CN108931495A - Terahertz time-domain spectroscopy synchronized measurement system and method - Google Patents
Terahertz time-domain spectroscopy synchronized measurement system and method Download PDFInfo
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- 238000005259 measurement Methods 0.000 title claims abstract description 39
- 238000001328 terahertz time-domain spectroscopy Methods 0.000 title claims abstract description 35
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- 238000001514 detection method Methods 0.000 claims abstract description 117
- 230000010287 polarization Effects 0.000 claims abstract description 70
- 239000013078 crystal Substances 0.000 claims description 34
- 230000003287 optical effect Effects 0.000 claims description 34
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 20
- 229910052710 silicon Inorganic materials 0.000 claims description 20
- 239000010703 silicon Substances 0.000 claims description 20
- 230000005855 radiation Effects 0.000 claims description 11
- 238000013519 translation Methods 0.000 claims description 11
- 238000012545 processing Methods 0.000 claims description 7
- 229910052594 sapphire Inorganic materials 0.000 claims description 6
- 239000010980 sapphire Substances 0.000 claims description 6
- 238000005086 pumping Methods 0.000 claims 1
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 238000001228 spectrum Methods 0.000 description 12
- 229910007709 ZnTe Inorganic materials 0.000 description 7
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- 238000005070 sampling Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
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- 241000122205 Chamaeleonidae Species 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation
- G01N21/3586—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation by Terahertz time domain spectroscopy [THz-TDS]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/061—Sources
- G01N2201/06113—Coherent sources; lasers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/12—Circuits of general importance; Signal processing
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Abstract
The present invention provides a kind of terahertz time-domain spectroscopy synchronized measurement system, including instrument room and it is mounted on the indoor laser light source module of the instrument, terahertz transmitter, detection beam splitter, terahertz polarization beam splitter, the first and second conjunction beam pieces and the first and second terahertz detection devices, wherein, the laser light source module includes laser and laser beam splitter, the laser light incident of the laser transmitting is divided into pump light and detection light on the laser beam splitter.The present invention also provides a kind of terahertz time-domain spectroscopy method for synchronously measuring.The present invention has while carrying out sample and reference measure, saves the time, reduces measurement unstable factor and laser fluctuation and the beneficial effect of circuit system interference.
Description
Technical field
The present invention relates to spectral measurement methods fields, and in particular to a kind of terahertz time-domain spectroscopy synchronized measurement system and side
Method.
Background technique
THz time domain spectrum technology is otherwise known as the THz-TDS (contracting of its English name time-domain spectroscopy
It writes).The D.H.Auston et al. of nineteen eighty-three AT&T Labs first proposed the principle of THz-TDS technology, because of its system knot
Structure is similar to Michelson's interferometer, so this method is referred to as relevant far red light spectrometry by them.1988,
The system that D.Grischkowsky of IBM et al. improves D.H.Auston really can be used widely, then
Formally it is named as THz time domain spectrum technology.Its principle is using the femtosecond laser irradiation source THz to excite to obtain broadband THz
Pulse enables THz pulse to pass through sample perpendicular to sample surfaces or reflect in sample surfaces by reasonable optical path,
Sample can thus be obtained to the transmission or reflection signal of THz, compare the signal and reference THz that without sample when is measured
Pulse signal, it will be able to the intensity value of the two THz pulses and the opposite variation of phase are obtained, to calculate the various of sample
Characteristic, including refractive index (multiple), dielectric constant and conductivity etc..
However, there are many technological deficiencies for existing measurement method.It is delivered in Zhang Liangliang et al. entitled
“Polarization sensitive terahertz time-domain spectroscopy for birefringent
Materials " (Applied Physics flash report, 94 (21): 211106-1-3,2009) in, it discloses a kind of for parsing the inclined of sample
The terahertz time-domain spectroscopy system for information of shaking, the shortcomings that system, are: (1), being referred to and Sample Scan, be done so respectively
It can be influenced by temperature and humidity variation in laboratory and the influence of the fuctuation within a narrow range of laser source power etc.；(2), sample
Time-consuming opposite twice for reference measure time-consuming of measurement, when being related to the measurement of a large amount of samples, data needed for asynchronous measurement are adopted
The increase for collecting the time becomes unfavorable factor (such as imaging applications and cohesion objects system).
