CN117406529A - Nonlinear frequency conversion crystal - Google Patents

Nonlinear frequency conversion crystal Download PDF

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Publication number
CN117406529A
CN117406529A CN202311124804.8A CN202311124804A CN117406529A CN 117406529 A CN117406529 A CN 117406529A CN 202311124804 A CN202311124804 A CN 202311124804A CN 117406529 A CN117406529 A CN 117406529A
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crystal
frequency
frequency conversion
light beam
fundamental
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Inventor
卞奇
薄勇
彭钦军
左军卫
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Qilu Zhongke Institute Of Optical Physics And Engineering Technology
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Qilu Zhongke Institute Of Optical Physics And Engineering Technology
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Priority to CN202311124804.8A priority Critical patent/CN117406529A/en
Publication of CN117406529A publication Critical patent/CN117406529A/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/355—Non-linear optics characterised by the materials used
    • G02F1/3551—Crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • H01S3/109—Frequency multiplication, e.g. harmonic generation

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Optics & Photonics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

The invention relates to the technical field of laser, in particular to a nonlinear frequency conversion crystal, which comprises an incidence inclined plane, an emergent inclined plane and a side emergent window; the phase matching direction of the crystal is parallel to the central axis of the crystal, the incident inclined plane is positioned at the first end of the crystal, the emergent inclined plane is positioned at the second end of the crystal, and the side emergent window is close to the second end of the crystal; the included angle between the incidence inclined plane and the central axis of the crystal is the Brewster angle of the fundamental frequency light, so that the incidence crystal without loss of the fundamental frequency light propagates along the central axis direction and generates nonlinear frequency conversion to generate variable frequency light; the included angle between the emergent inclined plane and the central axis of the crystal is the Brewster angle of the variable frequency light, so that the variable frequency light is emitted out of the crystal without loss; wherein, the incident fundamental frequency light, the crystal center axis and the emergent variable frequency light are not in the same plane. According to the invention, the laser power loss is reduced by cutting the front end face and the rear end face by a specific angle, no film coating is needed, the damage resistance of the crystal end face can be improved, and the higher-power variable-frequency laser output can be obtained.

Description

Nonlinear frequency conversion crystal
Technical Field
The invention relates to the technical field of lasers, in particular to a nonlinear frequency conversion crystal.
Background
The laser wavelength required in many practical applications today cannot be directly generated by the lasing medium of the stimulated radiation and must be obtained by laser frequency conversion techniques. The output wavelength of the laser based on the nonlinear frequency conversion technology is already covered from deep ultraviolet to middle-far infrared, and due to the absorption, transmission, response and other properties of certain substances to specific wavelengths, the demand of the laser with specific wavelengths is increasing. For example: third harmonic generation (Third Harmonic Generation, THG) is carried out on a picosecond laser with the wavelength of 1064nm to obtain ultraviolet laser with the wavelength of 355nm, and the generated ultraviolet light can be suitable for processing transparent materials; the ultraviolet laser with the wavelength of 355nm can be further subjected to frequency multiplication to obtain the deep ultraviolet laser with the wavelength of 177.3nm, and the method can be applied to a high-energy resolution angle resolution photoelectron spectrometer.
In the astronomical observation field, laser with the wavelength of 1064nm and 1319nm is generally utilized for summation frequency to obtain sodium yellow light with the wavelength of 589nm, and the 589nm sodium yellow light laser can be used in an adaptive optical system of a large-scale foundation telescope. The nonlinear crystal which is commonly used at present is LBO, and an antireflection film with specific wavelength is plated on the end face of the nonlinear crystal for reducing the loss of laser. However, the thicker film layer can cause the end face damage threshold to be reduced, and the crystal is easy to damage when the laser operates at high power, so that the output power of the laser is limited, and the practical application requirement cannot be met.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and proposes a nonlinear frequency conversion crystal.
