This conference presentation was prepared for the Nanophotonics, Micro/Nano Optics, and Plasmonics VIII conference at SPIE/COS Photonics Asia 2022

The abundant intrinsic point defects of ZnO are an important factor affecting its photoelectric performance. Identification and quantification of point defects is important both for the luminescent and optoelectronic applications, as well as for understanding the microscopic of spontaneous resistive switching behavior. As a shallow acceptor defect, zinc vacancy (VZn) plays an important role in ZnO photoluminescence, resistive switching, and electroluminescence. However, it is difficult to regulate the behavior of VZn defects, which leads to unclear effects on the photoelectric properties of ZnO. In this work, the effects of different VZn defect behaviors on the photoelectric properties of acceptor-rich ZnO (A-ZnO) microrod/tubes devices were studied by adjusting the concentration of VZn defects.

Chalcogenide phase-change materials are showing promise for the development of non-volatile memory and neuro-inspired computing technologies. One of the key issues in these devices is the energy consumption for the write (crystallization) and erase (amorphization) process. In this work, we propose to combine a PCM with a subwavelength chain of silicon nanoantennas with variable sizes following a parabolic profile. In comparison with a common slab waveguide, it was numerically demonstrated that the nanoparticle chain requires 24 times less energy for the writing and 42 times less energy for erasing process due to slow- light behavior near the photonic band-gap edge, which enhances local electromagnetic fields in the structure. Achieved results could be used for neuromorphic silicon photonics applications.

This conference presentation was prepared for the Nanophotonics, Micro/Nano Optics, and Plasmonics VIII conference at SPIE/COS Photonics Asia 2022.

Semiconductor nanowires have demonstrated great potential in all-photonic integrated circuits applications. However, the development of the controllable multidimensional nanowire assembly technique is still arguably in its infancy. We report here an all-dielectric silicon nanononamer that traps single and multiple nanowires for designing semiconductor nanolasers. We investigate the influences of light polarization on field enhancements, heating features, and force properties. The proposed structure exhibits strong optical forces and torques on nanowires. This structure is used both as optical tweezers for manipulating nanowires and as a semiconductor construction for performing nanolasing.

We construct a synthetic two-dimensional spatial-frequency space in one-dimensional modulated waveguide arrays, where topologically protected one-way transmission along the spatial boundary and Bloch oscillation along the frequency dimension are achieved.

The zero index metamaterials (ZIM) have been an intense research topic in nanophotonics. In ZIMs, the effective wavelength becomes infinite, and the spatial phase distribution of the propagating wave becomes uniform in the medium, overcoming many limitations imposed by the short spatial wavelength in the optical regime. This feature of ZIMs leads to applications including on-chip super coupling, nonlinear pumping, and on-chip orbital angular momentum generation. However, the traditional methods to realize ZIM face Ohm loss or out-of-plane radiation. In this work, we propose Steiner tree networks featuring a Dirac-like point and a photonic stop gap to realize low-loss 3D ZIM.

Optical chirality is intrinsically weak, and hard to tune in traditional bottom-up chiral perovskites. Here we realized all-dielectric halide perovskite chiral metasurfaces with a giant circular dichroism of 70% via high-throughput screening. Combining the giant optical chirality, unique light emission property and simple low-temperature solution processing technique, perovskite chiral metasurface paves the way towards real application in chiroptoelectronic and chiro-spintronic devices.

Visualization of enhanced optical fields in metallic and dielectric nanostructures resonated with infrared light is fundamentally important to control optical properties of metamaterials. However, conventional optical microscopic techniques, such as Fourier Transform Infrared absorption spectroscopy cannot resolve optically induced light fields of dielectric structures because of their low spatial resolution due to the diffraction limit of the infrared light. We introduced super-resolution far-field infrared spectroscopy to visualize the distribution of optical fields of dielectric-based metamaterials in the infrared region. Our newly developed novel infrared spectroscopic technique called as mid-infrared photothermal microscopy demonstrates to investigate optical field properties of silicon-based metamaterials at the sub-micrometer scale, which is far-beyond the diffraction limit of the infrared light.

The use of complex wave-vector in recent phenomena of spin-momentum locking inspired us to investigate a method of achieving improved transmission of light across optically opaque materials, solving the Helmholtz equation for complex values, via introducing a passive metasurface with a varying transmission phase and amplitude simultaneously, with interesting applications in acoustics structures, telecommunications bandwidth transmission or biophotonics for exotic beam shaping for analysing and treating malignant cells subcutaneously without damaging the skin.

This conference presentation was prepared for the Nanophotonics, Micro/Nano Optics, and Plasmonics VIII conference at SPIE/COS Photonics Asia 2022.

