Programmable generation system and method of soliton molecular laser

Abstract

The present application belongs to the field of laser technology, and relates to a programmable generation system and method of soliton molecular laser, wherein the generation system comprises: a fiber ring laser resonator formed by a pump source, a wavelength division multiplexer, a gain fiber, an output coupler, a polarization-independent isolator, a saturable absorber, a polarization controller, a bandpass filter, and a programmable optical controller that are fused in sequence, wherein the output end pigtail of the programmable optical controller is fused with the through end pigtail of the wavelength division multiplexer. The programmable generation system of soliton molecular laser in the present application is a highly customized and environmentally resistant soliton molecular laser generation system, which has the characteristics of simple structure and low maintenance cost, can accurately adjust the soliton spacing and the number of solitons of soliton molecules as needed, and improves the adjustment efficiency, accuracy and controllability of the soliton spacing and the number of solitons.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to a programmable generation system of a soliton molecular laser and a programmable generation method of a soliton molecular laser. Background Art

[0002] Soliton, also known as solitary wave, is a stable localized structure that can maintain its shape and strength during propagation. Soliton molecules are new soliton states formed when a soliton splits into multiple solitons in a nonlinear system and is bound together through a self-organizing process.

[0003] Soliton molecules are similar to material molecules and have multiple degrees of freedom, such as phase relationship, time domain spacing, number of solitons, etc. Currently, there are two methods to adjust the soliton spacing and number of solitons: manual adjustment and artificial intelligence (AI) adjustment. However, manual adjustment has the problems of low efficiency, poor adjustment accuracy, and inability to adjust on demand. AI adjustment requires setting up feedback devices, writing algorithms, and training models, which greatly increases the complexity of the laser and increases maintenance costs.

[0004] Therefore, it is necessary to provide a new system and method for programmable generation of soliton molecular lasers.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0006] The purpose of the present application is to provide a programmable generation system of a soliton molecular laser and a programmable generation method of a soliton molecular laser, thereby at least to a certain extent overcoming the problems of high system complexity, low efficiency, poor accuracy and inability to adjust the soliton spacing and soliton number as caused by the limitations and defects of the relevant technologies.

[0007] According to one aspect of the present application, a programmable generation system of soliton molecular laser is provided, comprising: a fiber ring laser resonant cavity formed by a pump source, a wavelength division multiplexer, a gain fiber, an output coupler, a polarization-independent isolator, a saturable absorber, a polarization controller, a bandpass filter and a programmable optical controller which are fused in sequence, wherein the output end pigtail of the programmable optical controller is fused with the through end pigtail of the wavelength division multiplexer; the programmable optical controller is used to transfer energy to the solitons circulating in the fiber ring laser resonant cavity according to the phase period in the pre-written frequency phase function, generate a main pulse and a sub-pulse spaced from the main pulse by a preset time domain spacing, wherein the main pulse and the sub-pulse form a soliton molecule containing a plurality of solitons after multiple rounds of circulation in the fiber ring laser resonant cavity; the bandpass filter is used to filter out the dispersion waves carried by the soliton molecules to obtain soliton molecules with a stable time domain spacing.

[0008] In an exemplary embodiment of the present application, the programmable light controller includes a first collimating lens, a diffraction grating, a cylindrical mirror, a liquid crystal spatial light modulator and a second collimating lens, the first collimating lens is connected to the output end pigtail of the bandpass filter, the second collimating lens is connected to the through end pigtail of the wavelength division multiplexer, and the liquid crystal spatial light modulator is connected to a computer device, and the computer device is used to write the frequency phase function into the liquid crystal spatial light modulator.

[0009] In an exemplary embodiment of the present application, the first collimating lens is used to collimate the solitons output by the bandpass filter and input them to the diffraction grating; the diffraction grating is used to perform spectral decomposition on the solitons to form multiple incident lights of different frequencies, and send the incident lights of different frequencies to the cylindrical mirror, so that the cylindrical mirror reflects the incident lights of different frequencies to the liquid crystal spatial light modulator; the liquid crystal spatial light modulator is used to modulate the incident lights of different frequencies according to the phase period, and send the incident lights of different frequencies after phase modulation to the cylindrical mirror, so that the cylindrical mirror reflects the incident lights of different frequencies after phase modulation to the diffraction grating for spectral synthesis to form the main pulse and the sub-pulse; the second collimating lens is used to collimate the main pulse and the sub-pulse and input them to the wavelength division multiplexer, so that the main pulse and the sub-pulse enter the fiber ring laser resonator through the wavelength division multiplexer for multiple rounds of circulation to form the soliton molecules.

[0010] In an exemplary embodiment of the present application, the number of solitons in the soliton molecule increases as the pump power of the pump source increases.

[0011] In an exemplary embodiment of the present application, the wavelength division multiplexer is used to input the pump light output by the pump source and the soliton molecules output by the programmable light regulator into the gain optical fiber, so as to perform power amplification on the soliton molecules under the action of the pump light to generate amplified soliton molecules; the output coupler is used to divide the amplified soliton molecules into circulating soliton molecules and output soliton molecules according to a preset output coupling ratio, and the output soliton molecules are output through the coupling port of the output coupler; the polarization-independent isolator is used to ensure the unidirectional transmission of the circulating soliton molecules; the saturable absorber performs intensity modulation on the circulating soliton molecules based on the nonlinear saturable absorption effect, suppresses background noise, and stabilizes the soliton molecules; the polarization controller is used to optimize the polarization state and loss of the soliton molecules output by the saturable absorber.

[0012] In an exemplary embodiment of the present application, two adjacent components among the pump source, the wavelength division multiplexer, the gain fiber, the output coupler, the polarization-independent isolator, the saturable absorber, the polarization controller, the bandpass filter, the first collimating lens, and the second collimating lens are fused by single-mode optical fiber, and the operating band of the single-mode optical fiber is the same as the gain band of the gain optical fiber.

[0013] According to one aspect of the present application, a programmable generation method of a soliton molecular laser is provided, which is applied to the programmable generation system of the soliton molecular laser in the above-mentioned embodiment, comprising: when the fiber ring laser resonator achieves a stable mode-locked state, energy transfer is performed on the solitons output by the bandpass filter according to the phase period in the frequency phase function by the programmable optical controller to generate a main pulse and a sub-pulse spaced from the main pulse by a preset time domain spacing; the main pulse and the sub-pulse are input into the fiber ring laser resonator through the wavelength division multiplexer for multiple cycles to generate the soliton molecules; and the dispersion waves carried by the soliton molecules are filtered out by the bandpass filter to obtain soliton molecules with stable time domain spacing.

[0014] In an exemplary embodiment of the present application, the programmable light controller includes a first collimating lens, a diffraction grating, a cylindrical mirror, a liquid crystal spatial light modulator and a second collimating lens; the programmable light controller performs energy transfer on the solitons output by the bandpass filter according to the phase period in the frequency-phase function to generate a main pulse and a sub-pulse with a preset time domain spacing from the main pulse, including: collimating the solitons and inputting them into the diffraction grating through the first collimating lens for spectral decomposition to form a plurality of incident lights of different frequencies; reflecting the incident light emitted by the diffraction grating to the liquid crystal spatial light modulator through the cylindrical mirror, so that the liquid crystal spatial light modulator modulates the incident light according to the phase period to form output lights with different phases and different frequencies; reflecting the output light emitted by the liquid crystal spatial light modulator to the diffraction grating through the cylindrical mirror for spectral synthesis to form the main pulse and the sub-pulse; and collimating the main pulse and the sub-pulse and inputting them into the wavelength division multiplexer through the second collimating lens.

