Multimode chaotic laser generating device based on pumping modulation

Abstract

The utility model relates to the technical field of laser, in particular to a multimode chaotic laser generating device based on pumping modulation. The device comprises a resonant cavity, a 4-f telescope system, a gain medium, a pinhole diaphragm and a pumping source. The resonant cavity comprises a plane mirror and an output coupling mirror which are coaxially arranged; the 4-f telescope system is arranged in the resonant cavity and comprises a first thin lens and a second thin lens which are coaxially arranged; the gain medium is arranged between the plane mirror and the first thin lens; the small-hole diaphragm is arranged between the first thin lens and the second thin lens; the resonant cavity, the 4-f telescope system, the gain medium and the small-hole diaphragm are coaxial; the pumping source is arranged on the side edge of the gain medium and used for providing energy for laser generation. According to the invention, multi-transverse-mode resonance characteristics of the degenerate cavity and system instability induced by pumping modulation are combined, multi-mode laser output is realized from a space dimension, and chaotic output is realized from a time dimension.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser technology, in particular to a multimode chaotic laser generating device based on pump modulation. BACKGROUND

[0002] As a typical nonlinear optical phenomenon, chaotic laser has the characteristics of noise-like and wide spectrum, and has been applied in digital communication, random number generation and radar ranging. However, there are still the following problems in the application of chaotic laser, 1. The autocorrelation curve of the traditional external cavity chaotic laser contains obvious time delay characteristics, which is easy to be cracked by signal cracking, and the pseudo sidelobes generated in the correlation ranging will interfere with the distance determination, which limits its application in secure communication and laser ranging scenes; 2. The generated chaotic signal is a single signal, which is difficult to realize parallel output, and cannot meet the parallel demand of data transmission and the generation requirement of high-speed random bits of future communication system; 3. Due to the relaxation oscillation of the laser itself, the chaotic laser spectrum is not flat, and contains obvious relaxation oscillation characteristics, which limits the information transmission rate of secure communication.

[0003] Therefore, in view of the application fields of secure communication, laser ranging, optical random bit generation and the like, it is urgent to develop a parallel broadband chaotic laser generating device. SUMMARY

[0004] The present application aims at the above-mentioned problems and deficiencies, and provides a multimode chaotic laser generating device based on pump modulation, which can effectively solve the problems of relaxation oscillation and time delay tag in the current chaotic laser technology.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted is:

[0006] The present application provides a multimode chaotic laser generating device based on pump modulation, comprising:

[0007] a resonant cavity comprising a planar mirror and an output coupling mirror arranged coaxially;

[0008] a 4-f telescope system arranged in the resonant cavity, the 4-f telescope system comprising a first thin lens and a second thin lens arranged coaxially;

[0009] a gain medium arranged between the planar mirror and the first thin lens;

[0010] a pinhole diaphragm arranged between the first thin lens and the second thin lens, the resonant cavity, the 4-f telescope system, the gain medium and the pinhole diaphragm being coaxial;

[0011] and a pump source arranged at the side of the gain medium, the pump source being used for providing energy for the generation of laser.

[0012] According to the multi-mode chaotic laser generating device based on pump modulation, further, the first thin lens and the second thin lens are both circular and are both convex lenses.

[0013] According to the multi-mode chaotic laser generating device based on pump modulation, further, the back focal plane of the first thin lens and the front focal plane of the second thin lens are coincident to form a common focal plane.

[0014] According to the multi-mode chaotic laser generating device based on pump modulation, further, the pinhole diaphragm is arranged at the common focal plane.

[0015] According to the multi-mode chaotic laser generating device based on pump modulation, further, the plane mirror is arranged at the front focal plane of the first thin lens.

[0016] According to the multi-mode chaotic laser generating device based on pump modulation, further, the output coupling mirror is arranged at the back focal plane of the second thin lens.

[0017] According to the multi-mode chaotic laser generating device based on pump modulation, further, a calculation equation of the resonant frequency of the eigenmode of the resonant cavity is shown as formula 1,

[0018]

[0019] The v qmn is the resonant frequency of the eigenmode of the resonant cavity, the q is the longitudinal mode number of the eigenmode of the resonant cavity, the m is a transverse mode number of the eigenmode of the resonant cavity, the n is another transverse mode number of the eigenmode of the resonant cavity, the c is the speed of light in vacuum, the L is the optical length of the resonant cavity, the A is the linear magnification of the eigenmode of the resonant cavity, and the D is the angular magnification of the eigenmode of the resonant cavity.

