A coherent optical signal generation and conversion system and method based on stimulated emission of radiation

Abstract

The present invention provides a coherent optical signal generation and conversion system and method based on stimulated radiation. The system includes 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, which is irradiated on 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 the stimulated radiation material in an excited state; the present invention effectively solves the problems faced by incoherent light, and fully utilizes the coherence characteristics of stimulated radiation optical signals in the fields of optical imaging, optical information transmission, quantum information processing, biomedicine, etc., breaking through the bottleneck of the existing optical field.

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 emission of radiation. Background Art

[0002] The stimulated emission phenomenon indicates that when a luminous 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 emission and spontaneous emission from excited particles is the coherence of stimulated emission photons. Spontaneous emission is a spontaneous process in atoms that is not controlled by an external radiation field. The phase of the spontaneous emission field from a large number of atoms is incoherent, and the propagation direction and polarization state of the radiation field are also randomly distributed. In contrast, stimulated emission is a luminescence process controlled by an external probe field. Therefore, the frequency, phase, propagation direction, and polarization state of the stimulated emission field are exactly the same as those of the external radiation field.

[0004] The invention of the laser is a crucial application of the principle of stimulated emission of radiation, a process essential for laser generation. More importantly, in recent years, stimulated luminescence by emission of radiation has gradually demonstrated its unique value in biomedical imaging, providing new approaches and methods for observing non-fluorescent samples. Stimulated emission of radiation (STED), a technique that combines stimulated emission of radiation with fluorescence, can break the diffraction limit and achieve super-resolution microscopy.

[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 imaging field, 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. This 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, the imaging method can only be used through single-point acquisition and then scanning and splicing, which has low acquisition efficiency and poor imaging quality. In imaging based on stimulated emission signals, only the incremental process of stimulated emission on photons is focused on. The very important coherence properties of the stimulated emission process and the feature that can realize the conversion of incoherent signals into coherent signals have not been taken seriously.

[0006] In coherent imaging methods, since the phases of the two light-emitting points in the light field have a fixed relationship, high-dimensional signals can be collected through computational reconstruction methods using the coherence information between photons. This can greatly improve the utilization 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 processes 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 achieve the conversion of incoherent light to coherent optical signals. This method has application value in the fields of using optical methods to realize new imaging paradigms, optical information processing and transmission, optical storage, quantum information computing, etc. Therefore, there is an urgent need to pay attention to the generation and conversion methods of coherent optical signals in the stimulated emission process. The implementation and research of this method have 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 address a series of problems faced by existing incoherent light and provide a coherent optical signal generation and conversion system based on stimulated emission of radiation. The system includes a pump light preparation and target information modulation module with incoherent characteristics, a probe light field preparation module, a module for generating stimulated emission of radiation light signals from stimulated emission materials, a coherent stimulated emission light signal processing module, and a signal triggering and synchronization control module.

[0008] 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 on the stimulated radiation material to produce an excitation effect, and load the carried target information onto the stimulated radiation material;

[0009] The probe light field preparation module is used to stimulate stimulated radiation material in an excited state;

[0010] The stimulated emission material generates a stimulated emission light signal module for generating a stimulated emission light signal;

[0011] 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;

[0012] The signal triggering and synchronization control module includes a computer, a data acquisition card and a photoelectric detector;

[0013] The data acquisition card is used for signal transmission (to achieve high speed and high bandwidth);

[0014] The photodetector is used to convert the optical signal into an electrical signal;

[0015] The computer is used to receive the electrical signal on the photodetector in real time, 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.

[0016] The present invention also provides a method for generating and converting coherent optical signals based on stimulated emission of radiation, which is implemented according to the system, and comprises the following steps:

[0017] 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 emission substance to achieve the effect of stimulating the stimulated emission substance;

[0018] 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 emission material to produce the strongest stimulated emission light signal;

[0019] 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 propagate to the stimulated radiation material through coaxial or non-coaxial propagation, inducing the stimulated radiation material to generate a stimulated radiation process.

[0020] The stimulated emission coefficient of the stimulated emission 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;

[0021] 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.

[0022] 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;

[0023] 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.

