Dispersion measurement device, pulse light source, dispersion measurement method, and dispersion compensation method

Abstract

This dispersion measurement device (1A) is provided with a pulse forming unit (3), a correlation optical system (4), a light detection unit (5), and a calculation unit (6). A pulse forming unit (3) forms an optical pulse train (Pb) including a plurality of optical pulses having a time difference from each other and having different central wavelengths from each other on the basis of a measured optical pulse (Pa) output from a pulsed laser light source (2). The correlation optical system (4) receives the optical pulse train (Pb) output from the pulse forming unit (3), and outputs correlation light (Pc) including cross-correlation or self-correlation of the optical pulse train (Pb). A light detection unit (5) detects the temporal waveform of the correlation light (Pc) output from the correlation optical system (4). The calculation unit (6) estimates the wavelength dispersion amount of the pulsed laser light source (2) on the basis of the characteristic amount of the time waveform of the correlated light (Pc). As a result, a dispersion measurement device, a pulse light source, a dispersion measurement method, and a dispersion compensation method are achieved, whereby wavelength dispersion can be measured with a simple configuration.

Description

[0001] This application is filed on March 27, 2020 、Application No. 202080026111.3 、The name of the invention is Dispersion Measurement Measurement device, pulse light source, dispersion measurement method and dispersion compensation method A divisional application for a patent application. Technical Field

[0002] The invention relates to a dispersion measuring device, a pulse light source, a dispersion measuring method and a dispersion compensation method. Background Art

[0003] Patent Document 1 and Non-Patent Document 1 disclose methods for measuring wavelength dispersion of laser pulses. The measurement methods described in these documents are called MIIPS (Multiphoton Intrapulse Interference Phase Scan). Fig.38 1 is a diagram schematically showing an example of the configuration of a measurement device based on MIIPS. The measurement device 100 includes a pulse light source 101 as a measurement object, a pulse control optical system (pulse shaper) 102 including a spatial light modulation element (SLM, etc.), an optical system 103 including an SHG crystal 103a, a spectrometer 104, and a computing unit 105.

[0004] First, a sinusoidal phase spectrum modulation is applied to the light pulse output from the pulse light source 101 in the pulse control optical system 102. Then, the light output from the pulse control optical system 102 is input to the SHG crystal 103a, and the second harmonic (SHG) corresponding to the modulation pattern is generated in the SHG crystal 103a. The SHG is input to the spectrometer 104, and the emission spectrum of the SHG is obtained in the spectrometer 104, and the calculation unit 105 analyzes the emission spectrum.

[0005] In such a structure, it is possible to obtain a light emission spectrum with the phase shift amount σ of the sinusoidal phase spectrum modulation pattern as a function, and calculate the wavelength dispersion amount based on the characteristic amount expressed in its two-dimensional data (MIIPS trace). In addition, by providing the inverse dispersion of the measured wavelength dispersion to the modulation pattern of the spatial light modulation element of the pulse control optical system 102, it is possible to perform dispersion compensation of the light pulse.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application No. 2006-502407

[0009] Non-patent literature

[0010] Non-patent document 1: Bingwei Xu et al., "Quantitative investigation of the multiphoton intrapulse interference phase scan method for simultaneous phase measurement and compensation of femtosecond laser pulses", Journal of the Optical Society of America B, Vol. 23, No. 4, pp. 750-759, 2006 Summary of the invention

[0011] Problems to be solved by the invention

[0012] exist Fig.38 In the measurement device 100 shown, dispersion is measured based on the change in the luminous spectrum corresponding to the phase shift amount of the sinusoidal phase modulation pattern. To this end, the luminous spectrum must be measured. Usually, in the measurement of the luminous spectrum, a combination of a spectroscopic element and a photodetector, or a photodetector (spectrometer) capable of detecting wavelength-intensity characteristics is required. Therefore, the optical system becomes complicated.

[0013] An object of the embodiments is to provide a dispersion measurement device, a pulse light source, a dispersion measurement method, and a dispersion compensation method capable of measuring wavelength dispersion with a simple structure.

[0014] Methods for solving problems

[0015] The embodiment is a dispersion measurement device. The dispersion measurement device includes: a pulse forming unit that forms an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a measurement object; a correlation optical system that receives the optical pulse train output from the pulse forming unit and outputs correlation light including cross-correlation or autocorrelation of the optical pulse train; a light detection unit that detects a time waveform of the correlation light; and a calculation unit that estimates a wavelength dispersion amount of the measurement object based on a feature amount of the time waveform.

[0016] The embodiment is a dispersion measurement device. The dispersion measurement device includes: a pulse forming unit that forms an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a light source; a correlation optical system that receives the optical pulse train output from the pulse forming unit and passes through a measurement object, and outputs correlation light including cross-correlation or autocorrelation of the optical pulse train; a light detection unit that detects a time waveform of the correlation light; and a calculation unit that estimates a wavelength dispersion amount of the measurement object based on a feature amount of the time waveform.

[0017] The embodiment is a pulse light source. The pulse light source includes: a dispersion measurement device having the above-described structure; and a pulse forming device that compensates for the wavelength dispersion amount obtained by the dispersion measurement device for an optical pulse input to or output from the measurement object.

[0018] The embodiment is a pulse light source. The pulse light source includes the dispersion measurement device having the above structure, wherein the spatial light modulator constitutes a part of a pulse forming device that compensates the wavelength dispersion amount obtained by the dispersion measurement device for an optical pulse input to or output from the measurement object.

[0019] The embodiment is a dispersion measurement method. The dispersion measurement method includes: a pulse forming step of forming an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a measurement object; a correlated light generating step of generating correlated light including cross-correlation or autocorrelation of the optical pulse train; a detection step of detecting a time waveform of the correlated light; and a calculation step of estimating a wavelength dispersion amount of the measurement object based on a feature amount of the time waveform.

[0020] The embodiment is a dispersion measurement method. The dispersion measurement method includes: a pulse forming step of forming an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a light source; a correlated light generating step of generating correlated light including cross-correlation or autocorrelation of the optical pulse train output from the pulse forming step and passing through a measurement object; a detection step of detecting a time waveform of the correlated light; and a calculation step of estimating a wavelength dispersion amount of the measurement object based on a feature amount of the time waveform.

[0021] The embodiment is a dispersion compensation method including: a step of estimating the chromatic dispersion amount of a measurement object using the dispersion measurement method of the above structure; and a step of performing pulse forming for compensating the chromatic dispersion amount on an optical pulse input to or output from the measurement object.

[0022] Effects of the Invention

[0023] According to the dispersion measurement device, the pulse light source, the dispersion measurement method, and the dispersion compensation method of the embodiment, it is possible to measure wavelength dispersion with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram schematically showing the structure of a dispersion measurement device according to one embodiment.

[0025] Figure 2 It is a diagram showing a configuration example of a pulse forming unit.

[0026] Figure 3It is a diagram showing the modulation surface of SLM.

[0027] Figure 4 (a) to (c) are diagrams showing examples of multi-pulses in which bandwidth control is performed.

[0028] Figure 5 (a) to (c) are diagrams showing examples of multi-pulses in which bandwidth control is not performed as comparative examples.

[0029] Figure 6 FIG. 1 is a diagram schematically showing a correlation optical system for generating correlation light Pc including autocorrelation of an optical pulse train Pb as a configuration example of the correlation optical system.

[0030] Figure 7 FIG. 1 is a diagram schematically showing a correlation optical system for generating correlation light Pc including cross-correlation of an optical pulse train Pb as another configuration example of the correlation optical system.

[0031] Figure 8 FIG. 2 is a diagram schematically showing a correlation optical system for generating correlation light Pc including cross-correlation of optical pulse trains Pb as another configuration example of the correlation optical system.

[0032] Fig. 9 is a diagram for conceptually explaining the characteristic amount of the correlation light Pc. Fig. 9 (a) shows an example of the time waveform of the correlation light Pc when the pulse laser light source does not have wavelength dispersion, and Fig. 9 (b) shows an example of the time waveform of the correlation light Pc when the pulse laser light source has wavelength dispersion.

[0033] Fig.10 This is a diagram schematically showing an example of the hardware configuration of the computing unit.

[0034] Fig.11 This is a flowchart showing a dispersion measurement method using a dispersion measurement device.

[0035] Fig.12 (a) is a diagram showing the spectral waveform of a single pulse light pulse Pa to be measured. Fig.12 (b) is a diagram showing the time intensity waveform of the measured light pulse Pa.

[0036] Fig.13 (a) is a diagram showing a spectral waveform of output light from a pulse forming unit when rectangular wave phase spectrum modulation is applied to the SLM. Fig.13 (b) is a diagram showing a temporal intensity waveform of output light from a pulse forming unit.

[0037] Fig.14This is a diagram showing the structure of a modulation pattern calculation device that calculates the modulation pattern of an SLM.

[0038] Fig.15 It is a block diagram showing the internal structure of the phase spectrum design unit and the intensity spectrum design unit.

[0039] Fig.16 This is a diagram showing the calculation flow of the phase spectrum based on the iterative Fourier transform method.

[0040] Fig.17 It is a diagram showing the calculation flow of the phase spectrum function in the phase spectrum design unit.

[0041] Fig.18 It is a diagram showing the calculation flow of spectrum intensity in the intensity spectrum design unit.

[0042] Fig.19 This is a diagram showing an example of a flow of generating a target spectrum diagram in a target generating unit.

[0043] Fig. 20 is the function A representing the calculated intensity spectrum IFTA A diagram showing an example of the flow of (ω).

[0044] Fig.21 (a) is the spectrum graph SG IFTA The graph of (ω,t), Fig.21 (b) is the spectrum graph SG IFTA Target SG0(ω,t) after the change of (ω,t).

[0045] Fig. 22 (a) is a graph showing a modulation pattern for generating a multi-pulse with bandwidth control, Fig. 22 (b) means through Fig. 22 (a) is a graph of the optical pulse train Pb generated by the modulation pattern.

[0046] Fig.23 It means according to Fig. 22 (a) Spectrum diagram of the optical pulse train Pb generated by the modulation pattern.

[0047] Fig.24 (a) is a graph showing a modulation pattern for generating a multi-pulse without bandwidth control, Fig.24 (b) means through Fig.24 (a) is a graph of the optical pulse train Pd generated by the modulation pattern.

[0048] Fig.25 It means according to Fig.24 (a) Spectrum diagram of the optical pulse train Pd generated by the modulation pattern.

[0049] Fig.26 (a) is a graph plotting the relationship between the average value of the peak time interval of optical pulse trains Pb having different central wavelengths and the secondary dispersion amount of the measured optical pulse Pa. Fig.26 (b) is a graph plotting the relationship between the average value of the peak time intervals of optical pulse trains Pd having mutually equal central wavelengths and the secondary dispersion amount of the measured optical pulse Pa.

[0050] Fig. 27 This is a graph plotting the relationship between the peak intensity of optical pulse trains Pb having different central wavelengths and the secondary dispersion amount of the optical pulse Pa to be measured.

[0051] Fig.28 This is a graph plotting the relationship between the full width at half maximum of optical pulse trains Pb having different central wavelengths and the secondary dispersion amount of the optical pulse Pa to be measured.

[0052] Fig.29 (a) is a graph plotting the relationship between the difference in peak time intervals of optical pulse trains Pb having different central wavelengths and the amount of third-order dispersion of the optical pulse Pa to be measured. Fig.29 (b) is a graph plotting the relationship between the difference in peak time intervals of optical pulse trains Pd having mutually equal central wavelengths and the third-order dispersion amount of the optical pulse Pa to be measured.

[0053] Fig.30 This is a graph plotting the relationship between the peak intensity of optical pulse trains Pb having different central wavelengths and the third-order dispersion amount of the optical pulse Pa to be measured.

[0054] Fig.31 This is a graph plotting the relationship between the full width at half maximum of optical pulse trains Pb having different central wavelengths and the third-order dispersion amount of the optical pulse Pa to be measured.

[0055] Fig.32 It is a diagram showing the structure of a pulse forming unit as a first modification.

[0056] Fig.33 It is a diagram showing the structure of the second modified example.

[0057] Fig.34 It is a diagram showing the structure of the third modified example.

[0058] Fig.35 It is a diagram showing the structure of a pulse light source as a fourth variation.

[0059] Fig.36 It is a flowchart showing the dispersion compensation method of the fourth variant.

[0060] Fig.37It is a diagram showing the structure of a pulse light source as a fifth variation.

[0061] Fig.38 This is a diagram schematically showing a configuration example of a measurement device using MIIPS.

[0062] Fig.39 (a) is a graph showing an example of a spectrum waveform for generating a multi-pulse with bandwidth control, and Fig.39 (b) indicates that Fig.39 (a) is a graph of the temporal waveform of the optical pulse train corresponding to the spectral waveform.

[0063] Fig.40 (a) is a graph showing another example of a spectrum waveform for generating a multi-pulse with bandwidth control, and Fig.40 (b) means Fig.40 (a) is a graph of the temporal waveform of the optical pulse train corresponding to the spectral waveform. DETAILED DESCRIPTION

[0064] Hereinafter, embodiments of a dispersion measurement device, a pulse light source, a dispersion measurement method, and a dispersion compensation method will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted. The present invention is not limited to these examples.

[0065] Figure 1 The dispersion measurement device 1A is a device for measuring the wavelength dispersion of a pulse laser light source 2 as a measurement object, and includes a pulse forming unit 3, a correlation optical system 4, a light detection unit 5, and a calculation unit 6.

