Efficient inscription of Bragg gratings in As2S3 fibers using near bandgap light.

Efficient inscription of Fiber Bragg gratings (FBGs) in single-mode, thin cladding As(2)S(3) fibers is demonstrated by using near bandgap light at 532 nm. The FBGs with the reflectivity of over 80% can be induced in only 80-90 s, substantially faster than in previous reports. The dynamics of the grating growth are investigated in the photosensitivity process, showing a fast blue shift of the Bragg wavelength and then a somewhat slower red shift. The aging of the grating after fabrication is also reported, indicating a 37% decay of the grating strength.

Reconfigurable photonic crystal waveguides created by selective liquid infiltration.

We experimentally demonstrate reconfigurable photonic crystal waveguides created directly by infiltrating high refractive index (n≈2.01) liquids into selected air holes of a two-dimensional hexagonal periodic lattice in silicon. The resulting effective index contrast is large enough that a single row of infiltrated holes enables light propagation at near-infrared wavelengths. We include a detailed comparison between modeling and experimental results of single line defect waveguides and show how our infiltration procedure is reversible and repeatable. We achieve infiltration accuracy down to the single air hole level and demonstrate control on the volume of liquid infused into the holes by simply changing the infiltration velocity. This method is promising for achieving a wide range of targeted optical functionalities on a "blank" photonic crystal membrane that can be reconfigured on demand.

Liquid crystal dynamics in a photonic crystal cavity created by selective microfluidic infiltration.

A microfluidic double heterostructure cavity is created in a silicon planar photonic crystal waveguide by selective infiltration of a liquid crystal. The spectral evolution of the cavity resonances probed by evanescent coupling reveals that the liquid crystal evaporates, even at room temperature, despite its relatively low vapor pressure of 5 × 10(-3) Pa. We explore the infiltration and evaporation dynamics of the liquid crystal within the cavity using a Fabry-Perot model that accounts for the joint effects of liquid volume reduction and cavity length variation due to liquid evaporation. While discussing how the pattern of the infiltrated liquid can be optimized to restrict evaporation, we find that the experimental behavior is consistent with basic microfluidic relations considering the small volumes of liquids and large surface areas present in our structure.

Enhanced Kerr nonlinearity in sub-wavelength diameter As(2)Se(3) chalcogenide fiber tapers.

We experimentally demonstrate enhanced Kerr nonlinear effects in highly nonlinear As(2)Se(3) chalcogenide fiber tapered down to sub-wavelength waist diameter of 1.2 mum. Based on self phase modulation measurements, we infer an enhanced nonlinearity of 68 W(-1)m(-1). This is 62,000 times larger than in standard silica singlemode fiber, owing to the 500 times larger n(2) and almost 125 times smaller effective mode area. We also consider the potential to exploit the modified dispersion in these tapers for ultra-low threshold supercontinuum generation.

Long period grating resonances in photonic bandgap fiber.

We demonstrate the formation of stress-induced long period gratings (LPGs) in fluid-filled photonic bandgap fiber (PBGF). Based on our experimental results, simulations, and theoretical understanding of LPGs, we identify coupling to a guided LP(11)-like mode of the core and lossy LP1x-like modes of cladding microstructure for a single grating period. The periodic modal properties of PBGFs allow for coupling to the same mode at multiple wavelengths without a dispersion turning point. Simulations identify inherent differences in the modal structure of even and odd bands.

Widely tunable, acousto-optic resonances in Chalcogenide As2Se3 fiber.

We report for the first time acousto-optical transmission resonances in a non-silica fiber. The resonances, generated in highly nonlinear, single-mode Chalcogenide (As2Se3) fiber, are up to -9 dB deep and tunable over 235 nm around 1450 nm by varying the frequency of an acoustic wave propagating in the fiber, creating a variable period long period grating. The material properties of Chalcogenide modify the acoustic wave propagation leading to a different frequency range of operation when compared to Silica fiber. A tunable resonant structure in this medium opens up possibilities for all-optical processing and mid-IR applications.

Tuning properties of long period gratings in photonic bandgap fibers.

We investigate the thermal tuning properties of long period gratings (LPGs) in a fluid-filled photonic bandgap fiber (PBGF). The combination of strong, resonant waveguide dispersion, characteristic of all PBGF modes, and the large thermo-optic coefficients of fluids yields highly tunable grating resonances. We measure grating resonances in three transmission bands with large tuning coefficients of up to -1.58 nm/degrees C, which match numerical results. We derive an analytic model for the PBGF LPG tuning coefficient to show how it depends on both the shift of the transmission bands and the dispersion of the coupled modes.