CN106052873A - Gas-based terahertz wave coherent detector and terahertz wave polarization detection method - Google Patents
Gas-based terahertz wave coherent detector and terahertz wave polarization detection method Download PDFInfo
- Publication number
- CN106052873A CN106052873A CN201610366074.6A CN201610366074A CN106052873A CN 106052873 A CN106052873 A CN 106052873A CN 201610366074 A CN201610366074 A CN 201610366074A CN 106052873 A CN106052873 A CN 106052873A
- Authority
- CN
- China
- Prior art keywords
- thz wave
- harmonic
- light
- wave
- electrode
- 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.)
- Granted
Links
- 238000001514 detection method Methods 0.000 title claims abstract description 80
- 230000010287 polarization Effects 0.000 title claims abstract description 79
- 230000001427 coherent effect Effects 0.000 title abstract description 7
- 230000005684 electric field Effects 0.000 claims abstract description 62
- 239000000523 sample Substances 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 20
- 230000003287 optical effect Effects 0.000 claims description 18
- 239000013078 crystal Substances 0.000 claims description 13
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 12
- 229910052710 silicon Inorganic materials 0.000 claims description 12
- 239000010703 silicon Substances 0.000 claims description 12
- 230000010355 oscillation Effects 0.000 claims description 7
- 230000005611 electricity Effects 0.000 claims description 5
- 238000005086 pumping Methods 0.000 claims description 3
- 230000006698 induction Effects 0.000 abstract 2
- 238000010586 diagram Methods 0.000 description 7
- 230000008859 change Effects 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000006872 improvement Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 108010076504 Protein Sorting Signals Proteins 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 235000013399 edible fruits Nutrition 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000009738 saturating Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/447—Polarisation spectrometry
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The present invention discloses a gas-based terahertz wave coherent detector and a terahertz wave polarization detection method. The gas-based terahertz wave coherent detector comprises the following components that: a terahertz wave generating unit used for generating terahertz waves through pump light; a detecting light unit used for obtaining detection light coming from the same source as the pump light; a second harmonic wave induced generation unit used for focusing the terahertz waves and the detection light at the center of a quadrature electrode to generate second harmonic waves based on the induction of the terahertz waves and generate second harmonic waves based on the induction of an electric field generated by the quadrature electrode, and making the second harmonic waves enter a detection unit, wherein the quadrature electrode generates the electric field distributed in an orthogonal direction; and the detection unit used for detecting the second harmonic waves entering the detection unit so as to obtain the components of the terahertz waves in the orthogonal direction, so that the polarization state of the terahertz waves can be reconstructed. With the gas-based terahertz wave coherent detector and the terahertz wave polarization detection method of the invention adopted, two orthogonal components of the terahertz waves can be detected accurately at the same time, so that the polarization of the terahertz waves can be accurately determined.
Description
Technical field
The present invention relates to THz wave field of detecting, particularly relate to a kind of THz wave coherence detector based on gas and
Terahertz polarization detection method.
Background technology
The method measuring terahertz polarization is generally basede on THz wave electro optic sampling or photoconductive antenna technology, terahertz
Hereby the polarization state of ripple can be measured the Terahertz waveform of two orthogonal directions by rotating Terahertz wire-grid polarizers and rebuild and obtain
?.As the improvement of this method, research worker attempts measuring the quadrature component of terahertz polarization simultaneously.But, along with Gao Gong
Rate, the appearance of super large bandwidth THz source, conventional polarization Detection Techniques based on solid probe are due to limited detective bandwidth
The THz source of these novelties it has been no longer appropriate for intensity threshold.
Higher electric field (more than 1MV/cm) and ultra broadband spectrum (more than 40THz) is studied in order to extend THz wave,
Need a kind of THz wave coherence detector mated with high power, super large bandwidth THz source and terahertz polarization detection side badly
Method solves the problems referred to above.
Summary of the invention
THz wave coherence detector based on gas and terahertz polarization detection method that the present invention provides are applicable to
High power, super large bandwidth THz source, for the THz wave of random polarization, by producing the most discontinuous at crossed electrode
Rotary DC electric field, involves DC electric field by detection Terahertz and inducts the polarization state of second harmonic, can reconstruct THz wave
Polarization state.
One aspect of the present invention provides a kind of THz wave coherence detector based on gas, including: THz wave produces single
Unit, detection light unit, the second harmonic that comprises crossed electrode are inducted unit and probe unit；Wherein, THz wave produces single
Unit, for producing THz wave by pump light, makes THz wave enter second harmonic and inducts unit；Detection light unit, is used for
Obtain and the detection light of pump light homology, make detection light enter second harmonic and induct unit；Second harmonic is inducted unit, for will
THz wave focuses on crossed electrode center with detection light, generates second harmonic and crossed electrode generation that THz wave is inducted
The second harmonic inducted of electric field, and make second harmonic that THz wave inducts and the second harmonic that described electric field is inducted enter
Probe unit；Wherein, described crossed electrode produces the electric field of orthogonal direction distribution；Probe unit, for humorous to the secondary entered
Ripple carries out detecting the component obtaining THz wave at described orthogonal direction, thus reconstructs the polarization state of THz wave.
