Coherent optical signal generation and conversion system and method based on stimulated radiation

Abstract

The invention provides a coherent optical signal generation and conversion system and method based on stimulated radiation, and the system comprises a pump light preparation and target information modulation module with an incoherent characteristic, a probe light field preparation module, a stimulated radiation substance stimulated radiation optical signal generation module, and a coherent stimulated radiation optical signal processing module. And a signal triggering and synchronous control module. The pump light preparation and target information modulation module with the incoherent characteristic is used for generating pump light which carries modulation information and has the incoherent characteristic, the pump light irradiates a stimulated radiation substance to generate an excitation effect, and carried target information is loaded to the stimulated radiation substance; the probe light field preparation module is used for stimulating stimulated radiation substances in an excited state; according to the invention, the problems of incoherent light are effectively solved, the coherence characteristic of stimulated radiation optical signals is fully utilized in the fields of optical imaging, optical information transmission, quantum information processing, biomedicine and the like, and the bottleneck of the existing optical field is broken through.

Description

Technical Field

[0001] The present invention belongs to the field of information optics, and in particular relates to a system and method for generating and converting coherent optical signals based on stimulated radiation. Background Art

[0002] The stimulated radiation phenomenon states that when a luminescent particle in an excited state transitions to a low-energy state or ground state under the stimulation of an external radiation field, the frequency, phase, propagation direction and polarization state of the emitted photons are exactly the same as those of the probe photons.

[0003] The most important difference between stimulated radiation and spontaneous radiation of excited particles is that stimulated radiation photons have the characteristic of coherence. Spontaneous radiation is a spontaneous process of atoms when they are not controlled by external radiation fields. The phase of the spontaneous radiation field of a large number of atoms is incoherent, and the propagation direction and polarization state of the radiation field are also irregularly distributed. Stimulated radiation is a luminescence process under the control of an external probe field. Therefore, the frequency, phase, propagation direction and polarization state of the stimulated radiation field are exactly the same as those of the external radiation field.

[0004] The invention of laser is the most important application of the principle of stimulated emission of radiation, and the stimulated emission of radiation process is a necessary condition for the generation of laser. More importantly, in recent years, stimulated emission of radiation has gradually demonstrated its unique value in the field of biomedical imaging. Stimulated emission of radiation can provide new ways and methods for the observation of non-fluorescent samples. The stimulated emission of radiation (STED) technology that combines stimulated emission and fluorescence processes can break through the diffraction limit and achieve super-resolution microscopic imaging.

[0005] In the process of interaction between samples such as biological cells or proteins and optical signals, the coherence properties of optical signals are often extremely important, such as Fourier stack coherent imaging (FPM) technology in the field of imaging, coherent signal processing in the field of optical information, and quantum computing and entangled photon preparation in the field of quantum information. Due to the lack of correlation between photons in incoherent light fields, there is no clear description of the relationship between photons in the light field, which makes traditional incoherent imaging methods face many challenges in practical applications. For example, in order to obtain the spatial distribution of photons in a scene, only single-point acquisition and scanning and splicing imaging methods can be used, which has low acquisition efficiency and poor imaging quality. In imaging based on stimulated emission signals, only the incremental process of stimulated emission on photon generation is focused on, and the very important coherence properties of the stimulated emission process and the characteristics of being able to convert incoherent signals into coherent signals have not been taken seriously.

[0006] In the coherent imaging method, since the phases of the two light-emitting points in the light field have a fixed relationship, high-dimensional signals can be collected through the coherence information between photons and the method of computational reconstruction, which can greatly improve the utilization rate and collection efficiency of optical information, and is of great significance to the preparation of quantum entangled photons, the improvement of optical imaging resolution, and the calculation and storage based on coherent optical signals. In addition, due to the unique interference and diffraction properties of coherent optical signals, the original incoherent signals can be further processed with the help of coherent optical information processing methods to realize the conversion of incoherent light to coherent optical signals. This method has application value in the fields of realizing new imaging paradigms, optical information processing and transmission, optical storage, quantum information calculation, etc. using optical methods. Therefore, it is urgent to pay attention to the generation and conversion methods of coherent optical signals in stimulated radiation processes. The realization and research of this method has important scientific significance and application value. Summary of the invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to provide a coherent optical signal generation and conversion system based on stimulated radiation in view of a series of problems faced by existing incoherent light, including a pump light preparation and target information modulation module with incoherent characteristics, a probe light field preparation module, a stimulated radiation material to generate stimulated radiation optical signal module, a coherent stimulated radiation optical signal processing module, and a signal triggering and synchronization control module; The pump light preparation and target information modulation module with incoherent characteristics is used to generate pump light with incoherent characteristics carrying modulation information, irradiate the pump light with incoherent characteristics onto the stimulated radiation material to produce an excitation effect, and load the carried target information onto the stimulated radiation material; The probe light field preparation module is used to stimulate stimulated radiation material in an excited state; The stimulated radiation material generates a stimulated radiation light signal module for generating a stimulated radiation light signal; The coherent stimulated emission light signal processing module is used to separate the stimulated emission light signal and process the target information carried by the stimulated emission light signal; The signal triggering and synchronization control module includes a computer, a data acquisition card and a photoelectric detector; The data acquisition card is used for signal transmission (to achieve high speed and high bandwidth); The photodetector is used to convert the optical signal into an electrical signal; The computer is used to receive the electrical signal on the photodetector in real time, and control the generation and propagation of the pump light and probe light field with incoherent characteristics, and control the data acquisition of the optical 4f spatial filter and the photodetector.

