figshare

United Kingdom

380 Works

Observation of discrete quadratic surface solitons

Georgios A. Siviloglou, Konstantinos G. Makris, Robert Iwanow, Roland Schiek, Demetrios N. Christodoulides, George I. Stegeman, Yoohong Min & Wolfgang Sohler
We report the first observation of discrete quadratic surface solitons in self-focusing and defocusing periodically poled lithium niobate waveguide arrays. By operating on either side of the phase-matching condition and using the cascading nonlinearity, both in-phase and staggered discrete surface solitons were observed. This represents the first experimental demonstration of staggered/gap surface solitons at the interface of a semi-infinite nonlinear lattice. The experimental results were found to be in good agreement with theory.

Observation of discrete quadratic surface solitons

Georgios A. Siviloglou, Konstantinos G. Makris, Robert Iwanow, Roland Schiek, Demetrios N. Christodoulides, George I. Stegeman, Yoohong Min & Wolfgang Sohler
We report the first observation of discrete quadratic surface solitons in self-focusing and defocusing periodically poled lithium niobate waveguide arrays. By operating on either side of the phase-matching condition and using the cascading nonlinearity, both in-phase and staggered discrete surface solitons were observed. This represents the first experimental demonstration of staggered/gap surface solitons at the interface of a semi-infinite nonlinear lattice. The experimental results were found to be in good agreement with theory.

Adaptive optics scanning laser ophthalmoscope for stabilized retinal imaging

Daniel X. Hammer, R. Daniel Ferguson, Chad E. Bigelow, Nicusor V. Iftimia, Teoman E. Ustun & Stephen A. Burns
A retinal imaging instrument that integrates adaptive optics (AO), scanning laser ophthalmoscopy (SLO), and retinal tracking components was built and tested. The system uses a Hartmann-Shack wave-front sensor (HS-WS) and MEMS-based deformable mirror (DM) for AO-correction of high-resolution, confocal SLO images. The system includes a wide-field line-scanning laser ophthalmoscope for easy orientation of the high-magnification SLO raster. The AO system corrected ocular aberrations to <0.1 μm RMS wave-front error. An active retinal tracking with custom...

Adaptive optics scanning laser ophthalmoscope for stabilized retinal imaging

Daniel X. Hammer, R. Daniel Ferguson, Chad E. Bigelow, Nicusor V. Iftimia, Teoman E. Ustun & Stephen A. Burns
A retinal imaging instrument that integrates adaptive optics (AO), scanning laser ophthalmoscopy (SLO), and retinal tracking components was built and tested. The system uses a Hartmann-Shack wave-front sensor (HS-WS) and MEMS-based deformable mirror (DM) for AO-correction of high-resolution, confocal SLO images. The system includes a wide-field line-scanning laser ophthalmoscope for easy orientation of the high-magnification SLO raster. The AO system corrected ocular aberrations to <0.1 μm RMS wave-front error. An active retinal tracking with custom...

Orbital angular momentum transfer in helical Mathieu beams

Carlos Lóxpez-Mariscal, Julio C. Gutiérrez-Vega, Graham Milne & Kishan Dholakia
We observe the transfer of orbital angular momentum to trapped particles in the azimuthally asymmetric transverse intensity distribution of a helical Mathieu beam. The average rotation rate, instantaneous angular displacement and terminal velocity of the trapped particles are measured experimentally. The angular dependence of these parameters is found to be in good agreement with the variation of the optical gradient force, the transfer of OAM from the wavefield and the Stokes drag force.

Orbital angular momentum transfer in helical Mathieu beams

Carlos Lóxpez-Mariscal, Julio C. Gutiérrez-Vega, Graham Milne & Kishan Dholakia
We observe the transfer of orbital angular momentum to trapped particles in the azimuthally asymmetric transverse intensity distribution of a helical Mathieu beam. The average rotation rate, instantaneous angular displacement and terminal velocity of the trapped particles are measured experimentally. The angular dependence of these parameters is found to be in good agreement with the variation of the optical gradient force, the transfer of OAM from the wavefield and the Stokes drag force.

Orbital angular momentum transfer in helical Mathieu beams

Carlos López-Mariscal, Julio C. Gutiérrez-Vega, Graham Milne & Kishan Dholakia
We observe the transfer of orbital angular momentum to trapped particles in the azimuthally asymmetric transverse intensity distribution of a helical Mathieu beam. The average rotation rate, instantaneous angular displacement and terminal velocity of the trapped particles are measured experimentally. The angular dependence of these parameters is found to be in good agreement with the variation of the optical gradient force, the transfer of OAM from the wavefield and the Stokes drag force.