Preferably, THz wave generation unit includes: LASER Light Source, beam splitter, the first lens, bbo crystal；Wherein, swash
The laser that radiant produces is divided into pump light and detection light after beam splitter, and pump light enters BBO after the first lens are assembled
Crystal produces frequency doubled light, and after pump light focuses on frequency doubled light, ionized air produces THz wave；And bbo crystal is additionally operable to pass through
Change inclination angle and produce the THz wave of different polarization states.
Preferably, detection light unit includes: the first reflecting mirror, the second reflecting mirror, the 3rd reflecting mirror and the second lens；Its
In, the first reflecting mirror, the second reflecting mirror, the 3rd reflecting mirror are for changing the light path of detection light so that it is enter the second lens；Second
Reflecting mirror, the 3rd reflecting mirror are additionally operable to the time difference changing detection light with THz wave；Second lens are for assembling detection light
To crossed electrode center.
Preferably, crossed electrode includes being arranged at the first electrode of X-direction and being arranged at the second electrode of Y-direction；And
First electrode inputs the first square-wave signal Ebias(Ω t), the second electrode inputs the second square-wave signal Ebias(Ωt+π/2)；Wherein,
First electrode and the second electrode are for producing the rotary DC electric field along X+Y, X-Y direction, and X-direction is vertical with Y-direction, and Ω is the
One square-wave signal and the angular frequency of the second square-wave signal, the frequency of the first square-wave signal and the second square-wave signal is described laser weight
The 1/4 of complex frequency.
Preferably, second harmonic unit of inducting also includes: silicon optical filter, the first paraboloidal mirror, terahertz polarization sheet,
Two paraboloidal mirrors, the 3rd paraboloidal mirror, paraboloidal mirror with holes and second harmonic optical filter；Wherein, silicon optical filter only makes Terahertz
The THz wave that ripple generation unit produces passes through, and is collimated through the first paraboloidal mirror successively by the THz wave of silicon optical filter, the
Two paraboloidal mirrors focus on, the 3rd paraboloidal mirror collimation, paraboloidal mirror with holes focus on crossed electrode center；Second harmonic filters
It is single that second harmonic that sheet is inducted for only making THz wave and the second harmonic that described rotary DC electric field is inducted enter detection
Unit；Terahertz polarization sheet is arranged between the first paraboloidal mirror and the second paraboloidal mirror, for improving the polarization of THz wave
The linearity, and for changing the polarization direction of THz wave；Paraboloidal mirror with holes is additionally operable to the detection light making the second lens assemble
Pass through, arrive crossed electrode center.
Preferably, probe unit includes: the 4th reflecting mirror, the 3rd lens, photomultiplier tube and lock-in amplifier；Wherein,
The second harmonic of entrance probe unit, after the 4th reflecting mirror reflection, is gathered photomultiplier tube by the 3rd lens；Photomultiplier transit
The light intensity signal of the second harmonic that pipe detection is incident；Lock-in amplifier locks the first signal from described light intensity signal, and from
One signal is isolated the THz wave component in X+Y, X-Y direction, thus reconstructs the polarization state of THz wave；Wherein, first
Signal is the component that in described light intensity signal, frequency of oscillation is equal to crossed electrode bias voltage frequency.
Preferably, described LASER Light Source is Ti∶Sapphire laser femtosecond laser amplifier.
Another aspect of the present invention provides a kind of terahertz polarization detection method, including step: laser is divided into homology by S1.
Pump light with detection light, utilize pump light produce THz wave；S2. adjusting light path makes THz wave just focus on detection light
Hand over electrode centers, produce the second harmonic inducted of THz wave and second harmonic that electric field that crossed electrode produces is inducted；Its
In, described crossed electrode produces the electric field of orthogonal direction distribution；S3. second harmonic and described electricity that THz wave is inducted are detected
The light intensity signal of second harmonic inducted in field, isolate from described light intensity signal THz wave described orthogonal direction point
Amount, thus reconstruct the polarization state of THz wave.
Preferably, step S2 also includes: the first electrode in crossed electrode is arranged at X-direction, in crossed electrode
Two electrodes are arranged at Y-direction；The first square-wave signal E is inputted at the first electrodebias(Ω t), inputs the second square wave at the second electrode
Signal Ebias(Ωt+π/2)；Wherein, X-direction is vertical with Y-direction, and the first electrode and the second electrode are for producing along X+Y, X-Y side
To rotary DC electric field, Ω is the first square-wave signal and the angular frequency of the second square-wave signal, the first square-wave signal and second party
The frequency of ripple signal is the 1/4 of described laser repetition rate；And described from described light intensity signal, isolate THz wave exist
The component of described orthogonal direction specifically includes: locks the first signal from described light intensity signal, and isolates from the first signal
THz wave is at the component in X+Y, X-Y direction；Wherein, during the first signal is described light intensity signal, frequency of oscillation is equal to crossed electrode
The component of bias voltage frequency.
Preferably, described utilize pump light produce THz wave particularly as follows: make pump light produce frequency multiplication by bbo crystal
Light, focal pumping light and frequency doubled light produce THz wave；And described method is after step S1, also include: silicon is set and filters
Sheet, for only making the THz wave of generation pass through；And described method is upon step s 2, also includes: arrange second harmonic filter
Second harmonic that mating plate is inducted for only making THz wave and the second harmonic that described rotary DC electric field is inducted pass through；And
Step S2 also includes: arrange terahertz polarization sheet, for improving the polarization linearity of THz wave, and is used for changing Terahertz
The polarization direction of ripple.
