Supercontinuum generation system, apparatus and device

Abstract

The present disclosure relates to a supercontinuum generation system, device and equipment, the supercontinuum generation system comprising: a femtosecond pulse generation module and a spectrum expansion module. The input end of the femtosecond pulse generation module is used to receive a femtosecond seed pulse, and the femtosecond pulse generation module is used to perform time domain shaping, amplification or reduction and compression on the femtosecond seed pulse to generate a femtosecond pulse. The spectrum expansion module comprises a first optical fiber segment, a second optical fiber segment and a self-reference interference unit. The first optical fiber segment is used to perform high-order soliton self-compression on the femtosecond pulse. The second optical fiber segment is used to broaden the spectrum of the femtosecond pulse under near-zero dispersion conditions to generate a first supercontinuum by frequency doubling. The self-reference interference unit is used to align the first long wave and the first short wave of the first supercontinuum in the time domain. After the first short wave is coaxial with the first long wave after frequency doubling, the self-reference interference unit outputs a target supercontinuum. Thus, the present disclosure realizes that the output supercontinuum has high flatness and high coherence.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of lasers, and particularly relates to a supercontinuum generation system, device and equipment. BACKGROUND

[0002] When an ultrashort pulse laser propagates in a nonlinear medium, its spectrum will be significantly broadened under the influence of nonlinear effects and group velocity dispersion, thereby forming a supercontinuum spectrum with a super wideband spectrum structure. The supercontinuum spectrum with wideband, high coherence, low noise and long time stability is an important basic light source in the fields of modern spectroscopy, optical metrology and precise frequency measurement.

[0003] In the related art, the supercontinuum spectrum is usually generated by a soliton driving mechanism, but the supercontinuum spectrum generated by using the mechanism has an envelope uneven problem. In order to improve the flatness problem of the supercontinuum spectrum, some studies propose to generate the supercontinuum spectrum by combining an all-normal dispersion (ANDi) photonic crystal fiber with a high-energy ultrashort pulse. Although this method can obtain a smoother spectrum structure and lower phase noise, it requires extremely high peak power, resulting in high cost and large volume of the required laser system, which is difficult to adapt to the needs of integration or external deployment in the laboratory.

[0004] Therefore, how to design a supercontinuum light source with simple structure, flat spectrum and high coherence has become a technical problem to be solved by the person skilled in the art. SUMMARY

[0005] In order to solve the above technical problems or at least partially solve the above technical problems, the present disclosure provides a supercontinuum generation system, device and equipment, so as to realize that the output supercontinuum spectrum has high flatness and high coherence, and the structure of the supercontinuum generation system is simple.

[0006] The present disclosure provides a supercontinuum generation system, comprising: a femtosecond pulse generation module and a spectrum expansion module.

[0007] The input end of the femtosecond pulse generation module is used to receive a femtosecond seed pulse, and the femtosecond pulse generation module is used to perform time domain shaping, amplification or reduction and compression on the femtosecond seed pulse to generate a femtosecond pulse.

[0008] The spectrum expansion module comprises a first optical fiber segment, a second optical fiber segment and a self-referenced interference unit; the first optical fiber segment is connected with the output end of the femtosecond pulse generation module, the first optical fiber segment is fusion spliced with the second optical fiber segment, and the second optical fiber segment is connected with the self-referenced interference unit; wherein the first optical fiber segment is used for self-compression of the femtosecond pulse to high-order solitons; the second optical fiber segment is used for spectrum expansion of the femtosecond pulse under near-zero dispersion condition to generate a first supercontinuum spectrum by frequency doubling; the self-referenced interference unit is used for time-domain alignment of a first long wave and a first short wave of the first supercontinuum spectrum, and the self-referenced interference unit is also used for output of a target supercontinuum spectrum after coaxial combination of the first short wave and the first long wave after frequency doubling.

[0009] Optionally, the length of the second optical fiber segment is greater than the length of the first optical fiber segment; wherein the first optical fiber segment and the second optical fiber segment are both nonlinear optical fibers, and the dispersion parameters of the first optical fiber segment and the second optical fiber segment are different.

[0010] Optionally, the self-referenced interference unit comprises a frequency doubling crystal, a first lens and a second lens.

[0011] The supercontinuum spectrum generation system further comprises a third optical fiber segment and an optical fiber beam splitter.

[0012] The third optical fiber segment is fusion spliced with the second optical fiber segment, the third optical fiber segment is connected with a first end of the frequency doubling crystal through the first lens, and a second end of the frequency doubling crystal is connected with the optical fiber beam splitter through the second lens.

