CN111416263B - Terahertz source based on non-collinear phase matching difference frequency of phosphorus-germanium-zinc crystal - Google Patents
Terahertz source based on non-collinear phase matching difference frequency of phosphorus-germanium-zinc crystal Download PDFInfo
- Publication number
- CN111416263B CN111416263B CN202010203279.9A CN202010203279A CN111416263B CN 111416263 B CN111416263 B CN 111416263B CN 202010203279 A CN202010203279 A CN 202010203279A CN 111416263 B CN111416263 B CN 111416263B
- Authority
- CN
- China
- Prior art keywords
- wavelength laser
- germanium
- phosphorus
- laser
- fixed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 239000013078 crystal Substances 0.000 title claims abstract description 80
- MOHPKPMGPNKIKH-UHFFFAOYSA-N [Zn].[Ge].[P] Chemical compound [Zn].[Ge].[P] MOHPKPMGPNKIKH-UHFFFAOYSA-N 0.000 title claims abstract description 59
- 238000003384 imaging method Methods 0.000 claims abstract description 23
- 230000003993 interaction Effects 0.000 claims abstract description 10
- 230000005540 biological transmission Effects 0.000 claims abstract description 8
- 230000003287 optical effect Effects 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 11
- 230000000694 effects Effects 0.000 claims description 5
- 230000010287 polarization Effects 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 description 9
- 230000005855 radiation Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 3
- 230000001427 coherent effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- MRZMQYCKIIJOSW-UHFFFAOYSA-N germanium zinc Chemical compound [Zn].[Ge] MRZMQYCKIIJOSW-UHFFFAOYSA-N 0.000 description 2
- 229910005543 GaSe Inorganic materials 0.000 description 1
- 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
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- 239000013598 vector Substances 0.000 description 1
- -1 zinc-phosphorus-germanium-zinc Chemical compound 0.000 description 1
Classifications
-
- 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
- H01S1/00—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range
- H01S1/02—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range solid
-
- 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
-
- 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
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/16—Solid materials
- H01S3/163—Solid materials characterised by a crystal matrix
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Nonlinear Science (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses a terahertz source based on non-collinear phase matching difference frequency of a phosphorus-germanium-zinc crystal, which comprises a fixed wavelength laser, a rotary reflecting mirror, a first convex lens, a second convex lens and a phosphorus-germanium-zinc crystal, wherein the fixed wavelength laser, the rotary reflecting mirror, the first convex lens, the second convex lens and the phosphorus-germanium-zinc crystal are sequentially arranged; the same side of the fixed wavelength laser and the rotary reflecting mirror is respectively provided with a variable wavelength laser and a fixed reflecting mirror; the frequency difference between the fixed wavelength laser emitted by the fixed wavelength laser and the variable wavelength laser is continuously adjustable within 1.88-4.49THz by adjusting the variable wavelength laser emitted by the variable wavelength laser; the fixed wavelength laser and the variable wavelength laser which pass through a telescope imaging system consisting of a first convex lens and a second convex lens are incident into the phosphorus germanium zinc crystal at a small angle and have difference frequency interaction; the telescope imaging system can realize 1:1 imaging, and the spot sizes and the transmission directions of the axial fixed wavelength laser and the off-axis variable wavelength laser at the rotary reflecting mirror are reproduced in the phosphorus-germanium-zinc crystal, so that small-angle non-collinear phase matching is realized.
Description
Technical Field
The invention belongs to the technical field of nonlinear optical frequency conversion, and particularly relates to a method for obtaining high-efficiency terahertz wave output by remarkably improving the effective nonlinear coefficient of the difference frequency in a phosphorus-germanium-zinc crystal in a mode of non-collinear phase matching with a small angle included angle.
Background
Terahertz (THz) technology enjoys the reputation of changing one of the ten technologies in the future world, and its application research field is very wide. However, due to the lack of efficient and stable THz transmitting antennas and radiation sources, commercialization is not yet possible in many application fields, which requires more effort on innovation and improvement of radiation sources. Currently, the technical means for effectively generating terahertz waves are broadly divided into optical means and electrical means. The terahertz waves generated by the nonlinear Difference Frequency (DFG) of the optical means have the advantages of higher emergent power, continuous tunable wavelength, narrow line width, room temperature operation and the like. For birefringent crystals, the difference frequency generation of terahertz waves is usually achieved in a collinear phase matching mode, and for crystals lacking birefringence, the difference frequency generation of terahertz waves is usually achieved in a non-collinear phase matching mode.