The invention provides a nonlinear frequency conversion crystal, which comprises an incidence inclined plane, an emergent inclined plane and a side emergent window;
the incidence inclined plane is positioned at the first end of the crystal, the emergent inclined plane is positioned at the second end of the crystal, the side emergent window is close to the second end of the crystal, the incidence inclined plane and the side face form a first preset angle, and the emergent inclined plane and the side emergent window form a second preset angle;
the fundamental frequency light beam enters the crystal at an angle of the first preset angle with the normal of the incident inclined plane, the fundamental frequency light beam carries out nonlinear frequency conversion in the crystal to generate an emergent variable frequency light beam, the emergent variable frequency light beam and the fundamental frequency light beam which does not participate in the nonlinear frequency conversion form a mixed light beam in the crystal and are transmitted parallel to the central axis of the crystal, and the fundamental frequency light beam which does not participate in the nonlinear frequency conversion comprises a fundamental frequency light beam a which does not participate in the nonlinear frequency conversion and a fundamental frequency light beam b which does not participate in the nonlinear frequency conversion; the mixed light beam and the emergent inclined plane form a second preset angle to emergent the crystal, so that two light beams of an emergent variable-frequency light beam and a fundamental frequency light beam a which does not participate in nonlinear frequency conversion are formed, and the other fundamental frequency light beam b which does not participate in nonlinear frequency conversion is reflected to the side emergent window by the emergent inclined plane to be emergent;
furthermore, the phase matching direction of the crystal is parallel to the central axis of the crystal, so that the fundamental frequency light beam incident through the incidence inclined plane is transmitted along the central axis direction of the crystal and is subjected to nonlinear frequency conversion.
Further, the first preset angle is the brewster angle of the incident fundamental frequency beam, and is determined by the wavelength of the fundamental frequency beam.
Further, the second preset angle is the brewster angle of the outgoing variable-frequency light beam, and is determined by the wavelength of the outgoing variable-frequency light beam.
Furthermore, the incident fundamental frequency beam, the crystal central axis and the emergent variable frequency beam are not in the same plane.
Further, the fundamental frequency light beam is one or more beams.
Further, the types of nonlinear frequency conversion performed in the crystal include frequency multiplication, difference frequency, sum frequency, and optical parametric conversion.
Further, the types of the crystals include, but are not limited to, lithium triborate crystals LBO, potassium titanyl phosphate crystals KTP, barium metaborate crystals BBO, potassium dihydrogen phosphate KDP.
Further, the incident inclined plane, the emergent inclined plane and the side emergent window are all polished.
Further, the side exit window is coated with a fundamental frequency light antireflection film.
The invention has the technical effects that:
compared with the prior art, the nonlinear frequency conversion crystal has the advantages that the front end face cutting angle is the brewster angle of fundamental frequency light, the rear end face cutting angle is the brewster angle of variable frequency light, and the nonlinear crystal with the double-end brewster angle cutting structure is formed, so that the transmission crystal with no loss is formed when the fundamental frequency light beam and the frequency converted light beam are not coated on the front end face and the rear end face, the damage resistance of the crystal end face is further improved, the crystal can bear larger laser power, and accordingly higher variable frequency laser output is obtained.
Drawings
FIG. 1 is a schematic diagram of a nonlinear frequency conversion crystal in accordance with embodiment 1 of the present invention;
FIG. 2 is a top view of FIG. 1;
FIG. 3 is a front view of FIG. 1;
FIG. 4 is a schematic diagram of a frequency doubling LBO crystal of embodiment 2 of the present invention;
FIG. 5 is a schematic diagram of the structure of a sum frequency LBO crystal of embodiment 3 of the present invention;
fig. 6 is a schematic structural diagram of an optical parametric converting LBO crystal according to embodiment 4 of the present invention.