[0013] The third optical fiber segment is used for compensation of the first supercontinuum spectrum into a second supercontinuum spectrum; wherein a second long wave and a second short wave of the second supercontinuum spectrum are time-domain aligned; the first lens is used for focusing the second supercontinuum spectrum to the frequency doubling crystal, the frequency doubling crystal is used for frequency doubling of the second long wave to a wavelength matched with the second short wave to obtain a frequency-doubled signal, the second lens is used for collimation and coupling of the frequency-doubled signal and the second short wave of the second supercontinuum spectrum into the target supercontinuum spectrum and providing the target supercontinuum spectrum to the optical fiber beam splitter, and the optical fiber beam splitter is used for dividing the target supercontinuum spectrum into multiple paths for output.

[0014] The wavelength of the second short wave is the same as that of the first short wave.

[0015] Optionally, the optical fiber beam splitter comprises a first output interface; the supercontinuum spectrum generation system further comprises a fourth optical fiber segment.

[0016] The first output interface is used for direct output of the target supercontinuum spectrum through the fourth optical fiber segment.

[0017] Optionally, the supercontinuum spectrum generation system further comprises a fifth optical fiber segment, a filter and a photodetector; the optical fiber beam splitter comprises a second output interface.

[0018] The second output interface is connected with the filter through the fifth optical fiber segment, and the filter is connected with the photodetector.

[0019] The filter is configured to filter the target supercontinuum spectrum to obtain the frequency-doubled signal and the second short wave; and the photodetector is configured to count in a unit of time and obtain the initial frequency of the femtosecond seed pulse according to the frequency-doubled signal and the second short wave.

[0020] Optionally, the supercontinuum spectrum generation system further comprises a first flange and a second flange.

[0021] The first optical fiber segment is connected to the output end of the femtosecond pulse generation module through the first flange, and the filter is connected to the photodetector through the second flange.

[0022] Optionally, the femtosecond pulse generation module comprises a first input interface, a wavelength division multiplexer, a sixth optical fiber segment, a seventh optical fiber segment, and an eighth optical fiber segment.

[0023] The first input interface is connected to a first end of the wavelength division multiplexer, a second end of the wavelength division multiplexer is fusion-spliced to the sixth optical fiber segment, a third end of the wavelength division multiplexer is connected to an external pump laser input module, the sixth optical fiber segment is fusion-spliced to the seventh optical fiber segment, the seventh optical fiber segment is fusion-spliced to the eighth optical fiber segment, and the eighth optical fiber segment is connected to the first optical fiber segment.

[0024] The first input interface is configured to receive the femtosecond seed pulse, the wavelength division multiplexer is configured to couple the pump laser provided by the external pump laser input module to the sixth optical fiber segment in a reverse direction, the sixth optical fiber segment is configured to pre-chirp the femtosecond seed pulse, the seventh optical fiber segment is configured to amplify the power of the femtosecond seed pulse according to the pump laser, and the eighth optical fiber segment is configured to compress the pulse width of the amplified femtosecond seed pulse to generate the femtosecond pulse.

[0025] Optionally, the femtosecond pulse generation module and the self-referenced interference unit adopt a full polarization-maintaining optical fiber structure.

[0026] The present disclosure also provides a supercontinuum spectrum generation device comprising any of the supercontinuum spectrum generation systems described above and a packaging shell.

[0027] The supercontinuum spectrum generation system is packaged in the packaging shell; a first interface of the packaging shell is connected to the input end of the femtosecond pulse generation module, the first interface of the packaging shell is configured to be connected to an external pulse output module; a second interface of the packaging shell is connected to the wavelength division multiplexer of the femtosecond pulse generation module, the second interface of the packaging shell is configured to be connected to an external pump laser input module; a third interface of the packaging shell is connected to the self-referenced interference unit of the supercontinuum spectrum generation module, the third interface of the packaging shell is configured to output the generated supercontinuum spectrum; and a fourth interface of the packaging shell is connected to the photodetector of the supercontinuum spectrum generation system, the fourth interface of the packaging shell is configured to output the initial frequency of the femtosecond seed pulse.

[0028] The present disclosure also provides a supercontinuum spectrum generation apparatus comprising the supercontinuum spectrum generation device described above.

