A bichromatic Gaussian output mirror for OPO laser and a manufacturing method thereof

Abstract

The application discloses a bichromatic Gaussian output mirror for an OPO laser and a manufacturing method, wherein the edge of the Gaussian output mirror is anti-reflective to 1065nm / 1570nm, the center of the Gaussian output mirror is anti-reflective to 1065nm, the reflectivity of the center of the Gaussian output mirror to 1570nm is about 60%, and the transition zone is according to high-order Gaussian distribution; the output mirror can improve the efficiency and beam quality of 1570nm of the OPO laser. According to the application, the output mirror with the reflectivity of two wavelengths is designed according to the laser, the double-side anti-reflective film is plated according to the conventional method, the double-wavelength film is plated in the center of the output mirror, 1065nm is low-reflective, and 1570nm is reflective at about 60%. The application can have higher beam quality than the conventional OPO laser.

Description

Technical Field

[0001] This invention belongs to the field of optical component design and fabrication, and relates to a dual-color Gaussian output mirror for OPO lasers and its fabrication method. By fabricating a regular film layer with a special structure, the 1065nm Gaussian film is extended to a 1570nm output mirror, achieving better beam quality than conventional OPO lasers. Background Technology

[0002] 1065nm Q-switched lasers have been widely used in various civilian and military fields, such as laser ranging, target designation, and laser processing. Recent developments have placed increasingly higher demands on the laser's output, with improvements manifested in aspects such as output energy, beam quality, and divergence angle.

[0003] With the widespread civilian use of these lasers, the damaging effects of 1065nm lasers on the human eye have become apparent. Occasionally, there have been reports of eye injuries and blindness among laser users. To address this issue, eye-safe lasers with wavelengths above 1500nm have been vigorously developed over the past decade. Currently, there are three main methods for generating eye-safe lasers around 1550nm: methane Raman shift, Er glass, and optical parametric oscillation (OPO). Methane is rarely used due to the need for high-pressure gas pipes and potential leakage issues. Er glass is prone to deliquescence and has poor environmental adaptability. OPO has become the primary method for eye-safe lasers.

[0004] Most current technologies focus on improving the beam quality of lasers. In the early stages, unstable cavities were mainly used to compensate for thermal effects. In recent years, references [1]-

[15] have discussed the influence of the characteristic parameters of the Gaussian film itself, such as the size of the central spot, the order of Gaussian, and the central reflectivity, on circular lasers or slab lasers in various ways. Their goal is to improve the beam quality of the laser output.

[0005] However, all current Gaussian films are designed as single-wavelength films, namely 1065nm fundamental frequency laser Gaussian films. After passing through the OPO, the 1570nm light that oscillates and diffracts in the OPO crystal is newly generated, and the beam quality will degrade, becoming inferior to the original fundamental frequency light. Only by designing the Gaussian mirror on the 1570nm output mirror can the beam quality of the output laser be effectively improved. A Gaussian output mirror that can directly adjust the beam quality of the 1570nm beam is needed. Summary of the Invention

[0006] (I) Purpose of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing OPO laser beam quality by designing a dual-color Gaussian output mirror for OPO lasers and its fabrication method, which achieves high transmittance at 1065nm, partial reflection and output of the laser at 1570nm, and the Gaussian film system is only effective at 1570nm.

[0008] (II) Technical Solution

[0009] To solve the above-mentioned technical problems, the present invention provides a dual-color Gaussian output mirror for OPO lasers, which adopts a fully regular film system, with anti-reflection at the edge for 1065nm / 1570nm wavelength, anti-reflection at the center for 1065nm, and a reflectivity of 60±5% for 1570nm.