In the figure, an entrance bevel 101, an exit bevel 102, a side exit window 103, a side 104, a fundamental frequency beam 11, a mixed beam 12, a fundamental frequency beam a13 which does not participate in nonlinear frequency conversion, a fundamental frequency beam b14 which does not participate in nonlinear frequency conversion, and an exit variable frequency beam 21;
frequency-doubled LBO crystal 20, fundamental beam a51, mixed beam a52, fundamental beam c53 not participating in nonlinear frequency conversion, fundamental beam d54 not participating in nonlinear frequency conversion, frequency-doubled beam 22, power meter 1, light collector a2, light collector b3, light collector c4;
the sum frequency LBO crystal 30, the fundamental frequency beam b61, the fundamental frequency beam c62, the mixed beam b63, the fundamental frequency beam e64 not participating in nonlinear frequency conversion, the fundamental frequency beam f65 not participating in nonlinear frequency conversion, the fundamental frequency beam g66 not participating in nonlinear frequency conversion, the fundamental frequency beam h67 not participating in nonlinear frequency conversion, and the sum frequency beam 23;
an optical parametric LBO crystal 40, a pump beam 71, a mixed beam d72, a pump beam e73 without optical parametric conversion, a pump beam g74 without optical parametric conversion, an idler beam f24, a signal beam 25, an idler beam h26.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings of the specification.
Example 1:
as shown in fig. 1, 2 and 3, fig. 1 is a perspective view of a nonlinear frequency conversion crystal provided in an embodiment of the present invention, fig. 2 is a top view of the crystal, and shows an incidence angle of a fundamental frequency beam in fig. 1, wherein only an optical path of one fundamental frequency beam is shown in fig. 1, and the fundamental frequency beam is one or more of the fundamental frequency beams. Fig. 3 is a front view of the crystal of fig. 1, showing the angle of emergence of the variable frequency beam and the fundamental frequency beam not participating in the nonlinear frequency conversion.
The nonlinear frequency conversion crystal provided in this embodiment includes an entrance bevel 101, an exit bevel 102, and a side exit window 103.
The incident inclined plane 101 is located at a first end of the crystal, the exit inclined plane 102 is located at a second end of the crystal, the side exit window 103 is located at a side of the crystal and is close to the second end, and the incident inclined plane 101 forms a first preset angle omega with the side 104 1 The exit bevel 102 forms a second predetermined angle ω with the side exit window 103 2 。
The fundamental frequency beam 11 forms the first preset angle ω with the normal line of the incident inclined plane 101 1 Is transmitted parallel to the central axis of the crystal, the fundamental frequency beam 11 is subjected to nonlinear frequency conversion in the crystal to generate an outgoing variable frequency beam 21, the outgoing variable frequency beam 21 and the fundamental frequency beam which does not participate in nonlinear frequency conversion form a mixed beam 12, and the mixed beam is transmitted parallel to the central axis of the crystalThe fundamental frequency beams include a fundamental frequency beam a13 which does not participate in nonlinear frequency conversion and a fundamental frequency beam b14 which does not participate in nonlinear frequency conversion; the mixed light beam 12 makes the second predetermined angle ω with the exit bevel 102 2 The crystal is emitted to form two light beams of an emergent variable-frequency light beam 21 and a fundamental-frequency light beam a13 which does not participate in nonlinear frequency conversion, and the other part of fundamental-frequency light beam b14 which does not participate in nonlinear frequency conversion is reflected to the side emergent window 103 by the emergent inclined plane 102 to be emergent.
The phase matching direction of the crystal is parallel to the central axis of the crystal, so that the fundamental frequency light beam 11 incident through the incidence inclined plane 101 is transmitted along the central axis direction of the crystal and subjected to nonlinear frequency conversion.
The incident fundamental frequency beam 11, the crystal center axis and the outgoing variable frequency beam 21 are not in the same plane. The first preset angle omega 1 The brewster angle, which is the fundamental light, is determined by the wavelength of the fundamental light beam 11. The second preset angle omega 2 The complementary angle to the brewster angle of the converted light is determined by the wavelength of the outgoing converted light beam 21.
