Acceptance-Probability-Controlled Simulated Annealing - a Method for Modeling the Optical-Constants of Solids

A simulated annealing procedure with acceptance-probability control instead of the usual temperature control is proposed. The algorithm presented here has proved to be fully insensitive to initial parameters values, free of local-minima trapping problems, and shows superior convergence compared to adaptive-step classical simulated annealing with exponential cooling schedule. Experiments on computer generated synthetic data (with noise), closely resembling the optical constants of a metal, were performed to verify the effectiveness of the algorithm. The algorithm is then applied to parameter estimation of the model of optical constants of aluminum

Asymmetric Bragg mirror design for organic microcavity light emitting diodes

published_or_final_versio

Modeling the optical constants of AlxGa1-xAs alloys

Extension of Adachi's model with a Gaussian-like broadening function instead of a Lorentzian one is used to model the optical dielectric function of the alloy AlxGa1-xAs. Gaussian-like broadening is accomplished by replacing the damping constant in the Lorentzian line shape with a frequency dependent expression. In such a manner, the comparative simplicity of analytic formulae of the model is preserved, while the accuracy becomes comparable to more intricate models, and/or models with a significantly greater number of parameters. The employed model describes accurately the optical dielectric function in the spectral range from 1.5 to 6.0 eV in the entire alloy composition range. Relative rms error obtained for the refractive index is below 2.2% for all compositionspublished_or_final_versio

Correction to "Mode Selection and Tuning Mechanisms in Coupled-Cavity Terahertz Quantum Cascade Lasers"

In [1], the affiliation for Andrew Grier was incorrect. The correct affiliation where his contribution was made is as follows: A. T. Grier was with the School of Electronic and Electrical Engineering, University of Leeds, LS2 9JT Leeds, U.K. (e-mail: [email protected])

Correction to “Temperature-Dependent High-Speed Dynamics of Terahertz Quantum Cascade Lasers”

Corrections to author affiliation information is presented in the above named paper

Mode selection and tuning mechanisms in coupled-cavity terahertz quantum cascade lasers

We present a model for longitudinal mode competition in coupled-cavity (CC) terahertz (THz) quantum cascade lasers (QCLs) by using a scattering matrix method and multi-mode reduced rate equations (RREs). The dependence of the mode selection and tuning characteristics on various device parameters are systematically investigated, including the net waveguide loss, the optical length of the passive cavity, and the heat sink temperature for different relationship between the active and passive cavity lengths. The changes in eigenmode frequencies due to variations of device parameter are calculated before solving the RREs. The mode selection and tuning results obtained from solving the nonlinear RREs could be well explained by linear scattering matrix analysis. The mode tuning process simulated by the proposed model is compared with experimentally measured data, yielding good agreement. Comprehensive study of the influence of the key device parameters on the performance of CC THz QCLs provides potential design rules for single-mode operation with either wide frequency tunability or high stability

Sensing and Imaging using Laser Feedback Interferometry with Quantum Cascade Lasers

Quantum cascade lasers (QCLs) are high-power sources of coherent radiation in the midinfrared and terahertz (THz) bands. Laser feedback interferometry (LFI) is one of the simplest coherent techniques, for which the emission source can also play the role of a highly-sensitive detector. The combination of QCLs and LFI is particularly attractive for sensing applications, notably in the THz band where it provides a high-speed high-sensitivity detection mechanism which inherently suppresses unwanted background radiation. LFI with QCLs has been demonstrated for a wide range of applications, including the measurement of internal laser characteristics, trace gas detection, materials analysis, biomedical imaging, and near-field imaging. This article provides an overview of the QCLs and the LFI technique, and reviews the state of the art in LFI sensing using QCLs