CN102255223B - Circular modulating frequency-shifting nonlinear frequency-differing type broadband tuning terahertz wave generator - Google Patents
Circular modulating frequency-shifting nonlinear frequency-differing type broadband tuning terahertz wave generator Download PDFInfo
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Abstract
The invention provides a circular modulating frequency-shifting nonlinear frequency-differing type broadband tuning terahertz wave generator, which comprises a laser device, a first circulator, a light beam splitter, a circular frequency-shifting link based on modulator frequency shifting, a first light beam combiner, an optoisolator, a nonlinear element and a terahertz filter plate. After passing through the first circulator, light outputted by the laser device is divided into a first light path and a second light path by the light beam splitter; the first light path is a reference light; a circular frequency-shifting light is generated after the second light path is inputted to the circular frequency-shifting link; and after being combined by the first light beam combiner, the reference light and the circular frequency-shifting light are subject to frequency differing in the nonlinear element by the optoisolator and finally are filtered by the terahertz filter plate, thereby radiating out a coherent terahertz wave. The circular modulating frequency-shifting nonlinear frequency-differing type broadband tuning terahertz wave generator provided by the invention has the advantages that the volume is small, the broadband tuning terahertz wave generator can be easily integrated because of few optical elements, the tuning scope is wide, the tuning efficiency is high, and the terahertz wave generating efficiency is high.
Description
Technical field
The present invention relates to the wide-band tuning THz wave device that a kind of difference frequency mode produces, relate in particular to a kind of wide-band tuning THz wave light source based on modulator shift frequency, circulation shift frequency and difference frequency principle.
Background technology
Terahertz (THz, 1THz=10
12Hz) ripple is meant that operating frequency is in the electromagnetic wave in 0.1～10THz scope.Why THz wave can cause the research interest that the scientific worker is dense; It is not electromagnetic radiation rarely known by the people because it is mysterious; Mainly be that these unique character have been given Terahertz science application prospects just because it has the character of a lot of uniquenesses.The character of the uniqueness of THz wave mainly shows: perspectivity, fail safe, spectral resolving power.Terahertz emission has good penetrability to a lot of dielectric materials and nonpolar liquid; Therefore can carry out perspective imaging to nontransparent object; In addition since the wavelength of Terahertz greater than the yardstick of suspension smoke particle in the air; The Rayleigh scattering loss is minimum, so can penetrate flue dust and thick fog preferably, is the perfect light source that forms images in fire rescue or the travel fatigue environmental monitoring.Compare the photon energy that X ray has kiloelectron-volt, the photon energy of terahertz emission has only the milli electronvolt, and this energy is all lower than the bond energy of various chemical bonds; So ionization reaction can not take place; Promptly can not destroy molecular structure of compounds, therefore can be applied to places such as safety check and biological detection, this is the embodiment of the fail safe of Terahertz; A large amount of molecules; Especially the transition of the vibration of organic molecule and rotation spectrum all is in the Terahertz spectral range, thereby can utilize the spectral resolution characteristic to realize the analysis of object appearance and constituent.
Because THz wave has above-mentioned important application prospects, existing in the world at present a plurality of groups have carried out the scientific research in relevant THz wave field, especially about the research of the generation aspect of tunable relevant THz wave.In Korea S; N.J.Kim group has realized in 2009 based on dual wavelength distributed feedback laser diode (Distributed Feedback Laser Diodes; DFB LDs) the tunable continuous wave terahertz emission of pumping, and expand 0.5THz in the broadness of tuning with THz wave in 2010.In Canada, S.L.Pan group has realized in 2009 based on dual wavelength erbium-doped fiber laser (Erbium-Doped Fiber Laser, adjustable microwave signal output EDFL).In the U.S., Y.J.Ding group has realized that in 2010 (Difference Frequency DF) has produced compact, portable terahertz emission source, and its volume can narrow down to 30.48 * 15.24 * 10.16cm based on the dual wavelength difference frequency
3, unique deficiency be: untunable.In Germany; The I.Breunig group of Bonn University constantly improved based on inner chamber optical parametric oscillator (Internal Cavity Optical Parametric Oscillator during 2007 to 2010; ICOPO) tunable THz wave produces scheme; Final its broadness of tuning reaches 2THz, but the temperature stability of heating furnace becomes the key issue of the accurate phase matched of influence (QPM).In France, the J.Mangeney group of French research establishment (CNRS) is devoted to utilize some nonlinear material (like In recent years always
0.53Ga
0.47As) optical mixer (PM) produces the research of tunable continuous THz wave, and maximum broadness of tuning is 0.9THz.In Japan, H.Ito group utilizes UTC-PD (Uni-Traveling-Carrier Photodioed) optical mixer to realize the generation of continuous THz wave, and highest frequency can reach 1.5THz.
