Gain compensation sampling device for spectrum synthesis fiber laser

Abstract

The present invention relates to the field of high-power fiber lasers, and provides a gain compensation sampling device suitable for spectrum synthesis fiber lasers. The device comprises a spectrum synthesis fiber laser, a main spectroscope, a reflector, a main power meter, a sampling lens, and a light spot collection device. The device simultaneously realizes the power measurement of the spectrum synthesis fiber laser and the weak light sampling function, and the optical path is simple and easy to implement. The device can reduce the variation amplitude of the sampling light intensity, effectively compensate for the intensity difference of laser components of different wavelengths in the sampling light, and improve the accuracy of the test.

Description

Technical Field

[0001] The present invention relates to the technical field of high-power lasers, and more specifically to a gain compensation sampling device for spectrum synthesis fiber lasers. Background Art

[0002] High brightness fiber lasers have broad application prospects in the fields of industry, medicine, and national defense. Spectral synthesis technology uses gratings or dichroic mirrors to synthesize multiple wavelengths of laser into one beam, while obtaining high power and good beam quality, which has great development prospects. Among them, the precise calibration of spectral synthesis lasers and the measurement of beam quality are important topics in this field.

[0003] During both calibration and measurement, the synthetic light beam needs to be incident on the spot collection device. Since the core imaging element of the spot collection device is a silicon-based detector, its power threshold is relatively low. Therefore, a main beam splitter with a high-reflection film coated on the surface is generally used to reflect the high-power laser, and the transmitted sampling weak light is incident on the spot collection device. The power of the sampled weak light requires a higher power stability, which can be used for power monitoring and beam quality testing of high-power lasers. As in the prior art (such as CN214706569 U, a high-power laser testing device), the high-power laser uses a 45-degree beam splitter (that is, the incident light is perpendicular to the reflected light angle) for sampling and monitoring. The reflective surface of the beam splitter is coated with a laser band high-reflection film, and the transmission surface is coated with a laser band anti-reflection film. There are two problems with this scheme when used for spectral synthesis laser beam quality measurement. First, due to the influence of the laser polarization state, the laser transmission power jitter is large when incident at a large angle (such as 45 degrees), and the accuracy is not high; second, the spectrum of the spectral synthesis laser contains multiple wavelengths in the range of 1030nm to 1090nm, and the spectral response of the silicon-based detector in this band shows a sharp downward trend. As a result, the gain response of these wavelengths on the silicon-based detector varies greatly. Generally, the gain response of the short-wave band (such as 1030nm) is about 3-5 times stronger than that of the long-wave band (such as 1090nm). This brings great difficulties to the calibration of spectral synthesis and the measurement of beam quality, thereby affecting the imaging effect of the synthetic light spot and the results of the synthetic beam quality measurement.

[0004] The weak light sampling scheme currently common in this field has two problems for spectral synthesis of high-power fiber laser light sources. The first is that the main beam splitter has a 45-degree sampling light path, and its sampling light intensity stability is poor. Secondly, the transmission surface of the main beam splitter is generally coated with an anti-reflection film, which has the same anti-reflection effect in the 1030nm-1090nm band of fiber lasers. Since the gain response curve of the silicon-based detector in the 1um band shows a sharp downward trend, the gain response of the spot collection device will be stronger near the short-wave 1030nm, while the gain response will be weaker near the long-wave 1090nm. This will affect the imaging effect of the synthetic light spot and the results of the synthetic beam quality measurement. Summary of the invention

[0005] In view of the above problems, the present invention proposes a gain compensation sampling device for spectral synthesis fiber laser, which solves the problems of large jitter and low accuracy of laser transmission power through small-angle reflection of the main beam splitter; a gain compensation film is plated on the back of the main beam splitter to meet the requirement of consistency of intensity of different wavelengths in the spectral synthesis sampling beam, and solves the technical problem of significant difference in gain response with wavelength in the light spot acquisition equipment.

