Patent ID: 7843976

Claim:
A tunable multimode laser light source, comprising: an optical cavity formed between two reflectors, the optical cavity supporting a plurality of optical modes and having a cavity length; an optical gain medium positioned within the optical cavity; and a tuning section positioned in the optical cavity, the tuning section being coupled to receive light from the gain medium and tune between modes of the plurality of optical modes, the tuning section including a wavelength selection device a distance from the optical gain medium, the cavity length being held substantially constant when the wavelength selection device is scanned, the tuning section having a tunable filter function wherein the wavelength selection device has a filter function width that allows a plurality of longitudinal modes to simultaneously lase within the optical cavity, the simultaneous lasing forming a wavelength-tuned, multi-mode laser having a coherence length of greater than about 2 mm, and wherein the tuning section causes the average laser wavelength to change continuously with new longitudinal cavity modes entering from the leading edge of the tunable filter function as old longitudinal cavity modes fall off from the trailing edge of the tunable filter function.