Double-shaft single-cavity double-frequency laser device and method

Abstract

The invention discloses a double-shaft single-cavity double-frequency laser generating device in the field of laser generating devices, and the device comprises a pump laser which is used for emitting a laser beam; the reflection separation device is arranged at the light output end of the pump laser; the prismatic dichroscope is arranged at the light output end of the reflection separation device, and the prismatic dichroscope is used for generating two axes in the same resonant cavity so as to generate two spatially separated laser oscillation modes; the etalon comprises a first etalon and a second etalon; an output coupling mirror; the invention further discloses a double-shaft single-cavity double-frequency laser generating method. Compared with the prior art, the invention has the beneficial effects that the two etalon independently select modes, the frequency adjustment is flexible, the operation is simple, the loss in the cavity is small, and the single-cavity common-mode noise is low.

Description

Technical Field

[0001] This invention relates to the field of laser generating devices, and more particularly to a biaxial single-cavity dual-frequency laser generating device and method. Background Technology

[0002] A dual-frequency laser is a laser system in which two intrinsic modes coexist within a single resonant cavity. Compared to a dual-frequency laser system formed by two independent lasers, a dual-frequency laser can passively eliminate laser frequency fluctuations caused by the external environment by utilizing the principle of a shared cavity, thereby obtaining a more stable difference frequency. Furthermore, the shared cavity structure of the two lasers in a dual-frequency laser makes its structure more compact. Based on these advantages, dual-frequency lasers have broad application potential and significant application value, and have long attracted considerable attention. For example, using a dual-frequency laser as a pump source to generate terahertz waves through the difference frequency has broad prospects in terahertz communication, detection, imaging systems, and sensing applications; dual-frequency laser interferometers using dual-frequency lasers as the light source are indispensable instruments for high-precision measurement of parameters such as length, position, and deformation in advanced manufacturing and scientific research; using optical radio frequency generated by dual frequencies, the velocity of moving objects can be precisely measured; and dual-frequency lasers can be used to detect precise spectra based on atomic coherent population trapping, locking the difference frequency of the dual-frequency laser, thereby realizing high-performance microwave atomic clocks. In summary, dual-frequency lasers can be widely used in lidar, atmospheric differential absorption lidar, terahertz wave generation, optical atomic clocks, precision laser spectroscopy and sensing, and are a key technology in many important precision instruments.

[0003] Based on their generation principles, dual-frequency lasers can be divided into two types: one is a dual-frequency laser based on a single-axis resonator, which typically utilizes intracavity birefringence or spectral filtering effects to achieve oscillation of two intrinsic modes; the other is a dual-frequency laser based on a dual-axis resonator, where each axis supports two oscillation modes at different frequencies. The former has a higher degree of cavity co-occurrence, but generally shares a gain medium, leading to a certain degree of gain competition between the two modes, causing some anti-phase noise and affecting laser stability. The latter cannot strictly co-occur, but it allows for some spatial separation of the gain regions of the two modes, thereby reducing or avoiding instability caused by gain competition.

[0004] Currently, dual-axis single-cavity dual-frequency lasers typically involve inserting a birefringent crystal within the cavity. The incident plane of this birefringent crystal is at a 45-degree angle to the optical axis, thus creating two oscillation modes: ordinary and extraordinary. While this method can easily achieve dual-frequency laser oscillation, it still suffers from several problems: First, the birefringent crystal has a certain degree of insertion loss, affecting power input. Second, the optical path lengths of the ordinary and extraordinary beams within the birefringent crystal change with temperature, affecting long-term frequency stability. Third, when the birefringent crystal is thin, only one etalon can be shared, affecting frequency tuning performance and making it difficult to simultaneously achieve minimum loss for both frequencies within the etalon, thus impacting power output and stability. Although using a thicker birefringent crystal can provide sufficient space for separation of the ordinary and extraordinary beams, allowing the use of two etalons, frequency stability becomes more sensitive to temperature fluctuations. Alternatively, using an in-cavity polarizing beam splitter prism and two output coupling mirrors is another way to implement a dual-frequency laser. Frequency tuning is relatively convenient, but because it is not a single cavity, it cannot fully utilize the common-cavity characteristics to eliminate common-mode noise.

[0005] In summary, the applicant has proposed a dual-axis single-cavity dual-frequency laser device and method. Summary of the Invention

[0006] To address the aforementioned shortcomings of the prior art, the present invention provides a dual-axis single-cavity dual-frequency laser device and method.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0008] A dual-axis, single-cavity, dual-frequency laser generator includes a pump laser for emitting a laser beam; a reflection separator located at the output end of the pump laser for spatially separating the emitted laser beam into two beams of equal power; a prismatic dichroic mirror located at the output end of the reflection separator for generating two axes within the same resonant cavity to produce two spatially separated laser oscillation modes; an etalon including a first etalon and a second etalon, both located at the output end of the prismatic dichroic mirror, for selecting the intracavity modes of the two beams; and an output coupling mirror located at the output end of the etalon, serving as the output face of the laser resonant cavity and closing the resonant cavity.

