A dual-wavelength resonator based on volume Bragg gratings

Abstract

The present invention relates to a dual-wavelength resonator based on volume Bragg gratings, and relates to the field of laser technology. The dual-wavelength resonator includes: first to fourth volume Bragg gratings; the first volume Bragg grating and the second volume Bragg grating are arranged at intervals; the reflection light optical path of the third volume Bragg grating coincides with the diffraction light optical path of the first volume Bragg grating; the reflection light optical path of the fourth volume Bragg grating coincides with the diffraction light optical path of the second volume Bragg grating; the first volume Bragg grating and the second volume Bragg grating are located on the outgoing light path of the pump light; the first volume Bragg grating and the second volume Bragg grating output dual-wavelength laser. In the present invention, the volume Bragg gratings are respectively used as a reflector and an output mirror, and the volume Bragg gratings are utilized to coordinate the gain competition between two laser oscillation wavelengths in the resonator, so as to achieve stable and balanced dual-wavelength laser output.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and particularly to a dual-wavelength resonator based on a volume Bragg grating. Background Art

[0002] Due to the advantages of simple and compact structure, high efficiency, and good output beam quality of dual-wavelength lasers, in recent years, the demand for dual-wavelength lasers in more and more fields such as laser communication, feature recognition, interference rainbow holography, and fine laser spectroscopy has been increasing, making dual-wavelength lasers have broad application prospects.

[0003] A dual-wavelength laser is a device that uses a solid as the working medium to generate laser light. It includes three main components: a resonator, a pump source, and a working medium. The resonator is a cavity that provides feedback for the light wave to oscillate back and forth, usually composed of two mirrors perpendicular to the axis of the working medium. The light will not escape from the cavity even if it travels back and forth many times in the stable resonator.

[0004] Currently, most dual-wavelength lasers are solid-state lasers. For example, a common Q-switched dual-wavelength laser uses a single laser gain medium to obtain simultaneous output of dual-wavelength laser light from the output mirror. However, when two-wavelength laser light is generated in the same gain medium, there is intense gain competition between the transition spectral lines of the two-wavelength laser light, which affects the stability of the laser output. Summary of the Invention

[0005] The purpose of the present invention is to provide a dual-wavelength resonator based on a volume Bragg grating, which uses the volume Bragg grating as the output mirror (spectral selection element) to coordinate the gain competition between the two laser oscillation wavelengths in the resonator and achieve stable and balanced dual-wavelength laser output.

[0006] To achieve the above purpose, the present invention provides the following solution:

[0007] A dual-wavelength resonator based on a volume Bragg grating, comprising: a first pair of volume Bragg gratings and a second pair of volume Bragg gratings; the first pair of volume Bragg gratings includes a first volume Bragg grating and a third volume Bragg grating, and the second pair of volume Bragg gratings includes a second volume Bragg grating and a fourth volume Bragg grating;

[0008] Both the first volume Bragg grating and the second volume Bragg grating are located on the outgoing light path of the pump light;

[0009] The first volume Bragg grating and the second volume Bragg grating are arranged at intervals, and the pump light is located between the plane where the first volume Bragg grating is located and the plane where the second volume Bragg grating is located;

[0010] The third volume Bragg grating is located on the diffraction optical path of the first volume Bragg grating; the included angle between the plane where the third volume Bragg grating is located and the plane where the first volume Bragg grating is located is a first preset angle, and the reflection optical path of the third volume Bragg grating coincides with the diffraction optical path of the first volume Bragg grating;

[0011] The fourth volume Bragg grating is located on the diffraction optical path of the second volume Bragg grating; the included angle between the plane where the fourth volume Bragg grating is located and the plane where the second volume Bragg grating is located is a second preset angle, and the reflection optical path of the fourth volume Bragg grating coincides with the diffraction optical path of the second volume Bragg grating;

[0012] The first volume Bragg grating is used to output light that meets the first preset transmission condition of the first volume Bragg grating, and diffract light that does not meet the first preset transmission condition;

[0013] The second volume Bragg grating is used to output light that meets the second preset transmission condition of the second volume Bragg grating, and diffract light that does not meet the second preset transmission condition;

[0014] The third volume Bragg grating is used to reflect light that meets the third preset reflection condition of the third volume Bragg grating;

[0015] The fourth volume Bragg grating is used to reflect light that meets the fourth preset reflection condition of the fourth volume Bragg grating.

