CN115390336B - Optical difference frequency terahertz wave generation device and method based on lithium niobate crystal - Google Patents
Optical difference frequency terahertz wave generation device and method based on lithium niobate crystal Download PDFInfo
- Publication number
- CN115390336B CN115390336B CN202211116405.2A CN202211116405A CN115390336B CN 115390336 B CN115390336 B CN 115390336B CN 202211116405 A CN202211116405 A CN 202211116405A CN 115390336 B CN115390336 B CN 115390336B
- Authority
- CN
- China
- Prior art keywords
- lithium niobate
- difference frequency
- niobate crystal
- terahertz wave
- crystal
- 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 116
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 title claims abstract description 79
- 230000003287 optical effect Effects 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 16
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 42
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 42
- 239000010703 silicon Substances 0.000 claims abstract description 42
- 229920002799 BoPET Polymers 0.000 claims abstract description 19
- 238000010521 absorption reaction Methods 0.000 claims abstract description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 230000000694 effects Effects 0.000 claims description 21
- 239000013307 optical fiber Substances 0.000 claims description 21
- 238000001035 drying Methods 0.000 claims description 3
- 238000007605 air drying Methods 0.000 abstract description 3
- 230000008878 coupling Effects 0.000 description 6
- 238000010168 coupling process Methods 0.000 description 6
- 238000005859 coupling reaction Methods 0.000 description 6
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000003993 interaction Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000005855 radiation Effects 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000001737 promoting effect Effects 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 229920000139 polyethylene terephthalate Polymers 0.000 description 2
- 239000005020 polyethylene terephthalate Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000000701 chemical imaging Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000009022 nonlinear effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920001225 polyester resin Polymers 0.000 description 1
- 239000004645 polyester resin Substances 0.000 description 1
- -1 polyethylene terephthalate Polymers 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 239000000126 substance Substances 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
-
- 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
- G02F1/3544—Particular phase matching techniques
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Landscapes
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Optics & Photonics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses an optical difference frequency terahertz wave generation device and method based on lithium niobate crystals, and relates to the technical field of terahertz wave generation. Comprising the following steps: the device comprises a light source module, a beam combining module and a difference frequency generating module. Two continuous lasers are obliquely incident into the lithium niobate crystal in parallel to realize non-collinear phase matching to generate terahertz waves. The two laser beams generate terahertz waves on the Y surface of the lithium niobate crystal, so that the absorption of the crystal to the terahertz waves is greatly reduced. And a layer of PET film is arranged between the lithium niobate crystal and the silicon prism, so that the influence of laser deviation on the difference frequency of two beams of light to the silicon prism is avoided. The air drying box is used for reducing the water vapor content in the air, so that the terahertz wave power is enhanced.
Description
Technical Field
The invention relates to the technical field of terahertz wave generation, in particular to an optical difference frequency terahertz wave generation device and method based on lithium niobate crystals.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
Terahertz technology is known as one of the ten technologies for changing the future world, and has very important academic and application values. The terahertz wave radiation source has unique and excellent characteristics of coherence, low energy, high penetrability and the like, stabilizes the realization of the high-energy terahertz light source, and fills a spectrum window between microwaves and infrared light. The power of the current terahertz source is approximately in the order of microwatts or even lower, and the background noise of the terahertz wave band in the environment is generally tens of microwatts, which is not beneficial to detection and application.
In the method for generating terahertz optical radiation by numerous solid photoelectric technologies, a terahertz time-domain system generated based on photoconductive and photo rectification effects caused by femtosecond ultrafast laser is mature, and can be used for carrying out rapid spectral imaging identification on various chemical explosives and biological macromolecular systems. As the method is a time domain conversion method, the application requirements of terahertz light in interplanetary transmission, terahertz communication and the like are not met. In recent years, a series of more satisfactory experimental results (such as that the pulse peak power is increased to the order of 100 mW) have been obtained by generating high-power, broadband and tunable terahertz light radiation through the stimulated polarization phonon parametric effect (parametric generation, parametric oscillation and parametric oscillation of injected seeds) of lithium niobate crystals. Based on the optical difference frequency principle, the high-power broadband coherent terahertz wave radiation is realized in the nonlinear optical crystal, and the device has the advantages of compact structure, simplicity in adjustment, no threshold limit, high output power, wide tuning band, room-temperature operation and the like.
