Optical Absorption Measurements on Crystalline Silicon at 1550nm

TL;DR

This paper reports optical absorption measurements of crystalline silicon at 1550nm, relevant for gravitational wave detectors, showing an absorption coefficient of approximately 264 ppm/cm at room temperature.

Contribution

It provides the first measurement of optical absorption in crystalline silicon at 1550nm using a photo-thermal self-phase modulation technique.

Findings

Absorption coefficient measured at (264 +/- 39) ppm/cm.

Measurement conducted at room temperature.

Sample was float-zone silicon with 11kOhm cm resistivity.

Abstract

Crystalline silicon is currently being discussed as test-mass material for future generations of gravitational wave detectors that will operate at cryogenic temperatures. We present optical absorption measurements on a large-dimension sample of crystalline silicon at a wavelength of 1550nm at room temperature. The absorption was measured in a monolithic cavity setup using the photo-thermal self-phase modulation technique. The result for the absorption coefficient of this float-zone sample with a specific resistivity of 11kOhm cm was measured to be \alpha_A=(264 +/- 39)ppm/cm.