Far-field super-resolution optical technologies offer methods to high-capacity nanoscale optical memory. Typical approaches need high beam power and energy consumption. Because they can convert near-infrared excitation to ultraviolet and visible emission, upconversion nanoparticles show potential for photo-activation. Upconversion nanoparticles have metastable excited energy levels, enabling low-power stimulated emission depletion microscopy. We show the use of upconversion nanoparticles for low-power nanoscale photo-activation for high-capacity low-energy consumption optical memory. Upconversion nanoparticles were combined with photo-active compounds. Super-resolution irradiation excited upconversion nanoparticles for photo-activation in the nanocomposite. Written features showed nanoscale size under low-intensity irradiation and enabled multiple optical readouts.

In order to characterize nanomaterial-based devices, such as transistors, in working conditions (e.g. in ambient), we are constantly developing and improving our tip-enhanced Raman spectroscopy (TERS) system to probe our samples with both high chemical sensitivity and high spatial resolution. We have achieved the detection of temperature at nanoscale volumes using our technique called tip-enhanced THz-Raman spectroscopy (TE-THzRS) and have achieved sub-nanometer spatial resolution through our environment stable TERS system. We have also probed nanometer scale strain variations in monolayer graphene membranes using TERS. Now, aside from studying the strain distribution in graphene wrinkles, we are also studying carrier doping, one aspect of graphene’s electronic properties, through TERS.

This conference presentation was prepared for the Nanophotonics, Micro/Nano Optics, and Plasmonics VIII conference at SPIE/COS Photonics Asia 2022.

Dual microchannel (MCh) assist photonic crystal fiber-based plasmonic sensor has been proposed to detect a maximum of two analytes simultaneously. The proposed sensor will improve the detection time and accuracy. The performance of the sensor is investigated using the finite element method. Due to the symmetric structure, the proposed sensor shows similar performance for both channels. The sensor can be applied for both cases single and multi-analyte detection. The sensor exhibits the maximum wavelength sensitivity (WS) of 11,000 nm/RIU and amplitude sensitivity (AS) of 922 RIU-1for y-polarized modes, respectively. Due to the multi-analyte detection ability, the proposed sensor will be a suitable candidate for real-time biological and organic chemicals detections.

A photonic crystal fiber (PCF)-based plasmonic biosensor for coronavirus detection is analyzed numerically. This can detect COVID spike protein, antibody and the viral ribonucleic acid (RNA) using multi-analyte sensing approach. It is optimized for the specific analytes’ refractive index (RI) range. The sensor shows the average wavelength sensitivities of 2,009 nm/RIU for the protein spike, 1984 nm/RIU for the antibody spike and 2745 nm/RIU for the mutant RNA spike, respectively. The corresponding amplitude sensitivities are 135 RIU-1, 140 RIU-1 and 196 RIU-1. We anticipate the proposed sensor to be a competitive candidate for rapid multi-analyte point-of-care COVID detection.

We propose a graphene embedded highly sensitive double D-shaped photonic crystal fiber (PCF) based plasmonic sensor for multi-analyte detection. The double D-shaped PCF is fabricated using the standard stack-and-draw method and utilizes the scanning electron microscope (SEM) image for numerical investigations. The double D-shape structure facilitates simultaneous multi-analyte detection capability. The proposed sensor exhibits the maximum wavelength and amplitude sensitivities of 14,000 nm/RIU and 1,922 RIU-1 for x-polarized mode respectively. Due to its highly sensitive response and multi-analyte detection capability, the proposed sensor will be a suitable candidate for medical diagnostics, biochemical, and organic chemical detection.

Optical encryption plays an important role in information encryption. As an ultrathin optical elements, metasurfaces have the ability to precisely and fully control the incident light, which greatly promotes the development of optical information encryption. Here, we propose and demonstrate a method for optical encryption based on different spin-states of incident light via different intensity distributions generated by metasurface. The meta-devices with a numerical aperture (NA) of 0.6 and a diameter of 27 microns can independently encode two different binary numbers, where the light field distributions of the donut-shaped beam and the solid-shaped beam represent 0 and 1, respectively. On this basis, the optical encryption of information can be achieved through American Standard Code for Information Interchange (ASCII). The proposed method provides an ultracompact and highly secure platform for large-scale information encoding.

It is known that metasurfaces – two-dimensional structures consisted of periodically spaced nanoresonators of various shapes – can be used for spatial filtering of light, particularly for image processing applications. In this work, spatial Fourier filtering based on semiconductor metasurfaces is proposed to implement complex analog operations on the optical signal. We design, create and test a metasurface composed of silicon nanodisks implementing the convolution of an arbitrary image with a reference one. An ultrafast tunable Fourier filtering based on the gallium arsenide metasurface under femtosecond optical pumping is also proposed. The results of this study can be used to create a compact and lightweight optical devices for image processing applications.