Search Results (5)

We report dual optical and acoustic negative refraction based on a defect-free phoxonic crystal within a triangular lattice. The phoxonic negative refraction is achieved based on abnormal dispersion effect, by intentionally creating convex equal-frequency contours for both photonic and phononic modes. As a potential application, negative refraction imaging for both photonic and phononic modes is also achieved. Numerical simulations based on the finite element method demonstrate the coexistence of negative refraction and the resultant imaging for electromagnetic and acoustic waves. Compared with the defect-based bandgap effects that need low fault tolerance, phoxonic negative refraction relying on passbands has considerable advantages in realizing controllable propagation of waves. The new scheme for the simultaneous control of electromagnetic and acoustic waves provides a potential platform for designing novel phoxonic devices. Full article

Nonreciprocal phonon emission is predicted theoretically from the coherent excitation of two coupled optomechanical cavities arranged along a phoxonic crystal nanobeam. The latter consists of a periodic array of holes and stubs and exhibits simultaneous photonic and phononic bandgaps. It is shown that nonreciprocal phonon emission arises from a combined effect of the spatial symmetry of the cavities and their underlying coupled phononic modes and the temporal phase shift between the excitation sources. This demonstration paves the way for the development of advanced integrated phonon networks and circuits, in which mechanical waves connect different elements in phononic and optomechanical structures. Full article

In this study, we propose a biochemical sensor that features a photonic cavity integrated with graphene. The tunable hybrid plasmonic-photonic sensor can detect the molecular fingerprints of biochemicals with a small sample volume. The stacking sequence of the device is “ITO grating/graphene/TiO₂/Au/Si substrate”, which composes a photonic band gap structure. A defect is created within the ITO gratings to form a resonant cavity. The plasmonic-photonic energy can be confined in the cavity to enhance the interaction between light and the analyte deposited in the cavity. The finite element simulation results indicated that the current sensor exhibits very high values in resonance shift and sensitivity. Moreover, the resonance spectrum with a broad resonance linewidth can identify the molecular vibration bands, which was exemplified by the fingerprint detections of protein and the chemical compound CBP. The sensor possesses an electrical tunability by including a graphene layer, which allowed us to tune the effective refractive index of the cavity to increase the sensor’s sensing performance. In addition, our device admits a phononic bandgap as well, which was exploited to sense the mechanical properties of two particular dried proteins based on the simplified elastic material model instead of using the more realistic viscoelastic model. The dual examinations of the optical and mechanical properties of analytes from a phoxonic sensor can improve the selectivity in analyte detections. Full article

Phoxonic crystals, which exhibit simultaneous phononic and photonic bandgaps, are promising artificial materials for optomechanical and acousto-optical devices. In this paper, simultaneous guidance of surface acoustic and surface optical waves in truncated phoxonic crystal slabs with veins is investigated using the finite element method. The phoxonic crystal slabs with veins can show dual large bandgaps of phononic and photonic even/odd modes. Based on the phononic and photonic bandgaps, simultaneous surface acoustic and optical modes can be realized by changing the surface geometrical configurations. Both acoustic and optical energies can be highly confined in the surface region. The effect of the surface structures on the dispersion relations of surface modes is discussed; by adjusting the surface geometrical parameters, dual single guided modes and/or slow acoustic and optical waves with small group velocity dispersions can be achieved. The group velocities are about 40 and 10 times smaller than the transverse velocity of the elastic waves in silicon and the speed of light in vacuum, respectively. Full article