(2015) Dielectric profile segmentation used to
reduce computation effort of the Fourier-Bessel
mode solving technique.
Optics Express
Authors: Robert C Gauthier, Seyed Hamed Jafari
The Fourier-Bessel space conversion of Maxwell's wave equations into an
eigenvalue formulation is a useful numerical tool for computing the steady states
of cylindrically symmetric dielectric structures. The relative dielectric profile,
inverse (
1
r
) present in wave equations, is split into a constant offset and
corresponding spatially dependent residue and greatly reduces the matrix building
time (and thus computation time) when alternate dielectric configurations are
considered with identical spatial distributions. Such a process significantly speeds
up the theoretical analysis of numerous optical designs, such as index of refraction
sensors, hole infiltration sensors and resonator tuning. The theoretical steps
involved are presented along with examples of the technique applied to the wellknown Bragg resonator and central defect containing hexagonal array.
(2014) Theoretical examination of the slot
channel waveguide configured in a cylindrically
symmetric dielectric ring profile
Optics Communications, Volume 329, Pages 154–162
Authors: Robert C Gauthier, Mohammed A. Alzahrani,, Seyed Hamed Jafari
It has recently been experimentally demonstrated that slot channel waveguides,
configured in cylindrical space, can support high azimuthal order modes similar to
whispering-gallery modes. This paper presents a mode solver based on Maxwell‫׳‬s
vector wave equation for the electric field cast into an eigenvalue problem using a
Fourier–Bessel basis function space. The modal frequencies and field profiles of
the high azimuthal order slot-channel-whispering-gallery (SCWG) modes are
computed for a set of nanometer spaced silicon rings supported by oxide. The
computations show, that in addition to the traditionally observed, lowest order
mode, the structure may support higher order SCWG modes. We complete the
analysis by computing structures response as an ambient medium index of
refraction sensor which achieves over 400 nm per RIU sensitivity.
(2012) Fourier–Bessel analysis of localized
states and photonic bandgaps in 12-fold
photonic quasi-crystals
Journal of the Optical Society of America A, Vol. 29, Issue 11, pp. 2344-2349
Authors: Scott R. Newman and Robert C. Gauthier
A Fourier–Bessel (FB) basis is used to solve two-dimensional (2D) cylindrical
Maxwell’s equations for localized states within dielectric structures that possess
rotational symmetry. The technique is used to determine the wavelengths and
profiles of the stationary states supported by the structure and identify the
bandgaps. 12-fold quasi-crystals for the TE and TM polarizations are analyzed.
Since the FB approach with 2D photonic crystals in this fashion is new, the
accuracy of the results is confirmed using finite-difference time-domain
simulations.
(2012) 2D FDTD simulation of low loss small
angle bend and Y branch configurations in a
photonic crystal waveguide layout with a Mach–
Zehnder device design configuration
Optics Communiations, Volume 285, Issue 7, Pages 1976–1987
Authors: R.C. Gauthier, , S. Newman, K.E. Medri
A technique to produce low loss small angle bends in photonic crystal waveguides
is presented. The technique consists of bridging parallel input and output
waveguide segments with an inclined waveguide region of the same basic design
that has a lateral dielectric shift. Results are presented for waveguides produced by
enlarging the silicon gap along the central line, separating air holes in a square
array photonic crystal for the TE polarization and an operating wavelength of λo =
1.55 μm. This low loss waveguide bending technique is applied to the design of Y
branch and Mach–Zehnder photonic crystal structures. Simulation of the
performance of the dielectric structures is achieved using 2-D FDTD, similar
results are anticipated when applied to 3-D waveguide configurations and for other
photonic crystal layouts.
