Commercially available GaN-based laser diodes were antireflection coated in our laboratory and operated in an external cavity in a Littrow configuration. A total tuning range of typically 4 nm and an optical output power of up to 30 mW were observed after optimization of the external cavity. The linewidth was measured with a beterodyne technique, and 0.8 MHz at a sweep time of 50 ms was obtained. The mode-hop-free tuning range was more than 50 GHz. We demonstrated the performance of the laser by detecting the saturated absorption spectrum of atomic indium at 410 nm, allowing observation of well-resolved Lamb dips.
A continuous-wave distributed feedback diode laser emitting at 976 nm was frequency doubled by the use of a periodically poled lithium niobate waveguide crystal with a channel size of 3 microm x 5 microm and an interaction length of 10 mm. A laser to waveguide coupling efficiency of 75% could be achieved resulting in 304 mW of incident infrared light inside the waveguide. Blue laser light emission of 159 mW at 488 nm has been generated, which equals to a conversion efficiency of 52%. The resulting wall plug efficiency was 7.4%.
The authors demonstrate within a metrology experiment the applicability of a recently proposed temporally incoherent semiconductor laser source which relies on nonlinear dynamics. The realized spectrally broadband emission with an output power of 110mW and a coherence length of only 120μm is used in a rainbow refractometry experiment for sizing of liquid droplets, representing an important problem in industrial processes. The observed emission characteristics are attractive for implementation of modern imaging and metrology techniques which are based on the properties of well-directed, temporally incoherent light.
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