CN102412496B - Non-linear optical difference frequency technology-based terahertz wave radiation source - Google Patents
Non-linear optical difference frequency technology-based terahertz wave radiation source Download PDFInfo
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- CN102412496B CN102412496B CN2011103241203A CN201110324120A CN102412496B CN 102412496 B CN102412496 B CN 102412496B CN 2011103241203 A CN2011103241203 A CN 2011103241203A CN 201110324120 A CN201110324120 A CN 201110324120A CN 102412496 B CN102412496 B CN 102412496B
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Abstract
The invention discloses a non-linear optical difference frequency technology-based terahertz wave radiation source, which comprises a pump source, a telescope shrinkage system, a holophote, a MgO:LiNbO3 crystal, a rotary platform, an output mirror, three reflecting mirrors, a half-wave plate, a polarization spectroscope, an attenuating sheet, a difference frequency crystal and a filter plate, wherein the holophote and the output mirror construct a resonant cavity, and are arranged on the rotary platform; and the MgO:LiNbO3 crystal is arranged in the resonant cavity. In the invention, continuous tunable output of Stocks laser is realized by rotating the rotary platform, the Stocks laser is combined with pump light emitted by the pump source in the polarization spectroscope to obtain a dual-wavelength difference frequency pump source for generating dry narrowband and continuously-adjustable terahertz waves in a non-linear difference frequency crystal. The terahertz wave radiation source is a full-solid terahertz wave coherent radiation source which has a small size and a compact structure and is continuously tunable, and can be applied to the terahertz photoelectron technical fields of medical diagnosis, fine spectrum analysis, biomedical imaging, terahertz communication and the like.
Description
Technical field
The present invention relates to THz wave optoelectronics technical field, be specifically related to a kind of terahertz radiation source based on nonlinear optics difference frequency technology.
Background technology
THz wave is meant the electromagnetic wave (1THz=10 of frequency in the 0.1-10THz scope
12Hz), its wave band is in electromagnetic spectrum between millimeter wave and the far red light.Because material includes abundant physics and chemical information in emission, reflection and the transmitted spectrum of THz wave frequency range; And terahertz radiation has characteristics such as low energy property, high-penetrability; So it is in basic research fields such as physics, chemistry, astronomy, life science and medical sciences, and application study fields such as safety inspection, medical imaging, environmental monitoring, Food Inspection, radio astronomy, satellite communication and weapon guidance all have huge scientific research value and wide application prospect.Yet the generation of THz wave is compared still with very ripe microwave, optical technology with Detection Techniques and is very fallen behind, and this just becomes one of main factor of the modern Terahertz Technology development of restriction.Therefore, develop the terahertz radiation source of function admirable, become researcher target of pursuing and the practical problem that presses for solution.
The method that produces terahertz radiation has a variety of; And the terahertz radiation that utilizes nonlinear optics difference frequency technology to produce; Have plurality of advantages such as high coherence, monochromaticjty are good, continuously adjustable wide ranges; But and the running of experimental facilities compact conformation, room temperature simple to operate, therefore in recent ten years extremely people attract attention, become the focus of studying in the world gradually.At present; Domestic and international many researchers produce the THz wave technology to difference frequency and have carried out a large amount of innovations, pilot study work; Realized the tuning range of broad; Peak power even reached a kilowatt magnitude, and utilize them successfully to carry out a lot of action oriented research as radiation source has proved that fully utilizing the difference frequency method to produce THz wave is a kind of effective, THz wave generating technique that practicality is very strong.
Utilize nonlinear optics difference frequency method to produce one of key problem in technology of continuously adjustable THz wave, must at first obtain exactly peak power height, narrow linewidth, wavelength interval suitable, at certain limit continuously-tuning dual wavelength difference frequency pump light.The method of at present common generation dual wavelength mainly contains two big types:
(1) utilize laser technology to produce dual wavelength difference frequency pump light.For example, use two single modes CO of output continuously
2Laser is as the difference frequency pumping source; Utilize a tunable dye laser to obtain dual wavelength output; Dual wavelength difference frequency pump light is formed in the tunable output that the optical parametric oscillator based on bbo crystal (OPO) that utilizes the output of Nd:YAG laser fundamental frequency and this laser frequency tripling to export pumping is produced.Shortcomings such as these methods that obtain dual wavelength exist such as difference frequency pump arrangement volume big, and main experimental facilities is expensive, and the wavelength tuning mode is complicated, and is not easy to operate.