(2012) Modal analysis and device
considerations of thin high index dielectric
overlay slab waveguides
Applied Optics Vol. 51, Issue 9, pp. 1266-1275
Authors: Robert C. Gauthier, Kristian E. Medri, and Scott R. Newman
The effect of adding a thin high index dielectric overlay layer onto a 3-layer slab
waveguide demonstrates several interesting features that can be exploited in
integrated optical device configurations. A simple modal analysis is employed to
examine the behavior of guided light launched from a 3-layer waveguide structure
then coupled and propagated in the 4-layer overlay region. Modal properties
typically overlooked in conventional slab waveguides are made use of in the
design and theoretical analysis of an MMI device and optical index of refraction
sensor. The optical structure presented here can form the backdrop waveguide
design for more complex and active devices.
(2011) Integrated heaters for the thermal tuning
of Bragg grating filters on silicon-on-insulator
rib waveguides
Microwave and Optical Technology Letters Volume 53, Issue 3, pages 672–676
Authors: Christopher R. Raum*, Robert Gauthier and R. Niall Tait
The thermal tuning of a Bragg grating filter on silicon-on-insulator rib waveguides
has been demonstrated with integrated resistive heaters.The thermal sensitivity is
82 pm/×°C with an efficiency of 4.5 nm/W. A technique for indirectly measuring
the temperature of the integrated heaters is also demonstrated.
(2011) Controlled sacrificial sidewall surface
micromachining for the release of high lengthto-thickness aspect ratio bridges
Journal of Vacuum Science & Technology B , Volume 28, Issue 6
Authors: Christopher R. Raum*, R. Niall Tait and Robert Gauthier
A surfacemicromachining technique for the release of high length-to-thickness
aspect ratio (800:1) bridge structures is presented. During a timed etch release, the
remaining side wall geometry of the sacrificial layer provides intrinsic support for
the structural layer. The micromachining process itself is an equipment limited
procedure in which the wet etchant for the sacrificial layer is replaced in solution
(i.e., in situ) with a supportive photoresist layer. Once in solid form, the photoresist
is removed via ashing in an oxygen plasma. This combination of controlling the
sidewall etch profile of the sacrificial layer and its removal technique results in the
successful release of bridge structures, which are 4000 μm long and 5 μm thick,
with a 2 μm suspension gap.
(2008) Hexagonal array photonic crystal with
photonic quasi-crystal defect inclusion
Optical Materials (Impact Factor: 2.08). 09/2008; 31(1):51-57.
Author(s): Robert C. Gauthier, Khaled Mnaymneh, Scott Ronald Newman, K. E. Medri,
Christopher R. Raum
The central region of a hexagonal array photonic crystal is replaced with the
central region of a higher rotational order photonic quasi-crystal pattern. The
quasi-crystal, with band gaps and defect states now acts as the defect region of the
hexagonal array. For the model system examined, different types of “defect” states
are identified, and the modal properties examined. The higher degree of defect
state control provided by the mixing of photonic crystal types can find applications
in resonator design for laser cavities and WDM as well as assist in the formation of
non-conventional photonic crystal waveguide designs. Results are presented
specifically for the hexagonal array and 12-fold quasi-crystal and can be extended
to other photonic crystal combinations. Hexagonal array photonic crystal with
photonic quasi-crystal defect inclusion - ResearchGate. Available from:
http://www.researchgate.net/publication/248210653_Hexagonal_array_photonic_c
rystal_with_photonic_quasi-crystal_defect_inclusion [accessed Jul 6, 2015].
(2007) Mode localization and band-gap
formation in defect-free photonic quasicrystals
Optics Express Vol. 15, Issue 8, pp. 5089-5099 (2007)
Author(s): Khaled Mnaymneh and Robert C. Gauthier
Defects in photonic crystals are local regions in which the translational symmetry
is broken. The same definition can be applied to photonic quasicrystals except in
this case the symmetry is the 2π/n rotational symmetry, where n is the rotational
fold number. In this context, if no such defects are present, the structure is called
“defect-free”. Even though photonic quasicrystal patterns can be defect-free,
localized modes can still exist in such structures. These modes resemble those of a
central potential that suggests that localization in photonic quasicrystals are
actually “extended” modes of the rotational symmetry. A possible connection is
suggested between these localized modes and short-range dependence of the
photonic band gap (PBG). Such a connection implies a tight-binding description of
PBG formation of photonic quasicrystals ‒ making them more similar to electronic
semiconductors than regular photonic crystals. Physical coupling to these defectfree localized modes is demonstrated.
