Abstract
Laser phase noise remains a limiting factor in many experimental settings, including metrology, time-keeping, as well as quantum optics. Hitherto this issue was addressed at low frequencies ranging from well below 1 Hz to maximally 100 kHz. However, a wide range of experiments, such as, e.g., those involving nanomechanical membrane resonators, are highly sensitive to noise at higher frequencies in the range of 100 kHz to 10 MHz, such as nanomechanical membrane resonators. Here we employ a fiber-loop delay line interferometer optimized to cancel laser phase noise at frequencies around 1.5 MHz. We achieve noise reduction in 300 kHz-wide bands with a peak reduction of more than 10 dB at desired frequencies, reaching phase noise of less than -160 dB(rad2/Hz) with a Ti:Al2O3 laser. These results provide a convenient noise reduction technique to achieve deep ground-state cooling of mechanical motion.
Highlights
Lasers are nowadays well-established as the workhorse of modern telecommunication, metrology, as well as developing quantum technologies
We achieve noise reduction in 300 kHz-wide bands with a peak reduction of more than 10 dB at desired frequencies, reaching phase noise of less than −160 dB(rad2/Hz) with a Ti:Al2O3 laser. These results provide a convenient noise reduction technique to achieve deep ground-state cooling of mechanical motion
We employ a 50-meter-long fiber delay line combined with a balanced detection scheme to measure laser phase noise and subsequently use active feedback to reduce it at high frequencies
Summary
Lasers are nowadays well-established as the workhorse of modern telecommunication, metrology, as well as developing quantum technologies. We employ a 50-meter-long fiber delay line combined with a balanced detection scheme to measure laser phase noise and subsequently use active feedback to reduce it at high frequencies. In setup 1, we obtain P = 11 mW of total power impinging on the balanced detector, which allows for fiber-noise limited measurement of laser phase noise, increasing the signal-to-shot-noise ratio. This allows for the fiber noise to be larger than shot noise until up to 2 MHz. we minimize the beam path between setup 1 and the laser, which is less than 3 meters and includes only two mirrors. Any noise added in propagation will be treated as an additional detection noise
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