CN117175339B - Method for generating middle-far infrared laser with wide tuning range and high resolution - Google Patents
Method for generating middle-far infrared laser with wide tuning range and high resolution Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 239000013078 crystal Substances 0.000 claims abstract description 75
- 230000003287 optical effect Effects 0.000 claims description 62
- 230000005540 biological transmission Effects 0.000 claims description 38
- 239000011669 selenium Substances 0.000 claims description 20
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 19
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims description 19
- 229910052788 barium Inorganic materials 0.000 claims description 19
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 claims description 19
- 229910052733 gallium Inorganic materials 0.000 claims description 19
- 229910052711 selenium Inorganic materials 0.000 claims description 19
- 229910052732 germanium Inorganic materials 0.000 claims description 18
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 18
- 238000001914 filtration Methods 0.000 claims description 12
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 230000035945 sensitivity Effects 0.000 claims description 7
- 230000003247 decreasing effect Effects 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 6
- 230000010355 oscillation Effects 0.000 claims description 6
- 238000005086 pumping Methods 0.000 claims description 4
- 230000000630 rising effect Effects 0.000 claims description 3
- 230000033228 biological regulation Effects 0.000 description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 3
- 239000000395 magnesium oxide Substances 0.000 description 3
- QFQMUMSMVIHPKR-UHFFFAOYSA-K P(=O)([O-])([O-])[O-].[Ge+2].[Zn+2] Chemical compound P(=O)([O-])([O-])[O-].[Ge+2].[Zn+2] QFQMUMSMVIHPKR-UHFFFAOYSA-K 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010905 molecular spectroscopy Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
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Abstract
The invention provides a method for generating middle-far infrared laser with wide tuning range and high resolution, and belongs to the technical field of infrared laser. The method comprises the steps of simultaneously controlling the angle and the temperature of BGSe crystals, firstly changing the temperature of the crystals under the condition of normal incidence, and obtaining high-resolution laser output of a certain wave band; then changing the angle of the crystal to a certain specific value and changing the temperature of the crystal, so as to obtain the high-resolution laser output of another wave band; the temperature of the crystal is sequentially changed under different angles, so that high-resolution laser output in a wider wave band range can be obtained.
Description
Technical Field
The invention belongs to the technical field of infrared laser, and particularly relates to a method for generating middle-far infrared laser with wide tuning range and high resolution.
Background
Currently, mid-far infrared lasers have wide and important applications in the fields of photoelectric countermeasure, environmental monitoring, medicine, molecular spectroscopy, satellites, and the like. The Optical Parametric Oscillator (OPO) can convert mature 1 mu m laser into middle-far infrared laser, and has the advantages of full solidification, miniaturization, adjustable output wavelength broadband, simple structure and the like. The wider the wavelength tuning range, the greater the selectivity of the light source and the more compact the system. The higher the wavelength resolution, the more aligned to the target band, and the higher the sensitivity and accuracy of the detection.
While in general, wide band tuning and high resolution are a pair of contradictions. When the tuning range is wide, the unit step size is generally large, and therefore the wavelength resolution is low; when the wavelength resolution is high, the unit step size is small, and thus the tuning range is generally narrow.
