Experimental Analysis of a Broadly Tunable Ingaasp Laser With Compositionally Varied Quantum Wells

Custom-designed InGaAsP lasers have been fabricated, tested, and show a broad spectral output at a bias current of 240 mA. The Fabry–Pérot ridge waveguide lasers were grown with one 80-$\hbox{\rm \AA}$ and five 100-$\hbox{\rm \AA}$ quantum wells in the active region. A different material composition was used for each well and this provided contributions to the gain profile over a broad wavelength range. A 1400-$\mu{\rm m}$ cavity length laser was found to operate in the spectral region from 1475 to 1650 nm and single-mode operation on the individual Fabry–Pérot modes of the uncoated laser was achieved over a 172-nm tuning range using a diffractive optical element short external cavity. The side-mode suppression ratio was measured to be above 30 dB at all wavelengths within the tuning range. Complete spectral coverage, in overlapping short segments, with the device is possible using temperature tuning.