The conventional nonlinear crystal used for generating terahertz waves at the difference frequency is: gaAs, gaP, gaSe and MgO, liNbO 3, but the crystals often have the problems of photorefractive effect, lower damage threshold and the like, and the physical and optical properties of the crystals can be greatly improved by doping modification of the crystals so as to obtain the difference frequency crystals with high nonlinear coefficients and high damage threshold. Besides the modification of the crystal, the confinement effect of the waveguide on the transmission wave is utilized to improve the terahertz wave beam quality, increase the nonlinear action length and reduce the transmission loss, and finally the difference frequency efficiency is improved. In addition, the generation efficiency of the terahertz waves is further improved by utilizing the phase matching of near infrared fundamental frequency light and terahertz difference frequency light in the crystal.
The current waveguide type lithium niobate difference frequency module mainly comprises a LiNbO 3 substrate, mgO doped lithium niobate crystals and a silicon prism. Two near infrared lights with similar wavelengths generate terahertz waves based on nonlinear difference frequency effect in the crystal, and are coupled out through a silicon prism with refractive index close to that of the crystal. The output terahertz wave has narrow linewidth of MHz magnitude and tuning precision, and meets the requirement of high-resolution terahertz spectrum measurement. However, in the interaction process of the near-infrared laser and the LiNbO 3 doped crystal, the refractive index of the crystal to the near-infrared light and the refractive index of the terahertz wave band are often quite different, so that the phase matching condition is difficult to meet in the interaction process of the near-infrared laser and the crystal, and the conversion of energy from near-infrared pumping light to the terahertz wave is restricted to a great extent.
The existing waveguide type lithium niobate crystal difference frequency module still has a plurality of defects although the difference frequency crystal is improved by doping. Firstly, the lithium niobate crystal has strong absorption to terahertz waves, especially high-frequency terahertz waves, the absorption effect is more obvious, and the improvement of terahertz power and the output of broadband terahertz waves are influenced. And secondly, under the irradiation of strong laser, the lithium niobate crystal waveguide is easy to emit light and damage, so that the damage resistance threshold is low, and the thermal effect is sensitive, so that the power of the laser cannot be improved, and the high power output of terahertz waves at room temperature is further influenced. Light then easily enters a medium of large refractive index from a medium of small refractive index (because of a larger range of angles of incidence), but conversely is not easy (because of a smaller range of angles of incidence), so that light energy is generally easily concentrated into a medium of large refractive index. In the near infrared band, the refractive index (about 3.5) of silicon is higher than that of lithium niobate (about 2.2), so that when a silicon prism is directly placed on a lithium niobate crystal to lead out terahertz, near infrared light is easily deviated from the lithium niobate crystal, and the difference frequency effect of two beams of light is influenced. Finally, remote sensing and spectroscopic analysis of long-range broadband terahertz waves are difficult to achieve due to the strong absorption of terahertz waves by water vapor in the air.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide an optical difference frequency terahertz wave generating device and method based on lithium niobate crystals, which are used for realizing non-collinear phase matching to generate terahertz waves by parallelly and obliquely incident two continuous lasers into the lithium niobate crystals, so that the technical problem that the refractive index of the crystals of a waveguide type lithium niobate crystal difference frequency module for near infrared light and the refractive index of terahertz wave bands are greatly different is solved, and a terahertz source with high efficiency and stable operation is manufactured.
In order to achieve the above object, the present invention is realized by the following technical scheme:
The first aspect of the present disclosure provides an optical difference frequency terahertz wave generating device based on a lithium niobate crystal, comprising: the device comprises a light source module, a beam combination module and a difference frequency generation module, wherein the light source module is used for emitting two beams of laser, and the beam combination module is used for combining the two beams of laser into one beam and parallelly incident the two beams of laser to the difference frequency generation module; the difference frequency generation module comprises a lithium niobate crystal, a silicon prism and a rotary table, wherein the lithium niobate crystal is cuboid and is placed on the rotary table, the silicon prism is known above the lithium niobate crystal, and a layer of PET film is placed between the lithium niobate crystal and the silicon prism.
