A. Wang

Over 4000 nm Bandwidth of Mid-IR Supercontinuum Generation in sub-centimeter Segments of Highly Nonlinear Tellurite PCFs

We report broad bandwidth, mid-IR supercontinuum generation using a sub-cm (8 mm) length of highly nonlinear tellurite microstructured photonic crystal fiber (PCF). We pump the fiber at telecommunication wavelengths by using 1550 nm, 100 fs pulses of energy E=1.9 nJ. When coupled in the PCF, these pulses result in a supercontinuum (SC) bandwidth of 4080 nm extending from 789 to 4870 nm measured at 20 dBm below the peak spectral power. This bandwidth is comparable or in excess of previously reported spectra for other nonlinear glass fiber formulations despite the significantly shorter fiber length. In addition, besides offering a convenient pump wavelength, short fiber lengths enable smoother SC spectra, lower dispersion, and reduced material absorption at longer wavelengths making the use of this PCF particularly interesting.

Bend loss in all-solid bandgap fibres

Experimental measurements of all-solid photonic bandgap fibres with an array of high-index rods in a low-index background revealed an unexpected variation of bend loss across different bandgaps. This behaviour was confirmed by calculations of photonic band structure, and explained with reference to the differing field distributions of the modes of the cladding rods. Our understanding was confirmed by further experiments, leading to proposals for the improvement of these fibres.

Three-level neodymium fiber laser incorporating photonic bandgap fiber

We report a neodymium fiber laser incorporating an all-solid photonic bandgap fiber to suppress the four-level laser transition 4F3/2-4I11/2. We demonstrate lasing at 907 nm on the three-level transition 4F3/2-4I9/2 when pumping at 808 nm. The maximum slope efficiency obtained was 32% with a threshold pump power of 70 mW.

Solid photonic bandgap fibres and applications

We report on the development of optical fibres which guide light in a solid core using a photonic bandgap effect. The photonic bandgap cladding consists of a two-dimensional array of isolated high-index regions in a lower-index matrix, with a relatively low index contrast. The core is one or more unit cells of the matrix material without the inclusions. The frequency bands for photonic bandgap guidance can be predicted by considering the cut-off frequencies of the guided modes of the high-index rods in the cladding using the weakly-guiding approximation. We demonstrate the basic properties of such fibres and their use as a wavelength-selective element in a fibre laser cavity.

Highly birefringent lamellar core fiber

We report a polarization-maintaining fiber in which the birefringence is due to artificially introduced anisotropy in the core material. The beat length was measured by direct observation at three different wavelengths, giving a shortest result of 85 µm at a wavelength of 543 nm. The measured phase-index birefringence is about one third of that expected, which is explained by diffusion between the core layers, which are each less than 200 nm thick. By taking account of this diffusion, we can accurately model the experimental beat length and differential group delay over a wide wavelength range.

Three-level Neodymium fiber laser incorporating photonic bandgap fiber

We report a neodymium fiber laser incorporating photonic bandgap fiber to suppress the four-level laser transition. Lasing at 907 nm on the three-level transition ⁴F_3/2-⁴I_9/2 is achieved with a slope efficiency of 32%.

Experimental reconstruction of bands in solid core photonic bandgap fibres using acoustic gratings

We present the first characterisation of cladding modes of a low-index contrast all-solid photonic bandgap fiber using an acousto-optic long-period grating. We experimentally measure the relative band diagrams of the cladding, visualise the fields of the cladding modes in the near field, and find both to be in good agreement with simulations. Our measurements and simulations show that the bands of the cladding are very sensitive to actual details of the structure.

All solid photonic bandgap fiber based on an array of oriented rectangular high index rods

We report the fabrication, characterization and modeling of an all-solid photonic bandgap fiber (PBGF) based on an array of oriented rectangular rods. Observed near-field patterns of cladding modes clearly identify the cut-off rod modes at the bandgap edges. The bend losses in this fiber depend on the bend direction, and can be understood by the directional coupling properties of the different rod modes and the modeled density of cladding states.

Applications of Long Period Gratings in Solid Core Photonic Bandgap Fibers

Solid core photonic bandgap fibres are photonic crystal fibres with a solid core surrounded by high index inclusions. The guidance properties of these fibers are very sensitive to the refractive index of the inclusions, making them widely tunable and making them very promising for sensing applications. Combining these fibers with long period gratings unleashes their full potential, enabling narrow band notch filters tunable over hundreds of nm, refractive index sensors with sensitivity comparable to that of surface plasmon resonance sensors, but also the extraction of the full band diagrams of these bandgap fibres.

IR Supercontinuum in Compact Tellurite PCFs

We demonstrate two-octave supercontinuum generation in an 8 cm length of tellurite glass photonic crystal fiber. The high modal confinement and nonlinearity of the tellurite PCF enables the short length of fiber used.