A narrow linewidth solid-state laser

Abstract

A narrow linewidth solid laser, a laser resonant cavity input mirror, a lens and a laser resonant cavity output mirror are arranged in sequence along the output direction of the pump source; the laser resonant cavity input mirror is coated with a dielectric film with high transmittance to pump light and high reflectivity to laser, and the laser resonant cavity input mirror and the laser resonant cavity output mirror form a resonant cavity; the lens is coated with a laser band anti-reflection film; the light-transmitting surface of the laser gain medium is coated with an anti-reflection film for the pump band and the laser band, which is arranged between the laser resonant cavity input mirror and the lens; the quartz coupling prism and the whispering gallery cavity are adjacent to each other at a coupling interface, and are arranged between the lens and the laser resonant cavity output mirror; the side of the quartz coupling prism close to the lens is the incident surface, and the side close to the laser resonant cavity output mirror is the exit surface, and both the incident surface and the exit surface are coated with an anti-reflection film of the laser band, and the bottom surface produces total reflection. The laser has a simple structure, small size, easy integration, narrow linewidth, low noise, high reliability and good stability.

Description

Technical Field

[0001] The invention belongs to the technical field of solid lasers, and in particular relates to a narrow-linewidth solid laser. Background Art

[0002] All-solid-state narrow linewidth lasers have the characteristics of narrow frequency linewidth, low noise, good coherence, good stability, and excellent beam quality. They have broad application prospects in precision measurement, lidar, coherent optical communication, high-precision spectroscopy, optical frequency standards, gravitational wave detection, and other fields, and have become a research hotspot in the laser field in recent years. Under free operation, due to the inherent characteristics of the generally wide fluorescence emission spectrum of solid lasers, solid lasers will experience multi-longitudinal mode oscillations. This is because in the laser resonant cavity, different longitudinal modes of the wide fluorescence emission spectrum use different parts of the inverted particle population to oscillate at the same time, thereby forming multi-mode oscillations in the laser resonant cavity, and the number of oscillating longitudinal modes will increase with the increase of pump power. Therefore, solid lasers must adopt linewidth control technology to obtain narrow linewidth laser output.

[0003] At present, the commonly used laser linewidth control technology is to add mode selection components in the laser resonant cavity to narrow the laser spectrum and achieve narrow linewidth single longitudinal mode output. Typical schemes include standard tool frequency selection method, short cavity method, volume Bragg grating method, birefringent filter frequency selection method, composite resonant cavity method, etc. Using these schemes, domestic and foreign research institutions have made a series of progress in the narrow linewidth output of solid-state lasers, and achieved narrow linewidth laser output in different types of solid-state lasers. However, the commonly used standard tool Fabry-Perot cavity cavity size is usually large and not easy to integrate, and the high reflectivity cavity mirror is expensive and requires complex stabilization devices, which seriously limit the application of Fabry-Perot cavity. In addition, to obtain extremely narrow linewidth, low noise, high beam quality, and high stability laser output, it is usually necessary to superimpose several frequency selection methods, such as using multiple fast standards, short cavity and composite cavity combination, memory composite cavity and birefringent filter combination in the resonant cavity, so as to achieve the purpose of strengthening the mode selection of the resonant cavity. This inevitably brings about the increase of laser complexity, the introduction of loss, and the reduction of laser efficiency and stability. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a narrow linewidth solid laser, which has the characteristics of simple structure, small size, easy integration, narrow linewidth, low noise, high reliability and good stability. At the same time, it has low manufacturing cost and is easy to promote and apply on a large area.

[0005] In order to achieve the above object, the present invention provides a narrow linewidth solid laser, comprising a pump source, a laser resonant cavity input mirror, a lens, a laser resonant cavity output mirror, a laser gain medium, a quartz coupling prism and a whispering gallery cavity;

[0006] The laser resonant cavity input mirror, lens and laser resonant cavity output mirror are arranged in sequence along the output direction of the pump source; the laser resonant cavity input mirror is coated with a dielectric film with high transmittance to the pump light and high reflectivity to the laser, and the laser resonant cavity input mirror and the laser resonant cavity output mirror form a laser resonant cavity; the lens is coated with a laser band anti-reflection film;

[0007] The light-transmitting surface of the laser gain medium is coated with an anti-reflection film for the pump band and the laser band, which is arranged on the optical path between the laser resonant cavity input mirror and the lens;

[0008] The quartz coupling prism and the whispering gallery cavity are adjacent to each other at a coupling interface and are arranged on an optical path between a lens and an output mirror of a laser resonant cavity; the quartz coupling prism is an isosceles prism, a side surface close to the lens is an incident surface and is coated with an anti-reflection film of a laser band, a side surface close to the output mirror of the laser resonant cavity is an exit surface and is coated with an anti-reflection film of a laser band, a bottom surface generates total reflection, and couples the laser into the whispering gallery cavity through an evanescent field to realize frequency selection, and the excitation after frequency selection is continuously reflected in the whispering gallery cavity to form a resonant enhanced laser, which is coupled again through the quartz coupling prism and then emitted to the output mirror of the laser resonant cavity.

