Photonic electrometry using a piezoelectric-Pockels microresonator

TL;DR

This paper demonstrates high-resolution radiofrequency electrometry using a low-cost fixed-frequency laser and a lithium niobate microresonator, achieving comparable sensitivity to more complex systems and revealing bandwidth limitations and resonance-enhanced sensitivity.

Contribution

It introduces a method for photonic electrometry with low-cost lasers, utilizing the electrooptic effect in microresonators, reducing system complexity and cost.

Findings

Electrometry resolution maintained beyond optical resonance bandwidth.

Signal-to-noise ratio remains stable under varied coupling conditions.

Resonance-enhanced sensitivity improves resolution by a factor of 3 at 4 MHz.

Abstract

Facilitated by low-noise laser frequency locking, optical microresonators with the Pockels effect have shown unprecedented high resolutions in sensing electrical field. However, the requirement for tunable and low-noise laser sources considerably increases the cost and the size of the system, thereby limiting the industrial applicability of the microresonator-based technology. Here, we explore the possibility of using a low-cost fixed-frequency semiconductor laser as the pump laser to perform radiofrequency electrometry. A resonant mode in a lithium niobate microresonator is frequency-locked to the laser using the electrooptic effect. This same effect also underlies the radiofrequency electric-field sensing mechanism. Our experimental results show that the electrometry resolution can be maintained at signal frequencies beyond the optical resonance bandwidth and that the signal-to-noise ratio does not change with varied coupling conditions as long as the laser frequency noise is the dominant noise source of the system. In addition, narrowband electrooptic sensitivity enhancement is observed at frequencies of the microresonator's piezoelectric resonances, resulting in a resolution enhancement factor of approximately 3 at signal frequencies around 4 MHz. Our work advances the photonic resonant electrometry technology by studying the bandwidth limitation, and opens the road to the employment of low-cost lasers in high-resolution sensing applications.