[0020] According to the multi-mode chaotic laser generating device based on pump modulation, further, a transformation matrix of the resonant cavity system is shown as matrix ①,

[0021]

[0022] wherein M1 is a forward transmission transformation matrix of the system from the plane mirror to the output coupling mirror in the resonant cavity, M2 is a reverse transmission transformation matrix of the system from the output coupling mirror to the plane mirror in the resonant cavity, A is the linear magnification, B is the transmission length, C is the optical power, and D is the angular magnification.

[0023] According to the multi-mode chaotic laser generating device based on pump modulation, further, the forward transmission transformation matrix M1 of the system from the plane mirror to the output coupling mirror in the resonant cavity is shown as matrix ②,

[0024]

[0025] Wherein, A1 is the linear magnification in the forward transmission, B1 is the transmission length in the forward transmission, C1 is the optical power in the forward transmission, D1 is the angular magnification in the forward transmission.

[0026] According to the multi-mode chaotic laser generation device based on pump modulation, further, the reverse transmission transformation matrix M2 from the output coupling mirror to the plane mirror in the resonant cavity is shown as matrix ③,

[0027]

[0028] Wherein, A2 is the linear magnification in the reverse transmission, B2 is the transmission length in the reverse transmission, C2 is the optical power in the reverse transmission, D2 is the angular magnification in the reverse transmission.

[0029] The above technical scheme has the beneficial effects of:

[0030] The present application has simple overall structure and ingenious design. The present application combines the multi-transverse mode resonance characteristics of the degenerate cavity and the system instability induced by pump modulation, realizes multi-mode laser output from the spatial dimension and chaotic output from the time dimension, and the laser generated by the generation device can be used for secure communication, parallel random bit generation and chaotic laser three-dimensional imaging.

[0031] The present application starts from the modulation of the pump source, increases the third degree of freedom-modulation current, controls the chaotic dynamics of the pump system through the modulation depth and modulation angular frequency, adjusts the mode number through the degenerate cavity structure and the variable aperture diaphragm, and breaks through the defects of the limited parameter range and the difficulty in controlling of the traditional scheme for generating chaos by using optical mode beat frequency parameters, expands the chaotic dynamics to the field of external electrical parameter control, and realizes electrical control of the chaotic dynamics. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments of the present application will be briefly introduced below. Among them, the drawings are only used to show some embodiments of the present application, and not to limit all embodiments of the present application to this.

[0033] Figure 1 is the structure schematic diagram of the multi-mode chaotic laser generation device based on pump modulation of the embodiment of the present application;

[0034] Figure 2 is the time sequence of the i-th mode output obtained by simulation and simulation of the embodiment of the present application;

[0035] Figure 3This is the Lyapunov index spectrum of the i-th mode obtained by simulation in an embodiment of the present invention;

[0036] Figure 4 This is the power spectrum of the i-th mode obtained through simulation in an embodiment of the present invention;

[0037] Figure 5 It is the autocorrelation spectrum of the i-th mode obtained by simulation in an embodiment of the present invention.

[0038] The numbers in the diagram represent the following meanings:

[0039] 1. Plane mirror, 2. Gain medium, 3. Pump source, 4. Positive conductor, 5. Negative conductor, 6. Modulation current source, 7. First thin lens, 8. Pinhole aperture, 9. Second thin lens, 10. Output coupling mirror. Detailed Implementation

[0040] The exemplary solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art.

[0041] like Figure 1 As shown, the pump-modulated multimode chaotic laser generator of this embodiment includes a resonant cavity, a 4-f telescope system, a gain medium 2, a pinhole aperture 8, and a pump source 3. A plane mirror 1 and an output coupling mirror 10 are coaxially arranged within the resonant cavity; the 4-f telescope system is disposed within the resonant cavity and includes a first thin lens 7 and a second thin lens 9 coaxially arranged; the gain medium is disposed between the plane mirror 1 and the first thin lens 7; the pinhole aperture is disposed between the first thin lens 7 and the second thin lens 9; the resonant cavity, the 4-f telescope system, the gain medium, and the pinhole aperture are coaxially arranged; the pump source 3 is disposed on the side of the gain medium 2 and is used to provide energy for laser generation.

[0042] The resonant cavity composed of the plane mirror 1 and the output coupling mirror 10 extends the working length of the gain medium 2 by reflecting light back and forth within the cavity.

