Development of a New, Precise Near-infrared Doppler Wavelength Reference: A Fiber Fabry-Perot Interferometer

TL;DR

This paper discusses the development of a fiber Fabry-Perot interferometer as a stable, precise, and economical Doppler wavelength reference for near-infrared spectrographs, demonstrating promising initial results.

Contribution

It introduces a new fiber Fabry-Perot interferometer designed for high stability and ease of integration as a Doppler reference in NIR spectrographs, with initial performance validation.

Findings

Achieved temperature control precision of 0.15 mK.

Theoretical velocity stability of 35 cm/s due to temperature control.

Successful first light results on SDSS-III APOGEE spectrograph.

Abstract

We present the ongoing development of a commercially available Micron Optics fiber-Fabry Perot Interferometer as a precise, stable, easy to use, and economic spectrograph reference with the goal of achieving <1 m/s long term stability. Fiber Fabry-Perot interferometers (FFP) create interference patterns by combining light traversing different delay paths. The interference creates a rich spectrum of narrow emission lines, ideal for use as a precise Doppler reference. This fully photonic reference could easily be installed in existing NIR spectrographs, turning high resolution fiber-fed spectrographs into precise Doppler velocimeters. First light results on the Sloan Digital Sky Survey III (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectrograph and several tests of major support instruments are also presented. These instruments include a SuperK Photonics fiber supercontinuum laser source and precise temperature controller. A high resolution spectrum obtained using the NIST 2-m Fourier transform spectrometer (FTS) is also presented. We find our current temperature control precision of the FFP to be 0.15 mK, corresponding to a theoretical velocity stability of 35 cm/s due to temperature variations of the interferometer cavity.