The mode that obtains THz wave is a lot, and principle is also different, and the mode that produces tunable relevant THz wave at present roughly can be divided into three major types.The first kind is based on the tunable relevant terahertz emission of research of dual wavelength pumping source and design; Second type is that the pumping source wavelength is fixed, and produces the research and the design of THz wave based on the ICOPO of non-linear cascade process.The 3rd type of tunable terahertz emission source that is based on PM.For the first kind, relate generally to research of tunable relevant terahertz emission source and design at present based on DFB LDs, EDFLs, DF dual wavelength pumping source.The Terahertz tuning range of utilizing DFB LDs to produce is narrower, generally less than 0.5THz; Though the Terahertz tuning range of utilizing the EDFLs mode to produce can reach 0.5THz, its structure is quite complicated; Though and the Terahertz tuning range broad that utilizes the DF mode to produce can reach 20THz, the terahertz emission source apparatus of this mode is quite huge, although 2010 years, Y.J.Ding has realized 30.48 * 15.24 * 10.16cm
3Compact terahertz emission source, however untunable.For second type, though its broadness of tuning can reach 2THz at present, owing to the temperature stability reason, satisfying accurate phase-matching condition is not the part nothing the matter, thereby makes that tuning efficient is lower.For the 3rd type, at present high tuning width is 0.9THz, and obviously its broadness of tuning is narrower.
In a word, said method or broadness of tuning are narrower, or bulky, or tuning efficient is low, or conversion efficiency is low.
Summary of the invention
Technical problem to be solved by this invention provides a kind of compactness, portable, be easy to integrated, the THz wave device that the difference frequency mode that broad tuning and tuning efficient are high produces.
The technical scheme that solves technical problem of the present invention is: a kind of circulation modulation shift frequency nonlinear difference formula wide-band tuning THz wave generator is provided; It comprises laser, first circulator, beam splitter, based on circulation shift frequency link, first beam synthesis, optical isolator, non-linear element and the Terahertz filter plate of modulator shift frequency; The light of said laser output is divided into the first via and the second tunnel by beam splitter after through first circulator; The first via is a reference light; The second the tunnel is input to and produces circulation shift frequency light after the said circulation shift frequency link; Said reference light and circulation shift frequency light carry out difference frequency through optical isolator again in non-linear element after first beam synthesis closes bundle, filtering gives off relevant THz wave through the Terahertz filter plate at last.
Said laser is semiconductor laser, gas laser, solid state laser or the fiber laser of operation wavelength in the 600nm-2000nm wave band.
Said first circulator is a three-port circulator, and its first port connects laser, and second port connects beam splitter, and the 3rd port connects absorbing load, the reverberation of said absorbing load absorbing light beam splitter.
Said non-linear element is the periodic structure that nonlinear material and linear material are alternately arranged; Or alternately arrange the optical superlattice structure that constitutes by nonlinear material and linear material; Or alternately arrange the slow variable period structure that constitutes by nonlinear material and linear material; Or arrange Fibonacci (Fibonacci) structure that constitutes by nonlinear material and linear material, it satisfies the desired phase-matching condition scope of the pairing nonlinear difference process of Terahertz output wave frequency tuning range of system.
Said Terahertz filter plate is logical transmission-type filter of Terahertz band or Terahertz band resistance reflecting filter; For the logical transmission-type filter of band, transmitted wave is output as THz wave, and the ripple of other wavelength can be by this filter reflection; For band resistance reflecting filter, reflected wave is output as THz wave, and the ripple of other wavelength can see through this filter.
The optimum value of the closed loop gain coefficient of said circulation shift frequency link based on the modulator shift frequency is 1, and inferior good value is other positive integer value beyond 1, and good once more value is the reciprocal value of other positive integer beyond 1.
The splitting ratio optimum value of said beam splitter is 1; Inferior good value is the reciprocal value of other positive integer beyond 1; Good once more value is other positive integer value beyond 1, and the splitting ratio of said beam splitter is a reference light power divided by the input optical power based on the circulation shift frequency link of modulator shift frequency.
