Operating Range of Aluminum - Gallium-Arsenide Quantum-Well Heterostructure Lasers: Tunability, Power Output, and High Energy Emission (Semiconductor, Optical, Diode)

Abstract

A quantum-well heterostructure (QWH) is the most capable form of semiconductor laser. The quantum-size effect (QSE), inherent in a QWH laser, improves the device performance compared to conventional double heterostructure lasers. One advantage provided by the QSE is the increased possibility for carrier bandfilling of the active region. Experimental results are presented in which the continuous (CW) emission wavelength of an Al(,x)Ga(,1-x)As-GaAs QWH laser diode is tuned over a 100-meV spectral range (with the aid of an external grating cavity). The single 90-(ANGSTROM) quantum well is an ideal active region to provide broadband (7800-8300 (ANGSTROM)) optical gain.

To extend the power output, a QWH laser with a multiple-stripe active region is also operated in the external grating cavity. The short wavelength, high performance diodes with a single 400-(ANGSTROM) Al(,x)Ga(,1-x)As (x (TURN) 0.22) quantum-well active region exhibit less tunability but a much greater power output than single stripe lasers fabricated on the same crystal. The trade-off between power output and tunability is discussed.

The spatial form (intensity) of the emission of a multiple-stripe laser is further enhanced because of the nature of a phased-array active region. The behavior of the complex electromagnetic modes or "supermodes" of a gain-guided laser is discussed and the observations of various supermode phenomena are described.

Finally, the single- and multiple-stripe short-wavelength QWH diode lasers are subjected (for "tuning") to hydrostatic pressure (p(, )< 12 kbar). The hydrostatic pressure shifts the (GAMMA)-, L-, and X-bands in a manner which simulates an increase in the Al composition of the crystal. As the pressure is increased, the carriers are redistributed out of the (GAMMA)-band into the X- and L-bands; the threshold current increases accordingly. The results of the pressure measurements suggest a short-wavelength CW limit for this structure of (lamda) (TURN) 6980 (ANGSTROM).