Disclosure of Invention
Based on the technical problems, the invention provides a method for generating middle-far infrared laser with wide tuning range and high resolution. The method comprises the following steps:
The method utilizes a laser generating device to generate middle-far infrared laser with wide tuning range and high resolution; wherein:
The laser generating device comprises the following components: the device comprises a laser, a first aperture diaphragm, a telescope system, a second aperture diaphragm, an optical parametric oscillator, an optical filter, a germanium sheet and an energy meter which are sequentially arranged along an optical transmission axis, wherein the optical transmission axis is positioned at the center of each component;
An input mirror, a temperature control furnace and an output mirror are sequentially arranged in the optical parametric oscillator along the optical transmission axis, a rotatable platform is arranged in the temperature control furnace, and nonlinear crystal selenium gallium barium is positioned on the rotatable platform;
The pulse laser output by the laser pump is used as pump light, and the pump light passes through the first aperture diaphragm, the telescope system and the second aperture diaphragm in sequence and then reaches the optical parametric oscillator;
In the optical parametric oscillator, the pump light enters the temperature control furnace from a gap at one side of the temperature control furnace after passing through the input mirror, and is decomposed into signal light and idler frequency light after passing through the nonlinear crystal selenium gallium barium, the signal light is reflected by the output mirror, the idler frequency light is captured after passing through the output mirror, the optical filter and the germanium sheet, and the energy meter is used for detecting the idler frequency light;
the idler light is middle-far infrared laser, and tuning the idler light comprises:
Taking the target wavelength of the mid-far infrared laser as a tuning target for tuning the idler frequency light;
configuring a cutting angle of the pumping light passing through the nonlinear crystal selenium gallium barium, wherein the cutting angle is Θ represents the angle between the cutting direction and the Z-axis in the three-dimensional coordinate system,/>Representing the angle between the projection of the cutting direction on the X-O-Y plane and the X-O-Z plane in the three-dimensional coordinate system, wherein the change rate of the wavelength of the idler light along with theta is much higher than the change rate along with/>Configuring the cut angle includes only tuning the cut angle θ;
When the cutting angle θ is gradually increased within (40 °,70 °), the wavelength of the idler light is gradually decreased within (18 μm,2 μm), and as the cutting angle θ is increased, the rate of decrease of the wavelength of the idler light is gradually decreased;
meanwhile, when the temperature in the temperature control furnace is gradually increased in the temperature (20 ℃ and 200 ℃), the wavelength of the idler light is gradually increased, and when the cutting angle theta is reduced by 1 DEG, the rising rate of the wavelength of the idler light is gradually increased under the same temperature increasing condition;
And the sensitivity of the wavelength of the idler frequency light to the cutting angle theta is higher than the sensitivity to the temperature in the temperature control furnace, and the wavelength of the idler frequency light is equal to the target wavelength of the mid-far infrared laser in a mode of firstly adjusting the angle of the cutting angle theta and then adjusting the temperature in the temperature control furnace.
The laser is a Nd-YAG laser, the pulse width range of the pump light output by the laser is (1 ns,100 ns), and the wavelength is 1.06 mu m.
The first aperture diaphragm is used for filtering stray light in the pump light and dynamically adjusting the spot radius of the pump light, so that the pump light passing through the first aperture diaphragm has a first spot radius R1.
The telescope system comprises a convex lens and a concave lens, and is used for further adjusting the spot radius of the pump light passing through the first aperture diaphragm, so that the pump light passing through the telescope system has a second spot radius R2.
The second aperture diaphragm is used for adjusting the transmission direction of the pump light, so that the transmission direction of the pump light is perpendicular to the vertical direction of the optical parametric oscillator, and further adjusting the spot radius of the pump light passing through the telescope system, so that the pump light passing through the second aperture diaphragm has a third spot radius R3, and R1> R2> R3.
The pump light passing through the telescope system has higher light energy density than the pump light passing through the first aperture diaphragm, and the light energy loss rate is lower than a loss threshold value, wherein the light energy loss rate l=1-E1/E2, E1 is the light energy of the pump light passing through the telescope system, and E2 is the light energy of the pump light passing through the first aperture diaphragm.
And the nonlinear crystal selenium gallium barium transmits the pump light, the signal light and the idler light.
The signal light is reflected by the input mirror and the output mirror, and is transmitted by the nonlinear crystal selenium gallium barium in the reflecting process, so that the signal light forms an oscillation effect in the optical parametric oscillator.
When the signal light is reflected by the input mirror each time, the signal light reflected by the input mirror is overlapped with the pump light which arrives subsequently, and the signal light and the idler frequency light with higher energy are decomposed after passing through the nonlinear crystal selenium gallium barium, so that an oscillation overlapping effect is formed, and the output mirror transmits the idler frequency light with the conversion efficiency higher than the conversion threshold value.
After passing through the output mirror, the output of the optical parametric oscillator comprises: the idler light, the pump light which is not completely decomposed, and the signal light which is not completely reflected.
The filter and the germanium sheet are both highly reflective to the pump light and the signal light, highly transmissive to the idler light, and the pump light which is not completely decomposed and the signal light which is not completely reflected are further filtered by the filter and the germanium sheet, and only the idler light reaches the energy meter.
The optical filter is positioned on the optical transmission axis and is not perpendicular to the optical transmission axis, and the included angle range between the optical filter and the optical transmission axis is [3 degrees, 10 degrees ], so that pump light reflected by the optical filter does not damage other components on the optical transmission axis.
The germanium sheet is used for filtering the pump light which is not completely decomposed and the signal light which is not completely reflected and has the wavelength of less than 1.7 mu m.