As shown from the above technical solution, the present invention uses a crossed electrode to produce the bias direct current voltage of probe portion,
The discontinuous rotary DC electric field that use is uniformly distributed, direction determines, it is possible to just simultaneously accurately detecting two of THz wave
Hand over component, and then accurately determine the polarization of THz wave.
Accompanying drawing explanation
Fig. 1 is the THz wave coherence detector schematic diagram based on gas of the present invention；
Fig. 2 is the discontinuous rotary DC electric field sequential chart of the embodiment of the present invention；
Fig. 3 is the discontinuous rotary DC electric field of the embodiment of the present invention and continuous rotary DC electric field comparison diagram；
Fig. 4 is the Terahertz wave source polarization state schematic diagram of the THz wave coherence detector detection of the present invention；
Fig. 5 is the terahertz polarization detection method schematic diagram of the present invention.
Detailed description of the invention
For making the purpose of the present invention, technical scheme and advantage clearer, referring to the drawings and enumerate preferred reality
Executing example, the present invention is described in more detail.However, it is necessary to explanation, the many details listed in description are only
Make the reader one or more aspects of the present invention are had a thorough explanation, can also even without these specific details
Realize the aspects of the invention.
The present inventor considers that existing Polarization Detection technology is due to limited detective bandwidth and intensity threshold, nothing
Method is applicable to high power, the THz source of super large bandwidth, therefore proposes a kind of based on plasma to detect any Terahertz
The method of wave polarization.
THz wave Detection Techniques based on plasma owing to having excellent bandwidth, high detection sensitivity, altofrequency are divided
Resolution and high damage threshold, significant in THz wave field of detecting.These Detection Techniques use air as medium
Detection THz wave, focuses on THz wave with detection light and a little induces second harmonic, by detecting the light intensity of second harmonic
Signal obtains the amplitude of THz wave, phase information.
The induct process of second harmonic of THz wave can be explained by four-wave mixing theory: a Terahertz photon and two
Second harmonic field after individual fundamental wave photon mixing can be represented by the formula:
E2ω∝χ(3)ETHzEωEωFormula 1
Wherein, χ(3)It is the third-order nonlinear susceptibility of gas, Eω、E2ω、ETHzIt is fundamental frequency light, second harmonic, terahertz respectively
The hereby electric field intensity of ripple.The present invention, in order to improve the signal to noise ratio of air detection THz wave, dynamic range and accuracy, utilizes standard
The principle of coherent detection THz wave, in conjunction with difference detecting technology, the focal point at fundamental wave modulates a direct current biasing field.On
State direct current biasing field to induct second harmonic, as a local oscillator in detection.The detection process of the present invention can describe
For:
Wherein, I2ωFor the light intensity of second harmonic,For the electric field intensity of the second harmonic that THz wave is inducted,
For the electric field intensity of the second harmonic that DC electric field is inducted, IωFor fundamental frequency light light intensity,For three rank of gas in above-mentioned environment
Non-linear susceptibility.
It will be seen that formula 2 exists second harmonic that Terahertz inducts and the second harmonic that DC electric field is inducted.But
It is that the DC offset voltage of periodic modulation can produce the second harmonic of periodic modulation, if locking this feature with lock-in amplifier
Frequency, just can lock the Section 3 on the right side of formula 2.Such as, in the embodiment of the present invention, the repetition rate of femtosecond laser is 1kHz, as
Fruit sets the frequency of DC offset voltage as 250Hz, then the Section 1 on the right side of formula 2 is 1kHz, and Section 2 is 500Hz, and the
The frequency of three is 250Hz.The locking frequency of lock-in amplifier is set to 250Hz, just can filter the letter of Section 1 and Section 2
Number, and lock the signal of Section 3, then:
The second harmonic intensity now detected is directly proportional to Terahertz field intensity, remains amplitude and the phase place of THz wave
Information, so being coherent detection.
Meanwhile, the present invention produces the DC electric field of discontinuous rotation the most in that orthogonal direction.Concrete grammar such as Fig. 2 institute
Show, the electrode of X-direction adds the square wave E of 1/4 laser repetition rate (such as 250Hz)bias(Ω t), adds identical in the Y direction
The square wave E of frequencybias(Ω t+ pi/2), thus produces a DC electric field along the rotation of X+Y and X-Y orthogonal direction, such as figure
E in 2biasShown in ' one hurdle.So, the second harmonic signal detected can be expressed as:
Wherein,For the second harmonic projection in X+Y direction,For the second harmonic projection in X-Y direction,The second harmonic inducted for the THz wave projection in X+Y direction,The second harmonic inducted for THz wave is at X-
The projection of Y-direction,The second harmonic inducted for the DC electric field projection in X+Y direction,Induct for DC electric field
Second harmonic is in the projection in X-Y direction.
Due toWithPhase pi/2, so by biphase lock-in amplifier, can isolate phase place phase
Difference pi/2WithSignal, thus detect THz wave in the amplitude of orthogonal direction and phase place, by just
Hand over the THz wave component in direction, the polarization state of THz wave can be reconstructed.
Fig. 1 shows the THz wave coherence detector schematic diagram based on gas of the present invention, sees Fig. 1, THz wave
Coherence detector includes: THz wave generation unit, detection light unit, second harmonic are inducted unit and probe unit.
