Carrier envelope phase measuring device, stabilized light source, and carrier envelope phase measuring method

Abstract

This device for measuring carrier-envelope phase is provided with a first nonlinear optical crystal, a birefringent crystal, and a polarization plate. The first nonlinear optical crystal produces a first light which is a harmonic of incident light and has a different polarization direction from that of the incident light. The birefringent crystal is located ahead of the first nonlinear optical crystal in the travel direction of light, light traveling on the slow axis and on the fast axis having different travel speeds. The polarization plate is located ahead of the birefringent crystal in the travel direction of light, the transmission axis of the polarization plate being different from both the slow axis and the fast axis.

Description

[Technical Field]

[0001] The present invention relates to a carrier envelope phase measuring device, a stabilized light source, and a carrier envelope phase measuring method. [Background technology]

[0002] In very short laser pulses, there may be only a few light waves contained within a single pulse. The phase of the electric field oscillation (carrier) relative to the laser pulse envelope is called the carrier-envelope phase. The carrier-envelope phase is one of the important indices that characterize laser pulses, and also plays an important role in optical frequency combs, for example.

[0003] For example, Patent Document 1 describes that a stabilized optical frequency comb can be obtained by detecting the carrier envelope phase (CEO beat signal) by interfering harmonics of different orders and feeding the result back to a laser pulse light source.

[0004] Furthermore, for example, Patent Document 2 describes that by using a quasi-phase matching device, fundamental light and wavelength-converted light (harmonic) can be made to interfere with each other without considering the phase difference between them. The self-referencing interferometer described in Patent Document 2 can stabilize an optical frequency comb without being affected by frequency fluctuations of the interferometer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-135341 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-155984 Summary of the Invention [Problem to be solved by the invention]

[0006] The device described in Patent Document 1 splits harmonics of different orders using splitting means 6, 6a. The CEO beat signal is detected when the split harmonics of different orders interfere with each other in a balanced receiver 7. Each harmonic travels a different optical path between the splitting means 6, 6a and the balanced receiver 7. The carrier envelope phase drifts due to slight temperature fluctuations or mechanical vibrations in the optical system. When each harmonic travels a different optical path, the carrier envelope phase is more likely to drift due to slight misalignments in the optical system, etc.

[0007] Patent Document 1 also discloses a configuration that can reduce the optical path length difference. However, this configuration is only applicable under extremely limited conditions, such as when group velocity dispersion is nearly zero and there is almost no time difference between light of different wavelengths, limiting its versatility. Patent Document 1 also does not consider the phase difference that occurs between light of different wavelengths in the nonlinear optical crystal 11. Unless the thickness of the nonlinear optical crystal 11 is sufficiently thin, the phase difference that occurs between light of different wavelengths in the nonlinear optical crystal 11 cannot be ignored. When the thickness of the nonlinear optical crystal 11 is sufficiently thin, the harmonic generation efficiency is low, and harmonics cannot be generated unless extremely intense light is irradiated. In other words, the device described in Patent Document 1 cannot detect the carrier-envelope phase from weak light, limiting its versatility.

[0008] Furthermore, Patent Document 2 uses a special configuration called a quasi-phase matching device to generate light of different harmonics. Quasi-phase matching devices are expensive and have low versatility.

[0009] The present invention has been made in consideration of the above problems, and aims to provide a carrier envelope phase measurement device, a stabilized light source, and a carrier envelope phase measurement method that can stably measure the carrier envelope phase by suppressing the drift of the phase of light emitted from a light source that includes the carrier envelope phase. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides the following means.

[0011] (1) A carrier envelope phase measurement device according to a first aspect includes a first nonlinear optical crystal, a birefringent crystal, and a polarizing plate. The first nonlinear optical crystal generates a first light that is a harmonic of incident light and has a polarization direction different from that of the incident light. The birefringent crystal is located ahead of the light traveling direction of the first nonlinear optical crystal, and the light traveling at different speeds along its slow axis and fast axis. The polarizing plate is located ahead of the light traveling direction of the birefringent crystal, and the transmission axis of the polarizing plate is different from both the slow axis and the fast axis.

[0012] (2) The carrier envelope phase measurement device according to the above aspect may further include a second nonlinear optical crystal. The second nonlinear optical crystal is located between the first nonlinear optical crystal and the birefringent crystal in the light propagation direction. The second nonlinear optical crystal generates second light, which is a harmonic of the incident light and has a different order from the first light. The second light has a different polarization direction from the first light.

