Tianhua Feng

Jinan University (Guangzhou, China) · Department of Electronic Engineering

Optomechanical interaction in microstructures plays a more and more important role in the fields of quantum technology, information processing, and sensing, among others. It is still a challenge to obtain a strong optomechanical interaction in a compact device. Here, we propose and demonstrate that compact ring resonators consisting of silicon nano...

Dynamic metasurfaces provide exciting opportunities for spatial light modulation with ultra‐compact footprint and high resolution. Designs reported so far typically suffer from efficiency problem due to the strong coupling between amplitude and phase modulation. Huygens metasurface design eliminates the back propagation with interference of dual re...

This study successfully implements spectrally distinguishable CdSe-ZnS core–shell colloidal quantum dot (CQD) microlasers by a simple, efficient spray printing technique and demonstrates its potential in biosensing. We have systematically characterized the optical properties of printed microring lasers with diameters less than 60 µm. The smallest s...

Optical encryption has attracted attention recently as information security becomes important in modern society. For most encryption methods based on metasurfaces, however, information is encrypted into the metasurfaces of physical forms, limiting information sharing and compatibility with digital information processing technology. Here, we demonst...

This Letter presents the first, to the best of our knowledge, thin-film lithium niobate-chalcogenide based microring acousto-optic modulator where an interdigital transducer and a chalcogenide strip waveguide are integrated on X-cut thin-film lithium niobate. The microring resonator exhibits a high loaded quality factor of 5 × 105. The developed hy...

A highly efficient on-chip acousto-optic modulator is as a key component and occupies an exceptional position in microwave-to-optical conversion. Homogeneous thin-film lithium niobate is preferentially employed to build the suspended configuration for the acoustic resonant cavity, with the aim of improving the modulation efficiency of the device. H...

A highly efficient on-chip acousto-optic modulator, as a key component, occupies an exceptional position in microwave-to-optical conversion. Homogeneous thin-film lithium niobate is preferentially employed to build the suspended configuration forming the acoustic resonant cavity to improve the modulation efficiency of the device. However, the limit...

On-chip stimulated Brillouin scattering (SBS) can be implemented with arsenic trisulfide (As2S3) waveguides and benefits various applications of microwave photonic, signal processing and sensing. While stiff top-claddings of silica on the waveguides can help to enhance the opto-acoustic interaction in SBS, the soft cladding can facilitate the reali...

We propose and demonstrate that strong optomechanical coupling can be achieved in a chain-like waveguide consisting of silicon nanorods. By employing quasi-bound states in the continuum and mechanical resonances at a frequency around 10 GHz, the optomechanical coupling rate can be above 2 MHz and surpass most microcavities. We have also studied cas...

Laplace operation, the isotropic second-order differentiation, on spatial functions is an essential mathematical calculation in most physical equations and signal processing. Realizing the Laplace operation in a manner of optical analog computing has recently attracted attention, but a compact device with a high spatial resolution is still elusive....

In this work, we report experimental characterizations of stimulated Brillouin scattering (SBS) in low-loss Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">25</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> S <sub xmlns:mml="http://www...

Deep-ultraviolet (DUV) bandpass filters play an important role in the fields of modern environmental disinfection and sterilization. A novel low-cost optical scattering material that can be used to manufacture flexible DUV bandpass filters is proposed. Considering both the refractive index matching condition and Rayleigh-Gans-Debye (RGD) scattering...

Quasi-bound states in the continuum (BICs) of metasurfaces are electromagnetic resonances with a high-quality (Q) factor embedded in a radiative continuum. The magnetic dipole type of the quasi-BIC (quasi-MDBIC) is associated with resonant enhancement of magnetic field near the metasurface. Here we show that the quasi-MDBIC of a compact dielectric...

Dielectric metasurfaces-based planar optical spatial differentiator and edge detection have recently been proposed to play an important role in the parallel and fast image processing technology. With the development of dielectric metasurfaces of different geometries and resonance mechanisms, diverse on-chip spatial differentiators have been propose...

We present a novel on-chip ultrasound detector based on the high-Q bound states in the continuum (BIC) in the chalcogenide glass photonic crystal slab (ChG-PCS) with high sensitivity of 84.9 pm · MPa ⁻ ¹ and 3-dB bandwidth of 670 MHz.

The Brillouin gain characteristics were demonstrated in two low-loss chalcogenide waveguides. Compared with the Brillouin gain coefficient of 202 m ⁻¹ W ⁻¹ in the As-S spiral waveguide, the gain performance of the Ge-As-S counterpart was measured to be 118 m ⁻¹ W ⁻¹ .

