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1.
半导体和非线性光学材料在飞秒激光脉冲的激发下,所产生的Terallertz(THz)宽带电磁辐射作为一种新型的超短脉冲光源,可以用于许多超快现象的研究.通常,直接分析THz辐射的时间波形即可获得与其振幅和相位有关的动力学信息.因此,高时间分辨率的THZ辐射波形的精确测量是一个重要的研究课题.另一方面,为了拓宽THz光谱应用的领域,扩展THz辐射的频率范围也是人们不断努力的目标.本文对THz脉冲辐射的电光取样测量中电光晶体的选用、群速色散的取样激光波长以及晶体厚度在测量中所起的作用进行简要的分析,并报告我们近期在宽带T…  相似文献   

2.
实验研究了ZnSe单晶的光学整流THz产生,借助电光取样技术得到THz脉冲的时域波形和FFT频谱分布,观察到约113fs的THz辐射场分布,及相应约5.8THz的频谱分布,辐射峰位于3THz左右.对比研究了不同表面的ZnSe晶体的THz辐射峰值强度随激发光功率的变化,通过轻微烧蚀模型定性解释了高激发功率下THz信号的饱和机制.  相似文献   

3.
实验研究了ZnSe单晶的光学整流THz产生,借助电光取样技术得到THz脉冲的时域波形和FFT频谱分布,观察到约113fs的THz辐射场分布,及相应约5.8THz的频谱分布,辐射峰位于3THz左右.对比研究了不同表面的ZnSe晶体的THz辐射峰值强度随激发光功率的变化,通过轻微烧蚀模型定性解释了高激发功率下THz信号的饱和机制.  相似文献   

4.
THz波的实验研究   总被引:3,自引:1,他引:2  
相干THz(terahertz)波是频率从0.1到几十THz的相干电磁辐射(对应的波长从3 mm~10μm).现代科学技术的发展对THz波的迫切需要,唤起了人们对THz波研究的极大兴趣.近年来,飞秒(10-15s)激光技术的发展和成熟为THz波的研究提供了有效的手段.依据光学整流原理,以飞秒(fs)激光为抽运源,激发非线性电光晶体产生脉宽为亚皮秒量级的宽带相干THz波脉冲是目前实验室较普遍采用的方法.THz时域光谱技术是相干光学选通门技术,它能探测THz波与物质相互作用的时域电场信息,即同时测得电磁波的振幅和相位,因此,可精确测量物质的色散和吸收特性.这种独到的技术特点,使得相干THz辐射脉冲在物理、化学、电子科学、材料科学、层析成像和环境监测等领域有着广泛的应用前景[1].  相似文献   

5.
在电磁波谱中所处的特殊位置使得THz波在物理、化学、生物医学、电子科学、材料科学、环境监测等领域有着广泛的应用前景。讨论了THz时域频谱技术的若干关键问题:THz发射晶体的双光子吸收、衍射效应和非线性效应(Kerr效应和类Kerr效应)等对THz产生效率的影响,THz辐射脉冲的载波包络相位差,THz小波变换频谱技术,以及利用光子晶体光纤飞秒激光作为激发源对THz时域频谱系统进行小型化和提高能量的方案。  相似文献   

6.
刘伟伟  赵佳宇  张逸竹  王志  储蔚  曾斌  程亚 《红外与激光工程》2016,45(4):402001-0402001(7)
通过使用太赫兹(Terahertz,THz)时域光谱系统,探测从不同长度飞秒激光光丝辐射出的THz脉冲,观察到THz波在飞秒激光成丝过程中超光速传输的实验现象。进一步的分析表明:THz波在等离子体光丝区域的折射率小于其在空气中的折射率,这是使得THz波能够在成丝过程中超光速传输的主要原因。由此可以推测:THz脉冲极有可能是在等离子体光丝中进行导引传输的。最后,通过数值模拟获得了光丝区域内的THz本征模式,从而验证了上述推测。  相似文献   

7.
基于非线性光学差频及参量效应的太赫兹源   总被引:1,自引:1,他引:0  
基于非线性光学技术的THz源具有其独特的性能和优点,将基于非线性光学差频原理和光学参量效应,从理论上研究并分析THz波与抽运光、闲频光及相位匹配角之间的关系,得到THz波输出的条件和范围,并设计出宽波段连续可调的THz源。以调QNd∶YAG激光器和光学参量振荡器(OPO)作为抽运源,以GaSe和MgO∶LiNbO3晶体作为差频非线性晶体,根据相位匹配理论及光学参量效应,搭建两套THz波产生系统。其中,基于光学参量效应的THz辐射源有效地产生出THz信号。  相似文献   