(2) utilize nonlinear optics parametric oscillation technology to produce dual wavelength difference frequency pump light.For example, utilize the PPLN crystal of binary cycle cascade to form OPO,, obtain the tuning output of dual wavelength through changing crystal temperature effect or selecting suitable polarization cycle; The optical parametric oscillator that utilizes two blocks of nonlinear crystals to be composed in series obtains dual wavelength output etc. through the angle tuning technology.This type produces the method for dual wavelength difference frequency pump light; The dual wavelength tuning manner is complicated, tuned speed is slow; Need the polylith nonlinear crystal to realize the dual wavelength parametric oscillation, increased tuning difficulty, and the selection of pump light has received the restriction of nonlinear crystal phase-matching condition.
In general,, incident pumping light wavelength is selected there is not strict restriction, absorb only otherwise by crystal and get final product for common Raman scattering phenomenon.With the Stokes light scattering is example, and when pump light incided in the nonlinear crystal, the frequency displacement of the stokes light of generation was a fixed value, was the energy level difference between two energy levels.In this stimulated scattering process, only comprise the third-order non-linear effect.Yet, when polar crystal (like LiNbO
3Crystal) cuts according to certain mode; And when disposing according to the forward direction Raman scattering, the lattice vibration mould of crystal will become polariton this moment, and the pairing vibration frequency of lattice vibration mould also will have certain angular dispersion characteristic; That is to say; The stokes light that produce this moment will have certain space angle dispersion characteristics, and polariton at this moment will have the part electromagnetic property, and not exclusively be the characteristic of phonon.In this stimulated scattering process, comprise second order and third-order nonlinear optical effect simultaneously.Based on this principle, if being added a resonant cavity, stokes light makes its stimulated oscillation, the angle through continuously changing very much resonant cavity and pump light in the small angle range so, the relevant stokes light output that will produce width, continuously adjustable at one.In this tuning process, the stokes light of pump light, vibration and the wave vector of polariton satisfy the non-colinear phase-matching condition.If with the continuously adjustable stokes light that produces and pump light as dual wavelength difference frequency pumping source, so through choosing suitable difference frequency crystal, just can difference frequency generation continuously adjustable, the terahertz radiation of the arrowband that is concerned with.
Summary of the invention
Defective or deficiency to the prior art existence; The objective of the invention is to; Provide that a kind of volume is little, compact conformation, simple to operate, to produce difference frequency dual wavelength method easy, reliable, the room temperature running can produce the terahertz radiation source of continuously adjustable, relevant narrow band terahertz band wave radiation.
In order to realize above-mentioned task, the present invention adopts following technical solution:
A kind of terahertz radiation source based on nonlinear optics difference frequency technology is characterized in that, comprises pumping source, telescopic system, completely reflecting mirror, MgO:LiNbO
3Crystal, rotation platform, outgoing mirror, three speculums, half-wave plate, polarization spectroscope, attenuator, difference frequency crystal and filter plates; Wherein:
Completely reflecting mirror and outgoing mirror constitute resonant cavity, place on the rotation platform; MgO:LiNbO
3Crystal is arranged in the resonant cavity;
, telescopic system is incident to resonant cavity from the pump light of pumping source outgoing after contracting bundle, excitation MgO:LiNbO
3Crystal produces the stokes light of vibration in resonant cavity.Pass through MgO:LiNbO
3The pump light of crystal is incident to polarization splitting prism through first speculum, attenuator; From the stokes light of outgoing mirror outgoing through second, third mirror reflects, make the Stokes light polarization direction that 90 ° of deflections take place through half-wave plate after, be incident to polarization splitting prism; Pump light and stokes light close bundle in polarization splitting prism after, be incident to and carry out difference frequency in the nonlinear difference crystal, and obtain THz wave with filter plate filtering dual wavelength difference frequency pump light.
