A PPLN crystal temperature-tuned laser based on an air-cooled heat dissipation laser module and its manufacturing method and application

Abstract

The present invention relates to a PPLN crystal temperature-tuned laser based on an air-cooled heat dissipation laser module, its fabrication method, and application. The laser comprises a 0-degree 1064nm high-reflectivity lens, an air-cooled heat dissipation laser module, a first 45-degree 1064nm high-reflectivity lens, a second 45-degree 1064nm high-reflectivity lens, a first output coupling mirror, a PPLN crystal, and a second output coupling mirror, all positioned sequentially along an optical path. The PPLN crystal is placed on the air-cooled heat dissipation laser module to achieve heat transfer. The present invention utilizes the waste heat generated by the air-cooled heat dissipation laser module under high-power pumping to change the temperature of the PPLN crystal, thereby achieving temperature-wavelength tuning of the PPLN crystal. The result is a highly integrated, compact, and easy-to-use tunable laser.

Description

Technical Field

[0001] The present invention relates to the technical field of mid-infrared lasers, and in particular to a PPLN crystal temperature-tuned laser based on an air-cooled heat dissipation laser module, a manufacturing method thereof, and applications thereof. Background Art

[0002] Near-infrared 1-3μm wavelength lasers are located in an important atmospheric transmission window with high atmospheric transmittance. At the same time, lasers in this band are in the human eye safe band, so they have important applications in infrared remote sensing, special night vision, spectral measurement, coherent laser radar, human eye safe ranging, biomedicine and other fields. Currently, the generation of 1-3μm wavelength lasers is mainly achieved through nonlinear crystals (PPLN, KTA, etc.) and doped rare earth elements (Ho 3+ 、Tm 3+ In order to make the laser output band wider, wavelength tuning is usually used to achieve wide-band laser output.

[0003] Periodically poled lithium niobate (PPLN) is a highly efficient wavelength-conversion nonlinear optical crystal with long life, wide transmittance, and high nonlinear coefficient. It can achieve efficient frequency conversion from the visible to the mid-infrared using methods such as frequency doubling, sum frequency generation, and optical parametric oscillation, offering broad application prospects. Doping PPLN with MgO significantly increases the optical damage threshold and photorefractive threshold, making its performance more stable and enabling widely tuned, efficient near-infrared and mid-infrared laser output. Temperature tuning is currently the most widely used method for MgO:PPLN, where the output laser wavelength is varied by varying the crystal's temperature. A typical MgO:PPLN temperature-tunable laser consists of a 1064nm pump laser, a temperature-controlled furnace (for heating the MgO:PPLN to the desired temperature), and the MgO:PPLN crystal. The temperature range required for temperature tuning currently ranges from tens to hundreds of degrees Celsius. Through simulations of theoretical formulas for temperature tuning, we have found that the polarization period parameter of the MgO:PPLN significantly influences its temperature tuning curve. When the polarization period is small, the temperature range required for temperature tuning is wide, while when the polarization period is large, the temperature range required for temperature tuning is narrow.

[0004] Water cooling is currently widely used in lasers due to its effectiveness. However, water cooling requires carrying around a bulky chiller. Furthermore, temperature-controlled furnaces are also quite large for temperature tuning. These two components make the entire laser system very bulky, significantly impacting transport and ease of use. Furthermore, operating a temperature-controlled furnace at several hundred degrees Celsius poses certain risks and inconveniences during experimental operations and in practical applications. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a PPLN crystal temperature tunable laser based on an air-cooled heat dissipation laser module;

[0006] The present invention also provides a method for manufacturing the above-mentioned PPLN temperature-tuned laser and its application;

[0007] The invention has a compact structure, a small volume, is convenient to transport, and can be applied to various complex environments.

