CONTINUOUSLY TUNED EXTERNAL-CAVITY SEMICONDUCTOR-LASER

Continuous tuning (no mode hops) of a grating-tuned external-cavity semiconductor laser by rotation of the grating about a carefully selected point is analyzed and demonstrated using a laser containing a prism beam expander. The analysis predicts the continuous tuning range as a function of pivot-point position and is used to select the point for maximum continuous tuning range. Because dispersive optical elements in the cavity were found to limit the continuous tuning range, the model was modified to include dispersion to first order. The dispersion correction improved the maximum observed tuning range of the 1300 nm wavelength laser from 600 GHz to nearly 3000 GHz. Details of the cavity and mechanical design as well as pivot-point tolerances are also included.