Said circulation shift frequency link based on the modulator shift frequency comprises second beam synthesis, modulator, second circulator, the first reaction type Bragg grating, tunable optic filter, image intensifer and light amplitude fading device, and said image intensifer and light amplitude fading device are formed the image intensifer of Gain Adjustable.
Said modulator is phase-modulator, frequency modulator or amplitude modulator.
Said second circulator is a three-port circulator, and its first port connects modulator, and second port connects the first reaction type Bragg grating, and the 3rd port connects absorbing load, and said absorbing load absorbs the reverberation of the first reaction type Bragg grating.
Said operational frequency bandwidth based on each parts, first beam synthesis, optical isolator in the circulation shift frequency link of modulator shift frequency is not less than the highest frequency of the THz wave of output.
Said first circulator, beam splitter, consistent with the service band of laser based on the service band of each parts, first beam synthesis, optical isolator in the circulation shift frequency link of modulator shift frequency.
Said tunable optic filter is a narrow band filter; It allows a narrow band light to output to the input of first beam synthesis; And the light of other frequency reflexed to the input of image intensifer; The difference of the arrowband output light frequency of said tunable optic filter and the output light frequency of said laser equals needed Terahertz wave frequency, and the frequency-tuning range of the THz wave of output is not more than the arrowband output light frequency tuning range of tunable optic filter.
Said tunable optic filter is the 1-D photon crystal tunable optic filter or the Bragg grating-completely reflecting mirror assembly of band defect layer.
The forbidden photon band district of said 1-D photon crystal is not less than the frequency tuning range of the THz wave of system's output; Said 1-D photon crystal comprises the adjustable defect layer of one deck refractive index; The regulative mode of the refractive index of said defect layer comprise electricity cause sell off, mangneto is sold off, sound cause sell off, photicly sell off, power causes and sells off or thermic is sold off; Said 1-D photon crystal has a defective mould; Said defective mould changes with the change of refractive of said defect layer; The surface of said 1-D photon crystal tunable optic filter and its incident wave line of propagation in angle of 45 degrees, the arrowband transmitted wave of said 1-D photon crystal tunable optic filter enters into the input of first beam synthesis, the reverberation of said 1-D photon crystal tunable optic filter enters into the input of image intensifer.
Said Bragg grating-completely reflecting mirror assembly comprise one with the incident light direction second reaction type Bragg grating and reflecting surface and incident light direction completely reflecting mirror in angle of 45 degrees in angle of 45 degrees; Between said second reaction type Bragg grating and completely reflecting mirror is an air or dielectric layer; The narrowband reflection light of the said second reaction type Bragg grating is the arrowband output light of this tunable optic filter; The narrowband reflection light of the said second reaction type Bragg grating gets in first beam synthesis; The reverberation of said completely reflecting mirror enters into the input of image intensifer along another light path; The lattice parameter of the said second reaction type Bragg grating cause through piezoelectric effect, magnetostrictive effect, the effect of expanding with heat and contract with cold, electricity sell off, mangneto is sold off, sound cause sell off, photicly sell off, power causes and sells off or the thermic mode of selling off is regulated, with the adjusting of the narrowband reflection light frequency of realizing the said second reaction type Bragg grating.
The present invention's beneficial effect compared with prior art is:
(1) compact, portable.Circulating ultrasonic grating shift frequency nonlinear difference formula wide-band tuning THz wave generator utilizes the volume after the commercially available assembly assembling to be no more than 40 * 10 * 35cm
3, weight is no more than 8kg.
(2) light path is simple.In whole device, have only beam splitter and L
1, L
2Lens are movable optical element, and other part is all fixing, and preferred beam synthesis is a fiber coupler.This device makes things convenient for light integrated.
(3) tuning range or broadness of tuning are big.Even if centre wavelength (for example, 1550nm) receives the bandwidth constraints of tunable optic filter and image intensifer.For bandwidth of operation is tunable optic filter and the image intensifer of 40nm, can obtain the broadness of tuning of 5THz THz wave.This broadness of tuning than most of terahertz emission source in the past is all big.Along with the increase of the broadness of tuning of tunable optic filter and bandpass amplifier, the wavelength regulation scope of output THz wave can correspondingly increase.
