Free spectral range measurement of a fiberized Fabry–Perot etalon with sub-Hz accuracy

Dimitrios Mandridis,Ibrahim Ozdur,Peter J Delfyett,Marcus Bagnell

doi:10.1364/oe.18.011264

Abstract

In this work a narrow linewidth (1 kHz) laser source is used to measure the free spectral range of a fiberized Fabry-Perot etalon with sub-Hz accuracy (10(-8)). A previously demonstrated technique based on the Pound-Drever-Hall error signal is improved in accuracy by the use of a narrow linewidth laser swept in frequency via an acousto-optic modulator, or single sideband generation. The sub-Hz (10(-8)) accuracy attained enables the characterization of both the long-term drift and the polarization dependence of the free spectral range of the fiberized etalon.

Highlights

Fabry-Perot etalons are multi-interference optical resonators having a periodic in frequency amplitude and phase response
A previously demonstrated technique based on the Pound-Drever-Hall error signal is improved in accuracy by the use of a narrow linewidth laser swept in frequency via an acousto-optic modulator, or single sideband generation
The high accuracy attained by the combination of the modified PDH technique with the frequency swept narrow linewidth laser enables the characterization of Fabry-Perot etalons and resonators with free spectral range (FSR) of up to tens of gigahertz, where phase modulators are available

Summary

Introduction

Fabry-Perot etalons are multi-interference optical resonators having a periodic in frequency amplitude and phase response. It is advantageous to reference at least one optical tone to the etalon, or vice versa This is performed by generating an error signal and feeding it back to either alter the frequency of the optical tone, or the center frequency of the resonator. The performance of the modified PDH technique described in [13] is analyzed revealing the requirement of a narrow linewidth frequency swept laser. This is achieved by incorporating a 1 kHz linewidth laser swept in frequency using an acousto-optic modulator (AOM). The high accuracy achieved enables the experimental measurement of both the polarization dependence of the FSR and its long-term drift

The Pound-Drever-Hall technique for free spectral range measurement

Experimental setup

Free spectral range characterization of a fiberized etalon

Findings

Conclusion