WO2017181310A1 - 基于空心金属波导光纤增强太赫兹波信号的装置及方法 - Google Patents

基于空心金属波导光纤增强太赫兹波信号的装置及方法 Download PDF

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WO2017181310A1
WO2017181310A1 PCT/CN2016/000613 CN2016000613W WO2017181310A1 WO 2017181310 A1 WO2017181310 A1 WO 2017181310A1 CN 2016000613 W CN2016000613 W CN 2016000613W WO 2017181310 A1 WO2017181310 A1 WO 2017181310A1
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light
terahertz
metal waveguide
hollow metal
waveguide fiber
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PCT/CN2016/000613
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French (fr)
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彭滟
徐博伟
朱亦鸣
张腾飞
陈万青
戚彬彬
庄松林
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上海理工大学
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Publication of WO2017181310A1 publication Critical patent/WO2017181310A1/zh
Priority to US16/258,345 priority Critical patent/US10663397B2/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G01J5/08—Optical arrangements
    • G01J5/0818—Waveguides
    • G01J5/0821—Optical fibres
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0208—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/021—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using plane or convex mirrors, parallel phase plates, or particular reflectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0216—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using light concentrators or collectors or condensers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0218—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using optical fibers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/42—Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G01J5/08—Optical arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G01J5/08—Optical arrangements
    • G01J5/0818—Waveguides
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/3501—Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/365—Non-linear optics in an optical waveguide structure
    • H—ELECTRICITY
    • 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
    • H01S1/00—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range
    • H01S1/02—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range solid
    • H—ELECTRICITY
    • 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
    • H01S1/00—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range
    • H01S1/06—Gaseous, i.e. beam masers
    • H—ELECTRICITY
    • 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
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0092—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity

Definitions

  • the present invention relates to an enhanced terahertz wave device, and more particularly to an apparatus and method for enhancing a terahertz wave signal based on a hollow metal waveguide fiber.
  • Terahertz radiation is an electromagnetic wave with a frequency in the range of 0.1 to 10 THz. This band is located between microwave and infrared. It has the characteristics of rich information, high spatial-temporal coherence, low photon energy, etc. in astronomy, biology, computer, communication and other sciences. The field has great application value.
  • the main application research is terahertz time domain spectroscopy, terahertz imaging technology, security inspection, terahertz radar, astronomy, communication technology.
  • the generation of terahertz waves by air drawing is a relatively common, simple and reliable method.
  • the principle is that when a laser pulse having a wavelength of 800 nm is concentrated and passed through a BBO frequency doubling crystal, it is partially converted into a laser having a wavelength of 400 nm. According to the nonlinear properties of the laser, the two beams interact strongly when the pulses coincide, and the ionized gas medium radiates terahertz waves.
  • the two wavelengths of light produce different refractive indices as they propagate through the medium, their propagation speeds are also different.
  • the pulse widths of the two beams are extremely small, so the time between the two can be coincident, and the interaction time to generate the terahertz wave is very short.
  • the two pulses gradually separate with their respective propagation, the two beams will also stop interacting and no longer produce a terahertz signal.
  • the main advantage of this method is that the obtained terahertz wave has a wide bandwidth, the whole device is convenient to set up, the occupied space is small, and the comprehensive cost is relatively low.
  • the coherence length is short (usually on the order of millimeters), so that laser energy in a long propagation distance cannot be effectively utilized.
  • the air contains more water, and water has a stronger absorption capacity for terahertz waves. Therefore, the temperature, humidity and other conditions of the environment will have a very significant impact on the generation, detection, and collection of terahertz waves.
  • the present invention is directed to two problems in which a large amount of terahertz waves are absorbed by air in the air, and a terahertz wave is generated by an air drawing method, and the nonlinear action time of the two different wavelengths of light is too short, and the conversion efficiency of the terahertz wave is not high.
  • the technical scheme of the present invention is: a device for enhancing a terahertz wave signal based on a hollow metal waveguide fiber, wherein an incident laser beam having a wavelength of 800 nm emitted by a laser source is split into two beams by a beam splitter, and the 800 nm transmitted light passes through a plane mirror group. After continuous reflection, it is concentrated by the first convex lens into the BBO crystal and partially converted into laser with a wavelength of 400 nm.
