An ultra-low noise and high-gain servo controller for ultra-stable laser systems

Area of Science:

• Physics
• Metrology
• Laser Technology

Background:

• Ultra-stable laser systems are crucial for precision measurements, with current state-of-the-art systems achieving fractional frequency stability around 10⁻¹⁷.
• Advancing stability to the 10⁻¹⁸ range is essential to approach fundamental thermal noise limits.
• Suppressing technical noise sources, especially electrical noise, below thermal noise levels is a key challenge.

Purpose of the Study:

• To improve ultra-stable laser systems by enhancing frequency stabilization feedback electronics.
• To develop an innovative servo controller architecture for superior noise suppression.
• To achieve fractional frequency stability in the 10⁻¹⁸ range.

Main Methods:

• Redesigned the frequency stabilization feedback electronics of an ultra-stable laser system.
• Implemented a novel servo controller with a 16-parallel operational amplifier pre-amp stage.
• Utilized a high-gain stage with four cascaded integrators in the servo controller.

Main Results:

• Achieved an input noise floor of 1.4 nV/√Hz at 1 Hz.
• Delivered a servo gain of 230 dB at 1 Hz.
• Demonstrated a residual in-loop error noise contributing to a fractional frequency stability of 4.7 × 10⁻²⁰, a two-order-of-magnitude improvement.

Conclusions:

• The redesigned electronics represent a significant stride towards 10⁻¹⁸ stability in ultra-stable lasers.
• This advancement effectively suppresses electrical noise, enabling further exploration of technical noise challenges.
• The improved laser system has broad appeal for high-precision applications like gravitational wave detectors and optical clocks.