ORCID Profile
0000-0002-3160-737X
Current Organisation
Australian National University
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Publisher: Springer Science and Business Media LLC
Date: 24-04-2019
DOI: 10.1038/S41598-019-42444-Y
Abstract: The development of a miniaturised device that provides efficient beam manipulation with high transmittance is extremely desirable for the broad range of applications including holography, metalens, and imaging. Recently, the potential of dielectric metasurfaces has been unleashed to efficiently manipulate the beam with full 2π-phase control by overlapping the electric and magnetic dipole resonances. However, in the visible range for available materials, it comes with the price of higher absorption that reduces efficiency. Here, we have considered dielectric amorphous silicon (a-Si) nanodisk and engineered them in such a way which provides minimal absorption loss in the visible range. We have experimentally demonstrated meta-deflector with high transmittance which operates in the visible wavelengths. The supercell of proposed meta-deflector consists of 15 amorphous silicon nanodisks numerically shows the transmission efficiency of 95% and deflection efficiency of 95% at operating wavelength of 715 nm. However, experimentally measured transmission and deflection efficiencies are 83% and 71%, respectively, having the experimental deflection angle of 8.40°. Nevertheless, by reducing the supercell length, the deflection angle can be controlled, and the value 15.50° was experimentally achieved using eight disks supercell. Our results suggest a new way to realise the highly transmittance metadevice with full 2π-phase control operating with the visible light which could be applicable in the imaging, metalens, holography, and display applications.
Publisher: American Chemical Society (ACS)
Date: 16-10-2020
Publisher: Springer Science and Business Media LLC
Date: 25-07-2018
DOI: 10.1038/S41377-018-0051-8
Abstract: We demonstrate that a dielectric anapole resonator on a metallic mirror can enhance the third harmonic emission by two orders of magnitude compared to a typical anapole resonator on an insulator substrate. By employing a gold mirror under a silicon nanodisk, we introduce a novel characteristic of the anapole mode through the spatial overlap of resonantly excited Cartesian electric and toroidal dipole modes. This is a remarkable improvement on the early demonstrations of the anapole mode in which the electric and toroidal modes interfere off-resonantly. Therefore, our system produces a significant near-field enhancement, facilitating the nonlinear process. Moreover, the mirror surface boosts the nonlinear emission via the free-charge oscillations within the interface, equivalent to producing a mirror image of the nonlinear source and the pump beneath the interface. We found that these improvements result in an extremely high experimentally obtained efficiency of 0.01%.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4RA11356J
Abstract: A silver incorporated graphene oxide nanocomposite was prepared and used for the detection of biomolecules using an absorbance based optical sensing method.
Publisher: Wiley
Date: 07-04-2015
Publisher: MDPI AG
Date: 17-09-2018
Abstract: We design an asymmetric nonlinear optical nanoantenna composed of a dielectric nanodisc and an adjacent nanobar. The proposed composite structure made of AlGaAs exhibits resonant response at both the fundamental and doubled frequencies. Being driven by the strong magnetic dipole resonance at the pump wavelength and a high-quality mode at the harmonic wavelength, the efficient second-harmonic radiation is generated predominantly along the vertical directions under the normally incident plane-wave excitation.
Publisher: Wiley
Date: 04-08-2022
Abstract: The development of nanoscale optical sensors is desirable for a broad range of applications, including wearable medical‐diagnostics, biochemical detection, and environmental monitoring. Optical detection platforms based on resonant nanostructures are the golden standard for miniaturized footprint and high optical sensitivity. These sensors function by measuring a shift in resonance wavelength upon binding of analytes to their surface. However, such measurements are sensitive to intensity fluctuations of the illuminating source and its wavelength calibration, which limits their applicability. Here, a novel optical sensing concept based on diffraction measurements from resonant dielectric metagratings is proposed and experimentally demonstrated. It is shown that this approach enables the direct measurement of unknown analytes with enhanced sensitivity and without the need for intensity calibrations. The intensified sensitivity of this metagrating‐sensor is derived from combining the resonant phenomena of the nanostructures with the tailored diffraction from the metagrating, thereby providing the highest sensitivity demonstrated to date amongst grating‐based sensors. As a proof of concept, the metagrating‐sensor was validated using an antibody binding assay, achieving a femtomolar‐level limit of detection. Due to their high sensitivity and robust performance, the proposed metagrating sensors pave the way for novel miniaturized medical diagnostics and biosensing applications.