(4) tuning efficient is high.The tuning main ultrasonic grating that passes through in this scheme is realized frequency shifts; When the signal frequency after regulating reaches the selecting frequency of tunable optic filter; The narrow band light output of tunable optic filter is just exported the input of a narrow band light to first beam synthesis, and the entering image intensifer otherwise flashlight is reflected is after amplifying; Feed back to the input of ultrasonic grating again, carry out frequency shifts once more through ultrasonic grating.This process does not need manual work or computer intervention, and its tuning efficient is quite high.
(5) Terahertz produces the efficient height.Owing to have the Gain Adjustable part in the circulation shift frequency joint, so the power output of shift frequency light can be than higher, this efficient than any shift frequency mode in the past is all high, and then the conversion efficiency of terahertz emission is also corresponding to higher.
Description of drawings
Below in conjunction with accompanying drawing and embodiment the present invention is described in further detail.
Fig. 1 is the circulate system configuration sketch map of modulation shift frequency nonlinear difference formula wide-band tuning THz wave generator of the present invention.
Fig. 2 is the circulate sketch map of first kind of execution mode of modulation shift frequency nonlinear difference formula wide-band tuning THz wave generator of the present invention.
Fig. 3 is the circulate sketch map of second kind of execution mode of modulation shift frequency nonlinear difference formula wide-band tuning THz wave generator of the present invention, and the slanted bar line in the short dash line frame is wherein filled frame and is respectively reaction type Bragg grating and completely reflecting mirror with black filling frame.
Fig. 4 is the circulate sketch map of the third execution mode of modulation shift frequency nonlinear difference formula wide-band tuning THz wave generator of the present invention.
Fig. 5 is the circulate difference frequency schematic diagram of modulation shift frequency nonlinear difference formula wide-band tuning THz wave generator of the present invention.
Embodiment
The invention provides a kind of circulation modulation shift frequency nonlinear difference formula wide-band tuning THz wave generator; As shown in Figure 1, it comprises laser 1, first circulator 2, beam splitter 3, based on the circulation shift frequency link of modulator shift frequency 4, first beam synthesis 5, optical isolator 6, non-linear element 7 and Terahertz filter plate 8.The light of laser 1 output is divided into the first via and the second tunnel through first circulator, 2 backs by beam splitter 3; The first via is a reference light; The second the tunnel is input to said circulation shift frequency link 4 backs produces circulation shift frequency light; Said reference light and circulation shift frequency light carry out difference frequency through optical isolator 6 again in non-linear element 7 after first beam synthesis 5 closes bundle, 8 filtering give off relevant THz wave through the Terahertz filter plate at last.
Laser 1 is semiconductor laser, gas laser, solid state laser or the fiber laser of operation wavelength in the 600nm-2000nm wave band.First circulator 2 is a three-port circulator, and its first port connects laser 1, the second port and connects beam splitter 3, the three ports connection absorbing load, the reverberation of said absorbing load absorbing light beam splitter 3.
Comprise second beam synthesis 41, modulator 42, second circulator 43, the first reaction type Bragg grating 44, tunable optic filter 45, image intensifer 46 and light amplitude fading device 47 based on the circulation shift frequency link 4 of modulator shift frequency, image intensifer 46 and light amplitude fading device 47 are formed the image intensifer of Gain Adjustable.First circulator 2, beam splitter 3, consistent with the service band of laser 1 based on the service band of each parts, first beam synthesis 5 and optical isolator 6 in the circulation shift frequency link 4 of modulator shift frequency.
Optimum value based on the closed loop gain coefficient (or claiming entire gain coefficient) of the circulation shift frequency link 4 of modulator shift frequency is 1, and inferior good value is other positive integer value beyond 1, and good once more value is the reciprocal value of other positive integer beyond 1.Equal the amplitude of reference light based on the amplitude optimum value of the output light of the circulation frequency displacement link 4 of modulator shift frequency; The splitting ratio optimum value that is beam splitter 3 is 1; Inferior good value is the reciprocal value of other positive integer beyond 1; Good once more value is other positive integer value beyond 1, also is the splitting ratio of beam splitter 3 and product optimum value based on the closed loop gain coefficient of the circulation shift frequency link of modulator shift frequency is 1.The splitting ratio of beam splitter 3 equals reference light power divided by the input power based on the circulation shift frequency link 4 of modulator shift frequency.
