Nanostructured materials are essential for many recent electronic, magnetic and optical devices. Lithography is the most common step used to fabricate organized and well calibrated nanostructures. However, feature sizes less than 200 nm usually require access to deep ultraviolet photolithography, e-beam lithography or soft lithography (nanoimprinting), which are either expensive, have low-throughput or are sensitive to defects. Low-cost, high-throughput and low-defect-density techniques are therefore of interest for the fabrication of nanostructures. In this study, we investigate the potential of displacement Talbot lithography for the fabrication of specific structures of interest within plasmonic and metamaterial research fields. We demonstrate that nanodash arrays and ‘fishnet’-like structures can be fabricated by using a double exposure of two different linear grating phase masks. Feature sizes can be tuned by varying the exposure doses. Such lithography has been used to fabricate metallic ‘fishnet’-like structures using a lift-off technique. This proof of principle paves the way to a low-cost, high-throughput, defect-free and large-scale technique for the fabrication of structures that could be useful for metamaterial and plasmonic metasurfaces. With the development of deep ultraviolet displacement Talbot lithography, the feature dimensions could be pushed lower and used for the fabrication of optical metamaterials in the visible range.
Photonic quasi-crystal structures have been prepared and investigated. Symmetrical patterns were fabricated by
interference lithography in negative tone photoresist and transferred to silicon by reactive ion etching. Theoretical
influences of pattern detail (radius of hole) on the photonic band gap have been studied. Three types of 2D photonic
quasi-crystals have been prepared: 8-fold, 10-fold and 12-fold pattern. Finally, finite-difference time-domain method was
used for theoretically prediction of transmission spectrum for fabricated 12-fold quasi-crystal.
Using Finite-difference time-domain (FDTD) method, the excitation of surface plasmon polaritons (SPP) at the
sinusoidally corrugated metal-dielectric interface was simulated. The sample structure was made by creating onedimension
sinusoidally corrugated dielectric layer on top of metal thin film deposited on dielectric substrate. The
thickness of metal film was simulated in range from 10 to 200 nm. Sinusoidally corrugated grating was modelled with
different pitch and height. Additionally influence of a dielectric layer between grating and metal layer was simulated.
The optical response of the structure was obtained in the regime of wavelength and angle. All simulations were
performed for gold (Au) thin films deposited on glass substrate. Then selected structures were fabricated and measured.
The gold film was thermally evaporated on glass substrate then the one-dimension sinusoidally corrugated dielectric
layer was made in a photoresist using interference lithography.
A wavelength selective add-drop multiplexer utilizing a directional coupler loaded with a first order Bragg grating can be
realized both in fiber and planar technologies. Specifically for the planar case, we detail a systematic design procedure
leading from general assumptions concerning the functional parameters of the device down to geometrical dimensions of
the resulting planar microstructure. The functional parameters include: channel spectral width and channel isolation. The
resulting dimensions are: waveguides etch depth, grating etch depth and lengths of apodized-grating trenches. Grating
apodization profile of the form <i>sin^n</i> is assumed. Design curves are presented, enabling an optimal choice of the
apodization profile's exponent <i>n</i> considering a tradeoff between the required channel isolation and the resulting grating
Gallium nitride is an important material for the contemporary optoelectronics. Large electric band gap, high temperature
resistivity and environmental resistance make GaN interesting also for sensor applications. However, asymmetric
structure of GaN-on-sapphire slab waveguide, grown as a conventional epitaxial heterostructure, poses a problem with
achieving high quality (Q) factor resonators. In this paper, issues related to an asymmetric structure of a waveguide and
theoretical possibilities to achieve high Q-factor resonator in the GaN planar structures are discussed. Three dimensional
(3-D) finite-difference time-domain (FDTD) modeling tools were used. It is shown that the highest Q-factor value of
~ 23 000 is obtained for a symmetrical membrane in L9 (nine points-defect cavity) micro-cavity based on GaN planar
waveguide. In reference to the simulation results, we also discuss the technological issues, i.e. fabrication of photonic
crystal patterns in GaN layers. New approach presented here included deep RIE etching with use of only single masking
layer and conductive polymer usage in e-beam pattering. Possible applications of the micro-resonators for sensor
applications are discussed.
We present results of numerical modeling of photonic crystal (PhC) structures fabricated in gallium nitride (GaN). GaN
is a wide band gap semiconductor material with large refractive index and very good thermal and mechanical properties,
so it is considered a valuable candidate for photonic crystal application - in particular for devices exposed to the harsh
environment. In this paper are considered the ideal 2D PhC with infinite high for a different lattice structures and
calculated optical band gap maps for each. We also calculated air-bridge type slab and "sandwich-type" PhC slabs with
finite height. The dependence of transmission and reflection spectra on holes size, width and profile of "sandwich-type"
PhC slab structure are investigated. All calculations were performed using plane wave expansion method (PWE) and
finite difference time domain method (FDTD).
Depth and profile information of one or two-dimensional photonic crystals can be obtained through
measurements of reflective diffractive patters obtained from the structures and subsequent numerical analysis. The
technique is known as a scatterometry. The method is non-invasive and fast, and competitive to the alternatives of AFM,
SEM etc. In our paper we presented results of investigation 1D photonic crystal fabricated in GaN with period
Λ = 400 nm, fill factor ff = 50% and depth d = 400 nm. Using computer algorithm of Rigorous Coupled Wave Analysis
(RCWA) and measuring diffracted light we extracted the profile parameters of Λ = 420 nm, ff = 51%, d = 400 nm.
Possibility of application of our method for analysis 2D photonic crystals is discussed also.