[0008] The present invention also provides a method for generating and converting a coherent optical signal based on stimulated emission of radiation implemented according to the system, comprising the following steps: Step 1, in a pump light preparation and target information modulation module with incoherent characteristics, generate pump light with incoherent characteristics, and modulate the target information onto the pump light to excite the light field signal; the spectrum of the pump light needs to coincide with the absorption spectrum of the stimulated radiation material to achieve the effect of exciting the stimulated radiation material; Step 2: The probe light field preparation module generates a high-intensity probe light field using high power (peak power greater than 10KW / cm 2 ) and a high coherence (coherence length greater than 1 mm) laser light source to prepare the probe light field; the spectrum of the probe light field needs to coincide with the radiation spectrum of the stimulated radiation material to produce the strongest stimulated radiation light signal; Step 3, the pump light with incoherent characteristics and the probe light field together constitute a pump-probe system, and the pump light with incoherent characteristics and the probe light field are propagated to the stimulated radiation material through coaxial or non-coaxial propagation, inducing the stimulated radiation material to undergo a stimulated radiation process; The stimulated radiation coefficient of the stimulated radiation material needs to be greater than , the stimulated emission light signal emitted by the stimulated emission process carries the target information modulated on the pump light with incoherent characteristics; Step 4, the coherent stimulated emission light signal processing module separates the stimulated emission light signal from other light to extract and process the target stimulated emission light signal; the other light includes pump light with incoherent characteristics, probe light field and ambient light.

[0009] In step 1, the target information is modulated onto the pump light to excite the light field signal, and the method adopted is a time information modulation method or a space information modulation method; In addition, since the pump light with incoherent characteristics does not overlap with the spectrum of the probe light field and the stimulated emission spectrum, a spectral filter is used in front of the photodetector to block the pump light with incoherent characteristics.

[0010] In step 1, the time information modulation method comprises the following steps: Step a1, applying time information modulation to the incoherent light field: Assume that the pump light at time t is , applying an amplitude modulation function , the time modulation is applied by a chopper or electro-optic modulator, and the modulated pump light It is expressed as: , The modulated time signal is a square wave, cosine wave, or pulse train; cosine wave modulation is expressed as: ; in is the modulation depth, is the frequency of the modulating signal, is the phase of the modulation signal; Step a2: Applying the probe light field Then stimulated radiation is generated: the modulated pump light excites the gain medium, and the stimulated radiation light field ,in is the stimulated emission cross section of the stimulated emission material, is the particle number density of the upper energy level, Indicates that both sides of the formula are correlated; is the ground state energy level particle number density, and the relationship is: ; Step a3, demodulate the transmitted time coding information: When using the phase-locked amplification method for demodulation, first generate a reference signal , and then the photodetector converts the received light signal into an electrical signal , With reference signal Multiply and integrate to get the mixed signal X: , , , Where d is the integral symbol, noise represents all signals collected by the photodetector except the stimulated emission light signal. Indicates the phase of the reference signal; Generate reference signal : , The reference signal With receiving signal Multiply and integrate to get the mixed signal Y: ; Then the two mixed signals X and Y are analyzed and processed, and the demodulated output for: , Where G is the set gain coefficient; Step a4, obtaining the time information modulated on the pump light with incoherent characteristics: the modulated information is transmitted through stimulated radiation, which is expressed as: , The spectrum peak position of the demodulated signal directly reflects the modulation frequency, realizing time information decoding. Through the stimulated emission process, the time information modulated on the pump light with incoherent characteristics is converted into the phase or amplitude change of the coherent light signal emitted by the stimulated emission process, and then the modulated time information is extracted through the phase-locked detection method.