[0015] In an exemplary embodiment of the present application, the liquid crystal spatial light modulator includes a plurality of liquid crystal regions, and different frequency components of the incident light correspond to different liquid crystal regions; the liquid crystal spatial light modulator modulates the incident light according to the phase period to form output light with different phases and different frequencies, including: determining an applied voltage corresponding to each of the liquid crystal regions according to the phase period; applying the applied voltage to each of the liquid crystal regions to change the spatial orientation of the liquid crystal molecules in each of the liquid crystal regions, and adjusting the phase of the incident light incident to each of the liquid crystal regions based on the different spatial orientations of the liquid crystal molecules to generate the output light.

[0016] In an exemplary embodiment of the present application, the method further includes: when the frequency-phase function remains unchanged, increasing the pump power of the pump source to increase the number of solitons in the soliton molecule; or, when the pump power of the pump source remains unchanged, adjusting the phase period in the frequency-phase function to change the soliton spacing in the soliton molecule.

[0017] The programmable generation system of soliton molecular laser in the present application is a fiber ring laser resonant cavity formed by a pump source, a wavelength division multiplexer, an erbium-doped fiber, an output coupler, a polarization-independent isolator, a saturable absorber, a polarization controller, a bandpass filter and a programmable optical controller connected in sequence, wherein the output end pigtail of the programmable optical controller is fused with the through end pigtail of the wavelength division multiplexer; the programmable optical controller is used to transfer energy to the solitons circulating in the fiber ring laser resonant cavity according to the phase period in the pre-written frequency phase function, generate a main pulse and a sub-pulse with a preset time domain spacing from the main pulse, and the main pulse and the sub-pulse form a soliton molecule containing multiple solitons after multiple rounds of circulation in the fiber ring laser resonant cavity; the bandpass filter is used to filter out the dispersion waves carried by the soliton molecules to obtain soliton molecules with stable time domain spacing. The programmable generation system of soliton molecular laser in the present application has a simple optical path structure on the one hand, thereby reducing the preparation cost and maintenance cost; on the other hand, the dispersion wave carried by the soliton molecule is filtered out by a bandpass filter, which can eliminate the oscillation tail of the soliton molecule in the time domain, and avoid the oscillation tail changing the soliton spacing of the soliton molecule and causing the failure of frequency phase control; on the other hand, the soliton spacing in the soliton molecule is adjusted on demand according to the phase period in the preset frequency phase function by a programmable optical controller, thereby improving the regulation efficiency, regulation accuracy and controllability of the soliton spacing.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 The schematic diagram of the structure of the programmable generation system of soliton molecular laser in the present application is shown.

[0021] Figure 2 The schematic diagram of the programmable light controller in the present application is shown.

[0022] Figure 3 A schematic diagram of the process of generating a soliton molecule containing two solitons in the present application is shown.

[0023] Figure 4 A schematic diagram of the process of increasing the pump power to adjust the number of solitons in the soliton molecule in the present application is shown.

[0024] Figure 5 The figure shows a flow chart of the programmable generation method of soliton molecular laser in the present application.

[0025] Figure 6 The schematic diagram shows the process of energy transfer of solitons by the programmable optical controller in the present application.

[0026] Figure 7 The autocorrelation diagram of the soliton molecule at different phase periods when the pump power is 40 mW in the present application is shown.

[0027] Figure 8 This application shows Figure 7 The corresponding spectrum.

[0028] Fig. 9 The relationship between the actual soliton spacing in the present application and the theoretical soliton spacing determined based on the phase period is shown.

[0029] Fig.10 The autocorrelation diagram of the soliton molecule at different pump powers when the phase period is 0.083 THz in the present application is shown.

[0030] Fig.11 This application shows Fig.10 The corresponding spectrum. DETAILED DESCRIPTION

[0031] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present application will be more comprehensive and complete, and the concept of the example embodiments will be fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical solutions of the present application may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present application.

[0032] In addition, the accompanying drawings are only schematic illustrations of the present application and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0033] Ultrashort pulse lasers are widely used in scientific research and engineering applications due to their narrow pulse width and high energy, such as spectroscopy, optical communication, material processing, laser ranging, etc. Soliton molecules, as a kind of ultrashort pulse, can also be applied in many fields. For example, in optical communication systems, by encoding information such as the soliton spacing, soliton number, and phase relationship of soliton molecules, it is possible to transmit ultrafast high-capacity information flows and all-optical information storage; in the field of material processing, changes in soliton spacing will produce different heat-affected zones, significantly changing the quality and efficiency of micro-hole processing, which is of great significance for improving and enhancing material processing technology.

[0034] In traditional mode-locked lasers, the soliton spacing and the number of solitons are completely dependent on the parameters of the laser system, such as pump power, cavity loss, dispersion, birefringence, etc. These parameters are easily affected by the environment. When adjusting the soliton spacing and the number of solitons, manual adjustment, AI adjustment and other methods are usually used. However, the manual adjustment method has problems such as low efficiency, poor adjustment accuracy, and lack of precise controllability. The AI ​​adjustment method has problems such as high laser complexity, such as:

[0035] Patent CN210111285U discloses a soliton molecular laser with controllable soliton spacing and soliton number. In a nonlinear polarization rotation mode-locked fiber laser, the soliton spacing and soliton number are regulated by manually adjusting the laser polarization state and pump power. However, this method relies on manual operation, has poor adjustment accuracy, and does not have the precise controllability of on-demand adjustment.

[0036] The document "On-demand harnessing of photonic soliton molecules", Optica 9, 240-250 (2022) records that in a carbon nanotube mode-locked fiber laser, the soliton spacing is regulated by adjusting the second-order dispersion and dispersion loss of the laser. However, the regulation range of the soliton spacing in this method is determined by the dispersion loss and can only be limited to 10ps.

[0037] Patent CN115966986A discloses a method and device for generating a controllable pitch femtosecond laser pulse train, which generates pulse trains with different pitches by phase modulating multiple monochromatic continuous waves outside the laser cavity and superimposing them. However, the optical path outside the cavity of this method contains multiple cylindrical mirrors, lenses and polarizers, which makes the spatial optical path complex, has high maintenance costs, has large losses and is easily affected by environmental interference.

[0038] The document "On-demand generation of soliton molecules through evolutionary algorithm optimization", Optics Letters 47, 134-137 (2022) records that in a nonlinear polarization rotation mode-locked fiber laser, the laser polarization state, cavity loss and dispersion are adjusted in real time through artificial intelligence methods to adjust the soliton spacing. However, this method relies on circuit control systems and artificial intelligence algorithms, and the entire laser system is too complicated.

[0039] In summary, the methods for regulating the soliton spacing and the number of solitons in the related art have the problems of complex system structure, high cost, low regulation efficiency, poor precision, poor controllability, etc. In view of the problems existing in the related art, this application proposes a programmable generation system and method of soliton molecular laser to overcome the problems existing in the methods for regulating the soliton spacing and the number of solitons in the prior art.

[0040] Before describing the programmable generation system and method of soliton molecular laser in the present application, the technical terms that may be involved in the present application are explained.

[0041] 1. Soliton: It is a special form of ultrashort pulse whose shape, amplitude and speed remain unchanged during propagation.

