Semiconductor optical gain

About: Semiconductor optical gain is a research topic. Over the lifetime, 5997 publications have been published within this topic receiving 96505 citations.

Practicality of compensating the loss in the plasmonic waveguides using semiconductor gain medium

Abstract: We consider the issue of compensating the loss in plasmonic waveguides with semiconductor gain material and show that, independent of specific geometry, full loss compensation in plasmonic waveguides with significantly sub-wavelength light confinement (less than λ/4n) requires current density well in excess of 100 kA/cm2. This high current density is attributed to the unavoidable shortening of recombination time caused by the Purcell effect inherent to sub-wavelength confinement. Consequently, an injection-pumped plasmonic laser that is truly sub-wavelength in all three dimensions (“spaser”) would have threshold current densities that are hard to obtain in any conceivable semiconductor device.

Sensitivity of quantum-dot semiconductor lasers to optical feedback.

Abstract: The sensitivity of quantum-dot semiconductor lasers to optical feedback is analyzed with a Lang-Kobayashi approach applied to a standard quantum-dot laser model. The carriers are injected into a quantum well and are captured by, or escape from, the quantum dots through either carrier-carrier or phonon-carrier interaction. Because of Pauli blocking, the capture rate into the dots depends on the carrier occupancy level in the dots. Here we show that different carrier capture dynamics lead to a strong modification of the damping of the relaxation oscillations. Regions of increased damping display reduced sensitivity to optical feedback even for a relatively large alpha factor.

Oscillation center frequency tuning, quantum FM noise, and direct frequency characteristics in external grating loaded semiconductor lasers

Abstract: Simple analytical expressions for the oscillation frequency, quantum FM noise spectrum, oscillation power spectrum, spectral linewidth, and direct optical frequency modulation efficiency in semiconductor lasers with external grating feedback are presented. Experimental results for the grating loaded AlGaAs lasers are in good agreement with the theoretical predictions. Remarkable reduction in spectral linewidth to less than 50 kHz is achieved by feeding back only 10-3of the output power. Oscillation frequency stabilization, frequency jump behavior, and reduction in direct optical frequency modulation efficiency are also discussed.

Optical gain and gain suppression of quantum-well lasers with valence band mixing

Abstract: The effects of valence band mixing on the nonlinear gains of quantum-well lasers are studied theoretically for the first time. The analysis is based on the multiband effective-mass theory and the density matrix formalism with intraband relaxation taken into account. The gain and the gain-suppression coefficient of a quantum-well laser are calculated from the complex optical susceptibility obtained by the density matrix formulation with the theoretical dipole moments obtained from the multiband effective-mass theory. The calculated gain spectrum shows that there are differences (both in peak amplitude and spectral shape) between this model with valence band mixing and the conventional parabolic band model. The shape of the gain spectrum calculated by the new model becomes more symmetric due to intraband relaxation together with nonparabolic energy dispersions. Optical intensity in the GaAs active region is estimated by solving rate equations for the stationary states with nonlinear gain suppression. >

Prevention of gain saturation by multi-layer quantum dot lasers

Abstract: The authors compare the threshold current density jt/sub h/ against the laser length of a single layer quantum dot (SLQD) laser with a sixfold multilayer quantum dot (MLQD) laser. Gain saturation is not observed in the MLQD laser. They calculate j/sub th/ against the number of dot layers including gain saturation. The strong impact of thermal coupling of carriers on j/sub th/ is demonstrated.