Weijun Tong

Low-loss all-solid photonic bandgap fiber

We report the fabrication and characterization of a new type all-solid photonic bandgap fiber. By introducing an index depressed layer around the high-index rod in the unit cell of photonic crystal cladding, transmission loss as low as 2 dB/km within the first bandgap is realized for the all-solid photonic bandgap fiber with a bandwidth of over 700 nm. The bend loss experiment shows that the photonic bandgap fiber is much less bend sensitive than single-mode fiber.

Design of All-Solid Bandgap Fiber With Improved Confinement and Bend Losses

We propose a new design of low-contrast all-solid bandgap fiber with low confinement and bend losses within low-order bandgaps. By introducing an index depressed layer around the high index rod in fiber cladding, we theoretically predict that the confinement loss of the proposed all-solid bandgap fiber would be significantly improved. Due to the enlarged index mismatch of the guided core mode and the edge of the bandgaps, the critical bend radius of the proposed fiber is remarkably reduced

Visible Supercontinuum Generation With Sub-Nanosecond 532-nm Pulses in All-Solid Photonic Bandgap Fiber

An all-solid photonic bandgap fiber with the first bandgap from 450 to 900 nm was designed for visible supercontinuum generation. Sub-nanosecond pulses from a 532-nm microchip laser were launched into this fiber, and the supercontinuum from 532 to 900 nm was obtained. The bright single-mode visible light beam was observed, with the output power of 30 mW.

Silica-Based Nanostructure Core Fiber

We report the fabrication and characterization of a new type of silica-based all-solid fiber with a two-dimensional (2-D) nanostructure core. The nanostructure core fiber (NCF) was formed by a 2-D array of high-index rods of sub wavelength dimensions. The NCFs attenuation of as low as 3.5 dB/km at 1550 nm has been obtained experimentally. We also measured the chromatic dispersion, differential group delay, and polarization-dependent loss of the NCF. Higher macro-and microbending losses compared with that of the single-mode fiber due to the reduced index difference has been observed experimentally, and this result suggests that NCF is potentially useful for curvature and strain sensing applications.

Silica-based Low Loss All-solid Bandgap Fiber

We report the fabrication of a new designed all- solid bandgap fiber. The low loss transmission (as low as 2 dB/km at 1310 nm) has been realized with a bandwidth of over 700 nm.

Intermodal Cherenkov Radiation Between Two Transmission Bandgaps in an All-Solid PBG Fiber

We demonstrate nonlinear propagation of femtosecond laser pulses in an all-solid photonic bandgap fiber. A supercontinuum from 560 to 1470 nm is generated from this fiber with an average power of 2 W. Spectral broadening not only occurs within the first bandgap, where the pump laser lies, but it also emits a phase-matched dispersive wave in a different propagation mode within the adjacent bandgap. Energy transfers across the intergap attenuation region with simultaneous mode conversion in the nonlinear process. The intermodal Cherenkov radiation generated across two bandgaps by the perturbed Raman solitons can enrich the nonlinear process in the all-solid photonic bandgap fiber.

Nanostructure Core Fiber With Enhanced Performances: Design, Fabrication and Devices

We report a new type of silica-based all-solid fiber with a 2-D nanostructure core. The nanostructure core fiber (NCF) is formed by a 2-D array of high-index rods of sub-wavelength dimensions. We theoretically study the birefringence property of such fibers over a large wavelength range. Large-mode-area (LMA) structure with a typical high birefringence in the order of 10-4 can be easily realized. The attenuation of the fabricated NCF is as low as 3.5 dB/km at 1550 nm. Higher macro- and micro-bending losses compared with those of the single-mode fiber (SMF) due to the reduced index difference have been observed experimentally, which suggests that the NCF is potentially useful for curvature and strain sensing applications. A fiber Bragg grating (FBG) inscribed in such a novel fiber is side-polished to make use of its evanescent field for refractive index sensing. The refractive index sensitivity obtained is one order of magnitude higher than that of the side-polished FBG in SMF, while the temperature and strain performances are comparable with those of the SMF-based FBG.

Photonic Bandgap Fiber for Infiltration-Free Refractive-Index Sensing

We report a novel photonic bandgap sensor, comprising a D-shaped fiber fabricated via side polishing. It takes advantage of measurand-elicited refractive-index profile changes upon exposure of its side-polished region to an ambient liquid. The bandgap shift can be induced by perturbations in close proximity to the fiber core, such as the change of refractive index in the surrounding. The side-polished all-solid photonic bandgap fiber utilized offers an infiltration-free sensing mechanism, which eliminates difficult air-hole infiltration and evacuation processes experienced by most photonic crystal fiber-based index sensors. Experimental results demonstrated the repeatability and linearity in refractive-index sensing from 1.31 to 1.43 with a sensitivity of 10 -5 refractive-index units (RIUs). Additional study was also conducted to identify the significance of polishing depths in relation to the sensor performance.