[0009] The dual-axis single-cavity system generates a biaxial laser by using a prism dichroic mirror and an output coupling mirror to cancel the common-mode noise of the dual-frequency laser. The structure is simple and does not require intracavity components to generate two spatially separated oscillation modes, resulting in low intracavity beam loss. The pump laser is spatially separated by a reflection separation device and matched with the two spatially separated laser oscillation modes in the dual-axis single cavity. At the same time, the first and second etalons are used for independent mode selection, which allows for flexible frequency adjustment. The structure is simple and easy to adjust.

[0010] Further defining the reflection separation device, it includes a first lens, a second lens, and a reflection system located between the first lens and the second lens. The reflection system includes a first mirror, a second mirror, a third mirror, and a fourth mirror. The reflecting surface of the first mirror is arranged downwards, and the first mirror blocks half of the beam emitted by the pump laser and reflects it. The reflecting surface of the first mirror is arranged at a 135° angle to the horizontal beam transmitted from the first lens. The second mirror is arranged parallel to the first mirror and directly below it, with its reflecting surface facing upwards. The third mirror is symmetrically arranged with respect to the second mirror about the vertical direction. The fourth mirror is arranged parallel to the third mirror and directly above it, with its reflecting surface facing downwards.

[0011] Traditional dual-axis single-cavity dual-frequency lasers have a certain insertion loss because they use a birefringent crystal with a cut surface at a 45-degree angle to the optical axis to form a dual axis in the same resonant cavity. By using a reflection separation device made of two lenses and four mirrors, the laser beam emitted by the pump laser is separated into two parallel laser beams, which makes it easier to independently adjust the pump beam and match it with the stimulated emission laser mode in the dual-axis single cavity.

[0012] Further defining the light-receiving side of the prismatic dichroic mirror as a ridge surface and the light-output side as a vertical plane, the prismatic dichroic mirror receives two parallel beams through its ridge surface and outputs them through its vertical plane, forming a dual-axis single cavity with the output coupling mirror.

[0013] Furthermore, the planar side of the prism dichroic mirror is also provided with a gain crystal, which is arranged parallel to the vertical plane of the prism dichroic mirror; the gain crystal serves as the working substance and generates a stimulated emission beam after being excited by the pump beam.

[0014] Further defining the output coupling mirror, the light receiving side is a concave spherical surface, and the light output side is a vertical plane; the concave spherical surface of the output coupling mirror can form a good biaxial single cavity with the prismatic dichroic mirror, resulting in better performance.

[0015] A method for generating dual-axis, single-cavity, dual-frequency lasers, comprising the following steps:

[0016] S1: The pump laser emits a horizontal pump laser beam;

[0017] S2: A pump laser beam emitted from the pump laser passes through the first lens. Half of the pump laser beam is reflected by the first mirror into a vertical beam to the second mirror. The second mirror reflects the vertical beam into a horizontal beam to the third mirror. The third mirror reflects the horizontal beam into a vertical beam to the fourth mirror. The fourth mirror reflects the vertical beam into a horizontal beam and outputs it to the second lens. The beam that is not reflected by the four mirrors is the first pump beam. The beam that is reflected by the four mirrors is the second pump beam.

[0018] S3: The first and second pump beams, which are output horizontally and parallel, pass through the upper and lower inclined surfaces of the ridge side of the prismatic dichroic mirror in the vertical direction, and then generate intersecting X-shaped first and second stimulated emission beams through the gain crystal.

[0019] S4: The first stimulated emission beam of the X-shaped cross beam is output to the output coupling mirror after passing through the second etalon mode selection, and the second stimulated emission beam is output to the output coupling mirror after passing through the first etalon mode selection.

[0020] The advantages of this invention compared to the prior art are: the two standard etalons have independent mode selection frequency adjustment, which is flexible, simple to operate, low cavity loss, and low single-cavity common-mode noise. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0022] Figure 2 This is a three-dimensional schematic diagram of a prismatic dichroic mirror.

