Daniel Owens

Variable splitting ratio 2×2 MMI couplers using multimode waveguide holograms

Variable power splitting ratio 2x2 MMI couplers using multimode waveguide holograms are analyzed. Theoretical analysis shows that variable splitting ratios can be obtained with surface relief holograms on MMI couplers with fixed dimensions. Devices with paired-imaging lengths are designed on a silicon-on-insulator (SOI) platform. Beam propagation simulations are used to verify a matrix theory analysis and to investigate proposed device performance. Fabrication tolerance of the proposed device is also analyzed.

A comprehensive analysis of the contributions to the nonlinear optical properties of thin Ag films

The nonlinear optical properties of 20 nm thick Ag films are investigated by time-resolved white- light continuum pump-probe experiments in both transmission and reflection mode. The dynamics of changes in permittivity Δe are measured at wavelengths between 500 to 700 nm. The data is fitted to a modified Drude model in the frequency domain and to a two-temperature model in the time domain. Changes in the individual Drude parameters are calculated as a function of time. A single, coherent model is proposed based on these fittings that describes the dynamics of the nonlinear optical properties of Ag, which could be used to model the nonlinear responses of multilayer structures containing thin films of Ag. The physical origins of the observed responses are discussed.

Controlling the directional emission of holey organic microlasers

The far-field pattern of stadium-shaped organic microlasers is strongly modified by introducing circular air vacancies within the cavity, so as to control it in a predictive way. Experimental results are in good agreement with geometrical optics predictions whereas spectral properties of emission are investigated to improve the understanding of the lasing modes.

Nonlinear optical properties of induced transmission filters.

The nonlinear optical (NLO) properties of induced transmission filters (ITFs) based on Ag are experimentally determined using white light continuum pump-probe measurements. The experimental results are supported using simulations based on the matrix transfer method. The magnitude of the NLO response is shown to be 30 times that of an isolated Ag film of comparable thickness. The impacts of design variations on the linear and NLO response are simulated. It is shown that the design can be modified to enhance the NLO response of an ITF by a factor of 2 or more over a perfectly matched ITF structure.

Ultrafast optical image processing based on third-harmonic generation in organic thin films

We report on the use of the noncollinear third-harmonic generation in an amorphous polymer film operating in the eye safe and telecommunication compatible near-infrared range to perform ultrafast all-optical two-dimensional (2D) image processing at 1550nm using 100fs pulses. The background-free and nondegenerate outputs at 517nm are easily spatially filtered and detected with low cost electronic components. We describe this Fourier transform based technique and demonstrate its application to the classical problem of 2D image recognition.

The ultrafast nonlinear optical properties of induced transmission filters

We report on the nonlinear optical properties of induced transmission filters with 30× enhancement compared with a 30 nm Ag film and with a peak transmittance of 63% in the visible.

Linear and nonlinear optical properties of highly transmissive one-dimensional metal-organic photonic bandgap structures

We present the design, fabrication and characterization of the optical properties of one-dimensional metal-organic photonic bandgaps (MO-PBGs) composed of a tetraphenyldiaminobiphenyl-based polymer and ultrathin electrically continuous Cu layers. The fabricated MO-PBGs achieve a peak transmission of around 44% at 620 nm combined with very large spectral, around 120 nm FWHM, and angular, more than 120° field-of-view, bandwidths. Using 140 fs pulses at various wavelengths we have found up to 10 × enhancements in the nonlinear optical (NLO) properties of the MO-PBGs when compared with the NLO response of ultrathin electrically continuous Cu layers.

Nonlinear optical properties of layered multi-metal nanostructures

We report on the temporal and spectral dynamics of the nonlinear optical response of transparent Ag/Au multi-metal layers and Fabry-Perot resonators with 10× enhancement compared with Ag and with comparable transparency in the visible.

A comprehensive study of the contributions to the nonlinear optical properties of thin Ag films

We report on the nonlinear optical (NLO) transmittance and reflectance of a 20 nm-thick Ag film characterized by time-resolved white-light continuum pump-probe experiments. The change in complex permittivity Δε(t) is extracted and is fitted to the Drude model in the frequency domain and a two-temperature model in the time domain. A unified model is presented that fully describes the dynamic NLO response of a thin Ag film that can be incorporated easily into the modeling of more complex metal-dielectric multilayer structures designed to take advantage of the NLO response of Ag.

The nonlinear optical response of transparent silver/gold multi-metal layers

We report on the linear and nonlinear optical properties of Ag/Au multi-metal thin films and Fabry-Perot resonator cavities. The linear optical properties of these multi-metal layers, having different mass distributions and Ag/Au ratios with thicknesses around 15 nm, resemble those of electrically continuous metal layers. The optical losses introduced by interband transitions in the Au layers are reduced to achieve peak transmittances of 76 % around 550 nm. Using femtosecond-pulsed white-light continuum pump-probe experiments we show that the nonlinear optical response of such multi-metal layers is comparable to that of neat Au thin films. Low-finesse Fabry-Perot resonators fabricated with such multi-metal layers, combine the large NLO response of Au with a transmittance of 60% and a spectral bandwidth that covers the visible spectral range.