[0008] The technical solution of the present invention is:

[0009] A laser that achieves PPLN temperature tuning based on an air-cooled heat dissipation laser module, comprising a 0-degree 1064nm high-reflectivity lens, an air-cooled heat dissipation laser module, a first 45-degree 1064nm high-reflectivity lens, a second 45-degree 1064nm high-reflectivity lens, a first output coupling mirror, a PPLN crystal, and a second output coupling mirror, which are sequentially placed along an optical path; the 0-degree 1064nm high-reflectivity lens, the air-cooled heat dissipation laser module, the first 45-degree 1064nm high-reflectivity lens, the second 45-degree 1064nm high-reflectivity lens, and the first output coupling mirror constitute a 1064nm laser resonant cavity; the PPLN crystal is fixed to the heat dissipation module of the air-cooled laser via indium foil; the first output coupling mirror, the PPLN crystal, and the second output coupling mirror constitute an optical parametric oscillator;

[0010] The air-cooled heat dissipation laser module includes a fan, a heat sink, a laser heat dissipation module, and a semiconductor refrigerator; the laser heat dissipation module includes a pump source and a heat sink; the heat sink, semiconductor refrigerator, heat sink and fan constitute a heat dissipation system; the heat generated by the pump source is accelerated by the semiconductor refrigerator to be transferred to the heat sink, and the heat is dissipated by blowing air through the fan.

[0011] Preferably, according to the present invention, the fan is fixed separately; the heat sink is fixed together with the heat sink of the laser heat dissipation module; and the semiconductor cooler is placed between the heat sink and the laser heat dissipation module.

[0012] Preferably, according to the present invention, the semiconductor cooler is a rectangular parallelepiped, and its heat conduction area is smaller than the fixed contact surface of the heat sink.

[0013] Preferably, according to the present invention, thermal conductive silicone grease is provided between the heat sink and the semiconductor cooler, and between the laser heat dissipation module and the semiconductor cooler.

[0014] Preferably, according to the present invention, the 0-degree 1064nm high reflectivity lens, the first 45-degree 1064nm high reflectivity lens, and the second 45-degree 1064nm high reflectivity lens are coated with a high reflectivity film covering the 1064nm wavelength on one side facing the 1064nm laser resonant cavity.

[0015] Preferably, according to the present invention, the side of the first output coupling mirror facing the 1064nm laser resonant cavity is coated with a partial reflectivity film covering the 1064nm wavelength, and the side facing the PPLN crystal is coated with a high reflectivity film covering the 1.5-3μm band.

[0016] Preferably, according to the present invention, the coating layer on the side of the second output coupling mirror facing the PPLN crystal is highly reflective at 1064 nm and partially reflective at 1.5-3 μm.

[0017] Preferably, according to the present invention, the first 45-degree 1064nm high reflectivity lens and the second 45-degree 1064nm high reflectivity lens are both placed at an angle of 45 degrees to the optical path.

[0018] Preferably according to the present invention, the PPLN crystal is a cuboid.

[0019] Preferably according to the present invention, the MgO doping concentration of the PPLN crystal is 5%.

[0020] According to the preferred embodiment of the present invention, the polarization period value of the PPLN crystal is selected to be greater than 31 μm.

[0021] The manufacturing method of the above-mentioned PPLN temperature-tuned laser comprises:

[0022] (1) Fixing a 0-degree 1064nm high reflectivity lens, a first 45-degree 1064nm high reflectivity lens, a second 45-degree 1064nm high reflectivity lens, a first output coupling mirror, and a second output coupling mirror on a lens holder;

[0023] (2) Install and fix the 0-degree 1064nm high reflectivity lens, the air-cooled heat dissipation laser module, the first 45-degree 1064nm high reflectivity lens, the second 45-degree 1064nm high reflectivity lens, the first output coupling mirror, and the second output coupling mirror in sequence so that the center line of all devices coincides with the optical axis;

[0024] (3) The pump source is working, and the angles of the 0-degree 1064nm high reflectivity lens, the first 45-degree 1064nm high reflectivity lens, the second 45-degree 1064nm high reflectivity lens, and the first output coupling mirror are adjusted to output 1064nm laser;

[0025] (4) Wrap the PPLN crystal with indium foil, place it on the surface of the air-cooled laser module, and press it to make the surface contact better;

[0026] (5) The 1064 nm output laser is incident on the end face of the PPLN crystal, causing a nonlinear effect. The angle of the second output coupling mirror is adjusted to output lasers of other wavelengths.