[0011] In step 1, the spatial information modulation method comprises the following steps: Step b1: applying sinusoidal stripes periodically distributed in the x direction to the incoherent light field , expressed as: , Among them, u 0 Represents the spatial frequency, the sinusoidal fringes and the original pump light with incoherent characteristics Point multiplication, we get the pump light with incoherent characteristics modulated by spatial information , realize spatial information modulation, expressed as: , Under the condition that the wavelength of the incoherent pump light matches the energy level of the stimulated radiation material, the number density of energy level particles on the stimulated radiation material is Modulated incoherent pump light and ground state energy level particle density Common impact: ; Step b2: Applying the probe light field After that, the stimulated radiation material produces a stimulated radiation process, radiating a coherent stimulated radiation light signal. and Has the following relationship: , in is the stimulated emission cross section of the stimulated emission material; The stimulated emission light signal carries the spatial information of the incoherent pump light, namely the sinusoidal fringes. ; Step b3, processing the information carried in the stimulated radiation light signal: using an optical 4f spatial filtering method to achieve the processing of the target information: using an optical 4f spatial filter composed of lenses L1, L2 and an aperture stop, in step b1, applying sinusoidal stripes periodically distributed in the x direction to the incoherent light field, after Fourier transformation by lens L1, the frequency spectrum is obtained at the position before the aperture stop : , , Among them, u represents the coordinate in the frequency domain, represents the Dirac function; Light field distribution at the front surface of the aperture stop for: , Where f is the focal length of lens L1, The wavelength of the stimulated emission light signal passing through the aperture diaphragm Filter out the signal and only keep the high-frequency signal introduced by the spatial information modulation in step b1 to obtain the optical signal : , , Then the optical signal After the inverse Fourier transform of lens L2, the periodically distributed sinusoidal fringes in the x direction applied to the incoherent light field in step b1 can be obtained at the photodetector position. .

[0012] In step 1, when the time information modulation method is adopted, the time information is modulated onto the pump light with incoherent characteristics through the electro-optic modulator AOM, and the accuracy of the time encoding needs to be less than the excited state lifetime of the stimulated radiation material; When the spatial information modulation method is used, the difference between the spatial frequency of the modulated target signal and the center frequency of the spatial frequency of the probe light field (greater than 10 KHz) needs to be greater than the frequency width of the probe light field (less than 2 KHz).

[0013] In step 1, when the time information modulation method is used, the photodetector needs to have a time resolution of no less than 1ps. At the same time, it is necessary to combine the phase-locked amplification method and use the causal relationship between the coded signal and stimulated radiation to achieve target signal reconstruction; When the spatial information modulation method is used, since the modulated incoherent pump light and the probe light field have obvious differences in spatial frequency, the stimulated radiation light signal can be effectively distinguished from other light in space through an optical 4f spatial filter.

[0014] In step 4, a photodetector PD or CMOS is used to collect and convert optical signals, and a disk medium is used to store the data collected by the photodetector.

[0015] Steps 1 to 4 are all operated under the control of the signal trigger and synchronization control module. The signal trigger and synchronization control module controls the generation time and sequence of the pump light and probe light field with incoherent characteristics through the photoelectric signal, and controls the optical path difference of the pump light and probe light field with incoherent characteristics through the optical delay line. After the stimulated radiation light signal is processed, it is combined with the time coordinate recorded by the signal trigger and synchronization control module to jointly process the target information.

[0016] The present invention also provides an electronic device, comprising a processor and a memory, wherein the memory stores program code, and when the program code is executed by the processor, the processor executes the steps of the described method.

[0017] Beneficial effects: The method proposed in the present invention is a new paradigm for realizing the modulation and transmission of optical information and optical imaging (such as Fourier stack imaging, background-free imaging, and single-exposure imaging). In the field of information optics, the present invention can realize a new type of optical information interaction mode, and realize the confidential communication of coherent optical signals through the stimulated radiation process; in the field of microscopic optics, the present invention helps to achieve a higher resolution and higher acquisition efficiency. At the same time, the present invention can be applied to Fourier stack coherent imaging (FPM) technology, and can realize single-exposure imaging. This imaging characteristic has irreplaceable advantages in the temporal consistency of the acquisition scene; in the field of optical storage, the present invention helps to realize a new type of storage method based on physical processes, which has higher storage efficiency and higher information compression ratio than traditional semiconductor storage, and solves the growing pressure of data storage; the generation of coherent optical signals in the present invention has a similar physical process to the quantum entanglement phenomenon in the field of quantum information, and is therefore a new type of preparation method for entangled light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0019] Figure 1 The present invention provides a flowchart of a method.

[0020] Figure 2 This is a structural diagram of a stimulated emission coherent optical signal generation and conversion system based on time information modulation provided by an embodiment of the present invention.

