We investigate the evolution of short-duration pulses injected into laser diodes biased above threshold with the use of spectrally and temporally resolved experimental and numerical methods. We show that stable transients may be formed as a result of spatially re-distributing the cavity energy. By controlling the phase of injected pulses with respect to the diode cavity radiation we show through simulation that it is possible to directly generate and control stable streams of pulses.
We investigate generalized asymmetric left-handed (LH) slab waveguides that constitute an extension to the symmetric structure initially proposed by Pendry. By utilizing the asymmetry it has been shown that they have the potential for increased image resolution. This is due to the amplification of the formed surface waves (SWs) that is able to compensate material losses. Some preliminary studies in this direction have been reported in the literature but, to the best of our knowledge, there is no complete study of all possible SW eigenmodes supported by such LH waveguides. A rigorous theoretical investigation is presented herein that offers clear mathematical explanation and detailed physical insight into the formation of surface polaritons (SPs) in these heterostructures and provides the conditions for their existence. It is found that a rich variety of SP modes can exist (30 in total) that depend critically on the combination of the different refractive indices, constitutive parameters ε(ω) and µ(ω) the sample geometry. For each case we provide the geometric dispersion diagram and the profile of the corresponding stable field configuration from which the various characteristics of the mode (enhancement, phase reversal) are apparent. An interesting result of the above analysis is that, for certain choices of the material parameters, the coupling between the interfaces allows the existence of new 'supermodes' when no stable solutions exist at the isolated interfaces of the slab alone. Finally, the modes that give rise to negative group velocity are identified and key features of the dispersion diagrams are discussed, most of which are unique to the structures studied herein and have not been previously recovered with symmetrical studies.
The spatio-temporal dynamics of whispering gallery modes in microdisk lasers is studied by time-domain computer simulations based on full vectorial Maxwell-Bloch equations. In particular, we focus on the spatial interaction of the optical mode with the inversion density of the active material.
The electromagnetic field evolution described by the Maxwell curl equations are solved with a full three-dimensional finite-difference
in time-domain algorithm with uniaxial perfectly matching layer boundary conditions. The nonlinear active material is modelled via optical Bloch equations that are transformed to real value differential equations which can be computed efficiently and highly accurately.
Our computer simulations give insight into the internal interrelated
carrier-light-field dynamics of microdisk lasers and reveal fundamental aspects of the progression of degenerated modes in nonlinear active material through spatial hole burning.
Using full three-dimensional finite-difference time-domain (FDTD) simulations of Maxwells' equations we investigate the mode and photonic band structure and far-field pattern of distributed feedback resonators used in organic lasers. The distributed feedback structure under investigation consists of a two layered system. The first layer is a thick substrate that has a one or two dimensionally corrugated (nano-patterned) surface structure. The active material is a thin layer on top of the corrugated structure. The whole structure is assumed being surrounded by vacuum. Our FDTD calculations are carried out by applying mixed uniaxial perfectly matched layers (UPML) and periodic boundary conditions. This new technique allows us to investigate both guided and leaking modes of dielectric periodic systems. The far-field is obtained by a near-field to far-field transformation. The mode pattern is calculated by spatially resolved discrete temporal Fourier transformation of a particular frequency of interest. A similar computation reveals the frequencies that form the photonic band structure. Our computations show the characteristics of the DFB resonator and explain central aspects of the lasing process in these devices, such as the position and width of the band gap. These results are in good qualitative and quantitative agreement with experimental results.