CN109187345A - A kind of trigger signal generator for ultrafast time-domain spectroscopy system - Google Patents
A kind of trigger signal generator for ultrafast time-domain spectroscopy system Download PDFInfo
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- CN109187345A CN109187345A CN201811045844.2A CN201811045844A CN109187345A CN 109187345 A CN109187345 A CN 109187345A CN 201811045844 A CN201811045844 A CN 201811045844A CN 109187345 A CN109187345 A CN 109187345A
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- 238000004611 spectroscopical analysis Methods 0.000 title claims abstract description 27
- 238000005086 pumping Methods 0.000 claims abstract description 13
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- 230000003287 optical effect Effects 0.000 abstract description 11
- 238000001228 spectrum Methods 0.000 abstract description 7
- 230000005611 electricity Effects 0.000 abstract description 6
- 230000008901 benefit Effects 0.000 abstract description 3
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- 238000013480 data collection Methods 0.000 description 4
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- 238000006243 chemical reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
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- 238000010521 absorption reaction Methods 0.000 description 1
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- 239000008358 core component Substances 0.000 description 1
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- 230000009897 systematic effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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- G—PHYSICS
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- 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
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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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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Abstract
The invention discloses a kind of trigger signal generators for ultrafast time-domain spectroscopy system, it is concerned with principle using laser spectrum, optical trigger signal is generated when the pumping laser and two laser pulse of exploring laser light of ultrafast time-domain spectroscopy system are overlapped, optical trigger signal is then converted into electricity trigger signal by high-speed photodiode；Again successively by operational amplifier, high-pass filter, Schmidt trigger processing after be sent into the trigger signal in ultrafast time-domain spectroscopy system as signal acquiring system, available highly stable THz time domain spectrum；High-speed photodiode, operational amplifier, high-pass filter, Schmidt trigger are all encapsulated on same PCB by this, realize the function that two column light pulses being periodically overlapped are changed into square-wave signal synperiodic, that rising edge is sharp keen.The device have the advantages that integrated level is high, structure is simple, bandwidth is high, rising edge is sharp keen, it is easy adjust, performance it is stable.
Description
Technical field
The invention belongs to Terahertz Technology fields, and in particular to a kind of trigger signal hair for ultrafast time-domain spectroscopy system
Raw device.
Background technique
Present ultrafast time-domain spectroscopy system realizes the high speed acquisition of time-domain spectroscopy using asynchronous-sampling principle.Based on asynchronous
The ultrafast time-domain spectroscopy system of the Terahertz of sampling has used the slightly differentiated femto-second laser of two repetition rates, repetition all the way
Frequency is f, and as direct impulse, another way femto-second laser pulse repetition rate is f+ Δ f, as pumping pulse, and by high band
Wide feedback electronics control its repetition rate.Thus two femtosecond pulse repetition rate is mentioned there are the difference that one is Δ f
The time delay of pumping pulse and probe pulse, scan period T can be provided by Δ f, i.e. T=1/ Δ f.When ultrafast Terahertz
Domain spectroscopic system sampling principle is as shown in Figure 1, Δ f=10kHz, T=100 μ s in figure.
Since the repetition rate of pumping pulse and direct impulse is not identical, so they are asynchronous, but every certain
Time will be overlapped once.Whenever pumping pulse and direct impulse are overlapped primary, present scan end cycle is just indicated, it is next
Scan period starts.Control system should just generate a high level pulse signal, as trigger signal (triggering as shown in figure 1
Signal).The cycle T of trigger signal=1/ Δ f.Time T is also the sampling period of signal acquiring system, and signal acquiring system receives
Start to acquire data to a trigger signal, terminate this acquisition after receiving next trigger signal, saves data, and open
Begin the acquisition of next cycle data.So trigger signal is most important to the acquisition of signal.
It is generated there are two types of trigger signal modes now: being based on optical generation method, be based on electricity production method.