[0027] (6) Changing the operating current of the pump source causes the output wavelength of the PPLN crystal to change.

[0028] The application of the above-mentioned PPLN temperature-tuned laser includes: by changing the operating current of the 1064nm laser pump source, the waste heat generated during the operation of the pump source is converted into useful energy, thereby changing the temperature of the PPLN crystal, thereby achieving temperature-wavelength tuning of the PPLN crystal at different temperatures.

[0029] Compared with the existing technical solutions, the present invention has the following significant advantages:

[0030] 1. The 1064nm pump source used in the present invention adopts an air-cooled heat dissipation method. Compared with the laser using the traditional water-cooled heat dissipation method, it does not require a bulky water-cooling machine, and the entire structure is more compact and simplified.

[0031] 2. The present invention makes full use of the waste heat generated by the high-power air-cooling module during operation. The temperature of the metal heat sink caused by the residual heat is increased, and the heat is transferred to the PPLN crystal, thereby achieving PPLN crystal temperature tuning by changing the size of the pump current, with high energy utilization.

[0032] 3. The present invention eliminates the need for a temperature control furnace for traditional temperature tuning, and the operating temperature is tens of degrees Celsius, thus avoiding the danger of high-temperature operation when the temperature control furnace is operated at hundreds of degrees Celsius, and the entire equipment is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a detailed structural diagram of the PPLN crystal temperature-tuned laser based on the air-cooled heat dissipation module of the present invention;

[0034] Figure 2 This is a schematic structural diagram of the air-cooling heat dissipation module of the present invention;

[0035] Figure 3 Schematic diagram of the theoretical simulation curve of temperature tuning of the PPLN crystal of the present invention;

[0036] Among them, 1. 0-degree 1064nm high reflectivity lens, 2. First 45-degree 1064nm high reflectivity lens, 3. Second 45-degree 1064nm high reflectivity lens, 4. First output coupling mirror, 5. PPLN crystal, 6. Air-cooled heat dissipation laser module, 7. Second output coupling mirror, 8. Fan, 9. Heat sink, 10. Laser heat dissipation module, 11. Semiconductor refrigerator. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but is not limited thereto.

[0038] Example 1

[0039] A laser that realizes PPLN temperature tuning based on air-cooled heat dissipation laser module, such as Figure 1 As shown, the optical path includes a 0-degree 1064nm high-reflectivity lens 1, an air-cooled laser module 6, a first 45-degree 1064nm high-reflectivity lens 2, a second 45-degree 1064nm high-reflectivity lens 3, a first output coupler 4, a PPLN crystal 5, and a second output coupler 7, all arranged sequentially along the optical path. The 0-degree 1064nm high-reflectivity lens 1, the air-cooled laser module 6, the first 45-degree 1064nm high-reflectivity lens 2, the second 45-degree 1064nm high-reflectivity lens 3, and the first output coupler 4 form a 1064nm laser resonator. The PPLN crystal 5 is wrapped and secured to the air-cooled laser module 6 with indium foil. The indium foil improves thermal conductivity. The first output coupler 4, PPLN crystal 5, and the second output coupler 7 form an optical parametric oscillator.

[0040] After building each device and fixing their positions, the 1064nm laser output is achieved by fine-tuning the angles of the 0-degree 1064nm high-reflectivity lens 1, the first 45-degree 1064nm high-reflectivity lens 2, the second 45-degree 1064nm high-reflectivity lens 3, and the first output coupling mirror 4. This ensures that the 1064nm laser is output to the end face of the PPLN crystal 5. The 1064nm laser undergoes nonlinear frequency conversion after passing through the PPLN crystal 5, and outputs lasers of other required wavelengths.

[0041] like Figure 2 As shown, the air-cooled heat dissipation laser module 6 includes a fan 8, a heat sink 9, a laser heat dissipation module 10, and a semiconductor refrigerator 11; the laser heat dissipation module 10 includes a pump source and a heat sink; the semiconductor refrigerator 11, the heat sink 9 and the fan 8 constitute a heat dissipation system; the heat generated by the pump source is accelerated by the semiconductor refrigerator 11 to transfer the heat to the heat sink 9, and the heat is dissipated by blowing air through the fan 8.