[0042] 2. Soliton molecules: Solitons split into multiple molecules in a nonlinear environment and are bound together through a self-organization process to form new soliton states.

[0043] 3. Soliton spacing: the time domain spacing between adjacent solitons.

[0044] 4. Saturable absorber: It is an optical device made by utilizing the nonlinear optical saturable absorption effect of the material. Its transmittance is nonlinearly positively correlated with the intensity of the light pulse.

[0045] Next, the programmable generation system and method of soliton molecular laser in the present application are described in detail.

[0046] This application first provides a programmable generation system of soliton molecular lasers. Figure 1The schematic diagram of the structure of the programmable generation system of soliton molecular laser is shown in FIG. Figure 1 As shown, the programmable generation system of soliton molecular laser includes a pump source 101, a wavelength division multiplexer 102, a gain fiber 103, an output coupler 104, a polarization-independent isolator 105, a saturable absorber 106, a polarization controller 107, a bandpass filter 108 and a programmable optical controller 109 which are fused in sequence, and the output end pigtails of the programmable optical controller 109 are connected to the through end pigtails of the wavelength division multiplexer 102 to form a fiber ring laser resonant cavity.

[0047] Among them, the pump source 101, the wavelength division multiplexer 102, the gain fiber 103, the output coupler 104, the polarization-independent isolator 105, the saturable absorber 106, the polarization controller 107, the bandpass filter 108 and the programmable optical regulator 109 are connected in sequence by single-mode optical fibers, which can improve the robustness and stability of the programmable generation system and reduce the deviation caused by environmental influences when adjusting the soliton spacing and the number of solitons in the soliton molecule. In the embodiment of the present application, the working band of the single-mode optical fiber used to connect each optical component is the same as the gain band of the gain optical fiber 103. For example, when the gain optical fiber is an erbium-doped optical fiber, a single-mode optical fiber with an operating wavelength of 1550nm can be used to connect adjacent optical components.

[0048] In an exemplary embodiment of the present application, the pump source 101 may be a semiconductor laser for generating pump light, and the pump light enters the gain fiber 103 through the wavelength division multiplexer 102 for pumping, so as to excite the particles in the gain fiber 103 in a low energy state to a high energy state. In the embodiment of the present application, the type of the pump source 101 varies according to the type of the gain fiber. For example, when the gain fiber is an erbium-doped fiber or an ytterbium-doped fiber, a semiconductor laser in the 980nm band may be used as the pump source, and when the gain fiber is a thulium-doped fiber, a semiconductor laser in the 1550nm band may be used as the pump source.

[0049] In an exemplary embodiment of the present application, when the programmable generation system of the soliton molecular laser is in the soliton molecule cyclic oscillation stage, the wavelength division multiplexer 102 can simultaneously receive the pump light generated by the pump source 101 and the soliton molecules output by the programmable optical controller 109, and transmit the pump light and the soliton molecules to the gain fiber 103 at the same time. Under the action of the pump light, the particle layout inversion occurs in the gain fiber, and the soliton molecules are power-amplified by stimulated radiation to compensate for the soliton molecule energy loss caused by fiber loss and output coupler splitting. In an embodiment of the present application, the model of the wavelength division multiplexer 102 can be determined according to the working band of the pump source 101 and the central wavelength of the gain fiber 103. For example, when the pump source 101 is a semiconductor laser in the 980nm band and the gain fiber is an erbium-doped fiber, a 980 / 1550nm wavelength division multiplexer can be selected.

[0050] In an exemplary embodiment of the present application, the output coupler 104 can divide the amplified soliton molecules outputted from the gain fiber 103 into circulating soliton molecules and output soliton molecules according to a preset output coupling ratio, wherein the circulating soliton molecules continue to remain in the fiber ring laser resonator to maintain laser operation, and the output soliton molecules are outputted through the coupling port for measurement and application. The preset output coupling ratio is the ratio of output power to circulating power, and the preset output coupling ratio can be specifically set according to the compensation capability of the pump source 101. When the compensation capability of the pump source 101 is high, the output power ratio can be increased, for example, the preset output coupling ratio is set to 50:50, 60:40, 70:30, etc. When the compensation capability of the pump source is low, the circulating power ratio can be increased, for example, the preset output coupling ratio is set to 10:90, 20:80, 30:70, etc.

[0051] In an exemplary embodiment of the present application, the input end pigtail of the polarization-independent isolator 105 is fused with the straight-through end pigtail of the output coupler 104, and the output end pigtail is fused with the input end pigtail of the saturable absorber 106, so as to unidirectionally transmit the received circulating soliton molecules to the saturable absorber 106 to improve system stability.

[0052] After receiving the circulating soliton molecules, the saturable absorber 106 can modulate the intensity of the circulating soliton molecules based on the nonlinear optical saturable absorption effect to suppress the background noise in the fiber ring laser resonator and stabilize the soliton molecules; then the polarization controller 107 squeezes the optical fiber to optimize the polarization state and loss of the soliton molecules to achieve stable output of the soliton molecules.

[0053] In an exemplary embodiment of the present application, the saturable absorber 106 may be a semiconductor saturable absorber or a nanomaterial having nonlinear optical saturable absorption characteristics, wherein the semiconductor saturable absorber may be a transmissive semiconductor saturable absorber or a reflective semiconductor saturable absorber, and the nanomaterial having nonlinear optical saturable absorption characteristics may be, for example, a carbon nanotube-based film, a graphene-based film, or a film made of other two-dimensional materials having nonlinear optical saturable absorption characteristics, etc., and the embodiments of the present application do not specifically limit this. The polarization controller 107 can be a squeezed fiber polarization controller or a three-ring fiber polarization controller. When the polarization controller 107 is a squeezed fiber polarization controller, the shape of the fiber at the squeezed position can be changed by squeezing the fiber, thereby optimizing the polarization state and loss of the circulating signal light passing through the polarization controller 107. For example, the cross-section of a conventional optical fiber is circular. By squeezing the optical fiber, the cross-section can be squeezed into an elliptical shape, so that the polarization state of the circulating signal light passing through is changed, and the loss of the circulating soliton molecules is changed, thereby achieving stable output of the soliton molecules. When the polarization controller 107 is a three-ring fiber polarization controller, the polarization state and loss of the circulating soliton molecules passing through the polarization controller 107 can be optimized by changing the shape of the optical fiber.

[0054] In an exemplary embodiment of the present application, since there are disturbances in the programmable generation system of the soliton molecule laser, such as periodic gain, loss, environmental interference, etc., dispersive waves are inevitably generated in the fiber ring laser resonator. Under the influence of the dispersive waves, the soliton molecules will produce oscillation tails in the time domain, and the oscillation tails will significantly change the soliton spacing in the soliton molecules, resulting in the failure of the programmable optical controller to adjust the soliton spacing. Therefore, it is necessary to filter out the dispersive waves to ensure the stability of the adjustment of the soliton spacing. In an embodiment of the present application, a bandpass filter 108 can be set after the polarization controller 107, and the dispersive waves carried by the soliton molecules output by the polarization controller 107 are filtered out by the bandpass filter 108 to eliminate the oscillation tails of the soliton molecules in the time domain, thereby ensuring the stability of the programmable optical controller 109 in adjusting the soliton spacing and obtaining soliton molecules with stable time domain spacing. In the embodiment of the present application, the operating band of the bandpass filter 108 corresponds to the gain band of the gain fiber. For example, when the gain fiber is an erbium-doped fiber, the operating band of the bandpass filter may be 1537 nm to 1549 nm.