Based on optical generation method, there are two types of modes: 1, two-photon detector method, two-photon absorption effect only can be two
It is generated under the light laser of road, so two-way light laser can cause photodiode greatly to damage, detector is easy to damage.2, frequency multiplication
The method of crystal, the method are the frequency multiplication principles using frequency-doubling crystal, but the low anti-interference of transformation efficiency is poor, encapsulation is difficult, makes
With inconvenience.
Based on electricity production method, the method is that two pulsed optical signals are first converted to two column separation electric impulse signal, so
Trigger signal is converted by two column separation electric signals by trigger circuit again afterwards.Disadvantage: stability is poor in high-frequency circuit, by
It abandons.
Summary of the invention
In view of this, the object of the present invention is to provide a kind of trigger signal generator for ultrafast time-domain spectroscopy system,
Be concerned with principle using laser spectrum, can produce rising edge it is sharp keen, it is easy adjust, the touching that structure is simple, bandwidth is high and performance is stable
It signals.
A kind of trigger signal generator for ultrafast time-domain spectroscopy system, including photodiode, high-pass filter, across
Impedance amplifier, operational amplifier and Schmidt trigger；
The photodiode receives the pumping laser of ultrafast time-domain spectroscopy system and the coherent pulse signal of exploring laser light,
And it is converted into electric signal；
The high-pass filter is used to filter out the direct current signal in the electric signal of photodiode output；
The trans-impedance amplifier is used to the current signal that photodiode exports being converted to voltage signal, and removes signal
In high-frequency noise；
The voltage signal that the operational amplifier is used to export trans-impedance amplifier is further amplified；
The Schmidt trigger connects after operational amplifier, for signal to be become the sharp keen square wave of rising edge
Thus signal obtains trigger signal.
Preferably, the bandwidth of the photodiode is 1GHz or more.
Preferably, photodiode of the photodiode using the model ET-400 of EOT company.
Preferably, the core devices model OPA657 of the trans-impedance amplifier and operational amplifier.
Preferably, the photodiode, operational amplifier, high-pass filter and Schmidt trigger are all encapsulated in together
On one piece of PCB.
The invention has the following beneficial effects:
A kind of trigger signal generator for ultrafast time-domain spectroscopy system of the invention utilizes the relevant original of laser spectrum
Reason generates optical trigger signal when the pumping laser and two laser pulse of exploring laser light of ultrafast time-domain spectroscopy system are overlapped, so
Optical trigger signal is converted into electricity trigger signal by high-speed photodiode afterwards；Successively pass through operational amplifier, high pass again
Filter, Schmidt trigger processing after be sent into the trigger signal in ultrafast time-domain spectroscopy system as signal acquiring system,
Available highly stable THz time domain spectrum；This is by high-speed photodiode, operational amplifier, high-pass filter, Schmidt
Trigger is all encapsulated on same PCB, and two column light pulses being periodically overlapped are changed into that synperiodic, rising edge is sharp by realization
The function of the square-wave signal of benefit.The device is high with integrated level, structure is simple, bandwidth is high, rising edge is sharp keen, easy adjusting, performance
Stable advantage.
Detailed description of the invention
Fig. 1 is existing asynchronous-sampling time-domain spectroscopy systematic sampling schematic illustration；
Fig. 2 is the functional block diagram of trigger signal generator of the invention；
Optical trigger signal is converted to electricity trigger signal for high speed diode of the present invention by Fig. 3；
Trigger signal when Fig. 4 is Δ f=1430KHz；
Fig. 5 is the output signal of operational amplifier (Amp)；
Fig. 6 is the electric pulse of time domain amplification；
Fig. 7 is Schmidt trigger signal
Fig. 8 is the structural schematic diagram applied after trigger signal generator of the invention；
Fig. 9 is the output signal of Schmidt trigger output end SMA-J in trigger signal generator of the invention；
The ultrafast time-domain spectroscopy system that Figure 10 is Fig. 8 is adopted using the trigger signal that trigger signal generator of the invention generates
Collect obtained signal time-domain diagram.
