Stimulated Raman scattering of pre-gaussian light

The quantum theory of a forward Stokes generation by means of stimulated Raman scattering is considered in the case of a pre-gaussian pump composed by two and three telegraphs. As for the case of a colored chaotic pump the mean Stokes intensity is found to be enhanced over that resulting from a coherent pump in both transient and steady-state limits. In the limit that the pre-gaussian bandwidth becomes large, the mean Stokes intensity also becomes identical with that resulting from a coherent pump.     

抽运光分布对二极管抽运激光器振荡光光束质量的影响

研究了二极管抽运激光器（DPL）中抽运光的空间分布对振荡光光束质量的影响.通过对端面 抽运情形下光场运动方程的研究，发现不均匀的空间增益分布会影响激光振荡的模式，并且 使得基模振荡光偏离高斯分布.引入一个称之为抽运光影响因子参数，来判断这种影响的程 度.研究表明，这个参数计算方便而且实用.在对基模调Q脉冲激光的研究中发现，由于抽运 光的影响，脉冲前沿的场分布将由远离高斯分布向接近高斯分布变化，称之为脉冲前沿的场 倏变现象. 关键词： 激光二极管 二极管抽运激光器 光束质量     

Spectral encoding of the polarization state of light in multiplexed polarization-sensitive lasing structures

We report the experimental demonstration of spectral encoding of the polarization state of light by use of multiplexed distributed-feedback lasers in a dye-doped organic thin film by exploiting the pump polarization selectivity of the superimposed resonators. Measurement of the Stokes parameters of the pump light without a priori knowledge of the lasing properties of the structure is discussed.     

Observation of the Rabi oscillation of light driven by an atomic spin wave

Coherent conversion between a Raman pump field and its Stokes field is observed in a Raman process with a strong atomic spin wave initially prepared by another Raman process operated in the stimulated emission regime. The oscillatory behavior resembles the Rabi oscillation in atomic population in a two-level atomic system driven by a strong light field. The Rabi-like oscillation frequency is found to be related to the strength of the prebuilt atomic spin wave. High conversion efficiency of 40% from the Raman pump field to the Stokes field is recorded and it is independent of the input Raman pump field. This process can act as a photon frequency multiplexer and may find wide applications in quantum information science.     

Extraordinary variation of pump light intensity inside a four-level solid-state laser medium

A theoretical investigation of the absorption of the pump light at different intensities through a four-level solid-state laser medium is presented. It is found that the variation of the pump intensity inside the laser medium cannot always simply be dominated by Beer's law. Transmission of the pump light through this laser medium is closely related to the pump intensity itself. In fact, when the pump intensity is relatively low, whose values depend on the characteristics of the medium, the variation of the pump light through the laser medium is consistent with Beer's law. However, while the pump intensity is high enough, the relationship between the transmission of the pump light and its propagation distance is demonstrated to be linear. These theoretical results have been confirmed by the experiment with a medium of YAG:Nd.     

三能级固体激光介质对抽运光吸收的理论研究

从激光介质中光能量的传输方程和描述脉冲激光的能级跃迁速率方程出发，研究了激光介质对抽运光的吸收特性.理论分析表明，固体激光介质对抽运光的吸收不仅是指数函数吸收方式，当抽运光的能量密度增大到一定程度时激光介质对抽运光的吸收变为非指数函数吸收，吸收深度增加.以红宝石晶体为例进行了具体的理论计算，结果显示出了随抽运光能量密度增大介质吸收的变化规律. 关键词： 抽运 激光介质 光传输方程 光吸收     

Collective processes during stimulated light scattering

An approach to the analysis of the phase conjugation by stimulated light scattering that is alternative to the mode theory of 3D hologram, which is usually applied for these purposes, has been studied. As is known, the use of the mode theory is based on the phenomenological gain factor of the Stokes wave, which is induced by a pump wave in a nonlinear medium. The approach developed in this work directly considers the interaction between plane components of the pump and Stokes waves via hypersonic gratings of the dielectric permittivity, which the pump and Stokes waves induce in the medium. It has been shown that, as a result of the phase conjugation, two hypersonic gratings participate equally efficiently in the interaction between any pair of plane components of the pump and Stokes waves, with one of these gratings being excited by the interacting waves themselves. The other grating in each such pair is unambiguously identified with a simplest vector diagram. Conditions have been analyzed under which numerous other gratings, which could also participate in the interaction of each pair of plane components of the pump and Stokes waves without violating the Bragg conditions and the joining conditions of the transverse components of the wave vectors at the interface between the two media, contribute negligibly to stimulated light scattering. It has been shown that, if the pump is spatially coherent, the considered approach yields the same results as the standard mode theory does. In October 2011, I reported the results of this work at the Vavilov State Optical Institute at the Memorial Meeting “Half a Century of New Optics in Russia: Lasers, Nonlinear Optics, and Optical Holography” and at the International Conference “Laser Optics—2012” (June 2012).     