[0013] (3) The carrier envelope phase measurement device according to the above aspect may further include a nonlinear medium located in front of the first nonlinear optical crystal in the light propagation direction, and the nonlinear medium broadens the spectral band of the light incident on the nonlinear medium.

[0014] (4) The carrier envelope phase measurement device according to the above aspect may further include a laser light source that generates the incident light.

[0015] (5) A stabilized light source according to a second aspect includes a carrier envelope phase measurement device according to the above aspect, and a feedback circuit that feeds back the carrier envelope phase measured by the carrier envelope phase measurement device to the laser light source.

[0016] (6) A carrier envelope phase measurement method according to a third aspect includes the steps of: generating first and second lights having different polarization directions while passing through the same optical path; adjusting a phase difference between the first and second lights; and changing the polarization direction of at least one of the first and second lights to cause interference between the first and second lights. Each frequency of the first and second lights is an integer multiple of a fundamental frequency. [Effects of the Invention]

[0017] The carrier envelope phase measurement device, stabilized light source, and carrier envelope phase measurement method according to the above aspects can stably measure the carrier envelope phase by suppressing the drift of the phase of light emitted from the light source, which includes the carrier envelope phase. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram of a carrier envelope phase measurement device according to a first embodiment. [Figure 2] 1 is an example of a laser pulse output from a laser light source. [Figure 3] 3A and 3B are schematic diagrams for explaining the functions of the birefringent crystal and the polarizing plate of the carrier envelope phase measurement device according to the first embodiment. [Figure 4] FIG. 10 is a schematic diagram of a carrier envelope phase measurement device according to a second embodiment. [Figure 5] 10A and 10B are schematic diagrams for explaining the functions of a birefringent crystal and a polarizing plate of a carrier envelope phase measurement device according to a second embodiment. [Figure 6] FIG. 10 is a schematic diagram of a stabilized light source according to a third embodiment. [Figure 7] FIG. 1 is a schematic diagram of a carrier envelope phase measurement device of Comparative Example 1. [Figure 8] 1 shows the measurement results of Example 1 and Comparative Example 1. [Figure 9] 1 shows the measurement results of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present embodiment will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional proportions of each component may differ from the actual proportions. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications may be made within the scope of the present invention.

[0020] "First embodiment" 1 is a schematic diagram of a carrier envelope phase measurement device according to a first embodiment. The carrier envelope phase measurement device 100 includes a first nonlinear optical crystal 10, a second nonlinear optical crystal 20, a birefringent crystal 30, a polarizing plate 40, a laser light source 50, a nonlinear medium 60, a spectrometer 70, and a plurality of mirrors 90.

[0021] The first nonlinear optical crystal 10, the second nonlinear optical crystal 20, the birefringent crystal 30, the polarizing plate 40, the nonlinear medium 60, and the plurality of mirrors 90 are all on the same optical path between the laser light source 50 and the spectrometer 70. The mirrors 90 are installed at any desired locations and change the traveling direction of the light.

[0022] The laser light source 50 outputs, for example, laser pulses having a predetermined repetition frequency. For example, the laser light source 50 emits laser pulses with a frequency of 1.7 μm.

[0023] FIG. 2 shows an example of a laser pulse output from the laser light source 50. FIG. 2 shows the time waveform of the electric field of the laser pulse. The time waveform of the electric field is expressed as E(t)=E0(t)cos(ωt-φ CEP ) Carrier envelope phase φ CEP is the envelope E0(t) and carrier vibration cos(ωt-φ CEP ) is the relative phase with the carrier envelope phase φ CEP When the amplitude of the maximum electric field changes by half a period (π) of the light, the sign of the maximum electric field amplitude changes.

[0024] The nonlinear medium 60 is located ahead in the traveling direction of the light from the laser light source 50. The light from the laser light source 50 is incident on the nonlinear medium 60. The nonlinear medium 60 may be omitted.

[0025] The nonlinear medium 60 broadens the spectral band of the laser pulse. By broadening the spectral band of the laser pulse using the nonlinear medium 60, light of different wavelengths (e.g., second harmonic and third harmonic), which will be described later, becomes more likely to interfere with each other. The nonlinear medium 60 is, for example, a photonic crystal. Examples of photonic crystals include quartz photonic crystal fiber, illuminated photonic crystal fiber, and highly nonlinear fiber.

