A wavelength tunable high power near-infrared laser and working method

Abstract

The application relates to a wavelength-tunable high-power near-infrared laser and a working method, the laser comprises an input mirror, a semiconductor laser module, a first laser crystal, an intracavity mirror, a second laser crystal and an output mirror which are sequentially connected, the semiconductor laser module is arranged around the first laser crystal and emits pump light, the pump light enters the first laser crystal through the input mirror; the first laser crystal is excited by the pump light to generate stimulated radiation, intracavity oscillation laser is formed, the intracavity oscillation laser is processed through the intracavity mirror and the second laser crystal in sequence, and finally is output through the output mirror, wavelength-tunable high-power near-infrared laser is obtained, and the temperature of the second laser crystal is regulated by using a temperature control module. The wavelength-tunable high-power near-infrared laser is obtained in the mode of intracavity pumping and temperature control, and has the advantages of high output power, high optical-optical conversion efficiency, wavelength tunability and good beam quality.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, specifically relating to a wavelength-tunable high-power near-infrared laser and its operating method. Background Technology

[0002] Currently, most lasers in the 700nm-850nm range have fixed wavelength outputs and cannot be continuously tuned. If different wavelengths are required, multiple devices must be combined, resulting in large system size, high cost, and complex control, making it difficult to achieve continuous spectral scanning. A few tunable solutions, such as external cavity semiconductor lasers, have extremely narrow tuning ranges, typically only 5nm-15nm, which cannot cover the wide 700nm-800nm ​​band, and they rely on mechanical tuning, resulting in slow response, poor vibration resistance, and low stability.

[0003] Meanwhile, light sources in this band generally have low power and poor optical-to-optical conversion efficiency. On the one hand, the power of a single semiconductor tube is limited, and the beam quality deteriorates after beam combining; on the other hand, solid-state frequency doubling schemes (the optical-to-optical conversion efficiency of 1064nm to 532nm is about 45%, and the optical-to-optical conversion efficiency of 700-800nm ​​obtained by optical parametric oscillation at 532nm is about 30%) typically have an efficiency of less than 20%, serious thermal effects, and are prone to wavelength drift and mode instability at high power; fiber lasers have insufficient gain and high loss in this band, and the loss increases further after adding tuning elements, further limiting efficiency and power.

[0004] Therefore, none of the existing technical approaches can guarantee that 700nm-800nm ​​lasers can simultaneously achieve wide-range continuous tuning, high power, high efficiency, and high stability, which severely restricts the performance improvement of lasers in this frequency band. There is an urgent need for a new type of tunable high-power near-infrared laser to solve the above problems. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the present invention provides a wavelength-tunable high-power near-infrared laser and a working method to solve the current problems.

[0006] A wavelength-tunable high-power near-infrared laser includes an input mirror, a semiconductor laser module, an endoscope, a first laser crystal, a second laser crystal, and an output mirror connected in sequence. The semiconductor laser module and the first laser crystal are disposed between the input mirror and the endoscope. The semiconductor laser module is arranged around the first laser crystal and emits pump laser. The pump laser enters through the input mirror and is incident on the first laser crystal. The first laser crystal is pumped to generate stimulated emission, forming an intracavity oscillating laser. The intracavity oscillating laser then passes through the intracavity mirror and the second laser crystal in sequence, and is finally output by the output mirror to obtain a wavelength-tunable high-power near-infrared laser. The wavelength of the near-infrared laser can be changed with the temperature of the second laser crystal.

[0007] In addition to the aspects and any possible implementations described above, a further implementation is provided, which further includes a temperature control module and a TEC module, wherein the TEC module is attached to the second laser crystal, and the temperature control module is electrically connected to the TEC module for controlling the temperature of the TEC module.

[0008] In addition to the aspects described above and any possible implementations, an implementation is further provided in which the first laser crystal and the second laser crystal have identical structures.

[0009] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the laser outputs a near-infrared laser with a frequency range of 700nm-850nm.

