Ultra-short laser pulse measuring device based on single two-step phase shift spectrum phase interference

Abstract

The invention provides an ultra-short laser pulse measuring device based on single two-step phase shift spectrum phase interference, and relates to the field of ultra-short laser pulse diagnos.The ultra-short laser pulse measuring device divides a laser pulse to be measured into a first laser beam and a second laser beam through a beam splitter I; a first laser beam sequentially passes through a half-wave plate, a chirped pulse generator, a beam splitter II and a delay regulator I to form two sub-chirped pulses with time delay; after the second laser beam passes through a delay compensator and a delay regulator II, the second laser beam and the two sub-chirped pulses are subjected to nonlinear sum frequency in a sum frequency device through a focuser, and two sum frequency pulses are generated; the two beams of sum frequency pulses are delayed by a delay regulator III, then are combined by a beam combiner and are simultaneously received by two spectrometers, and the spectrometers record two spectral interference patterns with complementary interference fringes to obtain two groups of complementary two-step phase shift spectral interference fringes. The direct current component can be directly eliminated through single measurement.

Description

Technical Field

[0001] The invention relates to the field of ultrashort laser pulse diagnosis, in particular to an ultrashort laser pulse measurement device of single two-step phase shift spectrum phase interference. Background Art

[0002] Accurately mastering the time-frequency characteristics of ultrashort laser pulses is of great significance to the development of ultrafast science and technology, such as stable pulse transmission and pulse shaping for material processing. Traditionally, the methods used to measure the phase characteristics of femtosecond laser pulses are mainly frequency resolved optical gating (FROG) and self-referenced spectral coherent electric field reconstruction (SPIDER).

[0003] The ultrashort pulse phase measurement device made according to the traditional SPIDER method uses the nonlinear sum-frequency interference of the pulse to be measured and the chirped pulse after time stretching to generate spectral side-cut interference, and then records the spectral interference ring to extract the phase information. However, in the phase extraction process, when the temporal shape of the femtosecond pulse to be measured is complex or the pulse width to be measured is wide enough, the time domain signal of the spectral interference ring will overlap the DC quantity without phase information and the AC quantity containing phase information, thereby reducing the accuracy of the spectral phase restoration algorithm and limiting the expansion of the measurement range and promotion and application of ultrashort pulse phase measurement devices. Summary of the invention

[0004] In view of this, the purpose of the present invention is to propose an ultrashort laser pulse measurement device of single two-step phase-shift spectral phase interferometry, so as to solve the problem that the existing two-step phase-shift SPIDER technology cannot measure in real time, expand the application scope of the two-step phase-shift SPIDER measurement device, and is particularly suitable for ultrafast laser pulses with low repetition rate and complex spectral shapes.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] Based on the above purpose, the present invention provides an ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry, comprising the following components:

[0007] Beam splitter I, used for dividing the laser pulse to be measured into a first laser beam and a second laser beam;

[0008] A half-wave plate, disposed in the optical path of the first laser beam, for adjusting the polarization of the first laser beam;

[0009] A chirped pulse generator, arranged after the half-wave plate, for generating a chirped pulse with a dispersion phase;

[0010] A delay compensator, arranged after the beam splitter I, for compensating the optical path or delay between the second laser beam and the chirped pulse;

[0011] A beam splitter II is arranged after the chirped pulse generator, and is used for further splitting the chirped pulse into a first sub-chirped pulse and a second sub-chirped pulse;

[0012] The delay regulator I is arranged after the beam splitter II and is used to adjust the optical path or time delay between the two sub-chirped pulses;

[0013] A delay regulator II, used for adjusting the optical path or time delay between the chirped pulse generated by the first laser beam and the second laser beam;

[0014] A focuser, used for focusing the two chirped pulses and the second laser beam;

[0015] A frequency summation device, used for generating two sum-frequency pulses in a nonlinear sum-frequency process;

[0016] Delay regulator III, used to adjust the optical path or time delay between two sum frequency pulses;

[0017] A beam combiner, used to combine two sum frequency pulses;

[0018] A focusing lens is used to focus the combined sum frequency pulse onto the spectrometer;

[0019] Two spectrometers of the same model are used to simultaneously record two sets of complementary two-step phase-shifted spectral interference fringes.

