Single and Multiple Longitudinal Wavelength Generation in Green Diode Lasers

Single and multiple wavelength laser systems are presented that employ self-injection locked InGaN/GaN green laser diodes in an external cavity configuration with a partially reflective mirror. A stable and simultaneous locking of up to four longitudinal Fabry-Perot modes of the system cavity is demonstrated with appreciable signal-to-noise-ratio of ~13 dB and average mode linewidth of ~150 pm. The multi-wavelength spectrum exhibited a flat-top emission with nearly equal power distribution among the modes and an analogous mode spacing of ~0.5 nm. This first demonstration of multi-wavelength generation source is highly attractive in a multitude of cross-disciplinary field applications besides asserting the prospects of narrow wavelength spaced multiplexed visible light communication. Moreover, an extended two-stage self-injection locked near single wavelength visible laser system is also presented. An ultra-narrow linewidth of ~34 pm is realized at 525.05 nm locked wavelength from this innovative system, with ~20 dB side-mode-suppression-ratio; thus signifying a paradigm shift toward semiconductor lasers for near single lasing wavelength generation, which is presently dominated by other kinds of laser technologies.