  • the light output from the BBO crystal includes light of 800 nm and 400 nm; the reflected light of 800 nm passes through the first plane mirror, and the adjustable delay system
  • the second planar mirror and the second convex lens after a certain time phase delay with the 800 nm light and the 400 nm light outputted by the BBO crystal, are collectively passed through the combining piece, and are concentrated into the hollow metal waveguide fiber filled with the dry gas, and the transmitted light is transmitted.
  • the focus of the reflected light after convergence by the convex lens is located at the entrance end of the hollow metal waveguide fiber, and the hollow metal waveguide fiber is outputted by the parabolic mirror after being outputted to the detection system.
  • the method for enhancing the terahertz wave signal of the device opens the laser source.
  • the 800 nm light output from the BBO crystal coincides with the 400 nm light pulse, and the first light beam is transmitted forward.
  • the ionized gas medium radiates the terahertz wave.
  • the adjustable delay system is adjusted to make the 800 nm reflected light relatively pulsed.
  • Delay as the second beam, when the 800 nm light pulse of the first beam is completely separated from the 400 nm light pulse, the pulse of the second beam 800 nm reflected light just coincides with the 400 nm light pulse, and continues to produce terahertz, too Hertz is output from the hollow metal waveguide fiber and then collected by a parabolic mirror into the detection system.
  • the invention has the beneficial effects that the device and the method for enhancing the terahertz wave signal based on the hollow metal waveguide fiber are simple in construction, and can directly and effectively increase the signal intensity of the terahertz wave by three times.
  • the invention has wide application range, strong practicability, simple operation, low cost, improved terahertz wave energy loss and improved terahertz wave intensity.
  • FIG. 1 is a schematic structural view of an apparatus for enhancing a terahertz wave signal based on a hollow metal waveguide fiber according to the present invention
  • FIG. 2 is a schematic view showing the principle of generating a terahertz wave by an air drawing method using a BBO frequency doubling crystal according to the present invention
  • FIG. 3 is a schematic diagram showing the principle of introducing a second bundle of 800 nm light-enhanced terahertz wave signal intensity by using a splitter sheet in the present invention; intention.
  • FIG. 1 is a schematic structural view of a device for enhancing a terahertz wave signal based on a hollow metal waveguide fiber, and is composed of a laser source 1, a beam splitter 2, a plane mirror 3, a plane mirror 4, a plane mirror 5, and a plane mirror 6.
  • the mirror 17 and the mechanical delay system are composed of a movable motor 18.
  • the incident laser light having a wavelength of 800 nm emitted from the laser source 1 passes through the splitting sheet 2 and is split into two beams.
  • the transmitted first beam of 800 nm light is continuously reflected by a plane mirror group composed of plane mirrors 3, 4, 5, and 6 and then concentrated by the convex lens 7 into the BBO crystal 7 and partially converted into a laser having a wavelength of 400 nm (this)
  • the convex lens 7 converges on the first 800 nm light, but does not focus the light on the BBO crystal because the BBO crystal is susceptible to damage by the high energy laser.
  • the light output from the BBO crystal 7 includes 800 nm and 400 nm.
  • the second beam of 800 nm reflected light passes through the plane mirrors 14, 17, 16, 15 (where the plane mirrors 16, 17 are fixed to the motor 18 to form a mechanical delay system) and the convex lens 13, and the 800 nm light output from the BBO crystal 7 After a certain time phase delay with the 400 nm light, the light is merged into the hollow metal waveguide fiber 10 filled with the dry gas through the combining sheet 9. The focus of the two beams concentrated by the lens is located at the entrance end of the hollow metal waveguide fiber 10.
  • the first bundle of 800 nm light coincides with the 400 nm light pulse, and they undergo a nonlinear interaction when transmitted forward, and the ionized gas medium radiates a terahertz wave.
  • the first beam of 800 nm light and the 400 nm light pulse gradually move away.
  • the first bundle of 800 nm light no longer interacts with the 400 nm light to produce a terahertz wave.
