We propose a facile approach to fabricate graphene nano-objects (GNOs) using interference lithography (IL) and direct
self-assembly of nanoparticles. Uniformly spaced parallel photoresist (PR) lines and periodic hole arrays are proposed as
an etch mask for producing graphene nanoribbons (GNRs), and graphene nanomesh (GNM), respectively. In a different
experiment, the PR line arrays are transferred to uniform oxide channels, and silica nanoparticle dispersions with an
average size of 10 nm are spun on the patterned surface, leaving a monolayer uniform nanoparticle assembly on the
graphene. Following the particle deposition, the graphene is removed in the narrow spacing between the particles, using
the O2 plasma etch, leaving ordered graphene quantum dot (GQD) arrays. The IL technique and etch process enables
tuning the GNOs dimensions.
A new approach to tunable mid-infrared lasers, an optically pumped, type-II, InGaSb/InAs gain medium with a chirped
distributed feedback grating, has been developed. The chirped grating is patterned using an interferometric lithography
(IL) technique with spherical wave fronts and etched into the top cladding of the laser slab waveguide structure. Because
the period of grating increases gradually laterally, wavelength tuning is implemented by shifting pump stripe to different
positions on the device with different grating periods. Fabry-Perot modes from the cleaved facets are successfully suppressed
by fabricating the grating 6° tilted with respect to facets and adjusting the pump stripe normal to the grating.
Continuous tuning of 30 nm around 3.1 μm with 320 mW single facet output power at 80K and a 1.6 nm FWHM is reported.
The present device is designed in the 3- to 4-μm range which matches a low loss atmospheric transmission window,
and covers an important region of molecular vibration spectra, in particular, the hydrocarbon C-H stretch at ~ 3.3
μm, making it suitable for atmospheric pressure remote gas sensing of industrially important small molecules such as
methane, hydrogen chloride and ammonia.
InAs quantum dots embedded in InGaAs quantum well (DWELL) structures grown by metal-organic chemical-vapor
deposition on nano-patterned GaAs pyramids and planar GaAs (001) substrate are comparatively investigated.
Photoluminescence (PL), PL excitation, and time-resolved PL measurements demonstrate that the DWELL grown on the
GaAs pyramids has a broad QW PL band (FWHM ~ 90 meV) and a better QD emission efficiency than the DWELL
structure grown on the planar GaAs (001) substrate. These properties are attributed to the InGaAs QW with distributed
thickness profile on the faceted GaAs pyramid, which introduces tapered energy band structure and assists the carrier
capture into the QDs. This research provides useful data for further improving the performance of DWELL structures for