[0010] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the photo-optical conversion efficiency of the near-infrared laser is greater than 25%.

[0011] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the input mirror has an optical aperture of 20 mm, a coating thickness of 523 nm, a reflectivity of ≥99.5%, a wavelength of 700-850 nm, and a transmittance of ≥99%.

[0012] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the semiconductor laser module is a cylinder with an overall size of Φ5mm × 60mm.

[0013] In addition to the aspects and any possible implementations described above, a further implementation is provided in which both the first laser crystal and the second laser crystal are cuboids with a length, width, and height of 25mm × 6mm × 6mm, respectively.

[0014] This invention also provides a method for operating a wavelength-tunable high-power near-infrared laser. The method, implemented using the aforementioned laser, includes the following steps: After power is switched on, the semiconductor laser module of the laser is electrically excited to generate a laser of a first wavelength. The first laser crystal is excited by side pumping. The first laser crystal, the input mirror, and the output mirror work together to generate a laser of a second wavelength, which serves as the pump light. This pump light excites the second laser crystal to generate signal light within a certain frequency range. This signal light is amplified and output under the action of the cavity mirror and the output mirror. The first wavelength is different from the second wavelength.

[0015] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the first wavelength is 443 mm, the second wavelength is 523 mm, and the certain frequency band is 700 nm-850 nm.

[0016] Beneficial effects of the present invention This invention obtains high-power near-infrared lasers with variable wavelengths through intracavity pumping and temperature control. The obtained near-infrared lasers have the advantages of high output power, high optical-to-optical conversion efficiency, tunable wavelength, and good beam quality, and can be widely used as laser illumination sources in the fields of laser detection and laser imaging. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0018] To better understand the technical solution of this invention, the content of this invention includes, but is not limited to, the specific embodiments described below. Similar technologies and methods should be considered within the scope of protection of this invention. To make the technical problem to be solved, the technical solution, and the advantages of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments.

[0019] It should be understood that the embodiments described in this invention are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0020] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0021] like Figure 1 As shown, a wavelength-tunable high-power near-infrared laser of the present invention includes an input mirror 1, a semiconductor laser module 2, an endoscope 3, a first laser crystal 6, a second laser crystal 4, and an output mirror 5, a temperature control module 7, and a TEC module 8 connected in sequence.

[0022] The semiconductor laser module 2 and the first laser crystal 6 are disposed between the input mirror 1 and the endoscope 3. The semiconductor laser module 2 emits a pump laser, which directly irradiates the first laser crystal 6 in a side-pumping manner. The first laser crystal 6 is pumped and stimulated to produce stimulated emission, forming intracavity fundamental frequency light under the action of the input mirror 1 and the output mirror 5. This intracavity fundamental frequency light then passes sequentially through the intracavity mirror 3 and the second laser crystal 4, and is finally output by the output mirror 5 to obtain a high-power near-infrared laser with a fixed frequency. The second laser crystal 4 is attached to a TEC module 8, which senses the temperature of the second laser crystal 4. The TEC module 8 is connected to a tuning temperature control module 7, which controls the temperature of the TEC module 8, thereby controlling the temperature of the second laser crystal 4 and achieving frequency adjustment of the near-infrared laser, ultimately obtaining a wavelength-tunable near-infrared laser.

[0023] Furthermore, the input mirror 1 is used to perform total internal reflection on the pump laser emitted by the semiconductor laser module 2, which directly irradiates the first laser crystal 6 in a side-pumped manner, and the cavity fundamental frequency light generated by the oscillation of the input mirror 1 and the output mirror 5, and the near-infrared laser generated by the internal cavity mirror 3, the output mirror 5, and the second laser crystal 4. The input mirror 1 has an optical aperture of 20 mm, a coating thickness of 523 nm, a reflectivity of ≥99.5%, a wavelength of 700-850 nm, and a transmittance of ≥99%.