[0066] The light input end 3a of the pulse forming unit 3 is optically coupled to the pulse laser light source 2 in space or via an optical waveguide path such as an optical fiber. The light input end 4a of the related optical system 4 is optically coupled to the light output end 3b of the pulse forming unit 3 in space or via an optical waveguide path such as an optical fiber. The light detection unit 5 is optically coupled to the light output end 4b of the related optical system 4 in space or via an optical waveguide path such as an optical fiber. The operation unit 6 is electrically connected to the pulse forming unit 3 and the light detection unit 5.

[0067] The pulse laser light source 2 as the measurement object outputs a coherent measured light pulse Pa. The pulse laser light source 2 is, for example, a femtosecond laser, and in one embodiment is a solid laser light source such as an LD direct excitation type Yb:YAG pulse laser. The measured light pulse Pa is an example of the first light pulse in the present embodiment, and its time waveform is, for example, a Gaussian function. The full width at half maximum (FWHM) of the measured light pulse Pa is, for example, in the range of 10 to 10000 fs, and is 100 fs in one example. The measured light pulse Pa is a light pulse with a certain degree of bandwidth, and contains multiple continuous wavelength components. In one embodiment, the bandwidth of the measured light pulse Pa is 10 nm, and the central wavelength of the measured light pulse Pa is 1030 nm.

[0068] The pulse forming unit 3 is a part that forms an optical pulse train Pb including a plurality of optical pulses (second optical pulses) from the measured optical pulse Pa. The optical pulse train Pb is a single pulse group generated by dividing the spectrum constituting the measured optical pulse Pa into a plurality of bands and using each band. In addition, there may be overlapping portions at the boundaries of the plurality of bands. In the following description, the optical pulse train Pb is sometimes referred to as a "multi-pulse with bandwidth control".

[0069] Figure 2 1 is a diagram showing an example of the configuration of the pulse forming unit 3. The pulse forming unit 3 includes a diffraction grating 12, a lens 13, a spatial light modulator (SLM) 14, a lens 15, and a diffraction grating 16. The diffraction grating 12 is a spectroscopic element in the present embodiment, and is optically coupled to the pulse laser light source 2. The SLM 14 is optically coupled to the diffraction grating 12 via the lens 13. The diffraction grating 12 spatially separates a plurality of wavelength components included in the measured light pulse Pa for each wavelength. In addition, as a spectroscopic element, other optical components such as a prism may be used instead of the diffraction grating 12.

[0070] The measured light pulse Pa is incident obliquely with respect to the diffraction grating 12 and is split into a plurality of wavelength components. The light P1 containing the plurality of wavelength components is focused by the lens 13 according to each wavelength component and is imaged on the modulation surface of the SLM 14. The lens 13 may be a convex lens composed of a light-transmitting component or a concave mirror having a concave light-reflecting surface.

[0071] In order to convert the measured optical pulse Pa into an optical pulse train Pb, the SLM 14 shifts the phases of the plurality of wavelength components output from the diffraction grating 12. Therefore, the SLM 14 outputs the phases of the plurality of wavelength components output from the diffraction grating 12 from the calculation unit 6 (see Figure 1) receives the control signal and simultaneously performs phase modulation and intensity modulation of the light P1. In addition, SLM14 may also perform only phase modulation or only intensity modulation. SLM14 is, for example, a phase modulation type. In one embodiment, SLM14 is an LCOS (Liquid crystal on silicon) type. In addition, although a transmissive SLM14 is shown in the figure, SLM14 may also be a reflective type.

[0072] Figure 3 1 is a diagram showing the modulation surface 17 of the SLM 14. Figure 3 As shown, on the modulation surface 17, a plurality of modulation areas 17a are arranged along a certain direction A, and each modulation area 17a extends in a direction B intersecting the direction A. The direction A is the spectral direction of the diffraction grating 12. The modulation surface 17 functions as a Fourier transform surface, and the corresponding wavelength components after spectral separation are incident on the plurality of modulation areas 17a respectively. In each modulation area 17a, the SLM 14 modulates the phase and intensity of each incident wavelength component independently from other wavelength components. In addition, the SLM 14 of this embodiment is a phase modulation type, so the intensity modulation is achieved by the phase pattern (phase image) presented on the modulation surface 17.

[0073] Each wavelength component of the modulated light P2 modulated by the SLM 14 is concentrated at a point on the diffraction grating 16 through the lens 15. At this time, the lens 15 functions as a focusing optical system for focusing the modulated light P2. The lens 15 can be a convex lens composed of a light-transmitting component, or a concave mirror with a concave light-reflecting surface. In addition, the diffraction grating 16 functions as a combining optical system for combining each wavelength component after modulation. That is, through these lenses 15 and the diffraction grating 16, the multiple wavelength components of the modulated light P2 are mutually focused and combined to form a multi-pulse (optical pulse train Pb) with bandwidth control.

[0074] Figure 4 2 is a diagram showing an example of a multi-pulse subjected to bandwidth control. In this example, an optical pulse train Pb consisting of three optical pulses Pb1 to Pb3 is shown. Figure 4 (a) is a spectrum diagram, where the horizontal axis represents time, the vertical axis represents wavelength, and the light intensity is represented by the shade of color. Figure 4 (b) shows the time waveform of the optical pulse train Pb. The time waveform of each of the optical pulses Pb1 to Pb3 is, for example, a Gaussian function.

[0075] like Figure 4 (a) and Figure 4As shown in (b), the peak values ​​of the three light pulses Pb1 to Pb3 are separated from each other in time, and the propagation moments of the three light pulses Pb1 to Pb3 are staggered. In other words, relative to one light pulse Pb1, another light pulse Pb2 has a time delay, and relative to the other light pulse Pb2, another light pulse Pb3 has a time delay. However, the lower hem portions of adjacent light pulses Pb1, Pb2 (or Pb2, Pb3) may overlap with each other. The time interval (peak interval) between adjacent light pulses Pb1, Pb2 (or Pb2, Pb3) is, for example, in the range of 10 to 10000 fs, and in one example is 2000 fs. In addition, the FWHM of each light pulse Pb1 to Pb3 is, for example, in the range of 10 to 5000 fs, and in one example is 300 fs.

[0076] Figure 4 (c) shows the spectrum of the three light pulses Pb1 to Pb3. Figure 4 As shown in (c), the spectrum of the synthesized three light pulses Pb1 to Pb3 has a single peak, but referring to Figure 4 In (a), the central wavelengths of the three light pulses Pb1 to Pb3 are offset from each other. Figure 4 The single peak shown in (c) roughly corresponds to the spectrum of the measured light pulse Pa.

[0077] The peak wavelength interval of adjacent light pulses Pb1, Pb2 (or Pb2, Pb3) is determined by the spectral bandwidth of the measured light pulse Pa, and is roughly within the range of 2 times the half-maximum full width. In one example, when the spectral bandwidth of the measured light pulse Pa is 10nm, the peak wavelength interval is 5nm. As a specific example, when the central wavelength of the measured light pulse Pa is 1030nm, the peak wavelengths of the three light pulses Pb1 to Pb3 can be 1025nm, 1030nm and 1035nm respectively.

[0078] Figure 5 1 is a diagram showing an example of a multi-pulse in which bandwidth control is not performed as a comparative example. In this example, an optical pulse train Pd consisting of three optical pulses Pd1 to Pd3 is shown. Figure 5 (a) and Figure 4 (a) is also a spectrum diagram, with the horizontal axis representing time and the vertical axis representing wavelength, and the light intensity is represented by the shade of color. Figure 5 (b) shows the time waveform of the optical pulse train Pd. Figure 5 (c) shows the spectrum of the three light pulses Pd1 to Pd3.

[0079] like Figure 5As shown in (a) to (c) of FIG. 1 , the peaks of the three optical pulses Pd1 to Pd3 are separated from each other in time, but the central wavelengths of the three optical pulses Pd1 to Pd3 are consistent with each other. The pulse forming unit 3 of this embodiment does not generate such an optical pulse train Pd, but generates Figure 4 The optical pulse trains Pb shown have different central wavelengths from each other.

[0080] Refer again Figure 1 The correlation optical system 4 receives the optical pulse train Pb output from the pulse forming unit 3, and outputs correlation light Pc including the cross-correlation or auto-correlation of the optical pulse train Pb. In the present embodiment, the correlation optical system 4 is configured to include a lens 41, an optical element 42, and a lens 43. The lens 41 is disposed on an optical path between the pulse forming unit 3 and the optical element 42, and focuses the optical pulse train Pb output from the pulse forming unit 3 on the optical element 42.

[0081] The optical element 42 is, for example, a light emitting body including at least one of a nonlinear optical crystal and a phosphor that generates a second harmonic (SHG). Examples of nonlinear optical crystals include KTP (KTiOPO4) crystals, LBO (LiB3O5) crystals, and BBO (β-BaB2O4) crystals. Examples of phosphors include coumarin, stilbene, and rhodamine. The optical element 42 inputs a light pulse train Pb and generates correlated light Pc including the mutual correlation or autocorrelation of the light pulse train Pb. The lens 43 parallelizes or focuses the correlated light Pc output from the optical element 42.

[0082] Here, a configuration example of the optical system 4 will be described in detail. Figure 6 FIG. 4 is a diagram schematically showing a correlation optical system 4A for generating correlation light Pc including the autocorrelation of the optical pulse train Pb as a configuration example of the correlation optical system 4. The correlation optical system 4A includes a beam splitter 44 as an optical branching component for branching the optical pulse train Pb into two branches. Figure 1 The pulse forming unit 3 shown is optically coupled to transmit a part of the optical pulse train Pb input from the pulse forming unit 3 and reflect the remaining part. The branching ratio of the beam splitter 44 is, for example, 1:1.

[0083] One optical pulse train Pba branched by the beam splitter 44 reaches the lens 41 through the optical path 4c including the plurality of reflectors 45. Another optical pulse train Pbb branched by the beam splitter 44 reaches the lens 41 through the optical path 4d including the plurality of reflectors 46. The optical length of the optical path 4c is different from the optical length of the optical path 4d. Therefore, the plurality of reflectors 45 and the plurality of reflectors 46 constitute a delay optical system that gives a time difference to one optical pulse train Pba and another optical pulse train Pbb branched in the beam splitter 44. Moreover, at least a part of the plurality of reflectors 46 is mounted on the moving stage 47, and the optical length of the optical path 4d is variable. Therefore, in this structure, the time difference between the optical pulse train Pba and the optical pulse train Pbb can be made variable.

[0084] In this example, the optical element 42 includes a nonlinear optical crystal. The lens 41 focuses the optical pulse trains Pba and Pbb respectively toward the optical element 42, and makes the optical axes of the optical pulse trains Pba and Pbb intersect each other at a predetermined angle in the optical element 42. Thus, in the optical element 42, which is a nonlinear optical crystal, a second harmonic is generated starting from the intersection of the optical pulse trains Pba and Pbb. The second harmonic is a correlated light Pc, which includes the autocorrelation of the optical pulse train Pb. The correlated light Pc is input to the light detection unit 5 after being parallelized or focused by the lens 43.

[0085] Figure 7 FIG. 4 is a diagram schematically showing a correlation optical system 4B for generating cross-correlation correlation light Pc including an optical pulse train Pb as another configuration example of the correlation optical system 4. In the correlation optical system 4B, the optical pulse train Pb reaches the lens 41 through an optical path 4e, and a reference optical pulse Pr as a single pulse reaches the lens 41 through an optical path 4f.

[0086] The optical path 4f includes a plurality of reflectors 48 and is bent into a U-shape. Moreover, at least a portion of the plurality of reflectors 48 is mounted on a moving stage 49, and the optical length of the optical path 4f is variable. Therefore, in this structure, the time difference (the time difference when arriving at the lens 41) between the optical pulse train Pb and the reference optical pulse Pr can be made variable.

[0087] In this example, the optical element 42 also includes a nonlinear optical crystal. The lens 41 focuses the optical pulse train Pb and the reference optical pulse Pr toward the optical element 42, and in the optical element 42, the optical axis of the optical pulse train Pb and the optical axis of the reference optical pulse Pr intersect each other at a predetermined angle. Thus, in the optical element 42, which is a nonlinear optical crystal, a second harmonic is generated starting from the intersection of the optical pulse train Pb and the reference optical pulse Pr. The second harmonic is a correlated light Pc, which includes the cross-correlation of the optical pulse train Pb. The correlated light Pc is input to the light detection unit 5 after being parallelized or focused by the lens 43.

[0088] Figure 8 FIG. 4 is a diagram schematically showing a correlation optical system 4C for generating cross-correlated correlation light Pc including a light pulse train Pb as another configuration example of the correlation optical system 4. In this example, the SLM 14 of the pulse forming unit 3 is a polarization-dependent spatial light modulator having a modulation effect in the first polarization direction. In contrast, the deflection plane of the measured light pulse Pa input to the pulse forming unit 3 is tilted relative to the polarization direction in which the SLM 14 has a modulation effect, and the measured light pulse Pa includes a polarization component in the first polarization direction (arrow Dp1 in the figure) and a polarization component in the second polarization direction orthogonal to the first polarization direction (symbol Dp2 in the figure). In addition, the polarization of the measured light pulse Pa may be not only the above-mentioned polarization (tilted linear polarized light) but also elliptically polarized light.