Specifically, as shown in fig. 2, the normal angle θ between the fundamental beam 11 and the incident inclined plane 101 is incident into the crystal through the incident inclined plane 101, according to brewster's principle, when the reflected light is perpendicular to the refracted light, the incident light is converted into the refracted light, and at this time, the normal angle θ between the fundamental beam 11 and the incident inclined plane 101 is the brewster angle of the fundamental beam 11, the fundamental beam 11 can be incident into the crystal without loss, and according to the brewster's principle and the refraction law, the normal angle θ between the fundamental beam 11 and the incident inclined plane 101 and the refractive index n of the crystal in air g1 The relationship of (2) can be expressed as:
θ＝arctan(n g1 )，
wherein n is g1 Is the refractive index of the crystal corresponding to the fundamental beam 11.
To ensure that the mixed beam 12 propagates parallel to the central axis of the crystal inside the crystal, it is necessary to align the crystalCutting the front end face of the crystal, wherein the cutting angle is the first preset angle omega 1 According to the geometric relationship, the first preset angle omega 1 Equal to the fundamental frequency beam 11 and the normal angle theta of the incidence inclined plane 101.
As shown in fig. 3, the mixed light beam 12 is split by the exit bevel 102, the outgoing variable frequency light beam 21 and the fundamental frequency light beam a13 not participating in the nonlinear frequency conversion are transmitted by the exit bevel 102, and the fundamental frequency light beam b14 not participating in the nonlinear frequency conversion is reflected by the exit bevel 102 to the side exit window 103. In order to allow the converted light beam to exit the crystal without loss, the angle α between the mixed light beam 12 and the exit inclined plane 102 is required to be the brewster angle of the outgoing converted light beam 21 according to brewster's principle, and the angle α between the mixed light beam 12 and the exit inclined plane 102 and the refractive index n of the crystal are required to be the brewster angle in air g2 The relationship of (2) can be expressed as:
α＝arctan(n g2 )，
wherein n is g2 The refractive index for the crystal corresponding to the outgoing variable frequency light beam 21. Since the mixed beam 12 is transmitted parallel to the central axis inside the crystal, the rear end face of the crystal is cut at the second predetermined angle ω 2 The second preset angle omega according to the geometric relation 2 Equal to the angle alpha between the transmission direction of the mixed beam 12 and the exit bevel 102.
The fundamental frequency beam 11 is one or more beams. Specifically, since the direction of the fundamental frequency beam 11 matches with the phase matching direction of the crystal in the embodiment of the present invention, the transmission and frequency conversion in the crystal are not affected by the fundamental frequency beam 11 in one or more beams. The number of the fundamental frequency beams 11 may be set as required, and in the embodiment of the present invention, the number of the fundamental frequency beams 11 is not particularly limited.
Types of nonlinear frequency conversion performed within the crystal include frequency multiplication, difference frequency, sum frequency, optical parametric conversion, and the like. The types of the crystals comprise lithium triborate crystals LBO, potassium titanyl phosphate crystals KTP, barium metaborate crystals BBO and potassium dihydrogen phosphate KDP.
The entrance bevel 101, the exit bevel 102 and the side exit window 103 are all polished. In particular, polishing refers to the reduction of the roughness of a plane by mechanical, chemical or electrochemical action to obtain a bright, flat crystal surface. The side exit window is coated with an antireflection film.
Example 2:
FIG. 4 is a schematic diagram showing a frequency doubling LBO crystal according to another embodiment of the present invention; the crystal is a frequency doubled LBO crystal 20 with a phase matching angle θ=90°, Φ=0°. The angle θ is the angle between the transmission direction of the fundamental beam (i.e., the wave vector direction) and the crystal axis direction of the frequency doubling LBO crystal 20, and the angle phi is the angle between the projection of the transmission direction of the fundamental beam perpendicular to the crystal axis direction and the x-axis.