Publisher: Elsevier BV
Date: 04-2018
Publisher: Springer Science and Business Media LLC
Date: 22-09-2021
DOI: 10.1038/S41467-021-25717-X
Abstract: Nonlinear light sources are central to a myriad of applications, driving a quest for their miniaturisation down to the nanoscale. In this quest, nonlinear metasurfaces hold a great promise, as they enhance nonlinear effects through their resonant photonic environment and high refractive index, such as in high-index dielectric metasurfaces. However, despite the sub-diffractive operation of dielectric metasurfaces at the fundamental wave, this condition is not fulfilled for the nonlinearly generated harmonic waves, thereby all nonlinear metasurfaces to date emit multiple diffractive beams. Here, we demonstrate the enhanced single-beam second- and third-harmonic generation in a metasurface of crystalline transition-metal-dichalcogenide material, offering the highest refractive index. We show that the interplay between the resonances of the metasurface allows for tuning of the unidirectional second-harmonic radiation in forward or backward direction, not possible in any bulk nonlinear crystal. Our results open new opportunities for metasurface-based nonlinear light-sources, including nonlinear mirrors and entangled-photon generation.
Publisher: Optica Publishing Group
Date: 22-06-2020
DOI: 10.1364/OE.392536
Abstract: We present a planar spectro-polarimeter based on Fabry-Pérot cavities with embedded polarization-sensitive high-index nanostructures. A 7 µm-thick spectro-polarimetric system for 3 spectral bands and 2 linear polarization states is experimentally demonstrated. Furthermore, an optimal design is theoretically proposed, estimating that a system with a bandwidth of 127 nm and a spectral resolution of 1 nm is able to reconstruct the first three Stokes parameters with a signal-to-noise ratio of -13.14 dB with respect to the the shot noise limited SNR. The pixelated spectro-polarimetric system can be directly integrated on a sensor, thus enabling applicability in a variety of miniaturized optical devices, including but not limited to satellites for Earth observation.
Publisher: American Chemical Society (ACS)
Date: 15-12-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4RA13777A
Abstract: In this review, the recent progress in the electrochemical sensing of dopamine with various graphene and their nanocomposite materials modified electrodes are presented.
Publisher: Informa UK Limited
Date: 15-02-2017
Publisher: Springer Science and Business Media LLC
Date: 22-02-2023
DOI: 10.1038/S41377-023-01078-6
Abstract: In the last decades, metasurfaces have attracted much attention because of their extraordinary light-scattering properties. However, their inherently static geometry is an obstacle to many applications where dynamic tunability in their optical behaviour is required. Currently, there is a quest to enable dynamic tuning of metasurface properties, particularly with fast tuning rate, large modulation by small electrical signals, solid state and programmable across multiple pixels. Here, we demonstrate electrically tunable metasurfaces driven by thermo-optic effect and flash-heating in silicon. We show a 9-fold change in transmission by V biasing voltage and the modulation rise-time of µs. Our device consists of a silicon hole array metasurface encapsulated by transparent conducting oxide as a localised heater. It allows for video frame rate optical switching over multiple pixels that can be electrically programmed. Some of the advantages of the proposed tuning method compared with other methods are the possibility to apply it for modulation in the visible and near-infrared region, large modulation depth, working at transmission regime, exhibiting low optical loss, low input voltage requirement, and operating with higher than video-rate switching speed. The device is furthermore compatible with modern electronic display technologies and could be ideal for personal electronic devices such as flat displays, virtual reality holography and light detection and ranging, where fast, solid-state and transparent optical switches are required.
Publisher: Springer Science and Business Media LLC
Date: 15-10-2015
Publisher: American Chemical Society (ACS)
Date: 26-12-2020
Abstract: High-index III-V semiconductor nanoantennas have gained great attention for enhanced nonlinear light-matter interactions, in the past few years. However, the complexity of nonlinear emission profiles imposes severe constraints on practical applications, such as in optical communications and integrated optoelectronic devices. These complexities include the lack of unidirectional nonlinear emission and the severe challenges in switching between forward and backward emissions, due to the structure of the susceptibility tensor of the III-V nanoantennas. Here, we propose a solution to both issues via engineering the nonlinear tensor of the nanoantennas. The special nonlinear tensorial properties of zinc-blende material can be used to engineer the nonlinear characteristics via growing the nanoantennas along different crystalline orientations. Based on the nonlinear multipolar effect, we have designed and fabricated (110)-grown GaAs nanoantennas, with engineered tensorial properties, embedded in a transparent low-index material. Our technique provides an approach not only for unidirectional second-harmonic generation (SHG) forward or backward emission but also for switching from one to another. Importantly, switching the SHG emission directionality is obtained only by rotating the polarization of the incident light, without the need for physical variation of the antennas or the environment. This characteristic is an advantage, as compared to other nonlinear nanoantennas, including (100)- and (111)-grown III-V counterparts or silicon and germanium nanoantennas. Indeed, (110)-GaAs nanoantennas allow for engineering the nonlinear nanophotonic systems including nonlinear "Huygens metasurfaces" and offer exciting opportunities for various nonlinear nanophotonics technologies, such as nanoscale light routing and light sources, as well as multifunctional flat optical elements.