[0055] It is worth noting that in the initial stage of the programmable generation system, soliton molecules are not generated immediately. Soliton molecules can only be generated when the light oscillates multiple times in the fiber ring laser resonator, achieves stable passive mode locking under the action of the saturable absorber, and the pump power of the pump source is greater than or equal to the preset power threshold. Among them, the preset power threshold is the minimum power value required to achieve soliton splitting and bind together through self-organization to form soliton molecules. Since the purpose of this application is to controllably adjust the soliton spacing and the number of solitons in the soliton molecules, the solution of the embodiment of this application is aimed at the soliton pulses generated when the programmable generation system achieves stable passive mode locking, and it is also necessary to ensure that the pump power is greater than or equal to the preset power threshold to provide the required energy for the generation of soliton molecules.

[0056] In an exemplary embodiment of the present application, the programmable optical controller 109 can transfer energy to the solitons circulating in the fiber ring laser resonator according to a pre-written frequency phase function, generate a main pulse and a sub-pulse with a preset time domain interval from the main pulse, and under the condition that the pump power is greater than or equal to the preset power threshold, the main pulse and the sub-pulse can form a soliton molecule containing multiple solitons after entering the fiber ring laser resonator for multiple rounds of circulation. Among them, the energy transfer of the soliton is essentially the pulse splitting of the soliton, the energy of the main pulse generated by the splitting is lower than the energy of the soliton, and the energy of the sub-pulse is lower than the energy of the main pulse; for example, if the energy of the soliton is 1, through energy transfer, the energy of the main pulse generated may be 0.9, the energy of the sub-pulse may be 0.1, and so on. Next, the structure and working principle of the programmable optical controller 109 are explained.

[0057] Figure 2 The architecture diagram of the programmable light controller is shown in FIG. Figure 2 As shown, the programmable optical controller 109 includes a first collimating lens 201, a diffraction grating 202, a cylindrical mirror 203, a spatial light modulator 204 and a second collimating lens 205, wherein the first collimating lens 201 is fused with the output end pigtail of the bandpass filter 108, and the second collimating lens 205 is fused with the through end pigtail of the wavelength division multiplexer 102. It is worth noting that Figure 2 The straight lines between the components in the programmable light controller 109 are spatial light paths, not connecting components.

[0058] In the programmable optical controller 109, the transmission path of the solitons and the adjustment principle of the soliton spacing are as follows: the first collimating lens 201 collimates the solitons output by the bandpass filter 108 and incidents them to the diffraction grating 202 along the optical path L1, and the diffraction grating 202 performs spectral decomposition on the incident solitons to form a plurality of incident lights with different frequencies; the diffraction grating 202 emits the generated incident light along the optical path L2 to the cylindrical mirror 203, and the incident light is reflected to the liquid crystal spatial light modulator 204 along the optical path L3 through the cylindrical mirror 203; the liquid crystal spatial light modulator 204 modulates the incident light according to the phase in the pre-written frequency phase function. The phase of multiple incident lights with different frequencies is adjusted according to the bit period to generate multiple outgoing lights with different frequencies and different phases, and the outgoing lights are emitted along the optical path L4 to the cylindrical mirror 203; the cylindrical mirror 203 reflects the outgoing light along the optical path L5 to the diffraction grating 202; the diffraction grating 202 performs spectral synthesis on the received outgoing light to generate a main pulse and a sub-pulse with a preset time domain spacing from the main pulse, and emits it along the optical path L6 to the second collimating lens 205; the second collimating lens 205 collimates the main pulse and the sub-pulse and inputs them to the wavelength division multiplexer 102 for circulation.

[0059] In an exemplary embodiment of the present application, the preset time domain spacing between the main pulse and the sub-pulse is determined by the phase period in the frequency phase function. Specifically, the time domain spacing between the main pulse and the sub-pulse is reciprocal to the phase period, that is, the soliton spacing = 1 / phase period. When the main pulse and the sub-pulse enter the fiber ring laser resonator for circulation, since the pump power is greater than or equal to the minimum power value for generating soliton molecules, the energy of the main pulse and the sub-pulse will increase in each cycle under the amplification effect of the gain fiber and the intensity modulation effect of the saturable absorber. After multiple cycles, the energy of the main pulse and the sub-pulse reaches the energy of the soliton, and the main pulse and the sub-pulse are transformed into solitons, thereby forming soliton molecules containing multiple solitons.

[0060] In an exemplary embodiment of the present application, a liquid crystal spatial light modulator is connected to a computer device with an external device. Before starting the programmable generation system of the soliton molecular laser, the user can write a frequency phase function in the computer device based on a computer language (MATLAB, etc.), and write the written frequency phase function into the liquid crystal spatial light modulator through the computer device. By changing the phase period, the spacing between solitons in the soliton molecule can be changed; then the programmable generation system of the soliton molecular laser is started, and an external voltage is applied to the liquid crystal spatial light modulator, so that the liquid crystal unit in the liquid crystal spatial light modulator adjusts the phase of the incident light of different frequencies according to the phase period in the frequency phase function, thereby changing the spacing between solitons in the soliton molecule. In an embodiment of the present application, the phase period can take any value in an interval greater than zero, and the maximum value of the interval is determined by the resolution of the liquid crystal spatial light modulator and the size of the light response area.

[0061] In an exemplary embodiment of the present application, the light response region of the liquid crystal spatial light modulator is composed of a plurality of liquid crystal regions, each of which contains a plurality of liquid crystal molecules, and different liquid crystal regions can receive incident light of different frequencies. Since the control circuits of the liquid crystal regions are independent of each other, different voltages can be applied to different liquid crystal regions in the liquid crystal spatial light modulator based on the frequency phase function, and the spatial orientation of the liquid crystal molecules is changed by different voltages, so that the incident light of different frequencies produces a time delay when passing through different liquid crystal regions, thereby realizing the phase regulation of the incident light of different frequencies. According to the Taylor expansion relationship of the phase in the frequency domain, the time delay is equal to the derivative of the phase with respect to the frequency, and the phase is equal to the integral of the time delay with respect to the frequency. Therefore, the voltage value applied to different liquid crystal regions can be determined according to the size of the phase period in the frequency phase function, so that the incident light of different frequencies produces the expected time delay, thereby realizing the frequency-phase regulation of the incident light spectrum, and then realizing the precise regulation of the soliton spacing in the soliton molecule.

[0062] Since the phase period in the frequency phase function in the present application can be artificially controlled, the user can adjust the phase period in the frequency phase function according to actual needs to adjust the soliton spacing in the soliton molecule. This also shows that the programmable generation system of the soliton molecular laser in the present application can achieve precise and on-demand adjustment of the soliton spacing in the soliton molecule.

[0063] In an exemplary embodiment of the present application, the number of solitons in the generated soliton molecule is affected by the pump power. Although multiple solitons will generate new main pulses and sub-pulses after being processed by the programmable optical controller, if the pump power is low and insufficient to maintain the conversion of all pulses into soliton pulses, the sub-pulses will be lost during the cycle. For example, when the pump power is 40 mW, it can support the generation of two solitons in the cavity. Even if the number of main pulses and sub-pulses generated by the programmable optical controller is more than two, the energy in the fiber ring laser resonant cavity can only ensure that two pulses are converted into solitons. Only when the pump power is further increased can other pulses be supplemented with energy and converted into new solitons. That is to say, in the embodiment of the present application, it is necessary to adjust the number of solitons in the soliton molecule by regulating the pump power, and the number of solitons increases with the increase of the pump power.

