Maier, F. J. (2016). Characterization of mid infrared photonic MEMS [Diploma Thesis, Technische Universität Wien]. reposiTUm. http://hdl.handle.net/20.500.12708/158533
For this thesis, different optical sensors have been characterized. The project was initiated by Infineon Austria and the sensor structures were designed by a team lead by Prof. Dr. Jakoby at the Johannes Kepler University Linz. We, at the Carinthian Tech Research (CTR), did the characterization of the structures and helped with some theoretical considerations. The sensor is designed to be able to detect different concentrations of CO2 in the ambient air by applying a Non- Dispersive InfraRed spectroscopy (NDIR) method. To reach a good sensitivity, even in low CO2 concentration environments, the sensor increases the path length of the light by guiding the light through waveguide structures. The sensor structures can be active (i.e. with an internal light source) or passive (with an external source) and can have an integrated bandpass filter. As the sensor is designed to work at a wavelength range of 3.9 - 4.3 µm, we also measured the absorption of chloroform, additionally to the absorption of CO2. To characterize the sensors experimentally, a test bench has been made. The test bench is able to characterize both passive and active devices. For the optical characterization of the different sensors, in contrast to free-beam designs, we employ InfraRed (IR) fibers as optical probes. The use of optical fibers facilitates position and angular-sensitive detection via an opto-mechanical design based on micrometric XYZ translation stages and a fixed pivot-point rotational positioning system. With this test bench we were able to characterize a grating coupler and also to prove the functionality of the passive sensors without bandpass filter by measuring the absorption of CO2 and chloroform. A concentration sensitive measurement has not been conducted at this stage of the project due to time constraints. It was not possible to measure the active devices and the sensors with bandpass filter with our test bench due to the low power output of the heater, which was further lowered by the various losses of the used incoupling method.