It is expected that miniaturized infrared spectrometers will enable spectral sensing anywhere. Their applications are almost infinite, including in smart devices, monitoring of air and water quality, healthcare wearables, among many others. Free‐space on‐chip, or photonic MEMS, interferometers are an attractive solution since they provide the required miniaturization while achieving the optical throughput needed for device sensitivity. A Fourier‐transform spectrometer on‐chip is presented based on cascading silicon broadband photonic MEMS cavities. The double‐cavity configuration shrinks the size of the optical engine dramatically with respect to the Michelson configuration, while overcoming the need for bringing the micromirrors in physical contact as in case of a single cavity. The all‐silicon interfaces provide low enough reflectivity such that the response of the cavity can be approximated by a single harmonic allowing Fourier transform operation of the spectrometer. The spectrometer is fabricated using deep etching of a silicon‐on‐insulator substrate allowing release of movable elements. The optical engine size is 300 µm × 400 µm. The device is tested in the wavelength range of 1.1–2.1 µm and spectroscopy measurement of different materials with 7.5 nm spectral resolution is demonstrated and compared to a reference spectrometer.

Notch filters are used in spectroscopy, multi-photon microscopy, fluorescence instrumentation, optical sensors and other life science applications. One type of notch filter is based on a fiber-coupled Fabry–Pérot cavity, which is formed by a reflector (external mirror) facing a dielectric-coated end of an optical fiber. Tailoring this kind of optical filter for different applications is possible because the external mirror has fewer mechanical and optical constraints. In this paper we present optical modeling and implementation of a fiber-coupled Fabry–Pérot filter based on dielectric-coated optical fiber inserted into a micromachined fiber groove facing a metallized micromirror, which is driven by a high-speed MEMS actuator. The optical MEMS chip is fabricated using deep reactive ion etching (DRIE) technology on a silicon on insulator wafer, where the optical axis is parallel to the substrate (in-plane) and the optical/mechanical components are self-aligned by the photolithographic process. The DRIE etching depth is 150 μm, chosen to increase the micromirror optical throughput and improving the out-of-plane stiffness of the MEMS actuator. The MEMS actuator type is closing-gap, while its quality factor is almost doubled by slotting the fixed plate. A low-finesse Fabry–Pérot interferometer is formed by the metallized surface of the micromirror and a cleaved end of a standard single-mode fiber, for characterization of the MEMS actuator stroke and resonance frequency. The actuator achieves a travel distance of 800 nm at a resonance frequency of 89.9 kHz. The notch filter characteristics were measured using an optical spectrum analyzer, and the filter exhibits a free spectral range up to 100 nm and a notch rejection ratio up to 20 dB around a wavelength of 1300 nm. The presented device provides batch processing and low-cost production of the filter.

This work reports the design and opto-mechanical characterization of high velocity comb-drive actuators producing in-plane motion and fabricated using the technology of deep reactive ion etching (DRIE) of silicon-on-insulator (SOI) substrate. The actuators drive vertical mirrors acting on optical beams propagating in-plane with respect to the substrate. The actuator-mirror device is a fabrication on an SOI wafer with 80 μm etching depth, surface roughness of about 15 nm peak to valley and etching verticality that is better than 0.1 degree. The travel range of the actuators is extracted using an optical method based on optical cavity response and accounting for the diffraction effect. One design achieves a travel range of approximately 9.1 µm at a resonance frequency of approximately 26.1 kHz, while the second design achieves about 2 µm at 93.5 kHz. The two specific designs reported achieve peak velocities of about 1.48 and 1.18 m/s, respectively, which is the highest product of the travel range and frequency for an in-plane microelectromechanical system (MEMS) motion under atmospheric pressure, to the best of the authors’ knowledge. The first design possesses high spring linearity over its travel range with about 350 ppm change in the resonance frequency, while the second design achieves higher resonance frequency on the expense of linearity. The theoretical predications and the experimental results show good agreement.

No abstract

Optical phase modulators are essential building components in a wide range of applications, for instance, optical communication systems, tunable lasers, optical phase locked loops and optical sensors. The production of in-plane MEMSbased optical phase modulator with self-aligned mirrors, actuator and fiber grooves enables the low cost and easy integration with fiber-based lasers and sensors or photonic microsystems. In this work, we report an in-plane transmission type MEMS-based optical phase modulator fabricated by deep reactive ion etching (DRIE) technology on a Silicon-On-Insulator (SOI) substrate. Detailed optical analysis of the MEMS phase modulator taking into account the diffraction of the single-mode fiber output beam, the asymmetric truncation of the beam by the limited aperture of the micromirrors and the tilt angle of the deeply-etched mirrors is presented. The device layer height of the fabricated SOI wafer is 100 µm and the sidewalls are etched with verticality that is better than 89.98°. The micromechanical system is characterized experimentally using electrical technique and the resonance frequency and quality factor are 11.3 kHz and 163, respectively. The MEMS device is integrated into fiber ring laser (FRL) enabling the achievement of low and high frequency modulation indices. The frequency modulation of the FRL using the presented phase modulator is supported with numerical analysis and experimental results.Index Terms-DRIE, fiber-coupled MEMS, in-plane optical axis, MEMS optical phase modulator, multi-longitudinal mode ring laser, silicon photonics.