Tandem coupled cavity lasers with separate current control and high parasitic resistance between them for bistability and negative resistance characteristics and use thereof for optical disc readout

摘要

A two-segment contact buried heterostructure (BH) laser is pumped by a current applied to its absorber contact from a source of high impedance on the order of 100K&OHgr; or more. The parasitic resistance between the absorber contact and the gain contact is high on the order of 10K&OHgr;. For a given absorber (bias) current the laser exhibits a relatively wide hysteresis on the order of 1 mA or more in the light vs. gain contact current. Such a laser is highly useful as a bistable optical element. The laser is also bistable with selected pump gain and absorber currents to exhibit a wide hysteresis of voltage across the absorber contact vs. relative amounts of light which is reflected back to the laser as feedback. The laser serve both as a light source and as a detector for reading out binary information stored as light reflective spots on a medium, e.g. a video disk.