[0026] The first nonlinear optical crystal 10 is located in the direction of light propagation relative to the nonlinear medium 60. The first nonlinear optical crystal 10 generates a second-order nonlinear optical effect. The first nonlinear optical crystal 10 performs Type I phase matching. When an optical field of the same polarization acts twice on the first nonlinear optical crystal 10 in a second-order process, it generates light polarized perpendicular to the incident light. The type of nonlinear optical crystal can be adjusted by the angle between the incident light and the crystal axis.

[0027] The first nonlinear optical crystal 10 receives incident light L0 + The first light L1 - First light L1 - For example, the incident light L0 + The first light L1 - is the incident light L0 + The polarization direction of the first light L1 is different from that of the first light L2. - and the polarization direction of the incident light L0 + The polarization directions of the incident light L0 are, for example, orthogonal to each other. + Part of the first light L1 - The incident light L0 + and the first light L1 - have different polarization directions and therefore do not significantly affect each other.

[0028] The first nonlinear optical crystal 10 is, for example, β-BBO (β-barium borate), KDP (potassium dihydrogen phosphate), DKDP (potassium dihydrogen phosphate), LBO (lithium triborate), or CLBO (cesium lithium borate).

[0029] The thickness of the first nonlinear optical crystal 10 is, for example, 50 μm. When the first nonlinear optical crystal 10 has a necessary and sufficient thickness, it is possible to generate harmonics of sufficient intensity while ensuring a necessary spectral width.

[0030] The second nonlinear optical crystal 20 is located ahead of the first nonlinear optical crystal 10 in the light propagation direction. The second nonlinear optical crystal 20 is located between the first nonlinear optical crystal 10 and the birefringent crystal 30 in the light propagation direction. The second nonlinear optical crystal 20 generates a second-order nonlinear optical effect. The second nonlinear optical crystal 20 performs type II phase matching. When light of different polarizations is incident on the second nonlinear optical crystal 20, the second nonlinear optical crystal 20 matches the incident light L0 + produces light polarized parallel to the

[0031] The second nonlinear optical crystal 20 receives the incident light L0 + The second light L2 is a harmonic of + The second nonlinear optical crystal 20 generates the first light L1 - and incident light L0 + The second light L2 is generated by sum-and-concentration mixing with + The second light L2 + is the first light L1 - The second light L2 is a harmonic of a different order. + For example, the incident light L0 + The second light L2 + is the first light L1 - The polarization direction of the second light L2 is different from that of the first light L1. + and the polarization direction of the first light L1 - The polarization directions of the first light L1 and the second light L2 are, for example, orthogonal to each other. - Part of the second light L2 + The incident light L0 is output from the second nonlinear optical crystal 20. + A part of the first light L1 may be emitted.- and the second light L2 + have different polarization directions and therefore do not significantly affect each other.

[0032] The second nonlinear optical crystal 20 is, for example, β-BBO (β-barium borate), KDP (potassium dihydrogen phosphate), DKDP (potassium dihydrogen phosphate), LBO (lithium triborate), or CLBO (cesium lithium borate). The type of nonlinear optical crystal can be adjusted by the angle and cutting direction of the crystal.

[0033] The thickness of the second nonlinear optical crystal 20 is, for example, 3 mm or more. When the second nonlinear optical crystal 20 has a sufficient thickness, it is possible to generate harmonics with sufficient intensity.

[0034] The birefringent crystal 30 is located ahead of the first nonlinear optical crystal 10 and the second nonlinear optical crystal 20 in the light propagation direction. The birefringent crystal 30 is located between the second nonlinear optical crystal 20 and the polarizing plate 40 in the light propagation direction.

[0035] The refractive index of the birefringent crystal 30 varies depending on the vibration direction of the linearly polarized light. Therefore, the speed at which light travels varies between the slow axis and the fast axis of the birefringent crystal 30. The slow axis is the vibration direction in which light travels slowly (high refractive index), and the fast axis is the vibration direction in which light travels quickly (low refractive index).

[0036] The birefringent crystal 30 is, for example, α-BBO, magnesium fluoride (Mg2O), quartz, rutile, or yttrium orthovanadate (YVO4).

[0037] 3 is a schematic diagram for explaining the functions of the birefringent crystal 30 and the polarizing plate 40 of the carrier envelope phase measurement device according to the first embodiment. - and the second light L2 + The time difference Δt occurs between the first light L1 and the second light L2. - and the second light L2 +This time difference Δt occurs because the speed of light passing through first nonlinear optical crystal 10 and second nonlinear optical crystal 20 differs depending on the polarization direction of the light.

