Fabrication of mid-IR lasers for gas analysis

We are working to improve current laser technology in the area of sensor applications. This comprises a number of advanced analysis techniques in which laser light is used to measure the properties of one or more chemical substances. Current focus it to m ake an improved laser for gas measurements and to extend the number of gases that can be detected with this technology. Key requirements for successfully developing a laserdevice for this includes: * Operation in most environments (-20 to +55C, 0% to 1 00% RH) * Low current usage (<200mA for laser) * Enough optical power (>5mW) * Narrow emission width (0.05nm) * Low optical noise (50 dB SNR or better) * Wavelength tuning (2nm) For the project to successfully realize such devices we utilize the latest in nanotechnology machinery. Materials are made using a Molecular Beam Epitaxy (MBE) machine that enables accurate adjustment of materials such as quantum wells. These are important for device efficiency (optical power, current usage). After the ma terials have been made, they are processed as large wafers. Each wafer can hold hundreds of lasers, and we will use a Substrate Conformal Imprint Lithography (SCIL) machine to "stamp" 160nm wide lines onto the wafer. This "stamp" impression is then us ed as a mask during material etching so that we get 160nm wide lines and 160nm wide openings in the surface of the wafer. After about 100 process steps including lithography, metallization, ion implant and annealing, the wafer is finished and can be cut i nto 0,5mm^2 large lasers. Finished lasers are tested so we can compare our results with simulated models to see if the device is as good as it should be. It enables improvement of model and process so that the next set of lasers are closer to the goal. Current status is that we have made wafers for 2.3um lasers using MBE and designed an imprint mask for the SCIL processing. The SCIL will be started 1Q´2014 at NTNU Nanolab.

The project is a collaboration between Integrated Optoelectronics (laser manufacturer) and Norsk Elektro Optikk (provider of optical gas analyser systems), and SINTEF (research institue). The project will establish new, mid-IR laser products (2300-3500nm wavelengths) based on the III-V materials system and integrate these in gas analysers. A significant end user advantage is projected (cost and ease of use) as compared to conventional gas chromatographs. Particular challenges that motivates a research a ctivity relate to (a) identification of optimum semiconductor material stacks, (b) wide tunability of the wavelength of the emitted light, and (c)high optical output powers. Reliable tunability requires extreme control of fine grating structures in the la ser surface. The project will make use of national laboratory infrastructures, in particular NORFAB (NTNU NanoLab).