Photothermal and thermo-refractive effects in high reflectivity mirrors at room and cryogenic temperature

Abstract

Increasing requirements in the sensitivity of interferometric measurements is a common feature of several research fields, from gravitational wave detection to quantum optics. This motivates refined studies of high reflectivity mirrors and of noise sources that are tightly related to their structure. In this work we present an experimental characterization of photothermal and thermo-refractive effects in high reflectivity mirrors, i.e., of the variations in the position of their effective reflection plane due to weak residual power absorption. The measurements are performed by modulating the impinging power in the range 10 Hz $÷$ 100 kHz. The experimental results are compared with an expressly derived theoretical model in order to fully understand the phenomena and exploit them to extract useful effective thermo-mechanical parameters of the coating. The measurements are extended at cryogenic temperature, where most high sensitivity experiments are performed (or planned in future versions) and where characterizations of dielectric film coatings are still poor.

References in corpus (6)

• Thermo-optic noise in coated mirrors for high-precision optical measurements
• Thermoelastic dissipation in inhomogeneous media: loss measurements and displacement noise in coated test masses for interferometric gravitational wave detectors
• Observation of back-action cancellation in interferometric and weak force measurements
• Thermal noises and noise compensation in high-reflection multilayer coating
• Enhanced photothermal displacement spectroscopy for thin-film characterization using a Fabry-Perot resonator
• Measurements of the optical mirror coating properties

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• Long 48-cm ULE cavities in vertical and horizontal orientations for Sr optical clock
• Broadband Measurement of Coating Thermal Noise in Rigid Fabry-Perot Cavities
• Ultra-stable transportable ultraviolet clock laser using cancellation between photo-thermal and photo-birefringence noise
• Optical back-action on the photothermal relaxation rate
• Ultrastable lasers: investigations of crystalline mirrors and closed cycle cooling at 124 K
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• Photo-birefringent effects in crystalline AlGaAs mirror coatings