Light controllability, design flexibility, and non-linearity features of photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor enable high sensitivity in the field of biosensing. Here, bio-inspired butterfly-core shaped microstructure fiber-based plasmonic sensor is proposed where circular air-holes are arranged to enhance the sensing performance. Butterfly shaped core is designed to confine the incident light into the core by preventing light scattering through the cladding and helps to excite surface electron of plasmonic metal layer. Chemically stable plasmonic material gold is used to produce the SPR phenomenon. The analyte detection layer and the plasmon layer are located externally on the PCF surface to make the detection process more feasible. The sensor performance is studied based on the finite element method (FEM), and the structural parameters are tuned to obtain maximum sensor performance. This modified core-based sensor exhibits the maximum wavelength sensitivity (WS) of 56,000 nm/RIU and the amplitude sensitivity (AS) of 1,584 RIU-1 for the x-polarized mode. It also shows an improved sensor resolution (SR) of 1.8 ×10−6 RIU, along with a decent figure of merit (FOM) of 691 RIU-1. Moreover, this sensor can detect analyte refractive indexes (RI) within a broad RI range of 1.33 to 1.42 in the visible to near-infrared wavelength range (450–2100 nm). Finally, the proposed sensor may have possible application to detect organic chemicals, food quality, and diseases with high accuracy due to outstanding sensitivity and linearity.

We experimentally demonstrate that the Mosquito method is capable of fabricating single-mode polymer optical waveguides with multiple cores while maintaining an identical mode-field diameter among them. The Mosquito method we developed is a technique to form circular cores in polymer waveguides using a commercially available microdispenser and multi-axis syringe scanning robot. However, the core shape tends to deteriorate from a circle because of the monomer flow due to the needle scan. We also demonstrate both theoretically and experimentally for the first time in this paper that the needles with a tapered outer form or just titled straight needles enable to form cores with a high circularity even if those cores are dispensed on any heights from the substrate surface.

Optical beam-induced current (OBIC) mapping is widely used to characterize semiconductor lasers, particularly for failure analysis, in which the reliability has been a critical issue to be resolved spectrally and temporally. OBIC microscopy is advantageous for its non-invasiveness, when compared with electron beam-induced current (EBIC) microscopy. However, for high-speed devices, conventional OBIC methods may be limited in observing the spectral responses adequately. In this work, we present a modified OBIC microscopy based on a tunable ultrafast laser, to address the need for spectral resolving for precision failure spot analysis in vertical-cavity surface-emitting laser (VCSEL) diodes. The spectral OBIC response of VCSEL diodes is investigated by varying the irradiation wavelengths. Importantly, the ultrafast mode-locked laser provides broadband wavelength range to investigate photocurrent responses of the VCSELs sample. Specifically, the OBIC, electroluminescence (EL) detection, and the reflectance of the normal and the electrostatic discharge (ESD) damaged VCSELs are compared. We have found the ESD damaged VCSELs showing a redshifted spectral response.

Species identification of human and animal blood is of critical importance in the areas of custom inspection, forensic science, wildlife preservation, and veterinary purpose. In this study, the combination of Raman spectroscopy and a recurrent neural network (RNN) is proposed for the discrimination of 20 kinds of blood species including human, poultry, wildlife, and experimental animals. The chemometric multi-classification model based on RNN was established and optimized by hyperparameter tuning and structure selection. The performance scores of the bidirectional RNN model with GRU for 20 kinds of species are as follows: accuracy 97.7%, precision 97.8%, recall 97.8% and F1-score 97.7%. The model resistant to wavenumber drift and cross-instrumental model were also studied for practical application purpose using a subset of Raman spectra by both commercial and laboratory-built Raman spectrometers. The evaluation shows an accuracy of 98.2%. These results indicate that our approach has great potential for blood species identification in real application scenarios.

