Design of a large aperture, tunable, Pancharatnam phase beam steering device.

Replacing mechanical optical beam steering devices with non-mechanical electro-optic devices has been a long-standing desire for applications such as space-based communication, LiDAR and autonomous vehicles. While promising progress has been achieved to non-mechanically deflect light with high efficiency over a wide angular range, significant limitations remain towards achieving large aperture beam steering with a tunable steering direction. In this paper, we propose a unique liquid crystal based Pancharatnam Phase Device for beam steering which can provide both tunability and a fast response times in a format scalable to large apertures. This architecture employs a linear array of phase control elements to locally control the orientation of the liquid crystal director into a cycloidal pattern to deflect transmitted light. The PCEs are comprised of a fringe field switching electrode structure that can provide a variable in-plane electric field. Detailed modeling of the proposed design is presented which demonstrates that such a device can achieve a high degree of uniformity as it rotates the LC molecules over the 180 ° angular range required to create a Pancharatnam phase device.

High-efficiency, tunable, fringe-field switching-mode beam steering based on a liquid crystal Pancharatnam phase.

We have fabricated, characterized, and analyzed a recently proposed non-mechanical beam steering device based on the Pancharatnam-Berry phase in a liquid crystal. The architecture of our proposed device employs a linear array of phase control elements (PCEs) to locally control the orientation of the liquid crystal director into a cycloidal pattern to deflect transmitted light. The PCEs are comprised of a fringe-field switching electrode structure that can provide a variable in-plane electric field. Detailed optimization of the director configuration is in a good agreement with experimental results showing that the half-wave retardation condition has been uniformly achieved across the aperture. Moreover, efficiency simulations using a finite-difference time-domain algorithm verify a high beam steering efficiency for the proposed device.

Design and characterization of an integrated surface ion trap and micromirror optical cavity.

We have fabricated and characterized laser-ablated micromirrors on fused silica substrates for constructing stable Fabry-Perot optical cavities. We highlight several design features which allow these cavities to have lengths in the 250-300 µm range and be integrated directly with surface ion traps. We present a method to calculate the optical mode shape and losses of these micromirror cavities as functions of cavity length and mirror shape, and confirm that our simulation model is in good agreement with experimental measurements of the intracavity optical mode at a test wavelength of 780 nm. We have designed and tested a mechanical setup for dampening vibrations and stabilizing the cavity length, and explore applications for these cavities as efficient single-photon sources when combined with trapped Yb171+ ions.

Orbital ordering in e(g) orbital systems: ground states and thermodynamics of the 120° model.

Orbital degrees of freedom shape many of the properties of a wide class of Mott insulating, transition metal oxides with partially filled 3d shells. Here we study orbital ordering transitions in systems where a single electron occupies the e(g) orbital doublet and the spatially highly anisotropic orbital interactions can be captured by an orbital-only model, often called the 120° model. Our analysis of both the classical and quantum limits of this model in an extended parameter space shows that the 120° model is in close proximity to several T=0 phase transitions and various competing ordered phases. We characterize the orbital order of these nearby phases and their associated thermal phase transitions by extensive numerical simulations and perturbative arguments.