[0089] The polarization component of the first polarization direction in the measured light pulse Pa is modulated in the SLM 14 and output as the light pulse train Pb from the pulse forming unit 3. On the other hand, the polarization component of the second polarization direction in the measured light pulse Pa is not modulated in the SLM 14 but is directly output from the pulse forming unit 3. This unmodulated polarization component is provided to the correlation optical system 4 as a single pulse, i.e., a reference light pulse Pr, coaxially with the light pulse train Pb.

[0090] The correlation optical system 4 generates correlation light Pc including the cross-correlation of the optical pulse train Pb based on the optical pulse train Pb and the reference optical pulse Pr. In this configuration example, by delaying the optical pulse train Pb in the SLM 14 and making the delay time variable (arrow E in the figure), the time difference (time difference when arriving at the lens 41) between the optical pulse train Pb and the reference optical pulse Pr can be made variable, and the correlation light Pc including the cross-correlation of the optical pulse Pb can be appropriately generated in the correlation optical system 4.

[0091] Fig. 9 This is a diagram for conceptually explaining the characteristic amount of the correlation light Pc. Fig. 9 (a) shows an example of the time waveform of the correlation light Pc in the case where the pulse laser light source 2 has no chromatic dispersion (chromatic dispersion is zero). Fig. 9 (b) shows an example of the time waveform of the correlation light Pc in the case where the pulse laser light source 2 has wavelength dispersion (wavelength dispersion is not zero).

[0092] In addition, these examples show that the optical pulse train Pb input to the relevant optical system 4 includes Figure 4In this case, the correlation light Pc is composed of three light pulses Pc1 to Pc3 corresponding to the light pulses Pb1 to Pb3, respectively. Here, the peak intensities of the light pulses Pc1 to Pc3 are respectively PE1 to PE3, the full width at half maximum (FWHM) of the light pulses Pc1 to Pc3 are respectively W1 to W3, and the peak time interval (pulse interval) of the light pulses Pc1 and Pc2 is G 1,2 , the peak time interval of the optical pulses Pc2 and Pc3 is set to G 2,3 .

[0093] like Fig. 9 As shown in (a), when the pulse laser light source 2 does not have wavelength dispersion, the time waveform of the correlation light Pc is substantially the same as the time waveform of the optical pulse train Pb. In this example, the peak intensity PE2 is greater than PE1 and PE3, and PE1 is substantially equal to PE3. In addition, regarding the full width at half maximum, W1, W2, and W3 are substantially equal to each other. Regarding the peak time interval, G 1,2 With G 2,3 Roughly equal.

[0094] In contrast, Fig. 9 As shown in (b), when the pulse laser light source 2 has wavelength dispersion, the time waveform of the correlation light Pc greatly changes from the time waveform of the optical pulse train Pb. In this example, the peak intensities PE1 to PE3 of the optical pulses Pc1 to Pc3 are Fig. 9 The full width at half maximum W1 to W3 of the light pulses Pc1 to Pc3 is significantly lower than that of (a). Fig. 9 The peak time interval G 1,2 and Fig. 9 (a) is much longer than (a).

[0095] Thus, when the pulse laser light source 2 has wavelength dispersion, the characteristic quantities of the temporal waveform of the correlation light Pc (peak intensities PE1 to PE3, full width at half maximum W1 to W3, peak time interval G 1,2 , G 2,3 ) changes greatly compared to the case where the pulse laser light source 2 does not have wavelength dispersion. Then, the amount of change depends on the wavelength dispersion amount of the pulse laser light source 2. Therefore, by observing the change in the characteristic amount of the time waveform of the correlation light Pc, the wavelength dispersion amount of the pulse laser light source 2 can be easily known with high accuracy.

[0096] Refer again Figure 1The light detection unit 5 is a part that receives the correlation light Pc output from the correlation optical system 4 and detects the time waveform of the correlation light Pc. The light detection unit 5 is configured to include a light detector (photodetector) such as a photodiode. The light detection unit 5 detects the time waveform of the correlation light Pc by converting the intensity of the correlation light Pc into an electrical signal. The electrical signal as the detection result is provided to the operation unit 6.

[0097] The calculation unit 6 estimates the chromatic dispersion amount of the pulse laser light source 2 based on the characteristic amount of the time waveform of the correlation light Pc provided from the light detection unit 5. As described above, according to the knowledge of the present inventors, when the correlation light Pc including the cross-correlation or autocorrelation of the optical pulse train Pb is generated, various characteristic amounts (such as pulse interval, peak intensity, pulse width, etc.) in the time waveform of the correlation light Pc have a significant correlation with the chromatic dispersion amount of the measurement object. Therefore, the calculation unit 6 can estimate the chromatic dispersion amount of the pulse laser light source 2 as the measurement object with high accuracy by evaluating the characteristic amount of the time waveform of the correlation light Pc.

[0098] Fig.10 6 is a diagram schematically showing an example of the hardware configuration of the computing unit 6. Fig.10 As shown, the computing unit 6 can be physically constructed as a common computer including a processor (CPU) 61, main storage devices such as ROM 62 and RAM 63, input devices 64 such as keyboard, mouse and touch screen, output devices 65 such as display (including touch screen), communication modules 66 such as network cards for sending and receiving data with other devices, auxiliary storage devices 67 such as hard disks, etc.

[0099] The processor 61 of the computer can realize the functions of the above-mentioned operation unit 6 through the chromatic dispersion amount calculation program. In other words, the chromatic dispersion amount calculation program causes the processor 61 of the computer to operate as the operation unit 6. The chromatic dispersion amount calculation program is stored in a storage device (storage medium) inside or outside the computer such as an auxiliary storage device 67. The storage device may also be a non-transitory recording medium. Examples of the recording medium include recording media such as floppy disks, CDs, and DVDs, recording media such as ROMs, semiconductor memories, and cloud servers.

[0100] The auxiliary storage device 67 stores the characteristic amount of the time waveform of the correlation light Pc that is theoretically calculated in advance assuming that the wavelength dispersion of the pulse laser light source 2 is zero. If the characteristic amount is compared with the characteristic amount of the time waveform detected by the light detection unit 5, it can be known to what extent the characteristic amount of the correlation light Pc has changed due to the wavelength dispersion of the pulse laser light source 2. Therefore, the calculation unit 6 can compare the characteristic amount stored in the auxiliary storage device 67 with the characteristic amount of the time waveform detected by the light detection unit 5 to estimate the wavelength dispersion amount of the measurement object.

[0101] Fig.11 1 is a flow chart showing a dispersion measurement method using the dispersion measurement device 1A having the above structure. In this method, first, in the pulse forming step S1, design information required for forming the optical pulse train Pb is prepared. The design information is, for example, the peak time interval, peak intensity, half-maximum full width, number of pulses, bandwidth control amount, etc., assuming that the wavelength dispersion of the pulse laser light source 2 is zero.

[0102] Then, an optical pulse train Pb including a plurality of optical pulses Pb1 to Pb3 having time differences and different central wavelengths is formed based on the optical pulse Pa to be measured output from the pulse laser light source 2. For example, the plurality of wavelength components included in the optical pulse Pa to be measured are spatially separated for each wavelength, and the phases of the plurality of wavelength components are mutually shifted using the SLM 14, and then the plurality of wavelength components are focused. In this way, the optical pulse train Pb can be easily generated.

[0103] Next, in the correlation light generating step S2, the optical element 42 including at least one of a nonlinear optical crystal and a phosphor is used to generate the correlation light Pc including the cross-correlation or auto-correlation of the optical pulse train Pb. Figure 6 As shown, the optical pulse train Pb is branched into two branches, so that one of the branched optical pulse trains Pbb is time delayed relative to the other optical pulse train Pba, and the correlated light Pc containing the autocorrelation of the optical pulse train Pb is generated based on the time-delayed optical pulse train Pbb and the other optical pulse train Pba.

[0104] Next, after the time waveform of the correlation light Pc is detected in the detection step S3, the wavelength dispersion amount of the pulse laser light source 2 is estimated in the calculation step S4 based on the characteristic amount of the time waveform. For example, based on the peak intensity E1 to E3, the half-maximum full width W1 to W3, and the peak time interval G of the correlation light Pc, the wavelength dispersion amount of the pulse laser light source 2 is estimated in the calculation step S4. 1,2 , G 2,3 At least one of the above is used to estimate the wavelength dispersion amount of the pulse laser light source 2. In addition, the characteristic amount of the time waveform of the correlation light Pc theoretically calculated in advance assuming that the wavelength dispersion of the pulse laser light source 2 is zero is compared with the characteristic amount of the time waveform detected in the detection step S3 to estimate the wavelength dispersion amount of the pulse laser light source 2. In addition, as the characteristic amount of the time waveform of the correlation light Pc assuming that the wavelength dispersion of the pulse laser light source 2 is zero, the characteristic amount used in the design of the optical pulse train Pb may be directly used.

[0105] As reference Figure 8As described above, the SLM 14 may be a polarization-dependent SLM 14 having a modulation function in the first polarization direction. In this case, in the pulse forming step S1, a measured optical pulse Pa including both a component in the first polarization direction and a component in the second polarization direction orthogonal to the first polarization direction may be input, and the component in the first polarization direction of the measured optical pulse Pa may be modulated in the SLM 14 to form an optical pulse train Pb, and the component in the second polarization direction of the measured optical pulse Pa may not be modulated in the SLM 14 to form a reference optical pulse Pr. Then, in the correlation light generating step S2, correlation light Pc including a cross-correlation of the optical pulse train Pb may be generated based on the optical pulse train Pb having the first polarization direction and the reference optical pulse Pr having the second polarization direction.

[0106] Here, Figure 2 The phase modulation for generating the multi-pulse with bandwidth control in the SLM 14 of the pulse forming unit 3 shown in FIG. 1 is described in detail. The region in front of the lens 15 (spectral region) and the region in the back of the diffraction grating 16 (time domain) are in a Fourier transform relationship with each other, and the phase modulation in the spectral region affects the temporal intensity waveform in the time domain. Therefore, the output light from the pulse forming unit 3 can have various temporal intensity waveforms different from the measured light pulse Pa according to the modulation pattern of the SLM 14.

[0107] As an example, Fig.12 (a) shows the spectral waveform (spectral phase G11 and spectral intensity G12) of the single pulse light pulse Pa to be measured. Fig.12 (b) shows the time intensity waveform of the measured light pulse Pa. In addition, as an example, Fig.13 (a) shows the spectral waveform (spectral phase G21 and spectral intensity G22) of the output light from the pulse forming unit 3 when rectangular wave phase spectral modulation is applied to the SLM 14. Fig.13 (b) shows the time intensity waveform of the output light. Fig.12 (a) and Fig.13 In (a), the horizontal axis represents the wavelength (nm), the left vertical axis represents the intensity value of the intensity spectrum (arbitrary unit), and the right vertical axis represents the phase value of the phase spectrum (rad). Fig.12 (b) and Fig.13 In (b), the horizontal axis represents time (femtoseconds) and the vertical axis represents light intensity (arbitrary unit).

[0108] In this example, by providing a rectangular wave-shaped phase spectrum waveform to the output light, the single pulse of the measured light pulse Pa is converted into a double pulse accompanied by high-order light. Fig.13The illustrated spectrum and waveform are just examples, and the temporal intensity waveform of the output light from the pulse forming unit 3 can be shaped into various shapes by combining various phase spectra and intensity spectra.

[0109] Fig.14 1 is a diagram showing the structure of a modulation pattern calculation device 20 for calculating the modulation pattern of the SLM 14. The modulation pattern calculation device 20 is, for example, a personal computer; a smart device such as a smartphone or a tablet terminal; or a computer having a processor such as a cloud server. Figure 1 The calculation unit 6 shown may also serve as the modulation pattern calculation device 20 .

[0110] The modulation pattern calculation device 20 is electrically connected to the SLM 14, calculates a phase modulation pattern for making the temporal intensity waveform of the output light of the pulse forming unit 3 close to the desired waveform, and provides a control signal including the phase modulation pattern to the SLM 14. The modulation pattern is data for controlling the SLM 14, and is data including a table of the intensity of the complex amplitude distribution or the intensity of the phase distribution. The modulation pattern is, for example, a computer-generated hologram (CGH).

[0111] The modulation pattern calculation device 20 of this embodiment causes the SLM 14 to present a phase pattern including a phase pattern for phase modulation for giving the output light a phase spectrum with a desired waveform and a phase pattern for intensity modulation for giving the output light an intensity spectrum with a desired waveform. Fig.14 As shown, the modulation pattern calculation device 20 includes an arbitrary waveform input section 21 , a phase spectrum design section 22 , an intensity spectrum design section 23 , and a modulation pattern generation section 24 .

[0112] That is, the processor of the computer provided in the modulation pattern calculation device 20 realizes the functions of the arbitrary waveform input unit 21, the phase spectrum design unit 22, the intensity spectrum design unit 23, and the modulation pattern generation unit 24. Each function may be realized by the same processor or by different processors.

[0113] The processor of the computer can realize the above-mentioned functions through the modulation pattern calculation program. Therefore, the modulation pattern calculation program enables the processor of the computer to act as the arbitrary waveform input unit 21, the phase spectrum design unit 22, the intensity spectrum design unit 23 and the modulation pattern generation unit 24 in the modulation pattern calculation device 20. The modulation pattern calculation program is stored in a storage device (storage medium) inside or outside the computer. The storage device can also be a non-temporary recording medium. As the recording medium, a recording medium such as a floppy disk, a CD, a DVD, a recording medium such as a ROM, a semiconductor memory, a cloud server, etc. can be exemplified.

