Differentially patterned pumped optical semiconductor gain media

Abstract

An optical gain medium comprising, for example, an optical semiconductor device which is differentially pumped and a master oscillator power amplifier (MOPA) device employing such an amplifier. The gain medium may have a linear stripe region or a diverging stripe region that allows the light propagating therein to diverge along at least part of its length, such as a flared or tapered amplifier having a gain region that increases in width toward its output at a rate that equals or exceeds the divergence of the light. The amplifier is pumped with a current density at its input end which is smaller than the current density used to pump the output end for maintaining coherence of the beam to high power levels employing differential pumping. Differential pumping may be both longitudinal and lateral within the amplifier and may be patterned to reduce the peak modal gain observed longitudinally along and/or laterally across the pumped stripe region of the gain medium so that he experienced modal gain of the propagating light is more balanced along the length of the stripe region, i.e., rendered significantly more uniform in distribution, providing for higher diffraction limited performance without optical filamentation formation.