Broadband Brillouin slow light with multiple-longitudinal-mode,tunable pump

We propose and demonstrate broadband Brillouin slow light using a multiple-longitudinal-mode tunable fiber laser as Brillouin pump. A tunable broadband Brillouin pump with a tuning range from 1 520 to 1 555 nm is generated using a fiber ring laser with a semiconductor optical amplifier (SOA) as its gain medium. The pump spectrum consists of a large number of longitudinal modes separated by 6 MHz. The 3-dB bandwidth is about 11.5 GHz, and its fluctuation is less than 100 MHz within the tuning range. An 8-Gb/s data signal can be delayed by up to 83.0 ps (bit error rate < 10 9) at 17-dBm pump power.     

非线性光纤环镜在受激布里渊散射慢光级联系统中的可行性研究

基于非线性光纤环镜(NOLM)的脉冲压缩特性,分析了NOLM在基于受激布里渊散射(SBS)慢光级联系统中对延迟脉冲的影响.利用环形结构来模拟多次级联,有效地降低了系统的复杂度,得到了在不同抽运光功率和级联次数下脉冲的延迟输出特性.理论分析表明,NOLM可以有效地抑制SBS慢光级联系统中延迟脉冲的展宽,抽运光功率决定了展宽因子的变化趋势及最终稳定值的大小,展宽因子在级联4次时趋于稳定值,恰当选取抽运光功率可实现脉冲的零展宽延迟;改变抽运光功率和级联次数可以实现延迟量的连续可调,且延迟量理论上不受限制;增大抽 关键词： 慢光 脉冲压缩 非线性光纤环镜 受激布里渊散射     

Time-modulated entangled states of light

We investigate time-modulated EPR entangled states and intensity quantum correlation of twin light beams in application to time-resolved quantum communication. As a proper device generating such states, the nondegenerate optical parametric oscillator driven by the time-modulated pump field is considered. The text was submitted by the authors in English.     

Effect of Brillouin slow light on distributed Brillouin fiber sensors

The effect of Brillouin slow light on distributed Brillouin fiber sensors (DBFSs) is studied. We demonstrate Brillouin slow light for a 1.2 ns pulse with peak powers (PS) from 3.3 to 56.2 mW on depletion of the pump power (PP) ranging from 1.3 to 83.2 mW in conventional optical fibers (SMF-28). Experiments show that, when pump power depletion is not negligible, for a given PP the Brillouin gain and delay time of a pulse decrease when PS increases in a long (> or =10 km) sensing fiber. The optimum pump beam depletion resulting from strong interaction of the pump and the probe in the fiber provides accurate temperature and strain information at a high spatial resolution. Our study reveals that at low PP the spatial resolution error caused by the pulse delay for a DBFS with centimeter spatial resolution is less than 5% of the pulse length.     

Broadband light generation by noncollinear parametric downconversion

Broadband light generation is demonstrated by noncollinear spontaneous parametric downconversion with a cw pump laser. By use of a suitable noncollinear phase-matching geometry and a tightly focused pump beam, downconverted signals that feature a bell-shaped spectral distribution with a bandwidth approaching 200 nm are obtained. As an application of the generated broadband light, submicrometer axial resolution in an optical coherence tomography scheme is demonstrated; a free-space resolution down to 0.8 microm was achieved.     

Ultrafast tilting of the dispersion of a photonic crystal and adiabatic spectral compression of light pulses

We demonstrate, by theory and experiment, the ultrafast tilting of the dispersion curve of a photonic-crystal waveguide following the absorption of a femtosecond pump pulse. By shaping the pump-beam cross section with a nanometric shadow mask, different waveguide eigenmodes acquire different spatial overlap with the perturbing pump, leading to a local flattening of the dispersion by up to 11%. We find that such partial mode perturbation can be used to adiabatically compress the spectrum of a light pulse traveling through the waveguide.     

