Study on the sensitivity of optical cavity length to light power fluctuation

Abstract

The length stability of optical cavities is vital in ultra-stable, cavity-stabilized laser systems. Using finite element analysis, we study the length deviation of optical cavities due to thermal expansion and thermo-refractive effects when the incident light power is changed. The simulated fractional length sensitivity of a 7.75-cm-long football cavity to the power fluctuation of incident light is 5 × 10 −14 ∕μW, which is in agreement with the experimental results found by measuring the frequency change of a cavity-stabilized laser when the incident light power is changed. Based on the simulation, the cavity sensitivity to light power fluctuation is found to depend on the cavity size and material.

Photo-birefringent effects of crystalline coatings in ultra-stable cavities

“…A regular change grows exponentially as the power increases, similar to that in dielectric coatings. 19 However, the difference in the optical path length in the fast axis increases and then decays exponentially with increased power. This respond to a dynamic frequency splitting between the incident light aligned with the slow and fast axes at 1397 nm changes with transmitted light power.…”

Investigation on the thermal property of a hydroxide catalysis bonded cryogenic cavity

“…We have also taken the 5 μm thick high reflective coating layer into consideration (not shown in the figures). Thermal expansion property of the coating layer depends on the composition of the dielectric layers SiO 2 and Ta 2 O 5 , and can be varied from the value of 5.8 × 10 −7 of Ta 2 O 5 to −2.5 × 10 −7 of SiO 2 [25,31], which makes the simulation much more complicated. We calculated the thermal property including the coating layer and notice that the CTE contribution of the coating layer can be compensated by the oxidation layer.…”

Thermal-noise-limited ultra-stable laser operated at 698 nm

“…Within the servo bandwidth, the frequency stability of the laser depends on the length of the optical cavity, which is highly susceptible to environmental noise such as ambient temperature fluctuations and mechanical vibration. With careful protection of the cavity and effective suppression of technologic noise [11][12][13], the performance of the stabilized laser will be limited by the thermal noise of the optical cavity [14].…”