Thermal-noise-limited higher-order mode locking of a reference cavity

Abstract

Higher-order mode locking has been proposed to reduce the thermal noise limit of reference cavities. By locking a laser to the HG mode of a 10-cm long all ultra-low expansion (ULE) cavity and measuring its performance with the three-cornered-hat method among three independently stabilized lasers, we demonstrate a thermal-noise-limited performance of a fractional frequency instability of 4.9×10. The results match the theoretical models with higher-order optical modes. The achieved laser instability improves the all ULE short cavity results to a new low level.

Ultraviolet laser spectroscopy of aluminum atoms in hollow-cathode lamp

“…The wavemeter is calibrated by a 534 nm laser which is generated by frequency doubling of an ultra-stable laser at 1068 nm. The ultra-stable laser has a frequency instability of 5.0 × 10 −16 and a frequency drift rate of 20 mHz/s [31], and the frequency of the ultra-stable laser is measured by a frequency comb that is referenced to a Cs clock (Symmetricom 5071A). The calibration wavelength is chosen at 534 nm instead of 1068 nm so that the calibration wavelength is closer to the measurement wavelengths.…”

Mirror Coating Thermal Noise Mitigation Using Multi-Spatial Mode Cavity Readout

“…There are several experimental examples of order-two modes in use in cavity experiments [22,29]. A choice of even ordered modes is ideal as their symmetry makes them first order insensitive to angular error and pointing jitter.…”

“…The resulting error signals are combined with optimal weightings to extract a composite signal with ideal combination to sample the largest possible effective mirror area, thereby minimizing coating thermal noise. In contrast to other beam spreading strategies -such as top-hat MESA modes [16,20], edge stability cavities [21], or, single higher order modes [22][23][24][25] -this method allows for the use of conventional spherically polished mirrors with a greater robustness to manufacturing defects and alignment errors. This approach makes use of standard RF locking techniques but lends itself well to modern digital signal processing approaches where quantity of signals and flexible recombination may be easily scaled.…”

Vibration Property of a Cryogenic Optical Resonator within a Pulse-Tube Cryostat

“…We lock a 1064 nm continuous wave semiconductor laser to the cavity using the Pound–Drever–Hall (PDH) method [ 21 ]. We evaluate the laser frequency stability by beating the laser with another reference ultrastable laser locked to a room temperature cavity [ 22 , 23 , 24 ], as shown in Figure 3 a. The frequency stability of the reference laser is at 1 s averaging time.…”

“…A normal 6 cm sapphire cavity without a vibration-immune design was installed on the cryogenic plate of the cryostat. We locked a 1064 nm laser to the cavity using the Pound–Drever–Hall (PDH) method, and the laser frequency stability was evaluated by beating this laser with another ultrastable reference laser [ 21 , 22 , 23 , 24 ]. We obtained the vibrational sensitivity of the cryogenic cavity through different frequencies of vibrational modulation with three voice coil motors driving the cryostat in three perpendicular directions.…”