Low repetition frequency erbium laser wavelength measuring device and method

Abstract

The invention discloses a low repetition frequency erbium laser wavelength measurement device and method, and belongs to the technical field of laser wavelength measurement. The method comprises the following steps: constructing a test light path consisting of a high-strength substrate, a convergent lens, a KTA crystal, an X-direction precise translation stage, a Y-direction precise translation stage, an angle rotating platform, a collimating lens, a short-wave-pass dichroscope and a spectrograph; the precise translation stage is adjusted to enable the laser to vertically penetrate through the center of the KTA crystal; the angle rotating platform is rotated, so that the angle of the KTA crystal is the optimal phase matching angle; adjusting the position of the spectrograph to enable the frequency-doubled light to be coupled into the spectrograph, and reading the spectrum of the frequency-doubled light; and adjusting different incident energies, and calculating to obtain fundamental frequency light peak wavelengths under different incident energies. Through the second harmonic effect of the KTA crystal, the wavelength of the fundamental frequency laser is halved, the wavelength of the frequency doubling light is measured through the spectrograph, the wavelength of the fundamental frequency Er laser is calculated, and the device has the advantages of being simple in measurement light path, convenient to operate, high in measurement precision and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser wavelength measurement, and particularly relates to a low-repetition-rate erbium laser wavelength measurement device and method. BACKGROUND

[0002] The erbium laser treatment instrument adopts doped erbium yttrium aluminum garnet (Er:YAG) as a laser medium, and outputs a 2.94 μm mid-infrared laser. The wavelength is in a significant region (about 3 μm) of the water molecule absorption spectrum, can be efficiently absorbed by water in biological tissues, so that the penetration depth of the laser in the tissue is shallow, thereby effectively avoiding thermal damage to the surrounding tissue during treatment, and being suitable for the fine medical field such as ophthalmology, dentistry and dermatology. In addition, the device usually works in a low repetition frequency and low energy output mode, which helps to achieve a precise and controllable treatment effect.

[0003] In order to ensure the safety and effectiveness of medical devices, according to the Medical Device Supervision and Management Regulations and the Medical Device Registration and Record Management Measures, erbium laser treatment instruments must pass relevant performance and safety detection before clinical application. The existing detection standards mainly include GB / T 7247.1 Safety of laser products Part 1: Classification and requirements, GB 9706.222 Medical electrical equipment Part 2-22: Particular requirements for the basic safety and basic performance of surgical, cosmetic, therapeutic and diagnostic laser equipment, GB / T 7247.13 Safety of laser products Part 12: Classification measurement of laser products and industry standard YY 1301-2016 Laser treatment equipment Erbium laser treatment machine. Among these standards, wavelength is one of the key parameters, directly affects the penetration ability of laser in tissue, treatment application range and effect evaluation, and is also the basis for safety classification and hazard evaluation of the equipment, so it becomes a necessary item in registration detection.

[0004] In laser wavelength measurement, common methods include interferometry and spectral analysis. Interferometry, such as Fabry-Perot interferometers, Fizeau interferometers, and Michelson interferometers, typically requires a reference beam for accurate measurement, resulting in complex system structures and high requirements for the coherence of the light source. For example, Fabry-Perot interferometers often employ a multi-etalon relay measurement method, but the thickness calibration of the etalons requires extremely high precision. Fizeau interferometers, on the other hand, invert the wavelength by analyzing the initial phase and width of the interference fringes, but are also susceptible to temperature and refractive index fluctuations. The patent "A Laser Wavelength Measurement Device and Method" (publication number CN113607290B) constructs two Fabry-Perot interferometers simultaneously and coordinates them to form a master-slave measurement interference signal, which is then detuned using the optical vernier principle to calculate the laser wavelength. The Fizeau interferometer consists of two plates made of fused silica bonded together with a wedge-shaped spacer. By fixing the wedge angle and spacing on the inner surface of the interference cavity, the initial phase and the width of the interference fringes are measured to obtain the wavelength to be measured. However, in practical applications, variations in temperature, air refractive index, or wedge spacers necessitate the introduction of a reference light source. The patent "Fizeau Interferometer Wavelength Meter and Optical Device for Measuring Lasers" (publication number CN114459618B) obtains the wavelength of the incident laser by analyzing the dense and sparse interference fringe images formed by passing two portions of a parallel beam through a wedge structure after passing through a flat plate. Michelson interferometers measure wavelength by comparing the number of interference fringes between a reference light and a test light, but can only measure the wavelength of continuous lasers. All these measurement methods require a standard reference light source, which places high demands on the source and hinders system integration.

