Examinando por Autor "Ralston, John"

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Carrier capture and escape times in In0.35Ga0.65As-GaAs multiquantum-well lasers determined from high-frequency electrical impedance measurements
(IEEE, 1996-10) Esquivias, Ignacio; Weisser, Stephan; Romero, Beatriz; Ralston, John
We present experimental results on the high-frequency electrical impedance of In0.35Ga0.65As-GaAs multiquantum-well lasers with varied p-doping levels in the active region, The analysis of the data, using a simple three rate equation model, provides information about the dynamical time constants (the carrier lifetime, the effective carrier capture and escape times) under the laser operation conditions, The addition of p-doping increases the carrier escape time at threshold from 0.7 ns, extracted for the undoped devices, up to a value higher than 2 ns for the p-doped lasers, The effective capture time is estimated to be between 2 and 5 ps.
Carrier Dynamics and microwave characteristics of GaAs-Based Quantum-Well Lasers
(IEEE Journal of quantum electronics, 1999-04) Esquivias, Ignacio; Weisser, Stephan; Romero, Beatriz; Ralston, John; Rosenzweig, Joseph
We investigate the effects of carrier capture and re-emission on the electrical impedance, equivalent circuit, and modulation response of quantum-well (QW) laser diodes. The electrical impedance is shown to be a sensitive function of the time constants associated with carrier capture/transport and carrier re-emission. We compare the theoretical results with measured values of the electrical impedance of high-speed InGaAs-GaAs multiple-quantum-well lasers fabricated using different epilayer structures with a common lateral structure. The experimental results agree well with the theoretical model, allowing us to extract the effective carrier escape time and the effective carrier lifetime in the QW's, and to estimate the effective carrier capture/transport time
Damping limited modulation bandwidths up to 40 GHz in undoped short-cavity InGaAs-GaAs multiple quantum well lasers
(IEEE, 1996) Weisser, stephan; Larkins, Eric; Czotscher, Konrad; Benz, W; Daleiden, J; Esquivias, Ignacio; Fleissner, J; Ralston, John; Romero, Beatriz; Sah, RE; Schönferlder, Alexander; Rosenzweig, Joseph
We demonstrate record direct modulation bandwidths from MBE-grown In0.5Ga0.65As-GaAs multiple-quantum-well lasers with undoped active regions and with the upper and lower cladding layers grown at different growth temperatures, Short-cavity ridge waveguide lasers achieve CW direct modulation bandwidths up to 40 GHz for 6 x 130 mu m(2) devices at a bias current of 155 mA, which is the damping limit for this structure, We further demonstrate large-signal digital modulation up to 20 Gb/s (limited by the measurement setup) and linewidth enhancement factors of 1.4 at the lasing wavelength at threshold of similar to 1.1 mu m for these devices.
Impedance characteristics of quantum well lasers
(IEEE, 1994) Weisser, Stephan; Esquivias, Ignacio; Tasker, PJ; Ralston, John; Romero, Beatriz; Rosenzweig, Joseph
We derive theoretical expressions for the impedance of quantum-well lasers below and above threshold based on a simple rate equation model, These electrical laser characteristics are shown to be dominated by purely electrical parameters related to carrier capture/transport and carrier re-emission, The results of on-wafer measurements of the impedance of high-speed In0.35Ga0.65As/GaAs multipie-quantum-well lasers are shown to be in good agreement with this simple model, allowing us to extract the effective carrier escape time and the effective carrier lifetime, and to estimate the effective carrier capture/transport time,