Indirect stress and air-cavity displacement measurement of MEMS tunable VCSELs via micro-Raman and micro-photoluminescence spectroscopy

We employ micro-Raman spectroscopy to optically infer the stress experienced by the legs of a bridge-type microelectromechanical systems (MEMS) used in high contrast gratings tunable vertical cavity surface emitting lasers (VCSELs). We then employ micro-photoluminescence (PL) spectroscopy to indirectly measure the air cavity displacement of the same MEMS structure. Results from micro-Raman show that electrostatically actuating the MEMS with a DC bias configuration yields increasing residual stress on the endpoints of the MEMS with values reaching up to 0.8 GPa. We simulated a finite element model via Comsol Multiphysics which agrees with the trend we observe based on our micro-Raman data. Our micro-photoluminescence (PL) spectroscopy showed that change in the air cavity of the VCSEL structure results in a change in the full width of the PL peak emitted by the layer consisting of 4 pairs of Distributed Bragg Reflectors (DBRs). The change in the full width of the PL peak was due to the change in the optical cavity induced by displacing the MEMS via externally applied bias and agrees with our transfer matrix convolution simulation. These optical characterization tools can be used for failure analysis, MEMS design improvements, and monitoring of MEMS tunable VCSEL devices for mass production and manufacturing.

Polariton Ring Currents and Circular Dichroism of Mg-porphyrin in a Chiral Cavity

By placing a Mg-porphyrin molecule in a chiral optical cavity, time reversal symmetry is broken, thus generating polariton ring currents even with linearly polarized light. These currents induce a circular...

Geometrical shapes effects of optical cavity on entanglement dynamics of optomechanical systems: A numerical analysis

In this work, a model of optomechanical system was investigated by analyzing the entanglement dynamics of two related mechanical oscillators in a modified system. Geometrical shapes effects of optical cavities on entanglement of a representative optomechanical system were investigated by means of performing numerical analysis. It was signified that the steady-state or the dynamic behavior of optomechanical engagement could be created owing to the strength of mechanical pairs, which are strong towards the oscillating temperature. In addition, the mentioned entanglement dynamics were seen to be entirely related to the natural state’s stability. Furthermore, rendering the mechanical damping effects, the critical mechanical coupling strength-related analytical expression, where the transition from a steady state to a dynamic clamp occurs, was reported. In the studied system, two identical mechanical oscillators were formed in different conditions of the optical cavities shapes.

Probing higher order optical modes in all-dielectric nanodisk, -square, and -triangle by aperture type scanning near-field optical microscopy

All-dielectric nanoantennas, consisting of high refractive index semiconductor material, are drawing a great deal of attention in nanophotonics. Owing to their ability to manipulate efficiently the flow of light within sub-wavelength volumes, they have become the building blocks of a wide range of new photonic metamaterials and devices. The interaction of the antenna with light is largely governed by its size, geometry, and the symmetry of the multitude of optical cavity modes it supports. Already for simple antenna shapes, unraveling the full modal spectrum using conventional far-field techniques is nearly impossible due to the spatial and spectral overlap of the modes and their symmetry mismatch with incident radiation fields. This limitation can be circumvented by using localized excitation of the antenna. Here, we report on the experimental near-field probing of optical higher order cavity modes (CMs) and whispering gallery modes (WGMs) in amorphous silicon nanoantennas with simple, but fundamental, geometrical shapes of decreasing rotational symmetry: a disk, square, and triangle. Tapping into the near-field using an aperture type scanning near-field optical microscope (SNOM) opens a window on a rich variety of optical patterns resulting from the local excitation of antenna modes of different order with even and odd parity. Numerical analysis of the antenna and SNOM probe interaction shows how the near-field patterns reveal the node positions of – and allows us to distinguish between – cavity and whispering gallery modes. As such, this study contributes to a richer and deeper characterization of the structure of light in confined nanosystems, and their impact on the structuring of the light fields they generate.

Bi-directional photonic switch and optical data storage in a hybrid optomechanical system

We propose to achieve quantum optical nonreciprocity in a hybrid qubit-optomechanical solid-state system. A two-level system (qubit) is coupled to a mechanically compliant mirror (via the linear Jaynes–Cummings interaction) placed in the middle of a solid-state optical cavity. We show for the first time that the generated optical bistability exhibits a bi-directional photonic switch, making the device a suitable candidate for a duplex communication system. On further exploring the fluctuation dynamics of the system, we found that the proposed device breaks the symmetry between forward and backward propagating optical modes (optical nonreciprocity), which can be controlled by tuning the various system parameters, including the qubit, which emerges as a new handle. The device thus behaves like an optical isolator and hence can store optical data in the acoustic mode, which can be retrieved later.

Crystallization in Zirconia Film Nano-Layered with Silica

Gravitational waves are detected using resonant optical cavity interferometers. The mirror coatings’ inherent thermal noise and photon scattering limit sensitivity. Crystals within the reflective coating may be responsible for either or both noise sources. In this study, we explored crystallization reduction in zirconia through nano-layering with silica. We used X-ray diffraction (XRD) to monitor crystal growth between successive annealing cycles. We observed crystal formation at higher temperatures in thinner zirconia layers, indicating that silica is a successful inhibitor of crystal growth. However, the thinnest barriers break down at high temperatures, thus allowing crystal growth beyond each nano-layer. In addition, in samples with thicker zirconia layers, we observe that crystallization saturates with a significant portion of amorphous material remaining.

Optical cavity-referenced terahertz synthesizer with 15-digit short-term stability

Stable terahertz sources are required to advance high precision terahertz applications such as molecular spectroscopy, terahertz radars, and wireless communications. Here, we demonstrate a photonic scheme of terahertz synthesis using an optical comb in stabilization to an ultra-low expansion optical cavity offering a 15-digit accuracy. By heterodyne photomixing of comb lines, terahertz frequencies of 0.10 – 1.10 THz are synthesized with a 2-mHz linewidth and a fractional instability of 3.26×10-15 at 1.3-s integration. Compared to other state-of-the-art counterparts, our terahertz synthesizer offers a fine frequency tuning capability in steps of 100 MHz and an extremely low level of phase noise below -70 dBc/Hz even at 1 Hz offset. Such unprecedented performance is expected to drastically improve the signal-to-noise ratio of terahertz radars, the resolving power of terahertz molecular spectroscopy, and the transmission capacity of wireless communications.