LD泵浦Cr4+∶YAG被动调Q锁模Nd∶Gd0.42Y0.58VO4激光器

理论和实验研究了LD泵浦Nd∶Gd0.42Y0.58VO4/Cr4+∶YAG被动调Q锁模激光器.在分析Cr4+∶YAG晶体能级结构和调Q锁模物理过程的基础上,通过数值模拟给出了Cr4+∶YAG调Q锁模的参量要求,然后进行了实验验证.实验中Cr4+∶YAG的初始透过率T0分别为86.3%、95%,输出镜的透过率T分别为10%、20%,在其他条件不变的情况下构成四种不同的组合,均实现了激光器的调Q锁模运转.实验结果表明,降低Cr4+∶YAG的初始透过率T0或提高输出镜透过率T有利于获得较好的锁模效果,与理论分析一致.     

Terahertz generation in quantum cascade structures by two-color deriving fields: An approach to reach inversion population via optical pumping

In this paper, a quantum cascade laser (QCL) design is proposed based on GaAs/AlGaAs material system, which simultaneously operates at three widely separated wavelengths (${\lambda }_1=11.1\mu m,{\lambda }_2=14.1\mu m$ and ${\lambda }_{THz}=60\mu m$). In the design, all the wavelength radiations are achieved by the engineering of the electronic spectrum via the quantum-well widths and the applied electric field in a single active region within a same waveguide. The mid-infrared (mid-IR) wavelengths are obtained by adoption a dual-upper-state active region, and the proposed design aims to use both the mid-IR radiations as the coherent deriving fields to populate the upper THz lasing state to aid the THz-laser population inversion via optical pumping instead of direct electrical injection. A detailed analysis of electronic transport in the structure is carried out using a multi-level rate-equation model. The results show that the proposed structure offers an alternative approach to room temperature THz generation in QCLs.     

Stability of a Laser-diode-pumped Cr~(4 )∶YAG Passively Q-switched Nd~(3 )∶YAG Laser

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The Effect of Incoherent Population Pumping on Squeezing in Resonance Fluorescence

1　ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｑｕｅｅｚｅｄｓｔａｔｅｓｏｆｒａｄｉａｔｉｏｎｆｉｅｌｄｈａｓｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙｉｎｖｅｓｔｉｇａｔｅｄ[1].Ｂｏｔｈｔｈｅｏｒｅｔｉｃａｌａｎｄｅｘｐｅｒｉｍｅｎｔａｌｓｔｕｄｉｅｓｈａｖｅｓｈｏｗｎｔｈａｔｔｈｅｒｅｓｏｎａｎｃｅｆｌｕｏｒｅｓｃｅｎｃｅｏｆａｄｒｉｖｅｎａｔｏｍｃａｎｓｅｒｖｅａｓａｓｏｕｒｃｅｏｆｎｏｎｃｌａｓｓｉｃａｌｌｉｇｈｔ.Ｆｏｒｅｘａｍｐｌｅ,ＣａｒｍｉｃｈａｅｌａｎｄＷａｌｌｓ,ａｎｄＫｉｍｂｌｅａｎｄＭａｎｄｅｌ[2…     

Steady state Behaviour of a Three level Ladder Atomic System with Incoherent Population Pumping in a Squeezed Vacuum

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Dissipation, decoherence and preparation effects in the spin-boson system

The dynamics of the reduced density matrix of the driven dissipative two-state system is studied for a general diagonal/off-diagonal initial state. We derive exact formal series expressions for the populations and coherences and show that they can be cast into the form of coupled nonconvolutive exact master equations and integral relations. We show that neither the asymptotic distributions, nor the transition temperature between coherent and incoherent motion, nor the dephasing rate and relaxation rate towards the equilibrium state depend on the particular initial state chosen. However, in the underdamped regime, effects of the particular initial preparation, e.g. in an off-diagonal state of the density matrix, strongly affect the transient dynamics. We find that an appropriately tuned external ac-field can slow down decoherence and thus allow preparation effects to persist for longer times than in the absence of driving. Received 23 October 1998 and Received in final form 26 February 1999     

The Effect of Incoherent Population Pumping on Squeezing in Resonance Fluorescence

The effect of incoherent population pumping on the steady-state population inversion and the quadrature squeezing spectra produced in the resonance fluorescence of a two-level atom is investigated. In the presence of incoherent population pumping, the steady-state population inversion is increased for small frequency detuning but is not changed for large frequency detuning. For resonant excitation at low intensities, the weak incoherent pumping degrades the degree of the squeezing and shifts the position of the maximum squeezing; for off-resonant excitation at strong intensities, the weak incoherent pumping hardly changes the squeezing spectra. But when the incoherent pumping is strong the squeezing may be completely destroyed for both cases.     

An apparatus for NMR of laser polarized 129Xe on single crystal surfaces

Due to a lack of at least 2 orders of magnitude in the amount of sample nuclei, single crystal surfaces are out of reach for conventional NMR measurements. Our aim is to prove that highly polarized ¹²⁹Xe provides a technique to overcome this restriction. Therefore an apparatus for polarizing ¹²⁹Xe up to 0.7 by spin transfer from optically pumped Rb has been designed as well as an NMR spectrometer in combination with a UHV chamber with sample cleaning, cooling and characterization abilities and a special manifold of glass stopcocks with a liquid nitrogen cooled trap for dosing nitrogen free polarized Xe into the chamber onto the surface. This revised version was published online in August 2006 with corrections to the Cover Date.     

重频XeF蓝绿激光技术

 利用表面放电光泵浦技术,研制了重频XeF(C-A)激光器,运行频率达到10 Hz。研究了运行频率、气体流量对激光输出能量稳定性的影响,分析了影响输出稳定性的主要因素,实验结果表明,提高气流量可有效改善重频输出能量的稳定性。同时,还给出了优化实验条件下不同运行频率连续20个脉冲较为理想的输出结果。运行频率分别为1,2,5 Hz时,输出能量稳定性较好,输出能量大于4.0 J;气流量大于53 L/s时,10 Hz重频运行的输出稳定性已显著提高,平均输出能量也达到1.8 J。