[0016] Optionally, both the first volume Bragg grating and the second volume Bragg grating are transmissive volume Bragg gratings;

[0017] Both the third volume Bragg grating and the fourth volume Bragg grating are reflective volume Bragg gratings.

[0018] Optionally, the grating periods of the first volume Bragg grating and the second volume Bragg grating are the same.

[0019] Optionally, the grating periods of the third volume Bragg grating and the fourth volume Bragg grating are the same.

[0020] Optionally, the grating thicknesses of the first volume Bragg grating and the second volume Bragg grating are the same.

[0021] Optionally, the grating thicknesses of the third volume Bragg grating and the fourth volume Bragg grating are the same.

[0022] Optionally, the distance between the third volume Bragg grating and the first volume Bragg grating is equal to the distance between the fourth volume Bragg grating and the second volume Bragg grating.

[0023] Optionally, the dual-wavelength resonator further includes: a laser gain medium; the laser gain medium is used to amplify the light in the dual-wavelength resonator.

[0024] Optionally, the laser gain medium is a neodymium-doped yttrium aluminum garnet laser crystal or a ytterbium-doped yttrium aluminum garnet laser crystal.

[0025] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] The present invention provides a dual-wavelength resonator based on volume Bragg gratings. The dual-wavelength resonator includes: a first pair of volume Bragg gratings and a second pair of volume Bragg gratings; the first pair of volume Bragg gratings includes a first volume Bragg grating and a third volume Bragg grating, and the second pair of volume Bragg gratings includes a second volume Bragg grating and a fourth volume Bragg grating; both the first volume Bragg grating and the second volume Bragg grating are located on the outgoing light path of the pump light; the first volume Bragg grating and the second volume Bragg grating are arranged at intervals, and the pump light is located between the plane where the first volume Bragg grating is located and the plane where the second volume Bragg grating is located; the third volume Bragg grating is located on the diffraction light path of the first volume Bragg grating; the included angle between the plane where the third volume Bragg grating is located and the plane where the first volume Bragg grating is located is a first preset angle, and the reflected light path of the third volume Bragg grating coincides with the diffraction light path of the first volume Bragg grating; the fourth volume Bragg grating is located on the diffraction light path of the second volume Bragg grating; the included angle between the plane where the fourth volume Bragg grating is located and the plane where the second volume Bragg grating is located is a second preset angle, and the reflected light path of the fourth volume Bragg grating coincides with the diffraction light path of the second volume Bragg grating; the first volume Bragg grating is used to output light that meets the first preset transmission condition of the first volume Bragg grating, and diffract light that does not meet the first preset transmission condition; the second volume Bragg grating is used to output light that meets the second preset transmission condition of the second volume Bragg grating, and diffract light that does not meet the second preset transmission condition; the third volume Bragg grating is used to reflect light that meets the third preset reflection condition of the third volume Bragg grating; the fourth volume Bragg grating is used to reflect light that meets the fourth preset reflection condition of the fourth volume Bragg grating. The present invention uses volume Bragg gratings as reflectors and output mirrors respectively, and utilizes the volume Bragg gratings to coordinate the gain competition between two laser oscillation wavelengths in the resonator, so as to achieve stable and balanced dual-wavelength laser output. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 Structural diagram of the dual-wavelength resonator provided by the embodiment of the present invention;

[0029] Figure 2 Schematic structural diagram of the included angle between volume Bragg gratings provided by the embodiment of the present invention;

[0030] Figure 3 Simulated curve diagram of the angle selectivity of transmissive volume Bragg gratings with different grating thicknesses provided by the embodiment of the present invention;

[0031] Figure 4 Simulated curve diagram of the angle selectivity of transmissive volume Bragg gratings with different grating periods provided by the embodiment of the present invention;

[0032] Figure 5 Simulated curve diagram of the wavelength selectivity of reflective volume Bragg gratings with different grating thicknesses provided by the embodiment of the present invention;

[0033] Figure 6 Simulated curve diagram of the wavelength selectivity of reflective volume Bragg gratings with different grating periods provided by the embodiment of the present invention;

[0034] Figure 7 Schematic curve diagram of the output of dual wavelengths provided by the embodiment of the present invention.