[0023] The symbols for the main components in the diagram are explained below:

[0024] Pump laser 1, first lens 2, first reflector 3, second reflector 4, third reflector 5, fourth reflector 6, second lens 7, prism dichroic mirror 8, gain crystal 9, first etalon 10, second etalon 11, output coupling mirror 12, first pump beam B1, first stimulated emission beam B11, second pump beam B2, second stimulated emission beam B22. Detailed Implementation

[0025] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0026] Example:

[0027] like Figure 1 and Figure 2 As shown, a dual-axis single-cavity dual-frequency laser generator includes a pump laser 1, a reflection separation device, a prism dichroic mirror 8, a gain crystal 9, an etalon, and an output coupling mirror 12. The pump laser 1 emits a laser beam. The reflection separation device is located at the output end of the pump laser 1 and is used to spatially separate the laser beam emitted by the pump laser 1 into two beams of equal power. The reflection separation device includes a first lens 2, a second lens 7, and a reflection system located between the first lens 2 and the second lens 7. The reflection system includes a first mirror 3, a second mirror 4, a third mirror 5, and a fourth mirror 6. The reflecting surface of the first mirror 3 is set downwards, blocking half of the beam emitted by the pump laser 1 and reflecting it. The reflecting surface of the first mirror 3 is set at a 135° angle to the horizontal beam transmitted from the first lens 2. The second mirror 4 is set parallel to the first mirror 3 and directly below it, with its reflecting surface facing upwards. The third mirror 5 is positioned relative to the second mirror 4 in the vertical direction. The fourth reflector 6 is symmetrically positioned, parallel to the third reflector 5, directly above the third reflector 5, with the reflecting surface of the fourth reflector 6 facing downwards. A prismatic dichroic mirror 8 is located at the light output end of the reflection separation device. The prismatic dichroic mirror 8 is used to generate two axes within the same resonant cavity to produce two spatially separated laser oscillation modes. The light receiving side of the prismatic dichroic mirror 8 is a ridge-shaped surface, and the light output side is a vertical plane. A gain crystal 9 is located on the planar side of the prismatic dichroic mirror 8, and the gain crystal 9 is parallel to the vertical plane of the prismatic dichroic mirror 8. The etalon includes a first etalon 10 and a second etalon 11, both located at the optical output end of the gain chip 9. The first etalon 10 and the second etalon 11 respectively select the intracavity modes of the two beams. The output coupling mirror 12 is located at the optical output end of the etalon and serves as the output end face of the laser resonator and closes the resonator. The optical receiving side of the output coupling mirror 12 is a concave spherical surface, and the optical output side is a vertical plane. The pump laser 1 is a fiber-coupled semiconductor laser.

[0028] The dual-axis single-cavity laser, generated between a prism dichroic mirror 8 and an output coupling mirror 12, cancels common-mode noise in the dual-frequency laser. This design is simple, eliminates the need for intracavity components to generate two spatially separated oscillation modes, and minimizes intracavity beam loss. A reflection separation device is used to spatially separate the pump laser and match it to the two spatially separated laser oscillation modes within the dual-axis single-cavity laser. Simultaneously, independent mode selection is achieved using the first etalon 10 and the second etalon 11, allowing for flexible frequency adjustment. The design is simple and easy to adjust. Traditional dual-axis single-cavity dual-frequency lasers, which use a birefringent crystal with a 45-degree angle between its cut surface and the optical axis to form a dual axis within the same resonant cavity, exhibit certain insertion losses. A reflection separation device, consisting of two lenses and four mirrors, separates the laser beam emitted by the pump laser 1 into two parallel laser beams. This allows for independent adjustment of the pump beams and matching with the stimulated emission laser mode within the dual-axis single cavity. The two parallel beams are received by the ridge surface of the prismatic dichroic mirror 8 and output in a vertical plane. The prismatic dichroic mirror 8 and the output coupling mirror 12 form a dual-axis single cavity. The gain crystal 9 serves as the working medium and generates a stimulated emission beam after being excited by the pump beam. The concave spherical surface of the output coupling mirror 12 can effectively form a dual-axis single cavity with the prismatic dichroic mirror 8, resulting in better performance.

[0029] A method for generating dual-axis, single-cavity, dual-frequency lasers, comprising the following steps:

[0030] S1: Pump laser 1 emits a horizontal pump laser beam;

[0031] S2: A pump laser beam emitted from pump laser 1 passes through the first lens 2. Half of the pump laser beam is reflected by the first mirror 3 into a vertical beam to the second mirror 4. The second mirror 4 reflects the vertical beam into a horizontal beam to the third mirror 5. The third mirror 5 reflects the horizontal beam into a vertical beam to the fourth mirror 6. The fourth mirror 6 reflects the vertical beam into a horizontal beam and outputs it to the second lens 7. The beam that is not reflected by the four mirrors is the first pump beam B1, and the beam after being reflected by the four mirrors is the second pump beam B2.

