Near-infrared and visible light dual-mode organic photodetectors.

We report a dual-mode organic photodetector (OPD) that has a trilayer visible light absorber/optical spacer/near-infrared (NIR) light absorber configuration. In the presence of NIR light, photocurrent is produced in the NIR light-absorbing layer due to the trap-assisted charge injection at the organic/cathode interface at a reverse bias. In the presence of visible light, photocurrent is produced in the visible light-absorbing layer, enabled by the trap-assisted charge injection at the anode/organic interface at a forward bias.

Label-free, disposable fiber-optic biosensors for DNA hybridization detection.

A novel and highly sensitive fiber-optic DNA sensor based on a thin-core fiber modal interferometer (TCFMI) is demonstrated by using a layer-by-layer (LbL) self-assembly technology. Poly(ethylenimine) (PEI), poly(acrylic acid) (PAA) and single-stranded DNA (ssDNA) were used for the preparation of a polyelectrolyte multilayer film for DNA detection. The film thickness was measured through a surface profilometer.

Optimization of 3-hole-assisted PMMA optical fiber with double cladding for UV-induced FBG fabrication.

We propose a new hole-assisted polymer optical fiber design to eliminate the influence of dopant diffusion and to increase the UV writing efficiency in fiber Bragg grating inscription. The optical waveguide is formed inside a solid core surrounded by a ring of 3 large air holes in enhanced UV photosensitive PMMA with double-cladding. We determined a map of the single-mode and multi-mode phase transitions using a finite-element- based vectorial optical mode solver.