[0064] Further, when increasing the pump power of the pump source, it can be increased according to a preset power interval, for example, the pump power can be increased at intervals of 5 mW, and of course it can also be increased according to other power intervals, which is not specifically limited in the embodiments of the present application. In the embodiments of the present application, there is no order of precedence for adjusting the number of solitons and the soliton spacing in the soliton molecule, and the user can adjust the number of solitons and / or the soliton spacing according to actual needs. When the frequency-phase function remains unchanged, the pump power of the pump source can be increased to increase the number of solitons in the soliton molecule. When the pump power of the pump source remains unchanged, the phase period in the frequency-phase function can be adjusted to change the soliton spacing in the soliton molecule; of course, only the soliton spacing or only the number of solitons can be adjusted, which is not specifically limited in the embodiments of the present application.

[0065] In order to make the technical solution of the present application clearer, the following takes the initial stable mode locking of a fiber ring laser resonator, and the pump power is the minimum power value required to generate soliton molecules as an example to illustrate the technical solution of the programmable optical controller in the present application for adjusting the soliton spacing in the soliton molecule.

[0066] Figure 3 The schematic diagram shows the process flow of generating a soliton molecule containing two solitons, as shown in FIG. Figure 3 As shown in the figure, when the fiber ring laser resonator first achieves a stable mode-locking state, a soliton O1 can be output through a bandpass filter. After the soliton O1 enters the programmable optical controller, it is sequentially spectrally decomposed by a diffraction grating to form multiple incident lights of different frequencies, the incident light is reflected by a cylindrical mirror, the liquid crystal spatial light modulator applies a phase period v to the incident light of different frequencies according to the frequency phase function to form an output light with different frequencies and different phases, the output light is reflected by a cylindrical mirror, and the diffraction grating performs spectral synthesis to form a main pulse P1 and a sub-pulse C1 with a time domain spacing of 1 / v from the main pulse. The main pulse P1 and the sub-pulse C1 enter the fiber ring laser resonator and circulate, and after multiple rounds of circulation, two solitons O1 and O2 are generated.

[0067] When solitons O1 and O2 enter the programmable optical controller, soliton O1 will generate a main pulse P2 and a sub-pulse C2 with a 1 / v interval from the main pulse P2 under the action of the frequency phase function, and soliton O2 will generate a main pulse P3 and a sub-pulse C3 with a 1 / v interval from the main pulse P3 under the action of the frequency phase function, wherein the main pulse P2 has the same time domain position as the soliton O1, and the main pulse P3 has the same time domain position as the soliton O2. Since the phase period is the same, the sub-pulse C2 and the main pulse P3 have the same time domain position. When the main pulses P2, P3 and the sub-pulses C2, C3 circulate in the cavity, since the pump power is the minimum power value required to generate soliton molecules, only the main pulses P2 and P3 in the cavity are transformed into solitons, while the sub-pulse C3 cannot be transformed into a soliton and is lost.

[0068] Figure 4 The schematic diagram shows the process of increasing the pump power to adjust the number of solitons in the soliton molecule, as shown in Figure 4 As shown, the frequency-phase function remains unchanged. Figure 3 When the corresponding pump power increases to a power value that can generate three solitons, after multiple cycles, not only the energy of the main pulses P2 and P3 increases and transforms into solitons O1 and O2, but the energy of the sub-pulse C3 also increases and transforms into soliton O3, and a soliton molecule containing three solitons with equal spacing is generated in the cavity.

[0069] As the cycle proceeds, by continuously increasing the pump power, 4, 5... or even more solitons will be generated, and then a soliton molecule containing multiple solitons arranged at equal intervals will be obtained.

[0070] It is worth mentioning that Figure 3 and Figure 4 In this paper, the energy of solitons, main pulses and sub-pulses is characterized by pulse amplitude.

[0071] The present application also provides a programmable generation method of a soliton molecular laser, which is implemented based on the programmable generation system of the soliton molecular laser. Figure 5 The flowchart of the programmable generation method of soliton molecular laser is schematically shown as follows: Figure 5 As shown, the process at least includes steps S501-S503:

[0072] Step S501: when the fiber ring laser resonator achieves a stable mode-locked state, the soliton output by the bandpass filter is energy transferred by the programmable optical controller according to the phase period in the pre-written frequency-phase function to generate a main pulse and a sub-pulse spaced from the main pulse by a preset time domain interval;

[0073] Step S502: inputting the main pulse and the sub-pulse into the fiber ring laser resonator through the wavelength division multiplexer for multiple cycles to generate the soliton molecules;

[0074] Step S503: filtering the dispersive waves carried by the soliton molecules through the bandpass filter to obtain soliton molecules with stable time domain spacing.

[0075] Next, based on Figure 1 The schematic diagram of the architecture of the programmable generation system of the soliton molecular laser shown in the figure provides a detailed description of the programmable generation method of the soliton molecular laser in the embodiment of the present application.

[0076] In step S501, when the fiber ring laser resonator achieves a stable mode-locked state, the soliton output by the bandpass filter is energy transferred by the programmable optical controller according to the phase period in the pre-written frequency-phase function to generate a main pulse and a sub-pulse spaced from the main pulse by a preset time domain spacing.

[0077] In the exemplary embodiment of the present application, a soliton is an ultrashort pulse, and an important condition for the formation of a soliton is that the laser is in a stable mode-locked state; a soliton molecule is a soliton split into multiple parts in a nonlinear environment, and a new soliton state is formed by binding together through a self-organization process, and the soliton splitting depends on the pump power of the pump source. Therefore, in order to achieve the regulation of the soliton spacing and the number of solitons in the soliton molecule, it is necessary to first generate solitons, and then generate soliton molecules based on the solitons. Then, it is necessary to ensure that the fiber ring laser resonator is in a stable mode-locked state, and the pump power of the pump source is greater than or equal to the minimum pump power for generating soliton molecules. The minimum pump power depends on the loss of the laser resonator. For example, the minimum pump power corresponding to the programmable generation system of the soliton molecule laser in the embodiment of the present application is 40mW. Of course, for systems with different gain fibers, the minimum pump power is different, and the embodiment of the present application does not make specific limitations on this.

[0078] In an exemplary embodiment of the present application, when the fiber ring laser resonator first achieves a stable mode-locked state, the polarization controller can output a soliton, and the soliton can enter the programmable optical controller through a bandpass filter. The programmable optical controller can transfer energy to the soliton according to a phase period in a pre-written frequency-phase function, generating a main pulse and a sub-pulse separated from the main pulse by a preset time domain spacing; the main pulse and the sub-pulse are transformed into solitons after multiple cycles in the fiber ring laser resonator, generating a soliton molecule containing two solitons.

[0079] Furthermore, as the pump power increases, each soliton in the soliton molecule continues to transfer energy through the programmable optical controller, generating a new main pulse and a sub-pulse with a preset time domain interval from the corresponding main pulse. These main pulses and sub-pulses are also transformed into solitons after multiple cycles in the cavity, thereby obtaining soliton molecules containing more solitons. By continuously cycling and increasing the pump power, soliton molecules with the required number of solitons can be obtained, and even soliton molecules with solitons filling the entire fiber ring laser resonant cavity can be obtained.