[0032] S3: The first pump beam B1 and the second pump beam B2, which are output horizontally and parallel, pass through the upper and lower inclined surfaces of the ridge side of the prism dichroic mirror 8 in the vertical direction, and then generate the intersecting X-shaped first stimulated emission beam B11 and second stimulated emission beam B21 through the gain crystal 9.

[0033] S4: The first stimulated emission beam B11, which crosses in an X shape, is output to the output coupling mirror 12 after mode selection by the second etalon 11, and the second stimulated emission beam B21 is output to the output coupling mirror 12 after mode selection by the first etalon 10.

[0034] It should be noted that the tilt angle of the ridge surface of the prism dichroic mirror in this article is derived based on actual needs and experimental data, and therefore will not be explained in detail.

Claims

1. A dual-axis single-cavity dual-frequency laser generator, characterized in that, include: A pump laser (1) is used to emit a laser beam; A reflection separation device is provided at the light output end of the pump laser (1). The reflection separation device is used to spatially separate a laser beam emitted by the pump laser (1) into two beams with equivalent power. A prismatic dichroic mirror (8) is provided at the light output end of the reflection separation device. The prismatic dichroic mirror (8) is used to generate two axes in the same resonant cavity to generate two spatially separated laser oscillation modes. The etalon includes a first etalon (10) and a second etalon (11), both of which are located at the light output end of the prism dichroic mirror (8). The first etalon (10) and the second etalon (11) respectively select the intracavity mode of the two beams. An output coupling mirror (12) is located at the optical output end of the etalon. The output coupling mirror (12) serves as the output end face of the laser resonant cavity and closes the resonant cavity.

2. The dual-axis single-cavity dual-frequency laser generator according to claim 1, characterized in that, The reflection separation device includes a first lens (2), a second lens (7), and a reflection system located between the first lens (2) and the second lens (7). The reflection system includes a first reflector (3), a second reflector (4), a third reflector (5), and a fourth reflector (6). The first reflector (3) is positioned with its reflective surface facing downwards. The first reflector (3) blocks half of the beam emitted by the pump laser (1) and reflects it. The reflective surface of the first reflector (3) is set at a 135° angle with the horizontal beam transmitted by the first lens (2). The second reflector (4) is positioned parallel to the first reflector (3) directly below it. The reflective surface of the second reflector (4) is positioned upwards. The third reflector (5) is symmetrically positioned with respect to the second reflector (4) about the vertical direction. The fourth reflector (6) is positioned parallel to the third reflector (5) directly above it. The reflective surface of the fourth reflector (6) is positioned downwards.

3. The dual-axis single-cavity dual-frequency laser generator according to claim 1, characterized in that, The light-receiving side of the prismatic dichroic mirror (8) is a ridge-shaped surface, and the light-output side is a vertical plane.

4. The dual-axis single-cavity dual-frequency laser generator according to claim 3, characterized in that, The planar side of the prismatic dichroic mirror (8) is also provided with a gain crystal (9), which is arranged parallel to the vertical plane of the prismatic dichroic mirror (8).

5. The dual-axis single-cavity dual-frequency laser generator according to claim 1, characterized in that, The light receiving side of the output coupling mirror (12) is a concave spherical surface, and the light output side is a vertical plane.

6. A method for generating a dual-axis, single-cavity, dual-frequency laser, characterized in that, The steps of using the dual-axis single-cavity dual-frequency laser generator according to any one of claims 1-5 are as follows: S1: The pump laser (1) emits a horizontal pump laser beam; S2: A pump laser beam emitted from the pump laser (1) passes through the first lens (2), and half of the pump laser beam is reflected by the first mirror (3) into a vertical beam to the second mirror (4). The second mirror (4) reflects the vertical beam into a horizontal beam to the third mirror (5). The third mirror (5) reflects the horizontal beam into a vertical beam to the fourth mirror (6). The fourth mirror (6) reflects the vertical beam into a horizontal beam and outputs it to the second lens (7). The beam that is not reflected by the four mirrors is the first pump beam (B1), and the beam after being reflected by the four mirrors is the second pump beam (B2). S3: The first pump beam (B1) and the second pump beam (B2) output horizontally and parallelly pass through the upper and lower inclined surfaces of the ridge side of the prism dichroic mirror (8) in the vertical direction, and then generate the intersecting X-shaped first stimulated emission beam (B11) and second stimulated emission beam (B21) through the gain crystal (9). S4: The first stimulated emission beam (B11) of the X-shaped cross is output to the output coupling mirror (12) after mode selection by the second etalon (11), and the second stimulated emission beam (B21) is output to the output coupling mirror (12) after mode selection by the first etalon (10).

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