Further, the light source module comprises a fixed wavelength laser, a tunable laser, a first optical fiber amplifier and a second optical fiber amplifier; the fixed wavelength laser is connected with the first optical fiber amplifier as a light source of nonlinear crystal optical difference frequency, and the tunable laser is connected with the second optical fiber amplifier as a light source of another nonlinear crystal optical difference frequency.
Further, the first and second optical fiber amplifiers amplify the power of the two laser beams to W level respectively.
Further, the beam combining module comprises a beam combining lens and a convex lens, wherein the beam combining lens is arranged in front of the convex lens, and the light source is focused by the convex lens to shrink the beam after combining the light rays by the beam combining lens.
Further, lithium niobate crystals are doped with 5mol% mgo as a medium for optical difference frequency generation.
Further, the rotary table can rotate at multiple angles and is used for changing the angle between the signal light and the pump light, realizing non-collinear phase matching and generating terahertz waves with different frequencies.
Further, a drying box is arranged outside the difference frequency generation module and used for reducing the water vapor content in the air, so that the absorption of the water vapor to the terahertz waves is reduced.
Further, the device also comprises a detector, wherein the detector is positioned in front of the hypotenuse of the silicon prism in the difference frequency generation module and is used for detecting the generated terahertz waves.
Further, in order to avoid affecting the output of the terahertz wave, the thickness of the PET film is smaller than the wavelength of the terahertz wave.
The second aspect of the present disclosure provides a method for generating an optical difference frequency terahertz wave based on a lithium niobate crystal, comprising the steps of:
the two laser beams output by the fixed wavelength laser and the tunable laser reach W level through the optical fiber amplifier, the two laser beams amplified by the power are combined into one beam through the beam combining lens, then focused and condensed to the level of about mu m in diameter through the convex lens, and the two laser beams are parallelly incident into the MgO-doped lithium niobate crystal to generate the terahertz wave under the difference frequency effect, and finally received by the detector.
The beneficial effects of the embodiment of the invention are as follows:
According to the invention, two continuous lasers are obliquely incident into the lithium niobate crystal in parallel to realize non-collinear phase matching to generate terahertz waves. The two laser beams generate terahertz waves on the Y surface of the lithium niobate crystal, so that the absorption of the crystal to the terahertz waves is greatly reduced. The invention does not adopt the scheme of designing the waveguide, and avoids the problem of damaging the waveguide under high-power laser. A layer of PET (polyethylene terephthalate, commonly known as polyester resin) film is placed between the lithium niobate crystal and the silicon prism, so that the difference frequency effect of two beams of light is prevented from being influenced by laser deviation to the silicon prism. Because the water vapor has a strong absorption effect on the terahertz waves, the air drying box is adopted in the scheme of the invention to reduce the water vapor content in the air, thereby playing a role in enhancing the power of the terahertz waves.
In the present invention, a PET film of about 5 microns thick was placed between the silicon prism and the lithium niobate crystal. The silicon prism is used for promoting the coupling output of terahertz waves from the nonlinear crystal, and the refractive index of the silicon prism in a near infrared band is higher than that of lithium niobate, so that the near infrared light is easily focused to the silicon prism by directly placing the silicon prism on the lithium niobate crystal, and the difference frequency effect of two beams of light in the crystal is influenced. A PET film is placed between the silicon prism and the lithium niobate crystal, the problem can be solved, the refractive index of the PET film in the near infrared band is about 1.3, and the refractive index of the PET film in the near infrared band is lower than that of the lithium niobate crystal, so that the difference frequency effect of the two laser beams in the nonlinear crystal is prevented from being influenced by the aggregation deviation of the two laser beams to the silicon prism. And the thickness of the PET film is smaller than the wavelength of terahertz, and the coupling propagation of the generated terahertz wave to the silicon prism is not influenced.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a diagram of a conventional waveguide-type difference frequency module;
Fig. 2 is a schematic diagram of an optical difference frequency terahertz wave generating apparatus based on a lithium niobate crystal in a first embodiment of the present invention;
FIG. 3 is a schematic diagram of a non-collinear phase matching structure of a difference frequency generating module according to an embodiment of the present invention;
1, a fixed wavelength laser; 2. a tunable laser; 3. a first optical fiber amplifier; 4. a second optical fiber amplifier; 5. a beam combining lens; 6. a convex lens; 7. lithium niobate crystals; 8. a silicon prism; 9. a rotary table; 10. an air drying box; 11. a detector; 12. a PET film; a lithium niobate waveguide.