[0020] As a further solution of the present invention, the first laser beam passes through a half-wave plate, a chirped pulse generator, a delay adjuster II, a beam splitter II and a delay adjuster II in sequence to form two chirped pulses with a time delay; after the second laser beam passes through the delay compensator, it undergoes nonlinear frequency addition in a frequency adder together with the two chirped pulses mentioned above through a focuser to generate two frequency addition pulses; after the two frequency addition pulses generate a certain delay through the delay adjuster III, they are combined through a beam combiner and simultaneously received by two spectrometers of the same model, and the spectrometers record the spectral interference patterns with two complementary interference fringes to obtain two sets of complementary two-step phase-shifted spectral interference fringes.

[0021] As a further solution of the present invention, the chirped pulse generator may be a dispersion glass, a dispersion prism or a grating pair.

[0022] As a further solution of the present invention, the delay compensator is a group of two relatively parallel plane reflectors, and the reflective surface is coated with a 0° broadband high-reflection film.

[0023] As a further solution of the present invention, the beam splitter II is a non-polarizing beam splitter.

[0024] As a further solution of the present invention, the delay adjuster I is a right-angle reflector group composed of two isosceles right-angle prisms with perpendicular inclined surfaces, and the inclined surfaces of the isosceles right-angle prisms are plated with a 45° broadband high-reflection film.

[0025] As a further solution of the present invention, the delay adjuster is a right-angle reflector group composed of two isosceles right-angle prisms with vertical inclined surfaces pasted on an adjustable translation stage.

[0026] As a further solution of the present invention, the frequency summer is a type II phase-matched nonlinear frequency summer crystal.

[0027] As a further solution of the present invention, the frequency adder is a type II BBO crystal (barium borate crystal).

[0028] As a further solution of the present invention, the beam combiner is a non-polarization beam splitter.

[0029] As a further solution of the present invention, the spectrometer is used to synchronously record two sets of complementary two-step phase-shifted spectral interference fringes, thereby eliminating the DC component in real time.

[0030] As a further solution of the present invention, the time delay of the two chirped pulses is adjusted by a delay regulator, thereby changing the frequency shear of the sum frequency pulse. The interference fringes recorded when the frequency shear is zero can be used to calibrate the linear term.

[0031] Compared with the prior art, the ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry proposed in the present invention has the following beneficial effects:

[0032] 1. Since the traditional two-step phase-shift SPIDER uses a half-wave plate or a quarter-wave plate to rotate back and forth to introduce two-step phase-shift interference, the present invention uses two spectrometers of the same model to simultaneously record complementary two-step phase-shift spectral interference fringes, which can realize real-time measurement of low-repetition-rate femtosecond pulses with complex spectral shapes, thereby improving the real-time measurement capability.

[0033] 2. The present invention uses two spectrometers in the device to simultaneously receive complementary spectral interference patterns, which can directly eliminate the DC component after numerical processing, avoiding the influence of the temporal overlap of the DC component and the AC component on the measurement results, thereby improving the accuracy of ultrashort laser pulse measurement and achieving the elimination of the DC component.

[0034] 3. The two-step phase-shift spectral interference fringes recorded in the present invention can effectively improve the signal-to-noise ratio of the signal. Compared with the traditional method, it has a higher signal-to-noise ratio and is more conducive to accurately extracting and recovering the phase information of ultrashort laser pulses. By eliminating the DC component in real time and improving the signal-to-noise ratio, the device provides more accurate measurement data, thereby improving the measurement accuracy of the time and spectral characteristics of ultrafast laser pulses with complex spectral shapes.