[0035] Symbol description: TVBG1, the first volume Bragg grating; TVBG2, the second volume Bragg grating; RVBG3, the third volume Bragg grating; RVBG4, the fourth volume Bragg grating. Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] The purpose of the present invention is to provide a dual-wavelength resonator based on volume Bragg gratings, using volume Bragg gratings as output mirrors (spectral selection elements) to coordinate the gain competition between two laser oscillation wavelengths in the resonator, and realizing stable and balanced dual-wavelength laser output.

[0038] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0039] This embodiment provides a dual-wavelength resonator based on volume Bragg gratings,Figure 1 The structural diagram of the dual-wavelength resonant cavity provided by the embodiment of the present invention is shown in Figure 1 The dual-wavelength resonant cavity includes: a first pair of volume Bragg gratings and a second pair of volume Bragg gratings; the first pair of volume Bragg gratings includes a first volume Bragg grating TVBG1 and a third volume Bragg grating RVBG3, and the second pair of volume Bragg gratings includes a second volume Bragg grating TVBG2 and a fourth volume Bragg grating RVBG4.

[0040] The dual-wavelength resonant cavity is used to form a laser oscillation and output dual-wavelength laser.

[0041] Both the first volume Bragg grating and the second volume Bragg grating are located on the outgoing light path of the pump light.

[0042] The first volume Bragg grating TVBG1 and the second volume Bragg grating TVBG2 are arranged at intervals, and the pump light is located between the plane where the first volume Bragg grating is located and the plane where the second volume Bragg grating is located. The first volume Bragg grating and the second volume Bragg grating are arranged obliquely to facilitate the incidence of the pump light onto the first volume Bragg grating and the second volume Bragg grating.

[0043] The third volume Bragg grating is located on the diffraction light path of the first volume Bragg grating; the included angle between the plane where the third volume Bragg grating is located and the plane where the first volume Bragg grating is located is a first preset angle, and the reflected light path of the third volume Bragg grating coincides with the diffraction light path of the first volume Bragg grating. See Figure 2 The included angle between the third volume Bragg grating and the first volume Bragg grating, that is, the first preset angle θ 1 ranges from 10° to 30°.

[0044] The fourth volume Bragg grating is located on the diffraction light path of the second volume Bragg grating; the included angle between the plane where the fourth volume Bragg grating is located and the plane where the second volume Bragg grating is located is a second preset angle, and the reflected light path of the fourth volume Bragg grating coincides with the diffraction light path of the second volume Bragg grating. See Figure 2 The included angle between the fourth volume Bragg grating and the second volume Bragg grating, that is, the second preset angle θ 2 ranges from 10° to 30°.

[0045] The first volume Bragg grating is used to output the light that meets the first preset transmission condition of the first volume Bragg grating, and diffract the light that does not meet the first preset transmission condition.

[0046] The second volume Bragg grating is used to output the light that meets the second preset transmission condition of the second volume Bragg grating, and diffract the light that does not meet the second preset transmission condition.

[0047] The third volume Bragg grating is used to reflect light that meets the third preset reflection condition of the third volume Bragg grating. The third volume Bragg grating is also used to filter light that does not meet the third preset reflection condition.

[0048] The fourth volume Bragg grating is used to reflect light that meets the fourth preset reflection condition of the fourth volume Bragg grating. The fourth volume Bragg grating is also used to filter light that does not meet the fourth preset reflection condition.

[0049] The third volume Bragg grating and the fourth volume Bragg grating are placed obliquely, and it is ensured that the diffracted light output from the first volume Bragg grating and the second volume Bragg grating is incident perpendicularly on the third volume Bragg grating and the fourth volume Bragg grating.

[0050] Both the first volume Bragg grating TVBG1 and the second volume Bragg grating TVBG2 are transmissive volume Bragg gratings.

[0051] Both the third volume Bragg grating RVBG3 and the fourth volume Bragg grating RVBG4 are reflective volume Bragg gratings.

[0052] Each pair of volume Bragg gratings is aligned in the resonant cavity and can be used as the reflection mirror and output mirror of the dual-wavelength resonant cavity. That is, the first volume Bragg grating TVBG1 and the third volume Bragg grating RVBG3 are aligned in the resonant cavity and form the reflecting mirror 1 of the resonant cavity. At the same time, the reflecting mirror 1 can also be used as the output coupling mirror 1; the second volume Bragg grating TVBG2 and the fourth volume Bragg grating RVBG4 are aligned in the resonant cavity and form the reflecting mirror 2 of the resonant cavity. At the same time, the reflecting mirror 2 can also be used as the output coupling mirror 2. The reflecting mirror 1 (output coupling mirror 1) and the reflecting mirror 2 (output coupling mirror 2) are combined reflective volume Bragg gratings and transmissive volume Bragg gratings.

