Phononic crystals and acoustic metamaterials enable the precise control of elastic properties, even in ranges inaccessible to traditional materials, making them useful for applications ranging from acoustic waveguiding to thermoelectrics. In particular, surface phononic crystals (SPCs) consisting of periodic nanolines on a semi-infinite substrate can be used to generate narrow bandwidth pseudosurface acoustic waves with exquisite sensitivity to the elastic properties of the underlying substrate. Tuning the period of the surface phononic crystal tunes the penetration depth of the pseudosurface wave, and thus selectively probes different depths of layered substrates. In our experiments, we use ultrafast near infrared laser pulses to excite these waves in the hypersonic frequency range by illuminating absorbing metallic nanolines fabricated on top of complex substrates. We probe the nanoscale dynamics launched by our SPCs via pump-probe spectroscopy where we monitor the diffraction of ultrafast pulses of extreme ultraviolet light generated via tabletop high harmonic generation. We then extract the mechanical properties of the substrate by comparing our measurements to quantitative finite element analysis. Utilizing this technique, we characterize the effective elastic and thermal transport properties of 3D periodic semiconductor metalattices.
ZnSe and other zinc chalcogenide semiconductor materials can be doped with divalent transition metal ions to create a
mid-IR laser gain medium with active function in the wavelength range 2 - 5 microns and potentially beyond using
frequency conversion. As a step towards fiberized laser devices, we have manufactured ZnSe semiconductor fiber
waveguides with low (less than 1dB/cm at 1550nm) optical losses, as well as more complex ternary alloys with
ZnSxSe(1-x) stoichiometry to potentially allow for annular heterostructures with effective and low order mode corecladding
Integration of semiconductor and metal structures into optical fibers to enable fusion of semiconductor optoelectronic
function with glass optical fibers is discussed. A chemical vapor deposition (CVD)-like process, adapted for high pressure
flow within microstructured optical fibers allows for flexible fabrication of such structures. Integration of semiconductor
optoelectronic devices such as lasers, detectors, and modulators into fibers may now become possible.
We have recently fabricated continuous semiconducting micro and nanowires within the empty spaces of highly ordered microstructured (e.g., photonic crystal or holey) optical fibers (MOF's). These systems contain the highest aspect ratio semiconductor micro- and nanowires yet produced by any method: centimeters long and ~100 nm in diameter. These structures combine the flexible light guiding capabilities of an optical fiber with the electronic and optical functionalities of semiconductors and have many potential applications for in-fiber sensing, including in-fiber detection, modulation, and generation of light.
Conference Committee Involvement (2)
Integrated Optics: Devices, Materials, and Technologies XIII
26 January 2009 | San Jose, California, United States
Integrated Optics: Devices, Materials, and Technologies XII
21 January 2008 | San Jose, California, United States