Compact, portable, thermal-noise-limited optical cavity with low acceleration sensitivity

Abstract

We develop and demonstrate a compact (less than 6 mL) portable Fabry-Pérot optical reference cavity. A laser locked to the cavity is thermal noise limited at 2 × 10−14 fractional frequency stability. Broadband feedback control with an electro-optic modulator enables near thermal-noise-limited phase noise performance from 1 Hz to 10 kHz offset frequencies. The additional low vibration, temperature, and holding force sensitivity of our design makes it well suited for out-of-the-lab applications such as optically derived low noise microwave generation, compact and mobile optical atomic clocks, and environmental sensing through deployed fiber networks.

Photonic chip-based low-noise microwave oscillator

“…The lowest-noise optical references are lasers locked to vacuum-gap F-P cavities, where fractional frequency stability as low as 4 × 10 −17 has been demonstrated with 212-mm-long cryogenic cavity systems 10 . Instead, we use an integrable cavity design based on a compact, rigidly held cylindrical F-P optical reference cavity that supports fractional frequency stability at the 10 −14 level 8 . Ultralow expansion glass with 1 m radius of curvature and an ultralow expansion glass spacer compose the 6.3-mm-long cavity with finesse of approximately 900,000 (Q ≈ 5 billion) and overall volume of less than 9 cm 3 .…”

“…Typically, this is a laboratory fibre or solid-state laser that is frequency stabilized to a large evacuated Fabry–Pérot (F-P) cavity 10 , 13 . Instead, we introduce an optimal combination of low-noise chip-integrated semiconductor lasers 14 , 15 and a new F-P concept that can be miniaturized to less than 1 cm 3 and chip-integrated without the need for high-vacuum enclosure 8 , 16 – 18 . The frequency noise of two semiconductor lasers near 1,560 nm is reduced by 40 dB through self-injection locking (SIL) to high-Q (quality factor) Si 3 N 4 spiral resonators 6 , 7 .…”

“…In this work we address this challenge by leveraging advances in integrated photonics to demonstrate low-noise microwave generation via two-point optical frequency division 4 , 5 . Narrow-linewidth self-injection-locked integrated lasers 6 , 7 are stabilized to a miniature Fabry–Pérot cavity 8 , and the frequency gap between the lasers is divided with an efficient dark soliton frequency comb 9 . The stabilized output of the microcomb is photodetected to produce a microwave signal at 20 GHz with phase noise of −96 dBc Hz −1 at 100 Hz offset frequency that decreases to −135 dBc Hz −1 at 10 kHz offset—values that are unprecedented for an integrated photonic system.…”

Ultralow-Noise K-Band Soliton Microwave Oscillator Using Optical Frequency Division

“…53 With increasing the Q factor of the microring, the external EDFA may be eliminated altogether. 52 Moreover, the ULE cavity in our system could be replaced with recently demonstrated integrated devices, 54 which provides a promising option for compact ultralow-noise microwave oscillator generation.…”

Environmental Chamber Characterization of an Ice Detection Sensor for Aviation Using Graphene and PEDOT:PSS

“…In response, the development of ice detection systems has become a key area in aviation technology. Traditional systems, ranging from mechanical methods to thermal and optical methods, have provided foundational information but often face limitations in terms of response time, sensitivity, and applicability under diverse flight conditions [4,5].…”