[0053] The propagation path of light is as follows: The pump light is injected from the side end of the resonant cavity and incident on the first volume Bragg grating and the second volume Bragg grating at the Bragg angle and diffracted by the first volume Bragg grating and the second volume Bragg grating respectively. The diffracted light of the first volume Bragg grating enters the third volume Bragg grating, and the diffracted light that meets the third preset reflection condition is diffracted (reflected) by the third volume Bragg grating. The diffracted light of the third volume Bragg grating returns along the optical path of the diffracted light of the first volume Bragg grating and enters the first volume Bragg grating; The diffracted light of the second volume Bragg grating enters the fourth volume Bragg grating, and the diffracted light that meets the fourth preset reflection condition is diffracted (reflected) by the fourth volume Bragg grating; The diffracted light of the fourth volume Bragg grating returns along the optical path of the diffracted light of the second volume Bragg grating and enters the second volume Bragg grating; The first volume Bragg grating and the second volume Bragg grating diffract the diffracted light returned by the third volume Bragg grating and the fourth volume Bragg grating again and then enter the third volume Bragg grating and the fourth volume Bragg grating respectively, causing the light to form oscillations. The transmitted light of the reflective Bragg grating is output after wavelength selection based on the grating. The pump light in this embodiment is radiation light. The diffracted light that does not meet the third preset reflection condition and the fourth preset reflection condition is filtered out of the dual-wavelength resonant cavity by the third volume Bragg grating and the fourth volume Bragg grating respectively. The first preset reflection condition, the second preset reflection condition, the third preset reflection condition and the fourth preset reflection condition are all determined by the wavelength selection parameters of the corresponding volume Bragg grating.

[0054] The grating periods of the first volume Bragg grating and the second volume Bragg grating are the same, or the grating thicknesses of the first volume Bragg grating and the second volume Bragg grating are the same.

[0055] The grating periods of the third volume Bragg grating and the fourth volume Bragg grating are the same, or the grating thicknesses of the third volume Bragg grating and the fourth volume Bragg grating are the same.

[0056] The first volume Bragg grating, the second volume Bragg grating, the third volume Bragg grating and the fourth volume Bragg grating are all uniform period gratings and all are phase-type volume Bragg gratings. That is, the first volume Bragg grating and the second volume Bragg grating are transmissive volume Bragg gratings of phase-type volume Bragg gratings, and the third volume Bragg grating and the fourth volume Bragg grating are reflective volume Bragg gratings of phase-type volume Bragg gratings, and the first volume Bragg grating, the second volume Bragg grating, the third volume Bragg grating and the fourth volume Bragg grating are periodically uniform.

[0057] The distance between the third volume Bragg grating RVBG3 and the first volume Bragg grating TVBG1 is equal to the distance between the fourth volume Bragg grating RVBG4 and the second volume Bragg grating TVBG2. The positions of the two pairs of volume Bragg gratings are as Figure 1 shown, L 1 +L 2 =L1 +L 3 , and the placement positions of the third volume Bragg grating and the fourth volume Bragg grating are such that the diffracted light of the first volume Bragg grating and the second volume Bragg grating can be incident on the third volume Bragg grating and the fourth volume Bragg grating respectively as the incident light of the third volume Bragg grating and the fourth volume Bragg grating. At the same time, the diffracted light of the third volume Bragg grating and the fourth volume Bragg grating can return along the original path of the diffracted light of the first volume Bragg grating and the second volume Bragg grating. Wherein, L 1 represents the distance between the first volume Bragg grating and the second volume Bragg grating, L 2 represents the distance between the first volume Bragg grating and the third volume Bragg grating, L 3 represents the distance between the second volume Bragg grating and the fourth volume Bragg grating.

[0058] The dual-wavelength resonator further includes: a laser gain medium; the laser gain medium is used to amplify the light in the dual-wavelength resonator. The first volume Bragg grating, the second volume Bragg grating, the third volume Bragg grating, and the fourth volume Bragg grating of this embodiment are all located in the same kind of laser gain medium.

