A mode-regulated laser based on a feshbach-like resonance

Abstract

The application discloses a mode regulation laser based on Feshbach resonance, and belongs to the technical field of lasers. The laser comprises a multimode gain module, a saturable absorption module, a Feshbach resonance tuning module and an output module arranged along an optical path in sequence. The multimode gain module provides optical signal energy and generates a multimode optical field; the saturable absorption module forms a pulse signal; the Feshbach resonance tuning module adjusts a polarization state through a polarization control part, changes reflectivity of different frequency components by using a frequency reflectivity curve tuning device, constructs a mode coupling channel and introduces Feshbach resonance; and the output module leads out the regulated laser signal. The application realizes directional distribution of gain among different modes through Feshbach resonance, regulates the output optical field mode from the perspective of active gain design, avoids energy loss in traditional optical field modulation, significantly improves energy utilization, and is especially suitable for high-power and multi-mode dynamic switching scenes, and can be applied to the fields of superfine processing and high-speed communication.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser technology, in particular to a mode regulation laser based on Feshbach resonance. BACKGROUND

[0002] Mode regulation is a key means to optimize the characteristics of the optical field in laser technology, and it is of great significance to laser applications. On the one hand, precise control of the mode distribution can suppress high-order mode interference, improve beam quality, and make the laser energy highly concentrated and the divergence angle smaller, meeting the needs of ultra-fine laser processing and other high-precision scenarios. On the other hand, through mode regulation, special light fields such as vortex beams can be generated, and their unique spiral phase can be used to expand the application boundary, for example, to realize multi-channel signal multiplexing to increase the communication transmission capacity and provide a possibility for breaking through the bandwidth bottleneck for 5G and future high-speed communication.

[0003] Existing mode regulation techniques are divided into two categories according to the action position: cavity-out regulation and cavity-in regulation. The widely used technical path is to directly intervene in the light field by means of a spatial light modulator and other devices. The core advantage of this method is the "direct manipulation" of the light field distribution, that is, the light field wavefront structure is precisely reshaped by loading a specific phase and amplitude modulation pattern. However, the "direct regulation" feature also has significant drawbacks: in essence, it is a "screening and modification" of the original light field. The unselected light field components (such as high-order modes and non-target phase components) will be lost due to diffraction, absorption, and other effects in the modulation process, resulting in a significant reduction in energy utilization and making it difficult to meet the needs of high-power, multi-mode dynamic switching scenarios. SUMMARY

[0004] In view of the problem of low energy utilization in the mode regulation process in the prior art due to "screening and modification" of the light field, the present application provides a mode regulation laser based on Feshbach resonance, which constructs a mode coupling channel through a cavity structure, introduces Feshbach resonance to realize directional distribution of gain among different modes, and realizes mode regulation from the perspective of active gain design, thereby improving energy utilization.

[0005] To achieve the above purpose, the present application provides a mode regulation laser based on Feshbach resonance, which includes a multi-mode gain module, a saturable absorption module, a Feshbach resonance tuning module, and an output module arranged in sequence along the optical path.

[0006] The multi-mode gain module is used to provide optical signal energy and generate a multi-mode light field; the saturable absorption module is used to form a pulse signal;

[0007] The Feshbach resonance tuning module cooperates with the multi-mode gain module to construct a coupling channel between modes and introduce Feshbach resonance, thereby realizing directional distribution of gain among different modes;

[0008] The output module is configured to output the regulated laser signal; and the Feshbach resonance tuning module is configured to make the different frequency gain curves and the mode gain curve of the multimode gain module satisfy a resonance relationship, so as to realize regulation of the mode distribution of the laser output light field.

[0009] Preferably, the multimode gain module, as a laser light signal energy source, comprises a pump source, a first collimator, a first reflector, a dichroic mirror, a second collimator and a multimode gain medium. The pump source provides energy required by the resonant cavity; the first collimator collimates the light beam emitted by the pump source; the first reflector adjusts the direction of the collimated pump light beam; the dichroic mirror combines the signal light beam and the pump light beam in the resonant cavity; the second collimator guides the combined light beam into the multimode gain medium; and the signal light beam and the pump light beam interact in the multimode gain medium to generate a multimode light field.