Orbital angular momentum transfer in helical Mathieu beams

Carlos López-Mariscal, Julio C. Gutiérrez-Vega, Graham Milne & Kishan Dholakia
We observe the transfer of orbital angular momentum to trapped particles in the azimuthally asymmetric transverse intensity distribution of a helical Mathieu beam. The average rotation rate, instantaneous angular displacement and terminal velocity of the trapped particles are measured experimentally. The angular dependence of these parameters is found to be in good agreement with the variation of the optical gradient force, the transfer of OAM from the wavefield and the Stokes drag force.

Cubic interpolated propagation scheme in numerical analysis of lightwave and optical force

Daisuke Barada, Takashi Fukuda, Masahide Itoh & Toyohiko Yatagai
A novel technique using a cubic interpolated propagation or constrained interpolation profile (CIP) scheme for numerical analysis of light propagation in dielectric media is proposed. One- and two-dimensional calculations of the propagation of short Gaussian pulses are performed. The validity of the proposed technique is confirmed by applying it to the examination of the reflection from dielectric media. Using the CIP scheme, the optical force acted upon a dielectric disc is also calculated and it...

Cubic interpolated propagation scheme in numerical analysis of lightwave and optical force

Daisuke Barada, Takashi Fukuda, Masahide Itoh & Toyohiko Yatagai
A novel technique using a cubic interpolated propagation or constrained interpolation profile (CIP) scheme for numerical analysis of light propagation in dielectric media is proposed. One- and two-dimensional calculations of the propagation of short Gaussian pulses are performed. The validity of the proposed technique is confirmed by applying it to the examination of the reflection from dielectric media. Using the CIP scheme, the optical force acted upon a dielectric disc is also calculated and it...

Visualization of optical binding of microparticles using a femtosecond fiber optical trap

N. K. Metzger, E. M. Wright, W. Sibbett & K. Dholakia
At the microscopic level, light-matter interactions can organize colloidal matter via a process known as optical binding. Optical binding refers to the creation of arrays of microparticles formed in the presence of laser fields, the inter-particle spacing being determined by the refocusing and/or scattering of the laser fields by the microparticles. In this paper we investigate one-dimensional optically bound arrays of microparticles using a femtosecond dual-beam optical fiber trap, and develop a means to visualize...

Visualization of optical binding of microparticles using a femtosecond fiber optical trap

N. K. Metzger, E. M. Wright, W. Sibbett & K. Dholakia
At the microscopic level, light-matter interactions can organize colloidal matter via a process known as optical binding. Optical binding refers to the creation of arrays of microparticles formed in the presence of laser fields, the inter-particle spacing being determined by the refocusing and/or scattering of the laser fields by the microparticles. In this paper we investigate one-dimensional optically bound arrays of microparticles using a femtosecond dual-beam optical fiber trap, and develop a means to visualize...

Raman-like light scattering from acoustic phonons in photonic crystal fiber

P. Dainese, P. St.J. Russell, G. S. Wiederhecker, N. Joly, H. L. Fragnito, V. Laude & A. Khelif
Raman and Brillouin scattering are normally quite distinct processes that take place when light is resonantly scattered by, respectively, optical and acoustic phonons. We show how few-GHz acoustic phonons acquire many of the same characteristics as optical phonons when they are tightly trapped, transversely and close to modal cut-off, inside the wavelength-scale core of an air-glass photonic crystal fiber (PCF). The result is an optical scattering effect that closely resembles Raman scattering, though at much...

Raman-like light scattering from acoustic phonons in photonic crystal fiber

P. Dainese, P. St.J. Russell, G. S. Wiederhecker, N. Joly, H. L. Fragnito, V. Laude & A. Khelif
Raman and Brillouin scattering are normally quite distinct processes that take place when light is resonantly scattered by, respectively, optical and acoustic phonons. We show how few-GHz acoustic phonons acquire many of the same characteristics as optical phonons when they are tightly trapped, transversely and close to modal cut-off, inside the wavelength-scale core of an air-glass photonic crystal fiber (PCF). The result is an optical scattering effect that closely resembles Raman scattering, though at much...

Variable focus dielectric liquid droplet lens

Chih-Cheng Cheng, C. Alex Chang & J. Andrew Yeh
A liquid crystal droplet lens driven by the dielectrophoresis (DEP) force was demonstrated. The liquid crystal droplet lens was deformed by the DEP forces under non-uniform AC electric fields. Focal length, hysteresis and electrode design were studied. The focal length varied from 1.6mm to 2.6mm in the range of 0-200V at 1 kHz for electrode spacing of 50μm; that is, the tuning ratio of the focal length was about 60% in maximum. The hysteresis of...

Variable focus dielectric liquid droplet lens

Chih-Cheng Cheng, C. Alex Chang & J. Andrew Yeh
A liquid crystal droplet lens driven by the dielectrophoresis (DEP) force was demonstrated. The liquid crystal droplet lens was deformed by the DEP forces under non-uniform AC electric fields. Focal length, hysteresis and electrode design were studied. The focal length varied from 1.6mm to 2.6mm in the range of 0-200V at 1 kHz for electrode spacing of 50μm; that is, the tuning ratio of the focal length was about 60% in maximum. The hysteresis of...