However, in collinear phase matching of birefringent crystals, since the effective nonlinear coefficient is related to the phase matching angle, the value will be severely limited by the phase matching angle, and the whole difference frequency process often cannot be performed under a higher effective nonlinear coefficient. For efficient performance of the difference frequency effect, it is desirable that the larger the effective nonlinear coefficient, the better. As a highly efficient nonlinear optical material commonly used for frequency conversion generation of mid-infrared and terahertz waves, a new scheme for generating terahertz radiation by amplifying dual-wavelength laser by utilizing a polarization-preserving ytterbium-doped optical fiber and then transmitting the amplified dual-wavelength laser to the phosphor-germanium-zinc crystal is proposed by the inventor CreedenD, wherein the scheme adopts o-e- & gt-e type collinear birefringent phase matching when the o-e and o-e- & gt-o type collinear birefringent phase matching is adopted, the difference frequency generates coherent terahertz radiation with the frequency ranging from 1 to 4.51THz and from 1.26 to 4.13THz continuously adjustable for (Shi W,Ding Y J.Continuously tunable and coherent terahertz radiation by means of phase-matched difference-frequency generation in zinc germanium phosphide[J].Applied physics letters,2003,83(5):848-850).2007 years, and the scheme adopts o-e- & gt-e type collinear birefringent phase matching, the phase matching angle is reduced, the effective nonlinear coefficient is also reduced, so that the terahertz output power is limited by (Creeden D,McCarthy J C,Ketteridge P A,et al.Compact fiber-pumped terahertz source based on difference frequency mixing in ZGP.IEEE Journal of Selected Topics in Quantum Electronics,2007,13(3):732-737).2008 years, the Liu Huan et al calculate and simulate the phase matching angle and the effective nonlinear coefficient of various collinear phase matching modes by utilizing the phosphorus germanium zinc crystal, summarize the optimal collinear phase matching modes corresponding to different THz wave bands, and the effective nonlinear coefficient is strictly limited by the phase matching angle for the o-e- & gt and o-e- & gt e of the phosphorus germanium zinc crystal, and the calculated maximum value is only 13.526pm/V and 26.486pm/V (both corresponding to the terahertz frequency of 4.38 THz) (Liu Huan, xu Degang, yao Jianquan. Theoretical research on generating tunable terahertz radiation based on the difference frequency of GaSe and ZnGeP 2 crystals. 2008). In 2009, li Guang studied the characteristics of an infrared laser in a zinc-phosphorus-germanium crystal, and also theoretically described the relationship between the effective nonlinear coefficient and both the phase matching type and the phase matching angle, and pointed out that the conversion efficiency is greatly affected by the effective nonlinear coefficient (Li Guang. Research on the characteristics of an infrared laser in ZnGeP 2. University of Beijing industry, 2009). Obviously, in collinear phase matching optical difference frequency, the effective nonlinear coefficient of the phosphorus germanium zinc crystal is often greatly influenced by the change of the phase matching type and the propagation angle of the light wave.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a terahertz source based on non-collinear phase matching high-efficiency difference frequency of a phosphorus-germanium-zinc crystal, the efficiency of generating terahertz waves by the difference frequency is obviously improved by improving the effective nonlinear coefficient of the terahertz radiation process generated by the difference frequency in the phosphorus-germanium-zinc crystal, and compared with the common collinear phase matching method, the method has the advantages that the conversion efficiency of the terahertz waves is improved by more than 4.5 times and more than one order of magnitude.