In entitled " the Polarization-sensitive terahertz that E.Castro-Camus et al. is delivered
Detection by multicontact photoconductive receivers " (Applied Physics flash report, 86:254102
(4pp), 2005) in, disclose a kind of system of multi-electrode photoconductive antenna parsing material polarization.Terahertz dipole photoconduction day
Line emits linear polarization THz wave, and three electrode photoelectric lead antenna detect terahertz signal, and wherein three-electrode structure is respectively one
Electrode is grounded (shared electrode), other two mutually orthogonal electrode and electrode respectively with lock-in amplifier 1 and lock-in amplifier
It is connected, acquires the terahertz signal on two orthogonal direction of sample respectively.But the system building is relatively difficult, and due to too
The polarization of the quadrupole radiation phenomenon of Hertz doublet antenna, the THz wave of dipole photoconductive antenna transmitting is not that complete line is inclined
Vibration, so measurement error can be brought when measurement.
Therefore, there is an urgent need in the art to develop a kind of can synchronize sample and reference to scan to reduce error
Measuring system and method.
Summary of the invention
It is an object of the present invention to provide a kind of terahertz time-domain spectroscopy synchronized measurement system and method, it is able to solve sample survey
The technology that amount, which takes a long time, asynchronous measurement changes vulnerable to temperature and humidity influences and the fluctuation within a narrow range of laser source power influences is asked
Topic.
The present invention provides a kind of terahertz time-domain spectroscopy synchronized measurement system, including instrument room and is mounted in instrument room
Laser light source module, terahertz transmitter, detection beam splitter, terahertz polarization beam splitter, first and second close beam pieces with
And the first and second terahertz detection device, wherein
The laser light source module includes laser and laser beam splitter, and the laser light incident of the laser transmitting is described
On laser beam splitter, it is divided into pump light and detection light, pump light is radiated in the terahertz transmitter and generates THz wave, produces
Raw THz wave is divided into reference signal terahertz wave beam and sample signal THz wave by the terahertz polarization beam splitter
Beam, detection light are divided into the first detection light beam and the second detection light beam, reference signal THz wave by the detection beam splitter
Beam and the first detection light beam close beam through the first conjunction beam piece and obtain the first light beam to be detected, and sample signal terahertz wave beam and second are visited
It surveys light beam and obtains the second light beam to be detected through the second conjunction beam piece conjunction beam, the first and second terahertz detections device receives respectively
First light beam to be detected and the second light beam to be detected simultaneously export the first and second electric signals for carrying terahertz time-domain information.
Preferably, the laser beam splitter is polarization beam apparatus, and the detection beam splitter is non-polarizing beamsplitter, described
First and second conjunction beam pieces are high resistant silicon wafer.
Preferably, the terahertz transmitter includes photoconductive antenna, and the pump light is radiated at the photoconductive antenna
Upper generation photo-generated carrier after applying bias voltage appropriate on the photoconductive antenna, can be such that the photo-generated carrier adds
Speed movement generates electromagnetic fiele and to external radiation THz wave, and the THz wave of generation collects collimation by off axis paraboloidal mirror
After be incident on terahertz polarization beam splitter.
It preferably, further include the delay line module being located in front of the terahertz transmitter, for guaranteeing among translation stage
The equivalent optical path of pump light and detection light two-way when position, and closed between beam piece in the terahertz polarization beam splitter and second
It is placed with sample to be measured.
Preferably, the first terahertz detection device includes the first crystal detection and the first Terahertz differential detector,
The second terahertz detection device include the second crystal detection and the second Terahertz differential detector, the first light beam to be detected and
Second light beam to be detected is respectively focused on the first crystal detection and the second crystal detection, and passes through the first Terahertz difference respectively
The first electric signal and the second electric signal are exported after detector and the processing of the second Terahertz differential detector.
Preferably, the photoconductive antenna is the GaAs dipole photoconductive antenna of low-temperature epitaxy.
Preferably, the signal-to-noise ratio of each optical path in the synchronized measurement system is in 350:1 or more.
The present invention also provides a kind of terahertz time-domain spectroscopy method for synchronously measuring, including
Step 1, laser light incident are divided into pump light and detection light two-beam on laser beam splitter,
Step 2, pump light, which are radiated in terahertz transmitter, generates THz wave, and the THz wave of generation passes through Terahertz
Polarization beam apparatus is divided into reference signal terahertz wave beam and sample signal terahertz wave beam,
Step 3, detection light are divided into the first detection light beam and the second detection light beam by detection beam splitter,
Step 4, reference signal terahertz wave beam and the first detection light beam through the first conjunction beam piece close beam, and to obtain first to be detected
Light beam, sample signal terahertz wave beam and the second detection light beam close beam through the second conjunction beam piece and obtain the second light beam to be detected,
Step 5, the first and second terahertz detection devices receive the first light beam to be detected and the second light beam to be detected respectively
And export the first and second electric signals for carrying terahertz time-domain information.
Preferably, the laser beam splitter be polarization beam apparatus, step 1 further include by be placed in the laser beam splitter it
Preceding half-wave plate adjusts the intensity of the two-beam that the laser beam splitter is separated.
