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Amorphous Silicon with Extremely Low Absorption: Beating Thermal Noise in Gravitational Astronomy
摘要： Amorphous silicon has ideal properties for many applications in fundamental research and industry. However, the optical absorption is often unacceptably high, particularly for gravitational-wave detection. We report a novel ion-beam deposition method for fabricating amorphous silicon with unprecedentedly low unpaired electron-spin density and optical absorption, the spin limit on absorption being surpassed for the first time. At low unpaired electron density, the absorption is no longer correlated with electron spins, but with the electronic mobility gap. Compared to standard ion-beam deposition, the absorption at 1550 nm is lower by a factor of ≈100. This breakthrough shows that amorphous silicon could be exploited as an extreme performance optical coating in near-infrared applications, and it represents an important proof of concept for future gravitational-wave detectors.
关键词： amorphous silicon,thermal noise,gravitational-wave detection,ion-beam deposition,optical absorption
更新于2025-09-23 15:21:01
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Towards the LISA backlink: experiment design for comparing optical phase reference distribution systems
摘要： LISA is a proposed space-based laser interferometer detecting gravitational waves by measuring distances between free-floating test masses housed in three satellites in a triangular constellation with laser links in-between. Each satellite contains two optical benches that are articulated by moving optical subassemblies for compensating the breathing angle in the constellation. The phase reference distribution system, also known as backlink, forms an optical bi-directional path between the intra-satellite benches. In this work we discuss phase reference implementations with a target non-reciprocity of at most 2π μrad √Hz?1 for a wavelength of 1064 nm in the frequency band from 0.1 mHz to 1 Hz. One phase reference uses a steered free beam connection, the other one a fiber together with additional laser frequencies. The noise characteristics of these implementations will be compared in a single interferometric set-up with a previously successfully tested direct fiber connection. We show the design of this interferometer created by optical simulations including ghost beam analysis, component alignment and noise estimation. First experimental results of a free beam laser link between two optical set-ups that are co-rotating by ±1° are presented. This experiment demonstrates sufficient thermal stability during rotation of less than 10?4 K √Hz?1 at 1 mHz and operation of the free beam steering mirror control over more than 1 week.
关键词： laser interferometer space antenna,gravitational wave detection,precision metrology,laser interferometry,stray light
更新于2025-09-23 15:19:57
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Relativistic Evaluation Models of Laser Time Transfer between Satellites Resulting from Orbit Perturbations and Attitude Jitters
摘要： The realization of picosecond level laser time transfer between satellites plays a key role in microgravity scientific missions, such as gravitational wave detection, next generation GNSS (Global Navigation Satellite System), deep space exploration, testing general relativity and searching for dark matter. In picosecond or higher level, a deep insight of relativistic error of laser time transfer between satellites induced by orbit perturbations and attitude jitters is urgently needed, which contributes to the compensation of relativistic error. Firstly, this paper points out the problem of orbit perturbations and attitude jitters. Then, the relativistic evaluation models of one-way laser time transfer and two-way laser time transfer resulting from orbit perturbations and attitude jitters are investigated. The relativistic evaluation models are proposed with incorporation of attitude dynamics and orbit dynamics of satellites, as well as relativistic models of one-way laser time transfer and two-way laser time transfer. Simulation studies are carried out to analyze the effect of orbit perturbations and attitude jitters on the relativistic error. Simulation results show that the relativistic error induced by orbit perturbations increases with time and the relativistic error induced by attitude jitters displays periodic variation. Furthermore, the relativistic error of two-way laser time transfer is less than one-way laser time transfer.
关键词： Laser time transfer,Relativistic evaluation models,Gravitational wave detection,Orbit perturbations,Attitude jitters
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Characterization, Integration and Operation of a 100-W Solid State Amplifier in the Advanced-VIRGO Pre-Stabilized Laser System
摘要： VIRGO is a 3-km-arm laser interferometer for gravitational wave detection in the 20 Hz - 5 kHz frequency band. Its second-generation version, Advanced VIRGO, aims at reducing the detector noise by a factor of ten compared to the first generation, with the progressive deployment of new technologies and equipment. The first detections of gravitational waves with VIRGO were made in August 2017. For its next scientific observations with an increased sensitivity, a pre-stabilized laser system twice as powerful has been developed. It comprises a new 100-W solid-state amplifier pumped at 878.7 nm. It is the first time such amplifier is integrated in a gravitational wave detector, LIGO detectors using a 70 W amplifier pumped at 808 nm. Power noise, long term power stability, frequency noise, beam jitter and transverse mode quality have been extensively studied and compared to Advanced VIRGO requirements.
关键词： beam jitter,solid-state amplifier,Advanced VIRGO,power noise,laser interferometer,frequency noise,gravitational wave detection
更新于2025-09-11 14:15:04