[0042] The heat sink is a metal heat sink, and the material of the metal heat sink is a metal with high thermal conductivity.

[0043] When powered on, the air-cooled laser module 6, pumped by an 808nm LD bar, generates a population inversion within the gain medium within the module, generating 1064nm stimulated emission. The 0-degree 1064nm high-reflectivity lens 1, the first 45-degree 1064nm high-reflectivity lens 2, the second 45-degree 1064nm high-reflectivity lens 3, and the first output coupling mirror 4 cause the 1064nm stimulated emission to oscillate back and forth within the resonant cavity. Each time it passes through the gain medium, the stimulated emission is amplified. After multiple round-trip gain amplification, 1064nm laser light is output from the first output coupling mirror 4. The PPLN crystal 5 is a commonly used temperature-tuned nonlinear crystal, and nonlinear effects occur when high-power 1064nm pump laser light passes through it.

[0044] When the pump source power increases, the heat dissipation system cannot dissipate the heat in time, causing the heat sink temperature to rise. The PPLN crystal 5 is fixed to the heat sink through the indium foil, which conducts heat to the PPLN crystal 5, thereby changing the temperature of the PPLN crystal 5.

[0045] The present invention innovatively proposes to make full use of the waste heat of the air-cooled heat dissipation system and realize the temperature tuning of the PPLN crystal 5 through the temperature of the heat sink of the air-cooled heat dissipation laser module 6, which is suitable for integrated and portable near-infrared lasers required in extreme environments.

[0046] Example 2

[0047] The difference between the laser that implements PPLN temperature tuning based on an air-cooled heat dissipation laser module described in Example 1 is that:

[0048] The fan 8 is fixed separately; the heat sink 9 is fixed to the heat sink of the laser heat dissipation module 10 by means of mechanical fixing of screws and screw holes; the semiconductor cooler 11 is placed between the heat sink 9 and the laser heat dissipation module 10.

[0049] Semiconductor cooler 11 is a rectangular parallelepiped with a smaller heat transfer area than the fixed contact surface of heat sink 9. Based on the Peltier effect, heat is transferred from the cold end to the hot end at an accelerated rate. Semiconductor cooler 11 utilizes the thermoelectric effect of semiconductors to generate cooling. When a conductor connects two dissimilar metals and a direct current is applied, the temperature at one junction decreases while the temperature at the other increases.

[0050] Thermal conductive silicone grease is provided between the heat sink 9 and the semiconductor cooler 11, and between the laser heat dissipation module 10 and the semiconductor cooler 11. The thermal conductive silicone grease reduces the contact gap and enhances the heat conduction capability.

[0051] The heat sink 9 is made of metal with high heat dissipation efficiency.

[0052] Example 3

[0053] The difference between the laser that implements PPLN temperature tuning based on an air-cooled heat dissipation laser module described in Example 1 is that:

[0054] The 0-degree 1064nm high-reflectivity lens 1, the first 45-degree 1064nm high-reflectivity lens 2, the second 45-degree 1064nm high-reflectivity lens 3, the first output coupling mirror 4, and the second output coupling mirror 7 are all plane mirrors. The sides of the 0-degree 1064nm high-reflectivity lens 1, the first 45-degree 1064nm high-reflectivity lens 2, and the second 45-degree 1064nm high-reflectivity lens 3 facing the 1064nm laser resonator are coated with a high-reflectivity coating covering the 1064nm wavelength (reflectivity R>99.5%). The side of the first output coupling mirror 4 facing the 1064nm laser resonator is coated with a partial reflectivity coating covering the 1064nm wavelength (reflectivity is lower than the high-reflectivity coating), and the side facing the PPLN crystal is coated with a high-reflectivity coating covering the 1.5-3μm band. The coating on the side of the second output coupling mirror 7 facing the PPLN crystal is highly reflective to 1064nm and partially reflective to the 1.5-3μm band.

[0055] The first 45-degree 1064nm high reflectivity lens 2 and the second 45-degree 1064nm high reflectivity lens 3 are both placed at an angle of 45 degrees to the optical path.