The invention aims at realizing the following technical scheme:
A terahertz source based on non-collinear phase matching difference frequency of a phosphorus-germanium-zinc crystal comprises a fixed wavelength laser, a rotary reflecting mirror, a first convex lens, a second convex lens and a phosphorus-germanium-zinc crystal which are sequentially arranged; the same side of the fixed wavelength laser and the rotary reflecting mirror is respectively provided with a variable wavelength laser and a fixed reflecting mirror; the frequency difference between the fixed wavelength laser emitted by the fixed wavelength laser and the variable wavelength laser is continuously adjustable within 1.88-4.49THz by adjusting the variable wavelength laser emitted by the variable wavelength laser; the variable wavelength laser is reflected to the rotary reflecting mirror through the fixed reflecting mirror, reflected again and then enters a telescope imaging system formed by the first convex lens and the second convex lens in an off-axis manner; the fixed wavelength laser is transmitted through the rotary reflector and then enters a telescope imaging system formed by a first convex lens and a second convex lens along the system optical axis; the fixed wavelength laser and the variable wavelength laser after passing through the telescope imaging system are incident into the phosphorus-germanium-zinc crystal at a certain small angle and have difference frequency interaction;
The distance between the first convex lens and the rotary reflecting mirror in the telescope imaging system and the distance between the second convex lens and the interaction position in the phosphorus germanium zinc crystal are the same as the focal length f of the two convex lenses, and the distance between the two convex lenses is 2f, so that the telescope imaging system can realize 1:1 imaging, and the spot sizes and the transmission directions of the axial fixed wavelength laser and the off-axis variable wavelength laser at the rotary reflecting mirror are reproduced in the phosphorus germanium zinc crystal, thereby realizing small-angle non-collinear phase matching.
Furthermore, the fixed wavelength laser participating in interaction is the ordinary light in the phosphorus germanium zinc crystal, and the propagation direction (namely the optical axis direction of the telescope imaging system) is perpendicular to the z axis along the angular bisector direction of the x axis and the y axis of the crystal; the variable wavelength laser is an extraordinary ray in the phosphorus-germanium-zinc crystal, the propagation direction of the variable wavelength laser is in a plane formed by the propagation direction of the fixed wavelength laser and the z axis of the crystal, the included angle between the variable wavelength laser and the z axis of the crystal is theta, and the included angle between the variable wavelength laser and the propagation direction of the fixed wavelength laser is phi, phi = pi/2-theta; the non-collinear difference frequency of the fixed wavelength laser and the variable wavelength laser generates terahertz waves in a class II phase matching mode (o-e- & gt o), the generated terahertz waves are ordinary rays, and an included angle between the propagation direction of the terahertz waves and the propagation direction of the fixed wavelength laser is alpha; the effective nonlinear coefficient of the difference frequency process is calculated asWherein/>For the included angle between the propagation direction of the laser with fixed wavelength and the x axis of the zinc-germanium-phosphorus crystal, because θ=90°, and/(respectively) at the momentThe effective nonlinear coefficient reaches a maximum value d 36, and the difference frequency efficiency is highest;
the fixed wavelength laser, the variable wavelength laser and the terahertz wave satisfy the following relations:
Omega 1、ω2 and omega 3 are the angular frequencies of the three waves, n 1、n2 and n 3 are the refractive indexes of the three waves in the zinc-phosphorus-germanium crystal (7), and lambda 1、λ2 and lambda 3 are the wavelengths of the three waves in vacuum; k 1、k2、k3 is the refractive index of the three waves of the space angular frequency ;k1＝n1ω1/c、k2＝n2ω2/c、k3＝n3ω3/c; of the three waves in the phosphorus-germanium-zinc crystal, and the refractive index is as follows:
Wherein n o represents the ordinary refractive index, n e represents the extraordinary refractive index, and the wavelength λ i has units of μm (i=1, 2, 3 represent fixed wavelength laser, variable wavelength laser, and terahertz wave, respectively); the included angle alpha between the terahertz wave propagation direction generated in the phosphorus-germanium-zinc crystal and the laser propagation direction with fixed wavelength meets the following conditions:
Further, the fixed wavelength laser is a Nd with high beam quality: YAG Q-switched laser with a center wavelength of 1064nm, and one variable wavelength laser passing through Nd: the wavelength tuning range of the tunable optical parametric oscillator of the YAG laser frequency multiplication post-pump is 1064-1082nm.