Holographic optical trapping of aerosol droplets

D. R. Burnham & D. McGloin
We demonstrate the use of holographic optical tweezers for trapping particles in air, specifically aerosol droplets. We show the trapping and manipulation of arrays of liquid aerosols as well as the controlled coagulation of two or more droplets. We discuss the ability of spatial light modulators to manipulate airborne droplets in real time as well as highlight the difficulties associated with loading and trapping particles in such an environment. We conclude with a discussion of...

Holographic optical trapping of aerosol droplets

D. R. Burnham & D. McGloin
We demonstrate the use of holographic optical tweezers for trapping particles in air, specifically aerosol droplets. We show the trapping and manipulation of arrays of liquid aerosols as well as the controlled coagulation of two or more droplets. We discuss the ability of spatial light modulators to manipulate airborne droplets in real time as well as highlight the difficulties associated with loading and trapping particles in such an environment. We conclude with a discussion of...

Holographic optical trapping of aerosol droplets

D. R. Burnham & D. McGloin
We demonstrate the use of holographic optical tweezers for trapping particles in air, specifically aerosol droplets. We show the trapping and manipulation of arrays of liquid aerosols as well as the controlled coagulation of two or more droplets. We discuss the ability of spatial light modulators to manipulate airborne droplets in real time as well as highlight the difficulties associated with loading and trapping particles in such an environment. We conclude with a discussion of...

Holographic optical trapping of aerosol droplets

D. R. Burnham & D. McGloin
We demonstrate the use of holographic optical tweezers for trapping particles in air, specifically aerosol droplets. We show the trapping and manipulation of arrays of liquid aerosols as well as the controlled coagulation of two or more droplets. We discuss the ability of spatial light modulators to manipulate airborne droplets in real time as well as highlight the difficulties associated with loading and trapping particles in such an environment. We conclude with a discussion of...

Dynamics of ultimate spectral narrowing in a semiconductor fiber-grating laser with an intra-cavity saturable absorber

Irina A. Kostko & Raman Kashyap
The ultimate spectrum-narrowing and side-mode suppression due to the presence of a saturable absorber in an external cavity of a fiber Bragg grating semiconductor laser is numerically simulated. The proposed algorithm describes an effect of absorption bleaching in a saturable absorber using earlier measurements and shows the evolution of a dynamic grating in the laser cavity. The simulations confirm for the first time an empirical theory of spectral line narrowing in a laser with an...

Dynamics of ultimate spectral narrowing in a semiconductor fiber-grating laser with an intra-cavity saturable absorber

Irina A. Kostko & Raman Kashyap
The ultimate spectrum-narrowing and side-mode suppression due to the presence of a saturable absorber in an external cavity of a fiber Bragg grating semiconductor laser is numerically simulated. The proposed algorithm describes an effect of absorption bleaching in a saturable absorber using earlier measurements and shows the evolution of a dynamic grating in the laser cavity. The simulations confirm for the first time an empirical theory of spectral line narrowing in a laser with an...

Adiabatic bends in surface plasmon polariton band gap structures

Ilya P. Radko, Thomas Søndergaard & Sergey I. Bozhevolnyi
Propagation and interaction of surface plasmon polaritons (SPPs) excited in the wavelength range 700–860 nm with periodic triangular arrays of gold bumps placed on gold film surfaces are investigated using a collection near-field microscope. We observe the inhibition of SPP propagation into the arrays within a certain wavelength range, i.e., the band gap (BG) effect. We demonstrate also the SPP propagation along a 30° bent channel obtained by an adiabatic rotation of the periodic array...

Femtosecond electron pulse gating using surface plasmons

S. E. Irvine & A. Y. Elezzabi
We present a theoretical investigation of a novel all-optical method for electron beam gating via ponderomotive surface plasmon (SP) interaction. Using femtosecond optical pulses, large electric field gradient SP waves are launched on the surface of a metal film and selectively gate an external electron beam. It is shown that this method can generate electron pulses having similar durations as the laser pulse. The ultrashort electron packets are highly directional and examination of their spatial...

Femtosecond electron pulse gating using surface plasmons

S. E. Irvine & A. Y. Elezzabi
We present a theoretical investigation of a novel all-optical method for electron beam gating via ponderomotive surface plasmon (SP) interaction. Using femtosecond optical pulses, large electric field gradient SP waves are launched on the surface of a metal film and selectively gate an external electron beam. It is shown that this method can generate electron pulses having similar durations as the laser pulse. The ultrashort electron packets are highly directional and examination of their spatial...

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