共查询到11条相似文献,搜索用时 15 毫秒
1.
2.
High quality Ge was epitaxially grown on Si using ultrahigh
vacuum/chemical vapor deposition (UHV/CVD). This paper demonstrates
efficient germanium-on-silicon p-i-n photodetectors with 0.8~μm
Ge, with responsivities as high as 0.38 and 0.21~A/W at 1.31 and
1.55~μ m, respectively. The dark current density is
0.37~mA/cm2 and 29.4~mA/cm2 at 0~V and a reverse bias of
0.5~V. The detector with a diameter of 30~μ m, a
3~dB-bandwidth of 4.72~GHz at an incident wavelength of 1550~nm and
zero external bias has been measured. At a reverse bias of 3~V, the
bandwidth is 6.28~GHz. 相似文献
3.
Detection of the spatiotemporal field of a single-shot terahertz pulse based on spectral holography 下载免费PDF全文
According to electro-optical sampling theory, we propose a new method to detect the spatiotemporal field of a single- shot terahertz pulse by spectral holography for the first time. The single-shot terahertz pulse is coupled into a broadened chirped femtosecond pulse according to electro-optical sampling theory in the detecting system. Then the reference wave and the signal wave are split by Dammann grating and spread into the interference band-pass filter. The filtered sub-waves are at different central-frequencies because of the different incident angles. These sub-waves at different central-frequencies interfere to form sub-holograms, which are recorded in a single frame of a charge coupled device (CCD). The sub-holograms are numerically processed, and the spatiotemporal field distribution of the original terahertz pulse is reconstructed. The computer simulations verify the feasibility of the proposed method. 相似文献
4.
A detailed numerical study of dynamical behavior of a semiconductor laser under current modulation and cavity detuning has been performed on the base of four different models of the active medium which take into account direct transitions between ground subbands, transitions with no k-selection rule between ground subbands and contribution of excited subbands in each of the above-mentioned cases. We have shown that different nonlinear regimes (period doubling, chaos, generalized bistability) can be obtained either with cavity detuning from the gain band maximum or near the laser threshold.It has been established that the shape and principal peculiarities of amplitude detuning characteristics are determined by the relation between the current modulation frequency and maximum resonance frequency of the laser.PACS numbers: 05.45.Pq, 42.55.Px, 42.65.Sf 相似文献
5.
王中结 《原子与分子物理学报》2007,24(3):591-595
解析地分析了在囚禁离子中由热库导致量子退相干的控制问题,提出了一个基于热库调制的抑制退相干的一般方法.热库的调制可利用外加的光场与离子相互作用来实现.应用这个方法,适当地选择热库调制参数,可以有效消除量子退相干.计算表明:在高的调制频率下,用这个机制来抑制退相干的效果与宇称激励机制相似.宇称激励机制不仅要求外场是±π脉冲而且要求脉冲既快又强,而热库调制机制仅要求外场频率足够高,因此,热库调制机制优于宇称激励机制. 相似文献
6.
7.
J. S. Bakos G. P. Djotyan P. N. Ignácz M. Á. Kedves M. Serényi Zs. Sörlei J. Szigeti Z. Tóth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(1):59-66
The spatial displacement of the 85Rb atoms in a
Magneto-Optical Trap (MOT) under the influence of series of frequency
modulated light pulse pairs propagating opposite to each other is measured
as a function of the time elapsed after the start of the pulse train, and
compared with the results of simulations. Adiabatic excitation and
consecutive de-excitation take place between the ground
52S1/2 (F=3) and the 52P3/2 (F'=2, 3, 4) excited levels as the result of
the interaction. The displacement of the 85Rb atoms is calculated as
the solution of simple equation of motion where the expelling force is that
arising from the action of the frequency modulated light pulses. The
restoring and friction forces of the MOT are taken into account also. The
system of Bloch equations for the density matrix elements is solved
numerically for transitions between six working hyperfine levels of the atom
interacting with the sequence of the frequency modulated laser pulses.
According to these simulations, the momentum transferred by one pulse pair
is always smaller than the expected 2ħk, (1) where ħ is the Plank constant and
k=2π/λ where λ is the wavelength, (2) having a maximum
value in a restricted region of variation of the laser pulse peak intensity
and the chirp. 相似文献
8.
提出了q-奇相干场与级联型三能级原子相互作用的非线性理论,求得了在相互作用绘景中薛定谔方程的形式解及其在其态下的期望值。利用数值计算讨论了q形变对相互作用中场的反聚束效应的影响。经研究发现,q形变对反聚束效应的调制能力很强,反映出了q形变的非线性行为对量子相干性的干扰以及对量子特性的影响。当q→1时,恢复为普通的线性理论。 相似文献
9.
q形变光场与级联型三能级原子相互作用中场的压缩效应 总被引:1,自引:0,他引:1
建立了q形变光场与级联型三能级原子相互作用的非线性理论,求得相互作用绘景中薛定谔方程的形式解,利用数值计算讨论了q形变对相互作用中场压缩效应的影响并与q-偶相干光场的情形做了对比分析。研究发现,q偏离1的程度越大,q形变对场压缩效应的调控能力越强,反映出q形变的非线性行为对量子相干性的干扰以及对量子特性的影响。当q→1时,恢复为普通线性理论。和q-偶相干光场的情形做的对比分析,反映出q-奇相干光场不仅不存在压缩效应,还会弱化压缩效应。这与q-偶相干光场和q-奇相干光场存在不同的量子效应的结论完全一致。 相似文献
10.
Y. F. Chen M. T. Chang W. Z. Zhuang K. W. Su K. F. Huang H. C. Liang 《Laser \u0026amp; Photonics Reviews》2015,9(1):91-97
A novel scheme to multiply the repetition rate of a monolithic self‐mode‐locked laser for generating sub‐terahertz pulse sources is successfully demonstrated. A coated Yb:KGW crystal is designed to achieve a self‐mode‐locked operation at a repetition rate of 24 GHz with an average output power exceeding 1.0 W at a pump power of 4.8 W. A partially reflective mirror is utilized to combine with the output surface of the gain medium to constitute an external Fabry‐Perot cavity. It is theoretically and experimentally verified that adjusting the external cavity length to satisfy the commensurate condition can lead to the frequency spacing to be various order harmonics of the mode spacing of the monolithic cavity. The maximum pulse repetition rate of the laser output can be up to 216 GHz and the pulse duration is as short as 330 fs. More importantly, the overall characteristics of the first‐order temporal autocorrelation traces obtained by sequentially scanning the external cavity.length display an intriguing phenomenon of temporally fractional revivals, similar to the feature of spatial Talbot revivals.
11.
Yuriy Serozhkin Olexiy Kollyukh Yevgen Venger 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(8):1517-1526
We present the results of measurement of grains vibrations under external action in gas and liquid with a laser heterodyne receiver of scattered radiation. For investigation of dynamic characteristics of particles we made the laser heterodyne receiver with sensitivity about 2×10−17 W/Hz and source of probing with radiation power 1 mW. In our pilot experiments, measurement of vibration amplitude of nanoparticles in gas (cigarette smoke) and microparticles in fluid (toothpaste in water) was made. We measured values of vibration amplitudes about 20–30 nm. 相似文献