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Quantum 2.0 Conference and Exhibition

Progress toward a continuous superradiant laser

Zhijing Niu, Vera M. Schäfer, Julia Cline, Dylan J. Young, Yilun Song, James K. Thompson

Published Jan 1, 2023• 0 citations
Publisher

Abstract

We demonstrate continuous loading of strontium atoms into a high finesse ring cavity and observe continuous strong collective coupling in the form of a vacuum Rabi splitting between the atoms and the cavity on the 7.5 kHz 1S0 to 3P1 transition.
DOI
10.1364/quantum.2023.qw3b.6

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We demonstrate continuous loading of strontium atoms into a high finesse ring cavity and observe continuous strong collective coupling in the form of a vacuum Rabi splitting between the atoms and the cavity on the 7.5 kHz transition 1S0^1{\rm S}_01S0​ to 3P1^3{\rm P}_13P1​. The atoms are loaded into the cavity from a 3D narrow linewidth molasses, thus avoiding large magnetic field gradients and associated broadening of transition frequencies. The ring cavity allows us to realize a deterministic conveyor belt to transport atoms away from the loading region where the laser cooling beams lead to broadening of the strontium clock transition. We trap up to 10610^6106 atoms in an intracavity 813 nm lattice in the Lamb-Dicke regime, and transport the atoms along the cavity axis. This work opens the path to the creation of a continuous wave superradiant laser with millihertz linewidth enabling searches for new physics and the use of high-precision optical frequency references outside of low vibration laboratory environments.
We demonstrate continuous loading and strong collective coupling of atoms to a high finesse ring cavity. A series of spatially separated laser cooling stages delivers a continuous flux of 2.1(3)×10^{7} ^{88}Sr atoms/s into an intracavity magic wavelength lattice where the atoms are deterministically transported inside the ring cavity. We observe a continuous atom-cavity vacuum Rabi splitting, demonstrating the first steady-state strong collective coupling on a narrow linewidth atomic transition. This Letter opens the path to future continuous cold atom devices, such as a continuous wave superradiant laser with millihertz linewidth and low vibration sensitivity, enabling searches for new physics and technologies.
We report on recent progress in our lab involving cavity quantum electrodynamics with optically trapped atoms. \n \nIn particular, we will focus on a recent measurement of the Vacuum-Rabi splitting for one atom strongly coupled to the field of a high finesse optical resonator. This splitting is characteristic of the normal modes in the eigenvalue spectrum of the atom-cavity system. A new Raman scheme for cooling atomic motion along the cavity axis enables a complete spectrum to be recorded for an individual atom trapped within the cavity mode, in contrast to all previous measurements in cavity QED that have required averaging over many atoms.
Laser-cooled gases of atoms interacting with the field of an optical cavity are a powerful tool for quantum sensing and the simulation of open and closed quantum systems. They can display spontaneous self-organisation phase transitions, time crystals, new lasing mechanisms, squeezed states for quantum sensing, protection of quantum coherence, and dynamical phase transitions. However, all of these phenomena are explored in a discontinuous manner due to the need to stop and reload a new ensemble of atoms. Here we report the observation of hours-long continuous lasing from laser-cooled 88^{88}88Sr atoms continuously loaded into a ring cavity. The required inversion to produce lasing arises from inversion in the atomic momentum degree of freedom, a mechanism related directly to self-organization phase transitions and collective atomic recoil lasing, both of which were previously only observed in a cyclic fashion compared to the truly continuous behavior here. Further, the sensitivity of the lasing frequency to cavity frequency changes is 120 fold suppressed due to an atomic loss mechanism, opening an interesting new path to compensate cavity frequency noise for realizing narrow frequency references. This work opens the way for continuous cavity QED quantum simulation experiments as well as continuous superradiant lasers.
Atoms coupled to cavities provide an exciting playground for the study of fundamental interactions of atoms mediated through a common channel. Many of the applications of cavity QED and cold-atom experiments more broadly, suffer from limitations caused by the transient nature of an atomic loading cycle. The development of continuous operation schemes is necessary to push these systems to the next level of performance. Here we present a machine designed to produce a continuous flux of collimated atoms that traverse an optical cavity. The atom-light interaction is enhanced by a fast-decaying cavity optimal for studying phenomena where atomic properties dominate. We demonstrate the transition to a collective strong-coupling regime heralded by a normal-mode splitting. We observe a second phase with a binary normal-mode splitting born from an offset in the mean velocity of the atoms. Inverting the atomic ensemble in the collective strong-coupling regime, we measure continuous optical gain. This work sets the stage for studying threshold conditions for continuous collective phenomena, such as continuous superradiant lasing. Published by the American Physical Society 2024