When the cutting angle θ=62°, the temperature in the temperature-controlled furnace is gradually increased in the (20 ℃,200 ℃) range, and the wavelength of the captured mid-far infrared laser is 2.3-5 μm.
When the cutting angle θ=59.8°, the temperature in the temperature-controlled furnace was gradually increased in the (20 ℃,200 ℃) range, and the wavelength of the captured mid-far infrared laser was 3-3.4 μm.
When the cutting angle θ=57.7°, the temperature in the temperature-controlled furnace was gradually increased in the (20 ℃,200 ℃) range, and the wavelength of the captured mid-far infrared laser was 3.4-3.8 μm.
According to the technical scheme provided by the invention, the angle and the temperature of BGSe crystals are controlled simultaneously, and the temperature of the crystals is changed under the condition of normal incidence to obtain high-resolution laser output with a certain wave band; then changing the angle of the crystal to a certain specific value and changing the temperature of the crystal, so as to obtain the high-resolution laser output of another wave band; the temperature of the crystal is sequentially changed under different angles, and the combination can obtain high-resolution laser output in a wider wave band range.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings which are required in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are some embodiments of the invention and that other drawings may be obtained from these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of components of a laser generating apparatus according to an embodiment of the present invention;
Fig. 2 is a graph showing phase matching curves of BGSe OPO at different temperatures and different θ angles under the conditions of class I phase matching, Φ=0°;
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
BGSe: baGa 4Se7, selenium gallium barium, a medium and far infrared nonlinear crystal.
OPO: optical parametric oscillator, an optical parametric oscillator, which is composed of nonlinear crystal and optical resonant cavity, can realize the large-scale continuous tuning of output wavelength.
ZGP: znGeP 2, zinc germanium phosphate, a medium and far infrared nonlinear crystal.
MgO, PPLN, magnesium oxide doped periodically polarized lithium niobate, a medium infrared nonlinear crystal.
Angle tuning is a technique to achieve broadband wavelength tuning. For example, using 2149nm laser pumped ZGP crystals, when the ZGP crystal angle was tuned from 51.2 ° to 50.3 °, a continuously tunable wavelength far infrared laser output in the range 7.82-9.08 μm was obtained (tuning range 1260 nm). Most of the far infrared nonlinear crystals have a certain angle tuning capability. However, the resolution of the laser wavelength output by the tuning mode is not high, and it is difficult to completely align the target wavelength.
Temperature tuning is another technique to achieve wavelength tuning. For example, using 1064nm laser pumped MgO as PPLN crystals (grating period 26-31 μm, 6 pieces of crystals), when the temperature of the crystals is raised from 25℃to 200℃a continuously tunable mid-infrared laser output in the range of 2.2-4.8 μm is obtained, with an average tuning range per crystal of 433nm. However, the tuning range of the output wavelength of a monolithic crystal is insufficient, and pumping requires switching back and forth among several crystals to achieve a laser wavelength output over a larger range, increasing the complexity of the system.
The wavelength tuning range of angle tuning is larger than that of temperature tuning, but there is a disadvantage in that when the crystal angle is changed, the pump light does not perform nonlinear crystal in normal incidence, so the conversion efficiency is lowered, and particularly when the angle change is large, the conversion efficiency of the output idler light is low. In the temperature tuning, the position of the pump light relative to the crystal is not moved, so that the normal incidence state can be always kept, and the conversion efficiency of idler frequency light is higher.
KTA crystal has a certain angle tuning capability, but the temperature tuning capability is too small; PPLN crystals have a certain temperature tuning capability, but are limited by the growth size of the crystal, and are difficult to angle tune.
From the practical demand and application point of view, the invention carries out theoretical and experimental research on the mid-far infrared nonlinear crystal BGSe. The nonlinear crystal BGSe is utilized to realize wide-range and high-resolution wavelength tuning at the same time with wide-band angle tuning capability and temperature tuning capability.
The invention provides the method for simultaneously controlling the angle and the temperature of BGSe crystals, firstly changing the temperature of the crystals under the condition of normal incidence to obtain high-resolution laser output with a certain wave band; then changing the angle of the crystal to a certain specific value and changing the temperature of the crystal, so as to obtain the high-resolution laser output of another wave band; the temperature of the crystal is sequentially changed under different angles, and the combination can obtain high-resolution laser output in a wider wave band range.
