Characterization of the optical properties of the buried contact of the JWST MIRI Si:As infrared blocked impurity band detectors

TL;DR

This paper investigates the optical properties of the buried contact in JWST MIRI Si:As detectors, analyzing how it influences fringing effects in mid-infrared spectra through measurements and modeling.

Contribution

It provides a detailed optical model linking the buried contact properties to fringing behavior, enhancing understanding of detector performance.

Findings

Fringing causes 10-30% spectral modulation in MIRI data.

The buried contact significantly affects fringing patterns.

Optical modeling explains the observed spectral modulations.

Abstract

The Mid-Infrared Instrument MIRI on-board the James Webb Space Telescope uses three Si:As impurity band conduction detector arrays. MIRI medium resolution spectroscopic measurements (R$\sim$3500-1500) in the 5~$\mu m$ to 28~$\mu m$ wavelength range show a 10-30\% modulation of the spectral baseline; coherent reflections of infrared light within the Si:As detector arrays result in fringing. We quantify the shape and impact of fringes on spectra of optical sources observed with MIRI during ground testing and develop an optical model to simulate the observed modulation. We use our optical model in conjunction with the MIRI spectroscopic data to show that the properties of the buried contact inside the MIRI Si:As detector have a significant effect on the fringing behavior.