S-matrix absolute optimization method for a perfect vertical waveguide grating coupler.

Vertical coupling using a diffraction grating is a convenient way to couple light into an optical waveguide. Several optimization approaches have been suggested in order to design such a coupler; however, most of them are implemented using algorithm-based modelling. In this paper, we suggest an intuitive method based on S-matrix formalism for analytically optimize 3-port vertical grating coupler devices.

Spectral characterization of nanostructured birefringent porous silicon.

We present measurements and analysis of the reflection spectrum of white light from a highly birefringent porous silicon layer at different polarization states. We report an anomalous pattern in the spectrum of linearly polarized light at 45° with respect to the principal axes of the layer. This spectrum comprises a combination of two interference effects, namely the Fabry-Perot-type multiple-beam interference present in a simple thin film, and a two-wave interference caused by the beat of two combined orthogonally polarized waves propagating in the birefringent medium.

Linearized electro-optic racetrack modulator based on double injection method in silicon.

Racetrack-based modulator of increased linearity for optical links is presented and analyzed. The modulator is referred to as FLAME - Finer Linearity Amplitude Modulation Element. Linearity is improved via the introduction of a Double Injection approach.

Integrated photonic threshold comparator based on square-wave synthesis.

A photonic threshold comparator is presented. A step-like electrical-to-optical (E/O) response is obtained by employing Fourier series synthesis in which a set of sine-wave responses of different amplitudes and phases are superimposed according to the Fourier series representation of a square-wave. The proposed comparator does not rely on optical material non-linearity; rather it consists of multimode interference (MMI) couplers and phase shifters.

Diffractive optical elements for mode-division multiplexing of temporal signals with the aid of Laguerre-Gaussian modes.

Optical aspects of space-division multiplexing with orthogonal modes of coherent light were considered in theory and experiments with the coherent optical correlator. We resorted to the mathematical tool of generating functions and technologies of diffractive optical elements to implement complex spatial filters matched to rotationally symmetrical transverse modes. Successful multiplexing and demultiplexing in free-space transmission of low-frequency temporally modulated signals through different spatial modes was demonstrated.

Generating arbitrary optical signal constellations using microring resonators.

It is shown that two mutually uncoupled microresonators in series can adequately cover the entire I-Q space and render the realization of QAM signals possible. This approach is based on the independent optimization of each microresonator for amplitude and phase modulation respectively. Generation of 16 quadrature amplitude modulation is demonstrated by means of simulation.

Gaussian content as a laser beam quality parameter.

We propose the Gaussian content (GC) as an optional quality parameter for the characterization of laser beams. It is defined as the overlap integral of a given field with an optimally defined Gaussian. The definition is especially suited for applications where coherence properties are targeted.

Guiding effects in waveguides with anti-symmetric refractive index layouts.

This paper presents and analyzes configurations of waveguides composed by both, regular dielectrics and negative-index materials disposed in an anti-symmetric way with respect to the optical axis. In its basic form, the configuration includes two guiding layers and two cladding media, where both the cladding and the guiding pairs have opposite-signed refractive index. A geometrical analysis shows that paths are closed, hinting the possibility of localized modes or light trapping with zero ray velocity.

Diffractive optical elements with porous silicon layers.

We investigate the basic chromatic properties of dispersive surface relief diffractive optical elements with porous silicon (PSi) layers. Rigorous and scalar wavelength-dependent diffraction efficiencies are juxtaposed and compared to reflection coefficients of uniform silicon and PSi layers. The application of the device as an enhanced sensor is discussed.

Critical sensitivity effect in an interferometer sensor.

We report the observation of anomalous behavior in the spectral sensitivity response in a specially designed waveguided interferometer sensor. Approaching a definite critical point, the sensitivity increases nonlinearly. Furthermore, at the critical wavelength a new effect of splitting or bifurcation of a minimum dip is observed.

Critical sensitivity in hetero-modal interferometric sensor using spectral interrogation.

This paper reports on the finding of a critical working point in the sensitivity of hetero-modal interferometric optical sensors using spectral interrogation. At this point the theoretical sensitivity approaches infinity and the practical sensitivity will depend only on the measurement accuracy and noise sources present. If the critical condition is attained at a point of minimal power transfer, a phenomenon of splitting or bifurcation of the minimum dip is expected as sensing occurs.

Tight packaging of erbium-doped waveguide amplifiers.

A numerical model for erbium-doped waveguide amplifiers (EDWAs) containing bent waveguides was developed. The model uses rate-propagation equations and takes into account bend-induced losses in the waveguide with a varying radius of curvature. It is applied to the design of tightly packed erbium-doped waveguide amplifiers under two constraints: minimization of the area required to obtain a predetermined gain and maximization of the gain available from a given area.

Fast method for physical optics propagation of high-numerical-aperture beams.

A method is presented that expands the scheme of physical optics propagation beyond the Fresnel approximation to include beams that are nonparaxial. The formalism retains most of the calculation advantages of the Fresnel approach; i.e.

Temperature-dependent Sellmeier equation for the refractive index of stoichiometric lithium tantalate.

We present a temperature-dependent Sellmeier equation for the refractive index of stoichiometric LiTaO3. The extraordinary refractive index, for the range 0.39-4.