The invention provides a method for generating middle-far infrared laser with wide tuning range and high resolution. The method utilizes a laser generating device to generate middle-far infrared laser with wide tuning range and high resolution; wherein:
the laser generating device comprises the following components (shown in fig. 1): the device comprises a laser, a first aperture diaphragm, a telescope system, a second aperture diaphragm, an optical parametric oscillator, an optical filter, a germanium sheet and an energy meter which are sequentially arranged along an optical transmission axis, wherein the optical transmission axis is positioned at the center of each component;
An input mirror, a temperature control furnace and an output mirror are sequentially arranged in the optical parametric oscillator along the optical transmission axis, a rotatable platform is arranged in the temperature control furnace, and nonlinear crystal selenium gallium barium is positioned on the rotatable platform;
The pulse laser output by the laser pump is used as pump light, and the pump light passes through the first aperture diaphragm, the telescope system and the second aperture diaphragm in sequence and then reaches the optical parametric oscillator;
In the optical parametric oscillator, the pump light enters the temperature control furnace from a gap at one side of the temperature control furnace after passing through the input mirror, and is decomposed into signal light and idler frequency light after passing through the nonlinear crystal selenium gallium barium, the signal light is reflected by the output mirror, the idler frequency light is captured after passing through the output mirror, the optical filter and the germanium sheet, and the energy meter is used for detecting the idler frequency light;
The idler is a mid-far infrared laser, and tuning the idler includes (as shown in fig. 2):
Taking the target wavelength of the mid-far infrared laser as a tuning target for tuning the idler frequency light;
configuring a cutting angle of the pumping light passing through the nonlinear crystal selenium gallium barium, wherein the cutting angle is Θ represents the angle between the cutting direction and the Z-axis in the three-dimensional coordinate system,/>Representing the angle between the projection of the cutting direction on the X-O-Y plane and the X-O-Z plane in the three-dimensional coordinate system, wherein the change rate of the wavelength of the idler light along with theta is much higher than the change rate along with/>Configuring the cut angle includes only tuning the cut angle θ;
When the cutting angle θ is gradually increased within (40 °,70 °), the wavelength of the idler light is gradually decreased within (18 μm,2 μm), and as the cutting angle θ is increased, the rate of decrease of the wavelength of the idler light is gradually decreased;
meanwhile, when the temperature in the temperature control furnace is gradually increased in the temperature (20 ℃ and 200 ℃), the wavelength of the idler light is gradually increased, and when the cutting angle theta is reduced by 1 DEG, the rising rate of the wavelength of the idler light is gradually increased under the same temperature increasing condition;
And the sensitivity of the wavelength of the idler frequency light to the cutting angle theta is higher than the sensitivity to the temperature in the temperature control furnace, and the wavelength of the idler frequency light is equal to the target wavelength of the mid-far infrared laser in a mode of firstly adjusting the angle of the cutting angle theta and then adjusting the temperature in the temperature control furnace.
The laser is a Nd-YAG laser, the pulse width range of the pump light output by the laser is (1 ns,100 ns), and the wavelength is 1.06 mu m.
The first aperture diaphragm is used for filtering stray light in the pump light and dynamically adjusting the spot radius of the pump light, so that the pump light passing through the first aperture diaphragm has a first spot radius R1.
The telescope system comprises a convex lens and a concave lens, and is used for further adjusting the spot radius of the pump light passing through the first aperture diaphragm, so that the pump light passing through the telescope system has a second spot radius R2.
The second aperture diaphragm is used for adjusting the transmission direction of the pump light, so that the transmission direction of the pump light is perpendicular to the vertical direction of the optical parametric oscillator, and further adjusting the spot radius of the pump light passing through the telescope system, so that the pump light passing through the second aperture diaphragm has a third spot radius R3, and R1> R2> R3.
The pump light passing through the telescope system has higher light energy density than the pump light passing through the first aperture diaphragm, and the light energy loss rate is lower than a loss threshold value, wherein the light energy loss rate l=1-E1/E2, E1 is the light energy of the pump light passing through the telescope system, and E2 is the light energy of the pump light passing through the first aperture diaphragm.
And the nonlinear crystal selenium gallium barium transmits the pump light, the signal light and the idler light.
The signal light is reflected by the input mirror and the output mirror, and is transmitted by the nonlinear crystal selenium gallium barium in the reflecting process, so that the signal light forms an oscillation effect in the optical parametric oscillator.