In the present embodiment, the wavelength of the fundamental frequency beam a51 is 1064nm, the wavelength of the frequency-doubled beam 22 is 532nm, and the first predetermined angle ω 3 At 58.4 deg., a second predetermined angle omega 4 58.4 deg.. The included angle between the fundamental frequency beam a51 and the normal line of the incident inclined plane 101 is 58.4 degrees, and the fundamental frequency beam a51 can enter the frequency doubling LBO crystal 20 without loss, so that the beam entering the frequency doubling LBO crystal 20 is transmitted along the phase matching direction. The fundamental frequency beam a51 with 1064nm completes nonlinear frequency conversion to obtain frequency multiplication light with the wavelength of 532nm before reaching the exit inclined plane 102, the frequency multiplication light beam 22 and the fundamental frequency beam which does not participate in nonlinear frequency conversion form a mixed light beam a52 to be transmitted to the exit inclined plane 102, wherein the frequency multiplication light beam 22 emits the frequency multiplication LBO crystal 20 through the exit inclined plane 102 without loss, part of the fundamental frequency beam c53 which does not participate in nonlinear frequency conversion emits the frequency multiplication LBO crystal 20 through the exit inclined plane 102, and the other part of the fundamental frequency beam d54 which does not participate in nonlinear frequency conversion is reflected to the side exit window 103 through the exit inclined plane 102 to emit the frequency multiplication LBO crystal 20. The power meter 1 is used for measuring the power of 532nm laser obtained by frequency multiplication, the light collector a2 and the light collector b3 are used for collecting 1064nm fundamental frequency light, and the side exit window 103 is plated with 1064nm laser antireflection film. Therefore, the fundamental frequency light beam and the frequency converted light beam can be transmitted through the crystal without loss under the condition that the front end surface and the rear end surface are not coated with films. In summary, the embodiment of the invention providesThe frequency multiplication LBO crystal improves the damage resistance of the end face of the crystal, so that the crystal can bear larger laser power.
Example 3:
FIG. 5 is a schematic diagram showing a structure of a sum frequency LBO crystal according to another embodiment of the present invention; the crystal is a sum frequency LBO crystal 30 with a phase matching angle θ=90°, Φ=0°. The angle θ is the angle between the transmission direction of the fundamental frequency beam (i.e., the wave vector direction) and the crystal axis direction of the sum frequency LBO crystal 30, and the angle phi is the angle between the projection of the transmission direction of the fundamental frequency beam perpendicular to the crystal axis direction and the x-axis.
In this embodiment, the fundamental beam b61 has a wavelength of 1064nm, the fundamental beam c62 has a wavelength of 1319nm, and the frequency beam 23 has a wavelength of 589nm. A first preset angle omega 5 At 58 ° (note: calculating a first predetermined angle ω with reference to 1319nm fundamental beam c62 5 ) A second preset angle omega 6 58.04 deg.. Since the refractive indexes of the crystal are different for the light beams with different wavelengths, the refraction angles of the two light beams after the light beams with different wavelengths are incident into the crystal at the same incident angle are different, and the deviation influence and the frequency efficiency can be generated between the light beams, so that the influence of the angle difference of 0.2 degrees on the transmissivity of 1064nm fundamental frequency light is negligible in order to ensure that the refraction angles of the fundamental frequency light beam b61 and the fundamental frequency light beam c62 are the same, and the calculated incident angle of the fundamental frequency light beam b61 is 58.28 degrees, and the Brewster angle of the fundamental frequency light beam b61 is 58.08 degrees.