[0059] The laser gain medium uses a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser crystal or a ytterbium-doped yttrium aluminum garnet (Yb:YAG) laser crystal or other laser crystals.

[0060] The volume Bragg grating is made of photo-thermo-refractive index glass, and the photo-thermo-refractive index glass is a silicate glass doped with cerium, silver, and fluorine.

[0061] The dual-wavelength resonator of this embodiment mainly performs intracavity oscillation on infrared light.

[0062] The first volume Bragg grating, the second volume Bragg grating, the third volume Bragg grating, and the fourth volume Bragg grating all have excellent angular selectivity, wavelength selectivity, and high diffraction efficiency. They are considered ideal wavelength and angle selection devices with high tunability. Parameters such as the incident angle, diffraction angle, central wavelength, and angular (spectral) selectivity of the volume Bragg grating can be adjusted by changing the grating structure parameters such as the grating thickness, refractive index modulation, grating period, and grating vector tilt angle of the volume Bragg grating. Among them, the incident angle satisfies the grating Bragg angle condition; the diffraction angle satisfies the Bragg condition: cos(φ - θ) = K / β, where φ is the grating vector tilt angle, the grating vector tilt angle φ is controlled within 0° to 90°, θ is the incident angle corresponding to the incident light, K is the grating vector, and β is the average propagation constant of light in the grating; the central wavelength is 400nm - 2000nm, and it can be tunably selected; the grating thickness is greater than 0.5mm; the range of the grating period is 0.1 micrometer to 6 micrometers; the refractive index modulation is greater than 10ppm. The grating vector tilt angle refers to the angle at which the grating stripe plane is perpendicular to the incident plane and is tilted at an angle φ with respect to the medium boundary.

[0063] The excellent optical properties of the first volume Bragg grating, the second volume Bragg grating, the third volume Bragg grating, and the fourth volume Bragg grating are mainly manifested in:

[0064] (1) The wavelength selectivity of the transmissive volume Bragg grating reaches 0.3nm - 20nm, and the wavelength selectivity of the reflective volume Bragg grating reaches 0.01nm - 10nm;

[0065] (2) The angular selectivity of the transmissive volume Bragg grating reaches 0.1mrad - 10mrad, and the angular selectivity of the reflective volume Bragg grating reaches 10mrad - 100mrad;

[0066] (3) The diffraction efficiency of the transmissive volume Bragg grating can reach 99% in the wavelength range of 633nm to 1550nm, and the diffraction efficiency of the reflective volume Bragg grating can reach 97% in the wavelength range of 633nm to 1550nm. Therefore, the diffraction efficiency of a single volume Bragg grating is high in the wavelength range of 633nm to 1550nm;

[0067] (4) High damage threshold. For a YAG (yttrium aluminum garnet) laser with a laser pulse width of 1ns, the damage threshold can reach 7J / cm 2 ~10J / cm 2 ; for a YAG laser with a laser pulse width of 8ns - 10ns, the damage threshold can reach 30J / cm 2 ~40J / cm 2 ;

[0068] (5) Low loss, the loss of the volume Bragg grating is less than 2.5%.

[0069] The volume Bragg grating has excellent angular selectivity and wavelength selectivity. By utilizing the angular selectivity of the transmissive volume Bragg grating and the wavelength selectivity of the reflective volume Bragg grating in combination, the beam bandwidth is narrowed. By adjusting the angular selectivity of the transmissive volume Bragg grating and the wavelength selectivity of the reflective volume Bragg grating, an optical filter with a wavelength bandwidth intersection part that can generate a light filter less than or equal to the longitudinal mode interval can be produced to select the desired longitudinal mode. It is precisely because the narrowband filter composed of the combined structure of the transmissive volume Bragg grating and the reflective volume Bragg grating can perform longitudinal mode selection that the combined structure of the transmissive volume Bragg grating and the reflective volume Bragg grating can be used as a dual-wavelength resonator.

[0070] According to the diffraction theory of the volume Bragg grating, the diffraction characteristics of the volume Bragg grating are closely related to the grating period, grating thickness, and refractive index modulation degree. The operating wavelength of the dual-wavelength laser corresponds to the grating period and satisfies the Bragg condition. The grating thickness and refractive index modulation degree are mutually matched to enable the volume Bragg grating to have specific diffraction efficiency and spectral selectivity. Generally, for the transmissive volume Bragg grating, its diffraction efficiency increases with the product of the grating thickness and refractive index modulation degree and shows periodic changes in the range of 0% to 100%, and its spectral selectivity decreases with the increase of the grating thickness and refractive index modulation degree; for the reflective volume Bragg grating, its diffraction efficiency continuously increases with the increase of the product of the grating thickness and refractive index modulation degree and finally approaches 100%, and its spectral selectivity decreases with the increase of the grating thickness and refractive index modulation degree.