When the signal light is reflected by the input mirror each time, the signal light reflected by the input mirror is overlapped with the pump light which arrives subsequently, and the signal light and the idler frequency light with higher energy are decomposed after passing through the nonlinear crystal selenium gallium barium, so that an oscillation overlapping effect is formed, and the output mirror transmits the idler frequency light with the conversion efficiency higher than the conversion threshold value.
After passing through the output mirror, the output of the optical parametric oscillator comprises: the idler light, the pump light which is not completely decomposed, and the signal light which is not completely reflected.
The filter and the germanium sheet are both highly reflective to the pump light and the signal light, highly transmissive to the idler light, and the pump light which is not completely decomposed and the signal light which is not completely reflected are further filtered by the filter and the germanium sheet, and only the idler light reaches the energy meter.
The optical filter is positioned on the optical transmission axis and is not perpendicular to the optical transmission axis, and the included angle range between the optical filter and the optical transmission axis is [3 degrees, 10 degrees ], so that pump light reflected by the optical filter does not damage other components on the optical transmission axis.
The germanium sheet is used for filtering the pump light which is not completely decomposed and the signal light which is not completely reflected and has the wavelength of less than 1.7 mu m.
When the cutting angle θ=62°, the temperature in the temperature-controlled furnace is gradually increased in the (20 ℃,200 ℃) range, and the wavelength of the captured mid-far infrared laser is 2.3-5 μm.
When the cutting angle θ=59.8°, the temperature in the temperature-controlled furnace was gradually increased in the (20 ℃,200 ℃) range, and the wavelength of the captured mid-far infrared laser was 3-3.4 μm.
When the cutting angle θ=57.7°, the temperature in the temperature-controlled furnace was gradually increased in the (20 ℃,200 ℃) range, and the wavelength of the captured mid-far infrared laser was 3.4-3.8 μm.
In some embodiments, nd: YAG outputs 1.06 mu m pulse laser with pulse width of several nanoseconds to several tens nanoseconds, and D1 is a small aperture diaphragm; t is a telescope system for compressing the spot diameter of the pump light; d2 is a small aperture stop; the M1 mirror is high in transmission of pump light (1064 nm) and high in reflection of signal light; m2 is an OPO output mirror, and has high transmission to pump light, high reflection to signal light and high transmission to idler frequency light.
In some embodiments BGSe is placed in a temperature controlled oven that changes the temperature of the crystal; the temperature control furnace is arranged on a rotatable platform, and the angle of the crystal is changed by the rotatable platform. The angle of BGSe crystal is determined by two angles of theta and phi, theta represents the included angle between the cutting direction and the Z axis in the three-dimensional coordinate system, phi represents the included angle between the projection of the cutting direction on the X-O-Y plane and the X-O-Z plane in the three-dimensional coordinate system. Wherein the conversion rate of the output wavelength with theta is much higher than phi. Therefore, the fixed phi angle is selected here, and the purpose of changing the output laser wavelength is achieved by changing the theta angle.
In some embodiments, F is a filter for filtering out the remaining pump light and the signal light output by the OPO cavity mirror, and is highly reflective to the pump light and the signal light and highly transparent to the idler light. G is germanium sheet for filtering residual pump light and signal light below 1.7 μm.
As shown in FIG. 2, the relationship between the output wavelength and the angle θ of BGSe OPO at 20 ℃, 110 ℃, 200 ℃ can be seen. To obtain a wide tuning range high resolution laser output, several specific angles θ of the crystal may be fixed and then temperature tuned. Wherein the output wavelength of the second fixed angle at the lowest temperature should be equal to or slightly less than the output wavelength of the first fixed angle at the highest temperature so that the entire tuning process can cover the entire target band.
Taking output of 2.3-5 μm laser as an example, the crystal angle θ is first adjusted to 62 °, and the temperature is adjusted from 20 ℃ to 200 ℃, so that 2.5-3 μm laser output can be obtained.
Then, the angle θ was adjusted to 59.8 °, and the temperature was adjusted from 20 ℃ to 200 ℃, whereby a laser output of 3 to 3.4 μm could be obtained.
Wherein the output wavelength of the crystal at the angle θ=62°, at the temperature of 200 ℃ is 3 μm, and the output wavelength of the crystal at the angle θ=59.8°, at the temperature of 20 ℃ is also 3 μm.
And then the angle theta is adjusted to 57.7 degrees, and the temperature is adjusted to 200 ℃ from 20 ℃ so as to obtain the laser output of 3.4-3.8 mu m.