[0021] Figure 3 This is a structural diagram of a system for generating and converting coherent optical signals by stimulated emission of radiation based on spatial information modulation provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The embodiment of the present invention provides a coherent optical signal generation and conversion system based on stimulated radiation, including a pump light preparation and target information modulation module with incoherent characteristics, a probe light field preparation module, a stimulated radiation material generation stimulated radiation optical signal module, a coherent stimulated radiation optical signal processing module, and a signal triggering and synchronization control module; The pump light preparation and target information modulation module with incoherent characteristics is used to generate pump light with incoherent characteristics carrying modulation information, irradiate the pump light with incoherent characteristics onto the stimulated radiation material to produce an excitation effect, and load the carried target information onto the stimulated radiation material; The probe light field preparation module is used to stimulate stimulated radiation material in an excited state; The stimulated radiation material generates a stimulated radiation light signal module for generating a stimulated radiation light signal; The coherent stimulated emission light signal processing module is used to separate the stimulated emission light signal and process the target information carried by the stimulated emission light signal; The signal triggering and synchronization control module includes a computer, a data acquisition card and a photoelectric detector; The data acquisition card is used for signal transmission (to achieve high speed and high bandwidth); The photodetector is used to convert the optical signal into an electrical signal; The computer is used to receive the electrical signal on the photodetector in real time, and control the generation and propagation of the pump light and probe light field with incoherent characteristics, and control the data acquisition of the optical 4f spatial filter and the photodetector.

[0023] like Figure 1 As shown, the embodiment of the present invention also provides a method for generating and converting a coherent optical signal based on stimulated emission of radiation implemented according to the system, comprising the following steps: Step 1, in a pump light preparation and target information modulation module with incoherent characteristics, generate pump light with incoherent characteristics, and modulate the target information onto the pump light to excite the light field signal; the spectrum of the pump light needs to coincide with the absorption spectrum of the stimulated radiation material to achieve the effect of exciting the stimulated radiation material; Step 2: The probe light field preparation module generates a high-intensity probe light field using high power (peak power greater than 10KW / cm 2 ) and a high coherence (coherence length greater than 1 mm) laser light source to prepare the probe light field; the spectrum of the probe light field needs to coincide with the radiation spectrum of the stimulated radiation material to produce the strongest stimulated radiation light signal; Step 3, the pump light with incoherent characteristics and the probe light field together constitute a pump-probe system, and the pump light with incoherent characteristics and the probe light field are propagated to the stimulated radiation material through coaxial or non-coaxial propagation, inducing the stimulated radiation material to undergo a stimulated radiation process; The stimulated radiation coefficient of the stimulated radiation material needs to be greater than , the stimulated emission light signal emitted by the stimulated emission process carries the target information modulated on the pump light with incoherent characteristics; Step 4, the coherent stimulated emission light signal processing module separates the stimulated emission light signal from other light to extract and process the target stimulated emission light signal; the other light includes pump light with incoherent characteristics, probe light field and ambient light.

[0024] In step 1, the target information is modulated onto the pump light to excite the light field signal, and the method adopted is a time information modulation method or a space information modulation method; In addition, since the pump light with incoherent characteristics does not overlap with the spectrum of the probe light field and the stimulated emission spectrum, a spectral filter is used in front of the photodetector to block the pump light with incoherent characteristics.

[0025] Figure 2 This is a structural diagram of a method for generating and converting a stimulated emission coherent optical signal based on time information modulation provided in an embodiment of the present invention.

[0026] The pump light with incoherent characteristics (central wavelength 800nm) passes through the optical modulator to modulate the sinusoidal time information with a frequency of 10MHz on the incoherent light. Then the probe light field (central wavelength 1064nm) transmits the two beams coaxially through the optical combiner. The pump light with incoherent characteristics makes the stimulated radiation sample (Nd:YVO 4 The crystal is excited, and then, under the action of the probe light field, Nd:YVO 4 The crystal undergoes stimulated emission and emits a coherent stimulated emission light signal (central wavelength 1064nm). Then, the optical filter absorbs or reflects the incoherent pump light, hindering the propagation of the pump light. The signal S(t) collected by the PD photodetector (which must have a time resolution of <10ps) contains the stimulated emission light signal and the probe light field. Since the intensity of the stimulated emission light signal is very weak compared to the intensity of the probe light field (signal-to-noise ratio <10 -5 ), so in the signal triggering and synchronization control module, it is necessary to use the phase-locked amplification data processing method to combine the signal S(t) collected by the detector with the analog signal R 1 (t), R 2 (t) performing multiplication and integration operations to obtain a stimulated radiation light signal. The time information modulation method comprises the following steps: Step a1, applying time information modulation to the incoherent light field. Assume that the pump light at time t is , applying an amplitude modulation function , this process can be temporally modulated by a chopper or electro-optic modulator, and the modulated pump light It is expressed as: , The modulated time signal can be a square wave, a cosine wave, or a pulse train. For example, cosine wave modulation is represented by: ; in is the modulation depth, is the frequency of the modulation signal (set to 10MHz), is the phase of the modulating signal.