[0035] 4. The present invention uses a delay regulator to adjust the time delay of two chirped pulses, change the frequency shear of the sum frequency pulse, and the interference fringes recorded when the frequency shear is zero can be used to calibrate the linear term. This function makes the device flexible and adjustable under different experimental conditions. The present invention is particularly suitable for measuring the time and spectral characteristics of ultrafast laser pulses with complex spectral shapes, and has broad application prospects, especially in the fields of femtosecond laser technology, atmospheric laser communication, ultrafast spectroscopy, etc.

[0036] In summary, the ultrashort laser pulse measurement device of single two-step phase-shift spectral phase interferometry provided in the embodiment of the present invention has high measurement accuracy, high signal-to-noise ratio, real-time performance and a more compact structure, which overcomes the shortcomings of traditional methods and provides a more excellent solution for the precise measurement of ultrafast laser pulses.

[0037] These and other aspects of the present invention will be more clearly understood in the following description of the embodiments. It should be understood that the above general description and the following detailed description are only exemplary and explanatory and cannot limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following is a brief introduction to the drawings required for use in the exemplary embodiments or related technical descriptions. The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0039] Figure 1 It is a structural schematic diagram of an ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry provided by an embodiment of the present invention.

[0040] Figure 2 It is a schematic diagram of the structure of a delay compensator in an ultrashort laser pulse measurement device provided in an embodiment of the present invention.

[0041] Figure 3 It is a schematic diagram of the structure of a delay regulator in an ultrashort laser pulse measurement device provided in an embodiment of the present invention.

[0042] Reference numerals:

[0043] 101-beam splitter I, 102-half-wave plate, 103-chirped pulse generator, 104-delay compensator, 105-beam splitter II, 106-delay regulator I, 107-delay regulator II, 108-focuser, 109-frequency converter, 110-delay regulator III, 111-beam combiner, 112-focusing lens, 113-two spectrometers. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0045] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are intended to distinguish two non-identical entities or non-identical parameters with the same name. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, other steps or units inherent to a process, method, system, product or device that includes a series of steps or units.

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0049] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0050] See also Figure 1As shown, an embodiment of the present invention provides an ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry, comprising a beam splitter I 101, a half-wave plate 102, a chirped pulse generator 103, a delay compensator 104, a beam splitter II 105, a delay regulator I 106, a delay regulator II 107, a focuser 108, a frequency summer 109, a delay regulator III 110, a beam combiner 111, a focusing lens 112 and two spectrometers 113; the beam splitter I 101 is used to measure the laser pulse The chirped pulse generator 103 is provided after the half-wave plate 102 and is used to generate a chirped pulse. The beam splitter II 105 is provided after the chirped pulse generator 103 and is used to further split the chirped pulse into a first sub-chirped pulse and a second sub-chirped pulse. The delay regulator I 106 is provided after the beam splitter II 105 and is used to adjust the delay between the two sub-chirped pulses. The delay compensator 104 is used to compensate for the optical path or time delay between the second laser beam and the chirped pulse generated by the first laser beam. The delay regulator II 107 is used to adjust the delay between the second laser beam and the two sub-chirped pulses. The focuser 108 is used to focus the two sub-chirp pulses and the second laser beam; the frequency summer 109 is used to generate two sum-frequency pulses in the nonlinear sum-frequency process; the delay regulator III 110 is arranged after the frequency summer 109, and is used to adjust the delay between the two sum-frequency pulses; the beam combiner 111 is used to combine the two sum-frequency pulses; the focusing lens 112 is used to focus the combined sum-frequency pulses onto the spectrometer 113. The present invention is provided with two spectrometers 113, which are used to simultaneously record two sets of complementary two-step phase-shifted spectral interference fringes.

