G.J. Veldhuis

Nanosieves with microsystem technology for microfiltration applications

A nanosieve with a very uniform pore size of 260 nm and a pore-to-pore spacing of 510 nm has been fabricated using multiple exposure interference lithography and (silicon) micromachining technology. The nanosieve filter consists of a thick silicon nitride membrane perforated with submicron diameter pores and a macroperforated inorganic silicon support. The calculated clean water flux is at least one to two orders higher than that of conventional inorganic membranes.

Microsieves made with laser interference lithography for micro-filtration applications

A microsieve with a very uniform pore size of 260 nm and a pore to pore spacing of 510 nm has been fabricated using multiple exposure interference lithography and (silicon) micro-machining technology. The sieve consists of a 0.1 µm thick silicon nitride membrane perforated with sub-micron diameter pores and a macro perforated silicon support. The calculated clean water flux is at least one to two orders higher than that of conventional inorganic membranes.

Fabrication and packaging of integrated chemo-optical sensors

This paper describes the design and fabrication of a sensitive integrated chemo-optical sensor supplied with on-chip fiber-to-waveguide connectors. The sensor is designed for TE-polarized light with wavelength of 633 nm. The fiber-to-chip connectors are based on easily fabricated silicon V-grooves combined with a smooth sawcut. The sawcut is defining the channel waveguide endface. The sensor is based on a phase modulated Mach-Zehnder interferometer, using the electro-optic effect of the waveguiding material zinc oxide (ZnO). The fiber-to-chip connector units have a typical coupling efficiency of 0.1?1%. The electro-optical voltage × length product V? is 15 ± 4 V cm at frequencies above 100 Hz. Preliminary experiments on the general (passive) sensor response showing its expected high sensitivity are discussed.

Micromachining of high-contrast optical waveguides in [111] silicon wafers

A fabrication technique by KOH etching for very thin free standing plane parallel silicon bridges in a [111] silicon wafer is presented. The applications of such a stress free slab as an evanescent optical waveguide sensor of unusually high sensitivity are discussed.

Design and characterization of a mode-splitting /spl Psi/-junction

It will he shown In this paper, that the mode conversion factor (MCF) as defined for Y-junctions, can be profitably applied for the design of three branch junctions for splitting the three lowest-order modes of a channel waveguide. Accordingly, these so-called mode-splitting /spl Psi/-junctions were designed for implementation in PECVD SiON-technology. Propagation calculations point to crosstalk levels well below -20 dB at 10-20 mm junction length. The produced /spl Psi/-junctions show crosstalk of less than -17 dB, mainly originating from the nonhomogeneity of the refractive indexes of the SiON layers.

Electrostatically actuated mechanooptical waveguide ON-OFF switch showing high extinction at a low actuation-voltage

This paper reports on an integrated mechanooptical waveguide ON-OFF switch, where an absorbing element is moved into and out of the evanescent field of the guided mode in order to achieve switching. For the electrostatically driven devices, an extinction ratio of 65 dB at an actuation voltage of 2.5 V has been achieved in a 9.5-mm-long device for a wavelength of 632.8 nm. The calculated mechanical fundamental resonance frequency is 1.95 kHz. The device design enables future vacuum sealing that will annihilate the squeeze damping which, in the present device, reduces the response time to 10 s. Full-wafer scale fabrication is enabled by using standard silicon technology, chemical mechanical polishing and aligned wafer bonding. The devices can he used for channel selection purposes in integrated optical sensor arrays.

Evanescent wave sensor of sensitivity larger than a free space wave

A ray optic description of evanescent wave sensing allows a homogeneous treatment of the sensitivity of free space and guided wave slab sensors. It is shown in particular that the sensitivity of evanescent wave sensors is generally smaller or much smaller than that of a free space wave traversing the probed medium except in the remarkable case of large contrast slab waveguides propagating a restricted number of TM modes where the sensitivity can exceed that of a free space wave.

Normalized analysis for the optimization of geometric wavelength dispersion in three-layer slab waveguides

Closed form analytical expressions and normalized charts rigorously provide the conditions for maximum geometric wavelength dispersion in three-layer slab waveguides. The resulting optimization procedure is illustrated by the design of a dispersive channel waveguide for use in a novel SiON-technology based integrated optical wavelength sensor.