[0027] Step a2: Applying the probe light field Stimulated radiation is then generated: the modulated pump light excites the gain medium (such as atoms or molecules), and the stimulated radiation light field ,in is the stimulated emission cross section of the stimulated emission material, is the particle number density of the upper energy level, Indicates that there is a correlation between the two sides of the formula. is the ground state energy level particle number density, and the relationship is: , this relationship shows that the number density of particles at the upper energy level This is related to the time information of the modulation on the pump light with incoherent characteristics in step a1. In this process, it is reflected that the stimulated emission light signal with coherence inherits the modulation information on the pump light with incoherent characteristics.

[0028] Step a3, demodulate the transmitted time coding information. When using the phase-locked amplification method for demodulation, a reference signal is first generated , then the signal With reference signal Multiply and integrate to get the mixed signal X: , , , Where d is the integral symbol, noise represents all the signals collected by the detector except the stimulated emission light signal. represents the circular frequency of the reference signal, represents the phase of the reference signal; please note that the integration time dt is related to the signal-to-noise ratio of the stimulated emission signal in the detection signal S(t), which is -5Under the condition of signal-to-noise ratio, the integration time needs to be set greater than 10μs. The longer the integration time, the better the signal quality, but the greater the time cost of acquiring the signal.

[0029] Generate reference signal (with reference signal The difference is the change in phase): , The reference signal With receiving signal Multiply and integrate to get the mixed signal Y: ; Then the two mixed signals X and Y are analyzed and processed, and the demodulated output for: , Where G is the set gain coefficient, X and Y are the in-phase component and the orthogonal component respectively; Step a4, obtain the time information modulated on the pump light with incoherent characteristics. The essence of the modulated information transmitted through stimulated radiation is: The peak position of the spectrum of the demodulated signal directly reflects the modulation frequency, realizing the decoding of time information. The core idea is to convert the time information modulated on the incoherent pump light into the phase or amplitude change of the coherent light signal emitted by the stimulated emission process through the stimulated emission process, and then extract the modulated time information through the phase-locked detection method.

[0030] The system adds a high-precision signal generator and extends the integration time dt to 1s to achieve a lower signal-to-noise ratio (less than 10 -7 ) of coherent optical signals.

[0031] The system may be equipped with a low-noise acquisition device, such as a cooling detector, to achieve higher quality signal acquisition.

[0032] The system can add a dichroic mirror to combine the light beams, thereby avoiding the waste of light energy and facilitating safer and more efficient conversion of coherent light signals.

[0033] The system can be added with a dedicated integrated circuit of a suitable combinational logic gate circuit, a programmable gate array (PGA), a field programmable gate array (FPGA), a high-throughput data acquisition card, etc. to achieve high-speed and accurate system process control and help achieve automated operation.

[0034] The system can be equipped with computers, signal generators and other equipment to control the operation of the system by writing software programs. At the same time, computer readable media can be added as a carrier for signal storage and transmission.

[0035] As a possible way to achieve this, Figure 3 A system diagram of the generation and conversion of stimulated emission coherent light signals based on spatial information modulation provided by an embodiment of the present invention.

[0036] Pump light with incoherent properties (Central wavelength 800nm) modulates the spatial information through the optical spatial light modulator SLM, and the probe light field (Central wavelength 1064nm) together constitute a pump-probe system, and the time delay (1ps) is set by the signal trigger and synchronization control module. In this case, the stimulated radiation signal light generated has coherence, so the target information can be processed through the optical 4f spatial filter. All the above processes are controlled by the signal trigger and synchronization control module. Since this embodiment uses light field spatial information modulation, it is capable of acquiring and imaging stimulated radiation light signals through a single exposure. Compared with the scanning imaging method, it has high data throughput and all pixels in the image are at the same time, which is crucial in the fields of biological imaging, ultrafast imaging, weak signal analysis and background-free imaging.

