Mickaël Guillaumée

Polarization sensitive silicon photodiodes using nanostructured metallic grids

In this paper, we present the design, fabrication, and characterization of wire grid polarizers. These polarizers show high extinction ratios and high transmission with structure dimensions that are compatible with current complementary metal-oxide-semiconductor (CMOS) technology. To design these wire grids, we first analyze the transmission properties of single apertures. From the understanding of a single aperture, we apply a modal expansion method to model wire grids. The most promising grids are fabricated on both a glass substrate and CMOS photodiode. An extinction ratio higher than 200 is measured.

Observation of enhanced transmission for s-polarized light through a subwavelength slit

Enhanced optical transmission (EOT) through a single aperture is usually achieved by exciting surface plasmon polaritons with periodic grooves. Surface plasmon polaritons are only excited by p-polarized incident light, i.e. with the electric field perpendicular to the direction of the grooves. The present study experimentally investigates EOT for s-polarized light. A subwavelength slit surrounded on each side by periodic grooves has been fabricated in a gold film and covered by a thin dielectric layer. The excitation of s-polarized dielectric waveguide modes inside the dielectric film strongly increases the s-polarized transmission. A 25 fold increase is measured as compared to the case without the dielectric film. Transmission measurements are compared with a coupled mode method and show good qualitative agreement. Adding a waveguide can improve light transmission through subwavelength apertures, as both s and p-polarization can be efficiently transmitted.

Enhanced transmission from a single subwavelength slit aperture surrounded by grooves on a standard detector

An enhanced transmission is detected through a single slit of subwavelength width surrounded by grooves in a gold layer that is added as a postprocess to a standard complementary metal oxide semiconductor (CMOS) fabricated detector. The enhanced transmission results from constructive interference of surface waves, which interact with the incident light. The measured enhanced transmission shows strong qualitative agreement with that predicted by the modal expansion method. With the decreasing dimensions available in standard CMOS process, such nanostructures in metals could be used to replace current optical systems or to improve performance by increasing the signal to noise ratio and/or allowing polarization selection.

Inexpensive and fast wafer-scale fabrication of nanohole arrays in thin gold films for plasmonics

In this paper, a fast and inexpensive wafer-scale process for the fabrication of arrays of nanoscale holes in thin gold films for plasmonics is shown. The process combines nanosphere lithography using spin-coated polystyrene beads with a sputter-etching process. This allows the batch fabrication of several 1000 microm(2) large hole arrays in 200 nm thick gold films without the use of an adhesion layer for the gold film. The hole size and lattice period can be tuned independently with this method. This allows tuning of the optical properties of the hole arrays for the desired application. An example application, refractive index sensing, is demonstrated.

Description of the modes governing the optical transmission through metal gratings

An analytical model based on a modal expansion method is developed to investigate the optical transmission through metal gratings. This model gives analytical expressions for the transmission as well as for the dispersion relations of the modes responsible for high transmission. These expressions are accurate even for real metals used in the visible - near-infrared wavelength range, where surface plasmon polaritons (SPPs) are excited. The dispersion relations allow the nature of the modes to be assessed. We find that the transmission modes are hybrid between Fabry-Pérot like modes and SPPs. It is also shown that it is important to consider different refractive indices above and below the gratings in order to determine the nature of the hybrid modes. These findings are important as they clarify the nature of the modes responsible for high transmission. It can also be useful as a design tool for metal gratings for various applications.

Curved Holographic Combiner for Color Head Worn Display

A volume hologram recorded with a lens array is proposed as a color transflective screen for Head Worn Display (HWD) systems. Design, fabrication as well as proof of concept are reported. Light from a single MEMS-based projector is efficiently diffracted towards the eye with an angular spread given by the numerical aperture of the lenses forming the lens array. Using a dual-focus contact lens, full color high-resolution images are added to the HWD users normal vision. A full color system with a 55 degrees lateral field of view is demonstrated. This screen offers the possibility for small footprint and large field of view HWDs.

Scattering of light by a single layer of randomly packed dielectric microspheres giving color effects in transmission

Strong scattering properties are obtained for a monolayer of randomly packed polystyrene microspheres. This gives rise to structural colors in transmission. For a sphere diameter between 0.5 and 1 micron, light is mainly scattered in the forward direction. Consequently, in-plane multiple scattering can be neglected when spheres are not too close to each others. This allows one to use a single scattering approximation to reproduce transmission spectra of the system. The film color is dependent on the sphere size, but also on the observation angle. This angular dependant color is reproduced taking into account multiple scattering between spheres. These films can be useful when low reflection is needed.

Focused Ion Beam: A Versatile Technique for the Fabrication of Nano-Devices

Keywords: Annular Aperture Arrays ; Field Optical-Images ; Hole Arrays ; Transmission ; Deposition Reference EPFL-ARTICLE-164812View record in Web of Science Record created on 2011-04-11, modified on 2017-05-10

Nanostructured metallic surfaces for enhanced transmission and polarization filtering in CMOS fabricated photodetectors

The miniaturization of photodetectors often comes at the expense of a smaller photosensitive area. This can reduce the signal and thus limit the image quality. One way to overcome this limitation is to reduce the photosensitive area but with no reduction of signal i.e. harvest the light. Here we investigate, theoretically and experimentally, light harvesting with nanostructured metals. Nanostructured metals can also give additional functionality such as polarization filtering which is also investigated. After defining the figure of merits used when characterizing light harvesting and polarization filtering structures, we detail the fabrication and measurement process. Structures were made on glass substrate, as a post process step on CMOS fabricated detectors and directly in the CMOS fabrication of the detectors. The optical characterization results are presented and compared with theory. Finally, we discuss the challenges and advantages of integrating metallic nanostructures within the CMOS process.

Enhanced transmission of s-polarized light through a metal slit

Enhanced optical transmission (EOT) through subwavelength apertures is usually obtained for p-polarized light. The present study experimentally investigates EOT for s-polarized light. A subwavelength slit surrounded on each side by periodic grooves has been fabricated in a gold film and covered by a thin dielectric layer. The excitation of s-polarized dielectric waveguide modes inside the dielectric film strongly increases the s-polarized transmission. Transmission measurements are compared with a coupled mode model and show good qualitative agreement. Adding a waveguide can improve light transmission through subwavelength apertures, as both s and p-polarization can be efficiently transmitted.