[0043] The first thin lens 7 and the second thin lens 9 form a 4-f telescope system, which enables the light field of the plane mirror 1 to be self-reproduced on the output coupling mirror 10 after a single-pass transit, reducing the diffraction loss of higher-order modes and enabling the cavity to support multi-transverse mode resonance.

[0044] The pinhole aperture 8 performs loss regulation on the transverse modes in the spectral plane to control the number of transverse modes.

[0045] Gain medium 2 is used to achieve population inversion and increase optical energy density, while also determining the wavelength of the laser.

[0046] The pump source 3 acts as an energy source, which emits photons to pump the electrons in the gain medium 2 from the ground state to high energy levels to achieve population inversion.

[0047] The modulated current source 6 generates a modulated current to modulate the output power of the pump source 3.

[0048] Further, the surface of the plane mirror 1 is coated with a high reflectivity film layer for light of the laser wavelength. The reflectivity of the high reflectivity film layer is >99.9%.

[0049] Optionally, the laser wavelength is 808nm, 1064nm or 1550nm. Optionally, the plane mirror 1 is a circular mirror with a diameter of 25.4cm or 50.8cm.

[0050] Optionally, the gain medium 2 is in a cylindrical or cuboid shape.

[0051] Optionally, the gain medium 2 can be a solid gain medium doped with neodymium ions (Nd 3+ ) such as neodymium-doped yttrium aluminum garnet laser crystal (Nd:YAG), neodymium-doped yttrium lithium fluoride crystal (Nd:YLF), neodymium-doped yttrium vanadate crystal (Nd:YVO4), etc., with a concentration of 0.8at%-1.2at% and a thickness of 1-3mm. Alternatively, the gain medium 2 can be a semiconductor quantum well material.

[0052] Optionally, the pump source 3 can be a semiconductor laser, an arc lamp, a diffuse light lamp, etc.

[0053] Optionally, the gain medium 2 and the pump source 3 are arranged together between the thin lens 7 and the pinhole diaphragm 8, or between the pinhole diaphragm 8 and the thin lens 9, or between the thin lens 9 and the output coupling mirror 10.

[0054] Optionally, the pinhole diaphragm 8 can be a circular diaphragm, a square diaphragm, etc., and its aperture is continuously adjustable in the range of 0mm-10mm.

[0055] As shown in Figure 1 , the first thin lens 7 and the second thin lens 9 are both circular and are convex lenses.

[0056] Further, the focal length of the convex lens is 20cm or 30cm, the diameter is 25.4cm or 50.8cm, and the surface of the convex lens is coated with a high transmittance film layer for light of the laser wavelength. Further, the wavelength range here is 800nm-1600nm.

[0057] Optionally, the laser wavelength is 808nm, 1064nm or 1550nm.

[0058] Optionally, both the first thin lens 7 and the second thin lens 9 are plano-convex lenses or biconvex lenses.

[0059] The rear focal plane of the first thin lens 7 and the front focal plane of the second thin lens 9 are superimposed to form a common focal plane, and the pinhole aperture is set at this common focal plane.

[0060] like Figure 1 As shown, the plane mirror 1 is positioned at the front focal plane of the first thin lens 7, and the output coupling mirror 10 is positioned at the rear focal plane of the second thin lens 9.

[0061] Optionally, the reflection:transmission splitting ratio of the output coupling mirror 10 can be selected as 5:5, 6:4, or 7:3, etc., and the surface of the output coupling mirror 10 is coated with a reflective film and a transmission film for the laser wavelength. Further, the wavelength range here is 800nm ​​to 1600nm.

[0062] Optionally, the laser wavelength is 808nm, 1064nm or 1550nm.

[0063] Optionally, the output coupling mirror 10 is a circular component with a diameter of 25.4 cm or 50.8 cm.

[0064] like Figure 1 As shown, pump source 3 is connected to modulation current source 6 via positive electrode wire 4 and negative electrode wire 5. This forms an electrical connection circuit, enabling modulation current source 6 to supply power to pump source 3.

[0065] In this application, the equation for calculating the system forward transmission transformation matrix from the plane mirror to the output coupling mirror in the resonant cavity is shown in Equation 1.

[0066]

[0067] v qmn Let q be the resonant frequency of the intrinsic mode of the resonant cavity, q be the longitudinal mode number of the intrinsic mode of the resonant cavity, m be the transverse mode number of the intrinsic mode of the resonant cavity, n be the transverse mode number of the intrinsic mode of the resonant cavity, c be the speed of light in vacuum, L be the optical length of the resonant cavity, A be the linear magnification of the intrinsic mode of the resonant cavity, and D be the angular magnification of the intrinsic mode of the resonant cavity.