[0009] As a preference, the pump source is a semiconductor laser pump source.

[0010] Preferably, the laser gain medium is rare earth ion-doped crystal, ceramic or glass.

[0011] Preferably, the material of the whispering gallery cavity is CaF2.

[0012] Preferably, the material of the whispering gallery cavity is MgF2.

[0013] As a preference, the distance between the quartz coupling prism and the whispering gallery cavity is 50-100 nm.

[0014] In the present invention, the whispering gallery is used for frequency selection in the laser resonant cavity, which fully utilizes the advantages of the whispering gallery, such as smaller size, easy integration, and convenient preparation, and can achieve up to 10 9 The extremely high Q value is equivalent to an ultra-narrowband optical filter, which plays a significant role in frequency selection in the laser resonant cavity. This technical solution can not only significantly narrow the line width, but also suppress the noise of the laser resonant cavity, and finally achieve the continuous output of narrow line width laser with narrow line width, low noise and high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention.

[0016] In the figure: 1. Semiconductor laser pump source, 2. Laser resonator input mirror, 3. Laser gain medium, 4. Lens, 5. Quartz coupling prism, 6. Whispering gallery cavity, 7. Laser resonator output mirror. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings.

[0018] like Figure 1 As shown, the present invention provides a narrow linewidth solid laser, comprising a pump source 1, a laser resonant cavity input mirror 2, a lens 4, a laser resonant cavity output mirror 7, a laser gain medium 3, a quartz coupling prism 5 and a whispering gallery cavity 6;

[0019] The laser resonant cavity input mirror 2, lens 4 and laser resonant cavity output mirror 7 are arranged in sequence along the output direction of the pump source 1; the laser resonant cavity input mirror 2 is coated with a dielectric film with high transmittance to the pump light and high reflectivity to the laser, and the laser resonant cavity input mirror 2 and the laser resonant cavity output mirror 7 form a laser resonant cavity; the lens 4 is coated with a laser band anti-reflection film;

[0020] The laser gain medium 3 is plated with an anti-reflection film for the pump band and the laser band on the light-passing surface, and is arranged on the optical path between the laser resonant cavity input mirror 2 and the lens 4;

[0021] The quartz coupling prism 5 and the whispering gallery cavity 6 are adjacent to each other at a coupling interface and are arranged on the optical path between the lens 4 and the laser resonant cavity output mirror 7; the quartz coupling prism 5 is an isosceles prism, and its side close to the lens 4 is the incident surface and is coated with an anti-reflection film of the laser band, and its side close to the laser resonant cavity output mirror 7 is the exit surface and is coated with an anti-reflection film of the laser band, and its bottom surface produces total reflection, and couples the laser into the whispering gallery cavity 6 through the evanescent field to achieve frequency selection, and the excitation after frequency selection is continuously reflected in the whispering gallery cavity 6 to form a resonant enhanced laser, and is coupled again through the quartz coupling prism 5 and emitted to the laser resonant cavity output mirror 7.

[0022] As a preferred embodiment, the pump source 1 is a semiconductor laser pump source. The pump source 1 is used to pump the laser gain medium 3 to generate laser oscillation in the resonant cavity.

[0023] As a preference, the laser gain medium 3 is rare earth ion-doped crystal, ceramic or glass.

[0024] As a preferred embodiment, the material of the whispering gallery cavity 6 is CaF2.

[0025] As a preferred embodiment, the material of the whispering gallery cavity 6 is MgF2.

[0026] As a preferred embodiment, the distance between the quartz coupling prism 5 and the whispering gallery cavity 6 is 50-100 nm.

