MEMS-based Fourier transform spectrometer using pulsed infrared light source

Abstract

MEMS-based FTIR spectrometers are good candidates for handheld and IoT applications due to their high speed of operation, ultra-compact size and low cost. Light sources used for FTIR spectroscopy are usually limited to thermal light sources that continuously emit black body radiation. However, the use of pulsed sources has many advantages, such as reducing detector noise and enabling new kinds of spectroscopy measurements that depend on pulsed sources such as supercontinuum sources and non-linear infrared spectroscopy. The use of these pulsed sources with the high-speed MEMS is, thus, of great interest. In this work, we study the effect of using a pulsed IR source with a MEMS FTIR spectrometer on the obtained spectrum. The system is analyzed for different operation regimes from quasi-static to high-speed pulses for different duty cycles and repetition rates. Two measurement setups are used. The first involves using pulsed white light output from a thermal source with an optical chopper. The chopper frequency is changed from 20 Hz to 1 kHz at duty cycle values from 1% to 50%. The second setup uses an acousto-optic modulator to square-wave modulate the amplified spontaneous emission of a semiconductor optical amplifier with a repetition rate ranging from 20 Hz to 2 MHz and duty cycle values from 5% to 50%. Degradation in signal-to-noise ratio as well as spectral distortion are analyzed for different regimes of operation.