[0024] In step 1, the time information modulation method includes the following steps:

[0025] 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 , temporal modulation is applied by a chopper or electro-optic modulator, and the modulated pump light Expressed as:

[0026] ,

[0027] The modulated time signal is a square wave, cosine wave, or pulse train; cosine wave modulation is expressed as: ;

[0028] in is the modulation depth, is the frequency of the modulating signal, is the phase of the modulated signal;

[0029] Step a2: Applying the probe light field Then stimulated emission of radiation is generated: the modulated pump light excites the gain medium, and the stimulated emission of radiation light field ,in is the stimulated emission cross section of the stimulated emission material, is the number density of particles at 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: ;

[0030] Step a3, demodulating the transmitted time code information: When using the phase-locked amplification method to demodulate, 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:

[0031] ,

[0032] ,

[0033] ,

[0034] 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;

[0035] Generate reference signal :

[0036] ,

[0037] The reference signal and receiving signals Multiply and integrate to get the mixed signal Y:

[0038] ;

[0039] Then the two mixed signals X and Y are analyzed and processed, and the demodulated output for:

[0040] ,

[0041] Where G is the set gain coefficient;

[0042] Step a4, obtaining the time information modulated on the pump light with incoherent characteristics: the modulated information is transmitted through stimulated emission and is expressed as:

[0043] ,

[0044] The peak position of the spectrum of the demodulated signal directly reflects the modulation frequency, realizing time information decoding. Through the stimulated emission process, the time information modulated on the incoherent pump light is converted into the phase or amplitude change of the coherent light signal emitted by the stimulated emission process. The modulated time information is then extracted through the phase-locked detection method.

[0045] In step 1, the spatial information modulation method includes the following steps:

[0046] Step b1: applying sinusoidal stripes periodically distributed in the x direction to the incoherent light field , expressed as:

[0047] ,

[0048] 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 , to achieve spatial information modulation, expressed as:

[0049] ,

[0050] Under the condition that the wavelength of the pump light with incoherent characteristics 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:

[0051] ;

[0052] 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:

[0053] ,

[0054] in is the stimulated emission cross section of the stimulated emission material;

[0055] The stimulated emission light signal carries the spatial information of the incoherent pump light, namely the sinusoidal fringes ;

[0056] Step b3, processing the information carried in the stimulated emission 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, applying a sinusoidal stripe periodically distributed in the x direction to the incoherent light field in step b1, after Fourier transform of lens L1, the frequency spectrum is obtained at the position before the aperture stop. :

[0057] ,

[0058] ,

[0059] Among them, u represents the coordinate in the frequency domain, represents the Dirac function;

[0060] Light field distribution at the front surface of the aperture stop for:

[0061] ,

[0062] Where f is the focal length of lens L1, The wavelength of the stimulated emission light signal passing through the aperture Filter out the signal and only retain the high-frequency signal introduced by the spatial information modulation in step b1 to obtain the optical signal :

[0063] ,

[0064] ,

[0065] Then the optical signal After the inverse Fourier transform of lens L2, the sinusoidal stripes with periodic distribution in the x direction can be obtained at the photodetector position. .

[0066] In step 1, when the time information modulation method is used, the time information is modulated onto the pump light with incoherent characteristics through the electro-optical modulator (AOM). The accuracy of the time encoding needs to be less than the excited state lifetime of the stimulated emission material.

[0067] 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).

[0068] In step 1, when the time information modulation method is used, the photodetector needs to have a time resolution of no less than 1 ps. 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 emission to achieve target signal reconstruction;

[0069] 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.

[0070] 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.

[0071] Steps 1 to 4 all operate under the control of the signal triggering and synchronization control module. The signal triggering and synchronization control module controls the generation time and sequence of the incoherent pump light and probe light field through photoelectric signals, and controls the optical path difference between the incoherent pump light and probe light field through optical delay lines. After the stimulated emission light signal is processed, the target information is jointly processed in combination with the time coordinates recorded by the signal triggering and synchronization control module.

[0072] 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 method.

[0073] 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 method, realizing the confidential communication of coherent optical signals through the stimulated emission process; in the field of microscopy, the present invention helps to achieve higher resolution and higher acquisition efficiency. At the same time, the present invention can be applied to Fourier stack coherent imaging (FPM) technology to achieve single-exposure imaging. This imaging characteristic has irreplaceable advantages in terms of 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, solving the growing pressure on data storage; the generation of coherent optical signals in the present invention has similar physical processes to the quantum entanglement phenomenon in the field of quantum information, and therefore is a new method for preparing entangled light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0075] Figure 1 This is a flowchart of a method provided by an embodiment of the present invention.