Preferably, the terahertz transmitter includes photoconductive antenna, and the step 2 includes being radiated at the pump light
Photo-generated carrier is generated on the photoconductive antenna, after applying bias voltage appropriate on the photoconductive antenna, institute can be made
It states photo-generated carrier and accelerates and generate electromagnetic fiele and to external radiation THz wave, and pass through the THz wave generated
Off axis paraboloidal mirror is incident on terahertz polarization beam splitter after collecting collimation.
It preferably, further include after step 1 and before step 2, by being located in front of the terahertz transmitter
The step of delay line module is come the equivalent optical path of pump light when guaranteeing translation stage middle position and detection light two-way, wherein in step
In rapid 4, sample to be measured, reference signal terahertz wave beam are placed between the terahertz polarization beam splitter and the second conjunction beam piece
It penetrates the first conjunction beam piece and second respectively with the sample signal terahertz wave beam for carrying sample message and closes beam piece, when the Terahertz
The sample to be measured used in the spectroscopic simultaneous measurement method of domain is with dichroic sapphire samples.
Preferably, the first terahertz detection device includes the first crystal detection and the first Terahertz differential detector,
The second terahertz detection device includes the second crystal detection and the second Terahertz differential detector, and in step 5, first is to be checked
It surveys light beam and the second light beam to be detected is respectively focused on the first crystal detection and the second crystal detection, and pass through first respectively too
The first and second electric signals are exported after hertz differential detector and the processing of the second Terahertz differential detector.
Terahertz time-domain spectroscopy synchronized measurement system of the invention has the following beneficial effects: compared with prior art with method
1, the present invention can carry out sample and reference measure simultaneously, save the time, reduce measurement unstable factor and laser
The interference of fluctuation and circuit system.
2, the present invention can be realized the synchronizing detection of two orthogonal direction of sample, make measurement result not by experiment room temperature and
The influence of the fuctuation within a narrow range of the influence and laser source power of humidity variation, keeps measurement result relatively reliable, can parse sample
The full polarization state of product.
3, two optical paths of synchronized measurement system of the invention show good similitude, can be used for executing synchronous background
It is measured with sample, therefore the fuctuation within a narrow range by temperature and humidity variation and laser source power is not influenced, wherein detector
The small difference of light efficiency can be calibrated when measuring and starting.
4, the quadrupole radiation generation due to Terahertz dipole antenna is avoided using terahertz polarization beam splitter in the present invention
Deviation linear polarization terahertz emission caused by error.
Detailed description of the invention
It will be briefly described attached drawing used in this application below, it should be apparent that, these attached drawings are for explaining only the invention
Design.
Fig. 1 is the structural schematic diagram of the terahertz time-domain spectroscopy synchronized measurement system of the embodiment of the present invention；
Fig. 2 is the structural schematic diagram of a specific example of measuring system shown in Fig. 1；
Fig. 3 is the flow chart of the terahertz time-domain spectroscopy method for synchronously measuring of the embodiment of the present invention；
Fig. 4 is the synchronous scanning Time Domain Spectrum in the terahertz time-domain spectroscopy method for synchronously measuring of the embodiment of the present invention；
Fig. 5 is the synchronous scanning frequency domain spectra in the terahertz time-domain spectroscopy method for synchronously measuring of the embodiment of the present invention；
Fig. 6 is that the synchronous reference and sample in the terahertz time-domain spectroscopy method for synchronously measuring of the embodiment of the present invention measure
The comparison diagram of amplitude and frequency relation.
Specific embodiment
Hereinafter, the implementation of terahertz time-domain spectroscopy synchronized measurement system and method for the invention is described with reference to the accompanying drawings
Example.
The embodiment recorded herein is specific specific embodiment of the invention, for illustrating design of the invention,
Be it is explanatory and illustrative, should not be construed as the limitation to embodiment of the present invention and the scope of the invention.Except what is recorded herein
Outside embodiment, those skilled in the art can also based on the claim of this application book and specification disclosure of that using aobvious and
The other technical solutions being clear to, these technical solutions include the embodiment recorded herein is made it is any it is obvious replacement and
The technical solution of modification.
The attached drawing of this specification be schematic diagram, aid in illustrating design of the invention, it is schematically indicated each section it is mutual
Relationship.It note that for the ease of clearly showing the relationship of each section of the embodiment of the present invention.The same or similar reference mark
Note is for indicating the same or similar part.
Fig. 1 is the structural schematic diagram of the terahertz time-domain spectroscopy synchronized measurement system of the embodiment of the present invention.As shown in Figure 1,
The synchronized measurement system includes instrument room's (not shown) and is mounted on the indoor laser light source module of instrument, terahertz sources
Device, detection beam splitter, terahertz polarization beam splitter, first and second close beam piece and the first and second terahertz detections dress
It sets.
