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Khonina S.N.,Russian Academy of Sciences | Golub I.,Algonquin College
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2013

A simple roadmap is established for the construction of the smallest three-dimensional (3D) isotropic focal spots. It is achieved in a 4Pi configuration by imposing a restriction/condition of equal transverse and longitudinal spot sizes to determine the position of an annular aperture and then optimize its size. The calculations were performed for cylindrically symmetric radial, azimuthal, and circular polarizations for the cases of in-phase and out-of-phase counter-propagating beams as well as when a vortex was added to the beams. A diffraction-limited bright 3D isotropic spot containing solely longitudinal or transverse electric field components is obtained, while the 3D dark spot can be formed from one of two complementary combinations, each containing both transverse and longitudinal field components. © 2013 Optical Society of America.

Khonina S.N.,Russian Academy of Sciences | Golub I.,Algonquin College
Optics Letters | Year: 2011

We show that, by adding a π-phase shift to one-half of a linearly polarized beam, the roles of the transversal and longitudinal field components of the focused beam are interchanged, resulting in better focusing of the longitudinal component in the direction perpendicular to the phase jump line. For this component the scheme produces a spot with FWHM > 15% smaller than a spot generated with either linearly or radially polarized light for any NA. The scheme has a similar advantage when applied to circularly polarized light, and it holds for both a plane wave and a realistic case of a Gaussian incident beam. This technique may find applications when using recording media responsive to the longitudinal field only, particularly in read/write for optical storage where the resolution in one transverse dimension is most important. © 2011 Optical Society of America.

Khonina S.N.,Russian Academy of Sciences | Golub I.,Algonquin College
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2012

We compare different beam combinations for stimulated emission depletion microscopy. The four considered copolarized, mutually symmetric, but complementary write + erase beam combinations are circularly polarized beam + circularly polarized vortex with charge +1 or -1, azimuthally polarized with a vortex + azimuthally polarized, and radially polarized beam + radially polarized with a vortex. The resulting fluorescent spot was calculated for plane incident pump and erase beams, for plane waves with added high NA annular ring apertures, and when both incident beams were optimized with amplitude-phase masks. For all three incident wave cases, the azimuthal polarization combination consistently produces spots 15%-C30% smaller than the commonly used, circularly polarized light combination (the first from above). The two other polarization combinations produce even smaller, of the order of nanometers /0.003λ, fluorescent spots with a caveat of having nonzero erase beam intensity in the center. Nevertheless, these combinations can be advantageous when exploiting PF, i.e., using molecules that respond solely to the longitudinal (or only to transversal) component of the illuminating field. © 2012 Optical Society of America.

Khonina S.N.,Russian Academy of Sciences | Golub I.,Algonquin College
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2012

We compare generation of a dark spot using focusing of beams with azimuthal polarizion, radial polarization with a vortex, and a circular polarization with either a first or second order vortex. By optimization of the amplitudephase pupil, it is ascertained that azimuthal polarization is the most suitable one to obtain the diffraction bounded dark spot per se whose scalar approximation limit has FWHM = 0.29λ. Consequently, for dark spot generation, this polarization plays the role of the radial polarization in creation of the diffraction-limited bright spot. Using azimuthal polarization, it is shown that an amplitude-phase filter allows generation of a subdiffractive dark spot in a prescribed finite area. © 2012 Optical Society of America.

Khonina S.N.,Samara State Aerospace University | Golub I.,Algonquin College
Optics Letters | Year: 2016

We report on a remarkable property of azimuthally (radially) polarized light beams containing a vortex or an orbital angular momentum: upon tight focusing of a first-order vortex beam, the subwavelength spot has a shape of an electric (magnetic) dipole rotating at an optical frequency. For beams with a vortex of order m, the generated pattern is propeller-shaped and rotates at a 1/m fraction of the optical frequency. The applications include petahertz control of electrical or optical conductance between two electrodes or waveguides of two-terminal junctions. © 2016 Optical Society of America.

Chebbi B.,Laurentian University | Golub I.,Algonquin College
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2014

Axicons are known to produce a nearly Bessel beam transverse intensity distribution. It has been previously recognized that linear axicons and logarithmic axicons with a predefined distant depth of field (DOF) and no blocking present a development region characterized by an enlarged central spot size. In this paper, we aim to obtain a better insight on the formation of lateral light distribution in this development region. We also examine the spot size and transverse intensity distribution of the recently developed exponential axicon. We present experiments and detailed nonparaxial numerical simulations for a plane wave passing through these optical elements and show that the lateral intensity distribution they generate differs from that of a Bessel beam for a significant part of their DOF. This anomaly/irregularity in the formation of nondiffracting Bessel beams has to be taken into account in applications of these axicons, such as imaging or optical trapping. © 2014 Optical Society of America.

Golub I.,Algonquin College | Mirtchev T.,Algonquin College | Nuttall J.,Algonquin College | Shaw D.,Algonquin College
Optics Letters | Year: 2012

We report the first observation (to our best knowledge) of a constant intensity, quasi-Bessel/nondiffracting beamin an absorbing medium generated by a novel optical element, "exicon," or exponential intensity axicon. Such absorptioncompensated and diffraction-resistant beams can find applications in illumination, remote sensing, free-space communications, imaging in biological tissues, nonlinear optics, and other situations where absorption and diffraction hinder light propagation. © 2012 Optical Society of America.

Golub I.,Algonquin College | Exir H.,Algonquin College
Optics Letters | Year: 2013

We present a left-right symmetry restoring method, which removes the detrimental birefringence in the singlemode fiber Sagnac interferometer, achieved with the aid of a half waveplate oriented at a specific angle. We show theoretically and demonstrate experimentally that adding a π-shift between clockwise and counterclockwise propagating, horizontally (in fiber loop plane) polarized field components, the Sagnac loop mirror's reflection becomes independent on birefringence of an element placed in the loop. © 2013 Optical Society of America.

Golub I.,Algonquin College | Chebbi B.,Laurentian University | Shaw D.,Algonquin College | Nowacki D.,Algonquin College
Optics Letters | Year: 2010

We show that it is feasible to design and manufacture a refractive logarithmic axicon that generates a quasi-diffraction-free/Bessel beam with nearly constant beam size and intensity over a predetermined range. The novel optical element was characterized with both coherent and incoherent light, and good correspondence with the predicted behavior of the intensity distribution and spot size was found. The energy flow was also found to be nearly constant over most of the designed range. Logarithmic axicons may find applications in situations where large depth of field and uniform axial intensity/energy distributions are important. © 2010 Optical Society of America.

News Article | April 17, 2016

Algonquin College mechanical engineering student Joseph Dupuis - whose off-the-grid cabin went viral last spring - displays an early prototype of his solar tracking device in September 2015. A local entrepreneur who made global headlines for his off-the-grid home last year is getting ready to unveil his latest unconventional solution in sustainable energy.

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