(2007) FDTD analysis of out-of-plane
propagation in 12-fold photonic quasi-crystals
Optics Communications (Impact Factor: 1.54). 01/2007; 269(2):395-410.
Author(s): Robert C. Gauthier
The out-of-plane propagation characteristics of an infinitely extended 12-fold
photonic quasi-crystal structure is modeled using the FDTD technique. The quasicrystal pattern is designed using the dual beam multiple exposure holographic
lithography system previously reported. Simulations indicate that two types of
mode families are possible; “bandgap guided” and; “index guided”. Results are
presented showing mode profiles; effective index versus propagation constant and
wavelength plots; and modal attenuation due to power leakage. Potential
applications include a new novel micro-structured optical fiber. FDTD analysis of
out-of-plane propagation in 12-fold photonic quasi-crystals - ResearchGate.
Available from:
http://www.researchgate.net/publication/223078186_FDTD_analysis_of_out-ofplane_propagation_in_12-fold_photonic_quasi-crystals [accessed Jul 6, 2015].
(2006) FDTD analysis of 12-fold photonic
quasi-crystal central pattern localized states
Optics Communications Volume 264, Issue 1, 1 August 2006, Pages 78–88
Author(s): Robert C. Gauthier, Khaled Mnaymneh
The TM bandgap features of the 2D 12-fold quasi-crystal are examined based on
the width of the dielectric strip and pattern central symmetry location within the
quasi-crystal. Results indicate that the bandgap properties observed for a particular
fill factor is independent of the rotational symmetry center when the dielectric strip
is wide, and still observable when the strip width is considerably reduced,
confirming the general belief that the bandgap generating properties of the quasicrystal are a local dielectric effect for the lower frequency band. Thin strips are
shown to posses defect states in the bandgap region of the thicker equivalent strips,
defect states analogous to intentionally introduced defect states of translational
symmetric photonic crystals. We explore the mode profiles of the defect state when
the defect is coincidental with the rotational symmetry central pivot point of the
quasi-crystal pattern. In addition we show that the rotational center “defect” may
be used to enhance the optical guidance of light around a 90° bend in a waveguide
implanted in the quasi-crystal.
(2005) Computation of the optical trapping
force using an FDTD based technique.
Optics Express 2005 May 16;13(10):3707-18.
Author(s): Robert C. Gauthier
The computation details related to computing the optical radiation pressure force
on various objects using a 2-D grid FDTD algorithm are presented. The technique
is based on propagating the electric and magnetic fields through the grid and
determining the changes in the optical energy flow with and without the trap
object(s) in the system. Traces displayed indicate that the optical forces and FDTD
predicted object behavior are in agreement with published experiments and also
determined through other computation techniques. We show computation results
for a high and low dielectric disc and thin walled shell. The FDTD technique for
computing the light-particle force interaction may be employed in all regimes
relating particle dimensions to source wavelength. The algorithm presented here
can be easily extended to 3-D and include torque computation algorithms, thus
providing a highly flexible and universally useable computation engine.
(2005) Photonic band gap properties of 12-fold
quasi-crystal determined through FDTD
analysis
Optics Express Vol. 13, Issue 6, pp. 1985-1998 (2005)
Author(s): Robert C. Gauthier and Khaled Mnaymneh
The TM propagation properties of planar 12-fold photonic quasi-crystal patterns
are theoretically examined using FDTD. The patterns examined can be produced
using a dual beam multiple exposure technique. Simulated transmission plots are
shown for various fill factors, dielectric contrast and propagation direction. It is
shown that low index waveguides can be produced using the quasi-crystal photonic
crystal pattern.