[0051] After the laser pulse to be measured is divided into a first laser beam and a second laser beam by beam splitter I 101, the first laser beam passes through half-wave plate 102, chirped pulse generator 103, beam splitter II 105 and delay regulator I 106 in sequence to form two sub-chirped pulses with time delay; after the second laser beam passes through delay compensator 104 and delay regulator II 107, it undergoes nonlinear frequency addition in sum frequency device 109 together with the two sub-chirped pulses mentioned above through focuser 108 to generate two sum frequency pulses; the two sum frequency pulses are combined by beam combiner 111 and focused by focusing lens 112 and then received by two spectrometers 113 at the same time, and the spectrometer 113 records the spectral interference patterns with two complementary interference fringes to obtain two sets of complementary two-step phase shift spectral interference fringes, and the DC component is eliminated through numerical processing, and the phase of the ultrashort laser pulse is extracted and restored from the AC component.

[0052] In this embodiment, the beam splitter II 105 is a non-polarizing cubic prism.

[0053] Furthermore, the chirped pulse generator 103 may be a dispersion glass, a dispersion prism or a grating pair.

[0054] Furthermore, the frequency adder 109 may be a type II BBO crystal.

[0055] Furthermore, the beam combiner 111 may be a non-polarizing cubic prism.

[0056] In this embodiment, see Figure 1 and Figure 2 As shown, the delay compensator 104 is a set of two relatively parallel plane reflectors, and the reflective surface is plated with a 0° broadband high-reflection film. Figure 2 As shown, the delay compensator 104 can fold the optical path to compensate for the optical path and make the device structure more compact.

[0057] In this embodiment, see Figure 1 and Figure 3 As shown, the delay regulator I 106, the delay regulator II 107 and the delay regulator III 110 are a right-angle reflector group composed of two isosceles right-angle prisms with perpendicular inclined surfaces, and the inclined surfaces of the isosceles right-angle prisms are coated with a 45° broadband high-reflection film. Figure 3 As shown, delay adjuster I106, delay adjuster II107 and delay adjuster III110 are a right-angle reflector group composed of two isosceles right-angle prisms with vertical inclined surfaces pasted on an adjustable translation stage. The right-angle reflector group can move back and forth in the direction of the arrow to change the optical path and adjust the delay.

[0058] The ultrashort laser pulse measurement device of single two-step phase-shift spectral phase interferometry provided in the embodiment of the present invention adopts two spectrometers 113 to simultaneously record two sets of complementary two-step phase-shift spectral interference fringes, which can measure low-repetition-rate femtosecond pulses with complex spectral shapes in real time and directly eliminate the influence of DC components, and has a higher signal-to-noise ratio and more accurate phase recording capability.

[0059] The ultrashort laser pulse measurement device of single two-step phase shift spectral phase interference provided in the embodiment of the present invention adopts delay regulator Ⅰ106 to adjust the time delay of two chirped pulses to change the frequency shearing amount of the sum frequency pulse. The interference fringes recorded when the frequency shearing amount is zero can be used to calibrate the linear term.

[0060] In this embodiment, the spectrometer 113 is used to synchronously record two sets of complementary two-step phase-shifted spectral interference fringes, thereby eliminating the DC component in real time.

[0061] In summary, the present invention provides an ultrashort laser pulse measurement device of single two-step phase shift spectral phase interference, which can measure the phase characteristics of ultrashort laser pulses with high precision under real-time conditions. The present invention solves the problem of temporal overlap of DC component and AC component in traditional methods by using two spectrometers to simultaneously record complementary two-step phase shift spectral interference fringes, thereby improving the signal-to-noise ratio and measurement accuracy of the measurement system.

[0062] The ultrashort laser pulse measuring device of the present invention uses a delay regulator to adjust the time delay of two chirped pulses, thereby changing the frequency shear of the sum frequency pulse. The interference fringes recorded when the frequency shear is zero can be used to calibrate the linear term. Through the device, low repetition rate femtosecond pulses can be measured in real time and the influence of the DC component can be effectively eliminated.

[0063] The present invention uses a delay regulator I106 to adjust the time delay of two chirped pulses, change the frequency shear of the sum frequency pulse, and the interference fringes recorded when the frequency shear is zero can be used to calibrate the linear term. This function makes the device flexible and adjustable under different experimental conditions. The present invention is particularly suitable for measuring the time and spectral characteristics of ultrafast laser pulses with complex spectral shapes, and has a wide range of application prospects, especially in the fields of femtosecond laser technology, atmospheric laser communication, ultrafast spectroscopy, etc.