[0029] The present disclosure provides a supercontinuum generation system, device and equipment, the supercontinuum generation system comprising: a femtosecond pulse generation module and a spectrum expansion module. The input end of the femtosecond pulse generation module is used to receive a femtosecond seed pulse, and the femtosecond pulse generation module is used to perform time domain shaping, amplification or reduction and compression on the femtosecond seed pulse to generate a femtosecond pulse. The spectrum expansion module comprises a first optical fiber segment, a second optical fiber segment and a self-referenced interference unit; the first optical fiber segment is connected with the output end of the femtosecond pulse generation module, the first optical fiber segment is fusion spliced with the second optical fiber segment, and the second optical fiber segment is connected with the self-referenced interference unit; the first optical fiber segment is used to perform high-order soliton self-compression on the femtosecond pulse; the second optical fiber segment is used to broaden the spectrum of the femtosecond pulse under near-zero dispersion conditions to generate a first supercontinuum by frequency doubling. The present disclosure inputs the femtosecond pulse into the first optical fiber segment, performs high-order soliton self-compression on the femtosecond pulse in the first optical fiber segment, so that the pulse peak power of the femtosecond pulse is improved, thereby enhancing the nonlinear spectral broadening capability thereof. Then, the self-compressed femtosecond pulse is input into the second optical fiber segment, the spectrum of the femtosecond pulse is broadened under near-zero dispersion conditions in the second optical fiber segment to generate a first supercontinuum by frequency doubling, so that the flatness of the first supercontinuum is controlled within an ideal range. Moreover, the present disclosure converts the femtosecond pulse into a first supercontinuum by sequentially adopting soliton self-compression and near-zero dispersion broadening, so that the coherence degradation caused by soliton splitting can be effectively avoided, thereby ensuring the stable operation of the supercontinuum generation system, and further ensuring that the output supercontinuum has high coherence. Moreover, the present disclosure can ensure that the first supercontinuum has high coherence and high flatness only by the first optical fiber segment and the second optical fiber segment, so that the supercontinuum generation system provided by the present disclosure has a simple structure. The first supercontinuum generated after the first optical fiber segment and the second optical fiber segment is further input into the self-referenced interference unit, the self-referenced interference unit is used to align the first long wave and the first short wave of the first supercontinuum in the time domain, and the self-referenced interference unit is further used to output a target supercontinuum after the first short wave is coaxial with the first long wave after frequency doubling. The present disclosure performs time domain optimization on the first supercontinuum in the self-referenced interference unit to obtain a target supercontinuum that can be used to obtain the initial frequency of the femtosecond seed pulse, or used as a flat supercontinuum light source, and the output target supercontinuum has high coherence and high flatness. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0031] Figure 1A structural schematic diagram of an ultrashort pulse laser system provided by an embodiment of the present disclosure.

[0032] Figure 2 A structural schematic diagram of an ultrashort pulse laser system provided by an embodiment of the present disclosure.

[0033] Figure 3 A structural schematic diagram of an ultrashort pulse laser system provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0034] Features and exemplary embodiments of various aspects of the present application will be described below in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application can be practiced without some or all of these specific details. The description of the embodiments is merely intended to provide a better understanding of the present application by showing examples of the present application.

[0035] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The embodiments will be described in detail below with reference to the accompanying drawings.

[0036] It should be noted that, in this document, the terms such as first and second are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Also, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or device. Without more limitations, the elements defined by the statement "include" do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0037] It should be understood that, when describing the structure of a component, when one layer, one region is referred to as being "on" or "above" another layer, another region, it can mean being directly on or above the other layer, another region, or containing other layers or regions therebetween. And if the component is flipped, the one layer, one region will be "under" or "below" the other layer, another region.

[0038] It should be understood that the term "and / or" used herein is merely an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A existing alone, A and B existing together, and B existing alone. In addition, the character " / " herein generally represents an "or" relationship between the front and rear associated objects.

[0039] In the embodiments of the present application, the term "electrically connected" can mean that two components are directly electrically connected, or that two components are electrically connected via one or more other components.

[0040] In the embodiments of the present application, the first node, the second node and the third node are only defined for the convenience of describing the circuit structure, and the first node, the second node and the third node are not an actual circuit unit.

[0041] Various modifications and changes can be made to the present application without departing from the spirit or scope of the present application, which will be apparent to those skilled in the art. Therefore, the present application is intended to cover the modifications and changes of the present application falling within the scope of the corresponding claims (claimed technical solutions) and their equivalents. It should be noted that the embodiments provided by the present application can be combined with each other without contradiction.

[0042] When an ultra-short pulse laser propagates in a nonlinear medium, its spectrum will be significantly broadened under the influence of the cooperative effect of nonlinear effects and group velocity dispersion, thereby forming a supercontinuum spectrum with a super-wideband spectrum structure. The supercontinuum spectrum with wideband, high coherence, low noise and long-time stability is an important basic light source in the fields of modern spectroscopy, optical metrology and precise frequency measurement.

[0043] In the related art, the supercontinuum spectrum is usually generated by a soliton driving mechanism, but the supercontinuum spectrum generated by using this mechanism has the problem of uneven envelope. In order to improve the flatness problem of the supercontinuum spectrum, some studies propose to generate the supercontinuum spectrum by combining an all-normal dispersion (ANDi) photonic crystal fiber with a high-energy ultra-short pulse. Although this method can obtain a smoother spectrum structure and lower phase noise, it requires extremely high peak power, resulting in high cost and large volume of the required laser system, which is difficult to adapt to the needs of integration or external deployment in the laboratory.