(2004) Design of photonic band gap structures
through a dual-beam multiple exposure
technique
Optics Express 04/2005; 13(6):1985-98
Author(s): Robert C. Gauthier, Khaled Mnaymneh
We present a dual-beam multiple exposure technique that can generate complex 2D and 3-D band gap template structures in a photosensitive material. The system
parameters related to the planar interference pattern produced by two laser beams
and reorientation effect of the sample relative to these planes is presented.
Structures such as the 2-D, square and hexagonal arrays of dielectric “rods” and
“holes” and the 3-D, cubic, Yablonovite and other profiles are given. We perform
band gap calculations on these structures when the dielectric contrast has been
increased using a backfill process and discuss techniques for increasing the band
gap by sculpting the dielectric profile. Design of photonic band gap structures
through a dual-beam multiple exposure technique. Available from:
http://www.researchgate.net/publication/253610727_Design_of_photonic_band_ga
p_structures_through_a_dual-beam_multiple_exposure_technique [accessed Jul 6,
2015].
(2004) Production of quasi-crystal template
patterns using a dual beam multiple exposure
technique
Optics Express Vol. 12, Issue 6, pp. 990-1003 (2004)
Author(s): Robert C. Gauthier and Alexei Ivanov
We present a dual beam multiple exposure technique that can generate complex 2D quasi-crystal template structures. The optical system is based on the interference
of two laser beams producing a family of high intensity planes. Controlled
reorientation of a photosensitive sample between exposures results in an exposure
dose, when developed, returns a quasi-crystal pattern. Results are shown in which
quasi-crystal patterns with 8, 10, and 12-fold rotation symmetry are produced in
photoresist. The results of several test runs are shown in which the quasi-crystal
patterns developed in photoresist are subsequently etched into silicon. Based on an
extended application of the dual beam multiple exposure optical system, a potential
technique for producing 3-D quasi-crystal patterns is presented.
(2002) Activation of microcomponents with
light for micro-electro-mechanical systems and
micro-optical-electro-mechanical systems
applications
Applied Optics Vol. 41, Issue 12, pp. 2361-2367 (2002)
Author(s): Robert C. Gauthier, R. Niall Tait, and Mike Ubriaco
We examine the light-activation properties of micrometer-sized gear structures
fabricated with polysilicon surface micromachining techniques. The gears are held
in place on a substrate through a capped anchor post and are free to rotate about the
post. The light-activation technique is modeled on photon radiation pressure, and
the equation of motion of the gear is solved for this activation technique.
Experimental measurements of torque and damping are found to be consistent with
expected results for micrometer-scale devices. Design optimization for optically
actuated microstructures is discussed.
(2001) Optical levitation and trapping of a
micro-optic inclined end-surface cylindrical
spinner.
Applied Optics 2001 Apr 20;40(12):1961-73.
Author(s): Gauthier RC
Cylindrical micro-objects with inclined end surfaces have been observed to be
optically trapped in a focused laser beam and to rotate about the beam's
propagation direction. A simplified vector model is developed that accounts for the
observed effect; the enhanced ray-optics model is used to simulate the behavior of
time evolution for the cylindrical object in the beam. Experimental laser trap
configurations are presented, along with a video image sequence of the cylinder's
precession.
(2001) Optical selection, manipulation,
trapping, and activation of a microgear structure
for applications in micro-opticalelectromechanical systems.
Applied Optics 2001 Feb 20;40(6):930-7.
Author(s): Gauthier RC, Tait RN, Mende H, Pawlowicz C.
The optical processes involved in laser trapping and optical manipulation are
explored theoretically and experimentally as a means of activating a micrometersize gear structure. We modeled the structure by using an enhanced ray-optics
technique, and results indicate that the torque present on the gear can induce the
gear to rotate about the gear-arm plane center with light as the driving energy
source. We confirmed these findings experimentally by using gears manufactured
with conventional semiconductor techniques and from a layer of polyimide. It is
expected that such a simple gear design activated by use of light could lead to an
entire new class of micro-optical-electromechanical systems.