[0005] Analysis reveals that most of the aforementioned laser wavelength measurement methods and patents employ interferometry. However, interferometry requires continuous or repetitive pulsed laser output. The laser wavelength output by low-repetition-rate erbium laser therapy devices is in the mid-infrared region, and with low-repetition-rate single-pulse output, coherence conditions cannot be met, resulting in no relevant signal response from measurement instruments based on coherence methods. Furthermore, methods that directly measure laser wavelength using a spectrometer require a specific wavelength range from which the spectrometer is applicable. Commonly used spectrometers have a near-infrared measurement range and either do not respond to mid-infrared lasers or have slow scanning speeds. Summary of the Invention

[0006] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a low repetition rate erbium laser wavelength measurement device and method.

[0007] The objective of this invention is achieved through the following technical solution: a low-repetition-rate erbium laser wavelength measurement device, comprising: a high-strength substrate, on which are provided an X-axis precision translation stage and a Y-axis precision translation stage, and an angle rotation platform fixed on the Y-axis precision translation stage; a converging lens is provided in the laser incident direction, and a KTA crystal is provided at the right focal point of the converging lens, and the KTA crystal is placed on the angle rotation platform; the position of the KTA crystal is adjusted by the X-axis precision translation stage and the Y-axis precision translation stage, and the orientation angle of the KTA crystal is adjusted by the angle rotation platform; a collimating lens is provided to the right of the KTA crystal, and a short-pass dichroic mirror is provided to the right of the collimating lens; a spectrometer is provided in the reflection direction of the short-pass dichroic mirror.

[0008] The present invention also provides a method for measuring the wavelength of a low-repetition-rate erbium laser, comprising the following steps: Step S1: Construct the test optical path consisting of a converging lens, a KTA crystal, a collimating lens, a short-pass dichroic mirror, and a spectrometer; Step S2: Adjust the position of the KTA crystal so that the laser passes perpendicularly through the center of the KTA crystal after passing through the converging lens; Step S3: Adjust the orientation angle of the KTA crystal to make the KTA crystal angle the optimal phase matching angle; Step S4: Adjust the position of the spectrometer to couple the frequency-doubled light into the spectrometer and read the spectrum of the frequency-doubled light to obtain the peak wavelength λ1 of the frequency-doubled light. Due to the effect of frequency doubling, the peak wavelength of the frequency-doubled light is half of the peak wavelength of the fundamental light, that is, the peak wavelength of the fundamental light λ2 = 2λ1. Step S5: Adjust different incident energies to obtain the peak wavelength of the frequency harmonic light under different incident energy conditions, and calculate the peak wavelength of the fundamental frequency light under different incident energy conditions.

[0009] Furthermore, the KTA crystal is placed on an angle rotation platform, which is fixed to a Y-axis precision translation stage. The Y-axis precision translation stage and the X-axis precision translation stage are fixedly connected. The position of the KTA crystal is adjusted by the X-axis precision translation stage and the Y-axis precision translation stage, and the orientation angle of the KTA crystal is adjusted by the angle rotation platform.

[0010] Furthermore, the KTA crystal has a size of 10mm*10mm*8mm, is coated with a 2940nm antireflection film on both sides, and has a crystal cutting angle of θ=58° and φ=0°; the optimal phase matching angle is θ=55° and φ=0°.