  • the movable motor 18 adjusts the distance between the two planar mirrors 16, 17 and the first planar mirror 15 and the second planar mirror 14 in the adjustable delay system by the mechanical delay system, thereby controlling the second beam of 800 nm light relative to
  • the pulse delay is such that when the first beam of 800 nm light pulse is completely separated from the 400 nm light pulse generated by the BBO crystal, the pulse of the second beam of 800 nm light just coincides with the 400 nm light pulse, thereby continuing to generate terahertz, and finally outputting The terahertz strength can be increased by three times.
  • the terahertz output is collected by the parabolic mirror 11 and enters the detection system 12.
  • the terahertz is collected by a 1:1 splitter beam, and the incident light having a wavelength of 800 nm is passed through a BBO frequency doubling crystal to form a terahertz in a hollow metal waveguide fiber filled with dry air.
  • the incident light of other wavelength bands, the different ratios of the splitting piece, and the implementation method of charging other kinds of dry gas in the optical fiber are basically the same as the present embodiment.
  • the specific implementation of the enhanced terahertz signal is as follows: the incident laser light having a wavelength of 800 nm emitted by the laser source 1 is split into two beams after passing through the 1:1 splitting sheet 2.
  • the transmitted first beam of 800 nm light is continuously reflected by the plane mirror group, and then concentrated by the convex lens 7 into the BBO crystal 7 and partially converted into a laser having a wavelength of 400 nm (the convex lens 7 converges on the first bundle of 800 nm light, but Instead of focusing the light onto the surface of the BBO crystal, the BBO crystal is susceptible to damage by the high energy laser;
  • the second beam of 800 nm passes through the plane mirrors 14, 17, 16, 15 (where the planar mirrors 16, 17 are attached to the motor 18)
  • the mechanical delay system) and the convex lens 13 are caused to have a certain time phase delay with the first bundle of 800 nm light and 400 nm light, and then collectively pass through the combining sheet 9 to be concentrated in the hollow metal waveguide fiber
  • the focus of the two beams concentrated by the lens is located at the entrance end of the hollow metal waveguide fiber.
  • the first bundle of 800 nm light coincides with the 400 nm light pulse. As shown in FIG. 2, they interact nonlinearly when forward, and the ionized gas medium radiates terahertz waves. As the propagation distance increases, the first beam of 800 nm light and the 400 nm light pulse gradually move away. When the two are completely separated, the first bundle of 800 nm light no longer interacts with the 400 nm light to produce a terahertz wave.
  • the movable motor 18 controls the second beam of 800 nm relative pulse delay by the mechanical delay system so that when the first beam of 800 nm light pulse is completely separated from the 400 nm light pulse generated by the BBO crystal, the second beam of 800 nm light is just right. It starts to coincide with the 400nm light pulse, and continues to produce terahertz.
  • the final output terahertz wave intensity can be increased by three times.
  • the terahertz output is collected by the parabolic mirror 11 and enters the detection system 12.
  • FIG. 3 a schematic diagram of using a splitter to introduce a second bundle of 800 nm light-enhanced terahertz wave signal intensity, a light pulse having a wavelength of 800 nm and a light pulse having a wavelength of 400 nm are coincident within a distance of three coherence lengths Lc. And continually strong interactions produce terahertz waves.
  • the schematic diagram of the terahertz wave generated by the air drawing method using the BBO frequency doubling crystal as shown in FIG. 2 in the process of generating the terahertz wave by the conventional conventional air drawing method, the 800 nm light and the 400 nm light are only in one coherence length Lc. coincide. Therefore, a simple comparison shows that the method of the present invention increases the terahertz wave signal strength by a factor of three.
  • the device of the present invention uses a simple device such as a splitting plate, a plane mirror, a combining beam, and a mechanical delay system to generate a second bundle of 800 nm wavelength light separated by the splitting beam and a first beam of 800 nm light for a certain time.
  • the phase delays are converged in the hollow metal waveguide fiber, and in turn, nonlinearly interact with the 400 nm wavelength light pulse, ionizing the gas in the fiber to generate terahertz waves;
  • device 2 uses the total reflection characteristics of the hollow metal waveguide fiber to gather and propagate Generated terahertz light waves.

