CN110444997A - A kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling - Google Patents
A kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling Download PDFInfo
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- CN110444997A CN110444997A CN201910751972.7A CN201910751972A CN110444997A CN 110444997 A CN110444997 A CN 110444997A CN 201910751972 A CN201910751972 A CN 201910751972A CN 110444997 A CN110444997 A CN 110444997A
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- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
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- H01S1/02—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range solid
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Abstract
The invention belongs to tera-hertz spectras and technical field of imaging, are related to a kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling, main structure includes: fiber coupling module, optical frequency-doubling module and photoconductive antenna；The main structure of fiber coupling module includes optical fiber collimator and condenser lens；Wherein optical fiber collimator is located at the left side of condenser lens, the two as close to, distance range is traditionally arranged to be 0~10mm, detection light sequentially passes through optical fiber collimator and condenser lens on the left of optical fiber collimator and is transferred to optical frequency-doubling module, wherein optical frequency-doubling module is set to the right side of condenser lens, photoconductive antenna is additionally provided on the right side of optical frequency-doubling module, it detects light and is finally transmitted to photoconductive antenna via optical frequency-doubling module, its main structure is simple, design concept is ingenious, preparation cost is low, it is suitable for industrialized production, application environment is friendly simultaneously, market prospects are extremely wide.
Description
Technical field:
The invention belongs to tera-hertz spectras and technical field of imaging, are related to a kind of terahertz light conductance antenna detector, special
It is not a kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling, preparation cost is low and is used for terahertz light
Spectrum and the stability of imaging are high.
Background technique:
THz wave refers to frequency in 0.1~10THz (1THz=1012Hz electromagnetic wave) is located at microwave and infrared band
Between.Have many advantages, such as that penetration capacity is strong, photon energy is low, fingerprint frequency spectrum so that it is in material identification, safety inspection, material
There is extremely important application prospect in the fields such as biopsy, the wireless communication of nondestructive inspection, biological tissue with structure.For
For the terahertz time-domain pulse of broadband, photoconduction sampling is one of most effective detection means.In photoconduction sampling, need to make
With the semiconductor material of special processing, the photoconductivity switching based on this material can be excited by femtosecond pulse and generate photoproduction
Carrier, these carriers form electric current under the action of terahertz pulse electric field, can be realized by the variation of probe current
Measurement to terahertz pulse.To realize good photoconductivity switching detection efficient, the photon energy of femtosecond laser must be high
In the energy bandgaps of semiconductor material, photo-generated carrier can be just inspired, therefore select the optical maser wavelength being mutually matched and partly lead
Body material becomes the key of terahertz light photoconductive detector
Currently, there are mainly two types of the terahertz light conductance antenna detectors of comparative maturity: one is using 1560nm (±
40nm) the fiber coupling terahertz light conductance antenna detector of wavelength femtosecond laser excitation, the femto-second laser of 1560nm wave band
Performance is stablized, compact-sized, and this wave band can be transmitted using all -fiber, and optical path reliability and stability is all very high, but
It is the disadvantage is that the corresponding semiconductor material of 1560nm wavelength is usually InGaAs, this Material growth is relatively difficult, prepares work
Skill is complicated；Another kind is the terahertz light conductance antenna detector excited using 780nm (± 20nm) wavelength femtosecond laser,
The corresponding semiconductor material of 780nm wavelength is usually the LT-GaAs of GaAs or low-temperature epitaxy, comparatively both materials are made
Standby fairly simple, cost is also relatively low, but haves the defects that the optical fiber technology of the wave band is not mature enough, can not use light
Fibre conduction, generally is free space system, therefore the Stability and dependability of optical path is poor, affected by environment larger, for
The requirement of usage scenario is stringenter.Therefore, the present invention, which seeks to design, provides a kind of fiber coupling terahertz based on optical frequency-doubling
Hereby photoconductive antenna detector.
Summary of the invention:
It is an object of the invention to overcome defect described above, seek to design a kind of fiber coupling based on optical frequency-doubling
Terahertz light conductance antenna detector, the antenna detector environmental suitability is strong, good for tera-hertz spectra and the effect of imaging.
To achieve the goals above, a kind of fiber coupling terahertz light conductance day based on optical frequency-doubling of the present invention
Line detector is achieved through the following technical solutions:
A kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling of the present invention, main body knot
Structure includes: fiber coupling module, optical frequency-doubling module and photoconductive antenna；
The main structure of fiber coupling module includes optical fiber collimator 1 and condenser lens 2；Final photoconductive antenna is visited
Device is surveyed using whole package casing, is easy to implement Products integration.