Publisher: Wiley
Date: 05-03-2019
Abstract: Increasing demand for higher resolution of miniaturized displays requires techniques achieving high contrast tunability of the images. Employing metasurfaces for image contrast manipulation is a new and rapidly growing field of research aiming to address this need. Here, a new technique to achieve image tuning in a reversible fashion is demonstrated by dielectric metasurfaces composed of subwavelength resonators. It is demonstrated that by controlling the temperature of a metasurface the encoded transmission pattern can be tuned. To this end, two sets of nanoresonators composed of nonconcentric silicon disks with a hole that exhibit spectrally sharp Fano resonances and forming a Yin-Yang pattern are designed and fabricated. Through exploitation of the thermo-optical properties of silicon, full control of the contrast of the Yin-Yang image is demonstrated by altering the metasurface temperature by ΔT ≈ 100 °C. This is the first demonstrated technique to control an image contrast by temperature. Importantly, the turning technique does not require manipulating the external stimulus, such as polarization or angle of the illumination and/or the refractive index of this environment. These results open many opportunities for transparent displays, optical switches, and tunable illumination systems.
Publisher: American Chemical Society (ACS)
Date: 28-05-2019
DOI: 10.1021/ACS.NANOLETT.9B01112
Abstract: Second-harmonic generation (SHG) in resonant dielectric Mie-scattering nanoparticles has been hailed as a powerful platform for nonlinear light sources. While bulk-SHG is suppressed in elemental semiconductors, for ex le, silicon and germanium due to their centrosymmetry, the group of zincblende III-V compound semiconductors, especially (100)-grown AlGaAs and GaAs, have recently been presented as promising alternatives. However, major obstacles to push the technology toward practical applications are the limited control over directionality of the SH emission and especially zero forward/backward radiation, resulting from the peculiar nature of the second-order nonlinear susceptibility of this otherwise highly promising group of semiconductors. Furthermore, the generated SH signal for (100)-GaAs nanoparticles depends strongly on the polarization of the pump. In this work, we provide both theoretically and experimentally a solution to these problems by presenting the first SHG nanoantennas made from (111)-GaAs embedded in a low index material. These nanoantennas show superior forward directionality compared to their (100)-counterparts. Most importantly, based on the special symmetry of the crystalline structure, it is possible to manipulate the SHG radiation pattern of the nanoantennas by changing the pump polarization without affecting the linear properties and the total nonlinear conversion efficiency, hence paving the way for efficient and flexible nonlinear beam-shaping devices.
Publisher: Research Square Platform LLC
Date: 24-05-2022
DOI: 10.21203/RS.3.RS-1665364/V1
Abstract: Metasurfaces have recently realised many revolutionary applications such as metalenses, equation solvers, beam shapers, and holographic projection.1–4 However, the conventional metasurfaces are monotask due to their fixed dimensions. Therefore, realising multitask metasurfaces for applications such as beam steering, optical switches and meta-displays, which require fast and dynamic reconfigurability, has bottlenecked. To address this technological challenge, there has been a quest to enable tunability via mechanical tilting or stretching the s les, rotating the illumination angle or the incident light polarisation, use of chemical reactions, and others.5–8 However, most of these approaches still suffer from slow tuning rate, weak modulation, and bulky or non-solid state components. Here, we introduce electrically tunable metasurfaces that offer up to 9 folds surge in transmission, i.e. 90% transmission modulation depth, with switching time µs, i.e. one order of magnitude faster than video frame rates. To realise such a breakthrough, we have driven the designed metasurface by V spiked voltage, asymmetrically, for the first time in optoelectronics.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Wiley
Date: 02-08-2021
Abstract: Modern nanophotonics has witnessed the rise of “electric anapoles” (EDAs), destructive interferences of electric and toroidal electric dipoles, actively exploited to resonantly decrease radiation from nanoresonators. However, the inherent duality in Maxwell equations suggests the intriguing possibility of “magnetic anapoles,” involving a nonradiating composition of a magnetic dipole and a magnetic toroidal dipole. Here, a hybrid anapole (HA) of mixed electric and magnetic character is predicted and observed experimentally via dark field spectroscopy, with all the dominant multipoles being suppressed by the toroidal terms in a nanocylinder. Breaking the spherical symmetry allows to overlap up to four anapoles stemming from different multipoles with just two tuning parameters. This effect is due to a symmetry‐allowed connection between the resonator multipolar response and its eigenstates. The authors delve into the physics of such current configurations in the stationary and transient regimes and explore new ultrafast phenomena arising at sub‐picosecond timescales, associated with the HA dynamics. The theoretical results allow the design of non‐Huygens metasurfaces featuring a dual functionality: perfect transparency in the stationary regime and controllable ultrashort pulse beatings in the transient. Besides offering significant advantages with respect to EDAs, HAs can play an essential role in developing the emerging field of ultrafast resonant phenomena.
