Narrowband switchable dual-passband atomic filter with four-wave mixing optical amplification

By using Faraday optical filter combined with four-wave mixing (FWM) amplifier, a narrow bandwidth optical amplifying atomic filter with switchable dual-passband is demonstrated experimentally. The two transmission peaks of the filter correspond to the Stokes and anti-Stokes frequencies, exhibiting a Raman gain in 13- and 17-fold, respectively, with bandwidth of ～120 MHz. By properly setting pump laser detuning, switching between filter passbands is realized. We also investigate the dependence of peak transmission on both pump laser intensity and Rb cell temperature. This atomic filter can find practical applications in long-distance laser communications and laser remote-sensing systems.     

Raman amplification of ultrashort light pulses in inhomogeneously broadened three-level systems

In the limit of pulse durations that are shorter than the characteristic times of atomic decays, the dynamics of the propagation of a probe light pulse under the action of a driving pulse in the form of a self-induced transparency soliton applied to the adjacent transition of the V-scheme is considered. For a three-level absorber, it is shown that, in the absence of two-photon inhomogeneous broadening, the effect of soliton-induced transparency (SOIT) for the probe field takes place, which consists of the probe pulse undergoing forced localization by the driving pulse and propagates further without a change in the energy or shape. This type of transparency has no threshold with respect to both the energy and the area and is observed for arbitrarily weak pulses. The SOIT effect disappears in the presence of a two-photon inhomogeneous broad-ening. The effect of Raman amplification in a three-level amplifier with the Raman population inversion is considered. It is demonstrated that, under the action of the two-photon inhomogeneous broadening, the effect of Raman amplification becomes a threshold effect. The broader the two-photon inhomogeneous contour, the larger the Raman inversion required to initiate generation.     

Cascade parametric light amplification with low-frequency pumping

Cascade parametric amplification in a regular domain structure is examined theoretically taking the variations in phase of all the interacting waves in a dissipative medium into account. Analytic expressions are obtained for the conversion efficiency of the laser energy with low-frequency pumping. The dependence of the parametric amplification efficiency on the number of layers is given. Ways of increasing the frequency conversion efficiency are discussed. The presence of a nonzero input intensity at the sum frequency is found to cause a nonlinear increase in the high-frequency signal at the output of the structure. As the losses of the interacting waves increase, both the frequency conversion efficiency and the optimum domain length decrease.     

水下拉曼光谱探测低通滤光片水拉曼信号抑制

拉曼光谱作为研究物质结构的一个强有力工具,被广泛应用于水环境物质的检测,近年在深海原位探测中也得到应用.文章针对水下拉曼光谱探测的需要,设计了用于水的O-H振动拉曼信号抑制的低通滤光片,经过计算,边缘为指数形式的低通滤光片可较好的满足需要,而且通过实际采用的低通滤光片的实验证明,采用低通滤光片后水的O-H振动拉曼信号得...     

Efficient multi-frequency generation of ultrashort light pulses using stimulated Raman scattering and optical parametric amplification

Optical parametric amplification of multi-frequency seed pulses generated in a mixture of compressed hydrogen and methane by stimulated Raman scattering of 1 ps, 1 kHz laser pulses at 395.8 nm has been studied. Efficient generation of spectrally narrow ultrashort pulses with a spatial distribution close to the Gaussian profile of the pump beam was obtained in the visible and near infrared ranges.     

Phase control of light amplification in steady and transient processes in an inverted-Y atomic system with spontaneously generated coherence

We investigate the effects of spontaneously generated coherence （SGC） on both the steady and transient gain properties in a four-level inverted-Y-type atomic system in the presence of a weak probe, two strong coherent fields, and an incoherent pump. For the steady process, we find that the inversionless gain mainly origins from SGC. In particular, we can modulate the inversionless gain by changing the relative phase between the two fields. Moreover, the amplitude of the gain peak can be enhanced and the additional gain peak can appear by changing the detuning of the coupling field. As for the transient process, the transient gain properties can also be dramatically affected by the SGC. Compared to the case without SGC, the transient gain can be greatly enhanced with completely eliminated transient absorption by choosing the proper relative phase between the two fields. And the inverted-Y-type system with SGC can be simulated in both atomic and semiconductor quantum well systems avoiding the conditions of SGC.     

Raman spectroscopy of atomic fluorine

We have measured the Raman scattering cross section of atomic fluorine for transitions between the ground fine-structure electronic states. The fluorine was contained a in heated, static chamber. Gas temperature, determined from the rotational Raman spectrum of molecular fluorine, was used as an input to calculate the degree of fluorine dissociation (assuming thermodynamic and chemical equilibrium). The Raman frequency shift and depolarization ratio were also determined. Our results indicate that Raman scattering can be used as a probe for atomic fluorine.     

The probe gain with and without inversion in a four—level atomic model：light amplification at a short wavelength

We propose a new four-level atomic model for achieving light amplification at a short wavelength, where direct incoherent pumping into the top level is avoided by the advantage of coherent pumping. In this model, the lower level of the probe transition is an excited state but not the usual ground state. By analytical as well as numerical calculations, we find that the probe gain, either with or without population inversion, which depends on the relation between spontaneous decay rates $\g_{42}$ and $\g_{21}$, can be achieved with proper parameters. We note that the Raman scattering gain always plays an important role in achieving the probe amplification.     