The present invention realizes that the specific work process of terahertz time-domain pulse detection is as follows:
S1, the femto-second laser pulse as the 1560nm (± 40nm) wavelength for detecting light by optical fiber transmission are introduced into light
Fine coupling module is emitted directional light after optical fiber collimator collimates, and then by condenser lens, laser is focused on optics times
Frequency module；
S2, by the polarization cycle of frequency-doubling crystal, operating temperature in control times frequency module, enable again frequency module with height
Shg efficiency by the input optical sccond-harmonic generation of 1560nm be 780nm output light；
The pulse laser of 780nm wavelength after S3, frequency multiplication is incident on GaAs (or LT-GaAs) photoconductive antenna, is generated
Photo-generated carrier, photo-generated carrier generate transient state induced current under incident Terahertz electric field driven, this is faradic strong
Spend directly proportional to Terahertz electric field strength, while the external current output circuit of photoconductive antenna is by the transient current output of generation
Into signal collecting device, it is then able to obtain complete terahertz pulse time domain waveform by the method for sampled measurements.
Further, femto-second laser pulse will introduce certain negative chirp before injecting this device in the present invention, to neutralize
Pulse broadening effect of the light pulse in optical fiber transmission process.
Further, times frequency module may be selected but be not limited to periodically poled lithium niobate crystal PPLN, mix oxidation in the present invention
Magnesium periodically poled lithium niobate crystalline MgO: PPLN or PPMgO:LN, period polarized potassium titanyl phosphate PPKTP；Meanwhile selection is suitable
Crystal length to adapt in the present invention used femtosecond pulse, reduce crystal for the negative effect of femtosecond laser
It answers.
Further, 4 integrated temperature control unit of times frequency module, to ensure its transformation efficiency stable in central wavelength.
Further, consider that times frequency module acts on the broadening of high-peak power femtosecond pulse, strobe pulse broadening is small, has
There are two times of frequency modules of high damage threshold, it is final to guarantee the relatively narrow pulse width of terahertz emission and wider spectral range.
It further, should be in the input and output of crystal in order to reduce the Fresnel loss that frequency-doubling crystal high refractive index causes
End face increases anti-reflection film.
Further, the present invention can by adjusting each component relative position inside condenser lens focal length, configuration transmitter,
The spot size being irradiated on times frequency module is controlled, to reach optimal conversion efficiency.
Further, semiconductor material used in photoconductive antenna 5 is GaAs, LT-GaAs etc. of (but being not limited to) maturation, is swashed
Hair femtosecond pulse center wavelength of light is 780nm (± 20nm).
Compared with prior art, the present invention what is obtained has the beneficial effect that:
1, it is put forward for the first time before detection light enters semiconductor switch, introduces optical frequency-doubling module, it can be by 1560nm
The detection femtosecond pulse frequency multiplication of (± 40nm) wavelength is the femtosecond pulse of 780nm (± 20nm) wavelength, so as to
Cost is relatively low, the GaAs of technical maturity (or LT-GaAs) carrys out the high InGaAs of alternative cost for selection, as semiconductor switch material
Material, is feasible low-cost optical fiber terahertz light conductance antenna detector Integrated Solution.
2, all -fiber biography may be implemented in the femtosecond pulse for detecting gloss 1560nm (± 40nm) wavelength in instrument
It is defeated, overcome the disadvantages of free space stability is poor, environmental suitability is poor.
3, innovative point of the invention also resides in: temperature control and optimized Selection (length and polarization week based on frequency-doubling crystal
Phase selection), it is ensured that the frequency multiplication transformation efficiency of stability and high efficiency, and ensure minimum pulse broadening effect.
4, all -fiber biography may be implemented in the femtosecond pulse for detecting gloss 1560nm (± 40nm) wavelength in instrument
It is defeated, overcome the disadvantages of free space stability is poor, environmental suitability is poor；
5, before detection light enters semiconductor switch, optical frequency-doubling module is introduced, it can be by 1560nm (± 40nm)
The detection femtosecond pulse frequency multiplication of wavelength is the femtosecond pulse of 780nm (± 20nm) wavelength, can be avoided selection price
Semiconductor material of the expensive InGaAs photoconductivity switching, and select preparation process is simple, the lower GaAs of price (or
LT-GaAs), the production domesticization for reducing Terahertz instrument cost, realizing 1560nm wave band terahertz light conductance antenna detector
It is of great significance.
To sum up, main structure of the present invention is simple, and design concept is ingenious, and preparation cost is low, is suitable for industrialized production, answers simultaneously
With environmental-friendly, market prospects are extremely wide.
Detailed description of the invention:
Fig. 1 is main structure schematic illustration of the invention.