The included angle between the fundamental frequency beam b61 and the normal line of the first incident surface 101 is 58.28 degrees, the fundamental frequency beam c62 and the normal line of the first incident surface 101 are 58 degrees, the fundamental frequency beam c62 and the fundamental frequency beam c 61 of 1064nm and the fundamental frequency beam c 23 of 1319nm are obtained through nonlinear frequency conversion, the fundamental frequency beam b63 and the fundamental frequency beam of 1064nm and 1319nm which do not participate in nonlinear frequency conversion form a mixed beam b63, the mixed beam b63 is emitted from the outgoing inclined plane 102 to the fundamental frequency LBO crystal 30, wherein the fundamental frequency beam c 23 is emitted from the outgoing inclined plane 102 in a lossless manner, the fundamental frequency beam e64 of 1319nm which do not participate in nonlinear frequency conversion and the fundamental frequency beam f65 of 1064nm which do not participate in nonlinear frequency conversion are emitted from the outgoing inclined plane 102 to the fundamental frequency LBO crystal 30, and the fundamental frequency beam g66 (1064 nm) which do not participate in nonlinear frequency conversion and the fundamental frequency beam h67 (9 nm) which do not participate in nonlinear frequency conversion are reflected from the outgoing inclined plane 102 to the lateral side window 103 to the fundamental frequency LBO crystal 30. The power meter 1 is used for measuring the power of 589nm laser obtained by summation frequency, the light collector a2, the light collector b3 and the light collector c4 are used for collecting 1064nm and 1319nm fundamental frequency light, and the side exit window 103 is plated with double-point 1064nm and 1319nm laser antireflection films. Therefore, the transmission crystal with no loss can be formed by the fundamental frequency light and the sum frequency light under the condition that the front end surface and the rear end surface are not coated with films. In summary, the sum frequency LBO crystal provided by the embodiment of the invention improves the damage resistance of the crystal end surface, so that the crystal can bear larger laser power.
Example 4:
FIG. 6 is a schematic diagram showing a structure of an optical parametric converting LBO crystal according to another embodiment of the present invention; the crystal is an optical parametric LBO crystal 40 with phase matching angles θ=90°, Φ=0°. The angle θ is the angle between the transmission direction of the fundamental beam (i.e., the wave vector direction) and the crystal axis direction of the optical parametric LBO crystal 40, and the angle phi is the angle between the projection of the transmission direction of the fundamental beam perpendicular to the crystal axis direction and the x-axis. In this embodiment, the pump beam 71 has a wavelength of 532nm, the signal beam 25 has a wavelength of 760nm, and the idler beam has a wavelength of 1770nm. A first preset angle omega 7 58.09 DEG, a second predetermined angle omega 8 58.19 (note: in this embodiment, the signal light is the target wavelength, and in practice, the second preset angle may be set as needed).
The pump beam 71 enters the optical parametric LBO crystal 40 at an angle of 58.09 ° with respect to the normal line of the first incident surface 101, and the pump beam 71 can enter the optical parametric LBO crystal 40 without loss, so that the beam entering the optical parametric LBO crystal 40 is transmitted along the phase matching direction. The pump beam 71 performs optical parametric conversion before reaching the exit bevel 102 to obtain signal light with 760nm wavelength and 1770nm idler light; the mixed beam d72 consisting of 532nm pump light, 760nm signal light and 1770nm idler light is emitted out of the optical parametric LBO crystal 40 through the exit inclined plane 102, wherein the signal beam 25 is emitted out of the optical parametric LBO crystal 40 through the exit inclined plane 102 without loss, part of the pump beam e73 without optical parametric conversion and part of the idler beam f24 are emitted out of the optical parametric LBO crystal 40 through the exit inclined plane 102, and the other part of the pump beam g74 without optical parametric conversion and the other part of the idler beam h26 are reflected to the side exit window 103 through the exit inclined plane 102 to be emitted out of the optical parametric LBO crystal 40. The power meter 1 is used for measuring the power of 760nm signal light obtained by optical parameter conversion, the light collector a2, the light collector b3 and the light collector c4 are used for collecting pump light and idler frequency light, and the side emergent window 103 is plated with double-point 532nm and 1770nm laser antireflection films. Therefore, the pump light and the signal light can be transmitted through the crystal without loss under the condition that the front end surface and the rear end surface are not coated with films. In summary, the optical parametric conversion LBO crystal provided by the embodiment of the invention improves the damage resistance of the crystal end surface, so that the crystal can bear larger laser power.