Laser light source module includes laser and laser beam splitter, and the laser light incident of laser transmitting is in laser beam splitter
On, it is divided into pump light and detection light.Pump light, which is radiated in terahertz transmitter, generates THz wave, and the THz wave of generation is logical
It crosses terahertz polarization beam splitter and is divided into reference signal terahertz wave beam and sample signal terahertz wave beam.Light is detected by detection light
Beam splitter is divided into the first detection light beam and the second detection light beam.Reference signal terahertz wave beam and the first detection light beam are closed through first
Beam piece closes beam and obtains the first light beam to be detected, and sample signal terahertz wave beam and second detect light beam and obtain through the second conjunction beam piece conjunction beam
To the second light beam to be detected.First and second terahertz detection devices receive the first light beam to be detected and the second light to be detected respectively
Beam simultaneously exports the first and second electric signals for carrying terahertz time-domain information.
Preferably, laser beam splitter is polarization beam apparatus, and detection beam splitter is non-polarizing beamsplitter, and first and second close
Beam piece is high resistant silicon wafer.
In one embodiment, terahertz transmitter may include photoconductive antenna, and pump light is radiated on photoconductive antenna
Photo-generated carrier is generated, after applying bias voltage appropriate on photoconductive antenna, photo-generated carrier can be made to accelerate and generated
Electromagnetic fiele and to external radiation THz wave, the THz wave of generation is incident on too after off axis paraboloidal mirror collects collimation
On hertz polarization beam apparatus.
In one embodiment, which can also include the delay line module in front of terahertz transmitter, for protecting
The equivalent optical path of pump light and detection light two-way when demonstrate,proving translation stage middle position, and closed in terahertz polarization beam splitter and second
Sample to be measured is placed between beam piece.
In one embodiment, the first terahertz detection device may include that the first crystal detection and the first Terahertz difference are visited
Device is surveyed, the second terahertz detection device may include the second crystal detection and the second Terahertz differential detector, and first is to be detected
Light beam and the second light beam to be detected are respectively focused on the first crystal detection and the second crystal detection, and pass through the first terahertz respectively
Hereby the first electric signal and the second electric signal are exported after differential detector and the processing of the second Terahertz differential detector.
In the synchronized measurement system, the signal-to-noise ratio of each optical path is in 350:1 or more.
Fig. 2 is the structural schematic diagram of a specific example of measuring system shown in Fig. 1, which includes instrument room's (figure
In be not shown).It is closed it should be noted that cover can be used in above-mentioned instrument room, there are air inlet on cover, system can inflated with nitrogen
Or dry air further increases measurement accuracy so as to avoid absorption of the water to Terahertz in air.In addition, cover
Convenient for the fixed installation of other component.
As shown in Fig. 2, being provided with femto-second laser and polarization beam apparatus PBS (composition laser light source mould in instrument room
Block), the femtosecond laser of femto-second laser transmitting is incident on polarization beam apparatus PBS by reflecting mirror M1, so that light beam is divided into pump
Pu light and detection light two-beam；It is equipped with half-wave plate before polarization beam apparatus PBS, the polarizing film is for adjusting what polarization beam apparatus separated
The intensity of pump light and detection light two-beam.Wherein, pump light is the light beam for being used to generate THz wave through polarization beam apparatus,
Detecting light is then the light beam reflected through polarization beam apparatus for detecting THz wave intensity.
Femto-second laser (Laser) in the present invention is blue precious by the Chameleon Vision-S titanium for the company's production that is concerned with
Stone laser, adjustable extent are 650nm~1050nm, pulsewidth 100fs, repetition rate 82MHz.Specifically, in this example with
For wavelength is the femto-second laser of 800nm, chopper handle can be first passed through in the pump light generated after polarization beam apparatus PBS
The femtosecond laser of wavelength 800nm cuts into several kHz to the pulse laser of tens kHz, and lock-in amplifier is cooperated to realize the lock of optical signal
Fixed and amplification.Pump light is then using delay line module (Delay line) (front and back is provided with reflecting mirror M2 and M3), reflection
Microscope group (including reflecting mirror M4 and M5), lens L1 and the photoconductive antenna PCA as terahertz transmitter.The delay line module
Effect, which is the delay line module, gradually to be scanned with the movement of small step-length and is reconstructed the waveform of terahertz signal, it is necessary to be guaranteed
The equivalent optical path of pump light and detection light two-way light when translation stage middle position.After delay line module pump light can pass through
Lens L1 is focused light on the GaAs dipole photoconductive antenna PCA of low-temperature epitaxy and is generated photo-generated carrier, in photoconductive day
After applying bias voltage appropriate on line, photo-generated carrier can be made to accelerate and generate electromagnetic fiele and to external radiation Terahertz
Wave.After off axis paraboloidal mirror PM1 collects collimation, light beam is incident on terahertz polarization beam splitter the THz wave of radiation,
Terahertz polarization beam splitter can make THz wave be divided into reference signal terahertz wave beam t1 and sample signal terahertz wave beam at this time
T2 two-beam, adjusting terahertz polarization beam splitter makes the terahertz polarization of two-beam be respectively+45 ° and -45 °.Here, too
Sample to be measured is placed between hertz polarization beam apparatus and a silicon wafer.This two-beam pass through respectively a series of reflecting mirror M12,
After M13, M14 and off axis paraboloidal mirror PM2, PM3, terahertz wave beam t1 and the terahertz wave beam t2 of sample message is carried through each
From the silicon wafer (the first and second conjunction beam pieces) of optical path and then focus on corresponding ZnTe crystal (the first and second crystal detections).