Furthermore, the fixed reflecting mirror is a dielectric film reflecting mirror with high reflection to the wavelength range of 1064-1082nm, the rotary reflecting mirror is a polarization beam splitting prism or a Brewster sheet, the fixed reflecting mirror is high in transmission to 1064nm laser emitted by the fixed wavelength laser, the fixed reflecting mirror is high in reflection to 1064-1082nm tunable laser emitted by the variable wavelength laser, and off-axis angle tuning can be realized to laser emitted by the variable wavelength laser.
Further, the first convex lens and the second convex lens are biconvex or plano-convex lenses plated with 1064-1082nm wave band antireflection films, and the focal length of the lenses is 100-300mm.
Further, the light passing direction of the p-ge-zn crystal is perpendicular to the optical axis z axis, and on the angular bisectors of the x axis and the y axis (θ=90°, Φ=45°), the included angle α between the output direction of the generated terahertz wave in the range of 1.88-4.49THz and the laser with fixed wavelength is: 0.15-45.70 degrees, wherein the included angle alpha between the terahertz output direction in the range of 1.90-4.49THz and the laser with fixed wavelength ranges from 11.4 degrees to 45.70 degrees; the phosphorus-germanium-zinc crystal is cut in a wedge shape at 61.45 degrees between the output end face and the light transmission direction so as to avoid the effect of total reflection of terahertz waves generated by difference frequency on the surface of the crystal on output
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. the effective nonlinear coefficient of terahertz wave generated by adopting class II phase matching mode (o-e- & gto) difference frequency of the phosphorus-germanium-zinc crystal is Since the phase matching angle θ of the conventional collinear phase matching method is smaller than 10.3 °, the effective nonlinear coefficient d oeo is about 13.526 at the highest, and is far lower than d 36. Power and/>, due to the difference frequency, of terahertz wavesIn proportion, a small d oeo severely limits the conversion efficiency of the nonlinear difference frequency. The small-angle non-collinear phase matching adopted by the invention can realize phase matching at the position of theta=90°, so that the larger nonlinear coefficient d 36 of the phosphorus-germanium-zinc crystal can be fully utilized, and the conversion efficiency of generating terahertz waves by using the difference frequency is greatly improved.
2. According to the scheme for generating terahertz waves by non-collinear phase matching of the zinc-phosphorus-germanium crystal, the terahertz wave frequency tuning range of 1.9-4.49THz generated by the difference frequency can be realized by changing the direction included angle of the fixed wavelength laser and the variable wavelength laser by 0-3 degrees (the phase matching external angle phi), and the traditional collinear phase matching mode needs to be tuned by more than 15 degrees, so that the non-collinear phase matching has a faster angle tuning speed.
3. The terahertz source based on the non-collinear phase matching difference frequency of the phosphorus-germanium-zinc crystal provided by the invention skillfully utilizes a telescope imaging system formed by the biconvex lens, can realize focusing of two incident lights (fixed wavelength laser and variable wavelength laser) participating in the difference frequency so as to improve the difference frequency efficiency, and can realize non-collinear beam combination by utilizing the imaging rule of the convex lens. The angle between the two incident light beams which are not collinear is accurately and quickly controlled by adjusting the rotary reflecting mirror without complicated mechanical structure and adjusting the angle of the phosphorus-germanium-zinc crystal like collinear phase matching.
Drawings
FIG. 1 is a schematic diagram of the structure of a terahertz source of the present invention;
Fig. 2 is a schematic diagram of the crystal direction, the cutting condition and the terahertz wave output of the zinc germanium phosphate provided by the embodiment of the invention;
Fig. 3 is a schematic diagram of a geometrical relationship of non-collinear phase matching of three wave vectors in a zinc germanium phosphorus crystal according to an embodiment of the present invention.