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Abstract

一种基于空心金属波导光纤增强太赫兹波信号的装置及方法，利用分束片（2）、平面反射镜（3、4、5、6、14、15）、合束片（9）、机械可调延迟系统等简单的器件，使经由分束片（2）分出的两束800nm波长光产生一定的时间相位延迟，共同会聚在空心金属波导光纤（10）中，并依次与400nm波长光脉冲重合发生非线性作用，电离光纤内气体，产生太赫兹波；利用空心金属波导光纤（10）的全反射特性聚拢和传播产生的太赫兹光波。避免了空气中水分大量吸收太赫兹波，改善太赫兹波能量损失，克服了空气拉丝法产生太赫兹波时，两束不同波长光发生非线性作用时间太短，太赫兹波转换效率不高问题，有效地将太赫兹波的信号强度提升了3倍，并且本发明操作简便，成本较低。

Description

基于空心金属波导光纤增强太赫兹波信号的装置及方法 技术领域
本发明涉及一种增强太赫兹波装置，特别涉及一种基于空心金属波导光纤增强太赫兹波信号的装置及方法。
背景技术
近几十年来，太赫兹波以其广泛的应用前景，已成为国际上物理领域的一个重要研究课题。太赫兹辐射是频率在0.1到10THz范围的电磁波，这一波段位于微波与红外之间，具有携带信息量丰富、高时空相干性、低光子能量等特性，在天文、生物、计算机、通信等科学领域有着巨大的应用价值。目前，主要的应用研究有太赫兹时域光谱技术、太赫兹成像技术、安全检查、太赫兹雷达、天文学、通信技术。
目前，以空气拉丝法产生太赫兹波是一种较为常见、简单、可靠的方法。其原理为：波长800nm的激光脉冲会聚通过BBO倍频晶体时，部分转化为波长为400nm的激光。根据激光的相关非线性性质，这两束光在脉冲重合时发生强相互作用，电离气体介质辐射出太赫兹波。
由于两种波长光在介质中传播时产生不同的折射率，它们的传播速度也不相同。而两束光的脉冲宽度都极小，所以两者能够脉宽重合、相互作用产生太赫兹波的时间很短。当两者脉冲随着各自的传播而逐渐分离时，两束光也将停止发生相互作用，不再产生太赫兹信号。这种方法的主要优点是所获得的太赫兹波带宽较宽，整套装置搭建方便，占地空间较小，综合成本相对较低。但同时也存在相干长度较短(通常在毫米量级)，从而在很长一段传播距离内的激光能量无法被有效利用的问题。
此外，空气中含有较多水分，而水对太赫兹波有较强的吸收能力。因此，环境的温度、湿度等条件都会对太赫兹波的产生、探测、与收集等，有十分明显的影响。
以上这些问题都极大地降低了太赫兹波产生的效率和性价比。
发明内容
本发明是针对空气中水分会大量吸收太赫兹波，以及空气拉丝法产生太赫兹波时，两束不同波长光发生非线性作用时间太短，太赫兹波转换效率不高的两个问题，提出了一种基于空心金属波导光纤增强太赫兹波信号的装置及方法，改善太赫兹波能量损失和提升太赫兹波强度。
本发明的技术方案为：一种基于空心金属波导光纤增强太赫兹波信号的装置，激光源发出的波长为800nm的入射激光经过分束片分为两束光，800nm透射光经过平面反射镜组连续反射后，被第一凸透镜会聚进入BBO晶体，并部分转换成波长为400nm的激光，从BBO晶体输出的光包括800nm和400nm的光；800nm反射光经过第一平面反射镜、可调延迟系统、第二平面反射镜和第二凸透镜，与BBO晶体输出的800nm光和400nm光产生一定的时间相位延迟后，共同通过合束片，会聚进入充有干燥气体的空心金属波导光纤中，透射光和反射光经过凸透镜会聚后的焦点都位于空心金属波导光纤入口端，空心金属波导光纤输出太赫兹后被抛物面镜收集，进入探测系统。
