Time domain numerical model for linear and nonlinear grating assisted co-directional coupler

A time domain algorithm for the dynamic analysis of linear and nonlinear devices based on coupled modes propagating with different group velocities is presented for the first time. As a test case, the numerical algorithm is applied to the analysis of a linear grating assisted co-directional coupler, in order to investigate quantitatively its limitations. As an application example, we show the simulation results on the switching dynamics of a current injection controlled grating assisted co-directional coupler sampled Bragg reflectors laser.     

Lasing spectra of 1.55 μm InAs/InP quantum dot lasers: theoretical analysis and comparison with the experiments

In this paper, a theoretical model is used to investigate the lasing spectrum properties of InAs/InP (113)B quantum dot (QD) lasers emitting at 1.55 μm. The numerical model used is based on a multi-population rate equation (MPRE) analysis. It takes into account the effect of the competition between the inhomogeneous broadening (due to the QD size dispersion) and the homogenous broadening as well as a nonlinear gain variation associated to a multimode laser emission. The double laser emission and the temperature dependence of lasing spectra of self-assembled InAs/InP quantum dot lasers is studied both experimentally and theoretically.     

Simulations of Differential Gain and Linewidth Enhancement Factor of Quantum Dot Semiconductor Lasers

We present a multi-population rate equation model for the analysis of the static and dynamic characteristics of a quantum dot (QD) semiconductor laser. The model is applied to the extraction of the differential gain and linewidth enhancement factor of the QD laser simulating the same kind of experiments usually done in the laboratory. Coherently with the experimental results, we show the difference between the values of the differential parameters extracted in below and above threshold characterizations. We demonstrate that such discrepancy is due the complex dynamics of the carriers in those energy states, whose carrier concentration is not clamped by the stimulated emission process above threshold.     

THE USE OF BENZOPHENONE AS A PHOTOAFFINITY LABEL, LABELING IN p-BENZOYLPHENYLACETYL CHYMOTRYPSIN AT UNIT EFFICIENCY

Abstract— p -Benzoylphenylacetyl chymotrypsin, an acyl enzyme derivative containing the benzophenone group in the hydrophobic binding pocket, was prepared and is indefinitely stable at low pH. Photolysis of this covalent derivative leads to loss of enzymic activity and incorporation of the labeling group via formation of a second covalent bond. The efficiency of the photochemical processes is exceptionally high, producing 100% incorporation and at least 92% inactivation. Analysis of active site titration data for the photolyzed enzyme show that at least two different photochemical processes must be involved. Elimination of phosphorescence emission and reduction of UV absorption upon photolysis are consistent with initial hydrogen abstraction by benzophenone triplet state, followed by radical coupling, much as has been observed for the photoreaction of benzophenone with model systems. Photoaffinity labeling of chymotrypsin is also efficiently accomplished using two benzophenone derivatives which bind noncovalently to the enzyme's active site, although the rates of labeling are somewhat less than in the covalent complex.     

Numerical analysis of the effects of carrier dynamics on the switch-on and gain-switching of quantum dot lasers

A systematic analysis of the influence of the capture, inter-level relaxation and exciton dephasing time constants on the dynamic behavior of quantum dot Fabry-Perot semiconductor lasers is done taking into account the lasing from the ground and excited states. The simulation results show that the carrier time constants studied influence significantly the static characteristic of the laser, its switch-on response and the pulses generated by gain-switching.