Reference numerals: 1-a fixed wavelength laser; 2-a variable wavelength laser; 3-a fixed mirror; 4-rotating a mirror; 5-convex lenses; 6-convex lenses; 7-phosphorus germanium zinc crystal
Detailed Description
The invention is described in further detail below with reference to the drawings and the specific examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1, the invention provides a terahertz source based on non-collinear phase matching difference frequency of a phosphorus-germanium-zinc crystal, which comprises a fixed wavelength laser 1, a rotary reflecting mirror 4, a convex lens 5, a convex lens 6 and a phosphorus-germanium-zinc crystal 7 which are sequentially arranged; the same side of the fixed wavelength laser 1 and the rotary reflecting mirror 4 is respectively provided with a variable wavelength laser 2 and a fixed reflecting mirror 3;
The fixed wavelength laser 1 is a high-beam-quality Nd-YAG Q-switched laser, and generates fixed wavelength laser with a center wavelength of 1064nm, single pulse energy of 20mJ and pulse width of 10ns. The variable wavelength laser 2 is a tunable optical parametric oscillator which is pumped after frequency multiplication by Nd: YAG laser, and generates tunable laser with wavelength tuning range of 1064-1082nm, single pulse energy of 10mJ, pulse width of 8ns, and polarization direction perpendicular to the laser with fixed wavelength of 1064 nm.
The fixed reflector 3 is a 1064-1082nm high-reflection mirror, the rotary reflector 4 is a polarization beam splitting prism, the high-reflection mirror is high in transmittance to 1064nm laser and high in reflection to tunable laser, off-axis tuning of the tunable laser can be achieved through the rotary polarization beam splitting prism, and the tuning range is larger than 3.1 degrees. The convex lens 5 and the convex lens 6 are identical biconvex lenses, are plated with 1064-1082nm wave band antireflection films, and have a lens focal length of 100mm, so that a double-lens telescope imaging system is formed. The distance between the convex lens 5 and the rotary reflecting mirror 4 in the telescope imaging system and the distance between the convex lens 6 and the three-wave interaction position in the phosphorus germanium zinc crystal 7 are 100mm, and the distance between the two convex lenses is 200mm, so that 1:1 imaging can be realized. The 1064nm fixed wavelength laser and the tunable laser after passing through the telescope imaging system have a certain small angle included angle to generate o-e- & gt o type non-collinear phase matching difference frequency interaction in the phosphorus-germanium-zinc crystal 7.
In the zinc-germanium-phosphorus crystal 7, the light transmission direction (1064 nm fixed wavelength laser propagation direction) is perpendicular to the optical axis z-axis, and on the angular bisector of the x-axis and the y-axisThe angle ψ between the tunable laser light emitted from the variable wavelength laser 2 and the fixed wavelength laser light is changed in the range of 0 to 0.94 °. Through the nonlinear optical difference frequency effect, the difference frequency in the zinc germanium phosphorus crystal 7 generates terahertz waves and outputs the terahertz waves in radiation at a certain angle. As shown in fig. 2, the included angle alpha between the terahertz wave output direction in the range of 1.88-4.49THz and the fixed wavelength laser generated by the difference frequency ranges from 0.15 degrees to 45.70 degrees, wherein the included angle alpha between the terahertz wave output direction in the range of 1.90-4.49THz and the fixed wavelength laser ranges from 11.4 degrees to 45.70 degrees. When the included angle between the terahertz output direction and the normal direction of the output end surface of the crystal is less than or equal to 17.15 degrees, total reflection does not occur, so that the phosphorus germanium zinc crystal 7 is in a 61.45-degree wedge-shaped cutting with the light passing direction at the output end surface, and the effect of total reflection of terahertz waves generated by difference frequency on the crystal surface is avoided.
As shown in fig. 3, in the non-collinear phase matching model of three-wave interaction in the zinc-phosphorus-germanium-zinc crystal 7, k 1、k2 and k 3 are the spatial angular frequencies of the fixed-wavelength laser, the variable-wavelength laser and the terahertz wave, respectively, the z-axis is the crystal optical axis direction, ψ is the included angle between the propagation directions of k 1 and k 2, and α is the included angle between the propagation directions of k 1 and k 3. When the tunable laser wavelength is 1071.7nm and psi=0.227 DEG, the terahertz wave frequency generated by non-collinear phase matching is 2.03THz, alpha=28.55 DEG, the terahertz wave is output perpendicular to the end face, the output energy is about 1 mu J, the conversion efficiency is about 0.1%, and the conversion efficiency is improved by an order of magnitude compared with the traditional collinear difference frequency mode.