[0044] Therefore, the current supercontinuum spectrum generation technology is faced with a "dilemma": the soliton driving method is easy to implement, but has the problems of uneven supercontinuum spectrum and degradation of coherence. The all-normal dispersion scheme has excellent spectrum quality and low noise characteristics, but requires extremely high energy and stability of the laser source, which is not conducive to actual deployment and integrated design.

[0045] To solve the above technical problems, the embodiments of the present application provide a supercontinuum generation system, device and equipment.

[0046] Figure 1 A structural schematic diagram of a supercontinuum generation system provided by the embodiments of the present application is shown in FIG. 1. Figure 1 The supercontinuum generation system comprises a femtosecond pulse generation module 10 and a spectrum expansion module 20.

[0047] The input end of the femtosecond pulse generation module 10 is configured to receive a femtosecond seed pulse, and the femtosecond pulse generation module 10 is configured to perform time-domain shaping, amplification or reduction and compression on the femtosecond seed pulse to generate a femtosecond pulse.

[0048] For example, the input end of the femtosecond pulse generation module 10 is configured to be connected with an external femtosecond seed pulse providing module, receive the femtosecond seed pulse provided by the external femtosecond seed pulse providing module, and sequentially perform pre-chirp, power amplification and compression on the femtosecond seed pulse to generate a femtosecond pulse.

[0049] The spectrum expansion module 20 comprises a first optical fiber segment 210, a second optical fiber segment 220 and a self-referenced interference unit 230. The first optical fiber segment 210 is connected with the output end of the femtosecond pulse generation module 10. The first optical fiber segment 210 is fusion spliced with the second optical fiber segment 220. The second optical fiber segment 220 is connected with the self-referenced interference unit 230.

[0050] For example, the first optical fiber segment 210 and the second optical fiber segment 220 are connected in a fusion splicing manner. Since the loss of fusion splicing is less than 0.1 dB, the power loss in the process of generating a first supercontinuum by the femtosecond pulse passing through the first optical fiber segment 210 and the second optical fiber segment 220 can be reduced.

[0051] The first optical fiber segment 210 is configured to perform high-order soliton self-compression on the femtosecond pulse. The second optical fiber segment 220 is configured to broaden the spectrum of the femtosecond pulse under near-zero dispersion conditions to generate a first supercontinuum by frequency doubling. The self-referenced interference unit 230 is configured to align the first long wave and the first short wave of the first supercontinuum in the time domain. The self-referenced interference unit is also configured to output a target supercontinuum after the first short wave and the first long wave after frequency doubling are coaxial.

[0052] Exemplarily, the first fiber segment 210 is an anomalous dispersion polarization maintaining high nonlinear fiber, and the second fiber segment 220 is a near-zero dispersion polarization maintaining high nonlinear fiber. The femtosecond pulse generation module 10 provides the femtosecond pulse to the first fiber segment 210, the femtosecond pulse forms a high-order soliton in the first fiber segment 210 and undergoes a self-compression process, thereby increasing the pulse peak power of the femtosecond pulse and enhancing the nonlinear spectral broadening capability of the femtosecond pulse. The self-compressed femtosecond pulse is input into the second fiber segment 220, and the second fiber segment 220 relies on the self-phase modulation and optical wave breaking effect to broaden the spectrum of the femtosecond pulse to generate a first supercontinuum spectrum by frequency doubling. The wavelength range of the first supercontinuum spectrum is 960-2200 nm, and the spectral flatness in the range of 960-1550 nm is controlled within 9 dB, so that the flatness of the first supercontinuum spectrum is controlled within the ideal range. The disclosure converts the femtosecond pulse into the first supercontinuum spectrum by sequentially using the soliton self-compression and the near-zero dispersion broadening, thereby effectively avoiding the coherence degradation caused by the soliton splitting, thereby ensuring the stable operation of the supercontinuum spectrum generation system, and further ensuring that the output supercontinuum spectrum has high coherence. Moreover, the disclosure can ensure that the first supercontinuum spectrum has high coherence and high flatness only by using the first fiber segment 210 and the second fiber segment 220, so that the supercontinuum spectrum generation system provided by the disclosure has a simple structure. The first supercontinuum spectrum generated after the first fiber segment 210 and the second fiber segment 220 is also input into the self-reference interference unit 230, and the self-reference interference unit 230 is used to align the first long wave and the first short wave of the first supercontinuum spectrum in the time domain. The self-reference interference unit 230 is also used to frequency double the first long wave to match the wavelength of the first long wave with the first short wave, and after the first short wave and the frequency-doubled first long wave are coaxial, a target supercontinuum spectrum is output. The disclosure obtains the initial frequency of the femtosecond seed pulse or the target supercontinuum spectrum used as a flat supercontinuum light source by optimizing the first supercontinuum spectrum in the time domain in the self-reference interference unit 230, and the output target supercontinuum spectrum has high coherence and high flatness.

