Operating a near-concentric cavity at the last stable resonance

Abstract

Near-concentric optical cavities of spherical mirrors can provide technical advantages over the conventional near-planar cavities in applications requiring strong atom-light interaction, as they concentrate light in a very small region of space. However, such cavities barely support stable optical modes, and thus impose practical challenges. Here, we present an experiment where we maintain a near-concentric cavity at its last resonant length for laser light at 780 nm resonant with an atomic transition. At this point, the spacing of two spherical mirror surfaces is 207(13) nm shorter than the critical concentric point, corresponding to a stability parameter g = −0.999962(2) and a cavity beam waist of 2.4 µm.

Towards a deterministic interface between trapped-ion qubits and travelling photons

“…The second parameter combination consists of a three times smaller value of 3.9 µm for w 0 combined with a value of 252 ppm for T 2 . Macroscopic cavities with waists down to 2.44 µm have been realised [58], albeit with far higher losses than ours. The third parameter combination consists of ten ions maximally coupled to the cavity in superradiant entangled states, and a value of 252 ppm for T 2 .…”

An architecture for quantum networking of neutral atom processors

“…the distance of the mirrors from the concentric point. Although a positive critical distance represents a stable cavity, maintaining alignment of a cavity with very small critical distance is challenging 50 . In Fig.…”

“…We see that a collection efficiency well above 0.5 is achievable with a few-mm cavity length, and that the outcoupling mirror should have a certain transmission. With precise active alignment of the cavity mirrors near-concentric cavities with a critical distance less than a micron have been demonstrated 50 . However, we assumed a moderate critical distance of d crit = 10 µm.…”

“…Our goal is to have a cavity that is large enough that a MOT can be formed inside the cavity, and no atom-transport is required. Moving the cavity closer to the concentric point is a viable option as it has been demonstrated that a cavity in a near-concentric configuration can be maintained with d crit < 1 µm using active feedback 50 . A similar spacing for a 10 mm cavity would decrease the mode volume by a factor of ∼ 7, and increase the value for P aa by a factor of ∼ 2 to 1.1 × 10 −1 , and the rate to ∼ 5800 s −1 .…”

Vibration damping platform for cavity quantum-electrodynamics experiments

“…In particular, sharp vibration resonances severely limit the bandwidth of feedback loops and ultimately represent the main limitation to cavity stability. This is especially relevant for new generations of cQED experiments employing long cavities or complex geometries [4][5][6][7][8][9][10][11][12] , where mechanical resonances can occur at low frequencies.…”