[0076] Figure 2 This is a structural diagram of a system for generating and converting coherent optical signals by stimulated emission of radiation based on time information modulation provided by an embodiment of the present invention.

[0077] 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

[0078] The embodiment of the present invention provides a coherent optical signal generation and conversion system based on stimulated emission of radiation, which includes a pump light preparation and target information modulation module with incoherent characteristics, a probe light field preparation module, a stimulated emission material generation stimulated emission optical signal module, a coherent stimulated emission optical signal processing module, and a signal triggering and synchronization control module;

[0079] 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 on the stimulated radiation material to produce an excitation effect, and load the carried target information onto the stimulated radiation material;

[0080] The probe light field preparation module is used to stimulate stimulated radiation material in an excited state;

[0081] The stimulated emission material generates a stimulated emission light signal module for generating a stimulated emission light signal;

[0082] 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;

[0083] The signal triggering and synchronization control module includes a computer, a data acquisition card and a photoelectric detector;

[0084] The data acquisition card is used for signal transmission (to achieve high speed and high bandwidth);

[0085] The photodetector is used to convert the optical signal into an electrical signal;

[0086] The computer is used to receive the electrical signal on the photodetector in real time, 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.

[0087] like Figure 1 As shown, an embodiment of the present invention further 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:

[0088] 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 emission substance to achieve the effect of stimulating the stimulated emission substance;

[0089] 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 emission material to produce the strongest stimulated emission light signal;

[0090] 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 propagate to the stimulated radiation material through coaxial or non-coaxial propagation, inducing the stimulated radiation material to generate a stimulated radiation process.

[0091] The stimulated emission coefficient of the stimulated emission 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;

[0092] 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.

[0093] 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;

[0094] 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.

[0095] Figure 2 This is a structural diagram of a method for generating and converting coherent optical signals by stimulated emission based on time information modulation provided by an embodiment of the present invention.

[0096] The pump light with incoherent characteristics (central wavelength 800nm) passes through the optical modulator, modulating the sinusoidal time information with a frequency of 10MHz on the incoherent light. Then the probe light field (central wavelength 1064nm) transmits the two light beams coaxially through the optical combiner. The pump light with incoherent characteristics excites the stimulated emission sample (Nd:YVO4 crystal). Then, under the action of the probe light field, the Nd:YVO4 crystal undergoes a stimulated emission process and radiates 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, a phase-locked amplification data processing method is required to multiply and integrate the signal S(t) collected by the detector with the analog signals R1(t) and R2(t) to obtain the stimulated emission light signal. The time information modulation method includes the following steps:

[0097] Step a1: Apply time information modulation to the incoherent light field. Assume that the pump light at time t is , applying an amplitude modulation function , the process can be temporally modulated by a chopper or electro-optic modulator, and the modulated pump light Expressed as:

[0098] ,

[0099] The modulated time signal can be a square wave, a cosine wave, or a pulse train. For example, cosine wave modulation is represented by: ;

[0100] in is the modulation depth, is the frequency of the modulation signal (set to 10MHz), is the phase of the modulating signal.

[0101] 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 number density of particles at 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 in 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 shown that the coherent stimulated emission light signal inherits the modulation information on the pump light with incoherent characteristics.

[0102] Step a3, demodulate the transmitted time code 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:

[0103] ,

[0104] ,

[0105] ,

[0106] 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). -5 Under the condition of signal-to-noise ratio, the integration time needs to be set to greater than 10μs. The longer the integration time, the better the signal quality, but the greater the time overhead of signal acquisition.

[0107] Generate reference signal (with reference signal The difference is the phase change):

[0108] ,

[0109] The reference signal and receiving signals Multiply and integrate to get the mixed signal Y:

[0110] ;

[0111] Then the two mixed signals X and Y are analyzed and processed, and the demodulated output for:

[0112] ,

[0113] Where G is the set gain coefficient, X and Y are the in-phase component and quadrature component respectively;

[0114] Step a4: obtain the temporal information modulated on the pump light with incoherent characteristics. The essence of the modulated information transmitted through stimulated emission is: The peak position of the demodulated signal spectrum directly reflects the modulation frequency, enabling time information decoding. The core idea is to convert the temporal information modulated on the incoherent pump light into phase or amplitude changes of the coherent optical signal emitted by the stimulated emission process through stimulated emission of radiation, and then extract the modulated temporal information through phase lock-in detection.

