Continuous frequency tuning of an external cavity diode laser significantly beyond the free spectral range by sweeping the injection current.

Abstract

In this study, the focus is on continuously tuning an external cavity diode laser equipped with an antireflection-coated laser diode over a 14.8 GHz range, 4.5 times larger than the free spectral range, using only injection current sweeps. In contrast, the absence of antireflection coating led to a tuning range of only one-fifth of the free spectral range, accompanied by hysteresis on mode hops. Theoretical analysis of this observed hysteresis suggests that broad tuning can be achieved when the longitudinal modes of the solitary laser diode are eliminated through the antireflection coating.