DOI: 10.1088/0268-1242/22/9/014
WoS: 000249755900015
14 Citations
Résumé:

We address design and performance issues of a 975 nm range tilted cavity laser ( TCL) based on GaAs/GaAlAs waveguide and GaInAs quantum wells as an active medium. The all-epitaxial design of a TCL includes a cavity and a multilayer interference reflector (MIR). The cavity and the MIR are constructed as follows. The cavity confines one tilted optical mode, and the wavelength of this mode as a function of the tilt angle follows a first dispersion curve. The reflectivity spectrum of the MIR for tilted incidence of light has a well-pronounced stopband, and the stopband reflectivity maximum follows a second dispersion curve. The two dispersion curves intersect at one optimum tilt angle and one optimum wavelength lambda(0). At the wavelength lambda(0) the leakage loss of the optical mode through the MIR to the substrate has a minimum, which favors lasing at this optimum wavelength. The thermal shift of lambda(0) is governed by the shift of the intersection point. As the photon energy corresponding to the operation wavelength of the laser 975 nm is close to the resonance with the electronic energy gap in GaAs, the refractive index temperature coefficient dn/dT of GaA1As strongly increases at the GaAs side. This gives a tool to control the thermal shift of lambda(0) by replacing some layers of the cavity by a superlattice containing narrow insertions of GaAs. Such a superlattice may have the same averaged refractive index at room temperature, but significantly different values of dn/dT, thus affecting the thermal shift of lambda(0). Within this approach broad-area ( 100 mu m) devices have been fabricated showing a high temperature stability of the lasing wavelength ( 0.13 nm K-1), low threshold current density ( 300 A cm(-2)), a high power operation (> 7 W in pulsed mode and > 1.5 W in continuous wave mode), a high spectral stability at high output power, and a narrow vertical far-field beam divergence ( FWHM similar to 20 degrees).