By sequentially changing the theta angle and the temperature of the crystal, the laser output in a wide range of 2.5-5 mu m can be obtained, and the average wavelength resolution is 3.5 nm/DEG C.
Specific example 1
Nd: YAG outputs 1.06 mu m pulse laser with pulse width of several nanoseconds to several tens nanoseconds, and D1 is a small aperture diaphragm; t is a telescope system for compressing the spot diameter of the pump light; d2 is a small aperture diaphragm, the M1 mirror is high in transmission of pump light (1064 nm) and high in reflection of signal light (1.35-1.65 μm); m2 is an OPO output mirror, and has high transmission to pump light (1064 nm), high reflection to signal light (1.35-1.65 μm) and high transmission to idler light (3-5 μm). BGSe is arranged in a temperature control furnace, and the temperature of the crystal is changed by the temperature control furnace; the temperature control furnace is arranged on a rotatable platform, and the theta angle of the crystal is changed by the rotatable platform. F is a filter for filtering residual pump light and signal light output by the OPO cavity mirror, and F has high reflection to pump light (1064 nm) and signal light (1.35-1.65 μm) and high transmission to idler frequency light (3-5 μm). G is germanium sheet for filtering residual pump light and signal light below 1.7 μm.
The angle theta of BGSe crystals at normal incidence is selected to be 55.6 degrees, the temperature is tuned within the range of 25-200 ℃, the angle theta of BGSe crystals is set to be 5 gears, the angles theta are 59.7 degrees, 57.6 degrees, 55.6 degrees, 53.8 degrees and 52.0 degrees respectively, and the output wavelength changes with the temperature under different angles are shown in table 1.
Table 1: BGSe crystal angle (phi=0°, class I) when outputting 3-5 μm laser
Under normal incidence conditions (θ=55.6°), the tuning range of the output wavelength is 3796-4246nm, and the wavelength resolution is 2.57nm/°c. The tuning range of the output wavelength was 4207-4698nm and the wavelength resolution was 2.81nm/°c at θ=53.8°. By combining the angles of 5 gears, BGSe OPO can obtain the output of the middle-far infrared laser with the wavelength of 3-5 mu m, and the average wavelength resolution is 2.59 nm/DEG C.
The temperature regulation resolution of the commercial temperature control furnace can reach 0.1 ℃ and the stability is better, so that the mid-infrared laser output with the average resolution of 0.259nm and the tuning range of 3-5 mu m can be obtained in a simple system.
Specific example 2
Nd: YAG outputs 1.06 mu m pulse laser with pulse width of several nanoseconds to several tens nanoseconds, and D1 is a small aperture diaphragm; t is a telescope system for compressing the spot diameter of the pump light; d2 is a small aperture stop; the M1 mirror is high in transmission of pump light (1064 nm) and high in reflection of signal light (1.14-1.35 mu M); m2 is an OPO output mirror, and has high transmission to pump light (1064 nm), high reflection to signal light (1.14-1.35 μm) and high transmission to idler light (5-15 μm). BGSe is arranged in a temperature control furnace, and the temperature of the crystal is changed by the temperature control furnace; the temperature control furnace is arranged on a rotatable platform, and the angle of the crystal is changed by the rotatable platform. F is a filter for filtering residual pump light and signal light output by the OPO cavity mirror, and F has high reflection to pump light (1064 nm) and signal light (1.14-1.35 μm) and high transmission to idler frequency light (5-15 μm). G is germanium sheet for filtering residual pump light and signal light below 1.7 μm.
The angle theta of BGSe crystals is selected to be 46.1 degrees at normal incidence, the temperature is tuned within the range of 25-200 ℃, the angle theta of BGSe crystals is set to be 9 gears, 50.9 degrees, 49.1 degrees, 48.1 degrees, 47.1 degrees, 46.1 degrees, 44.5 degrees, 43.3 degrees, 42.4 degrees and 41.1 degrees respectively, and the change of output wavelength with temperature under different angles is shown in table 2.
Table 2: BGSe crystal angle (phi=0°, class I) when outputting 5-15 μm laser
Under normal incidence conditions (θ=46.1°), the tuning range of the output wavelength is 7000-8044nm, and the wavelength resolution is 5.96nm/°c. Under the condition of θ=44.5°, the tuning range of the output wavelength is 8000-9361nm, and the wavelength resolution is 7.78nm/°c. By combining the angles of 9 gears, BGSe OPO-15 mu m of middle-far infrared laser output can be obtained, and the average wavelength resolution is 6.35 nm/DEG C.
