Plasmonic Micro-Channel Assisted Photonic Crystal Fiber Based Highly Sensitive Sensor for Multi-Analyte Detection.

A dual-channel propagation controlled photonic crystal fiber (PCF)-based plasmonic sensor was presented to detect multiple analytes simultaneously. Plasmonic micro-channels were placed on the outer surface of the PCF, which facilitates an easy sensing mechanism. The sensor was numerically investigated by the finite element method (FEM) with the perfectly matched layer (PML) boundary conditions. The proposed sensor performances were analyzed based on optimized sensor parameters, such as confinement loss, resonance coupling, resolution, sensitivity, and figure of merit (FOM). The proposed sensor showed a maximum wavelength sensitivity (WS) of 25,000 nm/refractive index unit (RIU) with a maximum sensor resolution (SR) of 4.0 × 10-6 RIU for channel 2 (Ch-2), and WS of 3000 nm/RIU with SR of 3.33 × 10-5 RIU for channel 1 (Ch-1). To the best of our knowledge, the proposed sensor exhibits the highest WS compared with the previously reported multi-analyte based PCF surface plasmon resonance (SPR) sensors. The proposed sensor could detect the unknown analytes within the refractive index (RI) range of 1.32 to 1.39 in the visible to near infrared region (550 to 1300 nm). In addition, the proposed sensor offers the maximum Figure of Merit (FOM) of 150 and 500 RIU-1 with the limit of detection (LOD) of 1.11 × 10-8 RIU2/nm and 1.6 × 10-10 RIU2/nm for Ch-1 and Ch-2, respectively. Due to its highly sensitive nature, the proposed multi-analyte PCF SPR sensor could be a prominent candidate in the field of biosensing to detect biomolecule interactions and chemical sensing.

Multi-Analyte Detection Based on Integrated Internal and External Sensing Approach.

Highly sensitive, simple and multiplex detection capabilities are key criteria of point-of-care (POC) diagnosis in clinical samples. Here, a simple and highly sensitive multi-analyte detection technique is proposed by using photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor that employs both internal and external sensing approaches. The proposed sensor can detect two different analytes simultaneously by the internal and external plasmonic micro-channels. The light propagation through the sensor is controlled by the scaled-down air-holes to excite the free electrons of the plasmonic metal layers. The light- guiding and sensing properties of the sensor is numerically analyzed by using the Finite Element Method (FEM). The proposed sensor shows the maximum wavelength sensitivities (WS) of 12,000 nm/refractive index unit (RIU), and 10,000 nm/RIU, for the internal and external sensing approaches, respectively, and corresponding resolution of 8.33×10 -6 RIU and 1.0×10-5 RIU. Moreover, the hybrid sensor is applicable to detect unknown analyte refractive index (RI) in the range of 1.33 to 1.40 which covers extensively investigating analytes such as viruses, different cancer cells, glucose, proteins and DNA/RNA. Due to high sensing performance with multi-analyte detection capability, the proposed sensor can play a significant role to detect bio targets at the POC platform.

High-Efficiency Visible Light Manipulation Using Dielectric Metasurfaces.

The development of a miniaturised device that provides efficient beam manipulation with high transmittance is extremely desirable for the broad range of applications including holography, metalens, and imaging. Recently, the potential of dielectric metasurfaces has been unleashed to efficiently manipulate the beam with full 2π-phase control by overlapping the electric and magnetic dipole resonances. However, in the visible range for available materials, it comes with the price of higher absorption that reduces efficiency. Here, we have considered dielectric amorphous silicon (a-Si) nanodisk and engineered them in such a way which provides minimal absorption loss in the visible range. We have experimentally demonstrated meta-deflector with high transmittance which operates in the visible wavelengths. The supercell of proposed meta-deflector consists of 15 amorphous silicon nanodisks numerically shows the transmission efficiency of 95% and deflection efficiency of 95% at operating wavelength of 715 nm. However, experimentally measured transmission and deflection efficiencies are 83% and 71%, respectively, having the experimental deflection angle of 8.40°. Nevertheless, by reducing the supercell length, the deflection angle can be controlled, and the value 15.50° was experimentally achieved using eight disks supercell. Our results suggest a new way to realise the highly transmittance metadevice with full 2π-phase control operating with the visible light which could be applicable in the imaging, metalens, holography, and display applications.

Design and fabrication of copper-filled photonic crystal fiber based polarization filters.

This work demonstrates a broadband polarization filter based on copper-filled photonic crystal fiber (CFPCF). The proposed fiber is fabricated using the conventional stack-and-draw method. The polarization filter properties of the proposed CFPCF are investigated numerically by considering the cross-sectional scanning electron microscopy image of the fabricated CFPCF. It is observed that the magnitude of cross talk reached up to -206 dB over 0.8 mm length with a broad bandwidth of 282 nm at a central wavelength of 1790 nm. In addition, the polarization characteristics of the CFPCF including cross talk, central wavelength, and bandwidth can be adjusted by varying the diameter of the copper wire. It is shown that the resonance wavelength of the proposed filter can be tuned over the wide range of wavelengths from 1390 to 1890 nm. We have shown that by adjusting the copper wire diameter to 0.32Λ and 0.48Λ µm (Λ is pitch size), the proposed filter can operate at communication bands of 1310 and 1550 nm, respectively. The results suggest high-potential of the proposed fiber for polarization filtering and other sensing applications.