[0114] The arbitrary waveform input unit 21 receives input of a desired time intensity waveform from the operator. The operator inputs information about the desired time intensity waveform (e.g., pulse interval, pulse width, number of pulses, etc.) to the arbitrary waveform input unit 21. The information about the desired time intensity waveform is provided to the phase spectrum design unit 22 and the intensity spectrum design unit 23. The phase spectrum design unit 22 calculates a phase spectrum of the output light of the pulse forming unit 3 suitable for realizing the provided desired time intensity waveform. The intensity spectrum design unit 23 calculates an intensity spectrum of the output light of the pulse forming unit 3 suitable for realizing the provided desired time intensity waveform.

[0115] The modulation pattern generation unit 24 calculates a phase modulation pattern (for example, a computer generated hologram) for providing the phase spectrum obtained in the phase spectrum design unit 22 and the intensity spectrum obtained in the intensity spectrum design unit 23 to the output light of the pulse forming unit 3. Then, a control signal SC including the calculated phase modulation pattern is provided to the SLM 14. The SLM 14 is controlled based on the control signal SC.

[0116] Fig.15 2 is a block diagram showing the internal structure of the phase spectrum design unit 22 and the intensity spectrum design unit 23. Fig.15 As shown, the phase spectrum design unit 22 and the intensity spectrum design unit 23 have a Fourier transform unit 25, a function replacement unit 26, a waveform function correction unit 27, an inverse Fourier transform unit 28 and a target generation unit 29. The target generation unit 29 includes a Fourier transform unit 29a and a spectrum diagram correction unit 29b. The functions of these components will be described in detail later.

[0117] Here, the desired temporal intensity waveform is represented as a function in the time domain, and the phase spectrum is represented as a function in the frequency domain. Therefore, the phase spectrum corresponding to the desired temporal intensity waveform is obtained, for example, by iterative Fourier transform based on the desired temporal intensity waveform. Fig.16 This is a diagram showing the calculation flow of the phase spectrum based on the iterative Fourier transform method.

[0118] First, prepare the initial intensity spectrum function A0(ω) and phase spectrum function Ψ0(ω) as functions of frequency ω (processing number (1) in the figure). In one example, these intensity spectrum function A0(ω) and phase spectrum function Ψ0(ω) represent the spectral intensity and spectral phase of the input light, respectively. Next, prepare a spectrum containing the intensity spectrum function A0(ω) and the phase spectrum function Ψ0(ω). n (ω) is a waveform function (a) in the frequency domain (processing number (2) in the figure).

[0119] [Formula 1]

[0120]

[0121] The subscript n indicates the phase spectrum function Ψ0(ω) as the phase spectrum function Ψ before the first (first) Fourier transform. n (ω). i is an imaginary number.

[0122] Next, the above function (a) is Fourier transformed from the frequency domain to the time domain (arrow A1 in the figure). Thus, the time-intensity waveform function B is obtained. n (t) and the time phase waveform function Θ n (b) is the waveform function in the frequency domain of (t) (processing number (3) in the figure).

[0123] [Formula 2]

[0124]

[0125] Next, the time intensity waveform function B contained in the above function (b) is n (t) is replaced by the time intensity waveform function Target0(t) based on the desired waveform (processing numbers (4) and (5) in the figure).

[0126] [Formula 3]

[0127] b n (t):=Target0(t)…(c)

[0128] [Formula 4]

[0129]

[0130] Next, the above function (d) is subjected to an inverse Fourier transform from the time domain to the frequency domain (arrow A2 in the figure). Thus, the intensity spectrum function B is obtained. n (ω) and the waveform function (e) in the frequency domain of the phase spectrum function Ψn(ω) (processing number (6) in the figure).

[0131] [Formula 5]

[0132]

[0133] Next, in order to constrain the intensity spectrum function B contained in the above function (e) n (ω) is replaced by the initial intensity spectrum function A0(ω) (processing number (7) in the figure).

[0134] [Formula 6]

[0135] B n (ω): = A0(ω)…(f)

[0136] Afterwards, by repeatedly performing the above-mentioned processes (2) to (7) multiple times, the phase spectrum function Ψ in the waveform function can be made n The phase spectrum shape represented by (ω) is close to the phase spectrum shape corresponding to the expected time intensity waveform. The final phase spectrum function Ψ IFTA (ω) becomes the basis for the modulation pattern used to obtain the desired temporal intensity waveform.

[0137] However, in the above-mentioned iterative Fourier method, although the time intensity waveform can be controlled, there is a problem that the frequency components (band wavelengths) constituting the time intensity waveform cannot be controlled. Therefore, the modulation pattern calculation device 20 of this embodiment uses the calculation method described below to calculate the phase spectrum function and the intensity spectrum function that are the basis of the modulation pattern. Fig.17 2 is a diagram showing a calculation flow of the phase spectrum function in the phase spectrum design unit 22 .

[0138] First, prepare the initial intensity spectrum function A0(ω) and phase spectrum function Φ0(ω) as functions of frequency ω (processing number (1) in the figure). In one example, these intensity spectrum function A0(ω) and phase spectrum function Φ0(ω) respectively represent the spectral intensity and spectral phase of the input light. Next, prepare the first waveform function (g) in the frequency domain including the intensity spectrum function A0(ω) and the phase spectrum function Φ0(ω) (processing number (2-a)). Here, i is an imaginary number.

[0139] [Formula 7]

[0140]

[0141] Next, the Fourier transform unit 25 of the phase spectrum design unit 22 performs Fourier transform on the function (g) from the frequency domain to the time domain (arrow A3 in the figure). Thus, a second waveform function (h) in the time domain including the time intensity waveform function a0(t) and the time phase waveform function Φ0(t) is obtained (Fourier transform step, processing number (3)).

[0142] [Formula 8]

[0143]

[0144] Next, the function substitution unit 26 of the phase spectrum design unit 22 substitutes the time intensity waveform function Target0(t) based on the desired waveform input in the arbitrary waveform input unit 21 into the time intensity waveform function b0(t) as shown in the following equation (i) (processing number (4-a)).

[0145] [Formula 9]

[0146]

[0147] Next, the function replacement unit 26 of the phase spectrum design unit 22 replaces the time intensity waveform function a0(t) with the time intensity waveform function b0(t) as shown in the following equation (j). That is, the time intensity waveform function a0(t) included in the above function (h) is replaced with the time intensity waveform function Target0(t) based on the desired waveform (function replacement step, processing number (5)).

[0148] [Formula 10]

[0149]

[0150] Next, the waveform function correction unit 27 of the phase spectrum design unit 22 corrects the second waveform function so that the spectrum of the replaced second waveform function (j) is close to the target spectrum pre-generated according to the desired band. First, the second waveform function (j) is converted into a spectrum SG by performing time-frequency conversion on the replaced second waveform function (j). 0,k (ω, t) (processing number (5-a) in the figure). The subscript k indicates the k-th conversion processing.

[0151] Here, time-frequency conversion refers to the conversion of a composite signal such as a time waveform into three-dimensional information consisting of time, frequency, and intensity of signal components (spectral intensity) by frequency filtering or numerical calculation processing (multiplying by shifting a window function and deriving a spectrum for each time). In addition, in this embodiment, the conversion result (time, frequency, spectral intensity) is defined as a "spectrogram".

[0152] As time-frequency conversion, there are short-time Fourier transform (STFT), wavelet transform (Haar wavelet transform, Gabor wavelet transform, Mexican Hat wavelet transform, Morlet wavelet transform), and the like, for example.

[0153] In addition, the target spectrogram TargetSG0(ω, t) pre-generated according to the desired wavelength band is read from the target generation unit 29. The target spectrogram TargetSG0(ω, t) is substantially the same value as the target time waveform (time intensity waveform and the frequency components constituting it), and is generated in the target spectrogram function of the processing number (5-b).

[0154] Next, the waveform function correction unit 27 of the phase spectrum design unit 22 performs spectrum graph SG 0,k(ω, t) is matched with the pattern of the target spectrum graph TargetSG0(ω, t) to investigate the similarity (how consistent they are). In this embodiment, the evaluation value is calculated as an indicator of similarity. Then, in the next processing number (5-c), it is determined whether the obtained evaluation value meets the specified end condition. If the condition is met, the processing number (6) is entered; if the condition is not met, the processing number (5-d) is entered. In processing number (5-d), the time phase waveform function Φ0(t) contained in the second waveform function is changed to an arbitrary time phase waveform function Φ 0,k (t) The second waveform function after changing the time phase waveform function is converted into a spectrum again through time-frequency conversion such as STFT.

[0155] After that, the above-mentioned processing numbers (5-a) to (5-d) are repeated. In this way, the second waveform function is corrected so that the spectrum graph SG 0,k (ω, t) gradually approaches the target spectrum TargetSG0(ω, t) (waveform function correction step).

[0156] Thereafter, the inverse Fourier transform unit 28 of the phase spectrum design unit 22 performs inverse Fourier transform on the corrected second waveform function (arrow A4 in the figure) to generate a third waveform function (k) in the frequency domain (inverse Fourier transform step, processing number (6)).

[0157] [Formula 11]

[0158]

[0159] The phase spectrum function Φ included in the third waveform function (k) 0,k (ω) becomes the desired phase spectrum function Φ TWC-TFD (ω). The phase spectrum function Φ TWC-TFD (ω) is supplied to the modulation pattern generation unit 24 .

[0160] Fig.18 1 is a diagram showing the calculation flow of spectrum intensity in the intensity spectrum design unit 23. Processing number (1) to processing number (5-c) are the same as the calculation flow of spectrum phase in the above-mentioned phase spectrum design unit 22, and thus description thereof is omitted.

[0161] The waveform function correction unit 27 of the intensity spectrum design unit 23 displays the spectrum graph SG 0,k When the evaluation value of the similarity between (ω, t) and the target spectrum TargetSG0(ω, t) does not satisfy the specified termination condition, the time phase waveform function Φ0(t) contained in the second waveform function is constrained to the initial value, and the time intensity waveform function b0(t) is changed to an arbitrary time intensity waveform function b0,k (t) (Processing number (5-e)) The second waveform function after the time intensity waveform function is changed is converted into a spectrum diagram again by time-frequency conversion such as STFT.

[0162] Then, the processing numbers (5-a) to (5-c) are repeated. In this way, the second waveform function is corrected so that the spectrum graph SG 0,k (ω, t) gradually approaches the target spectrum TargetSG0(ω, t) (waveform function correction step).

[0163] Thereafter, the inverse Fourier transform unit 28 of the intensity spectrum design unit 23 performs inverse Fourier transform on the corrected second waveform function (arrow A4 in the figure) to generate a third waveform function (m) in the frequency domain (inverse Fourier transform step, processing number (6)).

[0164] [Formula 12]

[0165]

[0166] Next, in process number (7-b), the filter processing unit of the intensity spectrum design unit 23 processes the intensity spectrum function B included in the third waveform function (m). 0,k (ω) Perform filtering based on the intensity spectrum of the input light (filtering step). Specifically, the intensity spectrum function B 0,k In the intensity spectrum obtained by multiplying (ω) by the coefficient α, the portion exceeding the cutoff intensity of each wavelength determined based on the intensity spectrum of the input light is cut off. This is because the intensity spectrum function αB 0,k (ω) does not exceed the spectral intensity of the input light.

[0167] In one example, the cutoff intensity for each wavelength is set to be consistent with the intensity spectrum of the input light (in this embodiment, the initial intensity spectrum function A0(ω)). In this case, as shown in the following mathematical formula (n), in the intensity spectrum function αB 0,k (ω) is greater than the intensity spectrum function A0(ω), as the intensity spectrum function A TWC-TFD The value of (ω) is taken into the value of the intensity spectrum function A0(ω). 0,k (ω) is the intensity spectrum function A0(ω) and below, as the intensity spectrum function A TWC-TFD (ω) is taken into the intensity spectrum function αB 0,k The value of (ω) (processing number (7-b) in the figure).

[0168] [Formula 13]

[0169]

[0170] The intensity spectrum function A TWC-TFD (ω) is provided to the modulation pattern generation unit 24 as the desired spectrum intensity finally obtained.

[0171] The modulation pattern generation unit 24 calculates a phase spectrum function Φ calculated by the phase spectrum design unit 22. TWC-TFD The spectral phase represented by (ω) and the intensity spectrum function A calculated by the intensity spectrum design unit 23 TWC-TFD The spectral intensity represented by (ω) is provided to a phase modulation pattern (eg, a computer generated hologram) of the output light (data generation step).

[0172] Here, Fig.19 This is a diagram showing an example of the generation process of the target spectrum graph TargetSG0(ω, t) in the target generation unit 29. The target spectrum graph TargetSG0(ω, t) represents the target time waveform (the time intensity waveform and the frequency components (band components) constituting the time waveform), so the generation of the target spectrum graph is an extremely important process for controlling the frequency components (band components).

[0173] like Fig.19 As shown, the target generation unit 29 first inputs the spectral waveform (initial intensity spectrum function A0(ω) and initial phase spectrum function Φ0(ω)) and the desired time intensity waveform function Target0(t). In addition, the time function p0(t) containing the desired frequency (wavelength) bandwidth information is input (processing number (1)).

