Removal of single-atom optical bistability by quantum fluctuations

The dynamics of the quantum-statistical properties of the radiation of an atom in a cavity interacting with an external coherent field is investigated. A high level of quantum fluctuations of the field in the cavity is shown to destroy optical bistability in the multiatom case. Photon-number fluctuations and the spectral dispersion of the canonically conjugate quadratures of the field inside and outside a cavity are calculated. It is found that in contrast to the multiatom case quadrature squeezing and squeezing of the radiation intensity of a single atom are negligible inside and outside the cavity. Zh. éksp. Teor. Fiz. 115, 2001–2013 (June 1999)     

Coherent control of optical bistability in tunnel-coupled double quantum wells

We analyze optical bistability (OB) behavior based on intersubband transitions in an asymmetric coupled-quantum well (CQW) driven coherently by a probe laser field and a control laser field by means of a unidirectional ring cavity. We demonstrate that OB can be controlled by tuning the energy splitting between two tunnel-coupled electronic levels, the intensity of the control field, and the frequency detuning of the probe and control fields. The influence of the electronic cooperation parameter on the OB behavior is also discussed. This investigation may be used for optimizing and controlling the optical switching process in the CQW solid-state system, which is much more practical than that in atomic system because of its flexible design and the controllable interference strength.     

ZnSe／ZnS多量子阱激子光学双稳性

用MOCVD在CaF_2衬底上生长的ZnSe/ZnS多量子阱材料,在77K下用N_2激光泵浦染料获得的宽带光脉冲进行了非线性光学测量,首次观察到ZnSe/ZnS多量子阱的激子光学双稳性,据分析这是由激子的能带增宽效应引起的增强吸收光学双稳性.     

On the use of the mean-field theory in optical bistability

The validity of the mean-field approximation in the theory of optical bistability is discussed. We show that major deviations from its predictions may occur if the mirrorreflectivity is decreased below a value which is strongly dependent on the bistability parameter C, and if the absorption αL is larger than a value weakly dependent on C (αL?4).     

Phase-dependent optical bistability and multistability in a semiconductor quantum well system

We theoretically investigate the hybrid absorptive-dispersive optical bistability and multistability in a four-level inverted-Y quantum well system inside a unidirectional ring cavity. We find that the coupling field, the pumping field as well as the cycling field can affect the optical bistability and multistability dramatically, which can be used to manipulate efficiently the threshold intensity and the hysteresis loop. The effects of the relative phase and the electronic cooperation parameter on the OB and OM are also studied. Our study is much more practical than its atomic counterpart due to its flexible design and the wide adjustable parameters. Thus, it may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.     

Piezooptical optical bistability

A glass fiber piezooptical optical bistability device is reported.Basing on pho-toelastic and strain effects of single-mode fiber,we have realized piezooptical modulation andperformed experiments of optical bistability.     

光栅光学双稳态

本文报道了一种光栅光学双稳态装置.利用改变一对对称光栅间相对位移,实现了对透过光强的周期性调制.将这样的系统作为传输部分,分别用He-Ne激光和普通白光完成了光学双稳实验.实验结果与理论分析相符.     

Subband-level renormalization and absorptive optical bistability in semiconductor multiple quantum well structures

A microscopic theory of many-body effects in the lowest subbands of semiconductor multiple quantum well structures is presented. The renormalized subband levels are calculated for a broad temperature range and optical bistability due to induced absorption is predicted.     

Optical bistability and multistability via quantum interference in an Er-doped optical fiber

The optical bistability and multistability in an Er³⁺-doped ZrF₄-BaF₂-LaF₃-AlF₃-NaF optical fiber inside a ring cavity are investigated. The underlying mechanism shows some new characteristics that other schemes do not have. Thus, it may provide some new possibilities for technological applications in optoelectronics and quantum information science.     

Incoherent control of optical bistability in an InGaN/GaN quantum dot nanostructure

The manipulation of bistable curve in the infrared (IR) region has been investigated theoretically in a unidirectional ring cavity doped by a four-level InGaN/GaN quantum dot nanostructure. The four-level quantum dot nanostructure is designed numerically by using the Schrödinger and Poisson equations. By controlling the size of the quantum dot and external voltage, one can design a four-level quantum dot with appropriate energy levels which can be suitable for interaction with IR signals. It is realized that the incoherent pumping fields play an essential role in controlling the intensity threshold of optical bistability. Decoherence effects such as the dephasing rate and electron density of the quantum dot are also analyzed at the threshold of optical bistability. Our proposed model due to its important application in all-optical systems may be favorable for real experimental evolution in infrared regions.     

Transients in optical bistability

In this paper we report on both a theoretical model for the transients in optical bistability in a Fabry-Perot cavity and the corresponding experimental results. An analytical calculation permits to predict the shape of the transient curves and the order of magnitude of their time duration in the case of a slow sweep of the length of the cavity. The experiment, which uses the nonlinearity arising from a two-photon transition in rubidium, yields results in good agreement with the theoretical calculation.Work supported by the D.R.E.T.     

Controlling the optical bistability via quantum interference in a four-level N-type atomic system

We investigate the optical bistability (OB) and optical multi-stability (OM) in a four-level N-type atomic system. The effect of spontaneously generated coherence (SGC) on OB and OM is then discussed. It is found that SGC makes the medium phase dependent, so the optical bistability and multi-stability threshold can be controlled via relative phase between applied fields. We realize that the frequency detuning of probe and coupling fields with the corresponding atomic transition plays an important role in creation OB and OM. Moreover, the effect of laser coupling fields and an incoherent pumping field on reduction of OB and OM threshold is then discussed.     

Theory of Gaussian-beam optical bistability

We describe an analysis of transverse coupling effects in a plane parallel Fabry-Perot containing a medium exhibiting non-linear refraction. The method involves projection on to a set of ortho normal mode functions and numerical solution of the resulting coupled equations. We find evidence for hysteresis in the profile of the transmitted beam without accompanying power hysteresis, in first interference order.     

Low threshold optical bistability with optical pumping

By use of circularly polarized light we have exploited optical pumping within the Zeeman sublevels of the ground state to obtain optical bistability in sodium vapours with low threshold power (around 1 mW) and a wide tuning range (>12 GHz). Experimental results are presented for different conditions of operation and compared to computer calculations, that include propagation effects and inhomogeneous broadening, based on a three-level atomic model that accounts for optical pumping.CEILAP, Buenos Aires, Argentina     

The statistical mechanics of particles obeying discrete spatial quantum theory

The energy levels for a particle confined to a one dimensional potential well are calculated using discrete spatial QM. The partition function is constructed and approximations are made to evaluate it thus generating an expression for the energy, entropy and chemical potential of an ensemble of such particles. The concept of negative temperature is applied to the above system and applications to the early universe are also discussed.     

Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.     

Self-pulsing in two-cavity optical bistability

We discuss two serially coupled ring cavities which contain media modelled by an ensemble of homogeneously broadened two-state atoms. This system produces pulsed outputs for appropriate CW inputs and values of the cooperativity parameters in the absorptive regime. In particular, self-pulsing occurs when both stable and unstable steady-state output versus input characteristics are everywhere monotomic with positive slope. An analytic requirement for this self-pulsing is obtained in the absorptive case.