The specific embodiment is as follows:
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof;
the current waveguide type lithium niobate difference frequency module mainly comprises a LiNbO 3 substrate, mgO doped lithium niobate crystals and a silicon prism, as shown in figure 1. Two near infrared lights with similar wavelengths generate terahertz waves based on nonlinear difference frequency effect in the crystal, and are coupled out through a silicon prism with refractive index close to that of the crystal. The output terahertz wave has narrow linewidth of MHz magnitude and tuning precision, and meets the requirement of high-resolution terahertz spectrum measurement. In the interaction process of near-infrared laser and a LiNbO 3 doped crystal, the refractive index of the crystal to near-infrared light and the refractive index of the terahertz wave band are often quite different, so that the phase matching condition is difficult to meet in the interaction process of the near-infrared laser and the crystal, and the conversion of energy from near-infrared pumping light to terahertz waves is restricted to a great extent.
According to the traditional difference frequency module scheme of combining the waveguide type lithium niobate crystal with the silicon prism, terahertz waves are generated in the crystal instead of the surface, and the lithium niobate crystal has strong absorption to the terahertz waves, so that the power and the bandwidth of the terahertz waves are influenced. Secondly, the nonlinear efficiency of the scheme is low, the output power of the terahertz wave needs to be improved by enhancing the laser power, and when the laser power reaches the W level, the waveguide is easy to damage, and the generation and output of the terahertz wave are affected. And a silicon prism is directly placed on the waveguide of the lithium niobate crystal for coupling the output of terahertz waves, so that the effect of the waveguide of the lithium niobate crystal is affected. In the near infrared band, the refractive index of the silicon prism is higher than that of lithium niobate, so that near infrared light is easy to deviate from the waveguide when propagating in the waveguide, and the difference frequency effect of two near infrared light beams in the nonlinear crystal is influenced.
According to the invention, two continuous lasers are obliquely incident into the lithium niobate crystal in parallel to realize non-collinear phase matching to generate terahertz waves, so that the technical problem of a waveguide type lithium niobate crystal difference frequency module is well solved, and a terahertz source with high efficiency and stable operation is manufactured. Specific examples are as follows:
embodiment one:
An embodiment of the present disclosure provides an optical difference frequency terahertz wave generating device based on a lithium niobate crystal, as shown in fig. 2, including: the device comprises a light source module, a beam combination module and a difference frequency generation module, wherein the light source module is used for emitting two beams of laser, and the beam combination module is used for combining the two beams of laser into one beam and parallelly incident the two beams of laser to the difference frequency generation module; the difference frequency generating module comprises a lithium niobate crystal 7, a silicon prism 8 and a rotary table 9, as shown in fig. 3, the lithium niobate crystal 7 is a cuboid, and is placed on the rotary table 9, the silicon prism 8 is placed above the lithium niobate crystal 7, a layer of PET film 12 is placed between the lithium niobate crystal 7 and the silicon prism 8, and in order to avoid influencing the output of terahertz waves, the thickness of the PET film 12 is smaller than the wavelength of terahertz waves, and in this embodiment, the PET film 12 with the thickness of about 5 micrometers is used. The silicon prism 8 is used for promoting coupling out of terahertz waves from a nonlinear crystal, and the refractive index of the silicon prism 8 in a near infrared band is higher than that of lithium niobate, so that the direct placement of the silicon prism 8 on the lithium niobate crystal 7 easily focuses near infrared light to the silicon prism 8, and the difference frequency effect of two beams of light in the crystal is affected. The refractive index of the PET film 12 in the near infrared band is about 1.3, and a layer of PET film 12 is arranged between the silicon prism 8 and the lithium niobate crystal 7, so that the problem can be solved, and the thickness of the PET film 12 is smaller than the wavelength of terahertz, and the output of terahertz waves is not influenced.
As a further technical solution, the light source module comprises a fixed wavelength laser 1, a tunable laser 2, a first optical fiber amplifier 3 and a second optical fiber amplifier 4; the fixed wavelength laser 1 is used as a light source of nonlinear crystal optical difference frequency, and is used for emitting pump light, and is connected with the first optical fiber amplifier 3, the tunable laser 2 is used as a light source of another nonlinear crystal optical difference frequency, is used for emitting signal light, and is tunable in wavelength, and is used for generating tunable terahertz waves, and is connected with the second optical fiber amplifier 4. The first optical fiber amplifier and the second optical fiber amplifier amplify the power of the two laser beams to W level respectively, so that the difference frequency of the two laser beams in the nonlinear crystal is more favorable for generating terahertz waves with higher power.