[0056] The PPLN crystal 5 is a rectangular parallelepiped.

[0057] The MgO doping concentration of the PPLN crystal 5 is 5% (molar fraction) to increase the damage threshold and photorefractive threshold of the crystal.

[0058] The PPLN crystal 5 is selected to have a polarization period value of 31 μm or more.

[0059] Example 4

[0060] The method for manufacturing the PPLN temperature-tuned laser according to any one of embodiments 1-3 comprises:

[0061] (1) Fix the 0-degree 1064nm high reflectivity lens 1, the first 45-degree 1064nm high reflectivity lens 2, the second 45-degree 1064nm high reflectivity lens 3, the first output coupling mirror 4, and the second output coupling mirror 7 on the lens frame;

[0062] (2) Install and fix the 0-degree 1064nm high reflectivity lens 1, the air-cooled heat dissipation laser module 6, the first 45-degree 1064nm high reflectivity lens 2, the second 45-degree 1064nm high reflectivity lens 3, the first output coupling mirror 4, and the second output coupling mirror 7 in sequence so that the center line of all components coincides with the optical axis;

[0063] (3) The pump source is working, and the angles of the 0-degree 1064nm high reflectivity lens 1, the first 45-degree 1064nm high reflectivity lens 2, the second 45-degree 1064nm high reflectivity lens, and the first output coupling mirror 4 are adjusted to output 1064nm laser;

[0064] (4) Wrap the PPLN crystal 5 with indium foil, place it on the surface of the air-cooled laser module 6, and press it to make the surface contact better;

[0065] (5) The 1064 nm output laser is directed onto the end face of the PPLN crystal 5, causing a nonlinear effect. The angle of the second output coupling mirror 7 is adjusted to output lasers of other wavelengths.

[0066] (7) Changing the operating current of the pump source causes the output wavelength of the PPLN crystal 5 to change.

[0067] Example 5

[0068] The application of the PPLN temperature-tunable laser described in any of Examples 1-3 includes: by varying the operating current of a 1064nm laser pump source, the waste heat generated by the pump source is converted into useful energy, thereby varying the temperature of the PPLN crystal 5, thereby achieving temperature-wavelength tuning of the PPLN crystal 5 at different temperatures. The temperature of the air-cooled laser module 6 increases, transferring heat to the PPLN crystal 5, thereby causing the temperature of the PPLN crystal 5 to change.

[0069] The temperature tuning theoretical curve of the partial polarization period PPLN crystal 5 is as follows Figure 3 As shown in the figure, the temperature tuning curves corresponding to PPLN crystals 5 with different poling periods are different. As the poling period value increases, the temperature tuning effect becomes more significant. Therefore, you can choose a PPLN crystal 5 with a suitable poling period according to your needs to achieve temperature tuning in the corresponding wavelength range.

Claims

1. A laser that realizes PPLN temperature tuning based on an air-cooled heat dissipation laser module, characterized in that: The optical fiber comprises a 0-degree 1064nm high-reflectivity lens, an air-cooled heat dissipation laser module, a first 45-degree 1064nm high-reflectivity lens, a second 45-degree 1064nm high-reflectivity lens, a first output coupling mirror, a PPLN crystal, and a second output coupling mirror, which are sequentially placed along the optical path; the 0-degree 1064nm high-reflectivity lens, the air-cooled heat dissipation laser module, the first 45-degree 1064nm high-reflectivity lens, the second 45-degree 1064nm high-reflectivity lens, and the first output coupling mirror constitute a 1064nm laser resonant cavity; the PPLN crystal is fixed to the air-cooled heat dissipation laser module via indium foil; the first output coupling mirror, the PPLN crystal, and the second output coupling mirror constitute an optical parametric oscillator; The air-cooled heat dissipation laser module includes a fan, a heat sink, a laser heat dissipation module, and a semiconductor refrigerator; the laser heat dissipation module includes a pump source and a heat sink; the heat sink, semiconductor refrigerator, heat sink and fan constitute a heat dissipation system; the heat generated by the pump source is accelerated by the semiconductor refrigerator to be transferred to the heat sink, and the heat is dissipated by blowing air through the fan.

