Gas Detection using a MEMS-Based Swept Laser Source

Swept Laser Sources (SLS) provide wide wavelength tuning range and high tuning speed making them attractive sources for sensing, biomedical and industrial imaging applications [1], [2]. MEMS based swept lasers have recently gained more attention with their potential low cost, high tuning speeds, high output power and possibility of integration with other devices [3], [4]. The adaptation of MEMS based swept lasers in gas sensing would allow the detection of multiple gases at high speed and sensitivity with a single device which is a major benefit over many of the available commercial devices. In this work, we present practical sensing of carbon dioxide gas using a MEMS based swept laser. The SLS under study, as shown in figure 1(a), it consists of a ring fiber cavity of length 20 m, a semiconductor optical amplifier (SOA) as a gain medium, an isolator to allow a unidirectional laser operation, a fiber polarization controller, an intracavity in-plane MEMS optical tunable filter and a tapping fiber-coupler to couple some power out of the loop. The MEMS filter, as shown in figure 1 (b), is a Fabry-Perot filter, based on deeply etched 80μm height silicon/air Bragg mirrors [4]. One of the mirrors is movable using an electrostatic comb-drive actuator. By applying a voltage across the comb-drive, an attractive force is developed which pulls the movable mirror towards the fixed one, thus the resonant wavelength of the filter is tuned, and the lasing wavelength as well.