CN114578627A - Nonlinear optical coupling modulation method based on adiabatic shortcut - Google Patents

Nonlinear optical coupling modulation method based on adiabatic shortcut Download PDF

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CN114578627A
CN114578627A CN202210103811.9A CN202210103811A CN114578627A CN 114578627 A CN114578627 A CN 114578627A CN 202210103811 A CN202210103811 A CN 202210103811A CN 114578627 A CN114578627 A CN 114578627A
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陈长水
韦焯航
张忠昊
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South China Normal University
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
    • G02F1/3534—Three-wave interaction, e.g. sum-difference frequency generation
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
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    • G02F1/355—Non-linear optics characterised by the materials used
    • G02F1/3551—Crystals

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Abstract

The invention discloses a nonlinear optical coupling modulation method based on adiabatic shortcut, which is used for realizing the high-efficiency conversion of signal light to output light and comprises the following steps of (1) calculating a heat-reflecting term in frequency conversion based on the adiabatic shortcut theory; (2) designing a modulation function of a coupling parameter in a cascade wavelength conversion process and a diathermy compensation method; (3) selecting and modulating a laser light source and a nonlinear crystal; (4) the process of converting the signal light to the output light is realized. The method is based on the adiabatic shortcut theory, is a scheme for realizing efficient secondary cascade nonlinear optical frequency conversion by modulating crystal parameters, reduces the limit of modulation parameters and pumping light intensity in adiabatic conversion to meet adiabatic conditions, and realizes multi-process quasi-phase matching in the nonlinear crystal by using a quasi-phase matching technology according to a designed coupling parameter modulation function so as to obtain efficient frequency conversion from signal light to output laser.

Description

Nonlinear optical coupling modulation method based on adiabatic shortcut
Technical Field
The invention relates to the field of novel light source acquisition, in particular to a nonlinear optical coupling modulation method based on adiabatic shortcut, which is used for generating laser light sources with different wave bands required in different fields of military affairs, environmental detection and the like.
Background
The light source with specific wave band has no alternative function in some fields, however, the light wave band capable of directly outputting laser through the laser working substance is limited, and the method of nonlinear frequency conversion is needed for obtaining laser with some wave bands. In order to realize efficient frequency conversion of the light source and obtain a new light source, the conversion process needs to satisfy the phase matching condition. At present, two methods for obtaining a new light source by using a nonlinear crystal to perform light source frequency conversion are mainly used, namely an angle phase matching technology and a quasi-phase matching technology. The technical method realizes high-efficiency light-light nonlinear frequency conversion, which needs to meet specific conditions, and the incident angle of input light and the parameters of nonlinear medium materials, such as temperature, length and the like, can affect phase matching, thereby seriously reducing the light-light conversion efficiency. How to design a suitable nonlinear crystal remains a hot point in the field.
In 2008, teaching Haim Suchowski, the adiabatic condition corresponding to the realization of nearly complete quantum conversion efficiency is theoretically given according to the fast adiabatic channel (RAP) scheme in atomic population transfer. A modulation scheme of the nonlinear crystal is designed, and experimental verification is carried out. The adiabatic evolution theory of the atomic physics field is introduced for the first time in the nonlinear optics field, so that the output light of high-efficiency frequency conversion is obtained through a sum frequency process.
The wavelength of the new frequency band obtained through a single three-wave mixing process is limited by the wavelengths of the pumping light and the signal light, the selection requirements of the wavelengths of the pumping light and the signal light are strict, the requirements of the existing laser cannot be met frequently, and the degree of freedom of the conversion process is not high. In 2012, Gil Porat et al proposed an adiabatic secondary cascade frequency conversion scheme, which is based on the stimulated raman adiabatic channel theory, effectively solves the problem of low degree of freedom in a single three-wave mixing process, and has high conversion efficiency. And the nonlinear crystal is modulated by designing a phase reversal quasi-phase matching technology in the next year, and the intermediate infrared laser is generated efficiently through a cascade difference frequency process experimentally. The frequency conversion scheme corresponding to the stimulated Raman adiabatic channel theory requires that the delay parameter meets the inverse visual coupling order and the coupling parameter meets the corresponding adiabatic condition, and has a plurality of limitations on the modulation mode of the crystal and the intensity of the pump light.