As a further technical scheme, the beam combining module comprises a beam combining lens 5 and a convex lens 6, wherein the beam combining lens 5 is used for combining two laser beams into one beam, and is more beneficial to the generation of the difference frequency effect of the two laser beams in the crystal. The convex lens 6 is used for focusing and beam shrinking after the two laser beams are combined, and is more beneficial to the difference frequency effect after the light spot becomes smaller and meets the optimal efficiency coupling relation. The beam combining lens 5 is arranged in front of the convex lens 6, and the light source is focused and condensed through the convex lens 6 after the light beam combining lens 5 combines the light beams.
As a further technical scheme, the lithium niobate crystal 7 is used as a medium for generating optical difference frequency, and is doped with 5mol percent MgO, so that the physical and optical characteristics of the lithium niobate crystal 7 can be improved, the damage threshold of the lithium niobate crystal 7 is enhanced, and the lithium niobate crystal can bear stronger laser power irradiation. The lithium niobate crystal has dimensions of 5mm×65mm×6mm, and is optically polished on the incident surface of the laser. And a silicon prism 8 for promoting coupling out of the terahertz wave from the nonlinear crystal.
The silicon prism is in the shape of a right-angle triangular prism, two right-angle sides are 55mm, the thickness is 6mm, a PET film is placed on the lithium niobate crystal, and the silicon prism is placed on the PET film. The rotary table 9 can rotate at multiple angles, and is used for changing the angle between the signal light and the pump light, realizing non-collinear phase matching and generating terahertz waves with different frequencies. The difference frequency generating module is provided with a drying box 10 outside for reducing the water vapor content in the air, thereby reducing the absorption of the water vapor to the terahertz waves.
As a further technical scheme, the device further comprises a detector 11, wherein the detector 11 is positioned in front of the hypotenuse of the silicon prism in the difference frequency generation module and is used for detecting the generated terahertz wave.
As shown in FIG. 3, a schematic diagram of the two laser lithium niobate crystals realizing non-collinear phase matching is that pump light and signal light are mutually parallel and incident into the crystals and form a certain included angle with the Y surface of the crystals, about 90% of the light will be reflected after the two laser light strikes the Y surface of the crystals, at this time, the reflected signal light and the unreflected pump light form a phase matching angle θ, the formula is expressed as
In the formula, n p、ns、nTHz is the refractive index of the pump light, the signal light and the terahertz wave in the lithium niobate crystal, and omega p、ωs、ωTHz is the angular frequency of the pump light, the signal light and the terahertz wave. In this embodiment, the incidence angles of the pump light and the signal light with respect to the nonlinear crystal Y surface are half of the phase matching angle. The incidence angle of the two beams of light in the nonlinear crystal can be changed through the rotary table, the terahertz wave frequency generated by the difference frequency can also be changed due to the change of the phase matching angle, and the higher the generated terahertz wave frequency is when the incidence angle is smaller. The area of the reflected signal light and the non-reflected pumping light, which generates terahertz, is positioned near the surface of the nonlinear crystal, so that the absorption of the crystal to terahertz waves, particularly high-frequency terahertz waves, is greatly reduced, and the tuning range of the terahertz waves is increased.
Embodiment two:
the second embodiment of the disclosure provides a method for generating an optical difference frequency terahertz wave based on a lithium niobate crystal, which comprises the following steps:
the two laser beams output by the fixed wavelength laser and the tunable laser reach W level through the optical fiber amplifier, the two laser beams amplified by the power are combined into one beam through the beam combining lens, then focused and condensed to the level of about mu m in diameter through the convex lens, and the two laser beams are parallelly incident into the MgO-doped lithium niobate crystal to generate the terahertz wave under the difference frequency effect, and finally received by the detector.
