Photonics and Nanostructures-Fundamentals and Applications最新文献

This is an introduction to the special issue “Micro and nano structured mid-IR to Terahertz materials and devices” which aims to cover recent developments in terms of photonics devices operating from the mid-infrared to terahertz wavelength ranges, with possible applications in spectroscopy, sensing, or communications.

Humidity monitoring is paramount in diverse applications, industrial, and medical applications. Surface Plasmon Resonance (SPR) is an optical detection technique capable of sensing various environmental parameters through changes in reflected optical spectra and has garnered significant attention. Typically, SPR sensing employs a single-point detection strategy with the sample at a fixed concentration to achieve optimal sensitivity, limiting its application in dynamic environmental testing. This study proposes an image-based SPR humidity monitoring method, integrating SPR with image processing, enabling dynamic parameter reconstruction, and achieving high responsiveness. Au-PVA is used as a sensing film. To attain the best sensing film thickness, sensing film thicknesses ranging from 94.0 $nm$ to 243.3 $nm$ were tested. Through optimizing film thickness and image data processing, high precision and dynamic responsiveness were achieved. Experimental results demonstrate a response time of 84 $ms$ and an average relative prediction error of 1.57 % for the sensor. Our research holds significant promise for dynamic and accurate humidity detection.

As a typical two-dimensional (2D) ferromagnetic insulator (FI), the Cr₂Si₂Te₆ (CST) has performance ferromagnetic properties. The previous investigation has shown that quantum mechanical simulation can get structure and electronic properties of CST, and the indirect gap value of CST is 0.6 eV by establishing its layered calculation. It implies that the CST is an excellent optical modulator due to larger infrared radiation absorption interval. Based on that, some groups conducted the research of fiber laser based on CST saturable absorber (SA). However, the exploration and application of 2D CST in optics is still in the early stage. In this investigation, the CST was utilized as a SA in an Er-doped fiber laser. The dual-wavelength mode-locked pulse could be observed when the pump power was adjusted from 25 to 140 mW. The CST was applied in Er-doped fiber as SA for generating dual-wavelength mode-locked pulse for the first time. It exhibits performance optical properties that provide a significant reference for exploring the application of 2D materials in ultrafast laser.

Optical technology has seen a revival from the previous decade, in terms of innovations and research, especially relating to optical integrated circuits. Similarly, Photonic Crystals (PCs) are one of the main contenders for the purpose. Therefore, this research work implicates different arrangements of the 3-Dimensional PC units based on the employment of a varying radius PC-cavity and its position i.e., at the beginning and within the middle of the PC-lattice. The effects of these PC-cavities are studied, investigating higher shifting in resonant wavelength, a narrower linewidth around 0.0061 µm and a quality factor of 99.59, comprising of a PC-cavity of radius 0.300 µm using input signal only i.e., coupled into the optical structure using the phenomenon of the Guided-mode-resonances (GMR). The structures are computed using an open-source FDTD platform, employing a stripe-model-based structure utilizing the Periodic Boundary Condition to save time and computational resources and later the PML for the realization of the Finite models. Moreover, the concluded structures based on the position of the PC-cavity, are demonstrated for the design of the all-optical-amplification device, executing a control signal reporting an 8 % of the amplification in the output of the input signal.

We find that the spontaneous and collective emissions have a strong influence on the excitation of two-level absorbers (atoms, molecules) interacting in resonance with the plasmonic mode near the metal nanoparticle. The spontaneous and collective emissions limit the absorption enhancement by the plasmonic mode and make the enhancement possible only with a fast, picosecond population relaxation of the upper absorbing states. Conditions for the maximum of plasmon-enhanced absorption in the presence of spontaneous and collective emissions are found. The nonlinearity in the nanoparticle-absorber interaction and in collective emission causes the bistability in the plasmon-enhanced absorption at high external field intensities and the plasmonic mode excitation.

We simulated the light extraction efficiency (LEE) of porous GaN-based InGaN/GaN micrometer-sized light-emitting diodes (μLEDs) emitting within the visible wavelength range using the finite-difference time-domain (FDTD) method. The simulations show that the embedding of a porous GaN layer with 40 % porosity reduces the bottom LEE, while the top side LEE of the μLEDs is increased. In addition, it also exhibits complex scattering properties that affect the microcavity structure of these devices. The LEE and the degree of microcavity structure disruption are related to nanopore size and location. This association weakens with increasing wavelength. Also, a decrease in nanopore size corresponds to a diminished impact on μLED optical properties. Since the porous GaN layer contributes to the deposition of high-quality InGaN, controlling pore size of the porous GaN layer will aid the development of GaN-based red μLEDs and full-color displays.

Meta-surfaces arrays are 2D meta-materials with a periodicity below the diffraction limit that permits to obtain homogeneous layers of resonant effective refractive index. In this work we present an analytical model that describes the electromagnetic behavior of meta-surfaces constituted by split-ring resonators (SRR). SRR resonance frequency can be adjusted by choosing their geometric parameters and the materials they are made of. Their deposition on a phase change material enables an optical modulation of resonance peak during the phase transition. We demonstrate a mid-infrared tunable SRR meta-surface using Vanadium dioxide (VO₂) as phase change material deposited on III-V semiconductors by low temperature pulsed laser ablation technique. The presented measurements exhibit a maximum of 100 cm⁻¹ resonance shift. This result is very promising for the conception of monolithic, robust, compact, frequency tunable III-V based devices in the mid-infrared.

The development of terahertz (THz) waveguides is limited by the high-conductivity losses of metals, the surface roughness, and the high-absorption of the dielectric materials. Consequently, dry air is certainly the most favorable medium to propagate THz radiations. A novel hollow-core THz waveguide enabling efficient THz wave propagation over 72 cm long length, is presented in this study. THz waves guiding in a hollow-core is achieved by an out-of-plane Photonic Band Gap (PBG) crystal cladding with a design inspired from the technology of hollow core PBG-crystal fibers. These fibers developed in the optical domains have demonstrated exceptional performances such as single mode propagation of light with low attenuation on kilometer length scales. The properties of the PBG guiding mechanism to forbid THz waves extension in the crystal cladding is exploited for enabling low-loss propagation in a waveguide fabricated with a highly absorptive material (ex. silica). PBG guidance into this new class of hollow-core THz waveguide were demonstrated theoretically and experimentally.

We present an experimental technique to accurately predict the formation of vibro-polaritons from a molecular polymeric film embedded in a resonant mid-infrared cavity. Using simple Fourier-transform reflectance measurement, we extract the complex dielectric function of a polyethylene film using Kramers-Kronig relations. The fitted dielectric function can be plugged into a numerical code to predict the strength and dispersion of the strong light-matter coupling regime between the quantized electromagnetic modes of a microcavity and the vibrational bands of the molecules. As a demonstration, we experimentally resolve the simultaneous formation of multiple vibro-polariton modes issued from the strong coupling of some vibrational bands of the methylene group (CH₂) in a 2.5-μm-thick polyethylene film embedded in a microcavity. We measure a Rabi splitting of 6.3 THz for the stretching doublet around 87.5 THz and a Rabi splitting of 1.1 THz for the scissoring doublet around 43.7 THz, in excellent agreement with numerical predictions.