Wherein, E
C0Be the amplitude of carrier signal, ω
C0Be the circular frequency of carrier signal, t is the time, k
cBe the wave vector of carrier signal,
Initial phase for carrier signal; If the microwave modulating signal does
E
m＝E
m0sin(ω
mt)， (2)
Wherein, E
M0Be the amplitude of microwave modulating signal, ω
mCircular frequency for the microwave modulating signal.After then passing through the primary modulation of phase-modulator, do from the electric vector of the light of phase-modulator output
A wherein
mBe phase-modulation sensitivity, usually ω
C0T＞＞a
mE
M0. rewriting formula (3) becomes following form:
Δω(t)＝ω
ma
mE
m0cos(ω
mt). (4)
Visible by formula (4), carrier wave is being ω through the maximum frequency shift of modulator after once
ma
mE
M0.
In circulation shift frequency link, obtain N ω behind N circulation shift frequency of light wave process based on phase-modulator
ma
mE
M0The maximum frequency shift amount, as long as this frequency shift amount does not make light frequency reach the selecting frequency of tunable optic filter, then light wave can be fed back to constantly circulation in the circulation shift frequency link, till frequency shift amount makes light frequency reach the selecting frequency of filter.
When being frequency modulator, then directly realizes by modulator 42 frequency displacement.The modulation signal that carrier signal that corresponding (1) provides and formula (2) provide through after the primary modulation of frequency modulator, from the electric vector of the light of frequency modulator output does
B wherein
mBe frequency modulation(FM) sensitivity, usually ω
C0＞＞b
mE
M0.
Visible by formula (5), carrier wave is being b through the maximum frequency shift of frequency modulator after once
mE
M0.
In circulation shift frequency link, obtain Nb through behind N circulation shift frequency based on frequency modulator
mE
M0The maximum frequency shift amount, as long as this frequency shift amount does not make light frequency reach the selecting frequency of tunable optic filter, then light wave can be fed back to constantly circulation in the circulation shift frequency link, light frequency reaches till the selecting frequency of tunable optic filter when frequency shift amount.
Visible by formula (6), through promptly obtaining ω behind shift frequency of amplitude modulator
mThe shift frequency amount.
In circulation shift frequency link, promptly obtain N ω through N circulation shift frequency based on amplitude modulator
mThe maximum frequency shift amount, as long as this frequency shift amount does not make light frequency reach the selecting frequency of tunable optic filter, then light wave can be fed back to constantly circulation in the circulation shift frequency link, till frequency shift amount makes light frequency reach the selecting frequency of tunable optic filter.
Said second circulator 43 is a three-port circulator, and its first port connects modulator 42, the second ports and connects the first reaction type Bragg grating, 44, the three ports connection absorbing load, and said absorbing load absorbs the reverberation of the first reaction type Bragg grating 44.Said operational frequency bandwidth based on each parts, first beam synthesis 5 and optical isolator 6 in the circulation shift frequency link 4 of modulator shift frequency is not less than the highest frequency of the THz wave of output, and promptly operational frequency bandwidth is not less than the maximum frequency shift scope of said circulation shift frequency link based on the modulator shift frequency.
Tunable optic filter 45 is a narrow band filter; It allows a narrow band light to output to the input of first beam synthesis 5; And the light of other frequency reflexed to the input of image intensifer 46; The difference of the arrowband output light frequency of said tunable optic filter 45 and the output light frequency of said laser 1 equals needed Terahertz wave frequency; The Terahertz wave frequency of output realizes that through the arrowband output light frequency of regulating tunable optic filter 45 frequency-tuning range of THz wave is not more than the arrowband output light frequency tuning range of tunable optic filter 45.