Another theory for atomic population transmission, stimulated Raman adiabatic shortcut theory, is a method for compensating adiabatic driving terms by stimulated Raman technology, and the frequency of the link ground state and the excited state is wp1And linking the excited and target states at a frequency wp2The pulse shape of the stokes pulse of (a) is adiabatically modified such that even if the original pulse parameters have a certain amount of shifted adiabatic conversion conditions, the same population distribution as the particles in the final energy state under adiabatic evolution is achieved and almost no particles remain in the excited state throughout the process, thereby completing a complete population transfer between the ground state and the target state.
Disclosure of Invention
The invention aims to provide a nonlinear optical coupling modulation method based on adiabatic shortcut, which is used for realizing the efficient conversion of signal light to output light, the method is based on the adiabatic shortcut theory, is a scheme for realizing the efficient secondary cascade nonlinear optical frequency conversion by modulating crystal parameters, reduces the limit of the modulation parameters and the pumping light intensity in the adiabatic conversion to meet the adiabatic condition, and realizes multi-process quasi-phase matching in a nonlinear crystal by utilizing a quasi-phase matching technology according to a designed coupling parameter modulation function so as to obtain the efficient frequency conversion from the signal light to the output laser.
The above object of the present invention is achieved by the following technical solutions:
a nonlinear optical coupling modulation method based on adiabatic shortcut is characterized by comprising the following steps:
(1) calculating anti-diathermy terms in frequency conversion based on adiabatic shortcut theory;
(2) designing a modulation function of a coupling parameter in a cascade wavelength conversion process and a diathermy compensation method;
(3) selecting and modulating a laser light source and a nonlinear crystal;
(4) the process of converting the signal light to the output light is realized.
The invention designs a group of new coupling functions based on the adiabatic shortcut theory, and realizes the modulation meeting the coupling functions in the nonlinear crystal by utilizing the quasi-phase matching technology, so that the multi-process quasi-phase matching and the required coupling parameter modulation are realized. The method can solve the problem that the high-efficiency conversion cannot be realized in the adiabatic secondary cascade nonlinear frequency conversion process due to the diathermy process, relieve the requirements on the modulation parameters of the crystal, reduce the requirements on the intensity of the pumping light in the high-efficiency frequency conversion process and realize the high-efficiency frequency conversion from the signal light to the output laser.
In the invention, the specific process of the step (1) is as follows:
the second-order cascade optical frequency conversion comprises two three-wave mixing processes and is described by the following kinetic equation system
Figure BDA0003492052330000021
Wherein A (z) ═ A1 A2 A3]TRepresenting the amplitude of the respective light field, where A1Represents the optical field of the signal light, A2Represents an intermediate light field, A3Representing the output light field, i represents the imaginary unit, z represents the transmission distance of light in the nonlinear crystal, and the transformation matrix in the kinetic equation can be expressed as follows
Figure BDA0003492052330000031
Wherein:
Figure BDA0003492052330000032
Figure BDA0003492052330000033
Figure BDA0003492052330000034
is the coupling parameter between the light fields j and l,
in the expression of coupling parameters
Figure BDA0003492052330000037
The signs represent different processes, where-represents sum frequency process, + represents difference frequency process,
Figure BDA0003492052330000035
representing the conjugate of the coupling parameter, where j, l take different values-1, 2, 3, representing the signal, intermediate and output fields, χ, respectively(2)Represents the second order nonlinear coefficient of the crystal, Ap1Representing the field amplitude of the pump field during the first three-wave mixing, A2Representing the amplitude of the pump light field during the second three-wave mixing, w being the frequency of the light and the phase mismatch Δ ki＝ki±kpi-ki+1+2π/Λi(i ═ 1, 2), the ± signs in the detuning quantity represent different processes, where + represents the sum frequency process, -represents the difference frequency process, kj＝wjn(wj) C is wave vector, c is light speed in vacuum, n represents refractive index of light with different wave bands in the crystal, wherein 2 pi/lambdaiIs a reciprocal lattice vector, Λ, produced by modulating a crystal by a quasi-phase techniqueiIn order to adjust the period of the crystal,
after modulation by the quasi-phase matching technique, the modulated crystal can completely compensate detuning, and the time is delta k1＝Δk2The coupling modulation function of the crystal and the light in the frequency conversion scheme based on the stimulated raman adiabatic channel which has been proposed so far satisfies the following expression
Figure BDA0003492052330000036
Wherein, k'12Indicating strong coupling of signal light and intermediate light in frequency conversion schemes based on stimulated Raman adiabatic channelsDegree modulation rule, k'32Represents the modulation law of the coupling intensity of intermediate light and output light based on the stimulated Raman adiabatic channel, s1Representing the amount of coupling delay in the first three-wave mixing process, d1Span of a Gaussian coupling function, s, representing the first process2Representing the amount of coupling delay in the second three-wave mixing process, d2Representing the span of the second process Gaussian coupling function, under the assumption of phase matching, integrating partial differential equations describing intermediate light with the initial condition of the intermediate light intensity being zero, and substituting into two cascaded kinetic equations, thereby simplifying the set of coupling equations comprising three light fields to a set of kinetic equations that can be represented by only a second-order matrix comprising signal light and output light by
Figure BDA0003492052330000041
Calculating the inverse diathermy term, McdIs a Hamiltonian representation of the diathermic term, where | n>Is the eigenstate of the second order conversion matrix of the simplified post-coupling system of equations described above,<n | represents the left vector of the eigenstates,
Figure BDA0003492052330000042
representing the derivation of the distance to the eigenstates, Σ representing the sum over all eigenstates, i is an imaginary unit, and the corresponding Hamilton value of the anti-diathermy drive term for the conversion from signal light to output light during adiabatic conversion is in the form
Figure BDA0003492052330000043
The specific expression of the non-diagonal terms in (1) is
Figure BDA0003492052330000044
The dots symbolically marked in the formula represent the partial derivatives of the distance.