Light scattering by nanoparticles can be well understood and manipulated in the framework of induced electromagnetic multipoles. Conventionally, the scattering properties of light by nanoparticles are considered to be a result of superposition of the radiation from the induced multipoles due to their orthogonality. Here, we reveal that the interact...

Sub wavelength all-dielectric structures processing simultaneously electric and magnetic resonances provide a new horizon for tailoring magnetic light–matter interaction that is often overlooked in optical spectrum. In general, the magnetic field enhancement can be boosted by utilizing the magnetic resonances of dielectric resonators where structur...

On-chip channelless diffraction-free beam guiding enables dense integration of optical circuits in a reconfigurable manner, where total internal reflection, which is considered the cornerstone of guided-wave optics, is utilized to confine light in the out-of-plane direction. Here, we theoretically propose a physical mechanism to achieve on-chip cha...

We propose and demonstrate that optical analog computing of spatial differentiation and edge detection can be realized with a single layer of dielectric metasurface. The optical transfer function for second-order derivation is obtained by engineering the spatial dispersion of electric dipole resonance supported by the silicon nanodisks in the metas...

Huygens metasurfaces provide a versatile and efficient platform for exotic wave manipulation. Conventional transmissive Huygens metasurfaces rely on the interference between different multipole excitations to minimize the undesired reflection, but the different nature between multipoles introduces challenges on the bandwidth and practical applicati...

The spectrum overlapping of the radiative power between magnetic and electric dipole moments in nanoparticles can be used to realize unidirectional light scattering, which is promising for various kinds of applications. Nevertheless, it is still challenging to achieve such overlapping in a broadband manner. Herein, we propose that the combination o...

Spatial differentiation and edge detection have been proposed to realize with a dielectric metasurface by engineering the spatial dispersion of electric dipole resonance. The results show excellent performances for 2D images.

Sharp electromagnetic resonances play an essential role in physics in general and optics in particular. The last decades have witnessed the successful developments of high-quality (Q) resonances in microcavities operating below the light line, which however is fundamentally challenging to access from free space. Alternatively, metasurface-based bou...

We proposed and demonstrated that unidirectional light scattering, usually realized by utilizing induced electric and magnetic dipole moments, can also be achieved via only electric dipole moments induced in an assembly of plasmonic nanoparticles. The condition for such kinds of unidirectional scattering has been derived in the dipole approximation...

Uncovering how disorder affects light propagation is a key step to manipulating light transportation and localization utilizing engineered disorder in photonics. Herein, we study the disorder-induced localization, delocalization and inter-transition between them in the regions of photonic band gaps (PBGs) and their associated passbands of one-dimen...

Manipulating the spontaneous emission rate of optical emitters with all-dielectric nanoparticles benefits from their low-loss nature and thus provides relatively large extrinsic quantum yield. However, such Purcell effect greatly depends on the orientation of the dipole emitter. Here, we introduce the concept of isotropic magnetic Purcell effect wi...

Toroidal multipole moments are usually underestimated as they are quite weak in most cases of light-matter interaction. Herein, we reveal a strong link between the toroidal dipole resonance and the bound state in the continuum in the context of all-dielectric metasurfaces. We introduce the concept of toroidal dipole bound state in the continuum, in...

In terms of the law of momentum conservation, the optical pulling force (OPF) is a counterintuitive phenomenon for optical manipulation. We investigate analytically and numerically the tunable OPF exerted on the low refractive index nanoparticle (NP) in a hybrid dimer system when it is illuminated by a plane wave based on the coupled dipole approxi...

All-dielectric nanoantenna is a promising alternative of plasmonic optical antennas for engineering light emission because of their low-loss nature in the optical spectrum. Nevertheless, it is still challenging to manipulate directional light emission with subwavelength all-dielectric nanoantennas. Here, we propose and numerically demonstrate that...

We study the multipolar nature of guide resonance in photonic crystal waveguide which is consisted of periodic Mie type resonators. By reconstructed the guide resonance utilizing the induced multipole moments in one unit cell, we reveal the important roles of multipole modes play in the high-Q resonances.

Manipulating the spontaneous emission rate of optical emitters with all-dielectric nanoparticles benefits from their low-loss nature and thus provides relatively large extrinsic quantum yield. However, such Purcell effect greatly depends on the orientation of the dipole emitter. Here, we introduce the concept of isotropic magnetic Purcell effect wi...

