We present an optical scheme to simultaneously characterize the cross-axis and rotational parasitic motions of a long-stroke shaker. By leveraging the geometric properties of a corner cube retroreflector mounted on the shaker load table, we independently sample pitch, yaw, and horizontal and vertical displacements with sampling rates above 10 kHz. We have applied our optical apparatus to a 400-mm-stroke shaker operated from 0.1 Hz to 100 Hz and present two forms of analysis: (A) Frequency-domain data for the four measured parasitic degrees of freedom, with the resulting implications for accelerometer calibration uncertainties, and (B) extracted trajectories of the shaker table, allowing visualization of the bowed linear guide below 0.5 Hz and higher harmonics and hysteresis above 10 Hz. Our findings demonstrate our optical measurement scheme to be an effective tool for the characterization of parasitic motion for long-stroke shakers. As an example, we determine the 'gravity error' in accelerometer calibration with our shaker to be ( 1 . 3 +/- 0.1) % times the acceleration amplitude at 0.1 Hz, providing a correction to reduce uncertainty from this effect by an order of magnitude.

The acousto-optic technique has been applied to acoustic sensing [1,2] and mapping [3] for over 20 years. A few years ago [4], we proposed the use of a high-finesse Fabry-Pérot cavity to enhance the sensitivity of the method and thus make it viable for low-uncertainty primary acoustic measurement and calibration. Using a plane-wave acoustic resonator, we have carried out a comparison of the acoustic pressure measured by a reciprocity-calibrated standard microphone to the acoustic pressure measured using the acousto-optic method in a Fabry-Pérot optical cavity with a finesse in the range of a few thousand, at an acoustic frequency of 1 kHz. We demonstrate agreement at the percent level, comparable to the uncertainty of the acousto-optic measurement. We believe that there is room for improvement of our acousto-optic measurement and that this early result indicates the viability of acousto-optic methods as an alternative to reciprocity for primary acoustic measurements.

We present progress in the development of a dynamic force reference instrument (KDFR) based on the Kibble principle. We describe the operating principle and design of the KDFR and discuss how the design for alternating current (AC) force measurements contrasts with Kibble balances for mass measurement and necessitates additional corrections to the force calculation. We further analyze the coil impedance, a critical factor for correcting the measured voltage in a single-mode AC Kibble measurement and illustrate a scheme for calibrating its temperature dependence.

We describe an optical sound standard in which the sound pressure is measured by using a high-finesse optical cavity to observe the induced change in the refractive index of the medium (acousto-optic effect).The optical refractive index of a substance varies with density, and for a compressible substance it will therefore vary in time in an acoustic field.To accurately measure the refractive index changes due to acoustic density variations, we enhance the induced optical phase shifts using a high-finesse optical cavity.By tracking the shift in the optical cavity resonance frequency we sensitively track the shift of the refractive index of the cavity medium and thereby the acoustic pressure in the cavity.We perform the optical measurement at standard telecom wavelength (1550 nm), thereby minimizing the cost of the optoelectronic components required.We report initial measurements in an acoustic resonator, comparing the pressure indicated by the optical cavity to the pressure indicated by a condenser microphone, at 1 kHz and 2 kHz acoustic frequencies.

Achieving electrically driven light sources on a silicon substrate is one of the great challenges in integrated optics. For low-power applications, one possible candidate could be Light Emitting Tunnel Junctions (LETJs) [1] . Unlike many semiconductor light sources that rely on direct-bandgap materials, the emission characteristics of LETJs are not strongly dependent on the material choice, but are determined by the electrical and optical environment of the tunnelling interface. While most electrons tunnel elastically from one electrode to the other, some can couple to and excite electromagnetic modes in a broad range of frequencies, spanning the microwave to the visible [1] – [3] .

We demonstrate arbitrary control of femtosecond timescale complex electrical-field transients using dielectric metasurfaces, enabling temporal vectorial ultrafast pulses with rich instantaneous polarization states and a simultaneously tailored spatial wavefront.

We report the emission of strong coherent broadband terahertz radiation from 6H-Silicon-Carbide (SiC) excited with optical pulses. The measured terahertz spectral signal-to-noise ratio is better than one thousand. We determine that the terahertz radiation is generated via second order optical nonlinearity (optical rectification). We present a measurement of the ratio of nonlinear susceptibility tensor elements χ (2) zzz/χ (2) zxx and the complex index of refraction of silicon carbide at THz frequencies.

A dielectric-metasurface-enabled pulse shaper able to tailor the temporal instantaneous polarization states within a near-infrared femtosecond pulse is demonstrated. Simultaneous complex wavefront shaping has been implemented by exploiting metasurfaces’ multi-functionalities within a single-pixel.

We present novel integrated photodetectors based on the radiation pressure of a plasmonic mode. Light absorbed in a plasmonic or hybrid plasmonic/optical waveguide builds a voltage along the length of the waveguide via the photon-drag effect. We implement this device concept for the first time and investigate its potential for fast, broadband, and inexpensive optical detection in an integrated platform.