[0010] The central Gaussian region film structure needs to meet the special requirement of simultaneously achieving high transmittance at 1065nm and half-reflection at 1570nm on a film system superimposed on the edge at dual wavelengths of 1065nm / 1570nm. A special structure, G / MHLxHxLxH / A, was designed, where M represents Al₂O₃, H represents ZrO₂, L represents SiO₂, and x represents the Gaussian film layer. The edge G / MHL / A structure achieves low reflectance at both wavelengths. Figure 1 The three-layer gradient coating at the center achieves low reflection at 1065nm and simultaneous half-reflection at 1570nm. Figure 2 The reflectivity of a semi-reflective film can be adjusted by changing the process parameters and adjusting the refractive index of the film layer between 55% and 65% to adapt to different gain media without changing the film structure.

[0011] The Gaussian gradient region is achieved by a three-layer film, which greatly improves the hardness compared to a conventional single-layer film. It has the same hardness as the central region film system and has good mechanical properties.

[0012] This invention also provides a method for fabricating a dual-color Gaussian output mirror for an OPO laser, comprising the following steps:

[0013] (1) Based on the design theory of lasers, determine the parameters of the laser, such as the central reflectivity, the diameter of the central flat top area, and the reflectivity gradient area.

[0014] (2) Based on the edge dual-wavelength anti-reflection requirement, a three-layer regular dual-wavelength anti-reflection film of G / MHL / A is designed, where M is Al2O3, H is ZrO2, L is SiO2, the reference wavelength is 1350nm, and dual-wavelength anti-reflection of 1065nm and 1570nm is achieved.

[0015] (3) A three-layer regular film system is superimposed on the three-layer regular structure of G / MHL / A, and the design becomes G / MHLxHxLxH / A, where x represents the Gaussian film layer. This special structure maintains low reflectivity at 1065nm and reflectivity of about 60% at around 1570nm.

[0016] (4) G / MHL / A film system was deposited on both sides using a coating machine according to conventional methods. The actual reflectance is shown in the figure. Figure 3 It achieves a residual reflectivity of less than 0.5% at 1065nm and 1570nm.

[0017] (5) Mount the lens on a special mask fixture, and deposit three layers of Gaussian film xHxLxH on the Gaussian surface according to the structure in step (3). The actual reflectivity is shown in the figure. Figure 4 It achieves a residual reflectivity of less than 1.5% at 1065nm and a reflectivity of about 60% at 1570nm. The red curve represents the reflectivity of the xHxLxH structure alone, which is about 45%.

[0018] (6) Using a nanoindenter to test the center of the Gaussian mirror, the hardness of three points with different diameters on the gradient region is 7-8 GPa, which is comparable to the thickness of ordinary ion beam-assisted film. This solves the shortcomings of conventional single-wavelength Gaussian film with low edge strength and easy peeling after wiping.

[0019] (III) Beneficial Effects

[0020] The above technical solution provides a dual-color Gaussian output mirror for OPO lasers and its manufacturing method. Based on the laser design, two output mirrors with corresponding wavelength reflectivities are designed. A double-sided anti-reflection film is deposited using conventional methods. A dual-wavelength film is deposited at the center of the output mirror to achieve low reflection at 1065nm and approximately 60% reflection at 1570nm. Attached Figure Description

[0021] Figure 1 Spectral diagram of the center design of the dual-wavelength Gaussian mirror.

[0022] Figure 2 Design diagram of G / MHL / A dual-wavelength antireflective coating.

[0023] Figure 3 G / MHL / A dual-wavelength antireflective film test spectrum

[0024] Figure 4 Central spectrum of a dual-wavelength Gaussian mirror.

[0025] Figures 5 to 8 The images show the hardness distribution at the center of the dual-wavelength Gaussian mirror, in gradient region 1, gradient region 2, and gradient region 3, respectively. Detailed Implementation

[0026] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0027] See Figure 1The present invention relates to a dual-wavelength Gaussian graded reflector and its manufacturing method, which comprises the following steps:

[0028] (1) Based on the design theory of lasers, determine the parameters of the laser, such as the central reflectivity, the diameter of the central flat top area, and the reflectivity gradient area.

[0029] (2) Based on the edge dual-wavelength anti-reflection requirement, a three-layer regular dual-wavelength anti-reflection film of G / MHL / A is designed, where M is Al2O3, H is ZrO2, L is SiO2, the reference wavelength is 1350nm, and dual-wavelength anti-reflection of 1065nm and 1570nm is achieved.