[0010] Preferably, the saturable absorption module is configured to provide a saturable absorption effect for the formation of the pulse signal and can be composed of a saturable absorber or an artificial saturable absorption component, and is configured to integrate the continuous light into a pulse light signal.

[0011] Preferably, the Feshbach resonance tuning module comprises a polarization control part and a frequency reflectivity curve tuning device; the polarization control part is configured to adjust the polarization state of the signal light in the resonant cavity; and the frequency reflectivity curve tuning device is configured to tune the reflectivity of different frequency components of the signal light in the resonant cavity to affect the gain curves of the different frequency components.

[0012] Preferably, the polarization control part comprises a 1 / 4 wave plate and a 1 / 2 wave plate, and the 1 / 4 wave plate and the 1 / 2 wave plate are arranged in sequence on the light path and are configured to cooperatively adjust the polarization state of the signal light.

[0013] Preferably, the frequency reflectivity curve tuning device is a position-adjustable reflector, which is configured to adjust the reflectivity of different frequency components by changing the resonant cavity length, and further affect the gain curves of the different frequency components. When the different frequency gain curves and the mode gain curve of the multimode gain medium satisfy a resonance relationship, a Feshbach-like resonance is formed, and the tuning of the mode proportion of the signal light is realized.

[0014] Preferably, the saturable absorber can be replaced by any component with a saturable absorption effect.

[0015] Preferably, the frequency reflectivity curve tuning device can be replaced by any component that can change the frequency reflectivity curve of the resonant cavity.

[0016] Preferably, the formation condition of the Feshbach-like resonance is that the frequency gain curve tuned by the frequency reflectivity curve tuning device and the mode gain curve of the multimode gain medium satisfy a resonance relationship, so that the modes in the multimode gain medium form a resonant pair and realize directional allocation of gain between the modes.

[0017] Preferably, the output module comprises a second mirror and an optical beam splitter; the second mirror is used to adjust the propagation direction of the signal light, and the optical beam splitter guides out the signal light in the resonant cavity as output laser light according to a preset ratio.

[0018] The working principle of the application is as follows: the pump light provided by the pump source is collimated by the first collimator, adjusted in direction by the first mirror, and then introduced into the multimode gain medium through the dichroic mirror; the signal light is generated in the multimode gain medium, and is formed into pulsed light by the saturable absorption module; after the pulsed light passes through the 1 / 4 wave plate and the 1 / 2 wave plate to adjust the polarization state, the reflectivity of different frequency components is changed by the frequency reflectivity curve tuning device; when the frequency gain curve after tuning by the frequency reflectivity curve tuning device meets the resonance relationship with the mode gain curve of the multimode gain medium, a Feshbach-like resonance is formed, the gain is directionally distributed among the modes, and thus the mode proportion of the signal light is tuned; finally, the signal light after regulation is output through the output module.

[0019] From the perspective of quantum mechanics, two modes of the multimode gain medium can be regarded as two energy levels of a two-level system, i.e., state and state (wherein, LP is linear polarization, LinearPolarization).

[0020] The Hamiltonian of the two-level system is as follows:

[0021] ;

[0022] wherein, is the photon number quantum, representing the photon number energy level in the optical field, and is a basic variable in the quantum mechanics model. is the angular frequency, representing the oscillation frequency of the optical field. is the energy level detuning, representing the energy level difference inside the two-level system, and is related to the mode gain curve. is the mode coupling constant, which has been defined by the formula, representing the coupling strength between modes.

[0023] The expression of the mode coupling constant can be derived from the eigenstate of the Hamiltonian as follows:

[0024] ;

[0025] wherein, is the frequency detuning. By adjusting the Feshbach resonance tuning module, the frequency reflectivity curve of the resonant cavity is coupled with the mode coupling, and thus mode selection can be realized. is the angle parameter, representing the direction angle of the polarization state of the optical field. is the saturation frequency or signal frequency. Reference frequency or fundamental frequency of resonant cavity.

[0026] Therefore, the application has the following beneficial effects:

[0027] (1) The application introduces Feshbach-like resonance through the resonant cavity, realizes directional distribution of gain among different modes, realizes mode regulation from the perspective of active gain design, avoids energy loss caused by "screening and modification" of light field in the prior art, and significantly improves energy utilization.

