In this work, we present a novel architecture for Fourier transform spectrometers based on cascaded low-finesse FP interferometers. One of the interferometers has fixed path length while the second is a scanning one using a relatively large stroke electrostatic comb-drive actuator. The fixed interferometer results in a spectrum modulation and, hence, a shifted version of the interferogram away from the point of the zero spacing between the two mirrors. The shifted interferogram can then be used with the Fourier transform algorithm to obtain the spectrum of the measured light. This cascaded FP configuration results in a simple arrangement of mirrors on a line, which makes it much tolerant to misalignment errors. The proposed configuration is implemented using the MEMS DRIE technology on an SOI wafer with a simple MEMS process flow without metallization or dielectric coating of the vertical optical surface. The fabricated compact structure is measured with both a laser source with narrow spectrum at 1550 nm and a wide spectrum source composed of an SLED and the ASE of a semiconductor optical amplifier source. The obtained results validate the concept of the new configuration.
Fiber lasers are gaining wide attention nowadays due to their high stability, high reliability, low cost and compactness. Frequency modulation of the laser system has many applications such as wavelength tuning, active mode locking, generation of optical frequency combs and fiber sensors in general. In this work, we report frequency modulation of fiber ring laser system using transmission-type corner cube in-plane MEMS phase modulator fabricated by DRIE technology on an SOI substrate. The fiber-coupled MEMS-based phase modulator is inserted in a multilongitudinal mode fiber ring laser, which has a free spectral range of 345 kHz. By varying the applied voltage on the MEMS device, a wide range of the frequency modulation index can be achieved.
Notch filters based on fiber-coupled Fabry-Pérot cavity are formed by a reflector placed in close proximity to a
dielectric-coated end of an optical fiber. This kind of optical filters is easy to tailor for a given application because the
external mirror has less mechanical and optical constraints. In this paper we present a fiber-coupled Fabry-Pérot filter
based on dielectric-coated optical fiber inserted into a fiber groove facing a metallized micromirror, where the latter is
driven by a high-speed MEMS actuator. The microsystem is fabricated using Deep Reactive Ion Etching (DRIE)
technology on SOI wafer. The optical axis is in-plane and the components are self-aligned. The DRIE etching depth is
150 μm; chosen for improving the out-of-plane stiffness of the actuator and increasing the micromirror optical
throughput. The MEMS actuator type is closing-gap while its quality factor is improved by slotting the fixed plate. The
actuator, therefore, achieves a travel distance larger than 800 nm and has a resonance frequency of 90 kHz. The notch
filter exhibits a free spectral range up to 100 nm and a notch rejection ratio of 20 dB around a wavelength of 1300 nm.
The presented device provides low cost wafer level production of the filter.