The present invention compares with the common terahertz emission source based on dual wavelength difference frequency generation THz wave, has the following advantages:
(1) method of acquisition dual wavelength is simple, only needs a nonlinear crystal just can obtain the relevant difference frequency pump light of the continuously adjustable close with the pump light wavelength, that energy is higher, makes that the single unit system volume is little, simple and compact for structure, flexible operation;
(2) owing to produce the forward direction Raman scattering process that the mechanism of dual wavelength is based on nonlinear crystal, thus the wavelength of pumping source output choose comparatively random, only otherwise by MgO:LiNbO
3Crystal absorbs and gets final product, and has avoided the restriction of birefringent phase matching condition, has improved the flexibility that obtains dual wavelength difference frequency pumping source.
Description of drawings
Fig. 1 is overall structure sketch map and the three ripple non-colinear phase matched sketch mapes based on the technological terahertz radiation source of nonlinear optics difference frequency of the present invention;
Fig. 2 is most circular outgoing mirror sketch mapes.
Label among the figure representes respectively, 1, pumping source, 2, the telescope beam system that contracts, 3, the round mostly total reflective mirror of resonant cavity, 4, pump light, 5, stokes light, 6, MgO:LiNbO
3Crystal, 7, rotation platform, 8, most circular outgoing mirror, 9, first speculum, 10, second speculum, the 11, the 3rd speculum, 12, half-wave plate, 13, polarization spectroscope, 14, attenuator, 15, the nonlinear difference crystal, 16, filter plate.
Below in conjunction with accompanying drawing and embodiment the present invention is further detailed.
Embodiment
The overall structure sketch map of Fig. 1 (a) is that present embodiment provides a kind of terahertz radiation source based on nonlinear optics difference frequency technology comprises pumping source 1, telescope contract beam system 2, completely reflecting mirror 3, MgO:LiNbO
3Crystal 6, rotation platform 7, outgoing mirror 8, three speculums (9,10,11), half-wave plate 12, polarization spectroscope 13, attenuator 14, nonlinear difference crystal 15 and filter plates 16;
Completely reflecting mirror 3, MgO:LiNbO
3Crystal 6 and outgoing mirror 8 constitute resonant cavity, place on the rotation platform 7 MgO:LiNbO
3Crystal 6 is arranged in the resonant cavity;
In the present embodiment, utilize electric-optically Q-switched Pulse Nd: fundamental frequency light (1064nm) output of YAG laser is as the pumping source 1 that produces dual wavelength, and the polarization direction of the pump light 4 of its ejaculation is parallel to operation material MgO:LiNbO
3The Z-direction of crystal 6 (doping content is 5%mol).
Utilize the telescope beam system 2 that contracts to contract bundle from the pump light 4 of pumping source 1 outgoing to improve energy density, then along X-direction incident operation material MgO:LiNbO
3Crystal 6.MgO:LiNbO
3Crystal 6 cutting mode and be of a size of 60mm (X axle) * 10mm (Y axle) * 5mm (Z axle) the logical light face of two Y-Z is carried out optical polish, and plating centre wavelength is the 1070nm anti-reflection film.
Resonant cavity is placed on the rotation platform 7, and the resonant cavity chamber is long to be 160mm.Between pump light 4 and the resonant cavity chamber axle a less angle theta is arranged
ExtThe pump light 4 disposable MgO:LiNbO that pass through
3Crystal 6, and not through completely reflecting mirror 3 and outgoing mirror 8.Excite the stokes light 5 of generation between total reflective mirror 3 and outgoing mirror 8, to vibrate, its polarization direction is identical with the polarization direction of pump light 4.Completely reflecting mirror 3 plating centre wavelengths are the film that is all-trans of 1070nm.Outgoing mirror 8 plating centre wavelengths are the part transmitance film of 1070nm, and transmitance is 5%.The shape of total reflective mirror 3 and outgoing mirror 8 is all most circles (as shown in Figure 2), and diameter is 20mm, and its chord length is between 15mm-20mm.Adopt circular mostly outgoing mirrors, be convenient to pump light 4 on the string limit of adjacent most circular outgoing mirrors 8 through the time, the stokes light 5 of vibration can effectively separate with pump light 4.