[0038] The birefringent crystal 30 adjusts this time difference Δt (phase difference). The birefringent crystal 30 reduces this time difference Δt (phase difference) to an appropriate value for obtaining interference. For example, the slow axis of the birefringent crystal 30 is aligned with the vibration direction of the light having a relatively fast traveling speed (for example, the vibration direction of the second light L2 + ), and the first axis is aligned with the vibration direction of the light with a relatively slow traveling speed (for example, the first light L1 - ), the time difference Δt becomes smaller.

[0039] The polarizing plate 40 is located ahead of the birefringent crystal 30 in the direction of light travel. A known polarizing plate can be used as the polarizing plate 40. The transmission axis of the polarizing plate 40 is different from and does not coincide with either the slow axis or the fast axis of the birefringent crystal 30. For example, the transmission axis of the polarizing plate 40 is tilted at 45° with respect to both the slow axis and the fast axis.

[0040] 1st light L1 - and second light L2 + The polarization direction of the first light L1 changes when it passes through the polarizing plate 40. - and the second light L2 + The polarization directions of the first light L1 - and the second light L2 + and interfere.

[0041] The spectrometer 70 receives the first light L1 - and the second light L2 + The interference light includes a carrier envelope phase. For example, the first light L1 - is the second harmonic, and the second light L2 + If is the third harmonic, the first light L1 - and the second light L2 + The following relation holds true for the interference intensity of the interference light with

[0042]

number

[0043] In the above equation, E 2f (ω) is the electric field spectrum obtained by Fourier transform of the time waveform of the electric field of the second harmonic, and E 3f (ω) is the electric field spectrum obtained by Fourier transform of the time waveform of the electric field of the third harmonic. I(ω) is the intensity of the interference light, I 2f (ω) is the intensity of the second harmonic, I 3f (ω) is the intensity of the third harmonic. Δt is the time difference between the second and third harmonics. φ 2f is the spectral phase obtained by Fourier transform of the second harmonic, and φ 3f is the spectral phase obtained by Fourier transforming the third harmonic. CEP is the carrier envelope phase.

[0044] The carrier envelope phase measurement device 100 can analyze the interference light and obtain the carrier envelope phase. - and the second light L2 + Because the two components pass through the same optical path, the interference conditions are less likely to fluctuate due to temperature fluctuations or mechanical vibrations. As a result, the phase drift of the light emitted from the light source, including the carrier-envelope phase, is suppressed, enabling stable measurement of the carrier-envelope phase.

[0045] "Second embodiment" 4 is a schematic diagram of a carrier envelope phase measurement device according to the second embodiment. Carrier envelope phase measurement device 101 differs from carrier envelope phase measurement device 101 according to the first embodiment in that it does not include second nonlinear optical crystal 20. Components similar to those in the first embodiment are given the same reference numerals and will not be described again.

[0046] The birefringent crystal 30 is located between the first nonlinear optical crystal 10 and the birefringent crystal 30. The birefringent crystal 30 receives incident light L0 + and the first light L1 - The first light L1 is emitted. - is the incident light L0+ and the polarization direction is different.

[0047] 5 is a schematic diagram for explaining the functions of the birefringent crystal 30 and the polarizing plate 40 of the carrier envelope phase measurement device according to the second embodiment. + is the incident light L0 + This differs from Figure 3 in that it is replaced with

[0048] When the incident light L0 reaches the birefringent crystal 30, + and the first light L1 - The time difference Δt' occurs between the incident light L0 + and the first light L1 - This time difference Δt′ occurs because the speed of light passing through first nonlinear optical crystal 10 differs depending on the polarization direction of the light.

[0049] The birefringent crystal 30 adjusts this time difference Δt′ (phase difference) by reducing the time difference Δt′ (phase difference) to an appropriate value for obtaining interference.

[0050] Incident light L0 + and the first light L1 - The polarization direction of the incident light L0 changes when it passes through the polarizing plate 40. + and the first light L1 - The polarization direction of the incident light L0 + and the first light L1 - These interference lights also contain the carrier envelope phase.

[0051] The carrier envelope phase measurement device 101 can analyze the interference light and determine the carrier envelope phase. + and the first light L1 - Because the two components pass through the same optical path, the interference conditions are less likely to fluctuate due to temperature fluctuations or mechanical vibrations. As a result, the phase drift of the light emitted from the light source, including the carrier-envelope phase, is suppressed, enabling stable measurement of the carrier-envelope phase.

