SNROW-based highly sensitive label-free surface biosensor for hepatitis B detection.

Despite the availability of effective hepatitis B vaccinations, the hepatitis B virus remains a serious global health concern. It is expected that early detection could aid in initiating therapy before the infection progresses to liver damage. A silicon nanowire rectangular optical waveguide has been demonstrated theoretically to detect the surface antigen of hepatitis B "HBsAg" based on label-free surface sensing using finite-element method-based COMSOL Multiphysics. Different procedural segments of the biomarker detection have been mimicked on the surface of a waveguide as adlayers to investigate the device theoretically. Initially, the parameters of the waveguide have been optimized to provide a large interaction of light and bio-analyte, i.e., to provide high sensitivity. The analyses are first performed at the waveguide level based on the light-analyte interaction. Furthermore, performances of the sensor have been obtained by incorporating this waveguide structure in the sensing arm of the Mach-Zehnder interferometer. The device structure shows ultra-high surface sensitivities such as phase surface sensitivity of 7.03×2πrad/nm and MZI surface sensitivity of 3421.89 µW/nm with an excellent detection limit of 2.92×10-3pg/mm2 for HBsAg detection. The proposed device can measure the HBsAg concentration as low as 0.00973 ng/mL, which is significantly low to detect the infection in an early stage.

Augmentation of sensitivity of FBG strain sensor for biomedical operation: publisher's note.

This publisher's note reports a correction to Appl. Opt.57, 6906 (2018)APOPAI0003-693510.1364/AO.57.006906.

Augmenting performance of a MEMS cantilever-based photonic crystal waveguide for switching applications.

In this paper, a micro-electro-mechanical system-based cantilever is integrated as a line defect on a photonic crystal silicon slab for optical switching applications. The elliptical holes are etched in the photonic crystal waveguide that result in wide transmission bandwidth of 56 nm in comparison to etched circular holes in the structure with a footprint of only ${12.5}\,\,{\unicode{x00B5}{\rm m}} \times {8}\,\,{\unicode{x00B5}{\rm m}}$12.5µm×8µm. The device is optimized for variation in height, the lattice constant, and semi-major and semi-minor axes in the optical range of the S-C-L band. It is shown that the response rise time of the device is 21 µs with very high extinction ratio of 30.4 dB and low insertion loss of 0.32 dB.

Augmentation of sensitivity of FBG strain sensor for biomedical operation.

The performance of a highly sensitive strain sensor based on nonlinear four wave mixing (FWM) using two uniform fiber Bragg gratings (FBGs) is investigated. Strain is measured by the proposed setup with high resolution and precision. It is observed that the wavelength shift induced by very small strain over the FBG is significantly magnified by the higher-order FWM process. The sensitivity is enhanced by a factor of nine based on a wavelength shift of the eighth-order FWM product. Strain sensitivity of 11.23 pm/µÏµ is achieved against initial strain sensitivity of 1.23 pm/µÏµ. The proposed scheme can provide a strain measurement range of about 3500 µÏµ. Application of the proposed setup in the cardiac and respiratory systems is also studied, and the results are found to be reliable and accurate, even if the applied strain on the FBG is of the order of 0.1 µÏµ.

Ultrahigh-resolution interrogation of a fiber Bragg grating sensor based on higher order four-wave mixing.

The performance of a highly sensitive strain sensor based on nonlinear four-wave mixing (FWM) using a fiber Bragg grating (FBG) is investigated. The power change due to the wavelength shift induced by very small strain over the FBG is significantly magnified by a higher order FWM process. Strain sensitivity of 5.547 dBm/µÏµ is achieved and minimum wavelength shift of 2.18×10-6 nm (which corresponds to a strain of 1.80×10-3 µÏµ) is detected with uniform FBG, whereas in case of chirped FBG (CFBG) strain sensitivity of 0.3 dBm/µÏµ with minimum detectable wavelength shift of 4×10-5 nm (which corresponds to a strain of 0.033 µÏµ) is obtained.

Photonic generation of high frequency millimeter-wave and transmission over optical fiber.

A novel technique of photonic generation of millimeter-waves beyond the presently reported 120 GHz and with a wider tunability (∼240 GHz) is proposed and demonstrated through a simulation experiment. The scheme consists of generating 24 times the frequency of a conventional low frequency microwave source using a combination of a LiNbO3 Mach-Zehnder modulator and four-wave mixing in a semiconductor optical amplifier. The filtering of a high frequency sideband and the suppression of a carrier are achieved by incorporating an optical band pass and fiber Bragg grating filters, respectively. Next, the spectral purity of the generated millimeter-wave parameters is evaluated after propagation through a conventional fiber of different lengths by digitally modulating it at 2.5 Gbps and generating an eye diagram. The constraints on the selection of the frequency of the millimeter-wave and length of fiber are discussed. The present method of millimeter-wave generation and distribution will find applications in photonic up/down conversion, phase-array antennas, photonic sensors, radars, and terahertz applications.

Error probability performance of a short-reach multicore fiber optical interconnect transmission system.

A standalone module for rectangular array multicore fiber (MCF)-based optical interconnect (OI) is realized that includes inherent intercore crosstalk and provides space division multiplexed coupling/decoupling of optical power. The module is integrated in a short-reach communication system to provide bit error probability (BEP). Next, a closed-form equation for BEP applicable to MCF OI with intercore crosstalk is derived. For characteristic parameters of the module, results obtained by two approaches agree within 1% for 40 Gbps per channel and predict an error-free transmission of aggregated data rate of 2.5 Tbps through the MCF OI under consideration.