Sb-Based Mid-Infrared Diode Lasers
- PDF / 438,501 Bytes
- 12 Pages / 612 x 792 pts (letter) Page_size
- 88 Downloads / 208 Views
Sb-Based Mid-Infrared Diode Lasers C. Mermelstein, M. Rattunde, J. Schmitz, S. Simanowski, R. Kiefer, M. Walther, and J. Wagner Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, D-79108 Freiburg, Germany ABSTRACT In this paper we review recent progress achieved in our development of type-I GaInAsSb/AlGaAsSb quantum-well (QW) lasers with emission wavelength in the 1.74-2.34 µm range. Triple-QW (3-QW) and single-QW (SQW) diode lasers having broadened waveguide design emitting around 2.26 µm have been studied in particular. Comparing the two designs we have find that the threshold current density at infinite cavity length as well as the transparency current density scale with the number of QWs. Maximum cw operating temperature exceeding 50°C and 90°C has been obtained for ridge waveguide lasers emitting above and below 2 µm, respectively. Ridge waveguide diode lasers emitting at 1.94 µm exhibited internal quantum efficiencies in excess of 77%, internal losses of 6 cm-1, and threshold current density at infinite cavity length as low as 121 A/cm2 reflecting the superior quality of our diode lasers, all values recorded at 280 K. A high characteristic temperature TO of 179 K for the threshold current along with a value of T1 = 433 K for the characteristic temperature of the external efficiency have been attained for the 240-280 K temperature interval. Room temperature cw output powers exceeding 1.7 W have been demonstrated for broad area single element devices with highreflection/antireflection coated mirror facets, mounted epi-side down. The latter result is a proof for the high power capabilities of these GaSb-based mid-ir diode lasers. INTRODUCTION Semiconductor diode lasers emitting at wavelengths around 2 µm and beyond are of significant current interest for an increasing number of applications, including tunable diode laser absorption spectroscopy (TDLAS) for process control and environmental monitoring, as well as materials processing such as welding of plastics and medical laser surgery. Many of the potential applications for mid-ir semiconductor lasers, in particular those involving molecular spectroscopy and remote sensing, require coherent sources with narrow linewidths. While the TDLAS related applications ask for high spectral purity and tunability of the diode laser, the two latter applications call for high output powers on the multiple watt level and concomitant high power conversion efficiency along with good beam quality. An additional key issue is the ambient or above ambient operating temperatures while maintaining high power efficiency. For the 2-3 µm wavelength interval, the conventional interband diode laser approach is adopted, employing GaInAsSb/AlGaAsSb type-I QW/barrier layers as active region grown on GaSb substrates [1, 2]. Diode lasers based on the (AlGaIn)(AsSb) material system covering the above given spectral range demonstrated excellent room temperature performances, including very low threshold current density, very low internal loss coefficient, and high internal quan
Data Loading...