(2001) Automated single-cell sorting system
based on optical trapping.
Journal of Biomedical Optics 2001 Jan;6(1):14-22.
Author(s): Grover SC, Skirtach AG, R.C. Gauthier, Grover CP.
We provide a basis for automated single-cell sorting based on optical trapping and
manipulation using human peripheral blood as a model system. A
counterpropagating dual-beam optical-trapping configuration is shown
theoretically and experimentally to be preferred due to a greater ability to
manipulate cells in three dimensions. Theoretical analysis performed by simulating
the propagation of rays through the region containing an erythrocyte (red blood
cell) divided into numerous elements confirms experimental results showing that a
trapped erythrocyte orients with its longest axis in the direction of propagation of
the beam. The single-cell sorting system includes an image-processing system
using thresholding, background subtraction, and edge-enhancement algorithms,
which allows for the identification of single cells. Erythrocytes have been
identified and manipulated into designated volumes using the automated dualbeam trap. Potential applications of automated single-cell sorting, including the
incorporation of molecular biology techniques, are discussed.
(2000) Theoretical investigation of the optical
trapping properties of a micro-optic cubic glass
structure.
Applied Optics 2000 Jun 20;39(18):3060-70.
Author(s): Robert C. Gauthier, Frangioudakis A.
An enhanced ray optics model is applied to the study of the optical levitation and
trapping properties of a glass cubic object. It is found that for certain highly
symmetric orientations simultaneous force and torque equilibrium can exist in the
lowest-order TEM00 laser beam profile. For analytical purposes, the square
surfaces of the cube are divided into two identical triangular surfaces, and the
interaction of the rays with these triangular surfaces simplifies the computation of
the total force and torque on the cube. The technique developed can easily be
extended to the study of other regular or complex structures.
(1999) Experimental confirmation of the
optical-trapping properties of cylindrical objects
Applied Optics Vol. 38, Issue 22, pp. 4861-4869 (1999)
Author(s): Robert C. Gauthier, Mike Ashman, and Chander P. Grover
A sophisticated modeling program was used recently to predict the trapping and
the manipulation properties of elongated cylindrical objects in the focal region of a
high-intensity laser beam. On the basis of the model, the cylinders should align
their longest diagonal dimension with the propagation axis of the laser beam and
follow the beam when it is displaced transverse to the cylinder’s central axis.
Experimental confirmation of the cylinder’s behavior is presented and confirms the
suitability of the enhanced ray-optics approach to modeling micrometer-scale
objects in optical-trap environments.
(1999) Radiation-pressure-based cylindrically
shaped microactuator capable of smooth,
continuous, reversible, and stepped rotation
Applied Optics Vol. 38, Issue 22, pp. 4850-4860 (1999)
Author(s): Robert C. Gauthier, Mike Ashman, Athanasios Frangioudakis, Howie Mende,
and Shanjun Ma
Long cylindrical objects have been observed to align their central axis with the
propagation axis of the illuminating laser beam through the action of radiationpressure-generated force and torque. A cylindrically shaped microactuator based
on this principle and suitable for micromachine applications is examined
theoretically. When four in-plane laser beams converging at a common point
centered on the cylinder are used, the cylinder can be made to rotate about a pivot
point. In one mode, smooth, continuous, and reversible rotation is possible,
whereas the other cylinder can be step rotated and locked, similar to the operation
of conventional stepping motors. The properties of the device are analyzed based
on obtaining either a constant rotation rate with variable beam power levels or a
quasi-constant rotation rate with constant beam power levels or on using a fixed
beam sequence rate that matches the system parameters and produces smooth or
stepped operation.
(1997) Trapping model for the low-index ringshaped micro-object in a focused, lowest-order
Gaussian laser-beam profile
Journal of the Optical Society of America B Vol. 14, Issue 4, pp. 782-789 (1997)
Author(s): R. C. Gauthier
The trapping properties of a micron-sized, ring-shaped object are examined with an
optical model consisting of ray, wave, electromagnetic, and quantum theoretical
components. Numerically calculated values for the trapping force vector and the
predicted behavior of the ring are in reasonable agreement with reported
experimental observations for this object.
