Alignment-insensitive method for wideband tuning of an unmodified semiconductor laser

摘要

Using simple optical components and an unmodified commercial off-the-shelf semiconductor laser, a frequency-selective self-aligning optical-feedback technique has been devised that allows a semiconductor laser to be tuned to and scanned about any optical frequency within the laser gain curve. This technique employs a graded-index rod lens cat's eye and an intracavity etalon for selecting one laser side mode. By changing the external cavity length, the laser frequency can be continuously tuned within one external cavity free spectral range. To further extend the tuning range, the laser injection current is changed to produce a discontinuous hop in the laser frequency. To eliminate the hops the cavity length and laser current are changed simultaneously.