Low-threshold lasing in a plasmonic laser using nanoplate InGaN/GaN

Plasmonic nanolaser as a new type of ultra-small laser, has gain wide interests due to its breaking diffraction limit of light and fast carrier dynamics characters. Normally, the main problem that need to be solved for plasmonic nanolaser is high loss induced by optical and ohmic losses, which leads to the low quality factor. In this work, InGaN/GaN nanoplate plasmonic nanolaser with large interface area were designed and fabricated, where the overlap between SPs and excitons can be enhanced. The lasing threshold is calculated to be ~6.36 kW/cm2, where the full width at half maximum (FWHM) drops from 27 to 4 nm. And the fast decay time at 502 nm (sharp peak of stimulated lasing) is estimated to be 0.42 ns. Enhanced lasing characters are mainly attributed to the strong confinement of electromagnetic wave in the low refractive index material, which improve the near field coupling between SPs and excitons. Such plasmonic laser should be useful in data storage applications, biological application, light communication, especially for optoelectronic devices integrated into a system on a chip.

Dirac-like cone-based electromagnetic zero-index metamaterials

Metamaterials with a Dirac-like cone dispersion at the center of the Brillouin zone behave like an isotropic and impedance-matched zero refractive index material at the Dirac-point frequency. Such metamaterials can be realized in the form of either bulk metamaterials with efficient coupling to free-space light or on-chip metamaterials that are efficiently coupled to integrated photonic circuits. These materials enable the interactions of a spatially uniform electromagnetic mode with matter over a large area in arbitrary shapes. This unique optical property paves the way for many applications, including arbitrarily shaped high-transmission waveguides, nonlinear enhancement, and phase mismatch-free nonlinear signal generation, and collective emission of many emitters. This review summarizes the Dirac-like cone-based zero-index metamaterials’ fundamental physics, design, experimental realizations, and potential applications.

Numerical and Experimental Demonstration of Inverse Designed Low-index Polarization-insensitive Wavelength Demultiplexer

The computational inverse design has paved the way for the design of highly efficient, compact, and novel nanophotonic structures beyond human intuition and trial-and-error approaches. Consequently, with this new design power, the exploration and implementation of multi-objective, complex, and functional nanophotonic devices become feasible. Herein, we used a recently emerged inverse design framework to demonstrate the design of a 1 * 2 polarization-insensitive wavelength division multiplexer (PIWDM) made of a low-refractive-index material with an index of 1.55. The designed PIWDM structure successfully steers toward the targeted channels for 1.30 mm and 1.55 mm with TE and TM polarizations, respectively. The transmission values were -2.42 and -2.18 dB for TE and -2.19 and -2.23 dB for TM polarization at the upper and lower waveguides, respectively. Taking advantage of the design with a low refractive index material, we scaled the structural dimensions corresponding to the microwave region, fabricated the compact device using a 3D printer, and conducted an experiment as a proof of concept. The experimentally verified PIWDM structure shows a power transmission efficiency of over -2.42 dB and a crosstalk value of less than -11.45 dB for the targeted wavelengths.

Multi-Layer Anti-Reflection Film Based on SiOx and NbOx by DC Pulse Sputter System with Inductively Coupled Plasma Source

The research on anti-reflection (AR) optical thin film has long sought to obtain high-performance reflection and transmission properties in photovoltaic and photonic devices. The study of multi-layer AR (M-AR) film with low- and high-refractive-index materials is essential to increase the selective transmittance and reflectance at visible light wavelengths. However, M-AR film exhibits low substrate adhesion and slow deposition rates. We developed a DC pulse sputter system incorporating an inductively coupled plasma (ICP) source of high density to obtain high-quality M-AR film. Six-layer AR optical thin film was simulated using SiOx as a low-refractive-index material and NbOx as a high-refractive-index material. The multi-layer AR film based on SiOx and NbOx (M-SiNb) was fabricated using DC pulse sputtering which incorporated an ICP source. M-SiNb film exhibited better properties than the optical simulation results at 550 nm (transmittance: 99.19%, reflectance: 0.87%). Similarly, the M-SiNb film fabricated using the ICP source had high transmittance and reflectance in the visible light region and excellent adhesion to the substrate notwithstanding the various mechanical tests it was subjected to. Consequently, the development of the DC pulse sputter system included the ICP source, and this study represents important research in the field of optical film.

III-nitride photonic cavities

Owing to their wide direct bandgap tunability, III-nitride (III-N) compound semiconductors have been proven instrumental in the development of blue light-emitting diodes that led to the so-called solid-state lighting revolution and blue laser diodes that are used for optical data storage. Beyond such conventional optoelectronic devices, in this review, we explore the progress made in the past 15 years with this low refractive index material family for the realization of microdisks as well as 2D and 1D photonic crystal (PhC) membrane cavities. Critical aspects related to their design and fabrication are first highlighted. Then, the optical properties of passive PhC structures designed for near-infrared such as their quality factor and their mode volume are addressed. Additional challenges dealing with fabrication pertaining to structures designed for shorter wavelengths, namely the visible to ultraviolet spectral range, are also critically reviewed and analyzed. Various applications ranging from second and third harmonic generation to microlasers and nanolasers are then discussed. Finally, forthcoming challenges and novel fields of application of III-N photonic cavities are commented.

Silicon photonics waveguide array sensor for selective detection of VOCs at room temperature

We report on the fabrication and characterization of a volatile organic compound sensor architecture addressing common drawbacks of photonic integrated sensors such as reusability and specificity. The proposed sensor, built on a silicon-on-insulator platform and based on arrayed waveguide interference, has a chemically selective polydimethylsiloxane polymer cladding, which encapsulates the waveguides and provides an expandable and permeable low refractive index material. This cladding material acts as the chemical transducer element, changing its optical properties when in contact with specific volatile organic compounds, whose presence in the context of environmental and public health protection is important to monitor. The sensor operates at room temperature and its selectivity was confirmed by multiple tests with water, toluene, chlorobenzene, and hexane, through which the sturdiness of the sensor was verified. A maximum spectral shift of about 22.8 nm was measured under testing with chlorobenzene, at a central wavelength of 1566.7 nm. In addition, a sensitivity of 234.8 pm/% was obtained for chlorobenzene mass percent concentrations, with a limit of detection of 0.24%m/m. The thermal sensitivity of the sensor has been found to be 0.9 nm/°C.

An Optimization of Two-Dimensional Photonic Crystals at Low Refractive Index Material

Photonic crystal (PC) is usually realized in materials with high refractive indices contrast to achieve a photonic bandgap (PBG). In this work, we demonstrated an optimization of two-dimensional PCs using a low refractive index polymer material. An original idea of assembly of polymeric multiple rings in a hexagonal configuration allowed us to obtain a circular-like structure with higher symmetry, resulting in a larger PBG at a low refractive index of 1.6. The optical properties of such newly proposed structure are numerically calculated by using finite-difference time-domain (FDTD) method. The proposed structures were realized experimentally by using a direct laser writing technique based on low one-photon absorption method.