8.
Terahertz(THz)电磁辐射是国际上近年来发展的一种新型相干辐射光源,通常可由超短脉冲激光在半导体材料中激发的解态载流子传输过程,非线性光学晶体中的光学整流过程,以及量子阱中的Bloch振荡等过程来产生.THz电磁辐射具有以下非常独特的性质:(1)这是一种频率介于远红外和微波之间的相干电磁辐射,典型的中心频率为1012Hz,即一个THz.(2)单个THz辐射脉冲具有非常大的辐射带宽。其频率带宽与中心频率之比的典型值为△v/v0≈1,甚至大于1;(3)THz辐射的时间波形可用光学手段进行相干测量。如作为探测光源就可以一次得到样…  相似文献   

9.
本文 利用飞秒激光作用于光折变周期性极化铌酸锂(PPLN)晶体和掺 镁(Mg)的PPLN(PP-Mg:LN)晶体通过光整流效应产生窄带太赫兹(THz) 辐射,通过外加磁场的 办法对THz脉冲串的振幅和寿命进行有效控制。随着外加磁场的增强,在光折变PPLN晶体中 产生的THz 波的振幅和寿命都随之减小;当外加磁场足够强时,光折变PPLN晶体中产生的THz波将完 全被抑制。外 加磁场之所以能够对THz波的振幅和寿命进行有效控制,主要是由于洛伦兹力的作用使光折 变晶体内部产生了空间电荷场。  相似文献   

10.
文摘     
在超高速光波形测量中,利用非线性光学效应的光取样法是很有希望的方法.本文报道利用半导体激光放大器(SLA)4波混频的光取样法.本方法与过去的光纤型相比较,体积小,稳定性高,允许信号光波长频带宽.比利用二次谐波发生的方法有希望产生高效率的相互相关信号.利用InGaAs半导体激光放大器和脉冲宽2.5ps的超短探测光,在以1540nm波长为中心的20nm的宽频带,用条纹摄像机实现更高分辨率的光波形测  相似文献   

11.
We report on optimization of the intensity of THz signals generated and detected by optical rectification and electro-optic sampling in dispersive, nonlinear media. Addition of a negative prechirp to the femtosecond laser pulses used in the THz generation and detection processes in 1-mm thick ZnTe crystals leads to an increase of the THz intensity of more than 30% at low laser intensity and up to 60% at higher laser intensity. Dispersion compensation in the ZnTe crystal, which becomes significant for laser pulses with durations much less than 100 fs, is responsible for the enhanced generation and detection efficiency at low excitation intensity, and our simulations indicate that two-photon absorption is responsible for the increased efficiency enhancement observed at high excitation intensity.  相似文献   

12.
光整流太赫兹源及其研究进展   总被引:1,自引:1,他引:0  
邵立  路纲  程东明 《激光与红外》2008,38(9):872-875
太赫兹科学技术是近20年来发展起来的一门新学科,其关键技术是太赫兹波的产生和探测.本文介绍了光整流太赫兹源的辐射原理、国内外研究情况、存在的问题等.今后其发展方向主要应为通过掺杂等手段改进光电导材料的光电特性,提高材料的相位匹配能力和减小饱和现象来提高辐射的功率和效率.  相似文献   

13.
于军立  孟庆龙  叶荣  钟哲强  张彬 《红外与激光工程》2016,45(1):106004-0106004(6)
光整流效应是产生太赫兹波的有效途径之一,而产生高功率太赫兹波则需要采用高强度的飞秒激光激励光整流晶体,但激光强度过大会造成晶体损伤,从而严重影响高功率太赫兹波的输出。因此,对光整流晶体的损伤阈值进行研究具有重要的理论意义与实用价值。通过对飞秒激光与非线性光整流晶体材料相互作用物理过程进行分析,建立了飞秒激光作用下光整流晶体损伤阈值的预估模型,比较分析了铌酸锂、碲化锌和硒化锌三种晶体材料的损伤阈值随飞秒激光脉宽的变化规律。结果表明,当飞秒激光的脉宽相对较小时,光致电离在整个作用过程中占主导地位,随着脉宽的增大,雪崩电离逐渐起主要作用;雪崩电离速率和光致电离速率均与晶体的禁带宽度密切有关,光整流晶体材料禁带宽度越大,晶体材料的损伤阈值越高;铌酸锂晶体的损伤阈值明显高于碲化锌和硒化锌晶体,更适合用于高功率太赫兹波的产生。  相似文献   

14.
Journal of Infrared, Millimeter, and Terahertz Waves - We report on THz pulse generation through optical rectification of femtosecond laser pulses in sugar crystals. The sugar crystals were grown...  相似文献   