[0068] The cyclic transformation matrix of the resonant cavity system is shown in matrix ①.

[0069]

[0070] Where A is the linear magnification of the resonant cavity's intrinsic mode, B is the transmission length of the resonant cavity's intrinsic mode, C is the optical power of the resonant cavity's intrinsic mode, and D is the angular magnification of the resonant cavity's intrinsic mode.

[0071] The system forward transmission transformation matrix M1 from the plane mirror to the output coupling mirror in the resonant cavity is shown in matrix ②.

[0072]

[0073] Where A1 is the linear magnification in forward transmission, B1 is the transmission length in forward transmission, C1 is the optical power in forward transmission, and D1 is the angular magnification in forward transmission.

[0074] The forward and reverse transmission transformation matrix M2 of the system from the output coupler to the plane mirror in the resonant cavity is shown in matrix ③.

[0075]

[0076] Where A2 is the linear magnification in reverse transmission, B2 is the transmission length in reverse transmission, C2 is the optical power in reverse transmission, and D2 is the angular magnification in reverse transmission.

[0077] Based on matrices ①, ②, and ③, we can calculate that...

[0078]

[0079] Therefore, we can obtain: A = D = 1. Substituting this result into formula (1) yields: Therefore, the resonant frequency v of the eigenmode of the resonant cavity in this application is... qmn The frequency response depends only on the speed of light in vacuum (c), the optical length of the resonant cavity (L), and the longitudinal mode number (q), and is independent of the transverse mode numbers (m, n). This indicates that the resonant cavity supports independent oscillation of higher-order and lower-order transverse modes within the same longitudinal mode. The mode loss and the number of modes can be adjusted by changing the aperture size of the pinhole.

[0080] Under the modulation of pump source 2, the dynamic equation of the i-th mode in the multimode laser is shown in Equation 2.

[0081]

[0082] Among them, E i and G i τ represents the complex amplitude and particle number gain of the i-th laser mode, respectively. c τ represents the round-trip time in the laser cavity. f ω represents the fluorescence time of the gain medium. i p represents the detuning between the i-th laser mode and the center frequency. i α is the pump coefficient of the i-th laser mode. iis the mode loss coefficient of the ith laser mode, M is the pump modulation depth, and Ω is the modulation angular frequency. The difference between the modes is that the frequency detuning, the gain and the loss are different, the frequency detuning is determined by the matching degree of the resonator and the gain curve of the gain medium, and the gain and the loss are determined by the mode field area and the divergence angle of the mode.

[0083] Therefore, the third degree of freedom, i.e. the modulation current, is realized by modulating the pump coefficient of the pump source 2, and the system instability originally described by the amplitude and the population gain is caused, which constitutes the basis of generating chaotic dynamics.

[0084] Further, for the degenerate state, the round-trip transformation matrix M of the resonator system satisfies A+D=u, and u is an integer or an irreducible fraction. At this time, the resonator mode still satisfies the degenerate condition, and the multimode chaotic laser can still be generated by pump modulation.

[0085] According to the actual physical system parameters, the normalized pump coefficient p i =0.02, the round-trip time τ c =4ns, the fluorescence time τ f =240μs, ω i =0, the normalized mode loss coefficient α i =0.01, the modulation depth M=0.95, the modulation angular frequency Ω=1.4×10 5 rad / s, the simulation of the ith mode is carried out, and the results are shown in Figures 2-5 .

[0086] The time sequence of the output of the ith mode is shown in Figure 2 , and the time sequence presents obvious noise-like characteristics.

[0087] The Lyapunov exponent spectrum of the ith mode is shown in Figure 3 , wherein λ1>0, indicating that the output time sequence of the system is a chaotic sequence.

[0088] The power spectrum of the output of the ith mode is shown in Figure 4 , and the power spectrum presents a wide spectrum characteristic and does not contain obvious relaxation oscillation characteristics.

[0089] The autocorrelation spectrum of the output of the ith mode is shown in Figure 5 , and since the pump modulation is adopted, the autocorrelation spectrum does not contain the time delay characteristics.

[0090] The technical scheme of the present application is exemplarily described above in combination with the drawings, and obviously, the specific implementation of the present application is not limited by the above manner, and various non-essential improvements or direct application of the inventive concept and technical scheme to other occasions without improvement are within the protection scope of the present application.

[0091] In the description of the present application, the expression "first", "second" is used to describe various elements of the present application, and does not indicate any order, number or importance limitation, but only to distinguish one part from another.

