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In semiconductor laser theory, the optical gain is produced in a semiconductor material. The choice of material depends on the desired wavelength and properties such as modulation speed. It may be a bulk semiconductor, but more often a quantum heterostructure. Pumping may be electrically or optically . All these structures can be described in a ...
[1] [2] For semiconductor lasers, the saturation effect is negligible. We derived the gain g for a Fabry-Perot semiconductor laser based on the density matrix equations and expressions for the natural linewidth. [1] [2] Thus, the linewidth theory [2] [8] [9] is an integral part of the nonlinear theory.
Optical gain is the most important requirement for the realization of a semiconductor laser because it describes the optical amplification in the semiconductor material. This optical gain is due to stimulated emission associated with light emission created by recombination of electrons and holes .
The laser diode rate equations model the electrical and optical performance of a laser diode. This system of ordinary differential equations relates the number or density of photons and charge carriers in the device to the injection current and to device and material parameters such as carrier lifetime, photon lifetime, and the optical gain.
The active laser medium (also called a gain medium or lasing medium) is the source of optical gain within a laser. The gain results from the stimulated emission of photons through electronic or molecular transitions to a lower energy state from a higher energy state previously populated by a pump source. Examples of active laser media include:
The appearance of in the denominator suggests that the required threshold gain would be decreased by lengthening the gain medium, but this is not generally the case. The dependence on l {\displaystyle l} is more complicated because α 0 {\displaystyle \alpha _{0}} generally increases with l {\displaystyle l} due to diffraction losses.