Résultat de la recherche
Optical MEMS based on silicon-on-insulator (SOI) for monolithic microoptics
Microelectromechanical systems (MEMS) combined with optical components add optical functionality to devices and lead to the terms optical MEMS or MOEMS. The underlying technology of the presented devices is silicon-on-insulator (SOI) based batch fabrication, which delivers small, reliable and lasting monolithic bulk silicon structures for commercial devices with the advantage of being very insensitive to temperature changes. The particular strength of the technology is monolithic horizontal and vertical micromirrors for a variety of applications.
Microlens systems for fluorescence detection in chemical microsystems
Micro-optical systems based on refractive microlenses are investigated. These systems are integrated on a chemical chip. They focus an excitation beam into the detection volume (microliter or even submicroliter scale) and collect the emitted light from fluorescent molecules. The fluorescence must be carefully separated by spatial and spectral filtering from the excitation. This paper presents the ray tracing simulation, fabrication, and measurement of three illumination systems. The measurements show that an adroit placement and combination of microfabricated lenses and stops can increase the separation between the excitation light and the fluorescence light. Moreover we present the successful detection of a 20 nM Cy5TM (Amersham Life Science Ltd.) solution in a 100-µm-wide and 50-µm-deep microchannel (excitation volume ≈ 250 pL) using one of these illumination systems. The microchemical chip with the micro-optical system has a thickness of less than 2 mm.
Applications of SOI-based optical MEMS
After microelectromechanical systems (MEMS) devices have been well established, components of higher complexity are now developed. Particularly, the combination with optical components has been very successful and have led to optical MEMS. The technology of choice for us is the silicon-on-insulator (SOI) technology, which has also been successfully used by other groups. The applications presented here give an overview over what is possible with this technology. In particular, we demonstrate four completely different devices: (a) a 2 × 2 optical cross connector (OXC)with an insertion loss of about 0.4 dB at a switching time of 500 μs and its extension to a 4 × 4 OXC, (b) a variable optical attenuators (VOA), which has an attenuation range of more than 50 dB (c) a Fourier transform spectrometer (FTS) with a spectral resolution of 6 nm in the visible, and (d) an accelerometer with optical readout that achieves a linear dynamic range of 40 dB over ±6 g. Except for the FTS, all the applications utilized optical fibers, which are held and self-aligned within the MEMS component by U-grooves and small leaf springs. All devices show high reliability and a very low power consumption.
Fabrication of multilayer systems combining microfluidic and microoptical elements for fluorescence detection
This paper presents the fabrication of a microchemical chip for the detection of fluorescence species in microfluidics. The microfluidic network is wet-etched in a Borofloat 33 (Pyrex) glass wafer and sealed by means of a second wafer. Unlike other similar chemical systems, the detection system is realized with the help of microfabrication techniques and directly deposited on both sides of the microchemical chip. The detection system is composed of the combination of refractive microlens arrays and chromium aperture arrays. The microfluidic channels are 60 μm wide and 25 μm deep. The utilization of elliptical microlens arrays to reduce aberration effects and the integration of an intermediate (between the two bonded wafers) aluminum aperture array are also presented. The elliptical microlenses have a major axis of 400 μm and a minor axis of 350 μm. The circular microlens diameters range from 280 to 300 μm. The apertures deposited on the outer chip surfaces are etched in a 3000-Å-thick chromium layer, whereas the intermediate aperture layer is etched in a 1000-Å-thick aluminum layer. The overall thickness of this microchemical system is less than 1.6 mm. The wet-etching process and new bonding procedures are discussed. Moreover, we present the successful detection of a 10-nM Cy5 solution with a signal-to-noise ratio (SNR) of 21 dB by means of this system.
Performance of an Integrated Microoptical System for Fluorescence Detection in Microfluidic Systems
This article presents a new integrated microfluidic/microoptic device designed for basic biochemical analysis. The microfluidic network is wet-etched in a Borofloat 33 (Pyrex) glass wafer and sealed by means of a second wafer. Unlike other similar microfluidic systems, elements of the detection system are realized with the help of microfabrication techniques and directly deposited on both sides of the microchemical chip. The detection system is composed of the combination of refractive circular or elliptical microlens arrays and chromium aperture arrays. The microfluidic channels are 60 μm wide and 25 μm deep. The elliptical microlenses have a major axis of 400 μm and a minor axis of 350 μm. The circular microlens diameters range from 280 μm to 350 μm. The apertures deposited on the outer chip surfaces are etched in a 3000-Å-thick chromium layer. The overall thickness of this microchemical system is <1.6 mm. A limit of detection of 3.3 nM for a Cy5 solution in phosphate buffer (pH 7.4) was demonstrated. The cross-talk signal measured between two adjacent microchannels with 1 mm pitch was <1:5600, meaning that ≤1.8 × 10-4% of the fluorescence light power emitted from one microchannel filled with a 50 μM Cy5 solution reaches the photodetector at the adjacent microchannel. This performance compares very well with that obtainable in microchemical chips using confocal fluorescence systems, taking differences in parameters, such as excitation power into microchannels, data acquisition rates, and signal filtering into account.
Pulsed fiber laser using micro-electro-mechanical mirrors
Two different types of micromirrors are integrated with a fiber laser to modulate the cavity Q-factor. Both systems operate at frequencies up to 60 kHz and generate a pulse peak power 100 times higher than the continuous emission. We simulate the emitted pulses and find a good agreement with the measured value for the period of relaxation oscillations. The simulations also show the necessity of a shorter rise time of the Q-factor modulation to achieve one single giant and narrow Q-switched pulse.