Second harmonic therein unit of inducting comprises crossed electrode 18, and crossed electrode 18 produces the electricity of orthogonal direction distribution
?.In a preferred embodiment of the invention, crossed electrode 18 includes the first electrode being arranged at X-direction and be arranged at Y-direction
Two electrodes, X-direction therein is vertical with Y-direction, the i.e. first electrode and the orthogonal setting of the second electrode.
First electrode inputs the first square-wave signal Ebias(Ω t), the second electrode inputs the second square-wave signal Ebias(Ωt+π/
2).Ω therein is the first square-wave signal and the angular frequency of the second square-wave signal, the first square-wave signal and the second square-wave signal
Frequency is equal, for producing the 1/4 of the laser repetition rate of THz wave.
Above-mentioned setting makes the first electrode and the second electrode produce the uniform discontinuous rotary DC electricity along X+Y, X-Y direction
, the above-mentioned electric field heart in the electrodes is uniformly distributed and electric field level is identical at different directions, and this is outstanding to THz wave coherent detection
For important, because uneven DC electric field directly influences the THz wave of detection and inducts the waveform of second harmonic, thus drop
The degree of accuracy of the terahertz polarization state of low measurement.It addition, the direction of above-mentioned electric field is it is known that only exist X+Y, X-Y direction, so
It is easy to determine the polarization direction of THz wave.
Fig. 2 shows the discontinuous rotary DC electric field sequential chart of the embodiment of the present invention, sees Fig. 2, ETHzOne hurdle is terahertz
The hereby sequential of ripple, its frequency of oscillation is equal with laser repetition rate, is four times of crossed electrode 18 square-wave signal.One hurdle is
First square wave signal sequence,One hurdle is the second square wave signal sequence.Ebias' one hurdle is the discontinuous of crossed electrode 18 generation
Rotary DC electric field sequential, it is seen that within a cycle, Ebias' discontinuous rotate in X+Y, X-Y direction, through four shapes
State.
By comparison, although the DC electric field rotated continuously in the cycle meets orthogonal, but the direction of electric field with just
The phase place of string ripple is correlated with, so DC electric field direction is difficult to determine, finally affects the determination in terahertz polarization direction.
Fig. 3 is the discontinuous rotary DC electric field of the embodiment of the present invention and continuous rotary DC electric field comparison diagram.Such as Fig. 3 institute
Showing, a is the discontinuous rotary DC electric field produced by square wave of finite element simulation, b be finite element simulation by sine wave
The continuous rotary DC electric field produced.From the figure, it can be seen that Electric Field Distribution is uniform and size is identical in a, high directivity simultaneously.
In b, uniformity and the directivity of electric field are poor.Visible, the discontinuous rotary DC electric field that the present invention uses is more beneficial for Terahertz
The detection of ripple.
THz wave generation unit in THz wave coherence detector, for producing THz wave by pump light, makes too
Hertz wave enters second harmonic and inducts unit.
In actual application, photoconductive antenna or optical rectification method can be used to produce THz wave.The most real in the present invention
Execute in example, utilize ionized air to produce THz wave.Specifically, THz wave generation unit includes: LASER Light Source is (in figure not
Mark), beam splitter the 1, first lens 2, bbo crystal 3.
It is preferred that LASER Light Source is Ti∶Sapphire laser femtosecond laser amplifier, its laser pulse average output power launched is
3.5W, repetition rate is 1kHz, and centre wavelength is 800nm, and pulsewidth is 50fs.In actual application, LASER Light Source can also be it
The femto-second laser of its type.
The laser that above-mentioned LASER Light Source produces is divided into pump light and detection light after beam splitter 1, and pump light is saturating through first
Mirror 2 enters bbo crystal 3 and produces frequency doubled light after assembling, after pump light focuses on frequency doubled light, ionized air produces THz wave.
Bbo crystal 3 is additionally operable to produce the THz wave of different polarization states by changing inclination angle, and then by the present invention's
THz wave coherence detector detects its polarization.
Detection light unit, for obtaining and the detection light of pump light homology, makes detection light enter second harmonic and inducts unit.
As a preferred version, detection light unit includes: first reflecting mirror the 14, second reflecting mirror the 15, the 3rd reflecting mirror
16 and second lens 17.
Specifically, first reflecting mirror the 14, second reflecting mirror the 15, the 3rd reflecting mirror 16 is used for changing the light path of detection light,
Make it into the second lens 17.Second lens 17 for gathering crossed electrode 18 center by detection light.Second reflecting mirror 15,
Three reflecting mirrors 16 are placed on electric control displacement platform, additionally it is possible to change the time difference of detection light and THz wave.
Second harmonic inducts unit for THz wave and detection light are focused on crossed electrode 18 center, generation Terahertz
Second harmonic that ripple is inducted and the second harmonic that the electric field that crossed electrode 18 produces is inducted, and the secondary making THz wave induct is humorous
Involve the second harmonic entrance probe unit that electric field is inducted.Two inducted by the DC electric field in X+Y, X-Y direction omnidirectional distribution
Subharmonic is equally along X+Y, X-Y directional spreding, and probe unit can thus obtain the THz wave component at above-mentioned orthogonal direction,
And then know the polarization state of THz wave.