Research on terahertz (THz) spectrum is encountering an enormous booming due to its inherent and promising applications. In recent years, an utmost interest shown by the researchers towards a hollow-core anti-resonant fiber (HC-ARF) based THz bio-sensor because of its sublime sensing performance. In this paper, Zeonex based five-circular cladding tube hollow-core node-less negative-curvature fiber (HC-NNCF) has been proposed for sensing of chemical specimens in THz frequency range. By filling the proposed HC-NNCF sensor with targeted specimens of different refractive indices such as water (n = 1.330), ethanol (n = 1.354), and benzene (n = 1.366), the sensing characteristics of the sensor are numerically investigated using full vectorial finite-element-method (FEM) based COMSOL software. The simulation results show that the proposed HC-NNCF sensor exhibits a total propagation loss magnitude of 10−01 dB/m and a sensitivity response of 98.90%, 99.04%, and 98.90% for water, ethanol, and benzene, respectively, at 1 THz operating frequency. The practical implementation of this propose HC-NNCF sensor is feasible by the existing fabrication methodology. Consequently, the proposed terahertz sensor can be a promising candidate in food, biomedical, and industrial chemical research for opto-fluidic sensing applications.

A high-power optical transmitter module based on an SOA-assisted extended-reach EADFB laser (AXEL) chip was developed at a wavelength of 1.49 µm to improve the loss budget of current passive optical access networks. The fiber-coupled output power of the modulated signal is 10 dBm owing to the post-amplification effect of the integrated SOA with an extinction ratio of 10 dB. Fiber transmission was demonstrated at data rates of 1.25 and 2.5 Gbit/s, assuming GE-PON and G-PON downstream signals, respectively. Error-free transmission over 100-km fiber was achieved with loss budgets of 46 and 43 dB at 1.25 and 2.5 Gbit/s, respectively.

We demonstrate optical trapping of rare earth-doped NaYF4:Er/Yb nanorods of high aspect ratio (length 1.47 μm and diameter 140 nm) using a quasi Bessel beam (QBB) generated by positive axicon optical fiber tips. Propulsion or trapping of the nanorods is demonstrated using either single or dual fiber nano-tip geometries. The optical force exerted on the trapped nanorods, their velocities, and their positions have been analyzed. We determine the trap stiffness for a single nanorod to be 0.12 pN/μm (0.003 pN/μm) by power spectrum analysis and 0.13 pN/μm (0.015 pN/μm) by Boltzmann statistics in the direction perpendicular to (along) the fiber axes for an average optical power of 34 mW. The experiments illustrate the advantage of using a QBB for multiple nanorod trapping over a large distance of up to 30 μm.

A new technique is suggested for the generation of laser beams with an intensity profile specified. The technique is based on the coherent combining of radiation of a fiber laser array with adaptive control of the power and phase of Gaussian subbeams with plane wavefronts. The power and phase of the subbeams are determined for each intensity profile specified in the far field based on the inverse problem solution, for example, by the Gershberg–Saxton method. To form a required phase profile, the stochastic parallel gradient descent (SPGD) method is used along with the inversion of a required phase distribution with a phase corrector. The main advantages of the technique are the adaptive control of the intensity profile and a possibility of generating high-power laser beams. The results of numerical and field experiments are described.

We demonstrated a dispersion-managed, high-power, Tm-doped ultrashort pulse fiber laser using a single-wall-carbon-nanotube (SWNT) polyimide film. SWNTs with a diameter of 1.6 nm were synthesized with the enhanced direct injection pyrolytic synthesis (e-DIPs) method, and thin polyimide films in which SWNTs were dispersed were developed as saturable absorbers in the wavelength range λ = 1.8–2.0 µm. An all-fiber type, passively mode-locked, ultrashort-pulse Tm-doped fiber laser was demonstrated using the developed SWNT films. Wavelength tuning operation with gain fiber control and dispersion management of the developed fiber laser were investigated. Stable soliton and dissipative soliton mode locking operations were observed. High-power (102.6 mW) single-pulse mode-locking operation was achieved in a large positive dispersion regime. The repetition rate was 21.6 MHz, and the corresponding pulse energy was 4.75 nJ. To the best of our knowledge, this is the highest power operation of a Tm-doped fiber laser using carbon nanotubes and film-type devices with nano-carbon materials. The developed laser showed self-staring, stable performance and is useful for practical applications.

We propose a simple structure of a metamaterial (MM) to achieve near-perfect narrowband absorption. This MM utilizes both a plasmonic antenna and its complimentary structure for trapping electromagnetic fields, without the use of a complete ground plate compared to conventional designs. The simple design opens a new possibility of engineering perfect absorbers that can be easily fabricated, and thus many potential applications in mid-infrared include thermal imaging, energy harvesting, localized biological sensing, optical tweezers, and laser beam shaping.