The steps involved in the second embodiment correspond to those of the first embodiment of the method, and the detailed description of the second embodiment can be found in the related description section of the first embodiment.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
Claims (7)
1. An optical difference frequency terahertz wave generating device based on lithium niobate crystal, characterized by comprising: the device comprises a light source module, a beam combination module and a difference frequency generation module, wherein the light source module is used for emitting two beams of laser, and comprises a fixed wavelength laser, a tunable laser, a first optical fiber amplifier and a second optical fiber amplifier; the tunable laser is connected with the second optical fiber amplifier as the light source of the optical difference frequency of the other nonlinear crystal; the first optical fiber amplifier and the second optical fiber amplifier amplify the power of two laser beams to W level respectively; the beam combining module is used for combining two laser beams into one beam and parallelly incident the two beams to the difference frequency generating module; the difference frequency generation module comprises a lithium niobate crystal, a silicon prism and a rotary table, wherein the lithium niobate crystal is cuboid and is placed on the rotary table, the silicon prism is placed above the lithium niobate crystal, and a layer of PET film is placed between the lithium niobate crystal and the silicon prism, so that the output of terahertz waves is prevented from being influenced, and the thickness of the PET film is smaller than the wavelength of terahertz waves.
2. The lithium niobate crystal-based optical difference frequency terahertz wave generating device of claim 1, wherein the beam combining module comprises a beam combining lens and a convex lens, the beam combining lens is arranged in front of the convex lens, and the light source is focused by the convex lens after combining light rays by the beam combining lens.
3. The lithium niobate crystal-based optical difference frequency terahertz wave generating apparatus according to claim 1, wherein the lithium niobate crystal is doped with 5 mol% MgO as a medium for optical difference frequency generation.
4. The lithium niobate crystal-based optical difference frequency terahertz wave generating apparatus of claim 1, wherein the turntable is rotatable at multiple angles for changing an angle between the signal light and the pump light, realizing non-collinear phase matching, and generating terahertz waves of different frequencies.
5. The lithium niobate crystal-based optical difference frequency terahertz wave generating device of claim 1, wherein a drying box is arranged outside the difference frequency generating module for reducing the water vapor content in the air, thereby reducing the absorption of the water vapor to the terahertz wave.
6. The lithium niobate crystal-based optical difference frequency terahertz wave generating apparatus according to claim 1, further comprising a detector located in front of the hypotenuse of the silicon prism in the difference frequency generating module for detecting the generated terahertz wave.
7. The optical difference frequency terahertz wave generation method based on the lithium niobate crystal, which adopts the optical difference frequency terahertz wave generation device based on the lithium niobate crystal as claimed in claim 1, is characterized by comprising the following steps:
The two laser beams output by the fixed wavelength laser and the tunable laser reach W level through the optical fiber amplifier, the two laser beams amplified by the power are combined into one beam through the beam combining lens, then focused and condensed to the diameter of mu m level through the convex lens, the two laser beams are parallelly incident into the MgO-doped lithium niobate crystal to generate the terahertz wave under the difference frequency effect, and finally the terahertz wave is received by the detector.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211116405.2A CN115390336B (en) | 2022-09-14 | 2022-09-14 | Optical difference frequency terahertz wave generation device and method based on lithium niobate crystal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211116405.2A CN115390336B (en) | 2022-09-14 | 2022-09-14 | Optical difference frequency terahertz wave generation device and method based on lithium niobate crystal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN115390336A CN115390336A (en) | 2022-11-25 |
| CN115390336B true CN115390336B (en) | 2024-05-24 |
Family
ID=84126689
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211116405.2A Active CN115390336B (en) | 2022-09-14 | 2022-09-14 | Optical difference frequency terahertz wave generation device and method based on lithium niobate crystal |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115390336B (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101592845A (en) * | 2009-07-01 | 2009-12-02 | 天津大学 | Dual-wavelength tunable inner cavity tera-hertz parametric oscillator and using method thereof |