[0174] Next, the target generation unit 29 uses, for example, Fig.16 The iterative Fourier transform method shown in FIG. 1 calculates the phase spectrum function Φ used to realize the time intensity waveform function Target0(t) IFTA (ω)(Processing number (2)).

[0175] Next, the target generation unit 29 uses the phase spectrum function Φ obtained previously. IFTA (ω) is used to calculate the intensity spectrum function A used to realize the time intensity waveform function Target0(t) IFTA (ω)(Processing number (3)). Here, Fig. 20 is the function A representing the calculated intensity spectrum IFTA A diagram showing an example of the flow of (ω).

[0176] First, prepare the initial intensity spectrum function A k＝0 (ω) and phase spectrum function Ψ0(ω) (processing number (1) in the figure). Next, prepare k(ω) and the waveform function (o) in the frequency domain of the phase spectrum function Ψ0(ω) (processing number (2) in the figure).

[0177] [Formula 14]

[0178]

[0179] The subscript k indicates the kth Fourier transform process. Before the initial (first) Fourier transform process, the initial intensity spectrum function A is used. k = 0(ω) as the intensity spectrum function A k (ω). i is an imaginary number.

[0180] Next, the above function (o) is Fourier transformed from the frequency domain to the time domain (arrow A5 in the figure). Thus, the time intensity waveform function b is obtained. k (t) is the waveform function (p) in the frequency domain (processing number (3) in the figure).

[0181] [Formula 15]

[0182]

[0183] Next, the time intensity waveform function b contained in the above function (p) is k (t) is replaced by the time intensity waveform function Target0(t) based on the desired waveform (processing numbers (4) and (5) in the figure).

[0184] [Formula 16]

[0185] b k (t):=Target0(t)…(q)

[0186] [Formula 17]

[0187]

[0188] Next, the above function (r) is subjected to an inverse Fourier transform from the time domain to the frequency domain (arrow A6 in the figure). Thus, the intensity spectrum function C k (ω) and the phase spectrum function Ψ k (ω) is the waveform function (s) in the frequency domain (processing number (6) in the figure).

[0189] [Formula 18]

[0190]

[0191] Next, in order to constrain the phase spectrum function Ψ contained in the above function (s) k(ω) is replaced by the initial phase spectrum function Ψ0(ω) (processing number (7-a) in the figure).

[0192] [Formula 19]

[0193] Ψ k (ω):=Ψ0(ω)…(t)

[0194] In addition, the intensity spectrum function C in the frequency domain after inverse Fourier transformation k (ω) performs filtering based on the intensity spectrum of the input light. Specifically, the intensity spectrum function C k In the intensity spectrum indicated by (ω), a portion exceeding the cutoff intensity of each wavelength determined based on the intensity spectrum of the input light is cutoff.

[0195] In one example, the cut-off intensity of each wavelength is set to be consistent with the intensity spectrum of the input light (eg, the initial intensity spectrum function A k＝0 (ω)) is consistent. In this case, as shown in the following mathematical formula (u), in the intensity spectrum function C k (ω) Spectral intensity function A k＝0 (ω) large frequency, as the intensity spectrum function A k The value of (ω) is taken into the intensity spectrum function A k＝0 (ω) value. In addition, in the intensity spectrum function C k (ω) is the intensity spectrum function A k＝0 (ω) or less, as the intensity spectrum function A k (ω) is taken into the intensity spectrum function C k The value of (ω) (processing number (7-b) in the figure).

[0196] [Formula 20]

[0197]

[0198] The intensity spectrum function C contained in the above function (s) k (ω) is replaced by the intensity spectrum function A after filtering based on the above mathematical formula (u): k (ω).

[0199] Afterwards, by repeatedly performing the above-mentioned processes (2) to (7-b), the intensity spectrum function A in the waveform function can be made k The intensity spectrum shape represented by (ω) is close to the intensity spectrum shape corresponding to the expected time intensity waveform. Finally, the intensity spectrum function A is obtained. IFTA (ω).

[0200] Refer again Fig.19The phase spectrum function Φ in the processing numbers (2) and (3) described above is IFTA (ω) and the intensity spectrum function A IFTA By calculating (ω), a third waveform function (v) in the frequency domain including these functions is obtained (processing number (4)).

[0201] [Formula 21]

[0202]

[0203] The Fourier transform unit 29a of the target generation unit 29 performs Fourier transform on the above waveform function (v), thereby obtaining a fourth waveform function (w) in the time domain (processing number (5)).

[0204] [Formula 22]

[0205]

[0206] The spectrum graph correction unit 29b of the target generation unit 29 converts the fourth waveform function (w) into the spectrum graph SG IFTA (ω, t) (processing number (6)). Then, in processing number (7), the spectrum graph SG is corrected based on the time function p0(t) containing the desired frequency (wavelength) bandwidth information. IFTA (ω, t), thereby generating a target spectrum graph TargetSG0(ω, t). For example, a portion of the spectrum graph SG composed of two-dimensional data is cut out. IFTA The characteristic pattern that appears in (ω, t) is manipulated based on the time function p0(t) to manipulate the frequency component of that portion. A specific example will be described in detail below.

[0207] For example, consider the case where a triple pulse with a time interval of 2 picoseconds is set as the desired time intensity waveform function Target0(t). IFTA (ω,t) becomes Fig.21 The result shown in (a) is shown in Fig.21 In (a), the horizontal axis represents time (unit: femtoseconds) and the vertical axis represents wavelength (unit: nm). In addition, the value of the spectrum graph is represented by the brightness of the graph. The brighter the graph, the larger the value of the spectrum graph. IFTA In (ω, t), the triple pulse appears as domains D1, D2, and D3 separated on the time axis at intervals of 2 picoseconds. The center (peak) wavelength of domains D1, D2, and D3 is 800 nm.

[0208] If it is desired to control only the temporal intensity waveform of the output light (only to obtain triple pulses), it is not necessary to operate these domains D1, D2, and D3. However, if it is desired to control the frequency (wavelength) band of each pulse, it is necessary to operate these domains D1, D2, and D3. That is, Fig.21 As shown in (b), independently moving the domains D1, D2, and D3 in the direction along the wavelength axis (vertical axis) means changing the constituent frequencies (bands) of the pulses. Such changes in the constituent frequencies (bands) of the pulses are performed based on the time function p0(t).

[0209] For example, when the peak wavelength of domain D2 is fixed at 800 nm and the time function p0(t) is described in such a way that the peak wavelengths of domains D1 and D3 are parallel shifted by -2 nm and +2 nm respectively, the spectrum graph SG IFTA (ω,t) changes to Fig.21 Target spectrogram TargetSG0(ω,t) shown in (b) of FIG. 1 . For example, by performing such processing on the spectrogram, it is possible to generate a target spectrogram in which the constituent frequency (band) of each pulse is arbitrarily controlled without changing the shape of the temporal intensity waveform.

[0210] Effects obtained by the dispersion measurement apparatus 1A and the dispersion measurement method according to the present embodiment described above will be described.

[0211] In the dispersion measurement device 1A and the dispersion measurement method of the present embodiment, in the pulse forming unit 3 (pulse forming step S1), an optical pulse train Pb including a plurality of optical pulses Pb1 to Pb3 having time differences and different central wavelengths is generated based on the measured optical pulse Pa output from the pulse laser light source 2.

[0212] In such a case, for example, when a correlated light Pc including the cross-correlation or autocorrelation of the optical pulse train Pb is generated using a nonlinear optical crystal or the like, various characteristic quantities in the temporal waveform of the correlated light Pc (e.g., peak intensities PE1 to PE3, full width at half maximum W1 to W3, peak time interval G 1,2 , G 2,3 The wavelength dispersion amount of the pulsed laser light source 2 is significantly correlated with the wavelength dispersion amount of the pulsed laser light source 2. Therefore, according to this embodiment, the wavelength dispersion amount of the pulsed laser light source 2 can be estimated in the calculation unit 6 with high accuracy.

[0213] Furthermore, according to this embodiment, Fig.38Unlike the measurement device 100 shown, it is not necessary to measure the emission spectrum, so the optical system of the light detection unit 5 can be simplified, and the wavelength dispersion of the pulse laser light source 2 can be measured with a simple structure. In addition, the combination of a spectrometer and a photodetector commonly used in the measurement of the emission spectrum, or the photodetector capable of detecting the wavelength-intensity characteristic, is generally expensive, and according to the present embodiment, since it is not necessary, it can contribute to the cost reduction of the device.

[0214] As in the present embodiment, the calculation unit 6 (in the calculation step S4) may also calculate the peak time interval G of the optical pulse train Pb based on the peak time interval G of the optical pulse train Pb. 1,2 , G 2,3 The wavelength dispersion of the measured optical pulse Pa is obtained. As shown in the following embodiment, the present inventors have found that among various characteristic quantities in the time waveform, the peak time interval G 1,2 , G 2,3 The wavelength dispersion of the pulse laser light source 2 is significantly correlated. 1,2 , G 2,3 By estimating the chromatic dispersion amount of the measured optical pulse Pa, it is possible to estimate the chromatic dispersion amount of the pulse laser light source 2 with higher accuracy.

[0215] like Figure 2 As shown, the pulse forming unit 3 may also include: a diffraction grating 12 that spatially separates the multiple wavelength components included in the measured light pulse Pa for each wavelength; an SLM 14 that shifts the phases of the multiple wavelength components output from the diffraction grating 12; and a lens 15 that focuses the multiple wavelength components output from the SLM 14. Similarly, in the pulse forming step S1, the multiple wavelength components included in the measured light pulse Pa may be spatially separated for each wavelength, and the multiple wavelength components may be focused after the phases of the multiple wavelength components are shifted by using the SLM 14. In this case, it is possible to easily form an optical pulse train Pb including multiple optical pulses Pb1 to Pb3 that have time differences and different central wavelengths.

[0216] like Figure 8As shown, when the SLM 14 is a polarization-dependent SLM having a modulation function in the first polarization direction, the pulse forming unit 3 (in the pulse forming step S1) may input a measured light pulse Pa including a polarization component in the first polarization direction and a polarization component in the second polarization direction orthogonal to the first polarization direction. In this case, the polarization component in the first polarization direction of the measured light pulse Pa is modulated in the SLM 14 and output from the pulse forming unit 3 as an optical pulse train Pb. In addition, the polarization component in the second polarization direction of the measured light pulse Pa is not modulated in the SLM 14 and is output from the pulse forming unit 3. The correlation optical system 4 (in the correlation light generating step S2) can easily generate the correlation light Pc including the cross-correlation of the optical pulse train Pb based on these polarization components.

[0217] As in the present embodiment, the correlation optical system 4 may include at least one of a nonlinear optical crystal and a phosphor. Similarly, in the correlation light generating step S2, the correlation light Pc may be generated using at least one of a nonlinear optical crystal and a phosphor. In this case, the correlation light Pc including the cross-correlation or auto-correlation of the optical pulse train Pb can be easily generated.

[0218] like Figure 6 As shown, the dispersion measurement device 1A further includes: a beam splitter 44 that branches the optical pulse train Pb into two branches; and a delay optical system that gives a time difference to one optical pulse train Pbb and another optical pulse train Pba branched in the beam splitter 44, and the correlation optical system 4 can also generate correlation light Pc including autocorrelation based on the one optical pulse train Pbb and the other optical pulse train Pba after time delay. Similarly, in the correlation light generating step S2, the optical pulse train Pb can also be branched into two branches, so that one optical pulse train Pbb branched is time-delayed relative to the other optical pulse train Pba, and the correlation light Pc including the autocorrelation of the optical pulse train Pb can be generated based on the one optical pulse train Pbb and the other optical pulse train Pba after time delay. For example, by these devices and methods, it is possible to easily generate correlation light Pc including the autocorrelation of the optical pulse train Pb.

[0219] As in the present embodiment, the calculation unit 6 (in the calculation step S4) may compare the characteristic amount of the time waveform of the correlation light Pc calculated in advance assuming that the chromatic dispersion of the pulse laser light source 2 is zero with the characteristic amount of the time waveform of the correlation light Pc detected by the light detection unit 5, and obtain the chromatic dispersion amount of the measured light pulse Pa. In this case, the chromatic dispersion amount of the pulse laser light source 2 can be estimated with higher accuracy.

[0220] (Example)

[0221] As an example of the above embodiment, the inventors conducted a simulation based on numerical calculation. As the measured light pulse Pa, a single pulse with a bandwidth of 10nm and a central wavelength of 1030nm was assumed. In order to convert the measured light pulse Pa into Figure 4 The optical pulse train Pb of the three optical pulses Pb1 to Pb3 shown in FIG. 1 is calculated using the method described in the above embodiment to present a modulation pattern to the SLM 14. At this time, the peak time interval G 1,2 , G 2,3 Set it to 2000fs, and set the central wavelength to 1025nm, 1030nm and 1035nm respectively.

[0222] Fig. 22 (a) is a graph showing the calculated modulation pattern. In this figure, the horizontal axis represents the wavelength (unit: nm), the vertical axis on the left represents the light intensity (arbitrary unit), and the vertical axis on the right represents the phase (rad). In addition, the curve G31 in the figure represents the modulation pattern of the spectral phase, and the curve G32 in the figure represents the modulation pattern of the spectral intensity.