[0053] In some embodiments, the length of the second fiber segment 220 is greater than the length of the first fiber segment 210; wherein the first fiber segment 210 and the second fiber segment 220 are both nonlinear fibers, and the dispersion parameters of the first fiber segment 210 and the second fiber segment 220 are different.

[0054] For example, the first fiber segment 210 is a polarization maintaining high nonlinear fiber of anomalous dispersion type, the nonlinear coefficient of the first fiber segment 210 is about 10.8 W⁻¹·km⁻¹, and the dispersion parameter of the first fiber segment 210 is about +5 ps / (nm·km). The second fiber segment 220 is a polarization maintaining high nonlinear fiber of near-zero dispersion type, the nonlinear coefficient of the second fiber segment 220 is close to the nonlinear coefficient of the first fiber segment 210, and the dispersion parameter of the second fiber segment 220 is controlled within the range of 1±1 ps / (nm·km). The length ratio of the first fiber segment 210 to the second fiber segment 220 can be, for example, 1:9, and the total length of the first fiber segment 210 and the second fiber segment 220 can be 0.6 m, so that the compact integration of the supercontinuum generation system can be realized. Moreover, the length of the second fiber segment 220 is greater than the length of the first fiber segment 210, and the problem of high-order soliton splitting after soliton self-compression caused by the excessively long length of the first fiber segment 210 can be avoided, so that the subsequent flat spectrum expansion can be ensured.

[0055] In some embodiments, Figure 2 A structural schematic diagram of a supercontinuum generation system provided by the embodiments of the present disclosure is shown in FIG. 2. Figure 2 As shown in FIG. 2, the self-referencing interference unit 230 includes a frequency doubling crystal 232, a first lens 233, and a second lens 234. The supercontinuum generation system further includes a third fiber segment 231 and a fiber beam splitter 30.

[0056] The third fiber segment 231 is fusion connected with the second fiber segment 220, the third fiber segment 231 is connected with the first end of the frequency doubling crystal 232 through the first lens 233, and the second end of the frequency doubling crystal 232 is connected with the fiber beam splitter 30 through the second lens 234.

[0057] The third fiber segment 231 is used for compensating the first supercontinuum into a second supercontinuum; wherein the second long wave and the second short wave of the second supercontinuum are aligned in time domain; the first lens 233 is used for focusing the second supercontinuum to the frequency doubling crystal 232, the frequency doubling crystal 232 is used for doubling the frequency of the second long wave to a wavelength matched with the second short wave to obtain a frequency-doubled signal, the second lens 234 is used for collimating and coupling the frequency-doubled signal and the second short wave of the second supercontinuum into a target supercontinuum and providing the target supercontinuum to the fiber beam splitter 30, and the fiber beam splitter 30 is used for dividing the target supercontinuum into multiple paths.

[0058] The wavelength of the first long wave and the second long wave is greater than 1000 nm and less than 2000 nm, the wavelength of the first short wave and the second short wave is less than 1000 nm, and the wavelength of the second short wave is the same as that of the first short wave.

[0059] For example, the third fiber segment 231 is a polarization maintaining fiber PM1550. The third fiber segment 231 compensates for the group velocity mismatch between the first long wave and the first short wave in the first supercontinuum spectrum by using the dispersion characteristics of the polarization maintaining fiber, avoids the influence of alignment errors and thermal drift in the traditional spatial optical path, and aligns the first long wave and the first short wave in the time domain, thereby generating a second supercontinuum spectrum. The second long wave and the second short wave in the second supercontinuum spectrum are aligned in the time domain, and thus conditions are created for coupling the frequency-doubled signal and the second short wave of the second supercontinuum spectrum after collimation.

[0060] The frequency-doubling crystal 232 can be, for example, a periodically poled lithium niobate crystal, and the polarization period of the frequency-doubling crystal 232 is about 30 μm. The frequency-doubling crystal 232 is also coated with a 2000 nm antireflection film on the surface. The polarization period of the frequency-doubling crystal 232 satisfies the phase matching condition of the second long wave, and thus the second long wave can be frequency-doubled into a frequency-doubled signal with a wavelength matching that of the second short wave. The wavelength of the frequency-doubled signal is less than 1000 nm. The frequency-doubled signal and the second short wave of the second supercontinuum spectrum are collimated by the second lens 234 and then pass through a polarization maintaining fiber. The frequency-doubling crystal 232 uses the second lens 234 to collimate the frequency-doubled signal and the second short wave and then re-enters the polarization maintaining fiber, which facilitates subsequent all-fiber integration and packaging. The frequency-doubled signal and the second short wave of the second supercontinuum spectrum propagate coaxially in the polarization maintaining fiber, and thus are coupled into a target supercontinuum spectrum and provided to the fiber beam splitter 30. The fiber beam splitter 30 can split the target supercontinuum spectrum into multiple paths for output, divide the target supercontinuum spectrum into multiple signals in proportion for output, or directly provide the target supercontinuum spectrum.

