Laser intensity noise suppression for space-borne gravitational wave mission.

Laser intensity noise is a main limitation of measurement and sensing missions represented by gravitational wave detection. We develop a noise decomposition model and design the core elements of the feedback loop based on the analysis results. We construct a fiber amplifier system with ultra-low intensity noise in the 0.1 mHz-1 Hz frequency band by the employment of an optoelectronic feedback loop that is specially designed, achieving a relative intensity noise below 6×10/Hz@0.1 mHz-1 Hz. By precise control of the temperature, we improve the temperature and mechanical stability of the fiber amplifier chain. Although the differential phase noise violates the LISA requirement in the 1 mHz-50 mHz frequency band, it meets the requirement at all other frequencies within the measurement range. The study provides an experimental basis and technologies for precise measurement and sensing systems at ultra-low frequency.