[0115] The system is equipped with a high-precision signal generator and the integration time dt is extended to 1s to achieve the goal of -7 ) of coherent optical signals.

[0116] The system may be equipped with a low-noise acquisition device, such as a refrigerated detector, to achieve higher quality signal acquisition.

[0117] The system can be added with a dichroic mirror to combine the light beams, thereby avoiding waste of light energy and facilitating safer and more efficient conversion of coherent optical signals.

[0118] 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 realize automated operation.

[0119] 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.

[0120] As a possible way to achieve this, Figure 3 A system diagram of the generation and conversion of coherent optical signals by stimulated emission of radiation based on spatial information modulation provided by an embodiment of the present invention.

[0121] Pump light with incoherent characteristics (Central wavelength 800nm) modulates the spatial information through the optical spatial light modulator SLM, and the probe light field (central wavelength 1064nm) together form a pump-probe system. A time delay (1ps) is set via the signal triggering and synchronization control module. The resulting stimulated emission signal light, due to its coherence, can be processed by an optical 4f spatial filter to achieve target information. All of the above processes are controlled by the signal triggering and synchronization control module. Because this embodiment utilizes light field spatial information modulation, it is capable of capturing and imaging stimulated emission light signals through a single exposure. Compared to scanning imaging methods, this approach offers high data throughput and simultaneous acquisition of all pixels in the image, which is crucial in fields such as biological imaging, ultrafast imaging, weak signal analysis, and background-free imaging.

[0122] 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:

[0123] Step b1: applying sinusoidal stripes periodically distributed in the x direction to the incoherent light field , expressed as:

[0124] ,

[0125] Where u0 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:

[0126] ,

[0127] According to the principle of stimulated absorption, under the condition that the wavelength of the pump light with incoherent characteristics (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:

[0128] ;

[0129] Step b2: Applying the probe light field (Central wavelength 1064nm), the stimulated radiation material (Nd:YVO4 crystal) produces a stimulated radiation process, radiating a coherent stimulated radiation light signal. ,in is the stimulated emission cross section of the stimulated emission material; since N2(x) is related to 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. ;

[0130] 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 method of optical 4f spatial filter (composed of lenses L1, L2 and aperture diaphragm) can realize the processing of target information: in the case of using sine encoding mentioned in step b1, after Fourier transform of lens L1, the frequency spectrum is obtained at the position before the aperture diaphragm. :

[0131] ,

[0132] ,

[0133] 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:

[0134] ,

[0135] Where f is the focal length of lens L1 (100mm), 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 (a distance of 6mm in the position difference of the center frequency was observed in the experiment). 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 :

[0136] ,

[0137] ,

[0138] Then the optical signal After the inverse Fourier transform of lens L2, the sinusoidal stripes with periodic distribution in the x direction of the incoherent light field in step b1 can be obtained at the detector position. The experimental results show that the system of 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 reach >160dB, indicating that coherent optical signals have obvious advantages over incoherent light in the field of signal processing.

[0139] When spatially modulating incoherent pump light, the system can use grating projection to create a structured effect, or a spatial light modulator (SLM) that dynamically controls the amplitude, phase, or polarization of the light wave. Devices that can also achieve spatial modulation include digital micromirror devices (DMDs).

[0140] 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.

[0141] The system can be added to a spatial light field relay system, which helps to eliminate the problem of low modulation depth caused by the Talbot effect during light transmission.

[0142] The system can incorporate a codeable unconventional aperture stop to help restore high spatial resolution while effectively suppressing the effects of stray light.

[0143] It should be noted that the aforementioned explanation of the embodiment of generating and converting coherent light signals based on stimulated emission of radiation also applies to the Fourier aperture-coded microscopy method based on stimulated emission of radiation in this embodiment. By sequentially illuminating a sample with a sequenced stimulated emission light field, light field information at multiple different viewing angles is collected, and further synthesis of high spatial resolution, large field-of-view microscopic images can be achieved. This description will not be repeated here. The method for generating coherent light signals by stimulated emission of radiation in this application is applicable not only to the field of ultrafast optics but also to other optical fields.