[0223] Fig. 22 (b) is a graph showing the time waveform of the optical pulse train Pb generated by the present simulation. Fig.23 This is the spectrum of the optical pulse train Pb generated by this simulation. Fig. 22 In (b), the horizontal axis represents time (unit: fs) and the vertical axis represents light intensity (arbitrary unit). Fig.23 In FIG. 1 , the horizontal axis represents time, the vertical axis represents wavelength, and light intensity is represented by color depth. As shown in these figures, an optical pulse train Pb including three optical pulses Pb1 to Pb3 having different central wavelengths and having time differences is obtained.

[0224] In addition, in this simulation, for comparison, in order to convert the measured light pulse Pa into Figure 5 The optical pulse train Pd of the three optical pulses Pd1 to Pd3 shown in the figure uses the method described in the above embodiment to calculate the modulation pattern presented to the SLM 14. These peak time intervals are set to be the same as those of the optical pulses Pb1 to Pb3, and the central wavelength of each optical pulse Pd1 to Pd3 is set to 1030nm.

[0225] Fig.24 (a) is a graph showing the calculated modulation pattern. A curve G41 in the graph shows the modulation pattern of the spectral phase, and a curve G42 in the graph shows the modulation pattern of the spectral intensity. Fig.24 (b) is a graph showing the time waveform of the optical pulse train Pd generated by the present simulation. Fig.25Spectra of the optical pulse train Pd generated by the present simulation are shown in FIG. As shown in these figures, an optical pulse train Pd including three optical pulses Pd1 to Pd3 having time differences and equal central wavelengths is obtained.

[0226] [Changes in characteristic quantities of a pulse train due to secondary dispersion]

[0227] In order to investigate the influence of the secondary dispersion of the pulse laser light source 2 on the characteristic amount of the pulse train, the secondary dispersion amount of the optical pulse Pa to be measured was changed, and the change in the time waveform of the optical pulse trains Pb and Pd was investigated. Fig.26 (a) and Fig.26 (b) is a graph showing the secondary dispersion of the measured optical pulse Pa and the peak time interval G. 1,2 , G 2,3 The average value (G 1,2 +G 2,3 ) / 2. Fig.26 (a) shows the case of an optical pulse train Pb whose central wavelength varies for each pulse. Fig.26 (b) shows the case of an optical pulse train Pd in ​​which the central wavelengths of the pulses are equal to each other. In these figures, the horizontal axis represents the secondary dispersion amount (unit: fs) of the measured optical pulse Pa. 2 ), the vertical axis represents the peak time interval G 1,2 , G 2,3 The average value (unit: fs).

[0228] Reference Fig.26 As can be seen from (a), in the case of an optical pulse train Pb whose central wavelength varies for each pulse, the peak time interval G increases with the increase or decrease of the secondary dispersion amount. 1,2 , G 2,3 The average value of increases and decreases monotonically (approximately linearly). If the data is examined in more detail, it is confirmed that the peak times of the left and right light pulses Pb1 and Pb3 tend to move symmetrically with respect to the peak time of the central light pulse Pb2 according to the dispersion amount. In this example, the peak time interval G 1,2 , G 2,3 An increase (or decrease) of 50 fs is equivalent to 5000 fs 2 The increase (or decrease) in the amount of secondary dispersion.

[0229] On the other hand, referring to Fig.26 As can be seen from (b), in the case of an optical pulse train Pd in ​​which the central wavelengths of the pulses are equal to each other, the peak time interval G is constant regardless of the increase or decrease in the secondary dispersion amount. 1,2 , G 2,3 The average value is approximately constant. It can be seen from this that the peak time interval G of the optical pulse train Pb is different for each pulse based on the central wavelength. 1,2, G 2,3 , the secondary dispersion amount of the pulse laser light source 2 can be easily and accurately estimated.

[0230] Fig. 27 This is a graph that plots the relationship between the secondary dispersion amount of the measured optical pulse Pa and the peak intensities E1 to E3, showing the case of an optical pulse train Pb with a different central wavelength for each pulse. The triangular plot points represent the peak intensity E1, the circular plot points represent the peak intensity E2, and the quadrilateral plot points represent the peak intensity E3. In this figure, the horizontal axis represents the secondary dispersion amount of the measured optical pulse Pa (unit: fs 2 ), the vertical axis represents the peak intensity (arbitrary unit).

[0231] Reference Fig. 27 It can be seen that in the optical pulse train Pb whose central wavelength is different for each pulse, the peak intensities E1 to E3 also increase or decrease as the amount of secondary dispersion increases or decreases. It can be seen that the amount of secondary dispersion of the pulsed laser light source 2 can be easily and accurately estimated based on the peak intensities E1 to E3 of the optical pulse train Pb whose central wavelength is different for each pulse.

[0232] Fig.28 This is a graph that plots the relationship between the secondary dispersion amount and the half-maximum full width W1 to W3 of the measured optical pulse Pa, and shows the case of an optical pulse train Pb whose central wavelength varies for each pulse. The triangular plot points represent the half-maximum full width W1, the circular plot points represent the half-maximum full width W2, and the quadrilateral plot points represent the half-maximum full width W3. In this figure, the horizontal axis represents the secondary dispersion amount (unit: fs) of the measured optical pulse Pa. 2 ), the vertical axis represents the full width at half maximum (unit: fs).

[0233] Reference Fig.28 It can be seen that in the optical pulse train Pb whose central wavelength is different for each pulse, as the amount of secondary dispersion increases or decreases, the half-maximum widths W1 to W3 also increase or decrease. It can be seen that based on the half-maximum widths W1 to W3 of the optical pulse train Pb whose central wavelength is different for each pulse, the amount of secondary dispersion of the pulsed laser light source 2 can be easily and accurately estimated.

[0234] [Changes in characteristic quantities of a pulse train due to third-order dispersion]

[0235] In order to investigate the influence of the third-order dispersion of the pulse laser light source 2 on the characteristic quantity of the pulse train, the third-order dispersion quantity of the optical pulse Pa to be measured is changed, and the change in the time waveform of the optical pulse trains Pb and Pd is investigated. Fig.29 (a) and Fig.29 (b) is a graph showing the third-order dispersion of the measured optical pulse Pa and the peak time interval G. 1,2 , G 2,3 The difference (G 1,2 -G2,3 ) / 2. Fig.29 (a) shows the case of an optical pulse train Pb whose central wavelength varies for each pulse. Fig.29 (b) shows the case of an optical pulse train Pd in ​​which the central wavelengths of the pulses are equal to each other. In these figures, the horizontal axis represents the third-order dispersion amount (unit: fs) of the measured optical pulse Pa. 3 ), the vertical axis represents the peak time interval G 1,2 , G 2,3 The difference (unit: fs).

[0236] Reference Fig.29 As can be seen from (a), in the case of an optical pulse train Pb whose central wavelength varies for each pulse, the peak time interval G increases as the amount of third-order dispersion increases or decreases. 1,2 , G 2,3 The difference increases and decreases monotonically. On the other hand, referring to Fig.29 As can be seen from (b), in the case of an optical pulse train Pd in ​​which the central wavelengths of the pulses are equal to each other, the peak time interval G is constant regardless of the increase or decrease of the amount of third-order dispersion. 1,2 , G 2,3 The difference is approximately constant. It can be seen from this that the peak time interval G of the optical pulse train Pb is different for each pulse based on the central wavelength. 1,2 , G 2,3 , the third-order dispersion amount of the pulse laser light source 2 can be easily and accurately estimated.

[0237] When the data is examined in more detail, it is confirmed that in the case of an optical pulse train Pb whose central wavelength differs for each pulse, the peak times of the left and right optical pulses Pb1 and Pb3 tend to shift asymmetrically with respect to the peak time of the central optical pulse Pb2 according to the dispersion amount. This characteristic is different from the case of the secondary dispersion amount, and based on this difference, i.e., the peak time interval G 1,2 , G 2,3 The relative change tendency of the dispersion order can be distinguished.

[0238] Fig.30 This is a graph that plots the relationship between the third-order dispersion amount of the measured optical pulse Pa and the peak intensities E1 to E3, and shows the case of an optical pulse train Pb whose central wavelength varies for each pulse. The triangular plot points represent the peak intensity E1, the circular plot points represent the peak intensity E2, and the quadrilateral plot points represent the peak intensity E3. In this figure, the horizontal axis represents the third-order dispersion amount of the measured optical pulse Pa (unit: fs 3 ), the vertical axis represents the peak intensity (arbitrary unit).

[0239] Reference Fig.30It can be seen that in the optical pulse train Pb whose central wavelength is different for each pulse, the peak intensities E1 to E3 also increase or decrease as the amount of third-order dispersion increases or decreases. It can be seen that based on the peak intensities E1 to E3 of the optical pulse train Pb whose central wavelength is different for each pulse, the third-order dispersion amount of the pulse laser light source 2 can be easily estimated with high accuracy.

[0240] Fig.31 This is a graph that plots the relationship between the third-order dispersion amount and the half-maximum full width W1 to W3 of the measured optical pulse Pa, and shows the case of an optical pulse train Pb whose central wavelength varies for each pulse. The triangular plot points represent the half-maximum full width W1, the circular plot points represent the half-maximum full width W2, and the quadrilateral plot points represent the half-maximum full width W3. In this figure, the horizontal axis represents the third-order dispersion amount (unit: fs) of the measured optical pulse Pa. 3 ), the vertical axis represents the full width at half maximum (unit: fs).

[0241] Reference Fig.31 It can be seen that in the optical pulse train Pb whose central wavelength is different for each pulse, as the amount of third-order dispersion increases or decreases, the half-maximum full width W1 to W3 also increases or decreases. It can be seen that based on the half-maximum full width W1 to W3 of the optical pulse train Pb whose central wavelength is different for each pulse, the third-order dispersion amount of the pulse laser light source 2 can be easily estimated with high accuracy.

[0242] (First Modification)

[0243] Fig.32 1 is a diagram showing the structure of a pulse forming unit 3A as a first modified example of the above-mentioned embodiment. The pulse forming unit 3A includes a pulse stretcher 18 and, in place of the SLM 14 (see Figure 2 ) and has a filter 19. The pulse stretcher 18 is provided on the optical path between the pulse laser light source 2 and the diffraction grating 12 to expand the pulse width of the measured light pulse Pa. Examples of the pulse stretcher 18 include a glass block, a diffraction grating pair, a prism pair, and the like.

[0244] The filter 19 is a light intensity filter, and is optically coupled to the diffraction grating 12 via the lens 13. The light P1 separated by the diffraction grating 12 is focused by the lens 13 according to each wavelength component and reaches the filter 19. The filter 19 has an optical opening corresponding to each wavelength component (or a filter with an absorptivity or reflectivity different from that of the surroundings), and selectively allows multiple wavelength components to pass from the wavelength band constituting the measured light pulse Pa. In addition, the propagation timings of these multiple wavelength components are shifted from each other by the pulse stretcher 18. Each wavelength component that has passed through the filter 19 is focused by the lens 15 to a point on the diffraction grating 16. Through these lenses 15 and the diffraction grating 16, the multiple wavelength components that have passed through the filter 19 are focused and combined with each other to become a multi-pulse (optical pulse train Pb) with bandwidth control.

[0245] The dispersion measurement apparatus 1A of the above-described embodiment may include a pulse forming unit 3A of the present modification instead of the pulse forming unit 3. In this case as well, the same effects as those of the above-described embodiment can be appropriately achieved.

[0246] (Second Modification)

[0247] Fig.33 : is a diagram showing the structure of the second variant of the above-mentioned embodiment. In this variant, the optical component 7 to be measured is arranged on the optical path between the pulse laser light source 2 and the pulse forming section 3, which is the front stage of the pulse forming section 3. In this case, the wavelength dispersion of the pulse laser light source 2 is zero or close to zero. Alternatively, if the wavelength dispersion of the pulse laser light source 2 is known, it may not be zero. In this variant, the light pulse output from the pulse laser light source 2 passes through the optical component 7 having wavelength dispersion and is input to the pulse forming section 3 as the measured light pulse Pa. In such a structure, the wavelength dispersion of the optical component 7 can be measured by a simple structure.

[0248] (Third Modification)

[0249] Fig.34 : is a diagram showing the structure of the third modified example of the above-mentioned embodiment. In this modified example, the optical component 7 to be measured is arranged in the optical path between the pulse forming unit 3 and the correlation optical system 4, which is the subsequent stage of the pulse forming unit 3. In this modified example, the optical pulse train Pb is output from the pulse forming unit 3 and passes through the optical component 7. Then, the correlation optical system 4 receives the optical pulse train Pb that has passed through the optical component 7, and outputs the correlation light Pc including the cross-correlation or auto-correlation of the optical pulse train Pb.

[0250] The dispersion measurement method of this modified example is as follows. First, Fig.11 In the pulse forming step S1 shown in FIG. 1 , the design information required for forming the optical pulse train Pb is prepared. Then, based on the optical pulse output from the pulse laser light source 2, an optical pulse train Pb including a plurality of optical pulses Pb1 to Pb3 having a time difference and different central wavelengths is formed. For example, Figure 2 As shown, the multiple wavelength components contained in the light pulse output from the pulse laser light source 2 are spatially separated for each wavelength, and the phases of the multiple wavelength components are mutually shifted using the SLM 14, and then the multiple wavelength components are focused. In this way, the optical pulse train Pb can be easily generated. After that, the optical pulse train Pb passes through the optical component 7 with wavelength dispersion.