Because MgO:LiNbO
3The basic principle of the continuously adjustable stokes light 5 that crystal 6 produces in resonant cavity is based on crystal A
1Symmetry lattice vibration mould (ω
TO≈ 250cm
-1) forward direction Raman scattering process, so stokes light 5 has certain space angle dispersion characteristics in Y direction, and pump light wave vector k
Pump, the vibration stokes light wave vector k
StokesWith polariton wave vector k
PolaritonSatisfy non-colinear phase-matching condition (shown in Fig. 1 (b)).Therefore, make resonant cavity chamber axle and pump light 4 angle theta when rotating rotation platform 7
ExtWhen between 0.4 °-3 °, changing continuously, the stokes light 5 of being excited of generation will change between 1067nm-1076nm continuously.
Pass through MgO:LiNbO
3The pump light 4 of crystal 6 through first speculum 9 after, earlier carry out energy attenuation through attenuator 14, be incident to polarization splitting prism 13 then, produce a branch of difference frequency pump light of THz wave as difference frequency.Stokes light 5 from the resonant cavity outgoing; After second, third speculum (10,11) reflection; Through 1/2nd wave plates 12, make the polarization direction of stokes light that 90 ° of deflections take place, be incident to polarization splitting prism 13 then; And close bundle with pump light 4, produce another bundle difference frequency pump light of THz wave as difference frequency.At this moment, the polarization direction of pump light 4 and stokes light 5 is orthogonal, is incident to nonlinear difference crystal GaSe or ZnGeP
2In the crystal 15, utilize II class phase-matching technique conllinear difference frequency to produce terahertz radiation.Utilize filter plate 16 filterings two bundle difference frequency pump lights, obtain terahertz radiation.Filter plate 16 tilts to place, and avoids the former road of two bundle difference frequency pump lights to return.
Rotate rotation platform 7 and make resonant cavity chamber axle and pump light angle theta
ExtBetween 0.4 °-3 °, change continuously, the stokes light 5 of being excited that produce this moment will change between 1064nm-1076nm continuously.At this moment, simultaneous tuning nonlinear difference crystal GaSe or ZnGeP
2The phase matched angle of crystal just can difference frequency produces the continuously adjustable terahertz radiation of 0.8-3.1THz.
Need to prove that the above-mentioned a kind of optimal way that is technical scheme of the present invention with embodiment the invention is not restricted to the foregoing description.Being to be understood that to realizing the present invention through the mode that provides instance, is not to qualification of the present invention, and those skilled in the art is on the technical scheme basis that the foregoing description provides, and interpolation of having done and equivalence replacement all belong to protection scope of the present invention.
Claims (4)
1. the terahertz radiation source based on nonlinear optics difference frequency technology is characterized in that, comprises pumping source (1), telescope contract beam system (2), completely reflecting mirror (3), MgO:LiNbO
3Crystal (6), rotation platform (7), outgoing mirror (8), three speculums (9,10,11), half-wave plate (12), polarization splitting prism (13), attenuator (14), nonlinear difference crystal (15) and filter plate (16); Wherein:
Completely reflecting mirror (3), MgO:LiNbO
3Crystal (6) and outgoing mirror (8) constitute resonant cavity, place on the rotation platform (7) MgO:LiNbO
3Crystal (6) is arranged in the resonant cavity; Completely reflecting mirror of said resonant cavity (3) and outgoing mirror (8) are circular mostly;
Contract and be incident in the resonant cavity excitation MgO:LiNbO behind the bundle through the telescope beam system (2) that contracts from the pump light (4) of pumping source (1) outgoing
3Crystal (6) produces the stokes light (5) of vibration in resonant cavity; Pass through MgO:LiNbO
3The pump light (4) of crystal (6) is incident to polarization splitting prism (13) through first speculum (9), attenuator (14); From the stokes light (5) of outgoing mirror (8) outgoing through second, third speculum (10,11) reflection, make stokes light (5) polarization direction that 90o deflection take place through half-wave plate (12) after, be incident to polarization splitting prism (13); Pump light (4) and stokes light (5) close the bundle back as dual wavelength difference frequency pump light in polarization splitting prism (13); Be incident in the nonlinear difference crystal (15) and carry out difference frequency, and obtain THz wave with filter plate (16) filtering dual wavelength difference frequency pump light.