[0071] Figure 3 It is the simulated angular selectivity curve graph of the first volume Bragg grating or the second volume Bragg grating when the incident wavelength is 1064 nm and the grating thickness d is 2.5 mm and 3.5 mm respectively. Figure 3 The parameters of the first volume Bragg grating or the second volume Bragg grating in it are: the Bragg wavelength is 1064 nm, the grating period is 3 μm, and the grating vector tilt angle is 90°. When the wavelength is fixed, the incident beam of the volume Bragg grating does not satisfy the Bragg condition, that is, it deviates from the Bragg angle. At this time, the volume Bragg grating has angular selectivity.

[0072] Figure 4 It is the simulated angular selectivity curve graph of the first volume Bragg grating or the second volume Bragg grating when the incident wavelength is 1064 nm and the grating period Λ is 2 μm and 3 μm respectively. Figure 4 The parameters of the first volume Bragg grating or the second volume Bragg grating in it are: the Bragg wavelength is 1064 nm, the grating thickness is 2.5 mm, and the grating vector tilt angle is 90°.

[0073] Figure 5Simulated wavelength selectivity curves of the third and fourth volume Bragg gratings when the incident wavelength is 1064 nm and the grating thickness d is 4 mm and 5 mm respectively. Figure 5 The parameters of the third or fourth volume Bragg grating in Figure 5 are: the Bragg wavelength is 1064 nm, the grating period is 0.6 μm, and the grating vector tilt angle is 90°.

[0074] Figure 6 Simulated wavelength selectivity curves of the third and fourth volume Bragg gratings when the incident wavelength is 1064 nm and the grating period Λ is 0.5 μm and 0.6 μm respectively. Figure 6 The parameters of the third or fourth volume Bragg grating in Figure 6 are: the Bragg wavelength is 1064 nm, the grating thickness is 5 mm, and the grating vector tilt angle is 90°.

[0075] Figure 7 Schematic diagram of the curves of the two wavelengths output by the dual-wavelength resonator of the present invention when the incident wavelength is 1064 nm. The full width at half maximum (FWHM) is used to represent the width of the output wavelength. The FWHM of the two-wavelength output is 0.5 nm for both. Curve 1 represents the output wavelength with a central wavelength of 1063.2 nm, and curve 2 represents the output wavelength with a central wavelength of 1064.8 nm.

[0076] The present invention adopts a resonator structure with two pairs of volume Bragg gratings, which outputs laser in two directions simultaneously. The structure is simple and easy to implement. By adjusting the grating structure parameters of the volume Bragg gratings, a dual-wavelength dual-end output with a wavelength difference of several nanometers or even lower between the wavelength output by the first volume Bragg grating and the wavelength output by the second volume Bragg grating can be achieved. At the same time, by filtering out the medium and high-frequency components in the beam through the volume Bragg grating and optimizing the wavefront, the quality of the output beam can be optimized, expanding the design field of the optical resonator of the dual-wavelength laser. Through the combined structure of the transmissive volume Bragg grating and the reflective volume Bragg grating, and controlling the structure parameters (thickness and period) of each volume Bragg grating, the angular selectivity of the transmissive volume Bragg grating and the wavelength selectivity of the reflective volume Bragg grating are coordinated to narrow the beam bandwidth. The structure of the longitudinal mode laser is simplified, the anti-interference ability is improved, and there is the potential for high-power output. The angular selectivity of the transmissive volume Bragg grating can limit the beam divergence angle in the cavity, which is conducive to achieving a large transverse mode diameter and high energy output. In addition, the present invention uses photo-thermo-refractive index glass as the material for preparing the grating, which can carry a high laser power; and does not change the polarization state of the radiation light, has good stability and strong anti-interference ability, so that the volume Bragg grating is less affected by temperature, has low loss and high damage threshold.