[0251] Next, in the correlation light generating step S2, the optical element 42 including at least one of a nonlinear optical crystal and a phosphor is used to generate the correlation light Pc including the cross-correlation or auto-correlation of the optical pulse train Pb that has passed through the optical component 7. Figure 6 As shown, the optical pulse train Pb is branched into two branches, and one of the branched optical pulse trains Pbb is time-delayed relative to the other optical pulse train Pba, and the correlation light Pc including the autocorrelation of the optical pulse train Pb is generated based on the time-delayed optical pulse train Pbb and the other optical pulse train Pba. Thereafter, the detection step S3 and the calculation step S4 are the same as those in the above-mentioned embodiment.

[0252] In this modification, the optical pulse train Pb output from the pulse forming unit 3 is input to the correlation optical system 4 through the optical component 7 having wavelength dispersion. In such a configuration, the wavelength dispersion of the optical component 7 can be measured with a simple configuration. That is, the measurement object can be arranged in either the front stage or the rear stage of the pulse forming unit 3.

[0253] (Fourth Modification)

[0254] Fig.35 1 is a diagram showing the structure of a pulse light source 30A as a fourth variation of the above-mentioned embodiment. The pulse light source 30A includes a light source 31, a light branching component 32, a dispersion measurement device 1A, a pulse forming unit 33, and a focusing lens 34. The light source 31 includes, for example, the pulse laser light source 2 of the above-mentioned embodiment or the optical component 7 of the first variation. The light branching component 32 is optically coupled to the light source 31, receives the light pulse Pf from the light source 31, and branches the light pulse Pf. One of the branched light pulses Pfa is input to the pulse forming unit 3 of the dispersion measurement device 1A optically coupled to the light branching component 32. The other branched light pulse Pfb is input to the pulse forming unit 33 optically coupled to the light branching component 32.

[0255] The pulse forming unit 33 is a pulse forming device of this embodiment, which compensates for the wavelength dispersion (provides inverse dispersion) obtained by the dispersion measurement device 1A for the optical pulse Pfb output from the light source 31. Therefore, the pulse forming unit 33 includes an SLM 33a that performs phase modulation and has the same structure as the pulse forming unit 3 described above.

[0256] The SLM 33a is controlled by the operation unit 6 (or other computer) of the dispersion measurement device 1A. The data of the modulation pattern presented on the SLM 33a is generated by the operation unit 6 (or another computer). The SLM 33a is, for example, a phase modulation type. In one embodiment, the SLM 33a is an LCOS type. In addition, although a transmission type SLM 33a is shown in the figure, the SLM 33a may also be a reflection type. The dispersion-compensated light pulse Pfb output from the pulse forming unit 33 is focused by the focusing lens 34 and irradiated to the irradiated object 35.

[0257] Fig.36 1 is a flow chart showing the dispersion compensation method of this modification. First, a light pulse Pf is output from the light source 31, and the branched light pulse Pfa is input to the pulse forming unit 3 (step S11). Then, the wavelength dispersion amount of the light source 31 is estimated using the dispersion measurement device 1A (step S12). Next, the light pulse Pfb is phase modulated to compensate for the wavelength dispersion amount using the pulse forming unit 33 (step S13). The dispersion-compensated light pulse Pfb is irradiated to the irradiated object 35, for example, in laser processing, microscope observation, etc. (step S14).

[0258] According to the pulse light source 30A and the dispersion compensation method of this modification, since it includes the dispersion measurement device 1A (using the dispersion measurement method) of the above-mentioned embodiment, it is possible to measure and compensate for the wavelength dispersion with a simple structure. In addition, in this example, the pulse forming unit 33 performs phase modulation for compensating the wavelength dispersion amount on the optical pulse Pfb output from the light source 31 as the dispersion measurement object, but the present invention is not limited to this mode. For example, the pulse forming unit 33 may be arranged in the front stage of the dispersion measurement object, and the pulse forming unit 33 may perform phase modulation for compensating the wavelength dispersion amount on the optical pulse input to the dispersion measurement object.

[0259] (Fifth Modification)

[0260] Fig.37 FIG. 1 is a diagram showing the structure of a pulse light source 30B as a fifth variation of the above-mentioned embodiment. The pulse light source 30B includes a light source 31, a dispersion measurement device 1A, a light branching component 32, and a condenser lens 34. In this variation, the light branching component 32 is arranged on the optical path between the pulse forming unit 3 and the correlation optical system 4. Then, the SLM 14 (see Figure 2 ) After the wavelength dispersion amount is measured by the dispersion measurement device 1A, the light pulse Pf output from the light source 31 is further phase modulated for compensating the wavelength dispersion amount. In other words, the pulse forming unit 3 also has the function of the pulse forming unit 33 of the fourth modification, and the SLM 14 constitutes a part of the pulse forming unit for compensating the wavelength dispersion. In this case, as in the fourth modification, the wavelength dispersion can be measured and compensated with a simple structure.

[0261] In this example, the pulse forming unit 3 performs phase modulation for compensating the chromatic dispersion amount on the optical pulse Pf output from the light source 31 as the dispersion measurement object, but the present invention is not limited to this. For example, the pulse forming unit 3 may be arranged at the front stage of the dispersion measurement object, and the pulse forming unit 3 may perform phase modulation for compensating the chromatic dispersion amount on the optical pulse input to the dispersion measurement object.

[0262] The dispersion measurement device, the pulse light source, the dispersion measurement method, and the dispersion compensation method are not limited to the above-described embodiments and configuration examples, and various modifications are possible.

[0263] In the above embodiment, if Figure 2 In the figure, the method of forming the optical pulse train Pb using the diffraction grating 12 and the SLM 14 is exemplified. In the first modified example, the method of forming the optical pulse train Pb using the pulse stretcher 18 and the filter 19 is exemplified, but the method of forming the optical pulse train Pb in the pulse forming unit 3 and the pulse forming step S1 is not limited to this. For example, a variable mirror may be used instead of the SLM 14. Alternatively, a liquid crystal display capable of electronically controlling the phase, an acousto-optic modulator, etc. may be used instead of the SLM 14.

[0264] In the above embodiment, the method of generating the correlated light Pc using a nonlinear optical crystal or a fluorescent substance is exemplified, but the method of generating the correlated light Pc in the correlation optical system 4 and the correlated light generating step S2 is not limited thereto.

[0265] In addition, about Fig.14 The method for designing a spectrum waveform in the phase spectrum design unit 22 and the intensity spectrum design unit 23 of the modulation pattern calculation device 20 shown in the figure, and the method for generating a multi-pulse with bandwidth control thereby, are exemplified in the above-mentioned embodiment using Fig.15 The structure shown in the figure is to calculate the spectrum waveform by means of the Fourier transform unit 25, the function substitution unit 26, the waveform function correction unit 27, the inverse Fourier transform unit 28 and the target generation unit 29.

[0266] According to such a structure, the time waveform of the multi-pulses constituting the optical pulse train can be made close to a desired shape, and the frequency band components of each optical pulse included in the optical pulse train can be controlled with high precision. However, the method for generating multi-pulses with bandwidth control is not limited to such a method. For example, as described below, the spectral waveform (spectral modulation pattern) for generating multi-pulses can be obtained by a simpler method without using a complex optimization algorithm.

[0267] Specifically, as a method for generating a multi-pulse with bandwidth control, a method for combining a linear phase modulation pattern (linear phase pattern) based on information about the number of optical pulses in the multi-pulse to be generated, the frequency band components constituting each optical pulse, and the interval between optical pulses can be used. Fig.39 and Fig.40 This is a conceptual diagram for explaining such a method of generating multi-pulses.

[0268] Fig.39(a) is a graph showing an example of a spectral waveform for generating a bandwidth-controlled multi-pulse. In the graph, the horizontal axis represents the wavelength, the vertical axis on the left represents the light intensity, and the vertical axis on the right represents the phase. In addition, curve G51 in the figure represents the spectral phase, and curve G52 represents the spectral intensity. In addition, regions R1, R2, and R3 in the figure respectively represent wavelength regions set for the spectral intensity waveform of curve G52. In addition, in the spectral phase pattern of graph G51, phase pattern X1 represents the phase pattern in wavelength region R1, phase pattern X2 represents the phase pattern in wavelength region R2, and phase pattern X3 represents the phase pattern in wavelength region R3. These phase patterns X1, X2, and X3 are linear phase patterns with different slopes from each other.

[0269] Fig.39 (b) means Fig.39 A graph of the time waveform of an optical pulse train corresponding to the spectral waveform shown in (a). In this graph, the horizontal axis represents time and the vertical axis represents light intensity. In this method, in the time waveform of the optical pulse train, an optical pulse is generated according to the number of linear phase patterns with different slopes contained in the spectral phase. Fig.39 In the example shown, in the wavelength regions R1 , R2 , R3 , by providing the above-mentioned linear phase patterns X1 , X2 , X3 , a bandwidth-controlled multi-pulse consisting of three optical pulses Y1 , Y2 , Y3 is generated.

[0270] In such a method, the slope of the linear phase pattern Xi corresponds to the amount of movement in the time waveform of the corresponding light pulse Yi. In addition, the frequency band components constituting each light pulse Yi can be controlled by setting the division of the wavelength region Ri relative to the spectrum waveform. Fig.39 In the example shown, the optical pulse Y1 is generated based on the spectral intensity component of the wavelength region R1, the optical pulse Y2 is generated based on the spectral intensity component of the wavelength region R2, and the optical pulse Y3 is generated based on the spectral intensity component of the wavelength region R3.

[0271] In the above method, regarding the control of the spectral intensity component, for example, unnecessary intensity components may be filtered in advance (intensity cutoff based on intensity modulation). In addition, when the difference in the slopes of the phase patterns X1, X2, and X3 is small, there is a possibility that the light pulses are not sufficiently separated in the obtained time waveform, so it is preferable to set the phase pattern in consideration of such a point. In addition, the phase pattern in the spectral phase is Fig.39 The example shown is a continuous pattern, but a discontinuous pattern is also possible.

[0272] Fig.40(a) is a graph showing another example of a spectral waveform for generating a bandwidth-controlled multi-pulse. The curve G61 in the figure represents the spectral phase, and the curve G62 represents the spectral intensity. In addition, the regions R4, R5, and R6 in the figure respectively represent the wavelength regions set for the spectral intensity waveform of the graph G62. In addition, in the spectral phase pattern of the graph G61, the phase pattern X4 represents the phase pattern in the wavelength region R4, the phase pattern X5 represents the phase pattern in the wavelength region R5, and the phase pattern X6 represents the phase pattern in the wavelength region R6. These phase patterns X4, X5, and X6 are linear phase patterns with different slopes from each other, and the boundaries between the phase patterns X5 and X6 become discontinuous patterns.

[0273] Fig.40 (b) means Fig.40 (a) is a graph showing the time waveform of the optical pulse train corresponding to the spectral waveform. Fig.40 In the example shown, by setting the above-mentioned discontinuous phase pattern in the spectral phase, light pulse Y4 is generated based on the spectral intensity component of wavelength region R4, light pulse Y6 is generated based on the spectral intensity component of wavelength region R5, and light pulse Y5 is generated based on the spectral intensity component of wavelength region R6. In this way, by setting the phase pattern in the spectral phase, the frequency band components constituting each light pulse can be arbitrarily changed and set in the time waveform.

[0274] The dispersion measurement device of the above-mentioned embodiment comprises: a pulse forming unit which forms an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a measurement object; a correlation optical system which receives the optical pulse train output from the pulse forming unit and outputs correlation light including cross-correlation or autocorrelation of the optical pulse train; a light detection unit which detects a time waveform of the correlation light; and a calculation unit which estimates a wavelength dispersion amount of the measurement object based on a feature amount of the time waveform.

[0275] The dispersion measurement device of the above-mentioned embodiment is configured to include: a pulse forming unit, which forms an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a light source; a correlation optical system, which receives the optical pulse train output from the pulse forming unit and passes through the measurement object, and outputs correlation light including cross-correlation or autocorrelation of the optical pulse train; a light detection unit, which detects the time waveform of the correlation light; and a calculation unit, which estimates the wavelength dispersion amount of the measurement object based on the feature amount of the time waveform.

[0276] The dispersion measurement method of the above-mentioned embodiment is configured to include: a pulse forming step of forming an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a measurement object; a correlated light generating step of generating correlated light including cross-correlation or autocorrelation of the optical pulse train; a detection step of detecting a time waveform of the correlated light; and a calculation step of estimating a wavelength dispersion amount of the measurement object based on a feature amount of the time waveform.

[0277] The dispersion measurement method of the above-mentioned embodiment is configured to include: a pulse forming step of forming an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a light source; a correlated light generating step of generating correlated light including cross-correlation or autocorrelation of the optical pulse train output from the pulse forming step and passing through the measurement object; a detection step of detecting a time waveform of the correlated light; and a calculation step of estimating a wavelength dispersion amount of the measurement object based on a feature amount of the time waveform.

[0278] In these devices and methods, in a pulse forming unit (pulse forming step), an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths is generated from a first optical pulse. Then, the first optical pulse is output from a measurement object, or the optical pulse train passes through the measurement object.

[0279] In such a case, according to the knowledge of the present inventors, when a correlated light including a cross-correlation or autocorrelation of an optical pulse train is generated using a nonlinear optical crystal or the like, various characteristic quantities (such as pulse interval, peak intensity, pulse width, etc.) in the time waveform of the correlated light have a significant correlation with the chromatic dispersion amount of the measurement object. Therefore, according to the above-mentioned device and method, the chromatic dispersion amount of the measurement object can be estimated with high accuracy in the calculation unit (calculation step).