[0064] Therefore, the ultrashort laser pulse measurement device of single two-step phase-shift spectral phase interferometry provided in the embodiment of the present invention has high measurement accuracy, high signal-to-noise ratio, real-time performance and a more compact structure, and can be applied to low pulse repetition rate or single-run laser systems, providing a more excellent solution for the precise measurement of ultrafast laser pulses.

[0065] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0066] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. An ultrashort laser pulse measurement device based on single two-step phase shift spectral phase interferometry, characterized in that: Includes the following components: A beam splitter I (101), used for splitting a laser pulse to be measured into a first laser beam and a second laser beam; A half-wave plate (102) is arranged in the optical path of the first laser beam and is used to adjust the polarization direction of the first laser beam; A chirped pulse generator (103), arranged after the half-wave plate (102), is used to convert the first laser beam into a chirped pulse carrying a certain group dispersion phase; A delay compensator (104) for compensating for an optical path or time delay between the second laser beam and the chirped pulse generated by the first laser beam; A beam splitter II (105), arranged after the chirped pulse generator (103), for splitting the chirped pulse into a first sub-chirped pulse and a second sub-chirped pulse; A delay adjuster I (106), arranged after the beam splitter II (105), is used to adjust the optical path or time delay between the first sub-chirped pulse and the second sub-chirped pulse; A delay regulator II (107), used for changing the optical path or time delay between the second laser beam and the two sub-chirped pulses; A focuser (108) for focusing the second laser beam, the first sub-chirped pulse and the second sub-chirped pulse; A frequency summation device (109), used for generating two sum-frequency pulses in a nonlinear sum-frequency process; A delay regulator III (110), used for adjusting the optical path or time delay between the first sum frequency pulse and the second sum frequency pulse; A beam combiner (111), used for combining two sum frequency pulses; A focusing lens (112) is used to focus the combined sum frequency pulse onto the spectrometer (110); Two spectrometers (113) of the same model are used to simultaneously record two groups of two-step phase-shifted spectral interference fringes.

2. The ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry according to claim 1, characterized in that: The first laser beam passes through a half-wave plate (102), a chirped pulse generator (103), a beam splitter II (105) and a delay regulator I (106) in sequence to form two sub-chirped pulses with a time delay; After the second laser beam passes through the delay compensator (104) and the delay regulator II (107), it is subjected to nonlinear frequency addition in the frequency adder (109) together with the first sub-chirp pulse and the second sub-chirp pulse through the focuser (108) to generate two frequency addition pulses; The two sum frequency pulses are delayed by a delay adjuster III (110), combined by a beam combiner (111), and received by two spectrometers (113) at the same time after passing through a focusing lens (112). The spectrometers (113) record two complementary spectral interference patterns of interference fringes, thereby obtaining two sets of complementary two-step phase-shifted spectral interference fringes.

3. The ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry according to claim 1, characterized in that: The chirped pulse generator (103) is a dispersion glass, a dispersion prism or a grating pair.

4. The ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry according to claim 1, characterized in that: The beam splitter II (105) is a non-polarizing beam splitter.

5. The ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry according to claim 1, characterized in that: The frequency summer (109) is a type II phase-matched nonlinear frequency summer crystal.

6. The ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry according to claim 2, characterized in that: The beam combiner (111) is a non-polarization beam splitter.

7. The ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry according to claim 2, characterized in that: The spectrometer (113) is used to synchronously record two sets of complementary two-step phase-shifted spectral interference fringes and eliminate direct current components in real time.

8. The ultrashort laser pulse measurement device of single two-step phase shift spectral phase interferometry as claimed in claim 2, characterized in that: The delay regulator I (106) is used to adjust the time delay of the two chirped pulses and change the frequency shear of the sum frequency pulse. The interference fringes recorded when the frequency shear is zero can be used to calibrate the linear term.

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