Specific embodiment
The present invention will now be described in detail with reference to the accompanying drawings and examples.
As shown in Fig. 2, a kind of trigger signal generator for ultrafast time-domain spectroscopy system of the invention, light receiving element
A mainly high-speed photodiode PD, this high-speed photodiode resistance when receiving light pulse can become smaller, and work as light intensity
When less than largest light intensity, the bigger resistance of light intensity is smaller.Its bandwidth is 5 times or more of laser repetition rate.In the present invention
The bandwidth requirement of high-speed photodiode is 1GHz or more, and the embodiment of the present invention uses the light of the model ET-400 of EOT company
Electric diode.High-speed photodiode is powered by DCBISA+ feeder ear, is powered in this example with 5V.Two beams are swashed first when use
Combiner interferes effect, forms optical trigger signal.This high-speed photodiode will complete optical trigger signal to electricity
The conversion of trigger signal.
It is specifically described the principle for generating trigger signal below:
Here two beam femtosecond pulses are reduced to two beam monochrome Gauss femtosecond pulses, wherein a branch of is pumping pulse, it is a branch of
For direct impulse.The electric field of two beam laser can be expressed as following form
Wherein Em (t), Es (t) are respectively pumping pulse electric field and direct impulse electric field, two beam Gauss femtosecond pulse of Em, Es
The peak value of electric field, T0 are the pulsewidths of pulse, and ω is the angular frequency of Gauss femtosecond pulse electric field, and τ is direct impulse relative to pumping
The delay time of pulse.The initial phase of two beam Gauss femtosecond pulse electric fields is defaulted hereinAnd electric field polarization direction
It is identical.
Coherent superposition is generated when two beam Gauss femtosecond pulses meet, total electric field can be expressed as form after superposition:
Total electric field energy can be expressed as form after two beam Gauss femtosecond pulse coherent superpositions:
It is hereby achieved that the light intensity after two beam Gauss femtosecond pulse coherent superpositions can be expressed as form:
Above formula each single item is redefined:
Wherein A (τ) is light intensity when relevant effect does not occur for two pulses, and B (τ) is two pulse coherence item light intensity.Its A (τ)
It can be further rewritten as A (τ)=C (τ)+D (τ),For pumping pulse energy,To detect energy.
Then formula (1-5) can be rewritten into:
I (τ)=A (τ)=B (τ) (1-8)
Formula (1-6), (1-7) can be calculated, as τ=0, A (0)=B (0).That is two beam Gauss femtosecond pulse phases
It does twice that superimposed light intensity is non-coherent superposition light intensity.The response time of photodiode used in light intensity detection
(hundred ps magnitudes) is much larger than pulse width.So the energy detected when the relative time-delay of two pulses is by 0 is most strong, it is
The complete coherent energy I (0) of spectrum in wave packet, i.e., photodiode response impulse is most strong at this time.As two pulse relative times prolong
Slow increase, photodiode response impulse die down.When relative time-delay is up to hundred femtosecond magnitudes to tens picoseconds, at this time two
Pulse is without relevant effect, i.e. B (τ)=0, but this two pulse still can not be identified in detector at this time, so detecting two pulses
Incoherent gross energy, i.e. A (τ), but with the increase of relative time-delay, detector response can be smaller.When two pulsion phase clock synchronizations
Between delay when increasing to several hundred picoseconds, detector can separately detect out two pulse energy C (τ), D (τ) at this time.Detection at this time
Device response intensity is minimum.Gu the period of two pulses with periodical time delay can be detected with the method.
As shown in figure 3, trigger signal is the AC signal for being added to direct current signal, so after high-speed photodiode
Face is added to high-pass filter (HPF), to remove direct current signal.This high-speed photodiode carries out photoelectric conversion with high
Bandwidth can produce the stabilization trigger signal of up to 1430kHz in the present invention, as shown in Figure 4.