[0030] (3) A three-layer regular film system is superimposed on the three-layer regular structure of G / MHL / A, and the design becomes G / MHLxHxLxH / A, where x represents the Gaussian film layer. This special structure maintains low reflectivity at 1065nm and reflectivity of about 60% at around 1570nm.

[0031] (4) G / MHL / A film system was deposited on both sides using a coating machine according to conventional methods. The actual reflectance is shown in the figure. Figure 3 It achieves a residual reflectivity of less than 0.5% at 1065nm and 1570nm.

[0032] (5) Mount the lens on a special mask fixture, and deposit three layers of Gaussian film xHxLxH on the Gaussian surface according to the structure in step (3). The actual reflectivity is shown in the figure. Figure 4 It achieves a residual reflectivity of less than 1.5% at 1065nm and a reflectivity of about 60% at 1570nm. The red curve represents the reflectivity of the xHxLxH structure alone, which is about 45%.

[0033] (6) Using a nanoindenter to test the center of the Gaussian mirror, the hardness of three points with different diameters on the gradient region is 7-8 GPa, which is comparable to the thickness of ordinary ion beam-assisted film. This solves the shortcomings of conventional single-wavelength Gaussian film with low edge strength and easy peeling after wiping.

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dual-color Gaussian output mirror for an OPO laser, characterized in that, The fully regular film system is used, with antireflection at the edges for wavelengths of 1065nm / 1570nm, antireflection at the center for 1065nm, and a reflectivity of 60±5% for 1570nm. The film system is deposited by superimposing the film structure in the central Gaussian region. The structure is: G / MHLxHxLxH / A, where M is Al2O3, H is ZrO2, L is SiO2, and x represents the Gaussian film layer. The edge membrane structure is: G / MHL / A.

2. The dual-color Gaussian output mirror for an OPO laser as described in claim 1, characterized in that, The Gaussian gradient region is achieved by three layers of film, and has the same hardness as the central region film system.

3. A method for manufacturing a dual-color Gaussian output mirror for an OPO laser based on the description in claim 2, characterized in that, Includes the following steps: S1: Based on the laser design theory, determine the laser's central reflectivity, central flat-top diameter, and reflectivity gradient parameters; S2: Based on the edge dual-wavelength antireflection requirement, a three-layer regular dual-wavelength antireflection film of G / MHL / A is designed, where M is Al2O3, H is ZrO2, and L is SiO2; S3: A three-layer regular film system is superimposed on the three-layer regular structure of G / MHL / A, and the design becomes G / MHLxHxLxH / A, where x represents a Gaussian film layer; S4: Use a coating machine to coat both sides of the output mirror with G / MHL / A film system; S5: Mount the output mirror on the mask fixture, and deposit three layers of Gaussian film xHxLxH on the Gaussian surface according to the structure of step S3.

4. The method for fabricating a dual-color Gaussian output mirror for an OPO laser as described in claim 3, characterized in that, In step S2, the reference wavelength is 1350nm, achieving dual-wavelength anti-reflection at 1065nm and 1570nm.

5. The method for fabricating a dual-color Gaussian output mirror for an OPO laser as described in claim 4, characterized in that, In step S4, the output mirror is coated with G / MHL / A films on both sides to achieve a residual reflectivity of less than 0.5% at 1065nm and 1570nm.

6. The method for fabricating a dual-color Gaussian output mirror for an OPO laser as described in claim 5, characterized in that, In step S5, three layers of Gaussian film xHxLxH are deposited on the Gaussian surface to achieve a residual reflectivity of less than 1.5% at 1065nm and a reflectivity of 60±5% at 1570nm.

7. The method for fabricating a dual-color Gaussian output mirror for an OPO laser as described in claim 6, characterized in that, In step S6, the hardness of the three points with different diameters at the center of the Gaussian mirror and on the gradient region is all between 7 and 8 GPa.

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