Abstract
We reduce the intensity noise of laser light by using an electro-optic modulator and acousto-optic modulator in series. The electro-optic modulator reduces noise at high frequency (10 kHz to 1 MHz), while the acousto-optic modulator sets the average power of the light and reduces noise at low frequency (up to 10 kHz). The light is then used to trap single sodium atoms in an optical tweezer, where the lifetime of the atoms is limited by parametric heating due to laser noise at twice the trapping frequency. With our noise eater, the noise is reduced by up to 15 dB at these frequencies and the lifetime of the atom in the optical tweezer is increased by an order of magnitude to around 6 seconds. Our technique is general and acts directly on the laser beam, expanding laser options for sensitive optical trapping applications.
Highlights
Low noise lasers are required in a variety of scientific applications including gravitational wave detection [1], optical communication systems [2], quantum key distribution [3], and atom trapping [4]
An approach designed for a gravitational wave detector uses feedback on an acousto-optic modulator (AOM) for frequencies below 10 kHz and an optical cavity for mode cleanup and frequencies above 1 MHz [8]
To characterize the performance of our broadband noise eater, we measure the light intensity on an independent photodetector, and use a low-noise SR560 preamplifier from Stanford Research Systems to improve the signal-to-noise ratio
Summary
Low noise lasers are required in a variety of scientific applications including gravitational wave detection [1], optical communication systems [2], quantum key distribution [3], and atom trapping [4]. A common approach is to modulate the RF power in an AOM, modulating the amount of power in a diffracted order, but feedback is limited to the few hundreds of kHz range due to the speed of sound in the AOM crystal This problem can be alleviated by using an EOM in the amplitude modulator configuration, which can achieve a higher bandwidth. We pick off some light from the first order diffracted beam and measure its intensity on a PDA10A2 photodetector (bandwidth of 150 MHz) and use it to feedback onto the RF power of the AOM This is achieved with a separate home built PID servo, where the feedback signal is fed into the I port of a mixer to be mixed with the RF that drives the AOM. We use a combination of P gain and I gain
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
