Sébastien Lani

Spectral phase, amplitude, and spatial modulation from ultraviolet to infrared with a reflective MEMS pulse shaper

We describe the performance of a reflective pulse-shaper based on a Micro-ElectroMechanical System (MEMS) linear mirror array. It represents a substantial upgrade of a preceding release [Opt. Lett. 35, 3102 (2010)] as it allows simultaneous piston and tilt mirror motion, allowing both phase- and binary amplitude-shaping with no wavelength restriction. Moreover, we show how the combination of in-axis and tilt movement can be used for active correction of spatial chirp.

Design, simulation, fabrication, packaging, and characterization of a MEMS-based mirror array for femtosecond pulse-shaping in phase and amplitude

We present an in-detail description of the design, simulation, fabrication, and packaging of a linear micromirror array specifically designed for temporal pulse shaping of ultrashort laser pulses. The innovative features of this device include a novel comb-drive actuator allowing both piston and tilt motion for phase- and amplitude-shaping, and an X-shaped laterally reinforced spring preventing lateral snap-in while providing high flexibility for both degrees of freedom.

High aspect ratio micromirror array with two degrees of freedom for femtosecond pulse shaping

We show the first results of a linear 100-micromirror array capable of modulating the phase and amplitude of the spectral components of femtosecond lasers. Using MEMS-based reflective systems has the advantage of utilizing coatings tailored to the laser wavelength range. The innovative features of our device include a novel rotational, vertical comb-drive actuator and an X-shaped, laterally reinforced spring that prevents lateral snap-in while providing flexibility in the two degrees of freedom of each mirror, namely piston and tilt. The packaging utilizes high-density fine-pitch wire-bonding for on-chip and chip-to-PCB connectivity. For the first deployment, UV-shaped pulses will be produced to coherently control the dynamics of biomolecules.

2D tilting MEMS micro mirror integrating a piezoresistive sensor position feedback

An integrated position sensor for a dual-axis electromagnetic tilting mirror is presented. This tilting mirror is composed of a silicon based mirror directly assembled on a silicon membrane supported by flexible beams. The position sensors are constituted by 4 Wheatstone bridges of piezoresistors which are fabricated by doping locally the flexible beams. A permanent magnet is attached to the membrane and the scanner is mounted above planar coils deposited on a ceramic substrate to achieve electromagnetic actuation. The performances of the piezoresistive sensors are evaluated by measuring the output signal of the piezoresistors as a function of the tilt of the mirror and the temperature. White light interferometry was performed for all measurement to measure the exact tilt angle. The minimum detectable angle with such sensors was 30µrad (around 13bits) in the range of the minimum resolution of the interferometer. The tilt reproducibility was 0.0186%, obtained by measuring the tilt after repeated actuations with a coil current of 50mA during 30 min and the stability over time was 0.05% in 1h without actuation. The maximum measured tilt angle was 6° (mechanical) limited by nonlinearity of the MEMS system.

A dual-axis high fill-factor micromirror array for high thermal loads

A high fill-factor, dual-axis micromirror array with novel spring and actuator design is developed for high thermal load applications. Each pixel can attain an omnidirectional mechanical DC rotation angle of ±4 degrees.

Fabrication and characterization of 3D integrated 2 DOF Micromirror Arrays for excessive thermal loads

This paper reports a high fill-factor (>90%), 2-dimensional analog micromirror array designed specifically for very high, optically induced thermal load applications. Each pixel can attain a mechanical DC rotation angle of ±4 degrees around any arbitrary axis with 170V excitation. The maximum temperature rise on the mirror surface with 7 KW/m2 thermal load under 1 Pa ambient pressure is below 230 °C. A detailed assessment of the fabrication process - including the poly-Si vertical electrodes, wafer level mirror bonding, and copper electroplating of structural layers-, and characterization methodology is presented with experimental results.

Large array of 2048 tilting micromirrors for astronomical spectroscopy: optical and cryogenic characterization

Multi-object spectroscopy (MOS) is a powerful tool for space and ground-based telescopes for the study of the formation and evolution of galaxies. This technique requires a programmable slit mask for astronomical object selection. We are engaged in a European development of micromirror arrays (MMA) for generating reflective slit masks in future MOS, called MIRA. MMA with 100 × 200 μm2 single-crystal silicon micromirrors were successfully designed, fabricated and tested. Arrays are composed of 2048 micromirrors (32 x 64) with a peak-to-valley deformation less than 10 nm, a tilt angle of 24° for an actuation voltage of 130 V. The micromirrors were actuated successfully before, during and after cryogenic cooling, down to 162K. The micromirror surface deformation was measured at cryo and is below 30 nm peak-to-valley. These performances demonstrate the ability of such MOEMS device to work as objects selector in future generation of MOS instruments both in ground-based and space telescopes. In order to fill large focal planes (mosaicing of several chips), we are currently developing large micromirror arrays integrated with their electronics.

Batman and Robin: next generation spectro-imagers for space observation

In Earth Observation, Universe Observation and Planet Exploration, scientific return of the instruments must be optimized in future space missions.

Microfabricated mirrors for space applications

We report on the advances towards the design and fabrication of a system consisting of two 10mm mirrors, one actuated magnetically and the other electrostatically. The system will be used for beam steering. The maximum resonant frequencies and deflection angle of each of the actuators will be reviewed and compared.

Linear MEMS micromirror array for UV-NIR femtosecond pulse shaping

We report our progress and the first optical application on the high-aspect ratio micromirror array for UV-NIR femtosecond (fs) broadband pulse shaping [1]. It is a bulk-micromachined device. capable of individually addressing 100 mirrors with a stroke of up to 3 μm using vertical comb drives in a novel. symmetrical double-spring design. The device was successfully implemented in a fs pulse shaper setup at λ0=795 nm.