[0024] Semiconductor laser module 2, as the pump source of the intracavity fundamental frequency light, is electrically excited to generate a first laser with a wavelength of 443nm. This laser pumps the first laser crystal 6. The total output power of the laser is 200W. It is cylindrical in shape with an overall size of Φ5mm×60mm, that is, a diameter of 5mm and a length of 60mm. It adopts a side-pumping method. The laser wavelength is about 443nm, which is used to match the absorption peak of pr:ylf of the laser crystal at 443nm. The optical-optical conversion efficiency is the highest when the absorption peak is perfectly matched, which is about 50%.

[0025] The endoscope 3 is used to pump the first laser crystal 6 with a second wavelength of 523nm by the semiconductor laser module 2. The pump light is completely transmitted through the cavity fundamental frequency light generated by the oscillation of the input mirror 1 and the output mirror 5. The endoscope 3 then performs full emission of this cavity fundamental frequency light.

[0026] The second laser crystal 4 serves as the gain medium for the near-infrared laser, absorbing and exciting the fundamental frequency light (pump light) within the cavity. The laser crystal material used is MgO:PPLN, and it is a cuboid with dimensions of 25mm × 6mm × 6mm. This crystal is the laser crystal that generates the Optical Parametric Oscillation (OPO), used to excite signal light and idler light based on the pump light. According to the principle of wavelength conservation in optical parametric oscillation (OPO) technology, when the pump light is 523nm, the signal light excited by the second laser crystal 4 is 700-850nm, and the idler light is 1352.74nm~2052.81nm. The signal light is the laser to be obtained in this invention. This laser then enters the output mirror 5. The pump light wavelength is 523nm, and the signal light, under temperature control, can have a frequency range of 700-850nm, while the idler light has a frequency range of 1350-2068nm.

[0027] Preferably, when the pump light is 523 nm, under appropriate temperature control, the corresponding signal light can reach 700 nm, and the idler light is 2068 nm. Therefore, the wavelength changes with temperature.

[0028] The output mirror 5 performs total internal reflection on the received signal light, allowing the near-infrared laser to pass through completely, thus obtaining the output of the entire laser. The first laser crystal 6 is used to absorb the pump light of the semiconductor laser module 2 and excite the fundamental frequency visible light laser. The laser is directed towards the endoscope 3. The first laser crystal 6 and the second laser crystal 4 have the same structural dimensions.

[0029] Temperature control module 7 performs precise temperature control on TEC module 8, thereby achieving temperature control of laser crystal 4.

[0030] The temperature control module 7 generates a power modulator with a high duty cycle of ±24V or ±48V based on the temperature measurement value obtained by the temperature sensor installed on it. For example, if the set temperature is 10℃ and the actual laser crystal temperature is 20℃, the temperature sensor will measure 20℃, and the power modulator will generate a +24V power supply with a 100% duty cycle. This corresponds to the TEC module 8 cooling, which can quickly reduce the temperature of the second laser crystal 4 that is in close contact with the TEC module 8. When the temperature drops to 10℃, the duty cycle of the +24V voltage of the power modulator is 0 and it does not work. If the crystal temperature changes again, closed-loop feedback control will be performed. The hermoelectric cooler TEC module, or TEC module 8, is temperature-controlled by the temperature control module 7, converting electrical power into cooling / heating, thereby controlling the temperature of the second laser crystal 4.

[0031] The TEC module 8 is in close contact with the second laser crystal 4, and its temperature determines the temperature of the second laser crystal 4. The frequency tuning of the output wavelength in the 700-850nm band is related to the temperature of the second laser crystal 4. The higher the temperature, the more the wavelength shifts towards the 850nm range. This is the principle of temperature and wavelength control in OPO technology.

[0032] Furthermore, the laser output is a near-infrared laser with a frequency range of approximately 700nm-850nm.

