Electrically tunable ring resonators incorporating nematic liquid crystals as cladding layers

We have demonstrated electrical tuning in ring resonators fabricated from silicon-on-insulator wafers by incorporating nematic liquid crystals (NLCs) as the waveguide top and side cladding material. Photolithographically defined electrodes aligned around the ring resonator were used to control the orientation of the NLCs to modulate the cladding refractive index and, hence, the resonant wavelengths of the ring resonator

Electrically tuned photonic crystal/liquid crystal laser

The emission wavelength of ultra-small photonic crystal laser is electrically controlled with an applied gate voltage. High quality factor porous-cavity laser design enables strong interaction between strong optical fields and infiltrated liquid crystals

Optically triggered Q-switched photonic crystal laser

An optically triggered liquid crystal infiltrated Q-switched photonic crystal laser is demonstrated. A photonic crystal laser cavity was designed and fabricated to support two orthogonally polarized high-Q cavity modes after liquid crystal infiltration. By controlling the liquid crystal orientation via a layer of photoaddressable polymer and a writing laser, the photonic crystal lasing mode can be reversibly switched between the two modes which also switches the laser’s emission polarization and wavelength. The creation of the Q-switched laser demonstrates the benefits of customizing photonic crystal cavities to maximally synergize with an infiltrated material and illustrates the potential of integrating semiconductor nanophotonics with optical materials

Electrically tuned photonic crystal/liquid crystal laser

The emission wavelength of ultra-small photonic crystal laser is electrically controlled with an applied gate voltage. High quality factor porous-cavity laser design enables strong interaction between strong optical fields and infiltrated liquid crystals

Fluidic and Polymeric Integration and Functionalization of Optical Microresonators

Optical resonators are structures that spatially confine and temporally store light. The use of such resonators continues to permeate throughout society as improvements in their design and fabrication qualify them to fulfill an ever-increasing array of technological and scientific applications. Traditionally, resonators have primarily been used in lasers and as filters, and more recently have been utilized in other areas including chemical sensing, spontaneous emission modulation, and quantum electrodynamics experiments. In many of these applications, the functionalities of the resonators are solely derived from the geometry and material composition of the resonators themselves. The central theme of this thesis is the investigation of further increasing a resonator's functionality through its integration with fluidic and polymeric materials. The thesis begins with an investigation of integrating silicon ring resonators with electro-optic polymer and liquid crystal in an effort to tune the resonators' resonant wavelengths. Although the electro-optic polymer efforts are a failure, we are able to electrically tune the rings' resonances using electrodes and the reorientation of liquid crystal surrounding the resonators. We then take the knowledge and experience acquired from these experiments and pursue the functionalization of photonic crystal laser resonators, a relatively new class of microresonators constructed from a thin slab of InGaAsP quantum well material with a periodic array of holes etched through the slab. To this end, we first infiltrate the porous resonators with liquid crystal and construct liquid crystal cells around the devices. We are then able to tune the lasing wavelengths by reorienting the liquid crystal with a voltage applied across the cell. Next, we devise a new photonic crystal cavity designed to optimally interact with infiltrated birefringent materials, by supporting two orthogonally polarized high-Q modes. Again, we infiltrate the cavity with liquid crystal, but this time optically control the liquid crystal orientation with a photoaddressable polymer film. By doing so we are able to realize a fundamentally new laser tuning method by reversibly Q-switching a resonator's lasing mode between the two cavity modes and thereby control the laser's emission wavelength and polarization. The successful fluidic and polymeric integration with optical resonators presented in this thesis demonstrates some of the possible synergies that can be obtained with such integration and suggests that further enhancements in resonator functionality is possible.</p

Negative Differential Resistance in Electrochemically Self-assembled Layered Nanostructures

Resonant tunneling devices are used for ultrahigh-speed applications. In this work, tunnel junctions based on copper metal (Cu) and cuprous oxide (Cu 2O) are electrochemically self-assembled from aqueous solution in an oscillating system. The Cu 2O layer thickness (L) is tuned from 0.8 to 2.8 nm by simply changing the applied current density. The layered structures show sharp negative differential resistance (NDR) signatures at room temperature in perpendicular transport measurements, and the NDR maximum shifts to higher bias with a 1/L 2 dependence as the Cu 2O layer is made thinner. The results are consistent with resonant tunneling from Cu into hole states in the valence band of quantum-confined Cu 2O through thin space - charge regions on each side of the Cu 2O