[0028] (2) The Feshbach resonance tuning module can flexibly tune the mode proportion, especially suitable for high-power and multi-mode dynamic switching scenarios, and expands the application range of the laser.

[0029] (3) The module structure in the application is reasonable, and the key components are replaceable, which reduces the difficulty of equipment debugging and maintenance, and has strong practicability.

[0030] The technical solutions of the application will be further described in detail below through the drawings and examples. DETAILED DESCRIPTION

[0031] Figure 1 is a module structure diagram of the application;

[0032] Figure 2 is a specific structure diagram of the application;

[0033] Figure 3 is a reflectivity curve diagram of the frequency reflectivity curve tuning device;

[0034] Figure 4 is a mode proportion effect diagram of Feshbach-like resonance tuning;

[0035] REFERENCE NUMERALS

[0036] 1-pump source, 2-first collimator, 3-first mirror, 4-dichroic mirror, 5-second collimator, 6-multimode gain medium, 7-saturable absorber, 8-1 / 4 wave plate, 9-1 / 2 wave plate, 10-frequency reflectivity curve tuning device, 11-second mirror, 12-optical splitter. DETAILED DESCRIPTION

[0037] The technical solutions of the application will be further described in detail below through the drawings and examples.

[0038] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the same meaning as those commonly understood by a person of ordinary skill in the art to which the present application belongs. The terms "first", "second", and similar terms are used herein merely to distinguish one element from another, and are not intended to imply any order or importance. The terms "include", "comprise", and similar terms are intended to mean that the elements listed after the terms encompass the elements recited and equivalents thereof, and do not exclude other elements. The terms "connected" and "coupled" are not limited to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect. The terms "upper", "lower", "left", "right", and similar terms are used merely to indicate relative positions, and can change accordingly when the absolute positions of the described objects are changed.

[0039] Embodiment

[0040] As shown in Figure 1 , the present application provides a mode control laser based on Feshbach resonance, which comprises a multimode gain module, a saturable absorption module, a Feshbach resonance tuning module and an output module.

[0041] As shown in Figure 2 , the multimode gain module comprises a pump source 1, a first collimator 2, a first mirror 3, a dichroic mirror 4, a second collimator 5 and a multimode gain medium 6. The pump source 1 is selected as a high-power semiconductor laser, and the output wavelength matches the absorption peak of the multimode gain medium 6; the first collimator 2 and the second collimator 5 are aspherical lenses, which are used to collimate the divergent light beam into a parallel light beam; the first mirror 3 is a high-reflectivity plane mirror, which is used to change the propagation direction of the pump light; the dichroic mirror 4 is highly transmissive to the pump light and highly reflective to the signal light, thereby realizing the beam combination of the pump light and the signal light; the multimode gain medium 6 is selected as a doped optical fiber or a crystal, which provides gain for the multimode light field.

[0042] The saturable absorption module adopts a saturable absorber 7, which is selected as graphene or carbon nanotube material, and uses the saturable absorption characteristics to shape the continuous light into a pulsed light signal. The pulse width can be controlled by adjusting the parameters of the saturable absorber 7.

[0043] The Feshbach resonance tuning module comprises a 1 / 4 wave plate 8, a 1 / 2 wave plate 9 and a frequency reflectivity curve tuning device 10. The 1 / 4 wave plate 8 and the 1 / 2 wave plate 9 cooperatively adjust the polarization state of the signal light, so that the polarization direction of the signal light matches the subsequent optical path; the frequency reflectivity curve tuning device 10 is a position-adjustable mirror, and the cavity length of the resonant cavity is changed by controlling the position of the frequency reflectivity curve tuning device 10 through a precision displacement stage, thereby tuning the reflectivity of different frequency components. The reflectivity curve is shown in Figure 3 .

[0044] The output module comprises a second mirror 11 and an optical beam splitter 12. The second mirror 11 is a high-reflectivity plane mirror for adjusting the propagation direction of the signal light; the splitting ratio of the optical beam splitter 12 is set to 1:9, wherein 10% of the light is output as the output laser light, and 90% of the light is returned to the resonant cavity to maintain oscillation.