| CN102386549A (en) * | 2011-10-10 | 2012-03-21 | 天津大学 | Tunable terahertz radiation source based on difference frequency cherenkov effect and modulation method |
| CN105637411A (en) * | 2013-10-09 | 2016-06-01 | 佳能株式会社 | Terahertz wave generating element and terahertz wave detecting element |
| CN106019765A (en) * | 2016-07-31 | 2016-10-12 | 山东大学 | Terahertz parameter source coupling structure and working method thereof |
| CN209281121U (en) * | 2019-01-21 | 2019-08-20 | 南京先进激光技术研究院 | A kind of optical difference frequency Terahertz generating means based on Distributed Feedback Laser |
-
2022
- 2022-09-14 CN CN202211116405.2A patent/CN115390336B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101592845A (en) * | 2009-07-01 | 2009-12-02 | 天津大学 | Dual-wavelength tunable inner cavity tera-hertz parametric oscillator and using method thereof |
| CN102386549A (en) * | 2011-10-10 | 2012-03-21 | 天津大学 | Tunable terahertz radiation source based on difference frequency cherenkov effect and modulation method |
| CN105637411A (en) * | 2013-10-09 | 2016-06-01 | 佳能株式会社 | Terahertz wave generating element and terahertz wave detecting element |
| CN106019765A (en) * | 2016-07-31 | 2016-10-12 | 山东大学 | Terahertz parameter source coupling structure and working method thereof |
| CN209281121U (en) * | 2019-01-21 | 2019-08-20 | 南京先进激光技术研究院 | A kind of optical difference frequency Terahertz generating means based on Distributed Feedback Laser |
Non-Patent Citations (2)
| Title |
|---|
| First principles terahertz spectroscopy of molecular crystals: the crucial role of periodic boundary conditions benchmarked with experimental l-ascorbic acid spectra;Ying Wang 等;Physical chemistry chemical physics : PCCP;20230403;全文 * |
| Tunable Terahertz-Wave Parametric Oscillators Using LiNbO3 and MgO: LiNbO3 Crystals;Jun-ichi Shikata 等;IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES;20000430;第48卷(第4期);全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN115390336A (en) | 2022-11-25 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Bodrov et al. | Highly efficient optical-to-terahertz conversion in a sandwich structure with LiNbO 3 core | |
| JP2002072269A (en) | Method and device for generating terahertz wave | |
| WO2006062073A1 (en) | Method and device for generating terahertz wave | |
| WO2017181310A1 (en) | Apparatus and method for strengthening terahertz signal on the basis of hollow-core metal waveguide optical fiber | |
| CN107425407B (en) | Tunable blue light radiation source based on inner cavity self-frequency multiplication and implementation method | |
| CN104503183A (en) | Self-frequency-conversion terahertz parametric oscillator | |
| CN110895239B (en) | Device and method for measuring excited state absorption heat load in laser gain crystal | |
| CN105159008B (en) | The application of niobic acid gallium lanthanum crystal device for non-linear optical of infrared band as in | |
| CN115390336B (en) | Optical difference frequency terahertz wave generation device and method based on lithium niobate crystal | |
| CN106654837B (en) | Seed light injection high-power terahertz difference frequency source system | |
| Wang et al. | Wide-tunable mid infrared intra-cavity optical parametric oscillator based on multi-period MgO: PPLN | |
| CN106159643B (en) | A kind of terahertz-wave parametric oscillator based on cascade parametric effect | |
| CN102331650B (en) | Right-angle prism resonance cavity-based broadband terahertz wave radiation source | |
| CN110768088A (en) | Tunable terahertz wave parameter source with self-frequency-selective seed laser injection | |
| CN116937312A (en) | Saturable absorber device based on structure dielectric constant near-zero film, preparation method and application | |
| CN106410582A (en) | Shared chamber light parameter oscillator of human-eye safe wave-band continuous output | |
| CN105790045A (en) | High-energy few-cycle ultra-high-signal to noise ratio femtosecond seed pulse generation device | |
| CN108767628A (en) | The method and apparatus for generating Terahertz based on multicycle structure PPLN cascade difference frequency | |
| CN213602178U (en) | Parameter oscillation optical system | |
| CN208806465U (en) | A kind of nonlinear crystal based on multicycle structure obtains the device of THz source | |
| Li et al. | Intracavity THz polariton source using a shallow-bounce configuration | |
| Xu et al. | Widely-tuned longwave mid-infrared optical parametric oscillator based on BaGa4Se7 crystal | |
| CN103259169B (en) | Difference frequency terahertz wave optical fiber laser | |
| CN112670810A (en) | Wide tuning 3-micron waveband intermediate infrared laser of cascade pump | |
| CN111641097A (en) | Waveguide type electro-optic modulation terahertz wave generator based on lithium niobate crystal |
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 | ||
| GR01 | Patent grant |