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 that couple in a quadratic fashion to the motion of the beam. From independent measurements of the anticrossing of the optical modes and of the dynamic optical spring effect, a positionsquared vacuum coupling rate as large asg 0 =2π ¼ 245 Hz is inferred between the optical supermodes and the fundamental in-plane mechanical resonance of the structure at ω m =2π ¼ 8.7 MHz, which in displacement units corresponds to a coupling coefficient of g 0 =2π ¼ 1 THz=nm 2 . For larger supermode splittings, selective excitation of the individual optical supermodes is used to demonstrate optical trapping of the mechanical resonator with measuredg 0 =2π ¼ 46 Hz.
We experimentally demonstrate plasmonic nanocircuits operating as subdiffraction directional couplers optically excited with high efficiency from free-space using optical Yagi-Uda style antennas at lambda(0) = 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 degrees), and low insertion loss. SPP channel waveguides exhibit propagation lengths as large as 34 mu m with adiabatically tuned confinement and are integrated with ultracompact (5 x 10 mu m(2)), highly dispersive directional couplers, which enable 30 dB discrimination over Delta lambda = 200 nm with only 0.3 dB device loss
Optomagnonic systems, where light couples coherently to collective excitations in magnetically ordered solids, are currently of high interest due to their potential for quantum information processing platforms at the nanoscale. Efforts so far, both at the experimental and theoretical level, have focused on systems with a homogeneous magnetic background. A unique feature in optomagnonics is however the possibility of coupling light to spin excitations on top of magnetic textures. We propose a cavity-optomagnonic system with a non homogeneous magnetic ground state, namely a vortex in a magnetic microdisk. In particular we study the coupling between optical whispering gallery modes to magnon modes localized at the vortex. We show that the optomagnonic coupling has a rich spatial structure and that it can be tuned by an externally applied magnetic field. Our results predict cooperativities at maximum photon density of the order of C ≈ 10 −2 by proper engineering of these structures.Introduction.-Optomagnonics is an exciting new field where light couples coherently to elementary excitations in magnetically ordered systems. The origin of this photon-magnon interaction is the Faraday effect, where the magnetization in the sample causes the light's polarization plane to rotate. Conversely, the light exerts a small effective magnetic field on the material's magnetic moments. Shaping the host material into an optical cavity enhances the effective coupling according to the increased number of trapped photons.Recent seminal experiments have demonstrated this coupling [1][2][3]. In these, an Yttrium Iron Garnet (YIG) sphere serves as the host of the magnetic excitations and, via whispering gallery modes (WGM), as the optical cavity. The optomagnonic coupling manifests itself in transmission sidebands at the magnon frequency. So far, these experiments have probed mostly the homogeneous magnetic mode (Kittel mode) where all spins rotate in phase [4]. Very recently, optomagnonic coupling to other magnetostatic modes [5,6] has been demonstrated, albeit still on top of a homogeneous background [7,8].The Kittel mode, although it is the simplest one to probe and externally tune, is a bulk mode and has a suboptimal overlap with the optical WGMs living near the surface. Another caveat is the state of the art in terms of sample size, which is currently sub-millimetric. This results in modest values for the optomagnonic coupling and motivates the quest for smaller, micron-sized magnetic samples, as well as for engineering the coupling between magnetic and optical modes. Increasing the currently observed values of optomagnonic coupling is an urgent prerequisite for moving on to promising applications such as magnon cooling, coherent state transfer, or efficient wavelength converters [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].In microscale magnetic samples, the competition between the short-range exchange interaction and the boundary-sensitive demagnetization fields can lead to magnetic textures, where the magnetic gr...
Optomechanical systems offer new opportunities in quantum information processing and quantum sensing. Many solid-state quantum devices operate at millikelvin temperatureshowever, it has proven challenging to operate nanoscale optomechanical devices at these ultralow temperatures due to their limited thermal conductance and parasitic optical absorption. Here, we present a two-dimensional optomechanical crystal resonator capable of achieving large cooperativity C and small effective bath occupancy n b , resulting in a quantum cooperativity C eff ≡ C/n b > 1 under continuous-wave optical driving. This is realized using a two-dimensional phononic bandgap structure to host the optomechanical cavity, simultaneously isolating the acoustic mode of interest in the bandgap while allowing heat to be removed by phonon modes outside of the bandgap. This achievement paves the way for a variety of applications requiring quantum-coherent optomechanical interactions, such as transducers capable of bi-directional conversion of quantum states between microwave frequency superconducting quantum circuits and optical photons in a fiber optic network.
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