Design, fabrication and characterization of infrared LVOFs for measuring gas composition
Journal article, 2014

This paper presents the design, fabrication and characterization of a linear-variable optical-filter (LVOF) that will be used in a micro-spectrometer operating in infrared (IR) for natural gas composition measurement. An LVOF is placed on top of an array of detectors and transforms the optical spectrum into a lateral intensity profile, which is recorded by the detectors. The IR LVOF was fabricated in an IC-compatible process using a photoresist reflow technique, followed by transfer etching of the photoresist into the optical resonator layer. The spectral range between 3 to 5 mu m contains the absorption peaks for hydrocarbons, carbon-monoxide and carbon-dioxide. The resulting optical absorption is utilized to measure the gas concentrations in a sample volume. Two LVOF structures were designed and fabricated on silicon wafers using alternate layers of sputtered silicon and silicon-dioxide as the high- and low- refractive index materials. These filters consist of a Fabry-Perot resonator combined with a band-pass filter designed to block out-of-band transmissions. Finally, the filters were fully characterized with an FTIR spectrometer and showed satisfactory agreement with the optical thin-film simulations. The characterization showed a spectral resolution of 100 nm, which can be further improved with signal processing algorithms. This method makes it possible to fabricate small and robust LVOFs with high resolving power in the IR spectral range directly on the detector array chip.

optical filter

IC-compatible

micro-spectrometer

infrared spectrum

hydrocarbon measurement

LVOF

Author

M. Ghaderi

Delft University of Technology

N.P. Ayerden

Delft University of Technology

A. Emadi

Delft University of Technology

Maxim Integrated

Peter Enoksson

Chalmers, Applied Physics, Electronics Material and Systems Laboratory

J. H. Correia

University of Minho

G. De Graaf

Delft University of Technology

R. F. Wolffenbuttel

Delft University of Technology

Journal of Micromechanics and Microengineering

0960-1317 (ISSN)

Vol. 24 8 Art. no. 084001-

Driving Forces

Sustainable development

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Transport

Energy

Subject Categories

Nano Technology

Infrastructure

Nanofabrication Laboratory

DOI

10.1088/0960-1317/24/8/084001

More information

Latest update

5/14/2018