[0092] It should be noted that when an element is in "connection", "coupling" or "connected" with another element, it can mean that it is directly connected, coupled or connected, but it should be understood that there can be intermediate elements between the two; that is, it covers the position relationship of direct connection and indirect connection.

[0093] It should be noted that the use of "one" or "a" and similar words does not necessarily mean a quantity limit. The words "including" or "containing" and similar words mean that the elements or objects appearing before the words cover the elements or objects listed after the words and their equivalents, and do not exclude other elements or objects.

[0094] It should be noted that the terms indicating the orientation or position relationship such as "up", "down", "left", "right" are only used to represent the relative position relationship, which is for the convenience of describing the present application, and the device or element referred to does not necessarily have a specific orientation, and is not necessarily constructed and operated in a specific orientation; When the absolute position of the described object changes, the relative position relationship may also change accordingly.

[0095] The preferred embodiments for implementing the present application have been described in detail above, but it should be understood that the role of these embodiments is only for example, and does not limit the scope, application or structure of the present application in any way. The scope of protection of the present application is defined by the appended claims and their equivalents. Those skilled in the art can make many changes to the foregoing embodiments under the teaching of the present application, and these changes all fall within the scope of protection of the present application.

Claims

1. A multi-mode chaotic laser generation apparatus based on pump modulation, characterized by, The resonant cavity comprises a plane mirror and an output coupling mirror arranged coaxially; A 4-f telescope system arranged in the resonant cavity, the 4-f telescope system comprising a first thin lens and a second thin lens arranged coaxially; A gain medium arranged between the plane mirror and the first thin lens; A pinhole diaphragm arranged between the first thin lens and the second thin lens, the resonant cavity, the 4-f telescope system, the gain medium and the pinhole diaphragm being coaxial; And a pump source arranged at the side of the gain medium, the pump source being used for providing energy for the generation of laser. The first thin lens and the second thin lens are both circular and convex.

2. The pump modulation based multimode chaos laser generating device according to claim 1, wherein The back focal plane of the first thin lens coincides with the front focal plane of the second thin lens to form a common focal plane.

3. The pump modulation based multimode chaos laser generating device according to claim 2, wherein The pinhole diaphragm is arranged at the common focal plane.

4. The pump modulation based multimode chaos laser generating device according to claim 3, wherein The plane mirror is arranged at the front focal plane of the first thin lens.

5. The pump modulation based multimode chaos laser generating device according to claim 2, wherein The output coupling mirror is arranged at the back focal plane of the second thin lens.

6. The pump modulation based multimode chaos laser generating device according to claim 5, wherein The calculation equation of the resonant frequency of the eigenmode of the resonant cavity is shown in Formula 1, 7. The pump modulation based multimode chaos laser generating apparatus according to claim 1, wherein The round-trip transfer matrix of the resonant cavity is shown in Matrix ①, （1） The v qmn is the resonant frequency of the eigenmode of the resonator, q is the longitudinal mode number of the eigenmode of the resonator, m is a transverse mode number of the eigenmode of the resonator, n is another transverse mode number of the eigenmode of the resonator, c is the speed of light in vacuum, L is the optical length of the resonator, A is the linear magnification of the round-trip transform matrix of the resonator, and D is the angular magnification of the round-trip transform matrix of the resonator.

8. The pump modulation based multimode chaos laser generating device according to claim 7, wherein Wherein, M1 is the forward transmission transfer matrix of the system from the plane mirror to the output coupling mirror in the resonant cavity, M2 is the reverse transmission transfer matrix of the resonant cavity from the output coupling mirror to the plane mirror, A is the linear magnification, B is the transmission length, C is the optical power, and D is the angular magnification. ① The forward transmission transfer matrix M1 of the system from the plane mirror to the output coupling mirror in the resonant cavity is shown in Matrix ②, 9. The pump modulation based multimode chaos laser generating device according to claim 8, wherein Wherein, A1 is the forward transmission linear magnification, B1 is the forward transmission length, C1 is the forward transmission optical power, and D1 is the forward transmission angular magnification. ② The reverse transmission transfer matrix M2 of the resonant cavity from the output coupling mirror to the plane mirror is shown in Matrix ③, 10. The pump modulation based multimode chaos laser generating apparatus according to claim 9, wherein Wherein, A2 is the linear magnification in the reverse transmission, B2 is the transmission length in the reverse transmission, C2 is the optical power in the reverse transmission, and D2 is the angular magnification in the reverse transmission. ③ ​

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