[0011] Furthermore, the converging lens has a focal length of 100mm and a transmission wavelength of 0.18μm-8.0μm.

[0012] Furthermore, the short-pass dichroic mirror has a transmission band of 1000nm-1450nm and a reflection band of 1550nm-2000nm. Its material is ultraviolet fused silica, with a transmittance of >90% in the transmission band, a reflectance of >90% in the reflection band, and an incident angle of 45°.

[0013] Furthermore, the wavelength measurement range of the spectrometer is 900nm-1700nm, and the integration time is 1ms-120s.

[0014] The beneficial effects of this invention are as follows: 1. By using a combination of optical elements, including an incident collimating lens, a laser beam reducer, and an incident converging lens, the fundamental frequency Er lasers from different low-repetition-rate erbium lasers can be incident on a frequency doubling crystal under the same conditions. 2. By setting up a frequency doubling crystal adjustment device, the position of the frequency doubling crystal can be finely adjusted, so that the frequency doubling crystal achieves better phase matching conditions, thereby obtaining better frequency doubling efficiency and realizing a controllable frequency doubling process; 3. By setting up a dichroic mirror and an outgoing collimating lens, it is possible to achieve collimation of only the frequency-doubled beam to the outgoing converging lens. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the optical path constructed in this invention; Figure 3 This is a schematic diagram of the KTA crystal adjustment device of the present invention; Figure 4 The figures shown are actual measurement results of the device built in this invention. In the figure, a is the spectrum of the frequency-doubled light under different input energy conditions, and b is the peak wavelength of the frequency-doubled light under the maximum input energy condition. In the figure: 1. High-strength substrate; 2. Converging lens; 3. KTA crystal; 4. X-axis precision translation stage; 5. Y-axis precision translation stage; 6. Angle rotation platform; 7. Collimating lens; 8. Short-pass dichroic mirror; 9. Spectrometer. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0018] like Figure 2 and Figure 3 As shown, this embodiment of the invention provides a low-repetition-rate erbium laser wavelength measurement device, comprising: a high-strength substrate 1, on which an X-axis precision translation stage 4 and a Y-axis precision translation stage 5 are provided, and an angle rotation platform 6 is fixed on the Y-axis precision translation stage 5; a converging lens 2 is provided in the laser incident direction, and a KTA crystal 3 is provided at the right focal point of the converging lens 2, and the KTA crystal 3 is placed on the angle rotation platform 6. The position of the KTA crystal 3 is adjusted by the X-axis precision translation stage 4 and the Y-axis precision translation stage 5, and the orientation angle of the KTA crystal 3 is adjusted by the angle rotation platform 6; a collimating lens 7 is provided to the right of the KTA crystal 3, and a short-pass dichroic mirror 8 is provided to the right of the collimating lens 7. A spectrometer 9 is provided in the reflection direction of the short-pass dichroic mirror 8.

[0019] The high-strength substrate 1 is a rectangular high-flatness steel plate with dimensions of 1800mm*1200mm*10mm.

[0020] The X-axis precision translation stage has a maximum stroke of 600mm and a motion accuracy of 10μm. It is fixed to the high-strength substrate with screws and is used to support the Y-axis precision translation stage and realize horizontal movement in the X direction.

[0021] The Y-axis precision translation stage has a maximum stroke of 600mm and a motion accuracy of 10μm. It is fixed to the center position of the X-axis precision translation stage with screws. It is used to support the angle rotation platform and realize vertical movement in the Y direction.

[0022] The X-axis precision translation stage, the Y-axis precision translation stage, and the angle rotation platform together form the KTA crystal adjustment device, which is used for fine-tuning the crystal position.