Preferably, tunable optic filter 45 is the 1-D photon crystal tunable optic filter (as shown in Figure 2) or the Bragg grating-completely reflecting mirror assembly (as shown in Figure 3) of band defect layer; The forbidden photon band district of said 1-D photon crystal is not less than the frequency tuning range of the THz wave of system's output; Said 1-D photon crystal comprises the adjustable defect layer of one deck refractive index; The regulative mode of the refractive index of said defect layer comprise electricity cause sell off, mangneto is sold off, sound cause sell off, photicly sell off, power causes and sells off or thermic is sold off; Said 1-D photon crystal has a defective mould, and said defective mould changes with the change of refractive of said defect layer, realizes the function of tunable filtering.Preferably; The surface of said 1-D photon crystal tunable optic filter and its incident wave line of propagation are in angle of 45 degrees; The arrowband transmitted wave of said 1-D photon crystal tunable optic filter enters into the input of first beam synthesis 5, and the reverberation of said 1-D photon crystal tunable optic filter enters into the input of image intensifer 46; Said Bragg grating-completely reflecting mirror assembly comprise one with the incident light direction second reaction type Bragg grating and reflecting surface and incident light direction completely reflecting mirror in angle of 45 degrees in angle of 45 degrees; Between said second reaction type Bragg grating and completely reflecting mirror is an air or dielectric layer; The narrowband reflection light of the said second reaction type Bragg grating is the arrowband output light of this tunable optic filter; The narrowband reflection light of the said second reaction type Bragg grating gets in first beam synthesis 5; The reverberation of said completely reflecting mirror enters into the input of image intensifer 46 along another light path; The lattice parameter of the said second reaction type Bragg grating cause through piezoelectric effect, magnetostrictive effect, the effect of expanding with heat and contract with cold, electricity sell off, mangneto is sold off, sound cause sell off, photicly sell off, power causes and sells off or the thermic mode of selling off is regulated, with the adjusting of the narrowband reflection light frequency of realizing the said second reaction type Bragg grating.
The difference frequency principle: as shown in Figure 5, it is the parametric process of three-wave interaction that optical difference frequency produces; Frequency is respectively ω
1And ω
2Pump light in non-linear element, interact, the parameter light frequency of generation is the difference ω of this two bundles pump light frequency
1-ω
2As ω of every consumption
1Photon must produce a ω simultaneously
2Photon, these three frequencies must satisfy energy conservation relation ω
3=ω
1-ω
2In the difference frequency process, the ω that frequency is higher
1Light is consumed, the ω that frequency is lower
2Light will be exaggerated.If produce the difference frequency field effectively, polarized wave must be identical with electromagnetic phase velocity, and promptly interactional three plane waves must satisfy phase-matching condition Δ k=k in the non-linear element
1-k
2-k
3In order to realize the output of wide-band tuning THz wave; Need wide phase matched scope; Through the periodic structure of alternately arranging by nonlinear material and linear material; Or alternately arrange the optical superlattice structure that constitutes by nonlinear material and linear material; Or alternately arrange the slow variable period structure that constitutes, or, can obtain the desired phase-matching condition scope of the pairing nonlinear difference process of Terahertz output wave frequency tuning range of system by nonlinear material Fibonacci (Fibonacci) structure that arrangement constitutes with linear material by nonlinear material and linear material.
Be each part and the running parameter thereof of a kind of embodiment below.Laser 1 is selected 1550nm super-narrow line width continuous conductor laser for use; The operation wavelength of this laser in the time of 25 ℃ is 1550nm, and power output is 5mW, continuous operation mode; Maximum line width is 50kHz, and the output optical fibre type is SMF-28 monomode fiber (9/125 μ m).Modulator 42 is selected phase-modulator for use, is the LiNbO with 700nm to 1650nm wavelength coverage
3Electro-optic phase modulator, and this modulator has 40GHz high modulation bandwidth near 1550nm, insert loss＜3.5dB, and the volume of this modulator is merely 10 * 1.5 * 0.95cm
3The broadness of tuning of 45 pairs of centre wavelengths of tunable optic filter of being selected for use reaches 40nm, and (1528nm～1610nm), the insertion loss is 4.0dB, and the volume of this filter is 24 * 8.8 * 35cm almost to have covered whole C-band
3The bandwidth of operation of the image intensifer of being selected for use 46 is 40nm, has covered whole C-band.The beam splitter selected for use 3 is 10/90 optical element of response 1550nm wavelength, 10 expression reference light parts wherein, 90 expression signal light parts.First circulator 2, second circulator 43 selected for use are to connect the optics of inhaling carrier load; Play the light isolation effect; Simultaneously carrier load is inhaled in the light utilization that reflects and absorb, this device not only plays the light isolation but also plays environmental-protection function, and its response wave length is near 1550nm.The 44 couples of carrier wavelength 1550nm of the first reaction type Bragg grating that selected for use play the reflection inhibitory action.The first combiner device of being selected for use 5, second beam synthesis 41 are the fiber coupler of response 1550nm wavelength.The non-linear element of being selected for use 7 is for become the periodic polarized lithium columbate crystal of inclined (PPLN) slowly, and Terahertz filter plate 8 is the resin material of response terahertz wave band, total reflection or total transmissivity reference light and shift frequency light.
