Abstract: An n-InP cladding layer, a GRIN-SCH-MQW active layer, a p-InP cladding layer, p-InGaAsP contact layer and a p-side electrode are laminated sequentially on an n-InP substrate. Moreover, a film having high reflectivity is laminated on a reflection side end surface, and a transmission film is laminated on an emission side end surface. The transmission film has a first film and a second film. The second film is composed of an equivalent film composed of three layers.

Abstract: An n-InP cladding layer, a GRIN-SCH-MQW active layer, a p-InP cladding layer, p-InGaAsP contact layer and a p-side electrode are laminated sequentially on an n-InP substrate. Moreover, a film having high reflectivity is laminated on a reflection side end surface, and a transmission film is laminated on an emission side end surface. The transmission film has a first film and a second film. The second film is composed of an equivalent film composed of three layers.

Abstract: Disclosed are semiconductor laser diodes and laser diode modules for reducing noise in EDFA and TDFA fiber amplifiers, to thereby increase signal bandwidth. A major source of noise is identified as being signal light that is inadvertently coupled from the fiber amplifier to the laser diode, and then returned back to the fiber amplifier as noise. In one aspect of the present invention, the back facet of the laser diode is constructed to achieve a reflectivity to the signal light of 40% or less. In another aspect, an anti-reflective coating is provide on the coupling fiber to the laser diode. A reduction of at least 17 dB in the returned signal is achieved by the present invention.