It is preferred that in embodiments of the present invention, second harmonic unit of inducting includes: crossed electrode 18, silicon optical filter 5,
One paraboloidal mirror 4, terahertz polarization sheet the 6, second paraboloidal mirror the 7, the 3rd paraboloidal mirror 8, paraboloidal mirror with holes 9 and secondary are humorous
Ripple optical filter 10.
Specifically, the THz wave that silicon optical filter 5 only makes THz wave generation unit produce passes through, stop pump light, times
Frequently light etc..
Collimated through the first paraboloidal mirror 4 successively by the THz wave of silicon optical filter, the second paraboloidal mirror 7 focuses on, the 3rd
Paraboloidal mirror 8 collimates, paraboloidal mirror 9 with holes focus on crossed electrode 18 center.One is arranged little in the middle part of paraboloidal mirror 9 with holes
Hole, so that detection light is by arriving crossed electrode 18 center.
Second harmonic optical filter 10 is arranged between crossed electrode 18 and probe unit, for only making THz wave induct
The second harmonic that second harmonic and described rotary DC electric field are inducted enters probe unit, stops detection light, THz wave etc..
Terahertz polarization sheet 6 is arranged between the first paraboloidal mirror 4 and the second paraboloidal mirror 7.Owing to plasma produces
The raw THz wave linearity is the highest, therefore at THz wave after the first paraboloidal mirror 4 collimation, uses terahertz polarization sheet
6 linearities improving terahertz polarization.Terahertz polarization sheet 6 is additionally operable to change the polarization direction of THz wave, and then produces
The THz wave of raw different polarization states.
The second harmonic that probe unit is used for entering detects the component obtaining THz wave at orthogonal direction, thus
The polarization state of reconstruct THz wave.In a preferred embodiment of the invention, above-mentioned orthogonal direction is X+Y, X-Y direction.
In a preferred embodiment of the invention, probe unit includes: the 4th reflecting mirror the 11, the 3rd lens 12, photomultiplier tube
13, preposition current amplifier (not marking in figure) and lock-in amplifier (not marking in figure).Lock-in amplifier therein is two-phase
Lock-in amplifier.
Specifically, the second harmonic of entrance probe unit, after the 4th reflecting mirror 11 reflection, is gathered by the 3rd lens 12
Photomultiplier tube 13；
Photomultiplier tube 13 detects the light intensity signal of the second harmonic of incidence.Preposition current amplifier low noise amplifies light intensity letter
Number；Lock-in amplifier locks the first signal from the light intensity signal amplified, and isolates THz wave from the first signal at X+
The component in Y, X-Y direction, thus reconstructs the polarization state of THz wave.First signal therein is to vibrate in the light intensity signal amplified
Frequency is equal to the component of crossed electrode 18 bias voltage frequency.For example, if the frequency of crossed electrode 18 bias voltage is
250Hz, then lock-in amplifier locks the signal that frequency of oscillation is 250Hz from second harmonic light intensity signal, and therefrom extracts too
The quadrature component of Hertz wave.It is preferred that the frequency of crossed electrode 18 bias voltage is different from the repetition rate of laser.
The process that lock-in amplifier separates THz wave quadrature component from the first signal is as follows: lock-in amplifier is from first
Signal separates the first signalProjection in X+Y, X-Y directionWithAnd from
Above-mentioned two projection signal obtains the projection in X+Y, X-Y direction of second harmonic that THz wave inductsBy
The second harmonic inducted to it in THz wave is directly proportional, and the most therefrom obtains the THz wave time domain in X+Y, X-Y direction
Waveform, thus reconstruct the polarization state of THz wave with this.
Above-mentioned first reflecting mirror the 14, second reflecting mirror the 15, the 3rd reflecting mirror the 16, the 4th reflecting mirror 11 is plane mirror, first
Lens the 2, second lens the 17, the 3rd lens 12 are convex lens.
Thus, the THz wave coherence detector based on gas of the present invention uses a crossed electrode to produce uniform point
The discontinuous rotary DC electric field that cloth, direction determine, it is possible to simultaneously accurately detect two quadrature components of THz wave, and then
Accurately determine the polarization of THz wave.
Fig. 4 shows the Terahertz of the THz wave coherence detector detection removing terahertz polarization sheet 6 of the present invention
Wave source polarization state, sees Fig. 4, and bottom surface and left surface are the THz wave projection in X+Y, X-Y direction respectively, and middle curve is
By the terahertz polarization state of reconstruction from projection, right flank is the projection at right flank of the terahertz polarization state.
Fig. 5 shows the terahertz polarization detection method schematic diagram of the present invention, as it is shown in figure 5, terahertz polarization is visited
Survey method performs with specific reference to following steps:
First, in step sl, laser is divided into pump light and the detection light of homology, utilizes pump light to produce Terahertz
Ripple.
Then, in step s 2, adjust light path and make THz wave focus on crossed electrode 18 center with detection light, produce too
Second harmonic that Hertz wave is inducted and the second harmonic that the electric field that crossed electrode 18 produces is inducted.Crossed electrode 18 therein produces
The electric field of raw orthogonal direction distribution.
It follows that in step s3, second harmonic that detection THz wave is inducted and the light of the second harmonic that electric field is inducted
Strong signal, isolates the THz wave component at described orthogonal direction from light intensity signal, thus reconstructs the polarization of THz wave
State.