2. the terahertz radiation source based on nonlinear optics difference frequency technology as claimed in claim 1 is characterized in that described pumping source (1) is a pulse laser, and its wavelength does not limit, otherwise be MgO:LiNbO
3Crystal (6) absorbs and promptly meets the demands.
3. the terahertz radiation source based on nonlinear optics difference frequency technology as claimed in claim 1 is characterized in that described MgO:LiNbO
3The cutting mode of crystal (6) is X-Y-Z, and logical light face is an X-Y plane, and on X-Y plane, plates anti-reflection film.
4. the terahertz radiation source based on nonlinear optics difference frequency technology as claimed in claim 1 is characterized in that said nonlinear difference crystal (15) is GaSe or ZnGeP
2Crystal.
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| CN104037595B (en) * | 2014-06-20 | 2017-05-24 | 华北水利水电大学 | Terahertz wave amplifier based on optical parametric effect |
| CN105048270A (en) * | 2015-07-13 | 2015-11-11 | 山东大学 | Laser amplifier based on lithium niobate crystals and application thereof |
| CN105261915A (en) * | 2015-11-17 | 2016-01-20 | 天津大学 | Compact type optical difference-frequency THz source |
| CN105827356B (en) * | 2016-05-25 | 2018-10-23 | 深圳市太赫兹科技创新研究院有限公司 | A kind of two-way THz wave communication system |
| CN106654837B (en) * | 2016-11-25 | 2023-05-05 | 中国科学院上海技术物理研究所 | Seed light injection high-power terahertz difference frequency source system |
| CN106374323B (en) * | 2016-11-25 | 2023-05-05 | 中国科学院上海技术物理研究所 | Laser up-conversion terahertz difference frequency source detection system |
| CN107017543A (en) * | 2017-06-15 | 2017-08-04 | 江西师范大学 | The device and method of tunable THz wave is produced in microcavity |
| CN110673352B (en) * | 2018-07-02 | 2024-08-30 | 天津大学 | Terahertz structure light modulation device for super-resolution imaging |
| CN110137780B (en) * | 2019-05-09 | 2021-02-26 | 华北水利水电大学 | Cascade terahertz wave parametric oscillator |
| CN110768088A (en) * | 2019-10-31 | 2020-02-07 | 郑州轻工业学院 | Tunable terahertz wave parameter source with self-frequency-selective seed laser injection |
| CN110783801B (en) * | 2019-10-31 | 2021-07-27 | 郑州轻工业学院 | THz wave parameter source for multi-wavelength pulse delay output |
| CN112202036A (en) * | 2020-09-15 | 2021-01-08 | 中国科学院沈阳自动化研究所 | self-Raman laser difference frequency terahertz radiation device |
| CN112540416B (en) * | 2020-12-01 | 2022-01-28 | 中国工程物理研究院激光聚变研究中心 | Terahertz pulse up-conversion detection method and system |
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| JP2004108905A (en) * | 2002-09-18 | 2004-04-08 | Inst Of Physical & Chemical Res | Difference imaging method using terahertz wave and device |
| CN101614930A (en) * | 2009-07-21 | 2009-12-30 | 华中科技大学 | A kind of frequency tuning method for TeraHertz parameter oscillator |
| CN101609243B (en) * | 2009-07-21 | 2010-12-08 | 华中科技大学 | Terahertz-wave parametric oscillator based on corner-cube prism resonant cavity |
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