Application of Spectral Density of Transitions in Semiconductor Laser Theory
In this paper the formulas for spectral speed of an emission, for gain, for spectral - volume energy density of spontaneous radiation, for modulation of spontaneous radiation output power spectrum near to a threshold, based on formula for spectral density of transitions, are derived. The contrast modulation index mk was defined; using of mk determines more split-hair accuracy of definition |thetas| from experimental data.
Nonlinear laser theory and natural linewidth in semiconductor lasers
Our approach to the problem is based on the following basic concepts: using a spatially-distributed laser model; using an approximate Kovalevski-Noppe (KN) expression for effective natural linewidth for semiconductor lasers with application of generalized parameters. Physical representations of secondary spontaneous fluctuations have been formulated. These allow deriving formulas for generalized parameters in the KN expression for linewidth, on the basis of which the gain, foundation of the nonlinear system of equations, is derived. The effective natural linewidth is calculated after solving the nonlinear system of equations. Thus, the theory of natural linewidth is an integral part of the nonlinear theory on the basis of which the output power, linewidth, and threshold current for Fabry-Perot semiconductor lasers are calculated. The calculations made allow explaining some experimental measurements of natural linewidth for the Fabry-Perot semiconductor lasers.
Third order nonlinear distortion of SAW duplexers in UMTS system
Nonlinearity distortion characterization and accurate modeling techniques for leaky surface acoustic wave (LSAW) devices have been desired in the recently years due to the applications of the Radio Frequency (RF) SAW duplexers in the third-generation (3G) telecommunication system, such as Universal Mobile Telecommunications System (UMTS). In the work, we first discuss the approaches to measure and characterize the 3rd order harmonic generation of the resonators on lithium tantalate YXl42° wafer and YXl48° wafer, with resonance frequency of 800MHz to 900 MHz; Second, we present an effective nonlinear Butterworth-van-Dyke (BVD) model to simulate the multi-tone 3rd order intermodulation effects of a band 5 duplexer; simulation result vs. measurement of 3rd order harmonic generation, 3rd order intermodulation (IMD3) and triple beat are presented.