Vinod Kumar Singh

Highly Sensitive Surface Plasmon Resonance Based D-Shaped Photonic Crystal Fiber Refractive Index Sensor

In this article, a D-shaped photonic crystal fiber based surface plasmon resonance sensor is proposed for refractive index sensing. Surface plasmon resonance effect between surface plasmon polariton modes and fiber core modes of the designed D-shaped photonic crystal fiber is used to measure the refractive index of the analyte. By using finite element method, the sensing properties of the proposed sensor are investigated, and a very high average sensitivity of 7700xa0nm/RIU with the resolution of 1.30xa0×xa010−5 RIU is obtained for the analyte of different refractive indices varies from 1.43 to 1.46. In the proposed sensor, the analyte and coating of gold are placed on the plane surface of the photonic crystal fiber, hence there is no necessity of the filling of voids, thus it is gentle to apply and easy to use.

No-core fiber-based highly sensitive optical fiber pH sensor

Abstract. The present work describes the fabrication and characterization of an optical fiber pH sensor using a sol–gel technique. The sensing head configuration is incorporated using a short section of no-core fiber, coated with tetraethyl orthosilicate and spliced at the end of a single mode fiber with a bulge. Different types of indicators (bromophenol blue, cresol red, and chlorophenol red) were used to achieve a wide pH range from 2 to 13. High sensitivities of the fabricated device were found to be 1.02 and −0.93u2009u2009nm/pH for acidic and alkaline solutions, respectively. From the characterization results, it was noted that there is an impact of ionic strength and an effect of the temperature of liquid on the response characteristic, which is an advantage of the existing device over the other pH sensors. The fabricated sensor exhibited good reflection spectrum, indicating a blueshift in resonance wavelength for alkaline solutions and a redshift for acidic solutions.

Experimental and Theoretical Analysis of Connector Offset Optical Fiber Refractive Index Sensor

In this paper, a high sensitive connector offset optical fiber sensor is employed to detect the refractive index of liquid. The configuration chosen for this experiment is formed by lateral core offset fusion splicing of no-core fiber (NCF) between the single mode fibers (SMF) and cladding modes are excited by misalignment. The sensing principle for refractive index detection is based on Mach-Zehnder Interferometer (MZI) principle and the experiment is carried out by immersion of device in NaCl solutions of different refractive indices. Such refractive index sensor exhibits high sensitivity 197.33xa0nm/RIU for the surrounding refractive index variation from 1.333 to 1.380, and the result shows the excellent agreement with theoretical analysis. Compared to other sensors, the proposed device has the potential to provide high sensitivity, ease of fabrication, low cost, compact size, and linear response. Thus, it can be used in many applications such as bio-sensors, chemical sensor, temperature sensor, and pressure sensor.

Enantioselective Tandem Oxidation/Michael-Aldol Approaches to Tetrasubstituted Cyclohexanes.

Enantioselective tandem Michael-aldol and oxidative Michael-aldol approaches have been achieved for the formation of diversely substituted cyclohexanes in total regio-, diastereo- and enantioselective fashion. The presence of nitro, hydroxy and keto groups in the product provides a wide scope for further structural transformations. Furthermore, the utility of the catalytic process is demonstrated in the context of enantioselective formal synthesis of ABT-341, a DPP4 inhibitor.

Silicone rubber-coated highly sensitive optical fiber sensor for temperature measurement

Abstract. A silicone rubber-coated Mach–Zehnder interferometer (MZI) is proposed and applied to temperature measurement. The MZI is fabricated by splicing single mode fiber between a short section of no-core fiber (NCF) and the ultra-abrupt taper region. The sensing length of MZI is coated with liquid silicone rubber to enhance the temperature sensitivity. Here, NCF is used to excite the higher order cladding mode, the ultra-abrupt taper region acts as a optical fiber coupler, and the silicone rubber coating on sensing length is used as solid cladding material instead of liquid. The enhancement of the sensitivity of a device is due to the high refractive index (1.42) and thermo-optic coefficient (−1.4×10−4/°C) of silicone rubber as compared to liquid cladding temperature sensors. The experiment was performed for both coated and uncoated MZI and the results were compared. The MZI exhibits a high temperature sensitivity of 253.75 and 121.26u2009u2009pm/°C for coated and uncoated sensing probes, respectively, in the temperature range from 30°C to 75°C.

Highly Non-linear Simple Designed Solid Core Photonic Crystal Fiber

A highly non-linear solid core photonic crystal fiber (SCPCF) is designed in the present work. Three hexagonal air hole rings in cladding region and four very small air holes are present in a symmetric manner in the core region. By using full vectorial finite element method (FVFEM) with the perfectly matched layer, we study numerically the effective area of modal pattern as well as the nonlinear coefficient of this proposed SCPCF. For this proposed fiber a small modal effective area 5.58 µm2 and a high nonlinear coefficient 21.38 W−1 km−1 are obtained at communication wavelength 1.55 µm for the small air holes in the core with diameter 0.15 µm. This type of SCPCF is useful for different nonlinear applications.