Observation of an Optical Spring With a Beamsplitter

TL;DR

This paper reports the first experimental observation of an optical spring generated solely by interference at a beamsplitter, demonstrating stability and tunability without optical cavities or external feedback.

Contribution

It introduces a novel cavity-free optical spring created by a beamsplitter, confirmed through experiments with a Michelson-Sagnac interferometer and a GaAs microresonator.

Findings

Optical spring frequency shifts with input power as predicted.

Optical spring stabilizes the interferometer without external feedback.

Experimental results match theoretical models.

Abstract

We present the experimental observation of an optical spring without the use of an optical cavity. The optical spring is produced by interference at a beamsplitter and, in principle, does not have the damping force associated with optical springs created in detuned cavities. The experiment consists of a Michelson-Sagnac interferometer (with no recycling cavities) with a partially reflective GaAs microresonator as the beamsplitter that produces the optical spring. Our experimental measurements at input powers of up to 360 mW show the shift of the optical spring frequency as a function of power and are in excellent agreement with theoretical predictions. In addition, we show that the optical spring is able to keep the interferometer stable and locked without the use of external feedback.