A highly sensitive non-complex cored photonic crystal fiber sensor for hazardous chemical sensing with water, ethanol, and benzene analytes has been proposed and is numerically analyzed using a full-vector finite element method. The proposed fiber consists of a hexagonal core hole and two cladding air hole rings, operating in the lower operating wavelength of 0.8 to 2.6 µm. It has been shown that the structure has high relative sensitivity of 94.47% for water, 96.32% for ethanol and 99.63% for benzene, and low confinement losses of 7.31 × 10⁻⁹ dB/m for water, 3.70 × 10⁻¹⁰ dB/m ethanol and 1.76 × 10⁻¹³ dB/m benzene. It also displays a high power fraction and almost flattened chromatic dispersion. The results demonstrate the applicability of the proposed fiber design for chemical sensing applications.

Two integrated Young’s interferometer (YI) sensors based on long-range surface plasmon polariton (LRSPP) waveguides are presented. The first sensor is single-channel and based on a Y-junction splitter, and the other is multi-channel and based on a corporate feed structure. The multichannel YI enables simultaneous and independent phase-based monitoring of refractive index changes in multiple channels. The diverging output beams from the waveguides are overlapped in the far field to form interference patterns which are then post-processed using the fast Fourier transform (FFT) algorithm to extract phase values. The sensing capability of these YIs was demonstrated through sequential injection of solutions with increasing refractive index into the sensing channels. A detection limit of ∼ 1 × 10⁻⁶ RIU was obtained for both LRSPP based YIs, a significant improvement over measurements from similar structures using attenuation-based sensing.

This study experimentally demonstrates a Q‐switched fibre laser using a new tungsten tri‐oxide (WO ₃ )‐based saturable absorber (SA). Using the drop and casting approach, we managed to prepare a thin film that contained WO ₃ powders in polyvinyl alcohol. A small bit of the film was used to form an SA which was placed in a ytterbium‐doped fibre laser cavity to generate a Q‐switched laser. The laser, operating at 1063.78 nm, was realised at the threshold pump power of 85 mW with a repetition rate of 23.87 kHz and a pulse width of 5.56 μs. At the pump power of 147 mW, the laser produced the maximum pulse energy of 625 nJ, signal‐to‐noise ratio of 59 dB, the repetition rate of 39.79 kHz and pulse width of 2.37 μs. To the best of our knowledge, this is the first demonstration of using WO ₃ SA to generate the pulse laser in the 1 μm region.

We report the fabrication of a novel multimodal biosensor combining plasmonic and electrochemical detection. The plasmonic sensors are based on monitoring the propagation of Bloch long-range surface plasmon polaritons (LRSPPs) along thin narrow Au stripes, integrating grating couplers as input/output means. The electrochemical sensors use the same Au stripes as working electrodes with nearby Pt stripes integrated on-chip as counter electrodes. The structures are fabricated on a truncated 1D photonic crystal comprised of a 15-period stack of alternating layers of SiO ₂ /Ta ₂ O ₅ . The Au and Pt stripes are fabricated using bilayer lift-off photolithography, and the gratings are fabricated using e-beam lithography. The structures are arranged into arrays targeting multichannel biosensing. The wafer is covered with CYTOP as the upper cladding with etched microfluidic channels providing access to the sensing surfaces and is wafer-bonded to a Borofloat silica wafer to encapsulate the fluidic channels and enable edge (in-plane) fluidic interfacing. The wavelength response of the grating-coupled plasmonic waveguide sensors is presented along with surface sensing results. Cyclic voltammetry measurements using the Au and Pt stripes as the working and counter electrodes are also presented. [2021-0103]

We have experimentally demonstrated a Q-switched fiber laser operating in the 1 µm region by using tris-(8-hydroxyquinoline) aluminum (Alq₃) as a saturable absorber (SA). The Alq₃ was fabricated through a drop-casting technique, where the material was embedded into a polyvinyl alcohol (PVA) film so that it can effectively incorporated into a laser cavity. The fiber laser has produced a high pulse energy of 0.8 µJ and peak power of 90 mW. When the laser cavity was reduced from 25 m to 5 m, the peak power increased and the pulse energy dropped to 237.62 mW and 451.5 nJ, respectively. Additionally, the minimum pulse width was reduced from 9 µs to 1.9 µs.