In a preferred embodiment of the invention, step S2 also includes: the first electrode in crossed electrode 18 is arranged at X side
To, the second electrode in crossed electrode 18 is arranged at Y-direction.The first square-wave signal E is inputted at the first electrodebias(Ω t),
Two electrodes input the second square-wave signal Ebias(Ωt+π/2)。
In above-mentioned steps, X-direction is vertical with Y-direction, and the first electrode and the second electrode are for producing along X+Y, X-Y direction
Rotary DC electric field, Ω is the first square-wave signal and the angular frequency of the second square-wave signal, the first square-wave signal and the second square wave
The frequency of signal is the 1/4 of laser repetition rate.
In step s3, from light intensity signal, isolate THz wave to specifically include at the component of described orthogonal direction: from
Light intensity signal locks the first signal, and from the first signal, isolates the THz wave component in X+Y, X-Y direction.Therein
First signal is the component that in light intensity signal, frequency of oscillation is equal to crossed electrode 18 bias voltage frequency.
As a preferred version, pump light is utilized to produce THz wave particularly as follows: make pump light pass through bbo crystal 3 and produce
Raw frequency doubled light, focal pumping light and frequency doubled light produce THz wave.
After step S1, said method also includes: arrange silicon optical filter 5, for only making the THz wave of generation pass through.
After step S2, said method also includes: arrange second harmonic optical filter 10 for only making THz wave induct
The second harmonic that second harmonic and rotary DC electric field are inducted passes through.
Step S2 also includes: arrange terahertz polarization sheet 6, for improving the polarization linearity of THz wave, and is used for
Change the polarization direction of THz wave.
Polarization-Sensitive THz wave coherence detector in the present invention can adjust the polarization state of Terahertz wave source, specifically
Method is:
(1) terahertz polarization direction is directly changed by rotation terahertz polarization sheet 6.
(2) by changing the circularly polarized THz wave of inclination angle acquisition of bbo crystal 3.
THz wave coherence detector based on gas and terahertz polarization detection method that the present invention provides can be same
Time detect two quadrature components of THz wave of any polarization state exactly, and then accurately determine the polarization of THz wave.
One of ordinary skill in the art will appreciate that all or part of step realizing in above-described embodiment method is permissible
Instructing relevant hardware by program to complete, this program can be stored in a computer read/write memory medium, such as:
ROM/RAM, magnetic disc, CD etc..
The above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
For Yuan, under the premise without departing from the principles of the invention, it is also possible to make some improvements and modifications, these improvements and modifications also should
It is considered as protection scope of the present invention.
Claims (10)
1. a THz wave coherence detector based on gas, it is characterised in that including: THz wave generation unit, detection
Light unit, the second harmonic comprising crossed electrode are inducted unit and probe unit；Wherein,
THz wave generation unit, for producing THz wave by pump light, makes THz wave enter second harmonic and inducts list
Unit；
Detection light unit, for obtaining and the detection light of pump light homology, makes detection light enter second harmonic and inducts unit；
Second harmonic is inducted unit, for THz wave is focused on crossed electrode center with detection light, generates THz wave sense
The second harmonic that the electric field that raw second harmonic and crossed electrode produce is inducted, and make second harmonic that THz wave inducts and
The second harmonic that described electric field is inducted enters probe unit；Wherein, described crossed electrode produces the electric field of orthogonal direction distribution；
Probe unit, for the second harmonic entered is detected the component obtaining THz wave at described orthogonal direction, from
And reconstruct the polarization state of THz wave.
2. detector as claimed in claim 1, it is characterised in that THz wave generation unit includes: LASER Light Source, beam splitting
Mirror, the first lens, bbo crystal；Wherein,
The laser that LASER Light Source produces is divided into pump light after beam splitter and assembles laggard with detection light, pump light through the first lens
Entering bbo crystal and produce frequency doubled light, after pump light focuses on frequency doubled light, ionized air produces THz wave；And
Bbo crystal is additionally operable to produce the THz wave of different polarization states by changing inclination angle.
3. detector as claimed in claim 2, it is characterised in that detection light unit includes: the first reflecting mirror, the second reflection
Mirror, the 3rd reflecting mirror and the second lens；Wherein,
First reflecting mirror, the second reflecting mirror, the 3rd reflecting mirror are for changing the light path of detection light so that it is enter the second lens；The
Two-mirror, the 3rd reflecting mirror are additionally operable to the time difference changing detection light with THz wave；
Second lens are for gathering crossed electrode center by detection light.
4. detector as claimed in claim 3, it is characterised in that crossed electrode include the first electrode being arranged at X-direction with
It is arranged at the second electrode of Y-direction；And
First electrode inputs the first square-wave signal Ebias(Ω t), the second electrode inputs the second square-wave signal Ebias(Ωt+π/2)；Its
In,
First electrode and the second electrode are for producing the rotary DC electric field along X+Y, X-Y direction, and X-direction is vertical with Y-direction, Ω
Being the first square-wave signal and the angular frequency of the second square-wave signal, the frequency of the first square-wave signal and the second square-wave signal is described sharp
The 1/4 of light repetition rate.
