CN102868080A - Device capable of generating high terahertz pulse through external cavity resonance enhancement - Google Patents
Device capable of generating high terahertz pulse through external cavity resonance enhancement Download PDFInfo
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- CN102868080A CN102868080A CN2012104036770A CN201210403677A CN102868080A CN 102868080 A CN102868080 A CN 102868080A CN 2012104036770 A CN2012104036770 A CN 2012104036770A CN 201210403677 A CN201210403677 A CN 201210403677A CN 102868080 A CN102868080 A CN 102868080A
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Abstract
The invention relates to a device capable of generating a high terahertz pulse through external cavity resonance enhancement. A movable oblique cleavage pair is placed at the position of an outlet of a femtosecond laser, a pumping laser enters into an external cavity type resonance cavity which is formed by an input coupler, a plane mirror and a concave mirror group through the input coupler, the pumping laser generates frequency doubling light when passing through a frequency doubling crystal, the frequency doubling light and residual fundamental frequency light form an air plasma body at the position of concave mirror group common focus, and a generated terahertz pulse is reflected by a dichroic mirror to enter into a terahertz detection system. According to the device capable of generating the high terahertz pulse through the external cavity resonance enhancement, under the condition that damage thresholds of a cavity mirror and a frequency doubling crystal does not reach, terahertz waves with high intensity can be obtained, by means of change of insertion amount of the movable oblique cleavage pair, the pulse width of the pumping laser pulse can be adjusted, thereby the central wavelength and frequency spectrum width of the generated terahertz pulse are continuously adjusted, the operation is simple and convenient, the external cavity resonance enhancement is merely relevant to repetition frequency of the pumping laser, so that the external cavity is not required to be adjusted repeatedly, the application range is wide, and the practicability is high.
Description
Technical field
The present invention relates to a kind of Terahertz Technology, particularly a kind of device that produces the strong terahertz pulse that strengthens by external cavity resonance.
Background technology
THz wave is a kind of electromagnetic wave that a lot of particular advantages are arranged, its frequency is in 0.1 to 10 THz scope (wavelength is in 0.03 to 3 mm scope), it coincides in long-wave band and millimeter wave (submillimeter wave), and coincide at short-wave band and infrared ray, in electromagnetic spectrum, occupy very special position.Terahertz Technology is one and relates to the advanced technology that THz wave produces, propagates, controls and survey, and belongs to very important intersection Disciplinary Frontiers, a very tempting opportunity is provided for technological innovation, the national economic development and national security.2004, U.S. government was chosen as Terahertz science and technology one of " the ten large technology that change future world ".Although various countries have dropped into a large amount of manpower and materials in the Terahertz field, up to the present, the intensity of Terahertz wave source is still very low, has limited the development of THz wave science and technology, makes it use potential and fails all to bring into play.
As the production method of terahertz emission, utilize the nonlinear effect generation strong terahertz pulse of parameter in ionized gases to be widely used at present.Its cardinal principle is to utilize pumping laser wire drawing in air, produces plasma exciatiaon four wave mixing phenomenon, if add a frequency-doubling crystal in the place ahead of laser convergent point, will so that frequency be
Ultrashort pulse fundamental frequency light and frequency doubled light 2 thereof
In air, focus on simultaneously, make air ionization, produce strong terahertz emission.And when total pumping laser pulse energy surpasses the formation threshold value of air plasma, the amplitude of terahertz emission field and fundamental frequency light
Pulse energy be directly proportional, with frequency doubled light 2
The evolution of pulse energy be directly proportional.The advantage of utilizing this mechanism to produce the terahertz emission maximum is that experimental facilities is simple, compact conformation, and can work at normal temperatures.Compare with produce terahertz emission in crystal, there is not the damage threshold problem in theory in the method, namely without the requirement of the pumping laser intensity upper limit.If make air ionization so adopt high power ultra-short pulse laser to focus on, just can obtain the radiation source of the very high THz wave of power.
But, because the output pulse strength of present pump laser is subject to the restriction of power or pulsewidth, so that the intensity of the terahertz pulse that can produce and the tunable range on the frequency spectrum are all very limited, be unfavorable for the extensive use in its later stage.
Summary of the invention
The present invention be directed to all very limited problems of the intensity of the terahertz pulse that can produce now and the tunable range on the frequency spectrum, proposed a kind of method that produces the strong terahertz pulse by the external cavity resonance intensifier.This device not only can significantly improve by external cavity type resonance the peak power of pumping laser, thereby obtain high-intensity terahertz pulse, can also tiltedly split right insertion amount outside the chamber by freely changing, change the pulse duration of inceptive impulse, thereby realize the centre frequency of terahertz pulse and the continuous adjusting of spectrum width.
