Transparent conductive oxide (TCO) films are proposed as electrode materials for direct current injection optical
microcavity devices. Four types of planar indium-tin-oxide (ITO) clad optical microcavities -1-D photonic crystal
nanobeam, 2-D photonic crystal slab, 3-D photonic crystal and microdisk are designed and analyzed both by perturbation
theory and 3D finite difference time domain (FDTD) analysis. The quality (Q) factors of cavities obtained by
perturbation theory in which imaginary part of the dielectric constant of ITO is introduced as a perturbation agree with
those obtained from FDTD method. Microcavities analyzed in this work still preserve high Q-factor in the presence of
metal clad and would provide an excellent heat sink and efficient carrier injection for electrically-driven continuous-wave,
room-temperature microlasers.
Three-dimensional woodpile photonic crystals with a variety of crystal orientations and surfaces, including (110), (001),
(100) and (010) planes, are fabricated in GaAs and silicon with the multi-directional etching method. The optical
properties of the fabricated woodpile photonic crystals are characterized via reflectance spectra measurement. High
reflectivity is observed in 1200 nm to 1550 nm wavelength, exhibiting a photonic bandgap. The ultra-high-Q
microcavities designed by unit cells size modulation consist of straight dielectric rods only; therefore, they could be
fabricated by the directional etching methods. A high quality factor is expected in the microcavity fabricated by the one-top,
one-side etching approach.
A complete photonic band gap inhibits light propagation in all directions regardless of the polarization. This likely
provides a means of molding light at the level of physical limits. For example, a complete PBG can be applied to
construct nanocavities with ultra-high quality (Q) factor while maintaining a small mode volume, and low-loss
waveguide. These are useful for the applications, such as thresholdless lasers, nonlinear optics and 3D optics. Only
three-dimensional (3D) photonic crystals can possess a complete band gap. However, the application of 3D photonic
crystal is restricted because of the difficulties in precisely fabricating the structures in optical wavelength. Here, we
report the fabrication of large-area woodpile photonic crystal in GaAs at 1.55 μm wavelength by two-directional etching
method without wafer bonding technique. A woodpile with 40×55×2.25 unit cells is fabricated in a two-patterning
process, in which high-resolution electron beam lithography (EBL) defines 2D patterns, and then chemically assisted ion
beam etching (CAIBE) provides high-aspect-ratio, anisotropic and deep GaAs etching at an angle of 45 degree relative
to the wafer surface. The two-directional etching is a simple method to fabricate high-precision woodpile photonic
crystals. The only alignment required in this process is performed by EBL overlay, which has a resolution of less than 30
nm. With our designs of ultra-high-Q nanocavities by unit cell size modulation, we can construct woodpile nanocavities
with active materials, such as epitaxially-grown quantum well (QW) and quantum dot (QD) layers, using the same
fabrication method without wafer bonding process.
The Cu-based interconnect is a major bottleneck for sustaining technological advances in semiconductor integrated
circuits. Matured optics technology may be able to resolve this challenge. Optics can provide high-speed, wavelengthdivision-
multiplexing signals with the capability of interfacing optics with electronics through EO and OE conversion-
directly-modulated laser, external modulator, and photodiode. An optical waveguide is a major building block for optical
interconnects technology. A three-dimensional photonic crystal may provide single-mode, low-loss, group-velocitydispersionless,
and compact waveguides. We report designs of double-heterojunction optical waveguides in a threedimensional
photonic crystal. Compact optical waveguide modes are induced by modulating unit cells onedimensionally
or two-dimensionally. One way to do this is to modulate the unit cell size. A well-type waveguide
structure is formed by modulating the lattice constant of woodpile in one direction. For some 1D double-heterojunction
geometries, light propagation becomes non-dispersive in the space domain, i.e. light is self-collimated along certain
directions within the well plane. Next, two-dimensional unit-cell-modulation is applied to a 3D photonic crystal for
exciting wire-type waveguide modes, for which light propagates along the horizontal or vertical wire. As a result, light
may be guided in the same level or into different levels. The propagation properties, such as group velocity, and
waveguide group velocity dispersion, are also analyzed in this work.
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