In order to guarantee amplitude coherent superposition such as reference light and shift frequency light, connect amplitude fading device 47 at the output of image intensifer 46.In addition, adopting under the situation of inserting loss less phase-modulator 42 and tunable optic filter 45, then need not use image intensifer 46, the output that only needs amplitude fading device 47 to be received tunable optic filter 45 gets final product, and is as shown in Figure 4.
Wide-band tuning Terahertz generator volume provided by the invention is little, and optical element is few thereby easy of integration, and tuning range is big, and tuning efficient is high, and it is high that Terahertz produces efficient.
The above the present invention all has improvements in embodiment and range of application, is not to be understood that to the present invention is limited.
Claims (1)
1. shift frequency nonlinear difference formula wide-band tuning THz wave generator is modulated in a circulation, and it is characterized in that: it comprises laser (1), first circulator (2), beam splitter (3), the circulation shift frequency link (4) based on the modulator shift frequency, first beam synthesis (5), optical isolator (6), non-linear element (7) and Terahertz filter plate (8); The light of said laser (1) output is divided into the first via and the second tunnel through first circulator (2) back by beam splitter (3); The first via is a reference light; The second the tunnel is input to said circulation shift frequency link (4) back produces circulation shift frequency light; First beam synthesis (5) after optical isolator (6) carries out difference frequency in non-linear element (7), passes through said reference light and circulation shift frequency combiner then Terahertz filter plate (8) filtering and gives off relevant THz wave; Said circulation shift frequency link (4) based on the modulator shift frequency comprises second beam synthesis (41), modulator (42), second circulator (43), the first reaction type Bragg grating (44), tunable optic filter (45), first image intensifer (46) and light amplitude fading device (47), and said first image intensifer (46) and light amplitude fading device (47) are formed the image intensifer of Gain Adjustable; Said tunable optic filter (45) is a narrow band filter; It allows the narrow band light of a frequency adjustable to output to the input of first beam synthesis (5); And the light of other frequency reflexed to the input of first image intensifer (46); The difference of the arrowband output light frequency of said tunable optic filter (45) and the output light frequency of said laser (1) equals needed Terahertz wave frequency, and the frequency-tuning range of the THz wave of output is not more than the arrowband output light frequency tuning range of tunable optic filter (45).
2, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator, it is characterized in that: said laser (1) is semiconductor laser, gas laser, solid state laser or the fiber laser of operation wavelength in the 600nm-2000nm wave band.
3, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator; It is characterized in that: said first circulator (2) is a three-port circulator; Its first port connects laser (1); Second port connects beam splitter (3), and the 3rd port connects absorbing load, the reverberation of said absorbing load absorbing light beam splitter (3).
4, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator; It is characterized in that: said non-linear element (7) replaces the periodic structure of arrangement for nonlinear material and linear material; Or alternately arrange the optical superlattice structure that constitutes by nonlinear material and linear material; Or arrange Fibonacci (Fibonacci) structure that constitutes by nonlinear material and linear material, it satisfies the desired phase-matching condition scope of the pairing nonlinear difference process of Terahertz output wave frequency tuning range of system.
5, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator, it is characterized in that: said Terahertz filter plate (8) is logical transmission-type filter of Terahertz band or Terahertz band resistance reflecting filter; For the logical transmission-type filter of band, transmitted wave is output as THz wave, and the ripple of other wavelength can be by this filter reflection; For band resistance reflecting filter, reflected wave is output as THz wave, and the ripple of other wavelength can see through this filter.
6, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator; It is characterized in that: the optimum value of the closed loop gain coefficient of said circulation shift frequency link (4) based on the modulator shift frequency is 1; Inferior good value is other positive integer value beyond 1, and good once more value is the reciprocal value of other positive integer beyond 1.
7, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator; It is characterized in that: the splitting ratio optimum value of said beam splitter (3) is 1; Inferior good value is the reciprocal value of other positive integer beyond 1; Good once more value is other positive integer value beyond 1, and the splitting ratio of said beam splitter (3) is a reference light power divided by the input optical power based on the circulation shift frequency link (4) of modulator shift frequency.
8, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator, it is characterized in that: said modulator (42) is phase-modulator, frequency modulator or amplitude modulator.
9, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator; It is characterized in that: said second circulator (43) is a three-port circulator; Its first port connects modulator (42); Second port connects the first reaction type Bragg grating (44), and the 3rd port connects absorbing load, and said absorbing load absorbs the reverberation of the first reaction type Bragg grating (44).
10, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator, it is characterized in that: said operational frequency bandwidth based on each parts, first beam synthesis (5), optical isolator (6) in the circulation shift frequency link (4) of modulator shift frequency is not less than the highest frequency of the THz wave of output.
11, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator, it is characterized in that: said first circulator (2), beam splitter (3), consistent with the service band of laser (1) based on the service band of each parts, first beam synthesis (5), optical isolator (6) in the circulation shift frequency link (4) of modulator shift frequency.
12, according to the described circulation modulation of claim 1 shift frequency nonlinear difference formula wide-band tuning THz wave generator, it is characterized in that: said tunable optic filter (45) is the 1-D photon crystal tunable optic filter or the Bragg grating-completely reflecting mirror assembly of band defect layer.
13, according to the described circulation modulation of claim 12 shift frequency nonlinear difference formula wide-band tuning THz wave generator; It is characterized in that: the forbidden photon band district of said 1-D photon crystal is not less than the frequency tuning range of the THz wave of system's output; Said 1-D photon crystal comprises the adjustable defect layer of one deck refractive index; The regulative mode of the refractive index of said defect layer comprise electricity cause sell off, mangneto is sold off, sound causes and sells off; Said 1-D photon crystal has a defective mould; Said defective mould changes with the change of refractive of said defect layer; The surface of said 1-D photon crystal tunable optic filter and its incident wave line of propagation in angle of 45 degrees, the arrowband transmitted wave of said 1-D photon crystal tunable optic filter enters into the input of first beam synthesis (5), the reverberation of said 1-D photon crystal tunable optic filter enters into the input of first image intensifer (46).
14, according to the described circulation modulation of claim 12 shift frequency nonlinear difference formula wide-band tuning THz wave generator; It is characterized in that: said Bragg grating-completely reflecting mirror assembly comprise one with the incident light direction second reaction type Bragg grating and reflecting surface and incident light direction completely reflecting mirror in angle of 45 degrees in angle of 45 degrees; Between said second reaction type Bragg grating and completely reflecting mirror is an air or dielectric layer; The narrowband reflection light of the said second reaction type Bragg grating is the arrowband output light of this tunable optic filter; The narrowband reflection light of the said second reaction type Bragg grating gets in first beam synthesis (5); The reverberation of said completely reflecting mirror enters into the input of first image intensifer (46) along another light path; The lattice parameter of the said second reaction type Bragg grating cause through piezoelectric effect, magnetostrictive effect, electricity sell off, the mangneto mode of selling off regulates, with the adjusting of the narrowband reflection light frequency of realizing the said second reaction type Bragg grating.
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| CN103427015B (en) * | 2013-09-02 | 2015-10-21 | 南京大学 | A kind of portable high power continuously adjustabe Terahertz generator |
| CN104330154B (en) * | 2014-10-16 | 2016-08-24 | 中国电子科技集团公司第五十研究所 | The terahertz detector of narrow linewidth |
| CN104332803A (en) * | 2014-10-16 | 2015-02-04 | 中国电子科技集团公司第五十研究所 | Narrow linewidth terahertz detector |
| WO2018129675A1 (en) * | 2017-01-11 | 2018-07-19 | 深圳大学 | Periodically polarized crystal and optical parameter amplifier |
| CN107611755B (en) * | 2017-10-13 | 2024-02-23 | 首都师范大学 | System and method for generating high-intensity terahertz waves by double plasmas with adjustable spacing |
| CN108535891B (en) * | 2018-04-11 | 2020-01-10 | 雄安华讯方舟科技有限公司 | Terahertz wave front phase modulation method |
| CN113783627B (en) * | 2020-06-09 | 2022-12-30 | 华为技术有限公司 | Signal generation method, device and system |
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| US6723991B1 (en) * | 2000-10-20 | 2004-04-20 | Imra America, Inc. | Single-shot differential spectroscopy and spectral-imaging at submillimeter wavelengths |
| CN101408708A (en) * | 2008-11-26 | 2009-04-15 | 天津大学 | Pumping optical multiplexing high-efficiency generating high power THz radiation pulse source |
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| CN101408708A (en) * | 2008-11-26 | 2009-04-15 | 天津大学 | Pumping optical multiplexing high-efficiency generating high power THz radiation pulse source |
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