At the same time, when detection optical path will also guarantee translation stage middle position with corresponding pump light equivalent optical path.By polarizing
The detection light of beam splitter PBS reflection is incident on lens L2 after multiple reflecting mirrors, and light is converged to unpolarized point by lens L2
On beam device BS, separated and reference signal terahertz wave beam t1 and sample signal terahertz wave beam t2 points by non-polarizing beamsplitter BS
Not corresponding reference signal detection light beam p1 (the first detection light beam) and sample signal detection light beam p2 (the second detection light beam).It
Respectively with reference signal terahertz wave beam t1 and sample signal terahertz wave beam t2 respective optical path silicon wafer (first and second
Close beam piece) at close beam, obtain the first light beam to be detected and the second light beam to be detected.Here, reference signal detection light beam p1 and sample
Product signal detection light beam p2 passes through lens L3 and lens L4 respectively and focuses on the corresponding ZnTe crystal (first and second of respective optical path
Crystal detection) on and its focus is overlapped with focus of the corresponding terahertz wave beam on ZnTe crystal.In addition, before each silicon wafer
The polarizing film and half of wave plate for being 800nm inserted with a wavelength, the effect of polarizing film P1, P2 and half-wave plate HWP2, HWP3 are
It filters out unwanted polarised light and adjusting polarization state keeps the terahertz signal finally obtained maximum.First and second light beams to be detected
Through after respective ZnTe crystal respectively by quarter-wave plate, lens L3 or L4, that wollaston prism is got to is right in optical path
(photodiode detector, wollaston prism and quarter-wave plate constitute the to the photodiode detector for the silicon substrate answered
One and the second terahertz detection device) on, and then by the reference electrical signal generated in photodiode detector and sample telecommunications
Number (the first and second electric signals), which is output in lock-in amplifier and information processing unit (not shown), carries out subsequent processing.When not having
When having THz wave generation, adjusts quarter-wave plate and the photodiode detector electric current of silicon substrate is made to be 0uA, due to terahertz
Hereby wave can change index ellipsoid of the 800nm light in ZnTe crystal, and this change degree is related with the intensity of THz wave,
So translation stage is cooperated gradually to scan and terahertz signal can be reconstructed when there is THz wave generation.
It should be noted that marking A1 to A6 to indicate aperture, the collimation for light in Fig. 2.
In further embodiment of the present invention, reference signal optical path include the detection light optical path that is set side by side with too
Hertz wave optical path.Specifically, the reference signal terahertz wave beam t1 generated after terahertz polarization beam splitter by THz wave with
The reference signal detection light beam p1 generated by detection light through non-polarizing beamsplitter BS converges to silicon wafer 1 jointly, then collinearly enters again
It is mapped to ZnTe crystal 1, and is incident on corresponding silicon substrate in optical path by quarter-wave plate, lens L3, wollaston prism
On photodiode detector 1, and then the reference signal generated in photodiode detector 1 is output to electro-optic sampling system
In 1 (not shown).
In further embodiment of the present invention, sample signal optical path also include the detection light optical path that is set side by side with
THz wave optical path.Specifically, the sample signal terahertz wave beam t2 generated after terahertz polarization beam splitter by THz wave
Silicon wafer 2 is converged to jointly with the reference signal detection light beam p2 generated by detection light through non-polarizing beamsplitter BS, it is then conllinear again
It is incident on ZnTe crystal 2, and is incident on corresponding silicon substrate in optical path by quarter-wave plate, lens L4, wollaston prism
Photodiode detector 2 on, and then the sample signal generated in photodiode detector 2 is output to electro-optic sampling system
In system 2.Wherein, sample to be measured is placed in sample signal optical path, and sample to be measured is preferably positioned at Terahertz
Between polarization beam apparatus and silicon wafer 2.
