Laser diode

摘要

A laser diode ( 1 ) for outputting light of a single mode comprises a substrate layer ( 5 ), a cladding layer ( 6 ) and a compound light propagating layer ( 7 ) comprising first, second, third and fourth layers ( 9 to 12 ). A wave guiding region ( 15 ) of refractive index lower than its adjacent regions is defined by the third layer ( 11 ) by two quantum wells ( 16 ) positioned at the anti-node of light of a single mode which is propagating in the third layer ( 11 ) for propagating and amplifying the single mode light. A central ridge ( 17 ) locates the wave guiding region transversely of the direction of light propagation. The wave guiding region ( 15 ) can also be defined by shaping the top cladding layer ( 6 ) by forming an elongated central channel through the central ridge ( 17 ).