[0077] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0078] In this article, specific examples are used to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A dual-wavelength resonator based on volume Bragg gratings, characterized in that, it includes: A first pair of volume Bragg gratings and a second pair of volume Bragg gratings; the first pair of volume Bragg gratings includes a first volume Bragg grating and a third volume Bragg grating, and the second pair of volume Bragg gratings includes a second volume Bragg grating and a fourth volume Bragg grating; Both the first volume Bragg grating and the second volume Bragg grating are located on the outgoing light path of the pump light; The first volume Bragg grating and the second volume Bragg grating are arranged at intervals, and the pump light is located between the plane where the first volume Bragg grating is located and the plane where the second volume Bragg grating is located. The first volume Bragg grating and the second volume Bragg grating are inclined to facilitate the incidence of the pump light onto the first volume Bragg grating and the second volume Bragg grating; The third volume Bragg grating is located on the diffraction light path of the first volume Bragg grating; the included angle between the plane where the third volume Bragg grating is located and the plane where the first volume Bragg grating is located is a first preset angle, and the reflected light path of the third volume Bragg grating coincides with the diffraction light path of the first volume Bragg grating; The fourth volume Bragg grating is located on the diffraction light path of the second volume Bragg grating; the included angle between the plane where the fourth volume Bragg grating is located and the plane where the second volume Bragg grating is located is a second preset angle, and the reflected light path of the fourth volume Bragg grating coincides with the diffraction light path of the second volume Bragg grating; The first volume Bragg grating is used to output light that meets the first preset transmission condition of the first volume Bragg grating, and diffract light that does not meet the first preset transmission condition; The second volume Bragg grating is used to output light that meets the second preset transmission condition of the second volume Bragg grating, and diffract light that does not meet the second preset transmission condition; The third volume Bragg grating is used to reflect light that meets the third preset reflection condition of the third volume Bragg grating; The fourth volume Bragg grating is used to reflect light that meets the fourth preset reflection condition of the fourth volume Bragg grating; The third volume Bragg grating and the fourth volume Bragg grating are placed obliquely, and it is ensured that the diffracted light output from the first volume Bragg grating and the second volume Bragg grating is incident perpendicularly on the third volume Bragg grating and the fourth volume Bragg grating; Each pair of volume Bragg gratings is aligned in the resonator and serves as the reflecting cavity mirrors of the dual-wavelength resonator, that is, the first volume Bragg grating and the third volume Bragg grating are aligned in the resonator and form the reflecting mirror (1) of the resonator, and the second volume Bragg grating and the fourth volume Bragg grating are aligned in the resonator and form the reflecting mirror (2) of the resonator. The reflecting mirror (1) and the reflecting mirror (2) are a combined reflecting type volume Bragg grating and a transmitting type volume Bragg grating.

2. The dual-wavelength resonator based on volume Bragg gratings according to claim 1, characterized in that, Both the first volume Bragg grating and the second volume Bragg grating are transmitting type volume Bragg gratings; Both the third volume Bragg grating and the fourth volume Bragg grating are reflecting type volume Bragg gratings.

3. The dual-wavelength resonator based on volume Bragg gratings according to claim 1, characterized in that, the grating periods of the first volume Bragg grating and the second volume Bragg grating are the same.

4. The dual-wavelength resonator based on volume Bragg gratings according to claim 1, characterized in that, the grating periods of the third volume Bragg grating and the fourth volume Bragg grating are the same.

5. The dual-wavelength resonator based on volume Bragg gratings according to claim 1, characterized in that, the grating thicknesses of the first volume Bragg grating and the second volume Bragg grating are the same.

6. The dual-wavelength resonator based on volume Bragg gratings according to claim 1, characterized in that, the grating thicknesses of the third volume Bragg grating and the fourth volume Bragg grating are the same.

7. The dual-wavelength resonator based on volume Bragg gratings according to claim 1, characterized in that, the distance between the third volume Bragg grating and the first volume Bragg grating is equal to the distance between the fourth volume Bragg grating and the second volume Bragg grating.

8. The dual-wavelength resonator based on volume Bragg gratings according to claim 1, characterized in that, the dual-wavelength resonator further comprises: a laser gain medium; the laser gain medium is used for amplifying the light in the dual-wavelength resonator.

9. The dual-wavelength resonator based on volume Bragg gratings according to claim 8, characterized in that, the laser gain medium is a neodymium-doped yttrium aluminum garnet laser crystal or a ytterbium-doped yttrium aluminum garnet laser crystal.

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