所述装置的增强太赫兹波信号方法，打开激光源，在空心金属波导光纤中，初始状态下，从BBO晶体输出的800nm光与400nm光脉冲重合，作为第一束光，向前传输时发生非线性相互作用，电离气体介质辐射出太赫兹波，随着传播距离的增加，此时第一束光的800nm光与400nm光脉冲逐步走离；调节可调延迟系统，使800nm反射光相对脉冲延时，作为第二束光，使得第一束光的800nm光脉冲与400nm光脉冲刚好完全分离时，第二束光800nm反射光的脉冲恰好与400nm光脉冲开始重合，继续产生太赫兹，太赫兹从空心金属波导光纤输出后被抛物面镜收集，进入探测系统。
本发明的有益效果在于：本发明基于空心金属波导光纤增强太赫兹波信号的装置及方法，装置搭建简单，可直接、有效地将太赫兹波的信号强度提升了3倍。本发明的应用范围广，实用性强，操作简便，成本较低，改善太赫兹波能量损失和提升太赫兹波强度。
附图说明
图1为本发明基于空心金属波导光纤增强太赫兹波信号的装置结构示意图；
图2为本发明中利用BBO倍频晶体以空气拉丝法产生太赫兹波原理示意图；
图3为本发明中利用分束片引入第二束800nm光增强太赫兹波信号强度的原理示 意图。
具体实施方式
如图1所示基于空心金属波导光纤增强太赫兹波信号的装置结构示意图，由激光源1、分束片2、平面反射镜3、平面反射镜4、平面反射镜5、平面反射镜6、凸透镜7、BBO晶体8、合束片9、空心金属波导光纤10、抛物面镜11、太赫兹波探测与应用部分12、凸透镜13、平面反射镜14、平面反射镜15、平面反射镜16、平面反射镜17、机械延时系统可移动电机18组成。
激光源1发出的波长为800nm的入射激光经过分束片2后分为两束光。其中透射的第一束800nm光经过由平面反射镜3、4、5、6组成的平面反射镜组连续反射后，被凸透镜7会聚进入BBO晶体7，并部分转换成波长为400nm的激光(此处需特别注意，凸透镜7对第一束800nm光起会聚作用，但并不是把光聚焦到BBO晶体上，因为BBO晶体易受高能激光的损坏)，从BBO晶体7输出的光包括800nm和400nm的光；第二束800nm反射光经过平面反射镜14、17、16、15(其中平面反射镜16、17固定在电机18上构成机械延迟系统)和凸透镜13，与BBO晶体7输出的800nm光和400nm光产生一定的时间相位延迟后，共同通过合束片9，会聚进入充有干燥气体的空心金属波导光纤10中。而两束光经透镜会聚后的焦点都位于空心金属波导光纤10入口端。在空心金属波导光纤10中，初始状态下，第一束800nm光与400nm光脉冲重合，它们向前传输时发生非线性相互作用，电离气体介质辐射出太赫兹波。随着传播距离的增加，第一束800nm光与400nm光脉冲逐步走离。当二者完全分开时，第一束800nm光不再与400nm光发生相互作用产生太赫兹波。通过机械延时系统可移动电机18调节可调延迟系统中两个平面反射镜16、17与第一平面反射镜15、第二平面反射镜14之间的距离，从而控制第二束800nm光相对脉冲延时，使得当第一束800nm光脉冲与通过BBO晶体产生的400nm光脉冲刚好完全分离时，第二束800nm光的脉冲恰好与400nm光脉冲开始重合，从而继续产生太赫兹，最后输出时太赫兹强度可提升为原来的3倍。太赫兹输出后被抛物面镜11收集，进入探测系统12。
在下面的实施例中，以用1∶1分束片分光，波长为800nm入射光通过BBO倍频晶体以拉丝法产生太赫兹汇聚在充有干燥空气的空心金属波导光纤中并应 用于太赫兹为例，其他波段的入射光、不同比例的分束片和在光纤内充入其他种类干燥气体的实施方法与本实施方法基本一致。
