arXiv subjects

Hannes Pfeifer

Publications and source records attributed to Hannes Pfeifer.

22 records · Page 2Linked to original sources

arXiv2016

Design of tunable GHz-frequency optomechanical crystal resonators

We present a silicon optomechanical nanobeam design with a dynamically tunable acoustic mode at 10.2 GHz. The resonance frequency can be shifted by 90 kHz/V^2 with an on-chip capacitor that was optimized to exert forces up to 1 $μ$N at 10 V operation voltage. Optical resonance frequencies around 190 THz with Q factors up to $2.2 \times 10^6$ place the structure in the well-resolved sideband regime with vacuum optomechanical coupling rates up to $g_0/2π= 353$ kHz. Tuning can be used, for instance, to overcome variation in the device-to-device acoustic resonance frequency due to fabrication errors, paving the way for optomechanical circuits consisting of arrays of optomechanical cavities.

physics.optics↗

arXiv2015

Position-squared coupling in a tunable photonic crystal optomechanical cavity

We present the design, fabrication, and characterization of a planar silicon photonic crystal cavity in which large position-squared optomechanical coupling is realized. The device consists of a double-slotted photonic crystal structure in which motion of a central beam mode couples to two high-Q optical modes localized around each slot. Electrostatic tuning of the structure is used to controllably hybridize the optical modes into supermodes which couple in a quadratic fashion to the motion of the beam. From independent measurements of the anti-crossing of the optical modes and of the optical spring effect, the position-squared vacuum coupling rate is measured to be as large as 245 Hz to the fundamental in-plane mechanical resonance of the structure at 8.7MHz, which in displacement units corresponds to a coupling coefficient of 1 THz/nm$^2$. This level of position-squared coupling is approximately five orders of magnitude larger than in conventional Fabry-Perot cavity systems.

physics.optics↗

arXiv2014

Generation and subwavelength focusing of longitudinal magnetic fields in a metallized fiber tip

We demonstrate experimentally and numerically that in fiber tips as they are used in NSOMs azimuthally polarized electrical fields (|E$_{\text{azi}}$|$^2$/|E$_{\text{tot}}$|$^2$ $\approx$ 55% $\pm $ 5% for 1.4μm tip aperture diameter and λ$_0$ = 1550nm), respectively subwavelength confined (FWHM $\approx$ 450nm $\approx$ λ$_0$/3.5) magnetic fields, are generated for a certain tip aperture diameter (d = 1.4μm). We attribute the generation of this field distribution in metal-coated fiber tips to symmetry breaking in the bend and subsequent plasmonic mode filtering in the truncated conical taper.

physics.optics↗

arXiv2013

Functional plasmonic nano-circuits with low insertion and propagation losses

We experimentally demonstrate plasmonic nano-circuits operating as sub-diffraction directional couplers optically excited with high efficiency from free-space using optical Yagi-Uda style antennas at λ= 1550 nm. The optical Yagi-Uda style antennas are designed to feed channel plasmon waveguides with high efficiency (45 % in coupling, 60 % total emission), narrow angular directivity (< 40°) and low insertion loss. SPP gap waveguides exhibit propagation lengths as large as 34 μm with adiabatically tuned confinement, and are integrated with ultra-compact (5 μm x 10 μm), highly dispersive directional couplers, which enable 30 dB discrimination over Δλ = 200 nm with only 0.3 dB device loss.

physics.optics↗