All-optical switching in a continuously operated and strongly coupled atom-cavity system

Abstract

We experimentally demonstrate collective strong coupling, optical bi-stability (OB) and all-optical switching in a system consisting of ultracold 85 Rb atoms, trapped in a dark magneto-optical trap (DMOT), coupled to an optical Fabry-Perot cavity. The strong coupling is established by measuring the vacuum Rabi splitting (VRS) of a weak onaxis probe beam. The dependence of VRS on the probe beam power is measured and bi-stability in the cavity transmission is observed. We demonstrate control over the transmission of the probe beam through the atom-cavity system using a free-space off-axis control beam and show that the cavity transmission can be switched on and off in micro-second timescales using micro-Watt control powers. The utility of the system as a tool for sensitive, in-situ and rapid measurements is envisaged. [20,21] and, as we suggest here, in sensitive measurement of interactions. Essential requirements for many of these applications are atom-cavity strong coupling [9,11,12,14,21] and all-optical switching of the cavity output light [7,10,22,23]. Perhaps the most important goal is to engineer all-optical switches that are fast, yet can be operated with minimal power [22][23][24]. To this end, significant progress has been made in cavity QED systems consisting of a single atom strongly coupled to a high finesse cavity [21], which however require extremely precise system control. Here we study the relatively less explored complementary system consisting of an ensemble of trapped ultracold atoms collectively coupled to a low finesse cavity [9][10][11]. This results in a significant technical simplification and ease with which a low intensity, fast alloptical switch can be implemented.In this article, we show that atom-cavity collective strong coupling can be achieved on a non-cycling (i.e. open) transition in a continuously operated 85 Rb dark-spot magneto-optical trap (DMOT) [25,26]. The signature of collective strong coupling is vacuum Rabi splitting (VRS) which is observed using a weak on-axis probe beam. The dependence of VRS on the probe beam power is measured and optical bi-stability (OB) in the cavity transmission is observed. Control over the nature of OB curve using a freespace off-axis control beam is demonstrated. We finally show that the cavity transmission can be switched on and off in micro-second timescales using micro-Watt control powers. Remarkably, a DMOT of ultracold atoms coupled to a cavity can be operated analogous to both strongly coupled atom-cavity systems as well as weakly coupled vapor cell based cavity systems, and retain advantages of the respective systems.The details of the overall experimental apparatus which consists of an atom trap and an ion trap at the mode center of a low finesse optical cavity has been described elsewhere [11,27]. A schematic representation of parts relevant for the present experiments is shown in Fig. 1(a). The 85 Rb DMOT is loaded from a Rb dispenser source. The DMOT is formed by three mutually orthogonal pairs of counter-propagating cooling beams ...

Nondestructive detection of ions using atom-cavity collective strong coupling

“…The VRS decreases to in presence of the blue (473 nm) laser beam that is used to create 85 Rb + ions by photo-ionization in presence of trapped atoms, blue laser and trapped ions. The asymmetry in the shape of the peaks is due to slight onset of optical bi-stability [24,30] but the effect is small and predominantly systematic. The small systematic errors cancel out and therefore do not affect the ensuing analysis significantly.…”

Low-Threshold and High-Extinction-Ratio Optical Bistability within a Graphene-Based Perfect Absorber

“…In some resonant structures with third-order nonlinear optical materials, one given input state has two corresponding output states. Based on this unique property, OB can be applied to the fabrication of all-optical switches, memory cells, and transistors [ 1 , 2 , 3 , 4 , 5 , 6 ], which are the fundamental components of all-optical communication systems. Up to now, researchers have developed many different methods to realize OB, including ring cavities [ 7 , 8 ], photonic crystals [ 9 , 10 ], subwavelength waveguides [ 11 , 12 ] etc.…”

Doubly-resonant-cavity electromagnetically induced transparency

“…In past two decades, great progresses have been achieved in such cavity-atomic ensemble system. Various nonlinear optics effects have been studied experimentally or theoretically, including the intracavity electromagnetically induced transparency (EIT) [17,18], multiple laser thresholds [19], the photon blockade effect [20], strong and super-strong coupling [21], four-wave mixing [22], bistability [23,24] and multi-stability [23,25], as well as all-optical switching [23,[26][27][28][29]. However, in all previous experimental realizations of the all-optical switching, at most one cavity resonance for the signal light is used, while the control light is applied through free-space laser beam [17,24,27,28].…”

“…Various nonlinear optics effects have been studied experimentally or theoretically, including the intracavity electromagnetically induced transparency (EIT) [17,18], multiple laser thresholds [19], the photon blockade effect [20], strong and super-strong coupling [21], four-wave mixing [22], bistability [23,24] and multi-stability [23,25], as well as all-optical switching [23,[26][27][28][29]. However, in all previous experimental realizations of the all-optical switching, at most one cavity resonance for the signal light is used, while the control light is applied through free-space laser beam [17,24,27,28]. Although the cavity resonance for the control light has the advantages that save the control laser power and are easy for control-signal alignment, there is an experimental challenge for realizing the cavity that doubly-resonant with two atomic transitions (e.g.…”