[0061] The self-referencing interference unit 230 forms a coaxial fiber structure through the frequency-doubling crystal 232, the first lens 233, and the second lens 234, and thus avoids path mismatch caused by air disturbance and optical path vibration. As a result, the supercontinuum spectrum generation system does not need an additional spatial delay line, and thus the stability of the supercontinuum spectrum generation system is significantly improved.

[0062] In some embodiments, continuing to refer to Figure 2 The fiber beam splitter 30 includes a first output interface 31, and the supercontinuum spectrum generation system further includes a fourth fiber segment 40. The first output interface 31 is configured to directly output the target supercontinuum spectrum through the fourth fiber segment 40.

[0063] For example, the fourth fiber segment 40 is a polarization maintaining fiber PM1550. The first output interface 31 of the fiber beam splitter 30 directly provides the target supercontinuum spectrum to the fourth fiber segment 40, and the other end of the fourth fiber segment 40 is connected to an FC / APC connector, so that the target supercontinuum spectrum can be output to an external module, thereby realizing that the supercontinuum spectrum generation system is used as a flat supercontinuum light source.

[0064] In some embodiments, continuing to refer toFigure 2 The supercontinuum generation system further comprises a fifth fiber segment 50, a filter 60, and a photodetector 70; the fiber beam splitter 30 comprises a second output interface 32;

[0065] The second output interface 32 is connected with the filter 60 through the fifth fiber segment 50, and the filter 60 is connected with the photodetector 70.

[0066] The filter 60 is used for filtering the target supercontinuum to obtain the frequency-doubled signal and the second short wave; and the photodetector 70 is used for counting in a unit of time, and obtaining the initial frequency of the femtosecond seed pulse according to the frequency-doubled signal and the second short wave.

[0067] For example, the filter 60 is a narrowband optical filter with a bandwidth of 2-3 nm, and the fifth fiber segment 50 is a polarization maintaining fiber PM1550. After the target supercontinuum output by the second output interface 32 passes through the filter 60, the filter 60 filters out the interference signals in the target supercontinuum, thereby obtaining the frequency-doubled signal and the second short wave with a wavelength less than 1000 nm, and providing the frequency-doubled signal and the second short wave to the photodetector 70. The photodetector 70 converts the frequency-doubled signal and the second short wave into a radio frequency electrical signal with a frequency equal to the initial frequency of the femtosecond seed pulse through optical heterodyne detection, and the initial frequency of the femtosecond seed pulse can be obtained by observing the radio frequency electrical signal. Moreover, the obtained radio frequency electrical signal has a signal-to-noise ratio better than 35 dB, which can meet the requirements of high-speed feedback and frequency locking, and is conducive to realizing long-term stable operation of the frequency comb.

[0068] In some embodiments, continuing to refer to Figure 2 The supercontinuum generation system further comprises a first flange 81 and a second flange 82.

[0069] The first fiber segment 210 is connected with the output end of the femtosecond pulse generation module 10 through the first flange 81, and the filter 60 is connected with the photodetector 70 through the second flange 82.

[0070] For example, the two ends of the first flange 81 and the second flange 82 are detachable, so that the first flange 81 can be connected with only the first fiber segment 210 or only the output end of the femtosecond pulse generation module 10, and the second flange 82 can be connected with only the filter 60 or only the photodetector 70. Therefore, the first flange 81 can be replaced with a module connected with the first fiber segment 210 or the output end of the femtosecond pulse generation module 10 at will according to requirements, and the second flange 82 can be replaced with a module connected with the filter 60 or the photodetector 70 at will according to requirements.

[0071] In some embodiments, continuing to refer to Figure 2The femtosecond pulse generation module comprises a first input interface 110, a wavelength division multiplexer 120, a sixth fiber segment 130, a seventh fiber segment 140, and an eighth fiber segment 150.

[0072] The first input interface 110 is connected with a first end of the wavelength division multiplexer 120, a second end of the wavelength division multiplexer 120 is fusion spliced with the sixth fiber segment 130, a third end of the wavelength division multiplexer 120 is connected with an external pump laser input module, the sixth fiber segment 130 is fusion spliced with the seventh fiber segment 140, the seventh fiber segment 140 is fusion spliced with the eighth fiber segment 150, and the eighth fiber segment 150 is connected with the first fiber segment 210.

[0073] The first input interface 110 is configured to receive a femtosecond seed pulse, the wavelength division multiplexer 120 is configured to backward couple pump laser provided by an external pump laser input module into the sixth fiber segment 130, the sixth fiber segment 130 is configured to pre-chirp the femtosecond seed pulse, the seventh fiber segment 140 is configured to amplify power of the femtosecond seed pulse according to the pump laser, and the eighth fiber segment 150 is configured to compress pulse width of the amplified femtosecond seed pulse to generate a femtosecond pulse.