In summary, the invention provides a terahertz source based on non-collinear phase matching of a phosphorus-germanium-zinc crystal and high-efficiency difference frequency, which can realize high-power terahertz output by adopting a non-collinear phase matching mode with a small angle included angle in the phosphorus-germanium-zinc crystal. The method remarkably improves the conversion efficiency and the output power of terahertz radiation by improving the effective nonlinear coefficient of the difference frequency process. The method has simple principle, convenient design and good feasibility, and can be applied to other birefringent crystals.
The invention is not limited to the embodiments described above. The above description of specific embodiments is intended to describe and illustrate the technical aspects of the present invention, and is intended to be illustrative only and not limiting. Numerous specific modifications can be made by those skilled in the art without departing from the spirit of the invention and scope of the claims, which are within the scope of the invention.
Claims (6)
1. The terahertz source based on the non-collinear phase matching difference frequency of the phosphorus germanium zinc crystal is characterized by comprising a fixed wavelength laser (1), a rotary reflecting mirror (4), a first convex lens (5), a second convex lens (6) and a phosphorus germanium zinc crystal (7) which are sequentially arranged; the same side of the fixed wavelength laser (1) and the rotary reflecting mirror (4) is respectively provided with a variable wavelength laser (2) and a fixed reflecting mirror (3); the frequency difference between the fixed wavelength laser emitted by the fixed wavelength laser (1) and the variable wavelength laser is continuously adjustable within 1.88-4.49THz by adjusting the variable wavelength laser emitted by the variable wavelength laser (2); the variable wavelength laser is reflected to the rotary reflecting mirror (4) through the fixed reflecting mirror (3), reflected again and enters a telescope imaging system formed by the first convex lens (5) and the second convex lens (6) in an off-axis mode; the fixed wavelength laser is transmitted through the rotary reflecting mirror (4) and then enters a telescope imaging system formed by a first convex lens (5) and a second convex lens (6) along the system optical axis; the fixed wavelength laser and the variable wavelength laser after passing through the telescope imaging system are incident into the phosphorus-germanium-zinc crystal (7) in a non-collinear mode to generate a difference frequency interaction;
the distance between the first convex lens (5) and the rotary reflecting mirror (4) and the distance between the second convex lens (6) and the interaction position in the phosphorus germanium zinc crystal (7) in the telescope imaging system are the same as the focal length f of the two convex lenses, and the distance between the two convex lenses is 2f, so that the telescope imaging system can realize 1:1 imaging, and the spot sizes and the transmission directions of the axial fixed-wavelength laser and the off-axis variable-wavelength laser at the rotary reflecting mirror (4) are reproduced in the phosphorus germanium zinc crystal (7) to realize non-collinear phase matching.
2. The terahertz source based on non-collinear phase matching difference frequency of the p-germanium-zinc crystal according to claim 1, wherein the fixed wavelength laser participating in the interaction is an ordinary ray in the p-germanium-zinc crystal (7), and the propagation direction, i.e. the direction of the optical axis of the telescope imaging system, is perpendicular to the z-axis along the direction of the angular bisector of the x-axis and the y-axis of the p-germanium-zinc crystal; the variable wavelength laser is an extraordinary ray in the phosphorus germanium zinc crystal (7), the propagation direction of the variable wavelength laser is in a plane formed by the propagation direction of the fixed wavelength laser and the z axis of the phosphorus germanium zinc crystal, the included angle between the variable wavelength laser and the z axis of the phosphorus germanium zinc crystal is theta, and the included angle between the variable wavelength laser and the propagation direction of the fixed wavelength laser is phi, phi=pi/2-theta; the terahertz wave generated by the non-collinear difference frequency of the fixed wavelength laser and the variable wavelength laser adopts a class II phase matching mode o-e- & gt o, the generated terahertz wave is ordinary light, and the included angle between the propagation direction of the terahertz wave and the propagation direction of the fixed wavelength laser is alpha; the effective nonlinear coefficient of the difference frequency process is calculated asWherein/>For the included angle between the propagation direction of the laser with fixed wavelength and the x axis of the zinc-germanium-phosphorus crystal (7), since θ=90°,/>The effective nonlinear coefficient reaches a maximum value d 36, and the difference frequency efficiency is highest;