Technical scheme of the present invention is: a kind of device that produces the strong terahertz pulse that strengthens by external cavity resonance, by femto-second laser, it is right movably tiltedly to split, input coupler, level crossing, the first concave mirror, frequency-doubling crystal, dichroic mirror, the second concave mirror and terahertz detection system form, the first concave mirror wherein, the second concave mirror is a pair of confocal concave mirror, the first concave mirror, the second concave mirror is to putting, focus drops on the same point, input coupler and level crossing are to putting, frequency-doubling crystal is at the first concave mirror together between the focus, dichroic mirror is between confocal point and the second concave mirror, input coupler, level crossing, the first concave mirror and the second concave mirror form external cavity type resonance resonant cavity, it is right movably tiltedly to split in the placement of the exit of femto-second laser, enter external cavity type resonance resonant cavity from the pumping laser of tiltedly splitting output by input coupler, pumping laser produces frequency doubled light through behind the frequency-doubling crystal, frequency doubled light and remaining fundamental frequency light form air plasma at the first concave mirror and the confocal point of the second concave mirror place, produce terahertz pulse, the terahertz pulse of generation is entered the terahertz detection system by the dichroic mirror reflection.
Described input coupler, level crossing, the first concave mirror, the second concave mirror all are coated with the high-reflecting film that is complementary with pumping laser.Described pumping laser is through behind the frequency-doubling crystal, and remaining pumping laser is continued resonance enhancing in exocoel by the dichroic mirror transmission, and remaining frequency doubled light is voluntarily loss in exocoel.
Described tiltedly splitting optional fused quartz or K9 glass, tiltedly splitting right insertion amount or inclination angle can calculate according to centre frequency and the spectrum width of required terahertz pulse.
Beneficial effect of the present invention is: the present invention is a kind of device by the pulse of external cavity resonance enhancing generation strong terahertz, in the situation of the damage threshold that does not reach chamber mirror and frequency-doubling crystal, can obtain high-intensity THz wave; By changing the removable right insertion amount of tiltedly splitting, the pulse duration that can regulate the pumping laser pulse, thereby centre wavelength and the spectrum width of regulating continuously the terahertz pulse that produces, easy and simple to handle, application is strong; Because external cavity type resonance strengthens only relevant with the repetition rate of pumping laser, other parameter that changes pumping laser can not exert an influence to the resonance enhancing, does not need repeatedly exocoel to be adjusted, and has wide range of applications, and is practical.
Description of drawings
Fig. 1 is that the present invention strengthens the apparatus structure schematic diagram that produces the strong terahertz pulse by external cavity resonance.
Embodiment
Strengthen the apparatus structure schematic diagram that produces the strong terahertz pulse by external cavity resonance as shown in Figure 1, by femto-second laser 1, movably tiltedly split 2, input coupler 3, level crossing 4, the first concave mirror 5, frequency-doubling crystal 6, dichroic mirror 7, the second concave mirror 8 and terahertz detection system 9 form, the first concave mirror 5 wherein, the second concave mirror 8 is a pair of confocal concave mirrors, the first concave mirror 5,8 pairs in the second concave mirror is put, focus drops on the same point, 4 pairs of input coupler 3 and level crossings are put, frequency-doubling crystal 6 is at the first concave mirror 5 together between the focus, dichroic mirror 7 is between confocal point and the second concave mirror 8, input coupler 3, level crossing 4, the first concave mirror 5, the second concave mirror 8 forms external cavity type resonance resonant cavity, movably tiltedly split 2 in the placement of the exit of femto-second laser 1, enter external cavity type resonance resonant cavity from the pumping laser of tiltedly splitting 2 outputs by input coupler 3, pumping laser produces frequency doubled light through frequency-doubling crystal 6, frequency doubled light and remaining fundamental frequency light form air plasma at the first concave mirror 5 and the second concave mirror 8 confocal some places, produce terahertz pulse.The terahertz pulse that produces is entered terahertz detection system 9 by dichroic mirror 7 reflections, and remaining pumping laser is continued to resonate enhancing by dichroic mirror 7 transmissions in exocoel.Because input coupler 3, level crossing 4 and concave mirror group all are to be coated with the high-reflecting film that is complementary with pumping laser, remaining frequency doubled light can not form resonance in exocoel, but voluntarily loss in exocoel, the resonance that does not affect pumping laser strengthens.
Tiltedly split right insertion amount outside the chamber by freely changing, can change according to following formula the pulse duration of inceptive impulse, thereby realize the centre frequency of terahertz pulse and the continuous adjusting of spectrum width.The formula of pulse stretching:
, wherein
Be the variable quantity of pulse stretching, L tiltedly splits the insertion amount,
The GVD (Group Velocity Dispersion) parameter of tiltedly splitting chromatic dispersion material,
The spectral width of pump light pulse,
Tiltedly to split right angle of inclination.