Multimode stimulated Raman scattering with squeezed light

Stimulated Raman scattering of a multimode pump light on an one-mode phonon system is examined. The pump light is expected to be strong, so that it can be treated classically. The phonon mode and scattered Stokes and anti-Stokes modes are described quantally. The phonon is prepared in a coherent state and the scattered modes are prepared in displaced and squeezed states at the input.The author would like to thank Dr. J. Peina for fruitful discussions, and Dr. A. Luk for comments on the results.     

Sub-Doppler bandwidth atomic optical filter

We demonstrate what is to our knowledge the first atomic optical filter that uses velocity selection to achieve a passband width that is less than the Doppler width of the filtering transition. A narrow-linewidth pump laser is used to induce circular birefringence in a narrow velocity class of atoms in a dense potassium vapor for 694-nm light resonant with the 4P(3/2)-6S(1/2) transition. The filter displays a single 170-MHz passband at a peak transmittance of 9.5%. The bandwidth is an order of magnitude lower than that of previously demonstrated atomic optical filters.     

一种新型原子共振滤光器研究

报道Rb原子法拉弟共振滤光器(AFROF)的理论与实验研究.考虑Rb原子超精细结构的塞曼效应,对Rb-AFROF的传输特性进行理论分析,实验观测了Rb-AFROF的工作频率、通带宽度随外磁场和气室温度的变化关系.测量表明,Rb-AFROF传输效率～50%,带宽小于3GHz,最小探测光强～0.1μW.     

Inversionless amplification of light by a two-level medium as a result of mechanical-to-electromagnetic atomic energy conversion

Nonreciprocal effects in the acousto-optical interaction in gyrotropic cubic crystals with electroinduced anisotropy are studied. It is shown that the presence of optical gyrotropy leads to the doubling of the number of peaks of amplitude nonreciprocity, whereas an external electric field causes their shift and enhancement. It is found that the direction of lasing in a ring laser can be reversed by changing the direction of the control field. The results obtained can be used for the development and optimization of polarization-and electro-controlled acousto-optical nonreciprocal elements on the basis of cubic gyrotropic crystals.     

拉曼放大辅助波长可选择的全光开关

使用3-dB耦合器组成M-Z干涉仪,在M-Z干涉仪的一臂加入高非线性光纤(HNLF)组成的反向拉曼放大器,改变放大器的泵浦波长及强度,可实现波长可选择的全光开关。其功能可用于波分复用(WDM)系统,对不同波长的上、下载选择有很大的应用意义。理论分析了实现这一功能的可行性和参数选择,考虑拉曼放大并伴有交叉相位调制(XPM)引起信号光的相移,推导分析了在引入放大的同时又引入相移,怎样选择放大和相位匹配问题,来实现波长可选择的光开关的要求。     

Small-core As-Se fiber for Raman amplification

We have demonstrated Raman small-core As-Se fiber. More than 20-dB of gain was observed in a 1.1-m length of fiber pumped by a nanosecond pulse of approximately 10.8-W peak power at 1.50 microm. The peak of the Raman gain occurred at a shift of approximately 240 cm(-1). The Raman gain coefficient is estimated to be approximately 2.3 x 10(-11) m/W, which is more than 300 times greater than that of silica. The large Raman gain coefficient coupled with the large IR transparency window of these fibers shows promise for development of As-Se Raman fiber lasers and amplifiers in the near-, mid-, and long-IR spectral regions.     

Semiconductor laser with extended cavity and intracavity atomic filter

We report on peculiar dynamic features of laser oscillation in a cavity with a semiconductor junction as the gain medium and an intracavity atomic absorber. The output face of the semiconductor is antireflection coated, and lasing action is achieved by using a diffraction grating to close the laser cavity. The spectral analysis of the laser emission evidences a stable emission with narrow linewidth when the oscillating frequency is resonant with the atomic absorber. We also observe frequency bistability and instability. The change between these regimes is controlled through the bias current in a very reproducible way.     

Multiple atomic wave interferometry with standing-waves of light

Fringe shapes in a multiple-beam de Broglie-wave interferometer based on the atomic Kapitza-Dirac effect are studied. An all-optical implementation of such a device is proposed. A realization in the time-domain, using Bose-Einstein condensates released from a trap, seems viable within the present state of the art. Received 5 April 2000 and Received in final form 14 July 2000     

Radiative atomic recombination of antiprotons with light nuclei

The explicit, analytical expression of the photorecombination cross section of negative particles with nuclei has been deduced in terms of non-confluent, hypergeometrical functions of complex variable. The initial population of antiprotons, after atomic recombination with hydrogen, deuterium and tritium, has been calculated.     

Thermally controlled light filter

Journal of Applied Spectroscopy -     

Inversionless light amplification in sodium

Light amplification without population inversion in sodium vapor is reported. The result of this work is the amplification of a weak probe beam at a wavelength of 589.0 nm when the atoms are driven coherently by a long pulse at 589.6 nm, and the amplification of a weak probe beam at 589.6 nm when the atoms are driven coherently at 589.0 nm. The population contributions in the upper and lower lasing levels are calculated through the absorption spectra.