the fixed wavelength laser, the variable wavelength laser and the terahertz wave satisfy the following relations:
Omega 1、ω2 and omega 3 are the angular frequencies of the three waves, n 1、n2 and n 3 are the refractive indexes of the three waves in the zinc-phosphorus-germanium crystal (7), and lambda 1、λ2 and lambda 3 are the wavelengths of the three waves in vacuum; k 1、k2、k3 is the refractive index of the three waves of the space angular frequency ;k1＝n1ω1/c、k2＝n2ω2/c、k3＝n3ω3/c; of the three waves in the phosphorus-germanium-zinc crystal, and the refractive index is as follows:
Wherein n o represents the ordinary refractive index, n e represents the extraordinary refractive index, the unit of the wavelength lambda i is μm, and i=1, 2 and 3 represent fixed wavelength laser, variable wavelength laser and terahertz wave respectively; the included angle alpha between the terahertz wave propagation direction generated in the phosphorus-germanium-zinc crystal and the laser propagation direction with fixed wavelength meets the following conditions:
3. The terahertz source based on the non-collinear phase matching difference frequency of the phosphorus-germanium-zinc crystal according to claim 1, wherein the fixed wavelength laser (1) is a high-beam-quality Nd-YAG Q-switched laser, the center wavelength is 1064nm, and the variable wavelength laser (2) is a tunable optical parametric oscillator pumped after frequency multiplication by Nd-YAG laser, and the wavelength tuning range is 1064-1082nm.
4. The terahertz source based on the non-collinear phase matching difference frequency of the phosphorus-germanium-zinc crystal according to claim 1, wherein the fixed reflecting mirror (3) is a dielectric film reflecting mirror with high reflection to the wavelength range of 1064-1082nm, the rotary reflecting mirror (4) is a polarization beam splitting prism or a brewster sheet, the laser with high transmission to 1064nm emitted by the fixed wavelength laser (1) is high-reflection to the tunable laser with 1064-1082nm emitted by the variable wavelength laser (2), and the off-axis angle tuning to the laser emitted by the variable wavelength laser (2) can be realized.
5. The terahertz source based on non-collinear phase matching difference frequency of zinc-germanium-phosphorus crystals according to claim 1, wherein the first convex lens (5) and the second convex lens (6) are biconvex or plano-convex lenses coated with antireflection films with wave bands of 1064-1082nm, and the focal length of the lenses is 100-300mm.
6. A terahertz source based on non-collinear phase-matching difference frequency of p-germanium-zinc crystals according to claim 2, characterized in that the light passing direction of the p-germanium-zinc crystals (7) is perpendicular to the optical axis z-axis, and on the angular bisectors of the x-axis and y-axis, θ=90°,The included angle alpha range between the output direction of the generated terahertz wave in the range of 1.88-4.49THz and the laser with fixed wavelength is as follows: 0.15-45.70 degrees, wherein the included angle alpha between the terahertz output direction in the range of 1.90-4.49THz and the laser with fixed wavelength ranges from 11.4 degrees to 45.70 degrees; the phosphorus germanium zinc crystal (7) is cut in a wedge shape at the output end face and the light transmission direction at 61.45 degrees so as to avoid the effect of total reflection of terahertz waves generated by difference frequency on the surface of the phosphorus germanium zinc crystal on output.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010203279.9A CN111416263B (en) | 2020-03-20 | 2020-03-20 | Terahertz source based on non-collinear phase matching difference frequency of phosphorus-germanium-zinc crystal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010203279.9A CN111416263B (en) | 2020-03-20 | 2020-03-20 | Terahertz source based on non-collinear phase matching difference frequency of phosphorus-germanium-zinc crystal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111416263A CN111416263A (en) | 2020-07-14 |