In the following embodiments, the laser take the output center wavelength of light as 800 nm is as example, and its all band is consistent with the implementation method of this wave band.
Laser output center wavelength of light is 800 nm, pulse duration is that 35 fs(spectral ranges are 760-840 nm), repetition rate 1 KHz, obtain the frequency doubled light of 400 nm with BBO frequency-doubling crystal 6, it is example that input coupler 3 has 0.1% transmissivity, it is as follows that the specific implementation external cavity resonance strengthens the adjustment process that produces the strong terahertz pulse: by femto-second laser 1 output optical pulse, by movably tiltedly splitting 2, mobile one of them tiltedly split right, change its insertion amount, (be 10 ° take the inclination angle, thereby material is tiltedly splitting (fused quartz is about 35 at the GVD (Group Velocity Dispersion) parameter at 800 nm wavelength places for example of fused quartz to the pulse duration of change inceptive impulse
), when tiltedly splitting insertion amount from 1 to 10 mm variation, the excursion of the pulse duration of inceptive impulse is 1.4 to 14.0 fs).Then pumping laser enters external cavity type resonance resonant cavity by input coupler 3.Pumping laser produces the frequency doubled light of 400 nm by BBO frequency-doubling crystal 6, and frequency doubled light and remaining 800 nm pumping lasers form air plasma at concave mirror 5,8 confocal some place, produce THz wave.The THz wave of 800 nm pumping lasers, 400 nm frequency doubled lights and generation is through dichroic mirror 7, and THz wave is reflected and enters terahertz detection system 9,800 nm pumping lasers and then be transmitted, and continues to resonate in exocoel enhancing.Because input coupler 3 and level crossing 4 and concave mirror group all are to be coated with the high-reflecting film that is complementary with 800 nm pumping lasers, the frequency doubled light of remaining 400 nm can not form resonance in exocoel, meeting voluntarily loss in exocoel, and the resonance that does not affect pumping laser strengthens.Here tiltedly split 2 except fused quartz, also optional K9 glass and other transparent chromatic dispersion materials.
In whole experimentation, exocoel requires input coupler, level crossing and concave mirror group accurately to place, and guarantees the pumping laser enhancing of can resonating in exocoel.In addition, the regulation and control parameter in the experiment is: movably tiltedly split 2 insertion amount.Be 10 ° take the inclination angle, material is tiltedly splitting (fused quartz is about 35 at 800 nm wavelength place GVD (Group Velocity Dispersion) parameters for example of fused quartz
), when tiltedly splitting insertion amount from 1 to 10 mm variation, the excursion of the pulse duration of inceptive impulse is 1.4 to 14.0 fs).The centre frequency of terahertz pulse and the change of spectrum width can draw by the change accurate Calculation of tiltedly splitting the insertion amount.
We place in the exit of femto-second laser 1 and movably tiltedly split 2, tiltedly split can freely change the insertion amount to 2, and the pulse duration of inceptive impulse is changed, thereby regulate continuously centre frequency and the spectrum width of the terahertz pulse that the later stage produces.The tunable pumping laser of pulse duration enters by external cavity type resonance resonant cavity by input coupler 3, obtains resonance and strengthens, and its peak strength is increased substantially.Again by frequency-doubling crystal 6, frequency doubled light and remaining fundamental frequency light focus at concave mirror group 5,8 confocal some places, make air ionization, produce the strong terahertz pulse, the terahertz pulse that produces is reflected onto the terahertz detection system when passing through dichroic mirror 7, and remaining pumping laser transmission is by dichroic mirror 7, in the continuous enhancing of resonating of exocoel relaying.Because input coupler 3, level crossing 4 and concave mirror group all are to be coated with the high-reflecting film that is complementary with incident laser, remaining frequency doubled light can voluntarily loss in exocoel, and the resonance that does not affect pump light strengthens.
Claims (4)
1. device that strengthen to produce the strong terahertz pulse by external cavity resonance, it is characterized in that, by femto-second laser (1), movably tiltedly split (2), input coupler (3), level crossing (4), the first concave mirror (5), frequency-doubling crystal (6), dichroic mirror (7), the second concave mirror (8) and terahertz detection system (9) form, the first concave mirror (5) wherein, the second concave mirror (8) is a pair of confocal concave mirror, the first concave mirror (5), the second concave mirror (8) is to putting, focus drops on the same point, input coupler (3) and level crossing (4) are to putting, frequency-doubling crystal (6) is positioned at the first concave mirror (5) together between the focus, dichroic mirror (7) is positioned between confocal point and the second concave mirror (8), input coupler (3), level crossing (4), the first concave mirror (5) and the second concave mirror (8) form external cavity type resonance resonant cavity, movably tiltedly split (2) in the placement of the exit of femto-second laser (1), enter external cavity type resonance resonant cavity from the pumping laser of tiltedly splitting (2) output by input coupler (3), pumping laser is through frequency-doubling crystal (6), frequency doubled light and remaining fundamental frequency light form air plasma at the first concave mirror (5) and the confocal point of the second concave mirror (8) place, produce terahertz pulse, the terahertz pulse of generation is entered terahertz detection system (9) by dichroic mirror (7) reflection.