In figure: optical fiber collimator 1, condenser lens 2, fiber coupling module 3 (including 1 optical fiber collimator and 2 condenser lenses),
Optical frequency-doubling module 4, photoconductive antenna 5, package casing 6.
Specific embodiment:
In order to clearly illustrate the technical characterstic of this programme, the present invention is made further below with reference to embodiment
It is bright.
Embodiment 1
A kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling that the present embodiment is related to, main body
Structure includes:
The main structure of fiber coupling module 3 includes optical fiber collimator 1 and condenser lens 2；Final photoconductive antenna
Detector is easy to implement Products integration using whole package casing 6；
Wherein optical fiber collimator 1 is located at the left side of condenser lens 2, and the two is as close to distance range is traditionally arranged to be 0
~10mm, detection light sequentially pass through optical fiber collimator 1 and condenser lens 2 from the left side of optical fiber collimator 1 and are transferred to optics times
Frequency module 4, wherein optical frequency-doubling module 4 is set to the right side of condenser lens 2, is additionally provided on the right side of optical frequency-doubling module 4
Photoconductive antenna 5 detects light via optical frequency-doubling module 4 and is finally transmitted to photoconductive antenna 5.
The present embodiment realizes that the specific work process of terahertz time-domain pulse detection is as follows:
S1, the femto-second laser pulse as the 1560nm (± 40nm) wavelength for detecting light by optical fiber transmission are introduced into light
Fine coupling module 3 is emitted directional light after the collimation of optical fiber collimator 1, then by condenser lens 2, laser is focused on light
Learn times frequency module 4；
S2, by the polarization cycle of frequency-doubling crystal, operating temperature in control times frequency module, enable again frequency module with height
Shg efficiency by the input optical sccond-harmonic generation of 1560nm be 780nm output light；
The pulse laser of 780nm wavelength after S3, frequency multiplication is incident on GaAs (or LT-GaAs) photoconductive antenna 5, is generated
Photo-generated carrier, photo-generated carrier generate transient state induced current under incident Terahertz electric field driven, this is faradic strong
Spend it is directly proportional to Terahertz electric field strength, while photoconductive antenna 5 it is external current output circuit the transient current of generation is defeated
Out into signal collecting device, it is then able to obtain complete terahertz pulse time domain waveform by the method for sampled measurements.
Further, femto-second laser pulse will introduce certain negative chirp before injecting this device in the present embodiment, in
With pulse broadening effect of the light pulse in transmission process, meanwhile, injection femtosecond pulse light should be that e is polarized.
Further, times frequency module may be selected but be not limited to periodically poled lithium niobate crystal PPLN, mix oxygen in the present embodiment
Change magnesium periodically poled lithium niobate crystalline MgO: PPLN or PPMgO:LN, period polarized potassium titanyl phosphate PPKTP；Meanwhile it selecting to close
The length of suitable crystal reduces crystal for the negative of femtosecond laser to adapt to femtosecond pulse used in the present embodiment
Effect.
Further, 4 integrated temperature control unit of times frequency module, to ensure its transformation efficiency stable in central wavelength.
Further, consider that times frequency module acts on the broadening of high-peak power femtosecond pulse, strobe pulse broadening is small, has
There are two times of frequency modules of high damage threshold, it is final to guarantee the relatively narrow pulse width of terahertz emission and wider spectral range.
It further, should be in the input and output of crystal in order to reduce the Fresnel loss that frequency-doubling crystal high refractive index causes
End face increases anti-reflection film.
Further, the present embodiment can be by adjusting each component inside 2 focal length of condenser lens, configuration transmitter with respect to position
It sets, the spot size being irradiated on times frequency module is controlled, to reach optimal conversion efficiency.
Further, semiconductor material used in photoconductive antenna 55 is GaAs, LT-GaAs etc. of (but being not limited to) maturation,
Excitation femtosecond pulse center wavelength of light is 780nm (± 20nm).
Claims (8)
1. a kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling, it is characterised in that pass through following technology
Scheme is realized: the main structure of fiber coupling module includes optical fiber collimator and condenser lens；Final photoconductive antenna is visited
Device is surveyed using whole package casing, is easy to implement Products integration；Wherein optical fiber collimator is located at the left side of condenser lens, and two
Person's distance range is 0~10mm, and detection light sequentially passes through optical fiber collimator and condenser lens and passed on the left of optical fiber collimator
Be handed to optical frequency-doubling module, wherein optical frequency-doubling module is set to the right side of condenser lens, the right side of optical frequency-doubling module also
It is provided with photoconductive antenna, light is detected via optical frequency-doubling module and is finally transmitted to photoconductive antenna.