Manipulation of plasmon modes at ultraviolet wavelengths using engineered nanophotonic devices allows for the development of high-sensitivity chiroptical spectroscopy systems. We present here an experimental framework based on aluminum-based crescent-shaped nanostructures that exhibit a strong chiroptical response at ultraviolet wavelengths. Through utilization of higher-order plasmon modes in wavelength-scale nanostructures, we address the inherent fabrication challenges in scaling the response to higher frequencies. Additionally, the distinct far-field spectral response types are analyzed within a coupled-oscillator model framework. We find two competing chiroptical response types that contribute toward potential ambiguity in the interpretation of the circular dichroism spectra. The first, optical activity, originates from the interaction between hybridized eigenmodes, whereas the second manifests as a response superficially similar to optical activity but originating instead from differential near-field absorption modes. The study of the chiroptical response from nanoplasmonic devices presented here is expected to aid the development of next-generation chiroptical spectroscopy systems.

Dielectric metasurfaces enable control of the temporal profile of large bandwidth, near-infrared femtosecond pulses. Using this approach, we demonstrate shaping of the time-domain polarization state within a single pulse.

We report terahertz metafilms designed to strongly couple hybridized lattice and fundamental dipole modes to form polaritons. By altering the metafilm's capacitance, the coupling strength of the dipole-lattice coupling is tuned from weak to strong.

The photovoltage generated in metal films conflicts with the prevailing intuitive model of light-metal momentum exchange, establishing the need for a new microscopic model of radiation pressure, and newly revealing the distribution of optical forces.

We demonstrate that the sign of the photon-drag effect in smooth gold films is crucially dependent on the surface environment and contrary to the prevailing intuitive model of direct momentum transfer to free electrons.

We demonstrate that the sign of the photon-drag effect in smooth metal films conflicts with the prevailing intuitive model of direct momentum transfer to free electrons, establishing the need for a new microscopic model of radiation pressure.

Two-dimensional atomically thin materials, most notably graphene and transition metal dichalcogenides (TMDs), have generated tremendous interest among researchers. The high electron mobility and strong light absorption exhibited by these materials make them attractive for opto-electronic applications. We will present our recent experimental and theoretical work on the ultrafast dynamics of collective excitations, such as excitons, phonons, and plasmons, in these materials for electronic and photonic device applications. We study the dynamics of excitons in 2D materials and optoelectronic devices using ultrafast optical/terahertz pump-probe and correlation spectroscopy. Our experimental work on metal dichalcogenide materials and devices (such as photodetectors) as well as our theoretical results show that defect assisted recombination involving capture of excitons and carriers by Auger scattering is the fastest mechanism for the non-radiative recombination of photoexcited electrons and holes. In particular, the very Coulomb interaction that resulted in the strongly bound excitons in these materials, causes extremely fast capture of the excitons by defects resulting in extremely poor quantum efficiencies in optoelectronic devices. The large sensitivity of device performance to defects is thus fundamental to 2D TMD materials. Defect-passivated 2D materials have demonstrated quantum efficiencies approaching ten percent. Our ultrafast two-pulse photovoltage correlation experiments show that the photoresponse of TMD photodetectors can be very fast making them useful for operation at frequencies in the hundreds of gigahertz range. Our recent experimental work has shown that 2D materials could be very promising for high frequency phononic devices. Our work has shown that mechanical oscillations in these atomically thin membranes can reach terahertz frequencies and are tunable from few tens of gigahertz to almost one terahertz. 2D material membranes can therefore enable MEMs resonator structures with record frequency-quality factor products at these high frequencies. Our ultrafast work in graphene plasmonic structures has revealed enormous potential for graphene based VLSI interconnects in which electrical signals are carried by plasmonic waves with much reduced propagation delays, losses, signal distortions, and cross-talk compared to conventional metal interconnects like copper.

We discuss recent efforts in realizing a surface plasmon resonator consisting of a dielectric cylinder surrounded by a metal film that supports whispering-gallery-type surface plasmon polaritons and higher order transverse magnetic modes with the capability of exhibiting high quality factors in the visible frequency range.

We propose a plasmon resonator consisting of a cylindrical hole in a metal film that supports whispering gallery type surface plasmon polariton modes exhibiting record-high quality factors (>750) in the visible frequency range.

Manipulating ultraviolet light presents unique challenges in technology. Here we demonstrate circular polarization selection at ultraviolet wavelengths over subwavelength distances using a flat-optical device consisting of Al chiral nanospirals periodically patterned on a glass substrate.

The strong Coulomb interactions and the small exciton radii in two-dimensional metal dichalcogenides can result in very fast capture of electrons and holes of excitons by mid-gap defects from Auger processes. In the Auger processes considered here, an exciton is annihilated at a defect site with the capture of the electron (or the hole) by the defect and the hole (or the electron) is scattered to a high energy. In the case of excitons, the probability of finding an electron and a hole near each other is enhanced many folds compared to the case of free uncorrelated electrons and holes. Consequently, the rate of carrier capture by defects from Auger scattering for excitons in metal dichalcogenides can be 100-1000 times larger than for uncorrelated electrons and holes for carrier densities in the 10(11)-10(12) cm(-2) range. We calculate the capture times of electrons and holes by defects and show that the capture times can be in the subpicosecond to a few picoseconds range. The capture rates exhibit linear as well as quadratic dependence on the exciton density. These fast time scales agree well with the recent experimental observations and point to the importance of controlling defects in metal dichalcogenides for optoelectronic applications.