Wherein, electro-optic sampling system 1 is connect with extraneous computer with electro-optic sampling system 2, is provided in computer
Tera-hertz spectra data processing software, for dividing the data export in electro-optic sampling system 1 and electro-optic sampling system 2 with processing
Analysis, obtains the various optical performance parameters of sample.
In further embodiment of the present invention, silicon wafer 1 and silicon wafer 2 are high resistant silicon wafer.
In further embodiment of the present invention, photoconductive antenna is transmission-type GaAs dipole photoconductive antenna.
Terahertz time-domain spectroscopy synchronized measurement system of the invention can measure sample and reference signal simultaneously, while this is
System also can parse polarization, wherein needing to be arranged suitable translation stage scanning starting to guarantee that system reaches optimum performance, terminating
Position and scanning step.Scanning obtains first in the optical path of a branch of THz wave after sample being placed on terahertz polarization beam splitter
90 degree of sample rotates scannings, are obtained second group of sample in the plane vertical with the Terahertz direction of propagation by group sample and reference data
Product and reference data, first group of comparison, second group of data obtain the Terahertz intensity and phase of sample on two orthogonal directions etc.
Information operates available information relevant to sample permittivity by Fast Fourier Transform etc., such as the frequency domain spectra of sample,
Transmission spectrum, spectrum of refractive index, absorption spectra etc..Because these information on two orthogonal direction of sample are measured, it is possible thereby to parse
The full polarization state information of sample.
In other embodiments, THz wave can be generated using other methods, for example, passing through various types of crystal
Optical rectification effect or skin effect generate THz wave.Meanwhile THz wave can be detected using other methods, such as use
The photoconductive antennas of various structures detects THz wave.
In another embodiment, can be before terahertz polarization beam splitter after off axis paraboloidal mirror PM1, then place one
A terahertz polarization piece, to ensure that the polarization state of light of Terahertz dipole photoconductive antenna sending is linear polarization.
In further embodiment of the present invention, the signal-to-noise ratio of each optical path in synchronized measurement system 350:1 with
On, setting system in this way is relatively stable.
In addition, including the following steps: the present invention also provides a kind of terahertz time-domain spectroscopy method for synchronously measuring
Step 1, laser light incident are divided into pump light and detection light two-beam on laser beam splitter,
Step 2, pump light, which are radiated in terahertz transmitter, generates THz wave, and the THz wave of generation passes through Terahertz
Polarization beam apparatus is divided into reference signal terahertz wave beam and sample signal terahertz wave beam,
Step 3, detection light are divided into the first detection light beam and the second detection light beam by detection beam splitter,
Step 4, reference signal terahertz wave beam and the first detection light beam through the first conjunction beam piece close beam, and to obtain first to be detected
Light beam, sample signal terahertz wave beam and the second detection light beam close beam through the second conjunction beam piece and obtain the second light beam to be detected,
Step 5, the first and second terahertz detection devices receive the first light beam to be detected and the second light beam to be detected respectively
And export the first and second electric signals for carrying terahertz time-domain information.
In further embodiment of the present invention, laser beam splitter is polarization beam apparatus, and step 1 further includes by being placed in laser
Half-wave plate before beam splitter adjusts the intensity of the two-beam that laser beam splitter is separated.
In further embodiment of the present invention, terahertz transmitter includes photoconductive antenna, and step 2 includes shining pump light
It penetrates and generates photo-generated carrier on photoconductive antenna, after applying bias voltage appropriate on photoconductive antenna, photoproduction can be made to carry
Stream accelerates generation electromagnetic fiele and to external radiation THz wave, and makes the THz wave generated by off-axis parabolic
Face mirror is incident on terahertz polarization beam splitter after collecting collimation.
It further include after step 1 and before step 2, by being located at Terahertz in further embodiment of the present invention
Delay line module in front of transmitter is come the step of pump light when guaranteeing translation stage middle position and the equivalent optical path of detection light two-way
Suddenly, wherein in step 4, place sample to be measured between terahertz polarization beam splitter and the second conjunction beam piece, reference signal is too
Hertz wave beam and the sample signal terahertz wave beam for carrying sample message penetrate the first conjunction beam piece and second respectively and close beam piece, terahertz
The sample to be measured hereby used in time-domain spectroscopy method for synchronously measuring is sapphire samples.
In further embodiment of the present invention, the first terahertz detection device includes the first crystal detection and the first Terahertz
Differential detector, the second terahertz detection device includes the second crystal detection and the second Terahertz differential detector, in step 5,
First light beam to be detected and the second light beam to be detected are respectively focused on the first crystal detection and the second crystal detection, and are passed through respectively
The first and second electric signals are exported after crossing the first Terahertz differential detector and the processing of the second Terahertz differential detector.
