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大功率激光二极管的波导结构(waveguide structures for High-power laser diodes)
1.The Large Optical Cavity (LOC) Concept
The vertical waveguide of a high-power LD consists of a core having a refractive index higher than that of cladding layers.In the core forming the active region, typically a strained quantum well is embedded. An optimized strucutre has to deal essentially with the following:
A. a high confinement factor to reduce the threhold current,
B. a large near-field width to reduce the facet load,
C. a small near-field width to reduce the overall thickness of the epitaxial layers as well as the thermal and series resistances,
D. a large near-field width to achieve a small vertical divergence,
E. low scattering losses,
F. low losses of free-carrier absorption,
G. high doping level to reduce the series resistance,
H. high barriers for the carriers to improve the electrical confinement and therefore the internal effiency and the thermal stability,
I. small barriers between the differenct layers to achieve a low voltage across the diode.
The so-called Large Optical Cavity with broadened waveguide layers allows a simple and good approximation of the near-field distribution to Gaussian one and results in improving LD performance.
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