[0006] The purpose of the present invention can be achieved by the following technical measures:

[0007] The gain compensation sampling device of the spectrum synthesis fiber laser comprises a spectrum synthesis fiber laser, a main beam splitter, a reflector, a main power meter, a sampling lens and a light spot collection device. The spectrum synthesis fiber laser is divided into two beams after passing through the main beam splitter, wherein the first beam reflected at a small angle contains the main power of the laser and is incident on the main power meter through the reflector; the sampling beam transmitted by the main beam splitter is the second beam and is incident on the light spot collection device through the sampling lens; wherein the reflection surface S1 is coated with a high reflection film of the laser, and the transmission surface S2 is coated with a gain compensation film of the laser. The main beam splitter reflects the spectrum synthesis fiber laser at a small angle, and the angle θ between the incident light and the first beam satisfies 5°<θ<15°. The transmission surface of the main beam splitter is coated with a gain compensation film, and the transmittance of the film layer gradually increases from 1030nm to 1090nm.

[0008] The main beam splitter is a wedge-shaped mirror or a prism, and is coated on both sides.

[0009] The spectrum synthesis fiber laser is a collimated light beam, and its spectrum contains more than two narrow spectrum wavelengths.

[0010] The light spot acquisition device may be a CCD or CMOS camera, or a power meter.

[0011] Compared with the prior art, it has the following beneficial effects:

[0012] The device can simultaneously realize spectrum synthesis fiber laser power measurement and weak light sampling, and the optical path is simple and easy to implement. The device can effectively compensate for the intensity difference of laser components of different wavelengths in the sampling light while reducing the amplitude of the sampling light intensity variation, thereby improving the accuracy of beam quality testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic structural diagram of a gain compensation sampling device for a spectrum synthesis fiber laser provided in an embodiment of the present invention.

[0014] Figure 2 It is a schematic diagram of double-sided coating of the main beam splitter provided by an embodiment of the present invention.

[0015] Figure 3 is the 5-degree incident main beam splitter optical path provided by the embodiment of the present invention (at this time Figure 1 The included angle θ between the incident light and the first light beam is 10 degrees), and the coating transmittance of the transmission surface varies with the wavelength.

[0016] Figure 4 This is a graph showing the variation of the sampling power of the fiber laser with a wavelength of 1060 nm provided by an embodiment of the present invention with respect to time when the main beam splitter is at 5 degrees and 45 degrees.

[0017] In the figure: 1. Spectral synthesis fiber laser; 2. Main beam splitter; 3. Reflector; 4. Main power meter; 5. Sampling lens; 6. Light spot collection device; S1. Reflection surface; S2. Transmission surface. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] In order to make the description of the present disclosure more detailed and complete, the following provides an illustrative description of the implementation and specific embodiments of the present invention; however, this is not the only form of implementing or using the specific embodiments of the present invention. The implementation covers the features of multiple specific embodiments and the method steps and sequences used to construct and operate these specific embodiments. However, other specific embodiments can also be used to achieve the same or equivalent functions and step sequences.

[0020] See also Figure 1 As shown, a gain compensation sampling device for a spectrum synthesis fiber laser comprises a spectrum synthesis fiber laser 1, a main beam splitter 2, a reflector 3, a main power meter 4, a sampling lens 5 and a light spot collection device 6. The spectrum synthesis fiber laser is divided into two beams after passing through the main beam splitter 2. The first beam reflected at a small angle contains the main power of the laser and is incident on the main power meter 4 through the reflector 3; the sampling beam passing through the main beam splitter 2 is the second beam and is incident on the light spot collection device 6 through the sampling lens 5; the main beam splitter 2 is a wedge-shaped mirror or a prism, and is coated on both sides. The reflection surface S1 of the main beam splitter 2 is coated with a high-reflection film for the laser, and the transmission surface S2 is coated with a gain compensation film for the laser. Please refer to Figure 2, as shown. The laser is incident at a small angle on the main beam splitter with a wedge angle. The main beam splitter is coated on both sides. The reflection surface S1 is coated with a high-reflection film for the laser, and the transmission surface S2 is coated with a gain compensation film for the laser. The transmittance of the gain compensation film gradually increases from 1030nm to 1090nm, and the gain response on the spot collection device is compensated in advance. This technical solution can effectively compensate for the intensity difference of laser components of different wavelengths in the sampling light while reducing the variation amplitude of the sampling light intensity, thereby improving the accuracy of the beam quality test.

