William J. Wadsworth

Phase-matched third harmonic generation in microstructured fibers

Strong guiding provided by the high-delta microstructured fibers allows for efficient intermodally phase-matched harmonic generation with femtosecond pumping at telecom wavelengths. Visible harmonics are generated in a number of distinct transverse modes of the structure. We present a detailed experimental and theoretical study of the third harmonic generation in such fibers including phase-matching wavelengths, far-field intensity distributions and polarization dependence. Good agreement between the theory and experiment is achieved.

Nonlinear generation of very high-order UV modes in microstructured fibers

Cobweb microstructured optical fibers are often strongly multimode in the visible and near infrared regions. This may lead to a number of intermodally phase-matched nonlinear processes. Here we describe a process of nonlinear generation of very high-order UV modes by pumping such fibers with 100 fs Ti:sapphire pulses. Wavelengths as short as 260 nm are generated through a mechanism distinct from supercontinuum generation.

Scalar modulation instability near zero GVD using a PCF

Scalar modulation instability has been demonstrated in the normal dispersion regime using a PCF leading to efficient upconversion of a red pump to wavelengths throughout the visible.

Simple optical profiling of complex guiding structures

Working with complex guiding structures such as holey fibers requires coupling light into the input face of the structure. We use a simple in vivo technique to determine the scale, morphology, and orientation of the input cleave of the fiber without resorting to separate and more complex methods like optical imaging or scanning electron microscopy. Further, after obtaining the transverse scan of the fiber tip one can precisely position the focal spot anywhere relative to the fiber structure.

Femtosecond pulse propagation dynamics near second zero-dispersion point in photonic crystal fibers

Cross-correlation frequency-resolved optical gating is used to probe the dynamics of a femtosecond pulse in a double-zero dispersion point photonic crystal fiber. Soliton attraction to the second zero-dispersion point and multiple-soliton interaction are observed.

Generation of spectrally distinct third harmonic in photonic crystal fibers

By coupling femtosecond pulses at λ=1.55 microns in a one meter segment of photonic crystal fiber we observe simultaneous generation of third harmonic frequencies from both the fundamental and its self-shifted Raman component, whereas no second harmonic signal is detected.