| CN111416263B true CN111416263B (en) | 2024-06-07 |
Family
ID=71494457
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010203279.9A Active CN111416263B (en) | 2020-03-20 | 2020-03-20 | Terahertz source based on non-collinear phase matching difference frequency of phosphorus-germanium-zinc crystal |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111416263B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112271441B (en) * | 2020-10-30 | 2023-04-07 | 北京维信诺光电技术有限公司 | Semiconductor device, manufacturing method thereof and antenna system |
| CN113060711B (en) * | 2021-03-19 | 2022-05-10 | 中国科学院新疆理化技术研究所 | Compound cadmium sulfur phosphorus, mercury sulfur phosphorus and mercury infrared nonlinear optical crystal, and preparation method and application thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006091802A (en) * | 2004-09-21 | 2006-04-06 | Semiconductor Res Found | Device and method for terahertz electromagnetic wave generation |
| CN102570247A (en) * | 2012-01-20 | 2012-07-11 | 中国科学院上海技术物理研究所 | Angle tuning-free THz collinear difference frequency radiation system based on cadmium telluride |
| CN212182754U (en) * | 2020-03-20 | 2020-12-18 | 天津大学 | Terahertz source based on phosphorus germanium zinc crystal non-collinear phase matching difference frequency |
-
2020
- 2020-03-20 CN CN202010203279.9A patent/CN111416263B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006091802A (en) * | 2004-09-21 | 2006-04-06 | Semiconductor Res Found | Device and method for terahertz electromagnetic wave generation |
| CN102570247A (en) * | 2012-01-20 | 2012-07-11 | 中国科学院上海技术物理研究所 | Angle tuning-free THz collinear difference frequency radiation system based on cadmium telluride |
| CN212182754U (en) * | 2020-03-20 | 2020-12-18 | 天津大学 | Terahertz source based on phosphorus germanium zinc crystal non-collinear phase matching difference frequency |
Non-Patent Citations (2)
| Title |
|---|
| 基于差频产生太赫兹的中远红外非线性光学晶体;段延敏;朱海永;张戈;邱怡申;黄呈辉;魏勇;黄凌雄;;激光与红外;20071220(12);全文 * |
| 磷化镓高功率太赫兹共线差频源的研究;黄敬国;陆金星;周炜;童劲超;黄志明;褚君浩;;物理学报;20130623(12);全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN111416263A (en) | 2020-07-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5400173A (en) | Tunable mid-infrared wavelength converter using cascaded parametric oscillators | |
| EP3417515B1 (en) | High efficiency laser system for third harmonic generation | |
| CN107425407B (en) | Tunable blue light radiation source based on inner cavity self-frequency multiplication and implementation method | |
| CN111416263B (en) | Terahertz source based on non-collinear phase matching difference frequency of phosphorus-germanium-zinc crystal | |
| CN216850735U (en) | Narrow-linewidth dual-wavelength solid laser | |
| JP2023526164A (en) | Method for generating and using parametric light | |
| CN105119139B (en) | Based on 2 μm of solid state lasers of suspension resonant cavity tunable single longitudinal mode | |
| CN111180987B (en) | Orthogonal polarization dual-wavelength laser with adjustable power proportion | |
| Li et al. | A high-power, long-wavelength infrared ZnGeP 2 OPO pumped by a Q-switched Tm, Ho: GdVO 4 laser | |
| CN109217077B (en) | A kind of tunable hollow laser of self-mixing | |
| CN212182754U (en) | Terahertz source based on phosphorus germanium zinc crystal non-collinear phase matching difference frequency | |
| CN110233416B (en) | Tunable blue light pulse laser | |
| CN112086848B (en) | High-power intracavity pump terahertz wave parametric oscillator for outputting uniform divergence angle round light spots | |
| CN114784607A (en) | Tunable optical parametric oscillator | |
| CN111641097B (en) | Waveguide type electro-optic modulation terahertz wave generator based on lithium niobate crystal | |
| CN110244498B (en) | Nonlinear frequency conversion crystal | |
| CN220021897U (en) | Dual wavelength laser | |
| CN114389137B (en) | Optical parametric oscillation device and conversion method for strip nonlinear crystal | |
| WO2011123822A2 (en) | Apparatus and method for generating continuous wave ultraviolet light | |
| JPH01257922A (en) | Waveguide type wavelength converting element | |
| CN218275499U (en) | High-power nanosecond extra-cavity quintupling frequency laser | |
| Debuisschért et al. | High-beam-quality unstable-cavity infrared optical parametric oscillator | |
| RU76509U1 (en) | LASER WITH OPTICAL PARAMETRIC GENERATOR | |
| CN110277719B (en) | Terahertz parameter generator | |
| CN106451051B (en) | 2 μm of tunable laser of standing-wave cavity optical parametric oscillator are constituted based on body grating |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant |