Multilayer porous silicon diffraction gratings operating in the infrared

Meifang Lai,Shanti Bhattacharya,Giacinta Parish,Adrian Keating,Gayathri M Sridharan

doi:10.1186/1556-276x-7-645

Abstract

Transmission diffraction gratings operating at 1,565 nm based on multilayer porous silicon films are modeled, fabricated, and tested. Features down to 2 μm have been patterned into submicron-thick mesoporous films using standard photolithographic and dry etching techniques. After patterning of the top porous film, a second anodization can be performed, allowing an under-layer of highly uniform porosity and thickness to be achieved. High transmission greater than 40% is measured, and modeling results suggest that a change in diffraction efficiency of 1 dB for a 1% change in normalized refractive index can be achieved. Preliminary measurement of solvent vapor shows a large signal change from the grating sensor in agreement with models.

Highlights

Diffraction gratings built from porous silicon (PS) have enormous potential to produce highly sensitive and rapid detection of analytes [1]
Planar gratings respond to changes in the near surface refractive index, requiring only shallow analyte infiltration compared with PS sensors made from microcavities and multilayer film stacks
Since the conductivity of the HF is significantly greater than the carrier depleted, high porosity P1 layer shown in Figure 3, the potential at the Si-electrolyte surface is unaffected by the P1 layer

Summary

Introduction

Diffraction gratings built from porous silicon (PS) have enormous potential to produce highly sensitive and rapid detection of analytes [1]. PS-based grating sensors have previously been made using pre-etched silicon [2], direct laser writing [3,4], imprinting [5,6], and holography [7]. Optical layers have been fabricated under the grating either as an uncontrolled result of the fabrication process [2,5] or by design [4,6]. Such layers could allow complex structures such as 2D photonic crystal structures to be created [6]; high-

Methods

Results

Conclusion