[0052] "Third embodiment" 6 is a schematic diagram of a stabilized light source according to the third embodiment. The stabilized light source 102 according to the third embodiment includes a carrier envelope phase measurement device 100 and a feedback circuit 80. The stabilized light source 102 differs from the carrier envelope phase measurement device 100 in that it further includes a feedback circuit 80. The same components as those in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

[0053] The feedback circuit 80 receives carrier envelope phase information from the spectrometer 70 and feeds it back to the laser light source 50 .

[0054] The feedback circuit 80 includes, for example, a processor such as a CPU and a memory. The feedback circuit 80 operates when the processor executes a program. The processor instructs the operation of receiving carrier envelope phase information from the spectrometer 70 and the operation of adjusting the laser light source 50 based on the carrier envelope phase information. The memory stores data and programs about the carrier envelope phase. The feedback circuit 80 operates, for example, when the incident light L0 output from the laser light source 50 is adjusted. + Control the wavelength of the light.

[0055] As described above, the carrier envelope phase measurement devices according to the first and second embodiments can suppress the drift of the phase of light emitted from a light source including a carrier envelope phase due to temperature fluctuations or mechanical vibrations. However, it is difficult to completely prevent the phase of light emitted from a light source including a carrier envelope phase from drifting. For example, the phase of light emitted from a light source including a carrier envelope phase may drift due to unintended vibrations or the like. The stabilized light source 102 can stabilize the laser light by feeding back the carrier envelope phase result via the feedback circuit 80.

[0056] Up to this point, the first to third embodiments have been illustrated as examples of carrier envelope phase measurement devices and stabilized light sources. However, the present invention is not limited to these embodiments, and modifications are possible within the scope of the present invention.

[0057] For example, although the above examples show the case where there are one or two nonlinear optical crystals on the optical path, there may be three or more nonlinear optical crystals on the optical path. In this case, the two interfering lights will be higher-order harmonics. The frequencies of the two interfering lights need only be integer multiples of the fundamental frequency.

[0058] The carrier envelope phase measurement device and the stabilized light source may have a filter on the optical path. For example, the carrier envelope phase measurement device 100 according to the first embodiment may have a filter for the incident light L0 between the second nonlinear optical crystal 20 and the spectrometer 70. + The optical fiber 10 may have a filter for cutting out the above.

[0059] "Fourth embodiment" The carrier envelope phase measurement method according to the fourth embodiment includes a first step, a second step, and a third step.

[0060] The first step is to generate first and second lights having different polarization directions while passing through the same optical path. The frequencies of the first and second lights are integer multiples of the fundamental frequency. There is no particular limit to the method for generating the first and second lights. For example, harmonics can be generated by passing light through a nonlinear optical crystal. Alternatively, for example, a fourth harmonic, whose frequency is four times the fundamental frequency, may be generated by doubling a second harmonic, whose frequency is twice the fundamental frequency.

[0061] The second step is a step of adjusting the phase difference between the first light and the second light. If the time difference between the first light and the second light is too large, interference is difficult. In the second step, the phase difference between the first light and the second light is reduced, preferably to an appropriate value for achieving interference. There is no particular restriction on the method for adjusting the phase difference between these lights. For example, the phase difference between the first light and the second light can be adjusted by passing them through a birefringent crystal.

[0062] The third step is a step of changing the polarization direction of at least one of the first light and the second light to cause interference between the first light and the second light. There is no particular limitation on the means for changing the polarization direction of the light, and a polarizing plate, for example, can be used.

[0063] The interference light between the first light and the second light includes a carrier envelope phase. The carrier envelope phase measurement method according to the fourth embodiment can determine the carrier envelope phase by analyzing the interference light. Furthermore, since the first light and the second light are both generated along the same optical path, it is possible to suppress changes in the interference conditions due to temperature fluctuations or mechanical vibrations, or to suppress drift in the phase of the light emitted from the light source, which includes the carrier envelope phase. [Example]

[0064] Example 1 In Example 1, the carrier envelope phase was measured using the carrier envelope phase measurement device shown in FIG.

[0065] The laser pulse output from the laser light source 50 had a central wavelength of 1.7 μm and a pulse width of 6 femtoseconds. The first nonlinear optical crystal 10 was made of type I β-BBO with a thickness of 50 μm. The first nonlinear optical crystal 10 generates second harmonic waves. The second nonlinear optical crystal 20 was made of type II β-BBO with a thickness of 3 mm. The second nonlinear optical crystal 20 generates third harmonic waves.

