Evaporative cooling by pulse width modulation (PWM) of optical dipole traps

Abstract

We introduce a method for cooling atoms in an optical dipole trap using pulse-width modulation (PWM) technique, without reducing the laser power of the dipole trap. The PWM technique involves digital modulation of the trap at a fixed frequency. The effective time-averaged dipole potential is lowered by adjusting the duty cycle of the modulation, thereby implementing evaporative cooling. We show that, this technique effectively reduces temperature and enhances phase space density. A comparison with the standard method of evaporative cooling has also been made. Apart from the atom loss due to reduction of the effective trapping potential, we observe an additional loss channel originating from the lack of trapping potential during the trap off time. This atom loss is observed at different modulation frequencies which are an order of magnitude higher compared to trapping frequency of dipole trap. The PWM technique provides an alternative to traditional evaporative cooling in scenarios where it is preferred that the laser power of the trap should be constant.

References in corpus (24)

• Many-Body Physics with Ultracold Gases
• Atom Interferometers
• All Optical Formation of an Atomic Bose-Einstein Condensate
• Experimental observation of the Anderson transition with atomic matter waves
• Resolving the gravitational redshift within a millimeter atomic sample
• A transportable optical lattice clock with $7\times 10^{-17}$ uncertainty
• Interleaved Atom Interferometry for High Sensitivity Inertial Measurements
• Fast machine-learning online optimization of ultra-cold-atom experiments
• Rapid production of ${}^{87}$Rb BECs in a combined magnetic and optical potential
• Rapid production of uniformly-filled arrays of neutral atoms
• Fast, Runaway Evaporative Cooling to Bose-Einstein Condensation in Optical Traps
• A quantum sensor: simultaneous precision gravimetry and magnetic gradiometry with a Bose-Einstein condensate
• Time-Averaged Adiabatic Potentials: Versatile traps and waveguides for ultracold quantum gases
• All-optical runaway evaporation to Bose-Einstein condensation
• Direct laser cooling to Bose-Einstein condensation in a dipole trap
• Preparation of hundreds of microscopic atomic ensembles in optical tweezer arrays
• Production of Sodium Bose--Einstein condensates in an optical dimple trap
• Eliminating light shifts in single-atom optical traps
• Optimizing the efficiency of evaporative cooling in optical dipole traps
• Evaporative cooling of a small number of atoms in a single-beam microscopic dipole trap
• Growth dynamics of a Bose-Einstein condensate in a dimple trap without cooling
• A mid-infrared magneto-optical trap of metastable strontium for an optical lattice clock
• All-Optical Matter-Wave Lens using Time-Averaged Potentials
• Asymmetric dynamical localization and precision measurement of BEC micromotion