具体实现增强太赫兹信号的过程如下：激光源1发出的波长为800nm的入射激光经过1∶1分束片2后分为两束光。其中透射的第一束800nm光经过平面反射镜组连续反射后，被凸透镜7会聚进入BBO晶体7，并部分转换成波长为400nm的激光(凸透镜7对第一束800nm光起会聚作用，但并不是把光聚焦到BBO晶体表面，因为BBO晶体易受高能激光的损坏)；第二束800nm光经过平面反射镜14、17、16、15(其中平面反射镜16、17固定在电机18上构成机械延迟系统)和凸透镜13，与第一束800nm光和400nm光产生一定的时间相位延迟后，共同通过合束片9，会聚在充有干燥气体的空心金属波导光纤10中。而两束光经透镜会聚后的焦点都位于空心金属波导光纤入口端。在空心金属波导光纤中，初始状态下，第一束800nm光与400nm光脉冲重合，如图2所示，它们向前传输时发生非线性相互作用，电离气体介质辐射出太赫兹波。随着传播距离的增加，第一束800nm光与400nm光脉冲逐步走离。当二者完全分开时，第一束800nm光不再与400nm光发生相互作用产生太赫兹波。通过机械延时系统可移动电机18控制第二束800nm光相对脉冲延时，使得当第一束800nm光脉冲与通过BBO晶体产生的400nm光脉冲刚好完全分离时，第二束800nm光的脉冲恰好与400nm光脉冲开始重合，从而继续产生太赫兹，最终输出的太赫兹波强度可提升为原来的3倍。太赫兹输出后被抛物面镜11收集，进入探测系统12。
如图3所示利用分束片引入第二束800nm光增强太赫兹波信号强度的原理示意图，波长为800nm的光脉冲与波长为400nm的光脉冲在三个相干长度Lc的距离内均有重合，并不断发生强相互作用产生太赫兹波。而如图2利用BBO倍频晶体以空气拉丝法产生太赫兹波原理示意图所示，现有的常规空气拉丝法产生太赫兹波的过程中，800nm光与400nm光只在一个相干长度Lc内有重合。因而简单对比，可知本发明的方法将太赫兹波信号强度提升为原来的3倍。
本发明装置一利用分束片、平面反射镜、合束片、机械延时系统等简单的器件，使经由分束片分出的第二束800nm波长光与第一束800nm光产生一定的时间相位延迟，共同会聚在空心金属波导光纤中，并依次与400nm波长光脉冲重合发生非线性作用，电离光纤内气体，产生太赫兹波；装置二利用空心金属波导光纤的全反射特性将聚拢和传播产生的太赫兹光波。这两点设计可针对不同实际情 况分别单独使用，更可以共同使用，从而大幅提升太赫兹波信号强度。

Claims (2)

  1. 一种基于空心金属波导光纤增强太赫兹波信号的装置，其特征在于，激光源发出的波长为800nm的入射激光经过分束片分为两束光，800nm透射光经过平面反射镜组连续反射后，被第一凸透镜会聚进入BBO晶体，并部分转换成波长为400nm的激光，从BBO晶体输出的光包括800nm和400nm的光；800nm反射光经过第一平面反射镜、可调延迟系统、第二平面反射镜和第二凸透镜，与BBO晶体输出的800nm光和400nm光产生一定的时间相位延迟后，共同通过合束片，会聚进入充有干燥气体的空心金属波导光纤中，透射光和反射光经过凸透镜会聚后的焦点都位于空心金属波导光纤入口端，空心金属波导光纤输出太赫兹后被抛物面镜收集，进入探测系统。
  2. 根据权利要求1所述装置的增强太赫兹波信号方法，其特征在于，打开激光源，在空心金属波导光纤中，初始状态下，从BBO晶体输出的800nm光与400nm光脉冲重合，作为第一束光，向前传输时发生非线性相互作用，电离气体介质辐射出太赫兹波，随着传播距离的增加，此时第一束光的800nm光与400nm光脉冲逐步走离；调节可调延迟系统，使800nm反射光相对脉冲延时，作为第二束光，使得第一束光的800nm光脉冲与400nm光脉冲刚好完全分离时，第二束光800nm反射光的脉冲恰好与400nm光脉冲开始重合，继续产生太赫兹，太赫兹从空心金属波导光纤输出后被抛物面镜收集，进入探测系统。
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