[0021] This embodiment measures the power of transmitted light when using a 45-degree main beam splitter and a 5-degree main beam splitter, respectively, to compare the difference between the prior art (hereinafter referred to as: 45-degree sampling optical path) and the solution of the present invention (hereinafter referred to as 5-degree sampling optical path). The reflective surface of the 45-degree main beam splitter is coated with a 1030nm-1090nm high-reflective film, and the transmission surface is coated with a 1030nm-1090nm anti-reflection film; the reflective surface of the 5-degree main beam splitter is coated with a 1030nm-1090nm high-reflective film, and the transmission surface is coated with a 1030nm-1090nm gain compensation film. The transmittance of the gain compensation film increases gradually from 1030nm to 1090nm, and the transmittance near 1060nm is 22%, and the transmittance near 1072nm is 82%. Figure 3 shown.

[0022] The light source for experiment 1 is a 1060nm non-polarized fiber laser with a light emission time of 150 seconds. The transmission power after the main beam splitter is tested. At this time, the spot acquisition device 6 is a 5W range power meter. The measurement results are as follows: Figure 4 It can be seen that the power stability is poor when using the 45-degree sampling optical path of the prior art, while the power stability is significantly improved when using the 5-degree sampling optical path of the present invention.

[0023] The light source of Experiment 2 is a non-polarized fiber laser with a spectrum synthesis of 1060nm and 1072nm wavelengths. When using the 45-degree sampling optical path of the prior art, the transmission power of the 1060nm wavelength laser is 210mW, and the transmission power of the 1072nm wavelength laser is 180mW. The spot acquisition device 6 is replaced with a CCD (model Ophir SP928), and the attenuation parameters of the CCD are adjusted so that the sampling spot of the 1060nm wavelength laser is displayed normally. However, since the gain response of the silicon-based detector decreases with wavelength, the 1072nm wavelength laser on the CCD is very weak and cannot be seen by the naked eye.

[0024] When Experiment 2 uses the 5-degree sampling optical path of the present invention, since the S2 surface of the main beam splitter 2 is coated with a gain compensation film, the transmission power of the 1060nm wavelength laser is 60mW, and the transmission power of the 1072nm wavelength laser is 180mW. The spot acquisition device 6 is replaced with a CCD (model Ophir SP928), and the attenuation parameters of the CCD are adjusted so that the sampling spot of the 1060nm wavelength laser is displayed normally. Although the gain response of the silicon-based detector decreases with the wavelength, since the S2 surface is gain compensated for the wavelength in advance, the intensity of the 1072nm wavelength laser on the CCD is almost the same as that of the 1060nm wavelength laser.

[0025] Based on the measurement results of spectrum synthesis laser sampling in the above embodiments, and comparing the prior art with the technical solution of the present invention, it can be seen that the latter has a higher consistency in the visible intensity of lasers of different wavelengths on the spot acquisition device 6 (CCD), which is conducive to improving the calibration accuracy of spectrum synthesis laser and the accuracy of beam quality measurement. The technical solution of the present invention has been verified and applied in actual scientific research and engineering practice.

[0026] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A gain compensation sampling device for a spectrum synthesis fiber laser, comprising a spectrum synthesis fiber laser, a main beam splitter, a reflector, a main power meter, a sampling lens and a spot collection device, characterized in that: The reflection surface (S1) of the main beam splitter is coated with a high reflection film of the spectrum synthesis fiber laser, and the transmission surface (S2) of the main beam splitter is coated with a gain compensation film of the spectrum synthesis fiber laser, and the film transmittance of the gain compensation film gradually increases from 1030nm to 1090nm; The spectral synthesis fiber laser is incident on the main beam splitter and is divided into two beams by the main beam splitter, namely a reflected beam and a transmitted beam, and the angle between the reflected beam and the incident light is in the range of 5° to 15°; the reflected beam contains the main power of the laser and is received by the main power meter after being reflected by the reflector; the transmitted beam is collected by the light spot collection device after being transmitted by the sampling lens.

2. The gain compensation sampling device for spectrum synthesis fiber laser according to claim 1, characterized in that: The main beam splitter is a wedge-shaped mirror or a prism.

3. The gain compensation sampling device for spectrum synthesis fiber laser according to claim 1, characterized in that: The spectrum synthesis fiber laser is a collimated light beam, and the spectrum contains more than two narrow spectrum wavelengths.

4. The gain compensation sampling device for spectrum synthesis fiber laser according to claim 1, characterized in that: The light spot acquisition device is a CCD, CMOS camera or a power meter.

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