Publisher: Wiley
Date: 23-05-2019
Publisher: Elsevier BV
Date: 11-2016
Publisher: SPIE-Intl Soc Optical Eng
Date: 29-04-2020
Publisher: IOP Publishing
Date: 03-2022
Abstract: Tailoring optically resonant features in dielectric metasurfaces unveils a robust scheme to control electromagnetic near fields of light and thus to boost the nanoscale nonlinear light–matter interactions. Membrane metasurfaces offer unique possibilities for supporting multipolar resonances and meanwhile maintaining high mode volume for enhancing nonlinear frequency conversion. Here we design a silicon membrane metasurface consisting of dimer airy holes, as a versatile platform for generating four-wave mixing (FWM). We show that such a metasurface exhibits a multi-resonant feature, including a quasi bound state in the continuum (BIC) generated by the collective toroidal dipole mode excited in the designed subdiffractive periodic system. We show that via employing the BIC mode in the short-wave infrared (SWIR), together with other resonant enhanced electric near fields in the near-infrared (NIR) region, simultaneously, one can convert invisible SWIR light to visible light radiation with high efficiency, via FWM. We experimentally demonstrated a significant FWM emission enhancement from our metasurface, which leads to a conversion efficiency of 0.76 × 10 −6 using pump and signal beam peak intensities as low as 0.33 GW cm −2 and 0.17 GW cm −2 , respectively. Our results open new routes for enhancing nonlinear efficiencies for up-conversion processes.
Publisher: AIP Publishing
Date: 05-08-2021
DOI: 10.1063/5.0058768
Abstract: Optically resonant dielectric metasurfaces offer unique capability to fully control the wavefront, polarization, intensity, or spectral content of light based on the excitation and interference of different electric and magnetic Mie multipolar resonances. Recent advances of the wide accessibility in nanofabrication and nanotechnologies have led to a surge in the research field of high-quality functional optical metasurfaces, which can potentially replace or even outperform conventional optical components with ultra-thin features. Replacing conventional optical filtering components with metasurface technology offers remarkable advantages, including lower integration cost, ultra-thin compact configuration, easy combination with multiple functions, and less restriction on materials. Here, we propose and experimentally demonstrate a planar narrow bandpass filter based on the optical dielectric metasurface composed of Si nanoresonators in arrays. A broadband transmission spectral valley (around 200 nm) has been realized by combining electric and magnetic dipole resonances adjacent to each other. Meanwhile, we obtain a narrow-band transmission peak by exciting a high-quality leaky mode, which is formed by partially breaking a bound state in the continuum generated by the collective longitudinal magnetic dipole resonances in the metasurface. Owing to the in-plane inversion symmetry of our nanostructure, the radiation of this antisymmetric mode is inhibited at far field, manifesting itself a sharp Fano-shape peak in the spectrum. Our proposed metasurface-based filter shows a stable performance for oblique light incidence with small angles (within 10°). Our work implies many potential applications of nanoscale photonics devices, such as displays, spectroscopy, etc.
Publisher: Beilstein Institut
Date: 06-02-2018
DOI: 10.3762/BJNANO.9.44
Abstract: Novel types of optical hybrid metasurfaces consist of metallic and dielectric elements are designed and proposed for controlling the interference between magnetic and electric modes of the system, in a reversible manner. By employing the thermo-optical effect of silicon and gold nanoantennas we demonstrate an active control on the excitation and interference between electric and magnetic modes, and subsequently, the Kerker condition, as a directive radiation pattern with zero backscattering, via temperature control as a versatile tool. This control allows precise tuning optical properties of the system and stimulating switchable sharp spectral Fano-like resonance. Furthermore, it is shown that by adjusting the intermediate distance between metallic and dielectric elements, opposite scattering directionalities are achievable in an arbitrary wavelength. Interestingly, this effect is shown to have a direct influence on nonlinear properties, too, where 10-fold enhancement in the intensity of third harmonic light can be obtained for this system, via heating. This hybrid metasurface can find a wide range of applications in slow light, nonlinear optics and bio-chemical sensing.
No related grants have been discovered for Khosro Zangeneh Kamali.