Its specific work process is as follows:
S1, the femto-second laser pulse as the 1520nm-1600nm wavelength for detecting light by optical fiber transmission are introduced into optical fiber coupling
Block is molded, directional light is emitted after optical fiber collimator collimates, then by condenser lens, laser is focused on into optical frequency-doubling mould
Block；
S2, by the polarization cycle of frequency-doubling crystal, operating temperature in control times frequency module, enable again frequency module with high times
The output light that the input optical sccond-harmonic generation of 1560nm is 780nm by frequency efficiency；
The pulse laser of 780nm wavelength after S3, frequency multiplication is incident on GaAs photoconductive antenna, generates photo-generated carrier, photoproduction
Carrier generates transient state induced current, the faradic intensity and Terahertz electric-field strength under incident Terahertz electric field driven
Spend directly proportional, while the external current output circuit of photoconductive antenna exports the transient current of generation to signal collecting device
In, it is then able to obtain complete terahertz pulse time domain waveform by the method for sampled measurements.
2. a kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling according to claim 1,
It is characterized in that times frequency module can select but be not limited to periodically poled lithium niobate crystal PPLN, mix magnesia periodically poled lithium niobate
Crystalline MgO: PPLN or PPMgO:LN, period polarized potassium titanyl phosphate PPKTP；Meanwhile selecting the length of suitable crystal with suitable
Femtosecond pulse used in the present invention is answered, reduces crystal for the negative effect of femtosecond laser.
3. a kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling according to claim 1,
It is characterized in that considering that times frequency module acts on the broadening of high-peak power femtosecond pulse, strobe pulse broadening is small, has high damage
Two times of frequency modules of threshold value, it is final to guarantee the relatively narrow pulse width of terahertz emission and wider spectral range.
4. a kind of fiber coupling Terahertz based on optical frequency-doubling according to any claim according to claim 1-3
Photoconductive antenna detector, it is characterised in that a times frequency module is integrated with temperature conditioning unit, to ensure that it stablizes in central wavelength
Transformation efficiency.
5. a kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling according to claim 4,
It is characterized in that increasing in the input and output end face of crystal to reduce the Fresnel loss of frequency-doubling crystal high refractive index initiation
Anti-reflection film.
6. a kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling according to claim 1,
It is characterized in that semiconductor material used in photoconductive antenna includes mature GaAs, LT-GaAs, excites femtosecond pulse center wavelength of light
For 780nm ± 20nm.
7. a kind of according to claim 1, fiber coupling terahertz based on optical frequency-doubling described in any claim in 2,3,5,6
Hereby photoconductive antenna detector, it is characterised in that the present invention can be by adjusting each inside condenser lens focal length, configuration transmitter
Component relative position controls the spot size being irradiated on times frequency module, to reach optimal conversion efficiency.
8. a kind of fiber coupling terahertz light conductance antenna detector based on optical frequency-doubling according to claim 7,
It is characterized in that femto-second laser pulse will introduce negative chirp before injecting this device, to neutralize pulse of the light pulse in transmission process
Broadening effect, meanwhile, injection femtosecond pulse light should be that e is polarized.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8427740B1 (en) * | 2010-03-10 | 2013-04-23 | Terahertz Technologies Llc | Modulation of terahertz radiation at room temperatures |
| CN103368042A (en) * | 2013-07-05 | 2013-10-23 | 中国科学院半导体研究所 | Terahertz source equipment based on semiconductor ultra-short pulsed laser |
| CN104283097A (en) * | 2014-10-30 | 2015-01-14 | 上海朗研光电科技有限公司 | 780 nm high-power optical-fiber femtosecond laser device |
| CN208241070U (en) * | 2017-12-27 | 2018-12-14 | 清华大学 | THz wave oscillator |
-
2019
- 2019-08-15 CN CN201910751972.7A patent/CN110444997A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8427740B1 (en) * | 2010-03-10 | 2013-04-23 | Terahertz Technologies Llc | Modulation of terahertz radiation at room temperatures |
| CN103368042A (en) * | 2013-07-05 | 2013-10-23 | 中国科学院半导体研究所 | Terahertz source equipment based on semiconductor ultra-short pulsed laser |
| CN104283097A (en) * | 2014-10-30 | 2015-01-14 | 上海朗研光电科技有限公司 | 780 nm high-power optical-fiber femtosecond laser device |
| CN208241070U (en) * | 2017-12-27 | 2018-12-14 | 清华大学 | THz wave oscillator |
Non-Patent Citations (2)
| Title |
|---|
| 曾志男等著: "《阿秒激光技术》", 31 July 2016, 国防工业出版社 * |
| 达里宇舒·萨义德齐亚: "《太赫兹成像 传感及通信技术手册》", 31 May 2016, 国防工业出版社 * |
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Application publication date: 20191112 |