Terahertz time-domain spectroscopy method for synchronously measuring of the invention can measure sample and reference signal simultaneously, while this is
System also can parse polarization, wherein needing to be arranged suitable translation stage scanning starting to guarantee that system reaches optimum performance, terminating
Position and scanning step.Scanning obtains first in the optical path of a branch of THz wave after sample being placed on terahertz polarization beam splitter
The comparison diagram of amplitude and frequency relation when group sample and reference data such as Fig. 6 is synchro measure.It hangs down with the Terahertz direction of propagation
90 degree of sample rotates scannings are obtained second group of sample and reference data in straight plane, first group of comparison, second group of data obtain
To the information such as Terahertz intensity of the sample on two orthogonal directions and phase, operated by Fast Fourier Transform etc. available
Information relevant to sample permittivity, for example, Time Domain Spectrum, frequency domain spectra, transmission spectrum, spectrum of refractive index, absorption spectra etc..This hair
Bright selection sapphire measures sample, is illustrated in figure 4 the Time Domain Spectrum of sapphire samples, is illustrated in figure 5 the frequency of sapphire samples
Domain spectrum.Because measuring these information on two orthogonal direction of sample, it is possible thereby to parse the full polarization state information of sample.
In further embodiment of the present invention, silicon wafer 1 and silicon wafer 2 are high resistant silicon wafer.
In further embodiment of the present invention, photoconductive antenna is transmission-type GaAs dipole photoconductive antenna.
In other embodiments, before sample being placed on terahertz polarization beam splitter, after off axis paraboloidal mirror PM1,
Scanning obtains two groups of terahertz signal data of two orthogonal direction of sample, further takes out Sample Scan and obtains corresponding two groups of reference numbers
According to.Relatively more corresponding reference and sample data, it can the sample Terahertz information on two orthogonal direction of sample is obtained, so
It can parse the full polarization state information of sample.In this way, realizing the synchronization of the polarization parsing on two orthogonal direction of sample.
Terahertz time-domain spectroscopy method for synchronously measuring of the invention can carry out sample and reference measure simultaneously, when saving
Between, reduce the interference of measurement unstable factor and laser fluctuation and circuit system；It can be realized the synchronization of two orthogonal direction of sample
Detection influences measurement result and the shadow of the fuctuation within a narrow range of laser source power by temperature and humidity variation in laboratory
It rings, keeps measurement result relatively reliable, can parse the full polarization state of sample；Two optical paths of measurement method show good phase
Like property, can be used for executing synchronous reference and sample measurement, therefore can not by temperature and humidity change and source power it is small size
The small difference of the influence of fluctuation, detector light efficiency can be calibrated when measuring and starting；The present invention uses terahertz polarization point
Beam device is avoided due to caused by the terahertz emission of the deviation linear polarization of the quadrupole radiation generation of Terahertz dipole antenna
Error.
Terahertz synchronized measurement system and method for the invention for example can be applied to following situations: measure material in a synchronous manner
The quadrature component for expecting electric field polarization, compared with the full polarization of accurate Analysis anisotropic material, thus with such as birefringence, optical activity
And circular dichroism, the anisotropic materials such as linear dichroism are corresponding.
The embodiment of terahertz time-domain spectroscopy synchronized measurement system and method for the invention is illustrated above.It is right
It can be according to the feature of above-mentioned disclosure in the specific features of terahertz time-domain spectroscopy synchronized measurement system and method for the invention
Effect is specifically designed, these designs are that those skilled in the art can be realized.Moreover, each technology of above-mentioned disclosure is special
Sign be not limited to it is disclosed with other feature combination, those skilled in the art can also purpose according to the present invention carry out each skill
Other combinations between art feature, be subject to realize the present invention purpose.
Claims (10)
1. a kind of terahertz time-domain spectroscopy synchronized measurement system, including instrument room and it is mounted on the indoor laser light source mould of instrument
Block, terahertz transmitter, detection beam splitter, terahertz polarization beam splitter, first and second close beam piece and first and second
Terahertz detection device, wherein
The laser light source module includes laser and laser beam splitter, and the laser light incident of the laser transmitting is in the laser
On beam splitter, it is divided into pump light and detection light, pump light is radiated in the terahertz transmitter and generates THz wave, generation
THz wave is divided into reference signal terahertz wave beam and sample signal terahertz wave beam by the terahertz polarization beam splitter, visits
It surveys light and is divided into the first detection light beam and second by the detection beam splitter and detect light beam, reference signal terahertz wave beam and the
One detection light beam closes beam through the first conjunction beam piece and obtains the first light beam to be detected, sample signal terahertz wave beam and the second detection light beam
Close beam through the second conjunction beam piece and obtain the second light beam to be detected, the first and second terahertz detections device receive respectively first to
Detection light beam and the second light beam to be detected simultaneously export the first and second electric signals for carrying terahertz time-domain information.