[0037] In the process of spatial information modulation and demodulation, the core idea is to modulate the incoherent pump light with spatial information and use the coherence of stimulated radiation to transmit the modulated spatial information. The spatial information modulation method includes the following steps: Step b1: applying sinusoidal stripes periodically distributed in the x direction to the incoherent light field , expressed as: , Among them, u 0 represents the spatial frequency, which is set to 200 lp / mm here. The sinusoidal fringes are incoherent with the original pump light. Point multiplication, we get the pump light with incoherent characteristics modulated by spatial information , the process of realizing spatial information modulation is expressed as: , According to the principle of stimulated absorption, under the condition that the wavelength of the incoherent pump light (central wavelength 800nm) matches the energy level of the stimulated radiation material, the energy level particle number density on the stimulated radiation material Modulated incoherent pump light and ground state energy level particle density Common impact: ; Step b2: Applying the probe light field (Central wavelength 1064nm), the stimulated radiation material (Nd:YVO 4Crystal) produces stimulated emission process, radiating coherent stimulated emission light signal. ,in is the stimulated radiation cross section of the stimulated radiation material; since N 2 (x) The spatial information modulated on the pump light with incoherent characteristics in step b1 Therefore, the stimulated emission light signal carries the spatial information of the pump light with incoherent characteristics. ; Step b3, processing the information carried in the stimulated emission light signal: In this embodiment, an optical 4f spatial filter (such as Figure 3 As shown in FIG, the optical 4f spatial filter is composed of lenses L1, L2 and an aperture stop) can realize the processing of target information: in the case of using sinusoidal coding mentioned in step b1, after Fourier transform of lens L1, the frequency spectrum is obtained at the position before the aperture stop. : , , Among them, u represents the coordinate in the frequency domain, represents the Dirac function. Represents the light field distribution at the front surface of the aperture stop: , Where f is the focal length of lens L1 (100 mm), Indicates the wavelength of the stimulated emission light signal (1064nm). Under this configuration, the stimulated emission light signal and the probe light field can be distinguished in space (the position difference of the center frequency observed in the experiment is 6mm). Filter out other signals and only retain the high-frequency signal introduced by the light field spatial information modulation in step b1 to obtain the optical signal : , , Then the optical signal After the inverse Fourier transform of lens L2, the periodically distributed sinusoidal fringes in the x direction of the incoherent light field applied in step b1 can be obtained at the detector position. The experimental results show that the system for generating and converting coherent optical signals by stimulated emission of radiation based on spatial information modulation can be used in The stimulated emission light signal is collected in an environment with a low signal-to-noise ratio, and the suppression effect on the probe light field can achieve >160dB, indicating that coherent optical signals have obvious advantages over incoherent light in the field of signal processing.

[0038] When the system modulates the spatial information of the pump light with incoherent characteristics, it can use grating projection to produce a structured effect, or it can use a spatial light modulator (SLM), which can dynamically control the amplitude, phase or polarization state of the light wave. Devices that can also realize spatial information modulation include digital micromirror devices (DMDs).

[0039] The system can be equipped with a high numerical aperture objective lens and a high spatial frequency modulation device, which helps to achieve coherent optical signal generation and conversion under lower signal-to-noise ratio conditions.

[0040] The system can be added with a spatial light field relay system, which helps to eliminate the problem of low modulation depth caused by the Talbot effect during light transmission.

[0041] The system can incorporate a codeable unconventional aperture stop, which helps to restore high spatial resolution while effectively suppressing the influence of stray light.

[0042] It should be noted that the aforementioned explanation of the embodiment of generating and converting coherent light signals based on stimulated emission is also applicable to the Fourier aperture coded microscopy imaging method based on stimulated emission of light in this embodiment, which can further synthesize microscopic images with high spatial resolution and large field of view by sequentially illuminating the sample with a serialized stimulated emission light field and collecting light field information under multiple different viewing angles, and will not be described in detail here. The method of generating coherent light signals by stimulated emission in this application can be used not only in the field of ultrafast optics, but also in other optical fields.

[0043] The incoherent optical signals mentioned in the related art mentioned in the background technology are converted into coherent optical signals, which can be used in the fields of optical information processing, quantum communication, microscopic imaging, etc. In the embodiment of the present invention, the incoherent optical signals carrying the target information are converted into coherent optical signals by the process of generating stimulated radiation by means of a pump-probe method, and the processing of the target information is realized by utilizing the differences in the time and space dimensions. Therefore, the embodiment of the present invention realizes the transmission of the target information on the incoherent light to the coherent optical signal through the stimulated radiation technology, makes full use of the coherence of the stimulated radiation optical signal, and can be used for the processing and processing of coherent optical information.

[0044] According to the coherent optical signal generation and conversion method based on stimulated radiation proposed in the embodiment of the present application, the timing relationship between the modules can be determined by the signal synchronization component, including incoherent light field generation and modulation, probe light field preparation, stimulated radiation material and stimulated radiation process, coherent stimulated radiation light field processing module, pulse synchronization and timing control module. Incoherent light field preparation and modulation of target information, application of probe light field, generation of stimulated radiation, target information processing of coherent stimulated radiation signal, recording and transmission of optical signal, pulse signal triggering and synchronization control. By loading the target information onto the incoherent pump light, and then stimulating the matching stimulated radiation material, coherent stimulated radiation photons are generated under the action of the probe light field, and then the target information is demodulated in the light field dimension, the light field is recorded by the detector, the excitation-modulation-detection timing is coordinated by the synchronization component, and the coherent optical signal is processed and analyzed in real time by the optical information processing module. The above-mentioned whole process requires the management of the pulse synchronization timing control module.

[0045] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless otherwise clearly and specifically defined. In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0046] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0047] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection with one or N wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0048] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above embodiment, N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0049] The present invention provides a system and method for generating and converting coherent optical signals based on stimulated emission of radiation. There are many methods and approaches to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A coherent optical signal generation and conversion system based on stimulated emission of radiation, characterized in that: It includes a pump light preparation module with incoherent characteristics and a target information modulation module, a probe light field preparation module, a stimulated radiation material generating stimulated radiation light signal module, a coherent stimulated radiation light signal processing module, and a signal triggering and synchronization control module; The pump light preparation and target information modulation module with incoherent characteristics is used to generate pump light with incoherent characteristics carrying modulation information, irradiate the pump light with incoherent characteristics onto the stimulated radiation material to produce an excitation effect, and load the carried target information onto the stimulated radiation material; The probe light field preparation module is used to stimulate stimulated radiation material in an excited state; The stimulated radiation material generates a stimulated radiation light signal module for generating a stimulated radiation light signal; The coherent stimulated emission light signal processing module is used to separate the stimulated emission light signal and process the target information carried by the stimulated emission light signal; The signal triggering and synchronization control module includes a computer, a data acquisition card and a photoelectric detector; The data acquisition card is used for signal transmission; The photodetector is used to convert the optical signal into an electrical signal; The computer is used to receive the electrical signal on the photodetector in real time, and control the generation and propagation of the pump light and probe light field with incoherent characteristics, and control the data acquisition of the optical 4f spatial filter and the photodetector.

2. A method for generating and converting coherent optical signals based on stimulated emission of radiation implemented by the system according to claim 1, characterized in that: The steps include: Step 1, in a pump light preparation and target information modulation module with incoherent characteristics, generate pump light with incoherent characteristics, and modulate the target information onto the pump light to excite the light field signal; the spectrum of the pump light needs to coincide with the absorption spectrum of the stimulated radiation material to achieve the effect of exciting the stimulated radiation material; Step 2: The probe light field preparation module generates a high-intensity probe light field, and uses a high-power and high-coherence laser light source to prepare the probe light field; the spectrum of the probe light field needs to coincide with the radiation spectrum of the stimulated radiation material to generate the strongest stimulated radiation light signal; Step 3: The pump light with incoherent characteristics and the probe light field together constitute a pump-probe system. The pump light with incoherent characteristics and the probe light field are propagated to the stimulated radiation material through coaxial or non-coaxial propagation to induce the stimulated radiation material to undergo stimulated radiation process. The stimulated radiation coefficient of the stimulated radiation material needs to be greater than , the stimulated emission light signal emitted by the stimulated emission process carries the target information modulated on the pump light with incoherent characteristics; Step 4, the coherent stimulated emission light signal processing module separates the stimulated emission light signal from other light to extract and process the target stimulated emission light signal; the other light includes pump light with incoherent characteristics, probe light field and ambient light.

3. The method according to claim 2, characterized in that In step 1, the target information is modulated onto the pump light to excite the light field signal, and the method adopted is a time information modulation method or a space information modulation method; A spectral filter is used in front of the photodetector to block the pump light with incoherent characteristics.