[0280] Moreover, according to the above-mentioned device and method, Fig.38 Unlike the measurement device 100 shown, there is no need to measure the emission spectrum, so the optical system of the light detection unit (detection step) can be simplified, and the wavelength dispersion of the measurement object can be measured with a simple structure.

[0281] In the above-mentioned measuring device, the calculation unit may estimate the chromatic dispersion of the measuring object based on the time intervals of the plurality of light pulses included in the correlated light. In the above-mentioned measuring method, the calculation step may estimate the chromatic dispersion of the measuring object based on the time intervals of the plurality of light pulses included in the correlated light.

[0282] The inventors have found that among various characteristic quantities in a time waveform, the pulse interval in particular has a significant correlation with the chromatic dispersion amount of the measurement object. Therefore, according to these devices and methods, the chromatic dispersion amount of the measurement object can be estimated with higher accuracy.

[0283] In the above-mentioned measuring device, the pulse forming unit may be configured to include: a spectroscopic element that spatially separates the plurality of wavelength components included in the first light pulse for each wavelength; a spatial light modulator that shifts the phases of the plurality of wavelength components output from the spectroscopic element; and a focusing optical system that focuses the plurality of wavelength components output from the spatial light modulator. In addition, in the above-mentioned measuring method, in the pulse forming step, the plurality of wavelength components included in the first light pulse are spatially separated for each wavelength, the plurality of wavelength components are shifted in phase by the spatial light modulator, and then the plurality of wavelength components are focused.

[0284] For example, these devices and methods can easily form an optical pulse train including a plurality of second optical pulses having a time difference and different central wavelengths from each other.

[0285] In the above-mentioned measuring device, it can also be configured that the spatial light modulator is a polarization-dependent spatial light modulator having a modulation effect in a first polarization direction, the pulse forming unit inputs a first light pulse including a component in the first polarization direction and a component in a second polarization direction orthogonal to the first polarization direction, the component in the first polarization direction of the first light pulse is modulated in the spatial light modulator and output from the pulse forming unit as an optical pulse train, the component in the second polarization direction of the first light pulse is not modulated in the spatial light modulator but output from the pulse forming unit, and the correlation optical system generates correlated light including mutual correlation of the optical pulse train based on the component in the first polarization direction and the component in the second polarization direction.

[0286] In addition, in the above-mentioned measurement method, it can also be configured that the spatial light modulator is a polarization-dependent spatial light modulator having a modulation effect in a first polarization direction, in the pulse forming step, a first light pulse including a component in a first polarization direction and a component in a second polarization direction orthogonal to the first polarization direction is input, the component in the first polarization direction of the first light pulse is modulated in the spatial light modulator to form an optical pulse train, the component in the second polarization direction of the first light pulse is not modulated in the spatial light modulator and is output, and in the correlated light generating step, correlated light including a mutual correlation of the optical pulse train is generated based on the component in the first polarization direction and the component in the second polarization direction.

[0287] For example, these devices and methods can easily generate correlated light including the mutual correlation of optical pulse trains.

[0288] In the above-mentioned measuring device, the correlation optical system may be configured to include at least one of a nonlinear optical crystal and a phosphor. In the above-mentioned measuring method, at least one of a nonlinear optical crystal and a phosphor may be used in the correlation light generating step.

[0289] For example, these devices and methods can easily generate correlated light including cross-correlation or autocorrelation of optical pulse trains.

[0290] The above-mentioned measuring device may also be configured to further include: an optical branching component that branches the optical pulse train into two branches; and a delay optical system that gives a time difference to one optical pulse train and another optical pulse train branched in the optical branching component, and the correlation optical system generates a correlation light including an autocorrelation based on the one optical pulse train and the other optical pulse train after the time delay. In addition, in the above-mentioned measuring method, it may also be configured that in the correlation light generating step, the optical pulse train is branched into two branches, one of the branched optical pulse trains is time-delayed relative to the other optical pulse train, and the correlation light including the autocorrelation of the optical pulse train is generated based on the one optical pulse train and the other optical pulse train after the time delay.

[0291] For example, such an apparatus and method can easily generate correlated light including the autocorrelation of an optical pulse train.

[0292] In the above-mentioned measuring device, the calculation unit may be configured to compare the characteristic amount of the time waveform calculated in advance assuming that the chromatic dispersion of the measuring object is zero with the characteristic amount of the time waveform detected by the light detection unit, thereby estimating the chromatic dispersion amount of the measuring object. In addition, in the above-mentioned measuring method, the calculation step may be configured to compare the characteristic amount of the time waveform calculated in advance assuming that the chromatic dispersion of the measuring object is zero with the characteristic amount of the time waveform detected in the detection step, thereby estimating the chromatic dispersion amount of the measuring object.

[0293] According to these devices and methods, the wavelength dispersion amount of the measurement object can be estimated with higher accuracy.

[0294] The pulse light source of the above embodiment comprises: the dispersion measurement device of the above structure; and a pulse forming device which compensates the wavelength dispersion amount obtained by the dispersion measurement device for the optical pulse input to or output from the measurement object.

[0295] The pulse light source of the above embodiment includes the dispersion measuring device of the above structure, and the spatial light modulator of the dispersion measuring device constitutes a part of the pulse forming device, which compensates the wavelength dispersion amount calculated by the dispersion measuring device for the optical pulse input to or output from the measurement object.

[0296] The dispersion compensation method of the above embodiment includes: a step of estimating the chromatic dispersion amount of the measurement object using the dispersion measurement method of the above structure; and a step of performing pulse forming for compensating the chromatic dispersion amount on an optical pulse input to or output from the measurement object.

[0297] In these pulse light sources and dispersion compensation methods, since they include the above-mentioned dispersion measurement device or dispersion measurement method, wavelength dispersion can be measured and compensated with a simple structure.

[0298] Industrial Applicability

[0299] The embodiment can be used as a dispersion measurement device, a pulse light source, a dispersion measurement method, and a dispersion compensation method capable of measuring wavelength dispersion with a simple structure.

[0300] Explanation of symbols

[0301] 1A...Dispersion Measurement Device

[0302] 2...Pulsed laser light source

[0303] 3. 3A……Pulse forming unit

[0304] 3a...Optical input terminal

[0305] 3b... Light output terminal

[0306] 4, 4A, 4B, 4C ... Related optical systems

[0307] 4a...Optical input terminal

[0308] 4b... Light output terminal

[0309] 4c~4f……Light path

[0310] 5... Light detection unit

[0311] 6……Calculation unit

[0312] 7...Optical components

[0313] 12...Diffraction grating

[0314] 13, 15... Lens

[0315] 14...Spatial Light Modulator (SLM)

[0316] 16...Diffraction grating

[0317] 17...Modulation surface

[0318] 17a...Modulation area

[0319] 18...Pulse stretcher

[0320] 19...Filter

[0321] 20......Modulation pattern calculation device

[0322] 21...Arbitrary waveform input section

[0323] 22……Phase Spectrum Design Department

[0324] 23...Intensity Spectrum Design Department

[0325] 24......Modulation pattern generation unit

[0326] 25……Fourier Transform Unit

[0327] 26... Function substitution part

[0328] 27... Waveform function correction unit

[0329] 28...Inverse Fourier Transform

[0330] 29...Target Generation Department

[0331] 29a...Fourier Transform Unit

[0332] 29b... Spectral Correction Unit

[0333] 30...Pulse light source

[0334] 31... Light Source

[0335] 32...Optical branching components

[0336] 33...Pulse forming unit

[0337] 34... Focusing lens

[0338] 41, 43... Lens

[0339] 42...Optical elements

[0340] 44...Beam splitter

[0341] 45, 46, 48...reflector

[0342] 47, 49... Mobile Station

[0343] 61...Processor

[0344] 64... Input device

[0345] 65... Output device

[0346] 66...Communication module

[0347] 67... Auxiliary storage device

[0348] 100……Measuring device

[0349] 101...Pulsed light source

[0350] 102...Pulse Control Optical System

[0351] 103...Optical system

[0352] 103a……SHG crystal

[0353] 104...Spectrum Splitter

[0354] 105……Calculation Department

[0355] Pa...Measured light pulse

[0356] Pb, Pd... optical pulse train

[0357] Pb1~Pb3, Pd1~Pd3...Light pulse

[0358] Pba, Pbb... optical pulse train

[0359] Pc... Related light

[0360] Pc1~Pc3...Light pulse

[0361] Pf... Light Pulse

[0362] Pr...Reference light pulse

[0363] SC...control signal.

Claims

1. A measuring device, characterized in that: have: a pulse forming unit that forms an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from a measurement object; a correlation optical system that receives the optical pulse train output from the pulse forming section and outputs correlation light including cross-correlation or auto-correlation of the optical pulse train; and A light detection unit detects a characteristic amount of the correlation light by converting the intensity of the correlation light into an electric signal.

2. A measuring device, characterized in that: have: a pulse forming unit that forms an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on the first optical pulse output from the light source; a correlation optical system that receives the optical pulse train output from the pulse forming unit and passes through a measurement object, and outputs correlation light including cross-correlation or auto-correlation of the optical pulse train; and A light detection unit detects a characteristic amount of the correlation light by converting the intensity of the correlation light into an electric signal.

3. The measuring device according to claim 1 or 2, characterized in that The pulse forming unit includes: a spectroscopic element that spatially separates the multiple wavelength components included in the first light pulse according to each wavelength; a spatial light modulator that shifts the phases of the multiple wavelength components output from the spectroscopic element; and a focusing optical system that focuses the multiple wavelength components output from the spatial light modulator.

4. The measuring device according to claim 3, characterized in that The spatial light modulator is a polarization-dependent spatial light modulator having a modulation effect in a first polarization direction. The pulse forming unit inputs the first light pulse including a component in the first polarization direction and a component in a second polarization direction orthogonal to the first polarization direction. The component in the first polarization direction in the first optical pulse is modulated in the spatial light modulator and output from the pulse forming unit as the optical pulse train. The component in the second polarization direction in the first light pulse is output from the pulse forming unit without being modulated in the spatial light modulator. The correlation optical system generates the correlation light including a mutual correlation of the optical pulse train based on the component in the first polarization direction and the component in the second polarization direction.

5. The measuring device according to any one of claims 1 to 4, characterized in that: The correlation optical system includes at least one of a nonlinear optical crystal and a phosphor.

6. The measuring device according to any one of claims 1 to 5, characterized in that Also available: an optical branching component that branches the optical pulse train into two branches; and a delay optical system that provides a time difference between one optical pulse train and another optical pulse train branched in the optical branching component, The correlation optical system generates the correlation light including autocorrelation based on the one optical pulse train and the other optical pulse train after time delay.

7. The measuring device according to any one of claims 1 to 6, characterized in that: A calculation unit is further provided for comparing the feature amount calculated in advance with the feature amount detected by the light detection unit.

8. A measurement method, characterized in that: include: a pulse forming step of forming an optical pulse train including a plurality of second optical pulses having time differences and different central wavelengths from each other based on a first optical pulse output from the measurement object; a correlated light generating step of generating correlated light including a cross-correlation or a self-correlation of the optical pulse train; and The detection step detects a characteristic amount of the correlation light by converting the intensity of the correlation light into an electric signal.

9. A measurement method, characterized in that: include: a pulse forming step of forming an optical pulse train including a plurality of second optical pulses having a time difference and different central wavelengths from each other based on the first optical pulse output from the light source; a correlated light generating step of generating correlated light including a cross-correlation or an autocorrelation of the optical pulse train output from the pulse forming step and then passing through the measurement object; and The detection step detects a characteristic amount of the correlation light by converting the intensity of the correlation light into an electric signal.

10. The measuring method according to claim 8 or 9, characterized in that: In the pulse forming step, a plurality of wavelength components included in the first light pulse are spatially separated for each wavelength, and after the phases of the plurality of wavelength components are shifted from each other using a spatial light modulator, the plurality of wavelength components are focused.

11. The measuring method according to claim 10, characterized in that: The spatial light modulator is a polarization-dependent spatial light modulator having a modulation effect in a first polarization direction. In the pulse forming step, the first light pulse including a component in the first polarization direction and a component in a second polarization direction orthogonal to the first polarization direction is input, the component in the first polarization direction of the first light pulse is modulated in the spatial light modulator to form the light pulse train, and the component in the second polarization direction of the first light pulse is not modulated in the spatial light modulator and is outputted, In the correlated light generating step, the correlated light including the mutual correlation of the optical pulse train is generated based on the component in the first polarization direction and the component in the second polarization direction.

12. The measuring method according to any one of claims 8 to 11, characterized in that: In the correlated light generating step, at least one of a nonlinear optical crystal and a phosphor is used.

13. The measuring method according to any one of claims 8 to 12, characterized in that: In the correlated light generating step, the optical pulse train is branched into two branches, one of the branched optical pulse trains is time delayed relative to the other optical pulse train, and the correlated light including the autocorrelation of the optical pulse train is generated based on the one optical pulse train and the other optical pulse train after the time delay.

14. The measuring method according to any one of claims 8 to 13, characterized in that: The method further includes a calculation step of comparing the feature amount calculated in advance with the feature amount detected in the detection step.

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