2. terahertz time-domain spectroscopy synchronized measurement system according to claim 1, wherein the laser beam splitter is polarization
Beam splitter, the detection beam splitter are non-polarizing beamsplitter, and the first and second conjunctions beam piece is high resistant silicon wafer.
3. terahertz time-domain spectroscopy synchronized measurement system according to claim 1 or 2, wherein the terahertz transmitter
Including photoconductive antenna, the pump light is radiated on the photoconductive antenna and generates photo-generated carrier, in the photoconductive day
After applying bias voltage appropriate on line, can make the photo-generated carrier accelerate generate electromagnetic fiele and to external radiation too
The THz wave of Hertz wave, generation is incident on terahertz polarization beam splitter after off axis paraboloidal mirror collects collimation.
4. terahertz time-domain spectroscopy synchronized measurement system according to claim 1 or 2 further includes being located at the Terahertz to send out
Delay line module in front of emitter, the equivalent optical path of pump light and detection light two-way when for guaranteeing translation stage middle position, and
And sample to be measured is placed between the terahertz polarization beam splitter and the second conjunction beam piece.
5. terahertz time-domain spectroscopy synchronized measurement system according to claim 1 or 2, wherein first Terahertz is visited
Surveying device includes the first crystal detection and the first Terahertz differential detector, and the second terahertz detection device includes the second spy
It surveys crystal and the second Terahertz differential detector, the first light beam to be detected and the second light beam to be detected is respectively focused on the first detection
On crystal and the second crystal detection, and handled respectively by the first Terahertz differential detector and the second Terahertz differential detector
After export the first electric signal and the second electric signal.
6. a kind of terahertz time-domain spectroscopy method for synchronously measuring, including
Step 1, laser light incident are divided into pump light and detection light two-beam on laser beam splitter,
Step 2, pump light, which are radiated in terahertz transmitter, generates THz wave, and the THz wave of generation passes through terahertz polarization
Beam splitter is divided into reference signal terahertz wave beam and sample signal terahertz wave beam,
Step 3, detection light are divided into the first detection light beam and the second detection light beam by detection beam splitter,
Step 4, reference signal terahertz wave beam and the first detection light beam close beam through the first conjunction beam piece and obtain the first light beam to be detected,
Sample signal terahertz wave beam and the second detection light beam close beam through the second conjunction beam piece and obtain the second light beam to be detected,
Step 5, the first and second terahertz detection devices receive the first light beam to be detected and the second light beam to be detected and defeated respectively
The first and second electric signals of terahertz time-domain information are carried out.
7. terahertz time-domain spectroscopy method for synchronously measuring according to claim 6, wherein the laser beam splitter is polarization
Beam splitter, step 1 further include adjusting the laser beam splitter by the half-wave plate before being placed in the laser beam splitter to divide
The intensity of two-beam out.
8. terahertz time-domain spectroscopy method for synchronously measuring according to claim 6 or 7, wherein the terahertz transmitter
Including photoconductive antenna, the step 2 includes being radiated at the pump light on the photoconductive antenna to generate photo-generated carrier,
After applying bias voltage appropriate on the photoconductive antenna, the photo-generated carrier can be made to accelerate and generate time-varying electromagnetism
And to external radiation THz wave, and make generate THz wave by off axis paraboloidal mirror collect collimation after be incident on terahertz
Hereby on polarization beam apparatus.
9. terahertz time-domain spectroscopy method for synchronously measuring according to claim 6 or 7, further include after step 1 and
Before step 2, by being located at the delay line module in front of the terahertz transmitter come pumping when guaranteeing translation stage middle position
The step of equivalent optical path of light and detection light two-way, wherein in step 4, closed in the terahertz polarization beam splitter and second
Sample to be measured, reference signal terahertz wave beam and the sample signal terahertz wave beam point for carrying sample message are placed between beam piece
First it Tou Guo not close beam piece and second and close beam piece, the sample to be measured used in the terahertz time-domain spectroscopy method for synchronously measuring
For sapphire samples.
10. terahertz time-domain spectroscopy method for synchronously measuring according to claim 6 or 7, wherein first Terahertz is visited
Surveying device includes the first crystal detection and the first Terahertz differential detector, and the second terahertz detection device includes the second spy
Survey crystal and the second Terahertz differential detector, in step 5, the first light beam to be detected and the second light beam to be detected are respectively focused on
On first crystal detection and the second crystal detection, and visited respectively by the first Terahertz differential detector and the second Terahertz difference
The first and second electric signals are exported after surveying device processing.
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