Control of a filter cavity with coherent control sidebands

Cavity-enhanced absorption sensing with robust sideband locking

We present a simple, continuous, cavity-enhanced optical absorption measurement technique based on high-bandwidth Pound-Drever-Hall (PDH) sideband locking. The technique provides a resonant amplitude quadrature readout that can be mapped onto the cavity's internal loss rate, and is naturally compatible with weak probe beams. With a proof-of-concept 5-cm-long Fabry-Perot cavity, we measure an absorption sensitivity of $6.6 \times 10^{-11} ~\text{cm}^{-1}/\sqrt{\text{Hz}}$ at 100 kHz (roughly the cavity bandwidth) and $\sim 10^{-10}~\text{cm}^{-1}/\sqrt{\text{Hz}}$ from 30 kHz to 1 MHz, with $38…

利用相干控制边带实现滤波腔长度控制的演示

Demonstration of length control for a filter cavity with coherent control sidebands

提出并实验验证了利用相干控制边带控制滤波腔长度的方法，成功将300米滤波腔的长度噪声从6.8 pm降至2.1 pm。

Optical vernier technique for in-situ measurement of the length of long Fabry-Perot cavities

We propose a method for in-situ measurement of the length of kilometer size Fabry-Perot cavities in laser gravitational wave detectors. The method is based on the vernier, which occurs naturally when the laser incident on the cavity has a sideband. By changing the length of the cavity over several wavelengths we obtain a set of carrier resonances alternating with sideband resonances. From the measurement of the separation between the carrier and a sideband resonance we determine the length of the cavity. We apply the technique to the measurement of the length of a Fabry-Perot cavity in the Cal…

Enhancing interferometer sensitivity without sacrificing bandwidth and stability: beyond single-mode and resolved-sideband approximation

Quantum noise limits the sensitivity of precision measurement devices, such as laser interferometer gravitational-wave observatories and axion detectors. In the shot-noise-limited regime, these resonant detectors are subject to a trade-off between the peak sensitivity and bandwidth. One approach to circumvent this limitation in gravitational-wave detectors is to embed an anomalous-dispersion optomechanical filter to broaden the bandwidth. The original filter cavity design, however, makes the entire system unstable. Recently, we proposed the coherent feedback between the arm cavity and the opto…

AM to PM conversion of linear filters

The conversion between amplitude modulation and phase modulation as a modulated signal goes thrugh a filter is analyzed. The difference in how the modulated sideband ampitude experience the filter, and how AM and PM has opposite signs for one of their sidebands interact. The conversion between AM and PM is modelled, providing a scatter model and evaluation of two functions based on the linear filters transfer function. The system bandwidth effects is analyzed and rule of thumb developed to ensure AM and PM isolation.

正交幅度调制用于电子边带Pound-Drever-Hall激光频率锁定

Quadrature amplitude modulation for electronic sideband Pound-Drever-Hall laser frequency locking

本文提出利用正交幅度调制技术生成高质量相位调制射频驱动信号，用于实现电子边带锁定，通过软件定义无线电补偿I/Q失真，验证了该方法在超窄线宽激光频率锁定中的连续调谐能力。