Patent ID: 6868101

Claim:
An apparatus said semiconductor laser is an active element in a tunable light source having an emission spectrum of substantially single 1 nes, said tunable light source comprising: at least one active optical element, a respective first reflective end for each said active optical element, a grating with a set of lines that are one of parallel and divergent, said divergent lines diverging frorm at least one of a true vertex and an effective vertex, said grating and said first reflective end of eac h said active optical element cooperating to form a respective laser resonant cavity that cortains each said active optical element, each said active optical element and its resonant cavity cooperating to produce a respective light output having an emission spectrum of substantially a single line, said rieans for effecting a grazing coupling between said grating aid each said laser resonant cavity and for controlling said grazing coupling to maintain substantially uniform reflection from each grating line back to each said active element, each said laser and said resonant cavity being at least one of a resonant cavity without an optical fiber and a resonant cavity having an optical fiber, and means for moving said grating along a path relative to each said laser resonant cavity to simultaneosly and in the same ratio alter both the periodicity of the effective intersections of said grating ines with each said resonant cavity and the effective cavity length of each said resonant cavity to produce a constant longitudinal mode throughout the entire tuning range of said tunable light source.