Laser frequency fluctuations are one of the limiting factors for many laser-involved precision measurements such as interferometry. Laser frequency locks with the Pound-Drever-Hall (PDH) method use typically an optical cavity as a reference, which are very sensitive to environmental noises. In contrast, spectroscopy methods using atom or molecular transitions and phase modulation spectroscopy behave better in the long term. A wellsealed fiber-based Hydrogen Cyanide (HCN) gas cell that is very compact and light-weighted is chosen. And We investigate laser frequency stabilization using the absorption line of an HCN gas cell instead of a cavity to provide better frequency stability in the low-frequency regime. In our lab, a fiber-coupled HCN gas cell laser frequency lock was built and thermally stabilized to provide better long-term stability. It is designed to work with our heterodyne interferometer around 1550 nm wavelength. The HCN gas cell locking setup using phase modulation (PM) spectroscopy shows less than 0.5MHz frequency drift over 12 hours measurement and stability levels of 1 kHz/ √ Hz for frequencies above 0.2 Hz.
High-sensitivity accelerometers are key for many applications including ground-based gravitational wave (GW) detectors, in-situ or satellite gravimetry measurements, and inertial navigation systems. We will present our work on the development of optomechanical accelerometers based on the micro-fabrication of mechanical resonators and their integration with laser interferometers to read out their test mass dynamics under the presence of external accelerations. We will discuss the latest developments on compact millimeter-scale resonators made of fused silica and silicon, optimized for frequencies below 1 kHz and exhibiting low mechanical losses. While fused silica has demonstrated high mechanical quality factors at room temperature, silicon devices perform significantly better at very low temperatures, which is particularly relevant for future ground-based gravitational wave detectors where cryogenic environments will be used to improve the sensitivity of the observatories. We will report on our design, modeling, and fabrication process for the silicon-based resonators and present their characterization by means of highly compact fiber-based Fabry-Perot cavities.
Accelerometers are key sensors in many fields and applications such as precision metrology, gravimetry measurements, gravitational wave observatories, and navigation where position and attitude need to be determined accurately. A combination of six accelerometers provides all the necessary information to estimate position and orientation of a rigid body and thus serves as an inertial navigation system for autonomous navigation. Fusedsilica based mechanical resonators paired with laser interferometric read-outs enable compact high-accuracy accelerometers. In this talk, we will present a wide-band accelerometer based on a double resonator with two test masses of different sizes in a single frame. One of the resonators has a resonance frequency of about 50 Hz, while the other is optimized for lower frequencies and has a nominal frequency of about 10 Hz. The combination of the two resonators allows for excellent long-term precision while maintaining good measurement bandwidth. We will show the experimental characterization in air and in vacuum of the double-resonator using a heterodyne laser interferometer and a fiber interferometer and its expected performance as an inertial sensor.
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