Frequency stabilization via interference between transmitted and reflected lights from a reference cavity

We propose a modulation-free optical frequency stabilization technique using an interferometric effect between transmitted and reflected lights from a reference cavity. The property of the reflected light brings robustness of the error signal against laser intensity fluctuations as in previous stabilization methods. Due to the property of the transmitted light, the capture range for a specific locking frequency is expanded up to twice the FSR of the cavity, which we experimentally demonstrate. If locking to any resonant frequency is allowed, the capture range is infinite. From the effect of using both lights, our method achieves the highest sensitivity to the frequency fluctuations around the resonant frequency and provides robustness against the interferometer fluctuations.