Department of Physics, Engineering Physics & Astronomy

Department of Physics, Engineering Physics & Astronomy
Department of Physics, Engineering Physics & Astronomy

Development of Single-Mode Infrared Laser Diodes for Trace Gas Sensing

Dr. James Gupta

Date: Thursday, March 20, 2008
Time: 10:30 AM
Location: Stirling 501


A growing awareness of the environmental implications of industrial activities has led to an urgent need for extensive process and emissions monitoring. In many industries, this involves the detection of potentially lethal trace gases which are byproducts of a standard process, or harbingers of an unforeseen catastrophe. Fortunately, many of these gases have strong absorption features at infrared wavelengths. This allows the gas concentrations to be monitored in-situ using the technique of tunable diode laser absorption spectroscopy (TDLAS), in which the gas species of interest is detected by modulating the emission wavelength of a single-mode laser through a suitable absorption line. In this presentation, we will describe several approaches for single-mode laser diode manufacturing being developed at IMS-NRC using III-V semiconductors grown by molecular beam epitaxy. These include small-oxide aperture vertical cavity surface emitting lasers (VCSELs), as well as large-area photonic-crystal VCSELs in which the mode selection is provided by a patterned array. Single-mode edge-emitting lasers have also been demonstrated using a novel distributed-feedback grating process which is independent of the constituent materials. This has enabled the development of mid-infrared lasers near 2.4-2.6um, which is particularly important for industrial gases such as HF, H2S and CH4.