Simone Sassolini

Absolute efficiency measurement of high-performance zone plates

An absolute efficiency measurement technique for Fresnel zone plates using an electron impact micro-focus laboratory X-ray source (Lα line of Tungsten at 8.4 KeV) is demonstrated. A quasi-monochromatic x-ray image of a zone plate was obtained employing a pair of copper and cobalt filters. Applying this method to zone plates optimizes the zone plate fabrication process and provides the ability to explore zone geometry to achieve the best possible efficiency. Several zone plate parameters were tested with first order efficiency measuring from 1% to 29%.

Electrostatic microactuator for future hard disk drive

Hard disk drives are the most widely used data-storage medium. The TPI (track per inch) limit is related to mechanical resonances of the positioning arm and to low frequency bearing effects. A secondary actuator must be able to precisely position the R/W head, with high bandwidth, with respect to the magnetic track, without any interference with the magnetic data recorded on the disk. MEMS technology allows the fabrication of such electrostatic microactuators for the secondary stage in HDDs.

Optical characterization of micro-electro-mechanical structures

In this paper, semiconductor laser feedback interferometry is applied to the characterization of vibrating mass microsensors, such as gyroscopes and accelerometers. Complete characterization of such devices with this technique includes the identification of the vibration modes and the measurement of the resonance curves of the different axes, the determination of resonance frequency, quality factor and the actuation efficiency as functions of different parameters such as pressure. In the case of a gyroscope, tuning of the driving and of the sensing axes can be also performed, as well as the measurement of the Coriolis force. Thanks to its very simple optical implementation, feedback interferometry provides a viable alternative to the standard electrical measurements, and is especially useful for the characterization of prototypes, for which a dedicated electronics circuit is not yet available.

Batch fabricated silicon electrostatic micropositioner for dual stage actuation

Hard Disk Drives (HDD) are the most widely used data-storage medium. The Track Per Inch (TPI) limit is related to mechanical resonances of the positioning arm and to low frequency bearing effect. A secondary actuator must be able to position precisely with higher bandwidth the Read/Write (RW) head with respect to the magnetic track with any interference with the magnetic data recorded on the disk. MEMS technology allows the fabrication of such electrostatic microactuator for the secondary stage in the HDD. The paper presents the basics requirements for the secondary actuator for the HDD as well as the process developed to fulfill those. Accurate calculation and FEM simulation are required to lead to high performance and robust design. After the built a deep experimental analysis is ducted to confirm and refine design parameters.

Novel process for realization of multiple-axis actuators suitable for the realization of an optical switch

This paper illustrates a novel MEMS technology that allows the creation of a multiple axis actuator / sensor trough deep silicon etching and wafer bonding techniques. As example a dual axis rotational high-stroke MEMS actuator is presented. This device can integrate a mirror to realize a device used, for example, in fully optical multiplexer. Microfabrication technology derives from our previous works and it’s based on deep silicon trench techniques as well as on wafer bonding capabilities. More over the resulting assembly after the wafer bonding is machined to proceed on realizing the complete MEMS device.