5. detector as claimed in claim 4, it is characterised in that second harmonic unit of inducting also includes: silicon optical filter, first
Paraboloidal mirror, terahertz polarization sheet, the second paraboloidal mirror, the 3rd paraboloidal mirror, paraboloidal mirror with holes and second harmonic filter
Sheet；Wherein,
The THz wave that silicon optical filter only makes THz wave generation unit produce passes through, by the THz wave of silicon optical filter successively
Collimate through the first paraboloidal mirror, the second paraboloidal mirror focuses on, the 3rd paraboloidal mirror collimation, paraboloidal mirror with holes focus on orthogonal
Electrode centers；
Second harmonic that second harmonic optical filter is inducted for only making THz wave and the secondary that described rotary DC electric field is inducted
Harmonic wave enters probe unit；
Terahertz polarization sheet is arranged between the first paraboloidal mirror and the second paraboloidal mirror, for improving the polarization of THz wave
The linearity, and for changing the polarization direction of THz wave；
The detection light that paraboloidal mirror with holes is additionally operable to make the second lens assemble passes through, and arrives crossed electrode center.
6. detector as claimed in claim 5, it is characterised in that probe unit includes: the 4th reflecting mirror, the 3rd lens, light
Electricity multiplier tube and lock-in amplifier；Wherein,
The second harmonic of entrance probe unit, after the 4th reflecting mirror reflection, is gathered photomultiplier tube by the 3rd lens；
The light intensity signal of the second harmonic that photomultiplier tube detection is incident；Lock-in amplifier locks first from described light intensity signal
Signal, and from the first signal, isolate the THz wave component in X+Y, X-Y direction, thus reconstruct the polarization of THz wave
State；Wherein, during the first signal is described light intensity signal, frequency of oscillation is equal to the component of crossed electrode bias voltage frequency.
7. the detector as described in claim 2-6 is arbitrary, it is characterised in that described LASER Light Source is that Ti∶Sapphire laser femtosecond laser is put
Big device.
8. a terahertz polarization detection method, it is characterised in that include step:
S1. laser is divided into pump light and the detection light of homology, utilizes pump light to produce THz wave；
S2. adjusting light path makes THz wave and detection light focus on crossed electrode center, and the secondary that generation THz wave is inducted is humorous
The second harmonic that the electric field that ripple and crossed electrode produce is inducted；Wherein, described crossed electrode produces the electricity of orthogonal direction distribution
?；
S3. the light intensity signal of the second harmonic that the detection second harmonic inducted of THz wave and described electric field are inducted, from described light
Strong signal isolates the THz wave component at described orthogonal direction, thus reconstructs the polarization state of THz wave.
9. method as claimed in claim 8, it is characterised in that step S2 also includes:
The first electrode in crossed electrode is arranged at X-direction, and the second electrode in crossed electrode is arranged at Y-direction；
The first square-wave signal E is inputted at the first electrodebias(Ω t), inputs the second square-wave signal E at the second electrodebias(Ωt+π/
2)；Wherein,
X-direction is vertical with Y-direction, and the first electrode and the second electrode are for producing the rotary DC electric field along X+Y, X-Y direction, Ω
Being the first square-wave signal and the angular frequency of the second square-wave signal, the frequency of the first square-wave signal and the second square-wave signal is described sharp
The 1/4 of light repetition rate；And
Described THz wave of isolating from described light intensity signal specifically includes at the component of described orthogonal direction: from described light intensity
Signal locks the first signal, and from the first signal, isolates the THz wave component in X+Y, X-Y direction；Wherein, first
Signal is the component that in described light intensity signal, frequency of oscillation is equal to crossed electrode bias voltage frequency.
10. method as claimed in claim 9, it is characterised in that described utilize pump light to produce THz wave particularly as follows: make pump
Pu light produces frequency doubled light, focal pumping light and frequency doubled light by bbo crystal and produces THz wave；And
Described method, after step S1, also includes: arrange silicon optical filter, for only making the THz wave of generation pass through；And
Described method upon step s 2, also includes: arrange second harmonic optical filter for the secondary only making THz wave induct
The second harmonic that harmonic wave and described rotary DC electric field are inducted passes through；And
Step S2 also includes: arrange terahertz polarization sheet, for improving the polarization linearity of THz wave, and for changing too
The polarization direction of Hertz wave.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610366074.6A CN106052873B (en) | 2016-05-27 | 2016-05-27 | THz wave coherence detector and terahertz polarization detection method based on gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610366074.6A CN106052873B (en) | 2016-05-27 | 2016-05-27 | THz wave coherence detector and terahertz polarization detection method based on gas |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN106052873A true CN106052873A (en) | 2016-10-26 |
| CN106052873B CN106052873B (en) | 2018-04-20 |
Family
ID=57174990