In the invention, the specific process of the step (2) is as follows:
according to adiabatic shortcut theory, namely, after adding anti-adiabatic driving to the system Hamilton quantity, under the condition of obtaining another interaction expression through rotation transformation, a modulation function capable of compensating diathermy based on the stimulated Raman process frequency conversion process is designed, namely, the modulation function based on adiabatic shortcut is as follows,
Figure BDA0003492052330000045
Figure BDA0003492052330000046
wherein:
Figure BDA0003492052330000047
Φ＝arctan(ka/k′12)
Figure BDA0003492052330000048
representing the change rule of the coupling strength of the signal light field and the intermediate light field based on adiabatic shortcut;
Figure BDA0003492052330000049
representing the law of change of the coupling strength of the output light field and the intermediate light field based on adiabatic shortcut.
In the invention, the specific process of the step (3) is as follows:
based on the adiabatic frequency conversion requirement, the coupling strength is required to be large enough corresponding to the optically twice cascaded adiabatic wavelength conversion, i.e. the power of the laser pumping light source is required to be large enough to ensure the adiabatic conversion process to be stably performed, so,
the pumping light source 1 is a nanosecond, picosecond or femtosecond light pulse light source;
the pumping light source 2 is a nanosecond, picosecond or femtosecond light pulse light source;
the signal light source can generally select a continuous, nanosecond, picosecond or femtosecond light pulse light source;
the nonlinear crystal is selected from LN, KTP, GaAs and the like, and the non-periodic or non-periodic quasi-phase matching structure crystal (hereinafter referred to as a structure crystal) for realizing the coupling parameter modulation is realized through electric field polarization or domain inversion.
In the invention, the specific process of the step (4) is as follows:
in a nonlinear crystal in which two beams of pump light with different wavelengths and one beam of signal light are simultaneously and vertically incident and modulated, the first beam of pump light and the first beam of signal light generate a three-wave frequency mixing process in the crystal, and the change rule of the coupling intensity between the two light fields is that
Figure BDA0003492052330000051
The generated intermediate light and the second beam of pump light simultaneously generate a second three-wave mixing process, and the change rule of the coupling intensity is
Figure BDA0003492052330000052
Thereby producing a final output light in which the signal light is completely converted into the output light.
As a preferred embodiment of the present invention:
signal light wavelength lambda11064nm, light intensity of 100MW/cm2；
First beam of pump light wavelength λp12800nm with a light intensity of 700MW/cm2；
Second beam pump light wavelength λp22900nm, light intensity of 1.6GW/cm2；
The intermediate optical wavelength λ 2 is 1716nm, and the output optical wavelength λ 3 is 1078 nm.
The nonlinear optical coupling modulation method based on adiabatic shortcut redesigns the coupling function and modulates the parameters of the structural crystal by calculating the diathermy item in the secondary cascade frequency adiabatic coupling modulation function based on the stimulated Raman adiabatic channel proposed by the predecessor, so that the interaction (coupling) intensity of light in the crystal meets the designed modulation function along the transmission direction after the corresponding wavelength is input, thereby realizing efficient secondary cascade adiabatic frequency conversion, the limitation of system parameters (such as delay parameters, pumping light intensity and the like) is broken, the wave band of the output light almost covers all wave bands transmitted by the corresponding crystal, and different output wave bands can be obtained by modulating different crystal parameters and selecting proper pumping and signal light wavelength.
Drawings
The invention is described in further detail below with reference to the figures and specific embodiments.
FIG. 1 is a schematic diagram of coupling strength of a nonlinear optical coupling modulation method based on adiabatic shortcut in accordance with the present invention, wherein the abscissa is the crystal length and the ordinate is the normalized coupling strength;
FIG. 2 is a diagram showing the light intensity variation of input light, intermediate light and output light in the crystal length direction in the adiabatic shortcut-based nonlinear optical coupling modulation method of the present invention;
FIG. 3 is a schematic diagram of a crystal structure of the modulation method based on adiabatic shortcut nonlinear optical coupling.
Detailed Description
The invention relates to a nonlinear optical coupling modulation method based on adiabatic shortcut, which realizes efficient conversion from 1064nm to 1078nm in wavelength by a lithium niobate crystal subjected to non-periodic electric field polarization modulation, and a secondary cascade schematic diagram is shown in figure 1. Firstly, by calculating a modulation crystal coupling function and then processing the crystal, the corresponding laser can automatically meet the conditions required by the adiabatic process when passing through the crystal, and the laser of a new frequency band is output.
The coupling modulation method comprises the following specific steps:
calculating a coupling intensity modulation function which meets the requirement and is based on adiabatic shortcut, wherein the functions are respectively as follows:
Figure BDA0003492052330000061
Figure BDA0003492052330000062
wherein
Figure BDA0003492052330000063
Φ＝arctan(ka/k′12)
Figure BDA0003492052330000064
Figure BDA0003492052330000065
Wherein k is12(z) describes the variation law of the coupling strength of the third three-wave mixing process in the secondary cascade wavelength conversion along the propagation direction z, wherein the constant term k12Representing the magnitude, k, of the coupling parameter of the first conversion process in an unmodulated crystal23(z) is the coupling strength, k, of the second three-wave mixing process in the second cascaded wavelength conversion along the propagation direction z23Representing the magnitude of the coupling parameter of the second conversion process in the unmodulated crystal. Determining a coupling delay parameter s in the first three-wave mixing process according to a delay parameter and a span parameter required for complete conversion in analog calculation10.01m, span parameter d1＝0.00007m2Second coupling delay parameter s in three-wave mixing process20.01m, span parameter d2＝0.00009m2，
The modulation of the coupling intensity in the crystal direction is realized by the above function, and the condition of the input light meeting the requirement of complete conversion is as follows
Signal light wavelength lambda11064nm, light intensity of 100MW/cm2；
Pump light 1 wavelength lambdap12800nm with a light intensity of 700MW/cm2；
Pump light 2 wavelength lambdap22900nm, light intensity of 1.6GW/cm2；
The intermediate optical wavelength λ 2 is 1716nm, and the output optical wavelength λ 3 is 1078 nm.
In the secondary cascade difference frequency process, the phase mismatch quantities corresponding to the two three-wave mixing frequencies are respectively as follows:
Δk1＝kλ1-kλ2-kp1+2π/A1，
Δk2＝kλ2-kλ3-kp2+2π/A2，
kj＝njwj/c。
wherein, Δ k1For the second cascade wavelength conversion, the amount of phase mismatch, Δ k, of the first difference frequency process2For the phase mismatch amount, k, of the second three-wave mixing process (i.e. sum frequency process)jIs wave number, where kp1Is the wave number, k, of the pump light in the first conversion processp2Is the wave number, k, of the pump light in the second conversion processλ1Is the wave number, k, of the signal lightλ2Wave number, k, of intermediate lightλ2The wave number of the output light contains the crystal modulation period Lambda1And Λ2The term (b) serves to compensate for phase detuning due to material dispersion. In the formula, the refractive index njCalculated by a dispersion equation, the set temperature is 100 ℃, c is the speed of light in vacuum, and wj(j ═ 1, 2, 3) represents the optical field frequency.
The magnesium oxide-doped lithium niobate crystal with high laser damage resistance threshold is selected.
In this embodiment, the non-linear crystal is a magnesium oxide doped Lithium Niobate (LN) crystal with a high laser damage resistance threshold, the direction with a non-linear coefficient d33 ═ 28pm/V is used as the optical axis direction, and the non-periodic or non-periodic quasi-phase matching structure of the coupling parameter modulation is realized by electric field polarization with intensity higher than or slightly lower than 2 kV/mm. An electric field signal is selected having a spatial form,
F(z)＝sign[-cos(πD1)+cos(2πz/Λ1)]×sign[-cos(πD2)+cos(2πz/Λ2)]
wherein Di＝l+/(l++l-) Crystal modulation duty cycle of period i,/+And l-Representing the lengths of the crystalline positive and negative domains, respectively. The first order approximation term of the fourier series of the modulation function selected corresponds to an amplitude modulation term of the form:
f1(z)＝(2D2-1)sin(πD1)
f2(z)＝(2D1-1)sin(πD2)
and Di represents the duty ratio of crystal modulation, and the optimal duty ratio arrangement in the propagation direction is calculated by a genetic algorithm, so that the two amplitude modulation terms f1(z) and f2(z) respectively satisfy the coupling parameter modulation function of the first process and the coupling parameter modulation function of the second process which are designed based on the adiabatic shortcut theory. And satisfy Λ1＝Δk1，Λ2＝Δk2。
Two beams of pumping light with different wavelengths of 2800nm and 2900nm and a beam of signal light with a wavelength of 1064nm are simultaneously and vertically incident into an electrically polarized and modulated lithium niobate crystal, the pumping light with the wavelength of 2800nm and the signal light with the wavelength of 1064nm firstly generate a difference frequency generation process in the crystal, a change rule of coupling intensity between the two light fields meets a coupling parameter modulation function of a first process designed based on an adiabatic shortcut theory, generated intermediate light and the pumping light with the wavelength of 2900nm simultaneously generate a sum frequency process, the change rule of the coupling intensity meets a coupling parameter modulation function of a second process designed based on the adiabatic shortcut theory, output light with the wavelength of 1078nm is obtained, the intermediate light with the wavelength of 1716nm is always in an extremely low state in the process, and the signal light is finally and completely converted into output light.
The above-described embodiments of the present invention are not intended to limit the scope of the present invention, and the embodiments of the present invention are not limited thereto, and various other modifications, substitutions and alterations can be made to the above-described structure of the present invention without departing from the basic technical concept of the present invention as described above, according to the common technical knowledge and conventional means in the field of the present invention.

Claims (5)

1. A nonlinear optical coupling modulation method based on adiabatic shortcut is characterized by comprising the following steps:
(1) calculating anti-diathermy terms in frequency conversion based on adiabatic shortcut theory;
(2) designing a modulation function of a coupling parameter in a cascade wavelength conversion process and a diathermy compensation method;
(3) selecting and modulating a laser light source and a nonlinear crystal;
(4) the process of converting the signal light to the output light is realized.
2. The adiabatic shortcut-based nonlinear optical coupling modulation method of claim 1, wherein the specific process of step (1) is as follows:
the second-order cascade optical frequency conversion comprises two three-wave mixing processes and is described by the following kinetic equation system
Figure FDA0003492052320000011
Wherein A (z) ═ A1 A2 A3]TRepresenting the amplitude of the respective light field, where A1Represents the optical field of the signal light, A2Represents an intermediate light field, A3Representing the output light field, i represents the imaginary unit, z represents the transmission distance of light in the nonlinear crystal, and the transformation matrix in the kinetic equation can be expressed as follows
Figure FDA0003492052320000012
Wherein:
Figure FDA0003492052320000013
Figure FDA0003492052320000014
Figure FDA0003492052320000015
is the coupling parameter between the light fields j and l,
in the expression of coupling parameters
Figure FDA0003492052320000017
The signs represent different processes, where-represents the sum frequency process, + represents the difference frequency process,
Figure FDA0003492052320000016
representing the conjugate of the coupling parameter, where j, l take different values-1, 2, 3, representing the signal, intermediate and output fields, χ, respectively(2)Represents the second-order nonlinear coefficient of the crystal,
Ap1representing the field amplitude of the pump field during the first three-wave mixing, A2Representing the amplitude of the pump light field during the second three-wave mixing, w being the frequency of the light and the phase mismatch Δ ki＝ki±kpi-ki+1+2π/Λi(i ═ 1, 2), the ± signs in the detuning quantity represent different processes, where + represents the sum frequency process, -represents the difference frequency process, kj＝wjn(wj) C is wave vector, c is light speed in vacuum, n represents refractive index of light with different wave bands in the crystal, wherein 2 pi/lambdaiIs a reciprocal lattice vector, Λ, produced by modulating a crystal by a quasi-phase techniqueiIn order to adjust the period of the crystal,
after modulation by the quasi-phase matching technique, the modulated crystal can completely compensate for detuning, in which case there is Δ k1＝Δk2The coupling modulation function of the crystal and the light in the frequency conversion scheme based on the stimulated raman adiabatic channel which has been proposed so far satisfies the following expression
Figure FDA0003492052320000021
Wherein, k'12Representing the coupled intensity modulation law, k ', of the signal light and the intermediate light in a frequency conversion scheme based on a stimulated Raman adiabatic channel'32Represents the modulation law of the coupling intensity of intermediate light and output light based on the stimulated Raman adiabatic channel, s1Representing the amount of coupling delay in the first three-wave mixing process, d1Span of Gaussian-type coupling function, s, representing the first process2Representing the amount of coupling delay in the second three-wave mixing process, d2Representing the span of the second process Gaussian coupling function, under the assumption of phase matching, integrating partial differential equations describing intermediate light with the initial condition of the intermediate light intensity being zero, and substituting into two cascaded kinetic equations, thereby simplifying the set of coupling equations comprising three light fields to a set of kinetic equations that can be represented by only a second-order matrix comprising signal light and output light by
Figure FDA0003492052320000022
Calculating the inverse diathermy term, McdIs a Hamiltonian representation of the diathermic term, where | n>Is the eigenstate of the second order conversion matrix of the simplified post-coupling system of equations described above,<n | represents the left vector of the eigenstates,
Figure FDA0003492052320000023
representing the derivation of the distance to the eigenstates, Σ representing the sum over all eigenstates, i is an imaginary unit, and the corresponding Hamilton value of the anti-diathermy drive term for the conversion from signal light to output light during adiabatic conversion is in the form
Figure FDA0003492052320000024
The specific expression of the non-diagonal terms in (1) is
Figure FDA0003492052320000025
The dots symbolically marked in the formula represent the partial derivatives of the distance.
3. The adiabatic shortcut-based nonlinear optical coupling modulation method of claim 1, wherein the specific process of step (2) is as follows:
according to adiabatic shortcut theory, namely, after adding anti-adiabatic driving to the system Hamilton quantity, under the condition of obtaining another interaction expression through rotation transformation, a modulation function capable of compensating diathermy based on the stimulated Raman process frequency conversion process is designed, namely, the modulation function based on adiabatic shortcut is as follows,
Figure FDA0003492052320000031
Figure FDA0003492052320000032
wherein:
Figure FDA0003492052320000033
Figure FDA0003492052320000034
representing the change rule of the coupling strength of the signal light field and the intermediate light field based on adiabatic shortcut;
Figure FDA0003492052320000035
representing the law of change of the coupling strength of the output light field and the intermediate light field based on adiabatic shortcut.
4. The adiabatic shortcut-based nonlinear optical coupling modulation method of claim 1, wherein the specific process of step (3) is as follows:
based on the requirement of adiabatic frequency conversion, corresponding to the requirement of optically twice cascading adiabatic wavelength conversion, the coupling strength is required to be large enough, namely the power of the laser pumping light source is required to be large enough to ensure that the adiabatic conversion process is stably carried out, so that the pumping light source 1 is a nanosecond, picosecond or femtosecond light pulse light source;
the pumping light source 2 is a nanosecond, picosecond or femtosecond light pulse light source;
the signal light source is a continuous, nanosecond, picosecond or femtosecond light pulse light source;
the nonlinear crystal is LN, KTP or GaAs, and the non-periodic or non-periodic quasi-phase matching structure crystal modulated by the coupling parameters is realized through electric field polarization or domain inversion.
5. The adiabatic shortcut-based nonlinear optical coupling modulation method of claim 1, wherein the specific process of step (4) is as follows:
in a nonlinear crystal in which two beams of pump light with different wavelengths and one beam of signal light are simultaneously and vertically incident and modulated, the first beam of pump light and the first beam of signal light generate a three-wave frequency mixing process in the crystal, and the change rule of the coupling intensity between the two optical fields is
Figure FDA0003492052320000036
The generated intermediate light and the second beam of pump light simultaneously generate a second three-wave mixing process, and the change rule of the coupling intensity is
Figure FDA0003492052320000037
Thereby producing a final output light in which the signal light is completely converted into the output light.
CN202210103811.9A 2022-01-27 2022-01-27 Nonlinear optical coupling modulation method based on adiabatic shortcut Pending CN114578627A (en)

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