High-energy (λ≲7300 Å) 300 K operation of single- and multiple-stripe quantum-well heterostructure laser diodes in an external grating cavity

A set of high performance single- and multiple-stripe Alx′Ga1−x′As -AlxGa1−xAs quantum-well heterostructure (QWH) laser diodes coupled to an external grating cavity is used to demonstrate the tuning properties of a semiconductor laser at short wavelength (λ≲7300 Å). A single-stripe laser diode (6-μm stripe width) with a single AlxGa1−xAs (x∼0.22) quantum well of size Lz≊400 Å is broadly tunable (7080≤λ≤7370 Å, Δℏω∼70 meV) and delivers a single dominant longitudinal mode of moderate output power (Pout∼50 mW at 200 mA, pulsed). In continuous (cw) operation (I=135 mA) a single-stripe laser has a 36-meV tuning range, 7168≤λ≤7322 Å. Phase-locked twenty- and forty-stripe diodes (3.5-μm stripe width) from the same QWH wafer are capable of single-longitudinal-mode output at higher power (peak Pout∼1.6 W at a 8.0-A, 200-ns pulse) although at slightly longer wavelength and reduced tuning range (7225≤λ≤7425 Å). Data are presented illustrating the wavelength dependence of the gain and power output as well as the partial homogeneous broadening and phase-locked nature of the QWH laser arrays. The difference in performance of the multiple-stripe diodes compared with the single-stripe structure can be attributed to the internal coupling of the optical field in neighboring stripes and the reduced threshold current density.