Squeezing out noise
Researchers at AEI Hannover develop new method to stabilize laser power, enabling more precise measurements in low-power experiments
Laser light is a versatile tool for scientists: Many precision experiments in fields ranging from life sciences to gravitational-wave detection are only possible with lasers. While the use of high laser power allows for more precise measurements, this may not be possible in certain experiments. At low laser power, precision is fundamentally limited by shot noise: a varying number of light quanta leads to fluctuations in laser power. Now, researchers at the Max Planck Institute for Gravitational Physics and at Leibniz University Hannover have developed a novel way to reduce shot noise using a taylored version of darkness, or quantum mechanical vacuum. This is the first realization of laser power stabilization with a squeezed vacuum. It reduces laser power noise over a broad frequency band by up to a factor of 3.7 below the previous fundamental shot noise limit. The results could improve experiments limited to low laser power levels. In their study, the researchers also discuss how their experiment could be modified to use the same method to stabilize the power fluctuations of high-power lasers, such as those used in current and future gravitational-wave detectors, such as the Einstein Telescope.
Paper abstract
Low-power-noise lasers are essential for many high-precision experiments. Shot noise imposes a fundamental limit on the power stability achievable with classical light sources. In this letter, we report the generation of bright squeezed light in the audio band, which can improve the sensitivity of otherwise shot-noise-limited measurements. It is (to our knowledge) the first experimental realization of a bright squeezed light source via the use of squeezed vacuum in a power stabilization scheme. We demonstrate a laser beam at a power of 9.9 mW with a broadband power noise suppression below the classical stabilization limit by up to 8.7+0.3−0.4 dB in the audio band, resulting in a bright squeezed beam with a power noise of 5.7+0.3−0.4 dB below shot noise for frequencies from 6 kHz to 20 kHz. We further conceptually outline a method to surpass this result in the future.