Trans-impedance amplifier (TIA) and operational amplifier (Amp) are linked after high-pass filter, high speed diode is generated
Trigger signal amplifies.Trans-impedance amplifier (TIA) is the front-end amplifier of high-speed photodiode, is used for high speed optoelectronic two
The output electric current (I) of pole pipe is converted to voltage (VOUT).Trans-impedance amplifier is the feedback resistance for utilizing operational amplifier both ends
(RF), according to Ohm's law: electric current (I) is converted to voltage (VOUT) by voltage (VOUT)=electric current (I) × feedback resistance (RF).
And this trans-impedance amplifier (TIA) has certain bandwidth, can remove the noise of high frequency.Operational amplifier (Amp) is that have
The low noise voltage signal of trans-impedance amplifier (TIA) output is further amplified in the very high speed amplifier of high-amplification-factor.Make it
The voltage signal of output can satisfy the requirement of Schmidt trigger below.The core component of this two amplifiers is OPA657,
And the bandwidth for being provided with them is 550MHz.The output signal of operational amplifier (Amp) is as shown in Figure 5.
The signal of the output of operational amplifier (Amp) is periodic electric impulse signal in fact, since electric impulse signal is
It is successively shone in generation by multiple light pulses, so being an electronic impulse envelope shape after true time-domain signal amplification
Formula, as shown in Figure 6.
What data collection system identified is the rising edge of trigger signal, but signal has multiple rising edges, is directly used in number
According to acquisition triggering it will cause triggering disorder.So the signal of the output of operational amplifier (Amp) is inputted schmidt trigger
Device, i.e. Schmitt trigger.This signal, it is sharp keen to be become a rising edge by the threshold voltage for adjusting Schmidt trigger
Square-wave signal, as shown in Figure 7.
Schmidt trigger signal is exported by signal output end SMA-J, and Schmidt trigger signal output end is i.e. thus
The output end of trigger signal generator.
Trigger signal generator of the invention can be put into ultrafast time-domain spectroscopy system and use, ultrafast time-domain spectroscopy system knot
Structure schematic diagram is as shown in Figure 8.Two femto-second lasers are used in this system, a pumping laser the most is used to generate THz signal,
Another is used to detect THz signal.The repetition rate of two beam femtosecond laser lasers is different, and the difference of repetition rate is Δ f, so
The laser pulse of two lasers can be periodically overlapped, and the period is 1/ Δ f.This is the coincidence of light pulse, triggering letter of the invention
Number detector is sought to detect two laser light pulses at the time of be overlapped.I.e. when two light pulses are overlapped, trigger signal detector
A high level signal should be exported, when two light pulses are not overlapped, maintains low level state.This trigger signal generator output letter
Number rising edge occur frequency be Δ f.Light pulse and detecting optical pulses are pumped in ultrafast time-domain spectroscopy system by closing beam
It is radiated in the high-speed photodiode of trigger signal detector later.Adjust the light that two beams are radiated in high-speed photodiode
Beam average intensity is equal, and be all saturated light intensity for high-speed photodiode 1/4.The output signal of trigger signal generator at this time
For periodic square-wave signal, the period is identical as the time domain period of two column envelopes, i.e. the difference of the repetition rate of two column pulses
It is reciprocal.This signal is the trigger signal of data collection system.The output signal of trigger signal generator is as shown in Figure 9.
This trigger signal is input to data collection system, the trigger signal as data collection system.Data are told to acquire
The end in this period of system and the beginning of next cycle, and save the data in this period.Integral is utilized in multiple measurement
Method of average trigger signal stable when obtaining signal may insure that position of the THz signal in whole cycle is constant, to last THz
The precision of signal has vital effect.
THz signal is acquired with the trigger signal that this trigger signal detector generates, signal time-domain diagram is as shown in Figure 10.From
The THz time domain spectrum that Figure 10 can be seen that the trigger signal that this trigger signal generator generates is acquired as trigger source is very steady
It is fixed.