[0080] In an exemplary embodiment of the present application, a programmable light controller includes a first collimating lens, a diffraction grating, a cylindrical mirror, a liquid crystal spatial light modulator, and a second collimating lens. Figure 6 The schematic diagram shows the process flow of energy transfer of solitons by a programmable optical controller, such as Figure 6 As shown:

[0081] In step S601, the solitons are collimated and input into the diffraction grating through a first collimating lens for spectral decomposition to form a plurality of incident lights of different frequencies.

[0082] In an exemplary embodiment of the present application, the first collimating lens is fused with the output tail fiber of the bandpass filter, and the first collimating lens can collimate the solitons output by the bandpass filter so that they are incident on the diffraction grating corresponding to the first collimating lens. After receiving the solitons, the diffraction grating can perform spectral decomposition on them and generate multiple incident lights with different frequencies in space.

[0083] In step S602, the incident light emitted by the diffraction grating is reflected to the liquid crystal spatial light modulator by a cylindrical mirror, so that the liquid crystal spatial light modulator modulates the incident light according to the phase period in the frequency-phase function to form output light with different phases and different frequencies.

[0084] In an exemplary embodiment of the present application, the diffraction grating transmits multiple incident lights of different frequencies to the cylindrical mirror. After receiving the incident light, the cylindrical mirror can reflect the incident light to the light response area of ​​the liquid crystal spatial light modulator to perform phase modulation. In the embodiment of the present application, the cylindrical mirror can be any type of cylindrical mirror, for example, it can be a plano-convex cylindrical lens, a plano-concave cylindrical lens, a bi-convex cylindrical lens, a bi-concave cylinder, a meniscus cylindrical mirror, a cylindrical cross-cylindrical mirror, a special-shaped cylindrical lens, etc. The embodiment of the present application does not specifically limit this, as long as it can reflect the incident light to the liquid crystal spatial light modulator.

[0085] In an exemplary embodiment of the present application, when the cylindrical mirror reflects incident light of different frequencies to the liquid crystal spatial light modulator, the incident light of different frequencies will be incident on different liquid crystal areas. Since the control circuits of each liquid crystal area are independent of each other, different external voltages can be applied to each liquid crystal area according to the phase period in the frequency-phase function pre-written in the liquid crystal spatial light modulator, so that the liquid crystal molecules in each liquid crystal area have different spatial orientations. When the incident light of each frequency passes through the liquid crystal layer of each liquid crystal area, a time delay will occur. The time delay causes the phase to change, thereby generating output light with different frequencies and different phases.

[0086] Since the phase is related to the soliton spacing, the soliton spacing in the soliton molecule can be adjusted under the action of the liquid crystal spatial light modulator and the frequency phase function. In addition, since the phase period in the frequency phase function can be updated according to actual needs, the soliton spacing in the soliton molecule can be adjusted on demand.

[0087] In step S603, the outgoing light emitted by the liquid crystal spatial light modulator is reflected to the diffraction grating through a cylindrical mirror for spectrum synthesis to form a main pulse and a sub-pulse.

[0088] In an exemplary embodiment of the present application, the liquid crystal spatial light modulator can emit the outgoing light to the cylindrical mirror, and after the cylindrical mirror receives the outgoing light, it reflects it to the diffraction grating. Since the outgoing light contains a plurality of signal lights of different frequencies and phases, the diffraction grating can perform spectral synthesis on them after receiving all the outgoing lights to form a main pulse and a sub-pulse with a preset time domain spacing from the main pulse, and the preset time domain spacing is the reciprocal of the phase period used by the liquid crystal spatial light modulator when performing phase modulation on the incident light.

[0089] In step S604, the main pulse and the sub-pulse are collimated and input into the wavelength division multiplexer through a second collimating lens.

[0090] In an exemplary embodiment of the present application, after the diffraction grating performs spectral synthesis on the incident light to form a main pulse and a sub-pulse, it can be emitted to a second collimating lens and collimated through the second collimating lens to be input to a wavelength division multiplexer for circulation and generation of soliton molecules.

[0091] It is worth noting that no matter the number of solitons circulating in the cavity is one or more, the programmable optical controller has the same processing method for each soliton. As for whether the new sub-pulse generated by energy migration can be transformed into a soliton during the circulation process, it depends on whether the pump power of the pump source can support it to obtain enough energy to be transformed into a soliton. In the embodiment of the present application, the number of solitons in the soliton molecule can be increased by increasing the pump power of the pump source. When adjusting the pump power, it can be adjusted according to a preset power interval, and the preset power interval can be, for example, 5 mW, etc., which is not specifically limited in the embodiment of the present application.

[0092] In step S502, the main pulse and the sub-pulse are input into the fiber ring laser resonator through the wavelength division multiplexer for multiple cycles to generate soliton molecules.

[0093] In an exemplary embodiment of the present application, after the main pulse and the sub-pulse enter the fiber ring laser resonator through the wavelength division multiplexer, they begin to circulate in the cavity. Under the premise of ensuring the pump power, through continuous circulation, the energy of the main pulse and the sub-pulse continues to increase and transform into solitons, thereby generating soliton molecules containing multiple solitons. However, when the pump power cannot guarantee the energy of the main pulse and the sub-pulse to transform into solitons, the pulse will be consumed as the cycle proceeds.

[0094] In step S503, the dispersion waves carried by the soliton molecules are filtered out by the bandpass filter to obtain soliton molecules with stable time domain spacing.

[0095] In an exemplary embodiment of the present application, due to the presence of disturbances in the fiber ring laser resonator, such as periodic gain, loss, environmental interference, etc., dispersive waves are inevitably generated in the resonator. Affected by the dispersive waves, the soliton molecules will produce oscillation tails in the time domain, and this oscillation tail will significantly change the spacing between solitons in the soliton molecules, thereby rendering the frequency and phase regulation of the soliton spacing by the programmable optical controller ineffective. Therefore, a bandpass filter can be set before the programmable optical controller, and the dispersive waves carried by the soliton molecules can be filtered out by the bandpass filter to eliminate the oscillation tails of the soliton molecules in the time domain, so as to ensure the adjustment accuracy and reliability of the programmable optical controller on the soliton spacing in the soliton molecules, and obtain soliton molecules with stable time domain spacing.

[0096] In an exemplary embodiment of the present application, when adjusting the soliton spacing, there is no need to interrupt the operation of the system. It is only necessary to update the phase period in the frequency-phase function in the computer device. The system can then adjust the soliton spacing in the soliton molecules according to the updated frequency-phase function, further improving the efficiency and controllability of the soliton spacing adjustment.

[0097] The programmable generation method of the soliton molecular laser in the embodiment of the present application, on the one hand, when adjusting the soliton spacing in the soliton molecule, the bandpass filter and the programmable optical controller cooperate with each other, the soliton spacing is adjusted based on the frequency phase function by the programmable optical controller, and then the dispersion wave carried by the soliton molecule is eliminated by the bandpass filter, thereby improving the accuracy, stability and controllability of the soliton spacing adjustment; on the other hand, when adjusting the soliton spacing, it is only necessary to adjust the phase period in the frequency phase function written into the liquid crystal spatial light modulator, thereby avoiding the adjustment of parameters such as cavity loss, dispersion, birefringence, gain, etc., thereby reducing the difficulty of adjusting the soliton spacing and improving the efficiency of adjusting the soliton spacing; on the other hand, since the phase period can be set according to actual needs, the soliton spacing in the soliton molecular laser can be accurately adjusted on demand. In summary, the method for generating soliton molecular lasers in the present application is a highly customized and environmentally resistant soliton molecular laser programmable generation method.