[0045] The working process of the embodiment is as follows: the pump light emitted by the pump source 1 is collimated by the first collimator 2, reflected by the first mirror 3 to the dichroic mirror 4, focused into the multimode gain medium 6 by the second collimator 5 after being transmitted by the dichroic mirror 4, and excites the multimode gain medium 6 to generate signal light; the signal light oscillates in the resonant cavity, forms a pulsed signal after the saturable absorber 7, passes through the 1 / 4 wave plate 8 and the 1 / 2 wave plate 9 to adjust the polarization state, and is reflected by the frequency reflectivity curve tuning device 10, at this time, the cavity length is changed by adjusting the position of the frequency reflectivity curve tuning device 10, so that the gain curves of different frequencies and the mode gain curve of the multimode gain medium 6 meet the resonance relationship (as shown in Figure 4 The pulsed signal after regulation is reflected by the second mirror 11 to the optical beam splitter 12, and the optical beam splitter 12 guides 10% of the signal light out as output laser light.

[0046] Through the above-mentioned embodiments, dynamic regulation of the output mode of the laser can be realized, high-order mode interference can be suppressed or special light fields such as vortex beams can be generated, the energy utilization rate is improved by more than 30% compared with the traditional spatial light modulator regulation mode, and the method is suitable for ultra-fine processing, high-speed communication and other scenes.

[0047] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application rather than limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A mode-controlled laser based on a Feshbach-like resonance, characterized in that... It includes a multimode gain module, a saturable absorption module, a Feshbach resonance tuning module, and an output module arranged sequentially along the optical path; The multimode gain module is used to provide optical signal energy and generate a multimode optical field; the saturable absorption module is used to form a pulse signal. The Feshbach resonance tuning module works in coordination with the multimode gain module to construct coupling channels between modes and introduce Feshbach-like resonance to achieve directional distribution of gain between different modes. The Feshbach resonant tuning module includes a polarization control section and a frequency reflectivity curve tuning device. The polarization control section is used to adjust the polarization state of the signal light in the resonant cavity. The frequency reflectivity curve tuning device is used to tune the reflectivity of different frequency components of the signal light in the resonant cavity to affect the gain curve of different frequency components. The formation condition of Feshbach-like resonance is: the frequency gain curve after tuning by the frequency reflectivity curve tuning device and the mode gain curve of the multimode gain medium satisfy the resonance relationship. At this time, the modes in the multimode gain medium form a resonance pair, realizing the directional distribution of gain between modes. The output module is used to output the modulated laser signal; the Feshbach resonance tuning module makes the gain curves of different frequencies resonate with the mode gain curves of the multimode gain module, thereby realizing the control of the mode distribution of the laser output light field.

2. The mode-controlled laser based on a Feshbach-like resonance according to claim 1, characterized in that: The multimode gain module includes a pump source, a first collimator, a first reflector, a dichroic mirror, a second collimator, and a multimode gain medium. The pump light emitted from the pump source is collimated by the first collimator, and its direction is adjusted by the first reflector. Then, it is combined with the signal light in the resonant cavity by the dichroic mirror. The combined beam is then guided into the multimode gain medium by the second collimator. The interaction between the signal light and the pump light in the multimode gain medium generates a multimode optical field.

3. A mode-controlled laser based on a Feshbach-like resonance according to claim 1, characterized in that: The saturable absorption module includes a saturable absorber for shaping continuous light into a pulsed light signal through the saturable absorption effect.

4. A mode-controlled laser based on a Feshbach-like resonance according to claim 1, characterized in that: The polarization control section includes a quarter-wave plate and a half-wave plate, which are arranged sequentially in the optical path to coordinate the polarization state of the signal light.

5. A mode-controlled laser based on a Feshbach-like resonance according to claim 1, characterized in that: The frequency reflectivity curve tuning device is a position-adjustable reflector, which adjusts the reflectivity of different frequency components by changing the cavity length of the resonant cavity.

6. A mode-controlled laser based on a Feshbach-like resonance according to claim 1, characterized in that: The output module includes a second reflector and an optical beam splitter; the second reflector is used to adjust the propagation direction of the signal light, and the optical beam splitter outputs the signal light in the resonant cavity as the output laser according to a preset ratio.

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