[0144] 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 an embodiment of the present invention, the incoherent optical signal carrying the target information is converted into a coherent optical signal by generating stimulated radiation by means of a pump-probe method, and the processing of the target information is realized by utilizing the differences in time and space dimensions. Therefore, the embodiment of the present invention realizes the transmission of target information on incoherent light to coherent optical signals through stimulated emission technology, fully utilizes the coherence of stimulated emission optical signals, and can be used for coherent optical information processing.

[0145] 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 each module 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 using the optical information processing module. The above-mentioned whole process requires the management of the pulse synchronization timing control module.

[0146] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" mean 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 any one or more embodiments or examples in an appropriate manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless otherwise clearly defined. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this application, "N" means at least two, for example, two, three, etc., unless otherwise clearly defined.

[0147] 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 be performed out of 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 those skilled in the art to which the embodiments of the present application belong.

[0148] The logic and / or steps represented in a flowchart or otherwise described herein, for example, can be considered a sequenced list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" is any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (not exhaustive) of computer-readable media include: an electrical connection with one or more wires (electronic devices), a portable computer disk cartridge (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and a portable compact disc read-only memory (CDROM). Furthermore, 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 it in another suitable manner if necessary, and then storing it in a computer memory.

[0149] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiment, the N steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having logic gate circuits for implementing logical functions on data signals, an application-specific integrated circuit having suitable combinational logic gate circuits, a programmable gate array (PGA), a field-programmable gate array (FPGA), etc.

[0150] The present invention provides a system and method for generating and converting coherent optical signals based on stimulated emission of radiation. Numerous methods and approaches exist for implementing this technical solution. The foregoing description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using 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 and target information modulation module with incoherent characteristics, a probe light field preparation module, a stimulated radiation material generation 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 on 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 emission material generates a stimulated emission light signal module for generating a stimulated emission 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, 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 emission substance to achieve the effect of stimulating the stimulated emission substance; Step 2: The probe light field preparation module generates a high-intensity probe light field using a high-power and high-coherence laser light source. The spectrum of the probe light field must coincide with the radiation spectrum of the stimulated emission material to produce the strongest stimulated emission 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 generate stimulated radiation. 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 includes 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 , temporal modulation is applied by a chopper or electro-optic modulator, and the modulated pump light 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 modulating signal; Step a2: Applying the probe light field Then stimulated emission of radiation is generated: the modulated pump light excites the gain medium, and the stimulated emission of radiation light field ,in is the stimulated emission cross section of the stimulated emission material, is the number density of particles at 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: ; Step a3, demodulating the transmitted time code information: When using the phase-locked amplification method to demodulate, 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 and receiving signals 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 emission and is expressed as: ， The peak position of the spectrum of the demodulated signal directly reflects the modulation frequency, realizing time information decoding. Through the stimulated emission process, the time information modulated on the incoherent pump light is converted into the phase or amplitude change of the coherent light signal emitted by the stimulated emission process. The modulated time information is then 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 includes 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 , to achieve spatial information modulation, expressed as: ， Under the condition that the wavelength of the pump light with incoherent characteristics 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 pump light with incoherent characteristics, namely the sinusoidal fringes ; Step b3, processing the information carried in the stimulated emission 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, applying a sinusoidal stripe periodically distributed in the x direction to the incoherent light field 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; 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 Filter out the signal and only retain 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 stripes with periodic distribution in the x direction 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 used, the time information is modulated onto the pump light with incoherent characteristics through the electro-optical modulator (AOM). The accuracy of the time encoding needs to be less than the excited state lifetime of the stimulated emission 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 used, the photodetector has a time resolution capability of not less than 1 ps. At the same time, combined with the phase-locked amplification method, the causal relationship between the coded signal and stimulated emission is utilized to achieve target signal reconstruction; 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 the data collected by the photodetector.

9. The method according to claim 8, characterized in that Steps 1 to 4 all operate under the control of the signal triggering and synchronization control module. The signal triggering and synchronization control module controls the generation time and sequence of the incoherent pump light and probe light field through photoelectric signals, and controls the optical path difference between the incoherent pump light and probe light field through optical delay lines. After the stimulated emission light signal is processed, the target information is jointly processed in combination with the time coordinates recorded by the signal triggering and synchronization control module.

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 is caused to perform the steps of the method according to claim 2 .

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