[0074] For example, the first input interface 110 is an FC / APC plug, which is configured to be connected with an external femtosecond seed pulse providing module to receive the femtosecond seed pulse provided externally. The first input interface 110 is connected with a laser isolator 160 through a polarization maintaining optical fiber PM1550, the laser isolator 160 is configured to ensure unidirectional propagation of the femtosecond seed pulse and avoid reverse propagation of other optical signals. The laser isolator 160 is connected with a first end of the wavelength division multiplexer 120 through the polarization maintaining optical fiber PM1550, a third end of the wavelength division multiplexer 120 is connected with an external pump laser input module to receive pump laser provided by the external pump laser input module. The wavelength division multiplexer 120 backward couples the pump laser into the sixth fiber segment 130, so that distributed amplification of the femtosecond seed pulse can be realized in the sixth fiber segment 130 and the seventh fiber segment 140, and amplification efficiency and noise performance are optimized. The femtosecond seed pulse is pre-chirped in the sixth fiber segment 130, and power of the femtosecond seed pulse is amplified in the seventh fiber segment 140, so that the pulse energy is greater than 1 nJ. The eighth fiber segment 150 is configured to compress pulse width of the amplified femtosecond seed pulse, so that the pulse width is less than 100 fs, and finally a femtosecond pulse is generated, which is provided to the first fiber segment 210.

[0075] In some embodiments, the femtosecond pulse generation module 10 and the self-referenced interference unit 230 adopt a full polarization maintaining optical fiber structure.

[0076] Exemplarily, since the entire supercontinuum generation system adopts the all-polarization-maintaining fiber structure, the supercontinuum generation system has excellent anti-interference ability and repeatability, is suitable for being packaged into a portable module, and can be deployed in an environment outside a laboratory.

[0077] Figure 3 A structural schematic diagram of a supercontinuum generation device provided by an embodiment of the present disclosure is shown in FIG. 1. Figure 3 As shown in FIG. 1, the supercontinuum generation device includes a supercontinuum generation system provided by any of the above embodiments and a packaging shell 90.

[0078] The supercontinuum generation system is packaged in the packaging shell 90; a first interface 91 of the packaging shell 90 is connected with an input end of the femtosecond pulse generation module, the first interface 91 of the packaging shell 90 is used to be connected with an external pulse output module; a second interface 92 of the packaging shell 90 is connected with a wavelength division multiplexer of the femtosecond pulse generation module, the second interface 92 of the packaging shell 90 is used to be connected with an external pump laser input module; a third interface 93 of the packaging shell 90 is connected with a self-reference interference unit of the spectrum expansion module, the third interface 93 of the packaging shell 90 is used to output the generated supercontinuum; and a fourth interface 94 of the packaging shell 90 is connected with a photodetector of the supercontinuum generation system, the fourth interface 94 of the packaging shell 90 is used to output an initial frequency of the femtosecond seed pulse.

[0079] Exemplarily, a fifth interface 95 of the packaging shell 90 is used to supply power for the photodetector. Since the supercontinuum generation system adopts the all-polarization-maintaining fiber structure, and the total length of the first fiber segment and the second fiber segment is 60 cm, the supercontinuum generation system can be packaged in the packaging shell 90 and can be deployed in an environment outside a laboratory.

[0080] It can be understood that the supercontinuum generation device provided by the embodiment of the present disclosure can also achieve the corresponding beneficial effects of the supercontinuum generation system provided by the above embodiments, which will not be described here.

[0081] The present disclosure further provides a supercontinuum generation device, which includes the supercontinuum generation device provided by the above embodiments.

[0082] It can be understood that the supercontinuum generation device provided by the embodiment of the present disclosure can also achieve the corresponding beneficial effects of the supercontinuum generation device provided by the above embodiments, which will not be described here.

[0083] The foregoing is merely illustrative of the various implementations of the present disclosure and the general principles thereof. Numerous modifications can be made to these illustrations, and equivalents can be substituted therefor, without departing from the scope of the present disclosure. The specific embodiments commensurate with the specific application are intended to be illustrative only and not limiting of the scope of the application as set forth in the following claims.

Claims

1. An ultrabroadband spectrum generation system, characterized by, The application relates to a supercontinuum spectrum generation system. The supercontinuum spectrum generation system comprises a femtosecond pulse generation module, a spectrum expansion module and a self-referenced interference unit. The femtosecond pulse generation module is used for receiving a femtosecond seed pulse, time-domain shaping, amplifying or reducing and compressing the femtosecond seed pulse to generate a femtosecond pulse. The spectrum expansion module comprises a first optical fiber segment, a second optical fiber segment and a self-referenced interference unit. The first optical fiber segment is connected with the output end of the femtosecond pulse generation module. The first optical fiber segment is used for self-compression of the femtosecond pulse. The second optical fiber segment is used for spectrum expansion of the femtosecond pulse under near-zero dispersion conditions to generate a first supercontinuum spectrum by frequency doubling. The self-referenced interference unit is used for time-domain alignment of a first long wave and a first short wave of the first supercontinuum spectrum.