4. The method according to claim 3, characterized in that In step 1, the time information modulation method comprises the following steps: Step a1, applying time information modulation to the incoherent light field: Assume that the pump light at time t is , applying an amplitude modulation function , the time modulation is applied by a chopper or electro-optic modulator, and the modulated pump light It is expressed as: ， The modulated time signal is a square wave, cosine wave, or pulse train; cosine wave modulation is expressed as: ; in is the modulation depth, is the frequency of the modulating signal, is the phase of the modulation signal; Step a2: Applying the probe light field Then stimulated radiation is generated: the modulated pump light excites the gain medium, and the stimulated radiation light field ,in is the stimulated emission cross section of the stimulated emission material, is the particle number density of the upper energy level, Indicates that both sides of the formula are correlated; is the ground state energy level particle number density, and the relationship is: ; Step a3, demodulate the transmitted time coding information: When using the phase-locked amplification method for demodulation, first generate a reference signal , and then the photodetector converts the received light signal into an electrical signal , With reference signal Multiply and integrate to get the mixed signal X: ， ， ， Where d is the integral symbol, noise represents all signals collected by the photodetector except the stimulated emission light signal. represents the phase of the reference signal; Generate reference signal : ， The reference signal With receiving signal Multiply and integrate to get the mixed signal Y: ； Then the two mixed signals X and Y are analyzed and processed, and the demodulated output for: ， Where G is the set gain coefficient; Step a4, obtaining the time information modulated on the pump light with incoherent characteristics: the modulated information is transmitted through stimulated radiation, which is expressed as: ， The spectrum peak position of the demodulated signal directly reflects the modulation frequency, realizing time information decoding. Through the stimulated emission process, the time information modulated on the pump light with incoherent characteristics is converted into the phase or amplitude change of the coherent light signal emitted by the stimulated emission process, and then the modulated time information is extracted through the phase-locked detection method.

5. The method according to claim 3, characterized in that: In step 1, the spatial information modulation method comprises the following steps: Step b1: applying sinusoidal stripes periodically distributed in the x direction to the incoherent light field , expressed as: ， Where u0 represents the spatial frequency, the sinusoidal fringes are related to the original pump light with incoherent characteristics. Point multiplication, we get the pump light with incoherent characteristics modulated by spatial information , realize spatial information modulation, expressed as: ， Under the condition that the wavelength of the incoherent pump light matches the energy level of the stimulated radiation material, the number density of energy level particles on the stimulated radiation material is Modulated incoherent pump light and ground state energy level particle density Common impact: ； Step b2: Applying the probe light field After that, the stimulated radiation material produces a stimulated radiation process, radiating a coherent stimulated radiation light signal. and Has the following relationship: ， in is the stimulated emission cross section of the stimulated emission material; The stimulated emission light signal carries the spatial information of the incoherent pump light, namely the sinusoidal fringes. ; Step b3, processing the information carried in the stimulated radiation light signal: using an optical 4f spatial filtering method to achieve the processing of the target information: using an optical 4f spatial filter composed of lenses L1, L2 and an aperture stop, in step b1, applying sinusoidal stripes periodically distributed in the x direction to the incoherent light field, after Fourier transformation by lens L1, the frequency spectrum is obtained at the position before the aperture stop : ， ， Among them, u represents the coordinate in the frequency domain, represents the Dirac function; Light field distribution at the front surface of the aperture stop for: ， Where f is the focal length of lens L1, The wavelength of the stimulated emission light signal passing through the aperture diaphragm Filter out the signal and only keep the high-frequency signal introduced by the spatial information modulation in step b1 to obtain the optical signal : ， ， Then the optical signal After the inverse Fourier transform of lens L2, the sinusoidal fringes with periodic distribution in the x direction applied to the incoherent light field in step b1 can be obtained at the photodetector position. .

6. The method according to claim 4 or 5, characterized in that: In step 1, when the time information modulation method is adopted, the time information is modulated onto the pump light with incoherent characteristics through the electro-optic modulator AOM, and the accuracy of the time encoding needs to be less than the excited state lifetime of the stimulated radiation material; When the spatial information modulation method is used, the difference between the spatial frequency of the modulated target signal and the center frequency of the spatial frequency of the probe light field needs to be greater than the frequency width of the probe light field.

7. The method according to claim 6, characterized in that In step 1, when the time information modulation method is adopted, the time resolution capability of the photodetector is not less than 1ps, and the target signal is reconstructed by combining the phase-locked amplification method and utilizing the causal relationship between the coded signal and stimulated radiation; When the spatial information modulation method is adopted, the stimulated emission light signal is effectively distinguished from other light in space through an optical 4f spatial filter.

8. The method according to claim 7, characterized in that In step 4, a photodetector PD or CMOS is used to collect and convert optical signals, and a disk medium is used to store data collected by the photodetector.

9. The method according to claim 8, characterized in that Steps 1 to 4 are all operated under the control of the signal trigger and synchronization control module. The signal trigger and synchronization control module controls the generation time and sequence of the pump light and probe light field with incoherent characteristics through the photoelectric signal, and controls the optical path difference of the pump light and probe light field with incoherent characteristics through the optical delay line. After the stimulated radiation light signal is processed, it is combined with the time coordinate recorded by the signal trigger and synchronization control module to jointly process the target information.

10. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores program codes, and when the program codes are executed by the processor, the processor executes the steps of the method according to claim 2.

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