Slow and fast light based on SBS with the spectrum tailoring

In this paper, slow and fast light of a signal pulse of nanosecond duration are achieved in the same experimental device by using band-pass filters to tailor the spectra of spontaneous Brillouin scattering (SPBS) coming from 50 km single-mode optical fibers (SMF) as the pump light. The phase matching condition of slow and fast light is satisfied by changing wavelengths of band-pass filters .In our experiment, we obtain the tunable delay time for various signal pulses range from 1 ns to 20 ns. By increasing the power of the pump field to 16 mW, a 1 ns signal pulse is delayed 1.5 ns and is advanced 1.0 ns respectively, while the signal pulse almost has no distortion. The experiment has demonstrated that larger relative pulse delay of slow and fast light can be obtained in the same experimental setup when pump power is lower.     

Quasi-phase-matched generation of tunable blue light in a quasi-periodic structure

We present what is to our knowledge a new approach to generating tunable blue light by cascaded nonlinear frequency conversion in a single LiTaO3 crystal. Simultaneous quasi-phase matching of an optical parametric generation process and a sum-frequency mixing process is achieved by means of structuring the crystal with a quasi-periodic optical superlattice. The spectral (wavelength tuning and bandwidth) and power characteristics of the blue-light generation are studied with a fixed-wavelength 532-nm picosecond laser and a wavelength-tunable nanosecond optical parametric oscillator (OPO) as the pump sources. By tuning the OPO wavelength, we could tune the blue output over approximately 20 nm. Temperature tuning of the blue output at a fixed pump wavelength of 532 nm was limited to approximately 1.5 nm. A maximum blue power of 15 microW was generated at a pump power of 0.5 mW, corresponding to an efficiency of 3%.     

Room-temperature slow light with semiconductor quantum-dot devices

We demonstrate room-temperature slow light that is electrically and optically controllable by using a quantum-dot (QD) semiconductor optical amplifier (SOA) at zero and low bias below the transparency current. The absorption spectrum of the QD SOA exhibits a spectral dip with a corresponding group-index dispersion and group delay owing to coherent population oscillation caused by the interaction of pump and probe laser light near resonance of the first heavy-hole-conduction-state transition. At an optical pump power of approximately 0.3 mW inside the single-mode waveguide without current injection, a group-index change of 3.0 with a bandwidth of 2 GHz was measured. This group-index change can be controlled by injection of electrical current and by changing the optical pump power.     

25 GHz bandwidth Brillouin slow light in optical fibers

Broadband slow light is demonstrated by using stimulated Brillouin scattering in optical fibers based on a double Brillouin pump, the peaks of which are spectrally separated by twice the Brillouin frequency. The loss spectrum generated by one of the pump waves is fully compensated by the gain spectrum of the other one, which permits the enlargement of the bandwidth to 25 GHz and a variable time delay of up to 10.9 ps with 37 ps pulses.     

Efficient conical emission of stimulated Raman Stokes light generated by a Bessel pump beam

Stimulated Raman scattering in H(2) gas was studied with a Bessel pump beam, which was generated with a binary phase grating. The first Stokes light was emitted along the surface of a cone, the angle of which was equal to the cone angle of the Bessel pump beam multiplied by the ratio of the wavelengths of the Stokes and pump beams. High conversion efficiency into the first Stokes light of as much as 60% was achieved, indicating that the complete Bessel J(0) mode of the pump beam is involved in the stimulated scattering process.     

Cross-phase-modulation-induced instability and efficient parametric frequency conversion of ultrashort light pulses

We experimentally demonstrate efficient controlled parametric frequency conversion of femtosecond laser pulses through cross-phase-modulation-induced instability in the presence of a copropagating pump field in a fused silica photonic-crystal fiber. The amplitudes and the frequency shifts of sidebands generated in the spectrum of the probe field at the output of the fiber as a result of parametric four-wave mixing are controlled by varying the intensity of the pump field.     

线极化Bell-Bloom测磁系统中抽运光对磁场灵敏度的影响

利用适用于线极化Bell-Bloom测磁系统的布洛赫方程和含有自旋弛豫的速率方程,以铯原子为研究对象,分析了抽运光对磁场灵敏度的影响,并在实验上分别采用与铯原子D1线和D2线共振的线偏光作为抽运光和探测光,用充有缓冲气体的气室进行了实验.实验结果与理论分析一致,均表明只有在一定的光强范围内,增大抽运光光强可以提高磁场灵敏度.且利用这一方法分析了原子的自旋弛豫对磁场灵敏度的影响.这项研究对于深入认识线极化的Bell-Bloom测磁系统,以及如何通过优化系统实现磁场灵敏度的提高具有重要的意义.