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201610366074.6A Active CN106052873B (en) | 2016-05-27 | 2016-05-27 | THz wave coherence detector and terahertz polarization detection method based on gas |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN106052873B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106483096A (en) * | 2016-11-25 | 2017-03-08 | 首都师范大学 | The system and method that laser excitation air plasma produces high intensity THz wave |
| CN109994917A (en) * | 2019-04-17 | 2019-07-09 | 中国科学院重庆绿色智能技术研究院 | A kind of wideband high field terahertz pulse radiation source generates and detection device |
| CN114136915A (en) * | 2021-11-05 | 2022-03-04 | 清华大学 | System and method for generating broadband terahertz waves with any polarization angle |
| CN115241725A (en) * | 2022-05-20 | 2022-10-25 | 中国人民解放军国防科技大学 | Terahertz balance detection system and method based on laser-air effect |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103261950A (en) * | 2010-03-04 | 2013-08-21 | 佳能株式会社 | Terahertz-wave generating element, terahertz-ave detecting element, and terahertz time-<wbr/>domain spectroscopy device |
| EP2770311A2 (en) * | 2013-02-21 | 2014-08-27 | Seiko Epson Corporation | Terahertz wave detection device, camera, imaging device, and measuring device |
| WO2015053138A1 (en) * | 2013-10-09 | 2015-04-16 | Canon Kabushiki Kaisha | Terahertz wave generating element and terahertz wave detecting element |
| CN105403178A (en) * | 2014-09-09 | 2016-03-16 | 丰田自动车株式会社 | Film thickness measuring device and film thickness measuring method |
-
2016
- 2016-05-27 CN CN201610366074.6A patent/CN106052873B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103261950A (en) * | 2010-03-04 | 2013-08-21 | 佳能株式会社 | Terahertz-wave generating element, terahertz-ave detecting element, and terahertz time-<wbr/>domain spectroscopy device |
| EP2770311A2 (en) * | 2013-02-21 | 2014-08-27 | Seiko Epson Corporation | Terahertz wave detection device, camera, imaging device, and measuring device |
| WO2015053138A1 (en) * | 2013-10-09 | 2015-04-16 | Canon Kabushiki Kaisha | Terahertz wave generating element and terahertz wave detecting element |
| CN105403178A (en) * | 2014-09-09 | 2016-03-16 | 丰田自动车株式会社 | Film thickness measuring device and film thickness measuring method |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106483096A (en) * | 2016-11-25 | 2017-03-08 | 首都师范大学 | The system and method that laser excitation air plasma produces high intensity THz wave |
| CN109994917A (en) * | 2019-04-17 | 2019-07-09 | 中国科学院重庆绿色智能技术研究院 | A kind of wideband high field terahertz pulse radiation source generates and detection device |
| CN114136915A (en) * | 2021-11-05 | 2022-03-04 | 清华大学 | System and method for generating broadband terahertz waves with any polarization angle |
| CN115241725A (en) * | 2022-05-20 | 2022-10-25 | 中国人民解放军国防科技大学 | Terahertz balance detection system and method based on laser-air effect |
| CN115241725B (en) * | 2022-05-20 | 2023-06-02 | 中国人民解放军国防科技大学 | Terahertz balance detection system and method based on laser-air effect |
Also Published As
| Publication number | Publication date |
|---|---|
| CN106052873B (en) | 2018-04-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Thyrhaug et al. | Identification and characterization of diverse coherences in the Fenna–Matthews–Olson complex | |
| JP6184109B2 (en) | Optical pumping magnetometer and magnetic sensing method | |
| CN106052873B (en) | THz wave coherence detector and terahertz polarization detection method based on gas | |
| McWilliams et al. | Observing mergers of nonspinning black-hole binaries | |
| CN101726362B (en) | Terahertz polarization analyzer and terahertz polarization measurement method | |
| Grandi et al. | Experimental quantum tomography of a homodyne detector | |
| WO2008037929A2 (en) | Electrical impedance tomography method and device | |
| CN106768335B (en) | A kind of non-linear spectral Method for Phase Difference Measurement | |
| CN106842095A (en) | Rf electric field proofreading method and device based on Rydberg atom quantum coherence effect | |
| Marquardt et al. | Quantum reconstruction of an intense polarization squeezed optical state | |
| Ghonge et al. | Reconstructing gravitational wave signals from binary black hole mergers with minimal assumptions | |
| Klimov et al. | Assessing the polarization of a quantum field from Stokes fluctuations | |
| CN103499392A (en) | TeraHertz-wave far-field detection super-diffraction resolution imaging instrument | |
| US9025163B2 (en) | Chirp modulation-based detection of chirped laser molecular dispersion spectra | |
| Meneghin et al. | Characterization of the coherent dynamics of bacteriochlorophyll a in solution | |
| Kinos et al. | Development and characterization of high suppression and high étendue narrowband spectral filters | |
| CN109633663A (en) | Quantum polarization lidar STOKES parameter detection accuracy analysis method | |
| Niehues et al. | A matter of symmetry: terahertz polarization detection properties of a multi-contact photoconductive antenna evaluated by a response matrix analysis | |
| Koukoulas et al. | A comparison between heterodyne and homodyne interferometry to realise the SI unit of acoustic pressure in water | |
| Bjorklund et al. | High Sensitivity Frequency Modulation Spectroscopy and the Path to Single Molecule Detection | |
| CN109238220B (en) | Method for measuring space rotation angle of object | |
| Rivas et al. | Measurement of ultrashort laser pulses with a time-dependent polarization state using the d-scan technique | |
| CN103471815A (en) | Method for simultaneously measuring S-polarized light reflectivity and P-polarized light reflectivity of high reflecting mirror | |
| CN206959990U (en) | A kind of self-reference Terahertz electro-optic sampling spectrointerferometer and measuring system | |
| Liu et al. | Polarisation-modulated photon-counting 3D imaging based on a negative parabolic pulse model |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |