The effect of controlled optical feedback has been investigated for InAs/InP laser structures operating in the 1.55
μm fiber window. Mode locked lasers in particular show extremely small phase noise when subjected to optical
feedback, implying a very low timing jitter which is of interest for many applications.
We present an extension of an early work on external optical feedback in semiconductor lasers. A more general
formalism has been developed, which takes into consideration the anisotropy properties of an external cavity. The
expressions are derived for description of the feedback phenomena in a system composed of a laser diode and a Fabry-Perot cavity which is optically birefringent. We show that the emission behavior of such a system can be strongly
affected by the polarization states of the feedback waves, and that therefore multiple solutions become possible for
stabilization of a composite mode. Particular attention is paid to the angle-dependent phase condition. Examples are
given for a laser emitting at the wavelength of 1.54 μm and for an external cavity made of a quartz crystal.
We show that the spontaneous-emission behavior of an emitter-embedded periodic photonic band-gap (PBG) stack, described in general on the basis of the approximation of dipole emission, can be considerably modified if the macroscopic features of the emitter are considered. We have developed a model which takes into account the optical thickness of the emitter in the usual formalism. The extended model is presented in comparison with the classical dipole-emission model. Some numerical results are given and discussed, by using GaAs-embedded SiO2 / TiO2-coated quarter-wave stacks as a specific configuration. Our model provides quantitative arguments for optimization of spontaneous-emission power in terms of radiation frequency and emitter localization. It can be directly applied to optimum design of more complex systems, such as multi-emitter-embedded periodic stacks and any other passive structure.
In this paper, we present the feasibility of a wavelength Bragg reflector based on a set of liquid crystal plates. The tunability of the structure, using the fast variations of birefringence of the plates, is demonstrated and simulated. The tailoring of the transmittance by changing the orientation of the plates between them is also discussed and simulated.
We show that cascading two finite one-dimensional periodic photonic band-gap structures may result, due to the multiple confinement of the electromagnetic field, in a significant modification of the modal distribution of the electromagnetic density of modes (DOM) around a band edge. As a result of the combination of the band-gap effects and the band-edge effects, the enhancement and the optimum localization of the DOM can be simultaneously obtained. The general approach is presented. The basic rules and the main steps for the design of such a structure are described. Some numerical results are given and discussed, by using alternating Ga0.7Al0.3As/AlAs layer quarter-wave and mixed quarter-wave/half-wave stacks. The principle of the present work, although described within the limits of linear and dispersionless materials, may be directly applied to nonlinear parametric processes.
We propose, based on our recent investigations of a novel type of optical birefringent filter (called intracavity birefringent filter), a wavelength selective configuration, which may be used for Dense WDM applications. We show that this structure, formed with a classical Lyot-Ohman filter inside a ring cavity, takes the advantages of two typical filters: Fabry-Perot filters and birefringent filters, and in consequence gives a quite good compromise among usual filters parameters such as the working range, the bandwidth and the crosstalk. The theoretical considerations have been summarized. The first experimental results by use of a tunable nematic liquid-crystal light modulator have been shown.
In this paper, we present the feasibility of wavelength filtering by a hybrid liquid crystal Solc/Fabry-Perot filter device. The influence of the structure opto-geometric defects, such as the variation of the thickness, on the spectral response of the filter have been reported. Frequency and temporal characteristics are presented and discussed.
In this paper, we report for the first time the feasibility of coding by coherence modulation in 2D optical correlator using a spatially and temporally incoherent light source. This technique allows to carry out simultaneously several correlation products. The reported results have been obtained with a broadband source, such as a white-light source.