We demonstrate that the electric and magnetic resonances of silicon nanoparticles can be tailored by an ultrathin electric conductive coating layer that is usually involved in the conventional scanning electron microscope (SEM) characterization. By utilizing three typical electric conductive coatings, including gold (Au), platinum (Pt), and graphit...

We introduce the concept of tunable ideal magnetic dipole scattering, where a nonmagnetic nanoparticle scatters lights as a pure magnetic dipole. High refractive index subwavelength nanoparticles usually support both electric and magnetic dipole responses. Thus, to achieve ideal magnetic dipole scattering one has to suppress the electric dipole res...

We propose a silicon hollow nanodisk for enhancing magnetic dipole emission. The Purcell factor can be more than 300, which is one order of magnitude larger than the silicon nanosphere case. It is demonstrated that the silicon hollow nanodisk resembles the function of an azimuthally polarized beam for tailoring the magnetic and electric dipole emis...

We experimentally demonstrate metamaterials with extreme dispersions by coiling up space with curled channels. An acoustic metamaterial is constructed with conical dispersion, supporting negative refraction with airborne sound. We have also demonstrated a double-negative microwave metamaterial by guiding through the cutoff-free TEM mode between two...

The coupling effects in electromagnetically induced transparency (EIT) for triatomic metamaterials are investigated at terahertz (THz) frequencies both experimentally and theoretically. We observed enhancement and cancellation of EIT with single transparency window, and also two additional ways to achieve double EIT transparency windows. One is fro...

We have derived a closed-form expression relating the S-parameters and the general constitutive matrix as a radiatively corrected local effective medium formula, which can work for thin metamaterials with low symmetries at normal incidence. We apply our approach to typical metamaterials possessing negative permeability or negative refractive index,...

Metamaterials are effectively homogeneous materials that display extraordinary dispersion. Negative index metamaterials, zero index metamaterials and extremely anisotropic metamaterials are just a few examples. Instead of using locally resonating elements that may cause undesirable absorption, there are huge efforts to seek alternative routes to ob...

supplementary info

We propose an ultra-thin metamaterial constructed by an ensemble of the same type of anisotropic aperture antennas with phase discontinuity for wave front manipulation across the metamaterial. A circularly polarized light is completely converted to the cross-polarized light which can either be bent or focused tightly near the diffraction limit. It...

We propose a novel solar cell structure with photonic nanocrystals coupled to quantum dots (QDs) for advanced management of photons and carriers. The photonic nanocrystals at the surface create an extra interaction between the photons and the QDs, which promotes light trapping. Photo-generated carriers can be efficiently transported by preparing ve...

We investigated an artificial Kerr-medium realized by actuated THz metamaterials. Instead of directly applying E-field inside the medium, we use micromechanical systems actuated by voltage to tune the phase shift. We established that the combined system can have a relationship between the phase shift and the voltage similar to a Kerr cell. A metama...

We propose to integrate photonic nanostructures coupled with Ge quantum dots (QDs) in crystalline Si solar cells for advanced management of photons and carriers. The photonic nanostructures at the surface can bring extra interaction between photons and QDs to result in efficient light trapping and increased photoresponse at infrared region. The typ...

A TiO(2) nanotube layer with a periodic structure is used as a photonic crystal to greatly enhance light harvesting in TiO(2) nanotube-based dye-sensitized solar cells. Such a tube-on-tube structure fabricated by a single-step approach facilitates good physical contact, easy electrolyte infiltration, and efficient charge transport. An increase of o...

Light harvesting in a TiO(2) nanotube-based dyesensitized solar cell can be greatly enhanced by coupling to a TiO(2) nanotubular photonic crystal with periodic structure along the axial direction, as demonstrated by Haitao Huang, Limin Zhou, and co-workers. The TiO(2) nanotubes and nanotubular photonic crystal are synthesized by a single anodizatio...

We design an ultra-thin infrared metamaterial thermal radiator which has nearly isotropic emission pattern for a wide range of angles. Our design is achieved by overlapping both the electric and magnetic resonances in the spectral domain and is insensitive to both TE and TM polarizations. The thermal emission of the metamaterial is nearly isotropic...

A plasmonic structure with double gold patches is proposed for enhancing the spontaneous emission of a magnetic dipole transition through a magnetic hot area. A Purcell factor of nearly 2000 can be obtained at optical frequencies together with a low sensitivity in spatial and spectral mismatches between the light emitter and the resonance mode. The...