Flexible autofocusing properties of ring Pearcey beams by means of a cross phase.

In this Letter, we introduce a new class of angular dependent autofocusing ring Pearcey beams by imposing a cross-phase structure. Due to this structure, the beam exhibits a non-uniform abrupt autofocusing behavior. Unlike the properties of the ring Pearcey beam without a cross phase [Opt. Lett.43, 3626 (2018)OPLEDP0146-959210.1364/OL.43.003626], we can flexibly adjust the focal length of the beam and its focusing ability, as well as the direction of the ring Pearcey beams, with the help of only the cross-phase structure. Furthermore, the Poynting vectors are employed to demonstrate convincingly the beam-focusing mechanism. Such beams with these fascinating characteristics are anticipated to find potential applications in optical tweezing, three-dimensional printing, material processing, and so on.

Generation of novel partially coherent truncated Airy beams via Fourier phase processing.

We propose theoretically and numerically, for the first time, the generation of novel partially coherent truncated Airy beams (NPCTABs) with Airy-like distributions for both intensity and degree of coherence via Fourier phase processing. We demonstrate a clear link between the magnitude and frequency of intensity and degree of coherence distributions oscillations of generated beams, and the source coherence and the phase screen parameter. Thus, the source coherence and phase can serve as convenient parameters to control the intensity and degree of the coherence of NPCTABs. Furthermore, we discover that NPCTABs are more stable than the fully coherent truncated Airy beams (FCTABs) during their propagation in free space and can maintain their Airy-like profile for an extended propagation distance. The interesting and tunable characteristics of these novel beams may find applications in particle trapping, phase retrieval, and optical imaging.

Self-healing properties of Hermite-Gaussian correlated Schell-model beams.

We study theoretically and experimentally the influence of the obstacle position separation from the source on the self-healing capacity of partially coherent beams using Hermite-Gaussian correlated Schell-model beams as a case in point. We establish that the shorter the distance between the obstacle and the source plane and the longer the distance between the obstacle and the observation (receiver) plane, the better the self-healing capacity of the beams. In addition, a similarity degree between the reconstructed and original beams is introduced to quantify the self-healing capacity of partially coherent beams. The derived interesting results may find applications in optical information processing, image transmission, and recovery.

Overview of Synthetic Methods to Prepare Plasmonic Transition-Metal Nitride Nanoparticles.

The search for new plasmonic materials that are low-cost, chemically and thermally stable, and exhibit low optical losses has garnered significant attention among researchers. Recently, metal nitrides have emerged as promising alternatives to conventional, noble-metal-based plasmonic materials, such as silver and gold. Many of the initial studies on metal nitrides have focused on computational prediction of the plasmonic properties of these materials. In recent years, several synthetic methods have been developed to enable empirical analysis. This review highlights synthetic techniques for the preparation of plasmonic metal nitride nanoparticles, which are predominantly free-standing, by using solid-state and solid-gas phase reactions, nonthermal and arc plasma methods, and laser ablation. The physical properties of the nanoparticles, such as shape, size, crystallinity, and optical response, obtained with such synthetic methods are also summarized.

Modal properties of a cylindrical graphene-coated nanowire deposited on a hexagonal boron nitride substrate.

Due to complementary chemical and optical characteristics, structural integration of graphene and hexagonal boron nitride (hBN) can lead to a promising platform for development of novel plasmonic devices. In this paper, we numerically investigate the modal behavior of a cylindrical graphene-coated nanowire (GNW) deposited on a thin hBN (GNW-hBN) substrate in the mid-infrared range. Our studies revealed that GNW-hBN can support hybridized plasmon-phonon modes in the upper reststrahlen band of hBN, which mainly originates from the strong coupling between plasmon modes in GNW and phonon modes in hBN. The characteristics of these hybrid modes can be effectively tuned by changing the chemical potential of graphene, hBN thickness, and gap distance between GNW and hBN. According to the results, by choosing smaller gap distances and tuning the chemical potential of graphene, GNW-hBN can exhibit a fundamental mode (m=0, where m is the azimuthal mode number) with higher effective index such that Real(neff) varies from 131.2-62.3 when the hBN thickness changes from 2-20 nm. In addition, the presence of an hBN slab can break the azimuthal symmetry of the high-order graphene plasmon modes (m≥1) in the GNW-hBN structure.

Non-Gaussian statistics and optical rogue waves in stimulated Raman scattering.

We explore theoretically and numerically optical rogue wave formation in stimulated Raman scattering inside a hydrogen filled hollow core photonic crystal fiber. We assume a weak noisy Stokes pulse input and explicitly construct the input Stokes pulse ensemble using the coherent mode representation of optical coherence theory, thereby providing a link between optical coherence and rogue wave theories. We show that the Stokes pulse peak power probability distribution function (PDF) acquires a long tail in the limit of nearly incoherent input Stokes pulses. We demonstrate a clear link between the PDF tail magnitude and the source coherence time. Thus, the latter can serve as a convenient parameter to control the former. We explain our findings qualitatively using the concepts of statistical granularity and global degree of coherence.

Hollow-Core Microstructured Optical Fiber Based Refractometer: Numerical Simulation and Experimental Studies.

In this paper, we numerically and experimentally propose a novel hollow-core microstructured optical fiber (HC-MOF) biosensor for refractive index determination. The sensing mechanism of the proposed sensor is based on photonic bandgap effect and the location of transmission maxima of the fiber, which is strongly depend on the liquid analyte RI filled in the fiber core. The proposed HC-MOF biosensor demonstrates the spectral sensitivity of 5636.3 nm/RIU with a RI detection range of 1.333 to 1.3385 for different ratios of plasma in blood serum in our experimental studies. The HC-MOF proposed here can detect similar liquid analytes with RI close to 1.33. The proposed sensor with a high sensitivity, ease of operation and the possibility of real-time sensing has a strong potential for detection of liquid analytes and biomolecules with possible applications in medicine, chemistry, and biology.

Continuous-Wave Coherent Raman Spectroscopy via Plasmonic Enhancement.

In this paper, we report a successful combination of stimulated Raman spectroscopy (SRS) and surface-enhanced Raman scattering (SERS) using cw laser sources and gold/silica nanoparticles with embedded reporter molecules. We describe the preparation method for our gold/silica nanoparticles as well as the effect of probe wavelength, pump and probe power, polarization and sample concentration on the cwSESRS signal. Altogether, a stable ~12 orders of magnitude enhancement in the stimulated Raman signal is achieved because of the amplification of both pump and probe beams, leading to the detection of pico-molar nanoparticle concentrations, comparable to those of SERS. The coherent Raman spectra matches the incoherent conventional Raman spectra of the reporter molecules. Unlike conventional incoherent SERS this approach generates a coherent stimulated signal of microwatt intensities, opening the field to applications requiring a coherent beam, such as Molecular Holography.