2. The supercontinuum generation system of claim 1, wherein, The self-referenced interference unit is also used for coaxial output of the first short wave and the first long wave after frequency doubling to output a target supercontinuum spectrum.

3. The supercontinuum generation system of claim 1, wherein, The self-referenced interference unit comprises a frequency doubling crystal, a first lens and a second lens. The supercontinuum spectrum generation system further comprises a third optical fiber segment and an optical fiber beam splitter.

4. The supercontinuum generation system of claim 1, wherein, The third optical fiber segment is connected with the second optical fiber segment by fusion splicing. The third optical fiber segment is connected with the first end of the frequency doubling crystal through the first lens. The second end of the frequency doubling crystal is connected with the optical fiber beam splitter through the second lens. The third optical fiber segment is used for compensation of the first supercontinuum spectrum into a second supercontinuum spectrum. The second lens is used for collimation and coupling of the frequency doubling signal and the second short wave of the second supercontinuum spectrum into the target supercontinuum spectrum and providing the target supercontinuum spectrum to the optical fiber beam splitter. The optical fiber beam splitter is used for splitting the target supercontinuum spectrum into multiple paths. The second short wave has the same wavelength as the first short wave. The length of the second optical fiber segment is greater than the length of the first optical fiber segment. The first optical fiber segment and the second optical fiber segment are both nonlinear optical fibers. The dispersion parameters of the first optical fiber segment and the second optical fiber segment are different. The optical fiber beam splitter comprises a first output interface. The supercontinuum spectrum generation system further comprises a fourth optical fiber segment. The first output interface is used for direct output of the target supercontinuum spectrum through the fourth optical fiber segment. The supercontinuum spectrum generation system further comprises a fifth optical fiber segment, a filter and a photodetector. The optical fiber beam splitter comprises a second output interface. The second output interface is connected with the filter through the fifth optical fiber segment. The filter is used for filtering the target supercontinuum spectrum to obtain the frequency doubling signal and the second short wave. The photodetector is used for counting in unit time and obtaining the initial frequency of the femtosecond seed pulse according to the frequency doubling signal and the second short wave.

5. The supercontinuum generation system of claim 4, wherein, The supercontinuum generation system further comprises a first flange and a second flange; The first fiber segment is connected with the output end of the femtosecond pulse generation module through the first flange, and the filter is connected with the photodetector through the second flange.

6. The supercontinuum generation system of claim 1, wherein, The femtosecond pulse generation module comprises a first input interface, a wavelength division multiplexer, a sixth fiber segment, a seventh fiber segment and an eighth fiber segment. The first input interface is connected with a first end of the wavelength division multiplexer, a second end of the wavelength division multiplexer is fusion-spliced with the sixth fiber segment, a third end of the wavelength division multiplexer is connected with an external pump laser input module, the sixth fiber segment is fusion-spliced with the seventh fiber segment, the seventh fiber segment is fusion-spliced with the eighth fiber segment, and the eighth fiber segment is connected with the first fiber segment. The first input interface is configured to receive the femtosecond seed pulse, the wavelength division multiplexer is configured to couple pump laser provided by the external pump laser input module to the sixth fiber segment in a reverse direction, the sixth fiber segment is configured to pre-chirp the femtosecond seed pulse, the seventh fiber segment is configured to amplify the power of the femtosecond seed pulse according to the pump laser, and the eighth fiber segment is configured to compress the pulse width of the amplified femtosecond seed pulse to generate the femtosecond pulse.

7. The supercontinuum generation system of any of claims 1-6, wherein the nonlinear medium is a photonic crystal fiber. The femtosecond pulse generation module and the self-referenced interference unit adopt a full polarization-maintaining fiber structure.

8. An apparatus for supercontinuum generation, characterized in that The supercontinuum generation system comprises a packaging shell. The supercontinuum generation system is packaged in the packaging shell, a first interface of the packaging shell is connected with an input end of the femtosecond pulse generation module, the first interface of the packaging shell is configured to be connected with an external pulse output module, a second interface of the packaging shell is connected with a wavelength division multiplexer of the femtosecond pulse generation module, the second interface of the packaging shell is configured to be connected with an external pump laser input module, a third interface of the packaging shell is connected with a self-referenced interference unit of the supercontinuum generation module, and the third interface of the packaging shell is configured to output the generated supercontinuum spectrum. A fourth interface of the packaging shell is connected with a photodetector of the supercontinuum generation system, and the fourth interface of the packaging shell is configured to output an initial frequency of the femtosecond seed pulse.

9. An apparatus for supercontinuum generation, characterized in that The supercontinuum generation device comprises the supercontinuum generation system.

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