2. The laser that realizes PPLN temperature tuning based on an air-cooled heat dissipation laser module according to claim 1, characterized in that: The fan is fixed separately; the heat sink is fixed together with the heat sink of the laser heat dissipation module; and the semiconductor refrigerator is placed between the heat sink and the laser heat dissipation module.

3. The laser that realizes PPLN temperature tuning based on air-cooled heat dissipation laser module according to claim 1, characterized in that: The semiconductor refrigerator is a rectangular parallelepiped, and its heat conduction area is smaller than the fixed contact surface of the heat sink.

4. The laser that realizes PPLN temperature tuning based on an air-cooled heat dissipation laser module according to claim 2, characterized in that: Thermal conductive silicone grease is provided between the heat sink and the semiconductor refrigerator, and between the laser heat dissipation module and the semiconductor refrigerator.

5. The laser that realizes PPLN temperature tuning based on air-cooled heat dissipation laser module according to claim 1, characterized in that: The 0-degree 1064nm high-reflectivity lens, the first 45-degree 1064nm high-reflectivity lens, and the second 45-degree 1064nm high-reflectivity lens are coated with a high-reflectivity film covering the 1064nm wavelength on the side facing the 1064nm laser resonant cavity; the first output coupling mirror is coated with a partial reflectivity film covering the 1064nm wavelength on the side facing the 1064nm laser resonant cavity, and the side facing the PPLN crystal is coated with a high-reflectivity film covering the 1.5-3μm band; the film coated on the side of the second output coupling mirror facing the PPLN crystal is highly reflective to 1064nm and partially reflective to the 1.5-3μm band.

6. The laser that realizes PPLN temperature tuning based on an air-cooled heat dissipation laser module according to claim 1, characterized in that: The first 45-degree 1064nm high reflectivity lens and the second 45-degree 1064nm high reflectivity lens are both placed at an angle of 45 degrees to the optical path.

7. The laser that realizes PPLN temperature tuning based on an air-cooled heat dissipation laser module according to claim 1, characterized in that: The PPLN crystal is a rectangular parallelepiped; the MgO doping concentration of the PPLN crystal is 5%.

8. The laser that realizes PPLN temperature tuning based on an air-cooled heat dissipation laser module according to claim 1, characterized in that: The polarization period value of the PPLN crystal is selected to be greater than 31 μm.

9. The method for manufacturing a PPLN temperature-tuned laser according to any one of claims 1 to 8, characterized in that: include: (1) Fixing a 0-degree 1064nm high reflectivity lens, a first 45-degree 1064nm high reflectivity lens, a second 45-degree 1064nm high reflectivity lens, a first output coupling mirror, and a second output coupling mirror on a lens holder; (2) Install and fix the 0-degree 1064nm high reflectivity lens, the air-cooled heat dissipation laser module, the first 45-degree 1064nm high reflectivity lens, the second 45-degree 1064nm high reflectivity lens, the first output coupling mirror, and the second output coupling mirror in sequence so that the center line of all devices coincides with the optical axis; (3) The pump source is working, and the angles of the 0-degree 1064nm high reflectivity lens, the first 45-degree 1064nm high reflectivity lens, the second 45-degree 1064nm high reflectivity lens, and the first output coupling mirror are adjusted to output 1064nm laser; (4) Wrap the PPLN crystal with indium foil, place it on the surface of the air-cooled laser module, and press it to make the surface contact better; (5) The 1064nm output laser is directed onto the end face of the PPLN crystal, causing a nonlinear effect. The angle of the second output coupling mirror is adjusted to output lasers of other wavelengths. (6) Changing the operating current of the pump source causes the output wavelength of the PPLN crystal to change.

10. Application of the PPLN temperature-tuned laser according to any one of claims 1 to 8, characterized in that: include: By changing the operating current of the 1064nm laser pump source, the waste heat generated when the pump source is working is converted into useful energy, thereby changing the temperature of the PPLN crystal and achieving temperature-wavelength tuning of the PPLN crystal at different temperatures.

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