[0066] The birefringent crystal 30 was made of α-BBO with a thickness of 1 mm. The slow axis of the birefringent crystal 30 was set to coincide with the vibration direction of the second harmonic wave. The fast axis of the birefringent crystal 30 was set to coincide with the vibration direction of the third harmonic wave.

[0067] The transmission axis of the polarizing plate 40 was tilted at 45° with respect to the slow axis and fast axis of the birefringent crystal 30 .

[0068] The spectrometer 70 then measured the interference light of the second and third harmonics, and measured the time change of the carrier envelope phase.

[0069] (Comparative Example 1) In Comparative Example 1, the carrier envelope phase was measured using the carrier envelope phase measurement device shown in FIG.

[0070] Comparative Example 1 differs only in the arrangement of each component, and the specific structure of each component is the same as that of Example 1. Furthermore, in Comparative Example 1, a portion of mirror 90 is replaced with a dichroic mirror 91. In Comparative Example 1 as well, the spectrometer 70 measures the interference light of the second harmonic and the third harmonic, and the time change of the carrier envelope phase is measured.

[0071] 8 and 9 show the measurement results of Example 1 and Comparative Example 1. The horizontal axis of FIG. 8 represents time, and the vertical axis represents the carrier envelope phase. The horizontal axis of FIG. 8 represents the carrier envelope phase, and the vertical axis represents the number of counts. FIG. 9 is a graph of the number of counts of the carrier envelope phase measured in FIG. 8.

[0072] As shown in FIG. 8, the carrier envelope phase of Comparative Example 1 fluctuates over time and is not stable. In contrast, the carrier envelope phase of Example 1 stabilizes near zero. Furthermore, as shown in FIG. 9, when checking the count number, the phase of the light emitted from the light source including the carrier envelope phase in Example 1 is constant and has a peak near zero, whereas the phase of the light emitted from the light source including the carrier envelope phase in Comparative Example 1 is unstable and the peak is broad. This is thought to be due to the fact that the configuration of Comparative Example 1 uses different optical paths for the second and third harmonic waves to propagate. In other words, by using the same optical path for the second and third harmonic waves to propagate, the phase of the light emitted from the light source including the carrier envelope phase is stabilized. [Explanation of symbols]

[0073] 10...first nonlinear optical crystal, 20...second nonlinear optical crystal, 30...birefringent crystal, 40...polarizer, 50...laser light source, 60...nonlinear medium, 70...spectrometer, 80...feedback circuit, 90...mirror, 91...dichroic mirror, 100, 101...carrier envelope phase measurement device, 102...stabilized light source, L0 + …Incoming light, L1 - …First light, L2 + …Second light

Claims

1. a first nonlinear optical crystal, a birefringent crystal, and a polarizer; the first nonlinear optical crystal generates a first light which is a harmonic of the incident light and has a polarization direction different from that of the incident light; the birefringent crystal is located ahead of the first nonlinear optical crystal in the direction of light propagation, and the light propagates at different speeds along the slow axis and the fast axis; A carrier envelope phase measurement device, wherein the polarizing plate is located ahead of the birefringent crystal in the direction of light propagation, and the transmission axis of the polarizing plate is different from both the slow axis and the fast axis.

2. Further comprising a second nonlinear optical crystal; the second nonlinear optical crystal is located between the first nonlinear optical crystal and the birefringent crystal in the light propagation direction; the second nonlinear optical crystal generates second light, which is a harmonic of the incident light having a different order from the first light; 2. The carrier envelope phase measurement device according to claim 1, wherein the second light has a polarization direction different from that of the first light.

3. Further comprising a nonlinear medium; the nonlinear medium is located in front of the first nonlinear optical crystal in the light propagation direction; 3. The carrier-envelope phase measuring device according to claim 1, wherein the nonlinear medium broadens the spectral band of light incident on the nonlinear medium.

4. 4. The carrier envelope phase measurement device according to claim 1, further comprising a laser light source that generates the incident light.

5. The carrier envelope phase measurement device according to claim 4; a feedback circuit that feeds back the carrier envelope phase measured by the carrier envelope phase measurement device to the laser light source.

6. generating first and second lights having different polarization directions while passing through the same optical path; adjusting a phase difference between the first light and the second light; changing the polarization direction of at least one of the first light and the second light, thereby causing the first light and the second light to interfere with each other; A carrier envelope phase measurement method, wherein the frequencies of the first light and the second light are integer multiples of a fundamental frequency.

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