The temperature regulation resolution of the commercial temperature control furnace can reach 0.1 ℃ and the stability is better, so the scheme can obtain the far infrared laser output with the average resolution of 0.635nm and the tuning range of 5-15 mu m in a simple system.
Specific example 3
The band range of the output wavelength may be varied in the range of 2.3-17 μm, for example, 4-6 μm or 8-14 μm, etc., and a wide tuning range high resolution laser output may be obtained by a similar method.
The angle theta of BGSe crystals is selected to be 51.2 degrees at normal incidence, the temperature is tuned within the range of 25-200 ℃, the angle theta of BGSe crystals is set to be 4 gears, 54.7 degrees, 53.0 degrees, 51.2 degrees and 49.7 degrees are respectively set, and the change of output wavelength with temperature under different angles is shown in table 3.
Table 3: BGSe crystal angle (phi=0°, class I) when outputting 4-6 μm laser
Under normal incidence condition (51.2 degrees), the tuning range of the output wavelength is 4900-5492nm, and the wavelength resolution is 3.38 nm/DEG C. The tuning range of the output wavelength is 5400-6057nm under the condition of θ=49.7 DEG, and the wavelength resolution is 3.75 nm/DEG C. By combining the angles of 4 gears, BGSe OPO can obtain the middle-far infrared laser output of 4-6 mu m, and the average wavelength resolution is 2.94 nm/DEG C.
The temperature regulation resolution of the commercial temperature control furnace can reach 0.1 ℃ and the stability is better, so the scheme can obtain the far infrared laser output with the average resolution of 0.294nm and the tuning range of 4-6 mu m in a simple system.
Therefore, the method for generating the middle-far infrared laser with wide tuning range and high resolution can realize tuning of a large wavelength range and high wavelength resolution in a certain device, and the system can simultaneously meet the application requirements of different wave band wavelengths and can efficiently aim at target wavelengths. Thereby greatly reducing the complexity of the system, and having wide application prospect in spacecrafts such as satellites and the like.
Note that the technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be regarded as the scope of the description. The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (5)
1. A method for generating middle-far infrared laser with wide tuning range and high resolution, which is characterized in that a laser generating device is utilized to generate the middle-far infrared laser with wide tuning range and high resolution; wherein:
The laser generating device comprises the following components: the device comprises a laser, a first aperture diaphragm, a telescope system, a second aperture diaphragm, an optical parametric oscillator, an optical filter, a germanium sheet and an energy meter which are sequentially arranged along an optical transmission axis, wherein the optical transmission axis is positioned at the center of each component;
An input mirror, a temperature control furnace and an output mirror are sequentially arranged in the optical parametric oscillator along the optical transmission axis, a rotatable platform is arranged in the temperature control furnace, and nonlinear crystal selenium gallium barium is positioned on the rotatable platform;
The pulse laser output by the laser pump is used as pump light, and the pump light passes through the first aperture diaphragm, the telescope system and the second aperture diaphragm in sequence and then reaches the optical parametric oscillator;
In the optical parametric oscillator, the pump light enters the temperature control furnace from a gap at one side of the temperature control furnace after passing through the input mirror, and is decomposed into signal light and idler frequency light after passing through the nonlinear crystal selenium gallium barium, the signal light is reflected by the output mirror, the idler frequency light is captured after passing through the output mirror, the optical filter and the germanium sheet, and the energy meter is used for detecting the idler frequency light;
the idler light is middle-far infrared laser, and tuning the idler light comprises:
Taking the target wavelength of the mid-far infrared laser as a tuning target for tuning the idler frequency light;
configuring a cutting angle of the pumping light passing through the nonlinear crystal selenium gallium barium, wherein the cutting angle is Θ represents the angle between the cutting direction and the Z-axis in the three-dimensional coordinate system,/>Representing the angle between the projection of the cutting direction on the X-O-Y plane and the X-O-Z plane in the three-dimensional coordinate system, wherein the change rate of the wavelength of the idler light along with theta is much higher than the change rate along with/>Configuring the cut angle includes only tuning the cut angle θ;
When the cutting angle θ is gradually increased within (40 °,70 °), the wavelength of the idler light is gradually decreased within (18 μm,2 μm), and as the cutting angle θ is increased, the rate of decrease of the wavelength of the idler light is gradually decreased;
meanwhile, when the temperature in the temperature control furnace is gradually increased in the temperature (20 ℃ and 200 ℃), the wavelength of the idler light is gradually increased, and when the cutting angle theta is reduced by 1 DEG, the rising rate of the wavelength of the idler light is gradually increased under the same temperature increasing condition;
And the sensitivity of the wavelength of the idler frequency light to the cutting angle theta is higher than the sensitivity to the temperature in the temperature control furnace, and the wavelength of the idler frequency light is equal to the target wavelength of the mid-far infrared laser in a mode of firstly adjusting the angle of the cutting angle theta and then adjusting the temperature in the temperature control furnace.
