Polarization Self-Modulation Phenomenon in a Free Oscillated Nd: YAG Laser

Polarization self-modulation effect in a free oscillated Nd:YAG laser is investigated after a quarter wave plate is introduced independently in the two positions of the cavity. As described in the previous experiments, the intensity components in the orthogonal directions are modulated with a period of the round-trip time or twice. Different pulse shapes reveal that the seed field from the spontaneous emission is not uniform and seems to be stochastic for each pulse.

Frequency characteristics and dynamical behaviors of self-modulation in vertical-cavity surface-emitting lasers

The frequency characteristics of a VCSEL with a quarter-wave plate (QWP) and an external reflector are investigated with the translation matrix of the vectorial field. Two series of eigenmode with a shift of half the free spectrum range are linearly polarized, respectively, along the neutral axes of QWP. We also numerically explore the polarization self-modulation phenomenon by using a vectorial laser equation and considering the inhomogeneous broadening of the gain medium. If the external cavity is so short that the shift is bigger than the homogeneous broadening, two stable longitudinal modes oscillate, respectively, on the neutral axes of QWP because they consume different carriers. With a long external cavity, the competition of the modes for the common carriers causes the intensity fluctuation of the modes with a period of one round-trip time of the external cavity.

Laser wakefield and self-modulation of driving pulse

A self-consistent theory of plasma response to a single laser beam is proposed. The driving pump is not viewed as invariant during its interaction with the plasmas. Its modulation by the plasmas has an obvious influence on the strength of the wakefield behind the pulse. This suggests that the compression of the low-intensity pulse by the plasmas might be a possible way to excite largae-amplitude wakefield. (C) 2003 American Institute of Physics.

Self-focusing, Raman, and modulation instability of shaped relativistic laser pulse in plasmas

The interaction of shaped laser pulses with plasmas is studied in a strict theoretical framework without adopting the slow-varying envelope approximation (SVEA). Any physical quantities involved in the interaction are denoted as a summation of different real quantities of respective phases. The relationships among the phases of those real quantities and their moduli are strictly analyzed. Such strict analyses lead to a more exact equation set for the three-dimensional envelope of the laser pulse, which is not based on SVEA. Based on this equation set, self-focusing, Raman, and modulation instabilities could be discussed in a unified framework. The solutions of this equation set for the laser envelope reveal many possible multicolor laser modes in plasmas. The energy and the shape of a pulse determine its propagation through plasmas in a multicolor mode or in a monochromic mode. A global growth rate is introduced to measure the speed of the transition from the monochromic mode in vacuum to a possible mode in plasmas. (c) 2006 American Institute of Physics.

Phase control of cross-phase modulation with electromagnetically induced transparency

We investigate a four-level double-Lambda atomic scheme interacting with four laser fields, a weak probe field, a weak signal field and two driven fields, in a closed-loop configuration. We study the Kerr nonlinearity associated with cross-phase modulation based on electromagnetically induced transparency. Our results show, in this closed-loop system, that the strength of cross-phase modulation and two-photon absorption are dependent critically on the relative phase between the excitation paths. By choosing the parameters appropriately, large cross-phase modulation can be achieved within a wide transparency window, while two-photon absorption is cancelled completely. The strength of cross-phase modulation can be enhanced much more by decreasing the intensities of two driven fields.

Tunneling-induced large cross-phase modulation in an asymmetric quantum well

We propose an asymmetric double AlGaAs/GaAs quantum well structure with a common continuum to generate a large cross-phase modulation (XPM). It is found, owing to resonant tunneling, that a large XPM can be achieved with vanishing linear and two-photon absorptions. (c) 2007 Optical Society of America.

Novel method to construct a quality map for phase unwrapping based on modulation and the phase gradient

A novel method to construct a quality map, called modulation-phase-gradient variance (MPGV), is proposed, based on modulation and the phase gradient. The MPGV map is successfully applied to two phase-unwrapping algorithms - the improved weighted least square and the quality-guided unwrapping algorithm. Both simulated and experimental data testify to the validity of our proposed quality map. Moreover, the unwrapped-phase results show that the new quality map can have higher reliability than the conventional phase-derivative variance quality map in helping to unwrap noisy, low-modulation, and/or discontinuous phase maps. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

Novel method to construct a quality map for phase unwrapping based on modulation and the phase gradient

A novel method to construct a quality map, called modulation-phase-gradient variance (MPGV), is proposed, based on modulation and the phase gradient. The MPGV map is successfully applied to two phase-unwrapping algorithms - the improved weighted least square and the quality-guided unwrapping algorithm. Both simulated and experimental data testify to the validity of our proposed quality map. Moreover, the unwrapped-phase results show that the new quality map can have higher reliability than the conventional phase-derivative variance quality map in helping to unwrap noisy, low-modulation, and/or discontinuous phase maps. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

Spectral narrowing of negatively chirped femtosecond pulse by cross-phase modulation in a single-mode optical fiber

We demonstrate theoretically that the negatively chirped femtosecond laser pulse can be spectrally narrowed by cross-phase modulation. The new view is well Supported by numerical simulation. The negative chirp method in fibers might be useful in all optical wavelength switching applications. (c) 2005 Elsevier B.V. All rights reserved.

Electro-optic modulation of light propagating near the optic axis with any polarization in uniaxial crystals

The electro-optic effect in uniaxial crystals for light propagating near the optic axis with any polarization has been analyzed. The passive and the electrically induced birefringences and the rotation of polarization direction in crystals have been calculated, and the conoscopic interference figures under orthogonal polariscopes for different polarizer directions have been plotted. The extinction areas caused by the rotation of polarization direction in crystals change with the polarizer direction, but the two heads of the induced optical axes do not vary, which are always on the induced principal axis with bigger refractive index. The directions of polariscopes are always extinction, and the +/- 45 degrees directions with polarizer are always complete transmission. The conoscopic interference figures for LiNbO3 crystals have been demonstrated experimentally by rotating polariscopes directions, which accord with the theoretically calculating plots. (c) 2006 Elsevier GmbH. All rights reserved.

Effect of Co-administration of Morphine and Cholinergic Antagonists on Y-maze Spatial Recognition Memory Retrieval and Locomotor Activity in Mice

吗啡和胆碱能系统的相互作用已在多项研究中提到,本实验想查明吗啡是否能和胆碱能拮抗剂、东莨菪碱以及阿托品共同作用对小鼠的Y迷宫空间识别记忆提取产生影响.采用测试前腹腔给药的方法,选用3种剂量的吗啡(5、1.5、0.5mg/kg),两种剂量的东莨菪碱(1、0.1mg/kg),以及两种剂量的阿托品(0.5、0.1mg/kg),剂量由高到低相配对作为联合给药的手段.其结果表明:1)0.5mg/kg低剂量吗啡与0.1 mg/kg低剂量的东莨菪碱,或与0.1 mg/kg低剂最的阿托品联合给药的小鼠,在记忆提取测试中, 空间探查行为(各臂停留时间百分比)对新异臂没有偏好,而新奇探索行为(各臂访问次数百分比)仍保持了对新异臂的偏好,而相应剂最药物单独给药的小鼠记忆提取均没有被损害;2)吗啡能和东莨菪碱相互作用使小鼠的活动性显著增强.暗示吗啡和胆碱能拮抗剂对小鼠空间记忆提取的破坏存在一定程度的相互作用.