[0098] In order to make the technical solution of the present application clearer, the programmable generation method of the soliton molecular laser in the present application is described below with a specific embodiment.

[0099] A programmable generation system of soliton molecular laser is formed by using a 980nm semiconductor laser, a 980 / 1550nm wavelength division multiplexer, an erbium-doped fiber, a 9 / 1 output coupler, a polarization-independent isolator, a carbon nanotube saturable absorber, a polarization controller, a bandpass filter, a first collimating lens, a diffraction grating, a cylindrical mirror, a liquid crystal spatial light modulator, a second collimating lens and a single-mode fiber. At the same time, the liquid crystal spatial light modulator is connected to a computer device for writing a frequency phase function into the liquid crystal spatial light modulator. In the system, the central wavelength of the single-mode fiber is 1550nm and the length is 9.2m. The length of the erbium-doped fiber is 6m. The working wavelength of the bandpass filter is 1537nm-1549nm. The equivalent optical path of the programmable light controller composed of the first collimating lens, the diffraction grating, the cylindrical mirror, the liquid crystal spatial light modulator and the second collimating lens is 3.7m. The total cavity length of the system is 18.9m, and the net cavity dispersion is -0.52ps. 2 .

[0100] First, the frequency phase function p(v) is written into the liquid crystal spatial light modulator through MATLAB programming, and the phase period v takes values ​​in [0.015THz, 0.333THz]. Then, the pump power of the pump source is adjusted to 40mW to generate 980nm pump light, which is input into the erbium-doped fiber through a wavelength division multiplexer for stimulated emission amplification to form a 1550nm laser. The laser passes through a 9 / 1 output coupler, 90% of the laser remains in the fiber ring cavity as a circulating signal light, and 10% of the laser is output through the output end pigtail for measurement and application. Then, the circulating signal light propagates unidirectionally to the carbon nanotube saturable absorber through a polarization-independent isolator, and the circulating signal light is intensity modulated based on the nonlinear saturable absorption effect, and the polarization state and loss of the circulating signal light output by the saturable absorber are optimized through a polarization controller. Then, the bandpass filter filters out the dispersion wave in the cavity. Finally, it returns to the wavelength division multiplexer through the first collimating lens, diffraction grating, cylindrical mirror, liquid crystal spatial light modulator and the second collimating lens. By continuously repeating the above process in the fiber ring laser resonator until a stable mode-locked state is achieved, the polarization controller can output solitons, which enter the programmable optical controller through a bandpass filter. The programmable optical controller performs energy migration on the solitons according to the phase period in the pre-written frequency phase function, generating a main pulse and a sub-pulse with a preset time domain interval from the main pulse. The main pulse and the sub-pulse enter the fiber ring laser resonator through the wavelength division multiplexer for circulation. After multiple rounds of circulation, a soliton molecule containing two solitons is generated, such as Figure 3As shown. Then, the bandpass filter filters out the dispersive wave carried by the soliton molecule to eliminate its oscillation tail in the time domain, ensuring the effectiveness of the programmable optical controller in regulating the soliton spacing in the soliton molecule. The soliton molecule continues to enter the programmable optical controller, through which the programmable optical controller sequentially performs energy migration on the two solitons to generate a main pulse corresponding to each soliton and a sub-pulse with a preset time domain spacing, wherein the time domain position of the first sub-pulse is the same as the second main pulse, as shown in FIG. Figure 4 As shown, these main pulses and sub-pulses enter the cavity for circulation, and by increasing the pump power to 45 mW, soliton molecules containing 3 solitons are generated in the cavity; the above process is repeated continuously to cascade generate soliton molecules containing more solitons.

[0101] Figure 7 The autocorrelation diagram of the soliton molecule at different phase periods is shown when the pump power is 40mW. Figure 7 As shown, the autocorrelation diagram shows 5 autocorrelation curves A, B, C, D, and E corresponding to different phase periods. Each curve has a three-peak structure, indicating that soliton molecules are generated at this time. The soliton spacing in curve A is 3.1ps, and the corresponding phase period is 1 / 3.1THz; the soliton spacing in curve B is 12.2ps, and the corresponding phase period is 1 / 12.2 THz; the soliton spacing in curve C is 26.9ps, and the corresponding phase period is 1 / 26.9 THz; the soliton spacing in curve D is 42.5ps, and the corresponding phase period is 1 / 42.5 THz; the soliton spacing in curve E is 66.5ps, and the corresponding phase period is 1 / 66.5 THz. From Figure 6 It can be found that as the phase period changes, the soliton spacing changes, but the intensities of the three peaks maintain a 1:2:1 relationship, indicating that the intensities of the two solitons in the soliton molecule are the same.

[0102] Figure 8 Shown with Figure 7 The corresponding spectrum is Figure 8 As shown, the spectrum diagram shows spectrum diagrams a, b, c, d, and e corresponding to autocorrelation curves A, B, C, D, and E. The autocorrelation curve shows the time domain information, and the spectrum diagram shows the frequency domain information. Since the soliton spacing corresponding to the autocorrelation curves A, B, C, D, and E changes from small to large, the spectrum curves in the spectrum diagrams a, b, c, d, and e change from sparse to dense.

[0103] Fig. 9 The relationship between the actual soliton spacing and the theoretical soliton spacing determined based on the phase period is shown, as Fig. 9As shown, the change trend of the points corresponding to the actual soliton spacing is consistent with the change trend of the curve corresponding to the theoretical soliton spacing, indicating that the programmable generation system of the soliton molecular laser in the present application can accurately adjust the soliton spacing in the soliton molecule.

[0104] In an exemplary embodiment of the present application, the number of solitons in a soliton molecule can be adjusted by adjusting the pump power while the frequency-phase function remains unchanged.

[0105] Fig.10 The autocorrelation diagram of the soliton molecule at different pump powers when the phase period is 0.083 THz is shown. Fig.10 As shown, the autocorrelation diagram includes autocorrelation curves F, G, and H corresponding to three different pump powers, wherein curve F shows that when the pump power is 40 mW, the programmable generation system can output double soliton molecules with a soliton spacing of 12 ps; curve G shows that when the pump power is 45 mW, the programmable generation system can output triple soliton molecules with a soliton spacing of 12 ps; curve H shows that when the pump power is 50 mW, the programmable generation system can output quadruple soliton molecules with a soliton spacing of 12 ps.

[0106] Fig.11 Shown with Fig.10 The corresponding spectrum is Fig.11 As shown, the spectrum diagram shows spectrum diagrams f, g, and h corresponding to the autocorrelation curves F, G, and H. Relative to spectrum diagram f, a new peak appears between two adjacent peaks in spectrum diagram g, and relative to spectrum diagram f, two new peaks appear between two adjacent peaks in spectrum diagram h.