2. The method for generating the middle-far infrared laser with wide tuning range and high resolution according to claim 1, wherein the method comprises the following steps:
YAG laser, the pulse width range of the pump light outputted by the YAG laser is (1 ns,100 ns), and the wavelength is 1.06 mu m;
the first aperture diaphragm is used for filtering stray light in the pump light and dynamically adjusting the spot radius of the pump light, so that the pump light passing through the first aperture diaphragm has a first spot radius R1;
The telescope system comprises a convex lens and a concave lens, and is used for further adjusting the spot radius of the pump light passing through the first aperture diaphragm, so that the pump light passing through the telescope system has a second spot radius R2;
the second aperture diaphragm is used for adjusting the transmission direction of the pump light, so that the transmission direction of the pump light is perpendicular to the vertical direction of the optical parametric oscillator, and further adjusting the spot radius of the pump light passing through the telescope system, so that the pump light passing through the second aperture diaphragm has a third spot radius R3, and R1> R2> R3;
the pump light passing through the telescope system has higher light energy density than the pump light passing through the first aperture diaphragm, and the light energy loss rate is lower than a loss threshold value, wherein the light energy loss rate l=1-E1/E2, E1 is the light energy of the pump light passing through the telescope system, and E2 is the light energy of the pump light passing through the first aperture diaphragm.
3. The method for generating the middle-far infrared laser with wide tuning range and high resolution according to claim 1, wherein the method comprises the following steps:
Inside the optical parametric oscillator, the input mirror and the output mirror both reflect the signal light and transmit the idler light and the pump light, and the nonlinear crystal selenium gallium barium transmits the pump light, the signal light and the idler light;
The signal light is reflected by the input mirror and the output mirror, and is transmitted by the nonlinear crystal selenium gallium barium in the reflecting process, so that the signal light forms an oscillation effect in the optical parametric oscillator;
when the signal light is reflected by the input mirror each time, the signal light reflected by the input mirror is overlapped with the pump light which arrives subsequently, and the signal light and the idler frequency light with higher energy are decomposed after passing through the nonlinear crystal selenium gallium barium, so that an oscillation overlapping effect is formed, and the output mirror transmits the idler frequency light with the conversion efficiency higher than the conversion threshold value.
4. A method for generating a wide tuning range high resolution mid-far infrared laser beam according to claim 3, wherein:
after passing through the output mirror, the output of the optical parametric oscillator comprises: the idler light, the pump light which is not completely decomposed, and the signal light which is not completely reflected;
the filter and the germanium sheet are both highly reflective to the pump light and the signal light, highly transmissive to the idler light, and the pump light which is not completely decomposed and the signal light which is not completely reflected are further filtered by the filter and the germanium sheet, and only the idler light reaches the energy meter;
The optical filter is positioned on the optical transmission axis and is not perpendicular to the optical transmission axis, and the included angle range between the optical filter and the optical transmission axis is [3 degrees, 10 degrees ], so that pump light reflected by the optical filter does not damage other components on the optical transmission axis;
The germanium sheet is used for filtering the pump light which is not completely decomposed and the signal light which is not completely reflected and has the wavelength of less than 1.7 mu m.
5. The method for generating the middle-far infrared laser with wide tuning range and high resolution according to claim 1, wherein the method comprises the following steps:
When the cutting angle theta=62°, the temperature in the temperature control furnace gradually increases in the range of (20 ℃ and 200 ℃), and the wavelength of the captured mid-far infrared laser is 2.3-5 mu m;
When the cutting angle theta=59.8°, the temperature in the temperature control furnace gradually increases in the range of (20 ℃ and 200 ℃), and the wavelength of the captured mid-far infrared laser is 3-3.4 mu m;
when the cutting angle θ=57.7°, the temperature in the temperature-controlled furnace was gradually increased in the (20 ℃,200 ℃) range, and the wavelength of the captured mid-far infrared laser was 3.4-3.8 μm.
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