(1997) Theoretical and experimental
considerations for a single-mode fiber-optic
bend-type sensor
Applied Optics Vol. 36, Issue 25, pp. 6264-6273 (1997)
Author(s): R. C. Gauthier, C. Ross
A novel single-mode bend fiber-optic sensing principle is presented. The design
makes use of the translucent protective sheath that encases a typical fiber as a
means of locating the position of a small bend present on an otherwise straight
fiber. We can simultaneously determine bend magnitude by measuring the
reduction in the fiber’s core light. The theoretical model presented and the
experimental results obtained are in excellent agreement, suggesting that a singlepoint sensor system is feasible with the proposed technique.
(1997) Optical trapping: a tool to assist optical
machining
Optics & Laser Technology Volume 29, Issue 7, October 1997, Pages 389–399
Author(s): R. C. Gauthier
Trapping of micro-optical particles in the minimum waist region of highly focused
laser beams has been observed for structures such as spheres, cylinders, rings,
stars, etc, with dimensions in the 1 to 10 μm range. The non-contact, controlled
manipulation and orientation of these objects shows considerable promise for
simplifying the assembly, activation, and possibly repair, of micro-machines. A
simple model is presented and used as the theoretical foundation for discussing the
behaviour of these objects in the beams. The model may also be employed to
predict the behaviour of other object geometries not discussed here. A dual trap
design is discussed which appears suitable for the lifting, orienting and depositing
of micrometre sized particles as required in the area of micro-machining.
(1997) Theoretical investigation of the optical
trapping force and torque on cylindrical microobjects
Journal of the Optical Society of America B Vol. 14, Issue 12, pp. 3323-3333 (1997)
Author(s): R. C. Gauthier
We investigate theoretically the experimentally observed nature of the optical
trapping force present on elongated, cylindrically shaped micro-objects. The
objects chosen have either flat or spherical ends and elongated cylindrical bodies
of various length-to-radii ratios. The trapping force, if present, occurs when the
objects are placed in the focal region of a highly divergent laser beam. Results
indicate that cylindrical objects can be trapped aligned with the laser beam axis.
(1996) Analysis of a birefringent sensor's
dependence on the blocking properties of linear
polarizers and the input laser beam's
polarization state.
Applied Optics 1996 Nov 1;35(31):6271-7
Author(s): R. C. Gauthier
The performance of birefringent fiber-optic sensors is examined theoretically,
based on the extinction properties and leakage of the linear polarizers and the
initial light beam's polarization state. Results indicate that polarizers with leakage
factors as large as 0.01 can still be part of high-quality sensing systems. It is also
shown that in certain input-beam polarization conditions, the presence of a leaky
polarizer in the sensing system acts similarly to a perturbation point on the fiber,
causing polarization mixing and signal degradation.
(1995) Polarization-maintaining distributed
fiber-optic sensor: software elimination of
second-order (ghost) coupling points
Applied Optics Vol. 34, Issue 10, pp. 1744-1748 (1995)
Author(s): R. C. Gauthier
A distributed polarization-maintaining sensor is theoretically analyzed when the
applied perturbations are large enough to generate second-order effects. A software
algorithm has been developed that identifies the real perturbation points and
returns the magnitude of the perturbations distributed along the fiber.
(1995) Optical levitation of spheres: analytical
development and numerical computations of the
force equations
Journal of the Optical Society of America B Vol. 12, Issue 9, pp. 1680-1686 (1995)
Author(s): R. C. Gauthier, S. Wallace
The force that is produced from the momentum change of a stream of photons
incident upon micrometer-sized spheres is developed from a ray-optic model. The
resulting force component expressions, axial and radial with respect to the photon
stream center and incident direction, are in a form that makes them suitable for
computer modeling of the levitation phenomena. Simulated results presented are in
excellent agreement with published experimental observations.