A low thermal noise and high reflection optical composite film structure and its preparation method

Abstract

The invention discloses a low-thermal-noise high-reflection type optical combined film structure and a preparation method thereof. The low-thermal-noise high-reflection type optical combined film structure is that a ultralow-expansion optical material is used as a substrate; a film coats the substrate, wherein the film is a multi-layer film formed by a sapphire film layer and a diamond layer which are arranged alternatively and combined by bonding or contact blocking. According to the low-thermal-noise high-reflection type optical combined film structure, the sapphire and diamond materials are used as the film coating layers and have extremely low mechanical loss factors, so that the brown thermal noise of the film coating material can be greatly reduced; meanwhile, the sapphire and diamond materials have a large difference in refraction rate, and therefore, high and low film layers can be formed to achieve high reflection rate; the combined film can be applied to high-tech fields such as an optical reference cavity, an optical interference instrument, an ultralow linewidth laser, an optical atomic clock and gravitational wave detection.

Description

technical field [0001] The invention belongs to the field of composite films, and relates to an optical composite film structure, in particular to a low-thermal-noise, high-reflection optical composite film structure and a preparation method thereof. Background technique [0002] Reducing the frequency noise of ultra-narrow linewidth lasers plays a vital role in high-tech applications such as optical atomic clocks, gravitational wave detection, and high-precision spectroscopy. In order to obtain a laser with extremely low frequency noise, the Pound-Drever-Hall (PDH) technique is usually used to precisely lock the laser frequency to the resonant frequency of an ultra-stable optical reference cavity. The frequency stability of ultra-narrow linewidth lasers is closely related to the stability of the effective cavity length of the optical reference cavity. The thermal noise that affects the length variation of the optical reference cavity is difficult to suppress and eliminate,...

AI Technical Summary

Problems solved by technology

The thermal noise that affects the length variation of the optical reference cavity is difficult to suppress and eliminate, and has become one of the main limiting factors for the further improvement of narrow linewidth laser performance

[0003] At present, methods to reduce the thermal noise of the optical reference cavity include: reducing the temperature of the optical reference cavity, using coatings and cavity materials with low mechanical loss, increasing the length of the reference cavity, and increasing the spot radius on the mirror surface, etc., but there are certain limitations

For example, an optical cavity made of single crystal silicon material can realize 10 -16 Ultra-stable lasers of the order of magnitude, but the silicon optical window is only suitable for the infrared band, and the loss is large, requiring a complex low-temperature system

The commonly used coating material SiO 2 / Ta 2 o 5 Although the optical window is wide, its mechanical loss factor is large, which directly leads to greater frequency stability

In 2014, Ye Jun’s group in the United States obtained a loss angle of 2.5×10 by attaching GaAs / AlGaAs DBR to the surface of molten silicon. -5 The coating material is commonly used coating material SiO 2 / Ta 2 o 5 1 / 10 of that, but its light-passing band is between 1000nm and 1100nm, and its application range is greatly limited

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