[0023] like Figure 1 As shown, based on the above-described apparatus, this embodiment of the invention also provides a method for measuring the wavelength of a low-repetition-rate erbium laser, comprising the following steps: Step S1: Construct a test optical path consisting of a high-strength substrate 1, a converging lens 2, a KTA crystal 3, an X-axis precision translation stage 4, a Y-axis precision translation stage 5, an angle rotation platform 6, a collimating lens 7, a short-pass dichroic mirror 8, and a spectrometer 9. The high-strength substrate 1 is a rectangular, highly flat steel plate with dimensions of 1800mm*1200mm*10mm. An X-axis precision translation stage 4 is placed on the high-strength substrate 1, with a maximum travel of 600mm and a motion accuracy of 10μm. A converging lens 2 is positioned 100mm to the right of the laser output window in the laser incident direction. The converging lens 2 is a 1μm-3μm mid-infrared laser plano-convex lens with a focal length of 100mm. A KTA crystal 3 is positioned at the right focal point of the converging lens 2. The KTA crystal 3 has dimensions of 10mm*10mm*8mm, is coated with a 2940nm antireflection film on both sides, and has a crystal cutting angle of θ=58° and φ=0°. The KTA crystal 3 is vertically placed on the angle rotation platform 6, which allows the crystal to rotate. The angle rotation platform 6 is fixed on the Y-axis precision translation stage 5, which has a maximum stroke of 600 mm and a motion accuracy of 10 μm, allowing movement in the Y direction. The Y-axis precision translation stage 5 is fixed on the X-axis precision translation stage 4, allowing movement in the X direction. A collimating lens 7 is placed 120 mm to the right of the KTA crystal 3 for collimating the divergent frequency-doubled light. A short-pass dichroic mirror 8 is placed to the right of the collimating lens 7. The short-pass dichroic mirror 8 has a transmission band of 1000nm-1450nm and a reflection band of 1550nm-2000nm. It is made of ultraviolet fused silica, with a transmittance >90% in the transmission band and a reflectance >90% in the reflection band. The angle between the short-pass dichroic mirror 8 and the collimating lens 7 is 45°. A spectrometer 9 is positioned in the direction of reflection from the short-pass dichroic mirror 8. The spectrometer 9 has a wavelength measurement range of 900nm-1700nm and an integration time of 1ms-120s.

[0024] Step S2: Adjust the X-axis precision translation stage 4 and the Y-axis precision translation stage 5 so that the laser passes perpendicularly through the center of the KTA crystal 3, and at the same time make the KTA crystal 3 within the focal length to the right of the converging lens 2, so that the fundamental frequency Er laser undergoes a second harmonic effect in the KTA crystal 3 to obtain frequency-doubled light.

[0025] Step S3: Rotate the angle rotating platform 6 so that the KTA crystal 3 has the optimal phase matching angle θ=55° and φ=0°; adjust the position of the collimating lens 7 so that it is 120mm away from the right side of the KTA crystal 3 to collimate the diverging beam emitted from the KTA crystal 3. A short-pass dichroic mirror 8 is set on the right side of the collimating lens 7. The angle between the short-pass dichroic mirror 8 and the collimating lens 7 is 45°. The fundamental frequency Er light and the frequency-doubled light are separated by the short-pass dichroic mirror 8.

[0026] Step S4: Adjust the position of the spectrometer 9 to ensure that the frequency-doubled light is successfully coupled into the spectrometer 9, and read the spectrum of the frequency-doubled light to obtain the peak wavelength λ1 of the frequency-doubled light. Due to the influence of the frequency doubling effect, it can be known that the peak wavelength of the frequency-doubled light is half of the peak wavelength of the fundamental light, that is, the peak wavelength of the frequency-doubled light λ2 = 2λ1.

[0027] Step S5: Adjust different incident energies to obtain the peak wavelength of the frequency harmonic light under different incident energy conditions, and calculate the peak wavelength of the fundamental frequency light under different incident energy conditions.

