No abstract

Herein, a new polymeric resin for stereolithography (SLA) three-dimensional printing (SLA-3DP) is reported. An ultraviolet (UV) or visible (VIS) light source is critical for SLA printing technology. UV light can be used to manufacture 3D objects in SLA-3DP, but there are significant occupational safety and health issues (particularly for eyes). These issues prevent the widespread use of SLA-3DP at home or in the office. Through the use of VIS light, the safety and health issues can largely be solved, but only non-transparent 3D objects can be manufactured, which prevents the application of 3DP to the production of various common transparent consumer products. For these reasons, we developed a VIS light-curable yet visibly transparent resin for SLA-3DP, which also retains UV curability. The key was to identify the photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (DPTBP). DPTBP was originally designed as a UV photoinitiator, but we found that VIS light irradiation is sufficient to split DPTBP and generate radicals due to its slight VIS light absorption up to 420 nm. The cured resin displays high transparency and beautiful transparent colors by incorporating various dyes; additionally, its mechanical properties are superior to those of commercial resins (Arario 410) and photoinitiators (Irgacure 2959).

We will discuss fabrication of twin core photonic crystal fiber (TC-PCF) using the stack-and-draw method and its application for in-line Mach-Zehnder interferometers. The small difference in the effective indexes of the two core modes leads to interference fringes and the birefringence of the twin cores results in polarization-dependent fringe spacing. The strain sensitivity was negative and wavelength-dependent. A novel intensity-based bend sensor is also demonstrated with bend-induced spatial fringe shift. High air filling fraction of fabricated TC-PCF cladding provides immunity to bend-induced intensity fluctuation.

A highly sensitive temperature sensor based on an all-fiber Mach-Zehnder interferometer using a selectively polymer-filled two-core photonic crystal fiber is experimentally demonstrated. The sensor fiber was made by the manual gluing and subsequent infiltration of polymer; the cladding air holes surrounding one core were selectively filled with a polymer material with a high thermo-optic (TO) coefficient while leaving those of the other core unfilled, and this led to the large TO mismatch between two cores. It was found from measurements that a very high temperature sensitivity of 1.595 nm/°C could be achieved, which was more than two orders of magnitude higher than that of the sensor fiber before the selective filling process.Index Terms-Two-core photonic crystal fiber, interferometer, optical fiber sensor, high temperature sensitivity.

We report on a transverse load sensor with enhanced sensitivity through the use of a birefringent interferometer based on a highly birefringent photonic crystal fiber (HB-PCF). The transverse load sensitivity can be enhanced by using a fabricated HB-PCF having larger air holes on its fast axis. The transverse load sensitivity was measured to be high: approximately 2.17 nm/(N/cm). The temperature-induced undesirable effects can be ignored because transmission outputs of our HB-PCF were stable with the change of the temperature. The sensing probe can be compact because of its high birefringence with the order of 10(-3) and no bending loss.