Using active resonator impedance matching for shot-noise limited, cavity enhanced amplitude modulated laser absorption spectroscopy.
We introduce a closed-loop feedback technique to actively control the coupling condition of an optical cavity, by employing amplitude modulation of the interrogating laser. We show that active impedance matching of the cavity facilitates optimal shot-noise sensing performance in a cavity enhanced system, while its control error signal can be used for intra-cavity absorption or loss signal extraction. We present the first demonstration of this technique with a fiber ring cavity, and achieved shot-noise limited loss sensitivity. We also briefly discuss further use of impedance matching control as a tool for other applications.
Centre for Gravitational Physics, Faculty of Science, The Australian National University, Canberra, ACT 0200, Australia. jong.chow@anu.edu.au
Jong H
JH
Chow
Ian C M
IC
Littler
David S
DS
Rabeling
David E
DE
McClelland
Malcolm B
MB
Gray
D003198:Computer Simulation; D017076:Computer-Aided Design; D017097:Electric Impedance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D008962:Models, Theoretical; D013057:Spectrum Analysis / Q000295:instrumentation*; D014159:Transducers; D014732:Vibration