[0028] As a preferred embodiment, the following specific experiments were conducted based on the device of the present invention: The nominal wavelength of the fundamental frequency Er laser is known to be 2940 nm. The peak wavelength of the frequency-doubled light, as measured by the present invention, is 1470 nm. Since the peak wavelength of the frequency-doubled light λ2 = 2λ1, it can be concluded that the wavelength of the fundamental frequency light is the same as the nominal value. Figure 4 Figures a and b are shown. The fundamental frequency Er laser wavelength was measured under different incident energy conditions, while the peak wavelength remained constant.

[0029] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only.

[0030] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A low-repetition-rate erbium laser wavelength measurement device, characterized in that, include: A high-strength substrate (1) is provided with an X-axis precision translation stage (4) and a Y-axis precision translation stage (5). An angle rotation platform (6) is fixed on the Y-axis precision translation stage (5). A converging lens (2) is provided in the laser incident direction. A KTA crystal (3) is provided at the right focal point of the converging lens (2). The KTA crystal (3) is placed on the angle rotation platform (6). The position of the KTA crystal (3) is adjusted by the X-axis precision translation stage (4) and the Y-axis precision translation stage (5). The orientation angle of the KTA crystal (3) is adjusted by the angle rotation platform (6). A collimating lens (7) is provided on the right side of the KTA crystal (3). A short-pass dichroic mirror (8) is provided on the right side of the collimating lens (7). A spectrometer (9) is provided in the reflection direction of the short-pass dichroic mirror (8).

2. A method for measuring the wavelength of a low-repetition-rate erbium laser, characterized in that, Includes the following steps: Step S1: Construct a test optical path consisting of a converging lens (2), a KTA crystal (3), a collimating lens (7), a short-pass dichroic mirror (8), and a spectrometer (9); Step S2: Adjust the position of the KTA crystal (3) so that the laser passes perpendicularly through the center of the KTA crystal (3) after passing through the converging lens (2); Step S3: Adjust the orientation angle of the KTA crystal (3) so that the angle of the KTA crystal (3) is the optimal phase matching angle; Step S4: Adjust the position of the spectrometer (9) so that the frequency-doubled light is coupled into the spectrometer (9) and read the frequency-doubled light spectrum to obtain the peak wavelength λ1 of the frequency-doubled light and the peak wavelength λ2 of the fundamental light = 2λ1; Step S5: Adjust different incident energies to obtain the peak wavelength of the frequency harmonic light under different incident energy conditions, and calculate the peak wavelength of the fundamental frequency light under different incident energy conditions.

3. The method according to claim 2, characterized in that, The KTA crystal (3) is placed on the angle rotation platform (6), which is fixed on the Y-axis precision translation stage (5). The Y-axis precision translation stage (5) and the X-axis precision translation stage (4) are fixedly connected. The position of the KTA crystal (3) is adjusted by the X-axis precision translation stage (4) and the Y-axis precision translation stage (5), and the orientation angle of the KTA crystal (3) is adjusted by the angle rotation platform (6).

4. The method according to claim 2, characterized in that, The KTA crystal (3) has a size of 10mm*10mm*8mm, and is coated with a 2940nm antireflection film on both sides. The crystal cutting angle is θ=58° and φ=0°. The optimal phase matching angle is θ=55° and φ=0°.

5. The method according to claim 2, characterized in that, The converging lens (2) has a focal length of 100mm and a transmission wavelength of 0.18μm-8.0μm.

6. The method according to claim 2, characterized in that, The short-pass dichroic mirror (8) has a transmission band of 1000nm-1450nm and a reflection band of 1550nm-2000nm. Its material is ultraviolet fused silica. The transmittance in the transmission band is >90%, the reflectance in the reflection band is >90%, and the incident angle is 45°.

7. The method according to claim 2, characterized in that, The wavelength measurement range of the spectrometer (9) is 900nm-1700nm, and the integration time is 1ms-120s.

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