Claims (10)

1. A nonlinear frequency conversion crystal, characterized in that the crystal comprises an entrance bevel (101), an exit bevel (102) and a side exit window (103);
the incidence inclined plane (101) is positioned at the first end of the crystal, the emergent inclined plane (102) is positioned at the second end of the crystal, the side emergent window (103) is close to the second end of the crystal, and the incidence inclined plane (101) and the side (104) form a first preset angle (omega) 1 ) The exit bevel (102) forms a second predetermined angle (omega) with the side exit window (103) 2 )；
The fundamental frequency beam (11) forms a first predetermined angle (omega) with the normal to the oblique plane of incidence (101) 1 ) The fundamental frequency light beam (11) performs nonlinear frequency conversion in the crystal to generate an emergent variable frequency light beam (21), the emergent variable frequency light beam (21) and the fundamental frequency light beam which does not participate in nonlinear frequency conversion form a mixed light beam (12) in the crystal, the mixed light beam is transmitted parallel to the central axis of the crystal, and the fundamental frequency light beam which does not participate in nonlinear frequency conversion comprises a fundamental frequency light beam a (13) which does not participate in nonlinear frequency conversion and a fundamental frequency light beam b (14) which does not participate in nonlinear frequency conversion; the mixed light beam (12) forms the second preset angle (omega) with the outgoing inclined plane (102) 2 ) Emitting the crystal to form an emitted variable frequency beam (21) and a non-participating non-linear frequencyThe converted fundamental frequency light beam a (13) is divided into two light beams, and the other part of fundamental frequency light beam b (14) which does not participate in nonlinear frequency conversion is reflected to the side exit window (103) by the exit bevel plane (102) to be emitted.
2. The nonlinear frequency conversion crystal according to claim 1, wherein the phase matching direction of the crystal is parallel to the central axis of the crystal, so that the fundamental frequency light beam (11) incident through the incidence inclined plane (101) is transmitted in the crystal central axis direction and nonlinear frequency conversion is performed.
3. The nonlinear frequency conversion crystal according to claim 1, wherein the first preset angle (ω 1 ) Is the Brewster angle of the incident fundamental beam (11).
4. The nonlinear frequency conversion crystal according to claim 1, wherein the second preset angle (ω 2 ) Is the Brewster angle of the outgoing variable frequency light beam (21).
5. Nonlinear frequency conversion crystal according to claim 1, characterized in that the incident fundamental frequency beam (11), the crystal center axis and the outgoing variable frequency beam (21) are not in the same plane.
6. Nonlinear frequency conversion crystal according to any one of claims 1-5, characterized in that the fundamental light beam (11) is one or more beams.
7. The nonlinear frequency conversion crystal according to any one of claims 1-5, wherein the type of nonlinear frequency conversion performed within the crystal comprises frequency multiplication, difference frequency, sum frequency, optical parametric conversion.
8. The nonlinear frequency conversion crystal according to any one of claims 1 to 5, wherein the type of crystal includes lithium triborate crystal LBO, potassium titanyl phosphate crystal KTP, barium metaborate crystal BBO, potassium dihydrogen phosphate KDP.
9. The nonlinear frequency conversion crystal according to any one of claims 1-5, wherein the entrance bevel (101), the exit bevel (102) and the side exit window (103) are each subjected to a polishing treatment.
10. The nonlinear frequency conversion crystal according to any one of claims 1-5, wherein the side exit window (103) is coated with a fundamental light antireflection film.
CN202311124804.8A 2023-09-02 2023-09-02 Nonlinear frequency conversion crystal Pending CN117406529A (en)

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CN202311124804.8A CN117406529A (en) 2023-09-02 2023-09-02 Nonlinear frequency conversion crystal

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CN117406529A true CN117406529A (en) 2024-01-16

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