2. the described device that strengthen to produce the strong terahertz pulse by external cavity resonance according to claim 1, it is characterized in that described input coupler (3), level crossing (4), the first concave mirror (5), the second concave mirror (8) all are coated with the high-reflecting film that is complementary with pumping laser.
3. the described device that strengthen to produce the strong terahertz pulse by external cavity resonance according to claim 2, it is characterized in that, behind the described pumping laser process frequency-doubling crystal (6), remaining pumping laser is by dichroic mirror (7) transmission, the continuation enhancing of resonating in exocoel, remaining frequency doubled light is voluntarily loss in exocoel.
4. the described device that strengthen to produce the strong terahertz pulse by external cavity resonance according to claim 1, it is characterized in that, described tiltedly splitting (2) optional fused quartz or K9 glass, insertion amount or the inclination angle of tiltedly splitting (2) can calculate according to centre frequency and the spectrum width of required terahertz pulse.
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Cited By (7)
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| CN103840366A (en) * | 2014-03-07 | 2014-06-04 | 上海理工大学 | Method for achieving terahertz wave center frequency continuous adjustability through pulse laser widening |
| CN105866061A (en) * | 2016-03-31 | 2016-08-17 | 上海理工大学 | A differential pulse detecting apparatus for terahertz wave time domain information and a differential pulse detecting method |
| CN105891144A (en) * | 2016-03-31 | 2016-08-24 | 上海理工大学 | Terahertz scanning system and method |
| WO2017181310A1 (en) * | 2016-04-18 | 2017-10-26 | 上海理工大学 | Apparatus and method for strengthening terahertz signal on the basis of hollow-core metal waveguide optical fiber |
| CN109239009A (en) * | 2018-09-03 | 2019-01-18 | 杭州电子科技大学 | Gaseous mercury concentration detection apparatus and method based on ring resonator frequency multiplication structure |
| CN111781650A (en) * | 2020-05-29 | 2020-10-16 | 欧必翼太赫兹科技(北京)有限公司 | Terahertz security inspection imaging device |
| CN115000785A (en) * | 2022-05-16 | 2022-09-02 | 中国人民解放军军事科学院国防科技创新研究院 | Terahertz radiation regulation and control device and method based on laser pulse width modulation |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103840366A (en) * | 2014-03-07 | 2014-06-04 | 上海理工大学 | Method for achieving terahertz wave center frequency continuous adjustability through pulse laser widening |
| CN105866061A (en) * | 2016-03-31 | 2016-08-17 | 上海理工大学 | A differential pulse detecting apparatus for terahertz wave time domain information and a differential pulse detecting method |
| CN105891144A (en) * | 2016-03-31 | 2016-08-24 | 上海理工大学 | Terahertz scanning system and method |
| CN105866061B (en) * | 2016-03-31 | 2018-08-31 | 上海理工大学 | The anticoincidence pulse detection device and anticoincidence pulse detection method of THz wave time-domain information |
| CN105891144B (en) * | 2016-03-31 | 2018-10-23 | 上海理工大学 | Terahertz scanning system and scan method |
| WO2017181310A1 (en) * | 2016-04-18 | 2017-10-26 | 上海理工大学 | Apparatus and method for strengthening terahertz signal on the basis of hollow-core metal waveguide optical fiber |
| US10663397B2 (en) | 2016-04-18 | 2020-05-26 | University Of Shanghai For Science And Technology | Method and device of enhancing terahertz wave signals based on hollow metal waveguide optical fiber |
| CN109239009A (en) * | 2018-09-03 | 2019-01-18 | 杭州电子科技大学 | Gaseous mercury concentration detection apparatus and method based on ring resonator frequency multiplication structure |
| CN111781650A (en) * | 2020-05-29 | 2020-10-16 | 欧必翼太赫兹科技(北京)有限公司 | Terahertz security inspection imaging device |
| CN115000785A (en) * | 2022-05-16 | 2022-09-02 | 中国人民解放军军事科学院国防科技创新研究院 | Terahertz radiation regulation and control device and method based on laser pulse width modulation |
| CN115000785B (en) * | 2022-05-16 | 2023-12-01 | 中国人民解放军军事科学院国防科技创新研究院 | Terahertz radiation regulation and control device and method based on laser pulse width modulation |
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