[0033] Furthermore, the near-infrared laser obtained by the laser has a high optical-to-optical conversion efficiency, which is greater than 25%. The efficiency of 443nm pumping pr:ylf to generate 523nm green light is about 50%, and the efficiency of 523nm pumping pr:ylf to generate 700-850nm light is about 50%, which may actually be higher. The optical-to-optical conversion efficiency from 443nm to 700-850nm is 50% × 50% = 25%. Therefore, the above-mentioned optical-to-optical conversion efficiency is obtained.

[0034] As an embodiment of the present invention, the present invention also discloses a laser operating mode, which is implemented using the modules described above, specifically including: After power is turned on, the semiconductor laser module 2 is electrically excited to generate a 443nm laser, which in turn excites the first laser crystal 6 (pr:ylf laser crystal) via side pumping. The first laser crystal 6, input mirror 1, and output mirror 5 work together to generate a 523nm laser, which serves as the pump light. Alternatively, the first laser crystal 6 and input mirror 1 can work together to generate the pump light, which is then directed into the second laser crystal 4 (MgO:PPLN), exciting it to generate a signal light within a specific frequency range, 700-850nm, preferably 750nm. Under the action of the cavity mirror 3 and output mirror 5, the signal light is amplified and output. At this time, the tuning temperature control module 7 sets the temperature of the second laser crystal 4, and the output signal light is adjusted nearly linearly with temperature changes. By controlling the temperature, laser output within a specified frequency range of 700-850nm is achieved.

[0035] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A wavelength-tunable high-power near-infrared laser, characterized in that, The laser comprises an input mirror, a semiconductor laser module, an endoscope, a first laser crystal, a second laser crystal, and an output mirror, connected in sequence. The semiconductor laser module and the first laser crystal are disposed between the input mirror and the endoscope. The semiconductor laser module is arranged around the first laser crystal and emits pump laser. The pump laser enters through the input mirror and is incident on the first laser crystal. The first laser crystal is pumped to generate stimulated emission, forming an intracavity oscillating laser. The intracavity oscillating laser then passes through the intracavity mirror and the second laser crystal in sequence, and is finally output by the output mirror to obtain a wavelength-tunable high-power near-infrared laser. The wavelength of the near-infrared laser can be changed with the temperature of the second laser crystal.

2. The laser according to claim 1, characterized in that, It also includes a temperature control module and a TEC module. The TEC module is attached to the second laser crystal, and the temperature control module is electrically connected to the TEC module to control the temperature of the TEC module.

3. The laser according to claim 1, characterized in that, The first laser crystal and the second laser crystal have identical structures.

4. The laser according to claim 1, characterized in that, The laser output is a near-infrared laser with a frequency range of 700nm-850nm.

5. The laser according to claim 1, characterized in that, The optical-to-optical conversion efficiency of the near-infrared laser is greater than 25%.

6. The laser according to claim 1, characterized in that, The input mirror has an optical aperture of 20mm, a coating thickness of 523nm, a reflectivity of ≥99.5%, a wavelength of 700-850nm, and a transmittance of ≥99%.

7. The laser according to claim 1, characterized in that, The semiconductor laser module is a cylinder with overall dimensions of Φ5mm × 60mm.

8. The laser according to claim 3, characterized in that, Both the first and second laser crystals are rectangular parallelepipeds with dimensions of 25mm × 6mm × 6mm.

9. A method for operating a wavelength-tunable high-power near-infrared laser, characterized in that, The method is implemented using the laser according to any one of claims 1-8, and includes the following steps: after the power is turned on, the semiconductor laser module of the laser is electrically excited to generate laser light of a first wavelength, and the first laser crystal is excited in a side-pumped manner. Then, the first laser crystal, the input mirror and the output mirror work together to generate laser light of a second wavelength as pump light. The pump light excites the second laser crystal to generate signal light within a certain frequency range. The signal light is amplified and output under the action of the cavity mirror and the output mirror. The first wavelength is different from the second wavelength.

10. The working method according to claim 9, characterized in that, The first wavelength is 443mm, the second wavelength is 523mm, and the specified frequency band is 700nm-850nm.

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