In conclusion the above is merely preferred embodiments of the present invention, being not intended to limit the scope of the present invention.
All within the spirits and principles of the present invention, any modification, equivalent replacement, improvement and so on should be included in of the invention
Within protection scope.
Claims (5)
1. a kind of trigger signal generator for ultrafast time-domain spectroscopy system, which is characterized in that including photodiode, high pass
Filter, trans-impedance amplifier, operational amplifier and Schmidt trigger；
The photodiode receives the pumping laser of ultrafast time-domain spectroscopy system and the coherent pulse signal of exploring laser light, and turns
Turn to electric signal；
The high-pass filter is used to filter out the direct current signal in the electric signal of photodiode output；
The trans-impedance amplifier is used to the current signal that photodiode exports being converted to voltage signal, and removes in signal
High-frequency noise；
The voltage signal that the operational amplifier is used to export trans-impedance amplifier is further amplified；
The Schmidt trigger connects after operational amplifier, believes for signal to be become the sharp keen square wave of a rising edge
Number, thus obtain trigger signal.
2. a kind of trigger signal generator for ultrafast time-domain spectroscopy system as described in claim 1, which is characterized in that institute
The bandwidth for stating photodiode is 1GHz or more.
3. a kind of trigger signal generator for ultrafast time-domain spectroscopy system as claimed in claim 2, which is characterized in that institute
Photodiode is stated using the photodiode of the model ET-400 of EOT company.
4. a kind of trigger signal generator for ultrafast time-domain spectroscopy system as described in claim 1, which is characterized in that institute
State the core devices model OPA657 of trans-impedance amplifier and operational amplifier.
5. a kind of trigger signal generator for ultrafast time-domain spectroscopy system as described in claim 1, which is characterized in that institute
Photodiode, operational amplifier, high-pass filter and Schmidt trigger is stated all to be encapsulated on same PCB.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4475396A (en) * | 1982-07-16 | 1984-10-09 | General Electric Company | Method of determining ultrasonic attenuation of tissue using reflective tomographic reconstruction |
| CN105891144A (en) * | 2016-03-31 | 2016-08-24 | 上海理工大学 | Terahertz scanning system and method |
| CN106442378A (en) * | 2016-09-26 | 2017-02-22 | 上海理工大学 | Device for improving test accuracy of spectrum absorbance on basis of terahertz optical combs |
| CN206226389U (en) * | 2016-11-21 | 2017-06-06 | 国家电网公司 | The frequency selection circuit that active RLC narrow-band pass filters are combined with Schmidt trigger |
-
2018
- 2018-09-07 CN CN201811045844.2A patent/CN109187345B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4475396A (en) * | 1982-07-16 | 1984-10-09 | General Electric Company | Method of determining ultrasonic attenuation of tissue using reflective tomographic reconstruction |
| CN105891144A (en) * | 2016-03-31 | 2016-08-24 | 上海理工大学 | Terahertz scanning system and method |
| CN106442378A (en) * | 2016-09-26 | 2017-02-22 | 上海理工大学 | Device for improving test accuracy of spectrum absorbance on basis of terahertz optical combs |
| CN206226389U (en) * | 2016-11-21 | 2017-06-06 | 国家电网公司 | The frequency selection circuit that active RLC narrow-band pass filters are combined with Schmidt trigger |
Non-Patent Citations (3)
| Title |
|---|
| YING-KHAI TEH等: "A bipolar output voltage pulse transformer boost converter with charge pump assisted shunt regulator for thermoelectric energy harvesting", 《ANALOG INTEGE CIRC PROCESS》 * |
| 于东钰等: "太赫兹微弱信号检测系统噪声处理方法研究", 《应用光学》 * |
| 郝鑫等: "太赫兹通信中高速数字信号处理并行化算法", 《太赫兹科学与电子信息学报》 * |
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