15.
For terahertz (THz) wave generators based on organic electrooptic crystals, their intrinsic phonon modes are playing an essential role in THz generation characteristics. Here, this study proposes an effective design strategy for THz phonon mode engineering of organic electrooptic salt crystals for efficient optical‐to‐THz frequency conversion. To reduce phonon‐mode intensity, strongly electronegative trifluoromethyl group acting as strong hydrogen‐bond acceptor is incorporated into molecular anions. New 2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 4‐(trifluoromethyl)benzenesulfonate (HMQ‐4TFS) crystals exhibit a relatively small absorption coefficient in the THz spectral range between 0.5 and 4 THz, which is attributed to suppressed molecular vibrations due to strong hydrogen bonds involving the 4TFS anion. In addition, HMQ‐4TFS crystals possess a very large macroscopic optical nonlinearity, comparable (or even higher) to benchmark stilbazolium crystals. Based on the low‐intensity THz phonon modes and the large optical nonlinearity, a 0.37 mm thick HMQ‐4TFS crystal pumped with 150 fs infrared laser pulses facilitates very efficient THz wave generation by optical rectification, delivering 23 times higher peak‐to‐peak THz electric field than the widely used standard inorganic ZnTe crystal (1.0 mm thick) and a broader spectral bandwidth. Therefore, strongly electronegative groups introduced into molecular salt electrooptic crystals provide a very promising design strategy of THz phonon mode engineering for developing intense broadband THz sources.  相似文献   

16.
We demonstrate the presence of dual simultaneous nonlinear mechanisms: field-induced optical rectification (FIOR) and field-induced surge current (FISC) for the generation of terahertz (THz) pulses from p-type and n-type Fe:In0.53Ga0.47As surfaces upon excitation with femtosecond laser pulses centered at 800 nm wavelength. Experimental investigations of the dependence of the generated THz waves on the incident angular optical polarization, optical irradiance, and the direction and magnitude of applied electric DC fields give confirming results to the proposed THz generation mechanisms. Applying external DC electric fields in the plane of the incident optical field shows efficient capability in manipulating the direction and phase of the generated THz waves, and controlling the refractive index of Fe:In0.53Ga0.47As material in the THz range, in addition to enhancing the emitted THz power up to two orders of magnitude. The fast and reliable response of Fe:In0.53Ga0.47As to the changes in the direction and magnitude of the optical and electrical fields suggests its use in amplitude and phase modulators, and ultrafast optoelectronic systems.  相似文献   

17.
介绍了基于非线性光学参变过程产生和放大中红外可调谐超短激光脉冲的主要方法,比较了参变振荡、差频产生、光学参变放大和啁啾脉冲光学参变放大等4种产生与放大方法的技术特点,重点评述了最近10年来国内外利用光学参变放大和啁啾脉冲光学参变放大实现大增益宽带和高峰值功率输出的最新进展.探讨了获得更高能量/功率和更短脉冲(更大带宽)...  相似文献   

18.
We report the observation of strong narrowband terahertz emission at 10.6 THz from the common nonlinear second harmonic generation crystal β-barium borate crystal excited by 40 fs laser pulses at a 800 nm center wavelength. The emitted THz field amplitude is linear with incident pump energy with no saturation observed up to 2 mJ of pump pulse energy, and exhibits a crystal azimuthal angular dependence consistent with an optical rectification process. The narrowband emission can be explained by the large dispersion caused by optical phonons in the vicinity of the emission energy.  相似文献   

19.
THz射线产生技术及应用最新进展   总被引:7,自引:0,他引:7  
THz电磁脉冲是由超短激光脉冲选通半导体光导开关后产生的超宽频带电磁辐射,在很多基础研究领域、工业应用领域以及军事领域中有相当重要的应用。作者就THz电磁脉冲的产生技术、探测技术作了较全面的评述。对其若干重要应用研究成果包括THz时域光谱技术(TDS)、THz二维成像技术等也进行了分析。  相似文献   

20.
The authors report the use of an optoelectronic system for the measurement of terahertz (THz) pulses by using chirped pulse technology. This system measures the spatio-temporal distribution of free-space pulsed radiation with an unprecedented data acquisition-rate. Using a linearly chirped optical probe pulse with an electro-optic crystal, a temporal waveform of a copropagating THz field is linearly encoded onto the frequency spectrum of the optical probe pulse and then decoded by dispersing the probe beam from a grating to a detector array. Acquisition of picosecond THz field pulses without using mechanical time-delay devices have been achieved. A single-shot electro-optic measurement of the temporal waveform of a THz pulse has been demonstrated. Unparalleled by other THz sampling techniques, this single-shot method provides what is believed to be the highest possible data-acquisition rate. Temporal resolution, sensitivity, optimal optical bias point of electro-optic modulation, potential applications, and possible improvements are also discussed. In principle, this technique can also be used in magneto-optic measurements  相似文献   

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