[0107] The programmable generation system of soliton molecular laser of the present application includes a pump source, a wavelength division multiplexer, a gain fiber, an output coupler, a polarization-independent isolator, a saturable absorber, a polarization controller, a bandpass filter and a programmable optical regulator. On the one hand, the bandpass filter can filter out dispersive waves, eliminate the oscillation tailing of soliton molecules in the time domain, prevent the oscillation tailing from changing the soliton spacing, and make the frequency phase control of the programmable optical controller invalid; at the same time, the programmable optical controller can adjust the soliton spacing in the soliton molecules according to the phase period in the frequency phase function written into the liquid crystal spatial light modulator, and the phase period can be set according to actual needs. Therefore, the present application can realize on-demand and precise adjustment of the soliton spacing in the soliton molecules, and at the same time, the number of solitons can be adjusted by adjusting the pump power of the pump source, thereby realizing programmable adjustment of the number of solitons; on the other hand, since there is no need to adjust the parameters such as cavity loss, dispersion, birefringence, gain, etc. in the optical fiber ring cavity, the difficulty of adjusting the soliton spacing and the number of solitons is reduced, and the adjustment efficiency and controllability are improved; on the other hand, the programmable generation system of the soliton molecular laser in the present application does not include an extra-cavity optical path, does not require the configuration of an artificial intelligence algorithm, the overall system architecture is simple, and the construction cost and maintenance cost are very low.

[0108] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art that are not disclosed in the present application. The specification and embodiments are to be regarded as exemplary only, and the true scope and spirit of the present application are indicated by the claims.

Claims

1. A programmable generation system of soliton molecular laser, characterized in that: include: A fiber ring laser resonator formed by a pump source, a wavelength division multiplexer, a gain fiber, an output coupler, a polarization-independent isolator, a saturable absorber, a polarization controller, a bandpass filter, and a programmable optical controller that are fused in sequence, wherein the output end pigtail of the programmable optical controller is fused with the through end pigtail of the wavelength division multiplexer; The programmable optical controller is used to transfer energy to the solitons circulating in the fiber ring laser resonator according to the phase period in the pre-written frequency phase function, to generate a main pulse and a sub-pulse spaced from the main pulse by a preset time domain spacing, wherein the main pulse and the sub-pulse form a soliton molecule containing a plurality of solitons after multiple rounds of circulation in the fiber ring laser resonator; the bandpass filter is used to filter out the dispersion waves carried by the soliton molecules to obtain soliton molecules with a stable time domain spacing; The programmable light controller comprises a first collimating lens, a diffraction grating, a cylindrical mirror, a liquid crystal spatial light modulator and a second collimating lens, wherein the first collimating lens is connected to the output end pigtail of the bandpass filter, the second collimating lens is connected to the through end pigtail of the wavelength division multiplexer, and the liquid crystal spatial light modulator is connected to a computer device, and the computer device is used to write the frequency phase function into the liquid crystal spatial light modulator; The first collimating lens is used to collimate the solitons output by the bandpass filter and input them into the diffraction grating; The diffraction grating is used to perform spectral decomposition on the soliton to form a plurality of incident lights of different frequencies, and send the incident lights of different frequencies to the cylindrical mirror, so that the cylindrical mirror reflects the incident lights of different frequencies to the liquid crystal spatial light modulator; The liquid crystal spatial light modulator is used to modulate the incident light of different frequencies according to the phase period, and send the incident light of different frequencies after phase modulation to the cylindrical mirror, so that the cylindrical mirror reflects the incident light of different frequencies after phase modulation to the diffraction grating for spectrum synthesis to form the main pulse and the sub-pulse; The second collimating lens is used to collimate the main pulse and the sub-pulse and input them into the wavelength division multiplexer, so that the main pulse and the sub-pulse enter the fiber ring laser resonator through the wavelength division multiplexer and form the soliton molecule after multiple rounds of circulation.

2. The programmable generation system of soliton molecular laser according to claim 1, characterized in that: The number of solitons in the soliton molecule increases as the pump power of the pump source increases.

3. The programmable generation system of soliton molecular laser according to claim 1, characterized in that: The wavelength division multiplexer is used to input the pump light output by the pump source and the soliton molecules output by the programmable light regulator into the gain optical fiber, so as to amplify the power of the soliton molecules under the action of the pump light to generate amplified soliton molecules; The output coupler is used to divide the amplified soliton molecules into circulating soliton molecules and output soliton molecules according to a preset output coupling ratio, and the output soliton molecules are output through the coupling port of the output coupler; The polarization-independent isolator is used to ensure unidirectional transmission of the circulating soliton molecules; The saturable absorber modulates the intensity of the circulating soliton molecules based on the nonlinear saturable absorption effect, suppresses the background noise in the fiber ring laser resonator, and stabilizes the soliton molecules; The polarization controller is used to optimize the polarization state and loss of the soliton molecules output by the saturable absorber.

4. The programmable generation system of soliton molecular laser according to claim 1, characterized in that: The pump source, the wavelength division multiplexer, the gain fiber, the output coupler, the polarization-independent isolator, the saturable absorber, the polarization controller, the bandpass filter, the first collimating lens, and the second collimating lens are connected by single-mode fiber fusion splicing, and the working band of the single-mode fiber is the same as the gain band of the gain fiber.

5. A method for programmable generation of soliton molecular laser, applied to the programmable generation system of soliton molecular laser as claimed in any one of claims 1 to 4, characterized in that: include: When the fiber ring laser resonator achieves a stable mode-locked state, the solitons output by the bandpass filter are energy-transferred by the programmable optical controller according to the phase period in the frequency-phase function to generate a main pulse and a sub-pulse spaced from the main pulse by a preset time domain interval; Inputting the main pulse and the sub-pulse into the fiber ring laser resonator through the wavelength division multiplexer for multiple cycles to generate the soliton molecule; The dispersion waves carried by the soliton molecules are filtered out by the bandpass filter to obtain soliton molecules with stable time domain spacing; Wherein, the programmable light controller comprises a first collimating lens, a diffraction grating, a cylindrical mirror, a liquid crystal spatial light modulator and a second collimating lens; The step of transferring energy of the solitons output by the bandpass filter according to the phase period in the frequency-phase function by the programmable optical controller to generate a main pulse and a sub-pulse spaced from the main pulse by a preset time domain interval comprises: The soliton is collimated and input into the diffraction grating through the first collimating lens for spectral decomposition to form a plurality of incident lights with different frequencies; Reflecting the incident light emitted by the diffraction grating to the liquid crystal spatial light modulator through the cylindrical mirror, so that the liquid crystal spatial light modulator modulates the incident light according to the phase period to form outgoing light with different phases and different frequencies; Reflecting the outgoing light emitted by the liquid crystal spatial light modulator to the diffraction grating through the cylindrical mirror for spectrum synthesis to form the main pulse and the sub-pulse; The main pulse and the sub-pulse are collimated by the second collimating lens and input to the wavelength division multiplexer.

6. The programmable generation method of soliton molecular laser according to claim 5, characterized in that: The liquid crystal spatial light modulator comprises a plurality of liquid crystal regions, and different frequency components of the incident light correspond to different liquid crystal regions; The liquid crystal spatial light modulator modulates the incident light according to the phase period to form outgoing light with different phases and different frequencies, including: Determining an applied voltage corresponding to each of the liquid crystal regions according to the phase period; The external voltage is applied to each of the liquid crystal regions to change the spatial orientation of the liquid crystal molecules in each of the liquid crystal regions, and the phase of the incident light incident to each of the liquid crystal regions is adjusted based on the different spatial orientations of the liquid crystal molecules to generate the output light.

7. The programmable generation method of soliton molecular laser according to any one of claims 5-6, characterized in that: The method further comprises: When the frequency-phase function remains unchanged, increasing the pump power of the pump source to increase the number of solitons in the soliton molecule; or When the pump power of the pump source remains unchanged, the phase period in the frequency-phase function is adjusted to change the soliton spacing in the soliton molecule.

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