A process to fabricate porous silicon Bragg reflectors patterned on a micrometer lateral scale over wafer areas of several square centimeters is described. This process is based on a new type of projection system involving a megavolt accelerator and a quadrupole lens system to project a uniform distribution of MeV ions over a wafer surface, which is coated with a multilevel mask. In conjunction with electrochemical anodisation, this enables the rapid production of high-density arrays of a variety of optical and photonic components in silicon such as waveguides and optical microcavities for applications in high-definition reflective displays and optical communications.
Visible light emission from the porous silicon (PSi) formed by anodic etching of Si in HF solution has raised great interest in view of possible applications of Si based devices in optoelectronics. In particular, multilayers consisting of periodic repetition of two PSi layers whose refractive indices are different can be exploited to design interference filters for controlling the emission wavelength as well as for the spectral narrowing of the wide emission band of Psi. FabryPerot optical microcavities with an active layer of λ/2 or λ sandwiched between two Bragg reflectors, consisting of alternating layers of high and low refractive indices are fabricated on heavily doped p-type silicon. We have investigated the optical properties of these microstructures using reflectivity and photoluminescence measurements at various temperature.
An electrically switchable computer-generated hologram (CGH) was fabricated using a liquid crystal (LC) cell. A polymethylmethacrylate (PMMA) film, which was spin-coated on one glass substrate of the LC cell, was patterned by a focused 2 MeV proton beam with a CGH phase pattern (2 microm resolution). With an applied voltage on the LC cell CGH sample, an index modulation was produced between the regions with and without PMMA because of the reorientation of LC molecules under the external electric field. The maximum diffraction efficiency measured was about 28.7%. The operating voltage was below 15 V(rms).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.