[0027] In the present invention, the whispering gallery is used for frequency selection in the laser resonant cavity, which fully utilizes the advantages of the whispering gallery, such as smaller size, easy integration, and convenient preparation, and can achieve up to 10 9 The extremely high Q value is equivalent to an ultra-narrowband optical filter, which plays a significant role in frequency selection in the laser resonant cavity. This technical solution can not only significantly narrow the line width, but also suppress the noise of the laser resonant cavity, and finally achieve the continuous output of narrow line width laser with narrow line width, low noise and high stability.

[0028] Example:

[0029] The pump light with a wavelength of about 808 nm emitted by the pump source 1 enters through the laser resonant cavity input mirror 2 and irradiates the laser gain medium 3. The laser gain medium 3 is Nd 3+ The Nd:YAG crystal with a doping concentration of 0.6at.% is stimulated to radiate a laser with a wavelength of 1064nm, and is reflected back and forth between the laser cavity input mirror 2 and the laser cavity output mirror 7, thereby repeatedly exciting the laser gain medium 3 to radiate more photons. Since the stimulated radiation light is running back and forth, the laser gain medium 3 is repeatedly used. At the same time, the laser along the axis of the cavity is focused by the lens 4 to adjust the incident angle and then enters the quartz coupling prism 5. Total reflection occurs at the bottom surface of the quartz coupling prism 5 and an evanescent wave is generated at the total reflection point. The evanescent wave is coupled into the whispering gallery cavity 6 which is parallel to the bottom surface of the quartz coupling prism 5 and is 50 to 100nm away to achieve frequency selection. The whispering gallery cavity 6 is actually made of CaF2 material, and the whispering gallery cavity 6 has an extremely high Q value (~10 9 ), the light wave that meets the resonance condition of the whispering gallery is amplified and oscillated in the whispering gallery cavity 6 to form an enhanced laser, and is coupled again by the quartz coupling prism 5 and then emitted from the output surface. The emitted light is output through the laser resonant cavity output mirror 7. In this way, the continuous output of narrow linewidth laser is achieved through the frequency selection effect of the whispering gallery cavity 6 in the cavity.

Claims

1. A narrow linewidth solid-state laser, comprising a pump source (1), a laser resonant cavity input mirror (2), a lens (4) and a laser resonant cavity output mirror (7), characterized in that: It also includes a laser gain medium (3), a quartz coupling prism (5) and a whispering gallery cavity (6); The laser resonant cavity input mirror (2), the lens (4) and the laser resonant cavity output mirror (7) are arranged in sequence along the output direction of the pump source (1); the laser resonant cavity input mirror (2) is coated with a dielectric film with high transmittance to the pump light and high reflectivity to the laser, and the laser resonant cavity input mirror (2) and the laser resonant cavity output mirror (7) form a laser resonant cavity; the lens (4) is coated with a laser band anti-reflection film; The laser gain medium (3) is plated with an anti-reflection film for the pump band and the laser band on the light-transmitting surface thereof, and is arranged on the optical path between the laser resonant cavity input mirror (2) and the lens (4); the laser gain medium (3) is Nd 3+ Nd:YAG crystal with a doping concentration of 0.6at.%; The quartz coupling prism (5) and the whispering gallery cavity (6) are mutually adjacent to a coupling interface and are arranged on an optical path between the lens (4) and the laser resonant cavity output mirror (7); the quartz coupling prism (5) is an isosceles prism, the side surface of which is close to the lens (4) is an incident surface and is coated with an anti-reflection film of the laser band, the side surface of which is close to the laser resonant cavity output mirror (7) is an exit surface and is coated with an anti-reflection film of the laser band, the bottom surface of which generates total reflection, and couples the laser into the whispering gallery cavity (6) through the evanescent field to achieve frequency selection, the excitation after frequency selection is continuously reflected in the whispering gallery cavity (6) to form a resonant enhanced laser, and is coupled again through the quartz coupling prism (5) and then emitted to the laser resonant cavity output mirror (7); The distance between the quartz coupling prism (5) and the whispering gallery cavity (6) is 50 to 100 nm; the material of the whispering gallery cavity (6) is CaF2; The laser light along the axis direction of the resonant cavity is focused by a lens (4) to adjust the incident angle and then enters the quartz coupling prism (5). Total reflection occurs at the bottom surface of the quartz coupling prism (5) and an evanescent wave is generated at the total reflection point. The evanescent wave is coupled into a whispering gallery cavity (6) which is parallel to the bottom surface of the quartz coupling prism (5) and is 50 to 100 nm away to achieve frequency selection.

2. A narrow linewidth solid-state laser according to claim 1, characterized in that: The pump source (1) is a semiconductor laser pump source.

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