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This paper introduces a novel design of a tapered rib waveguide utilizing Hybrid Chalcogenide material. The waveguide is 4 mm in length and has a core of GAP-Se. GAP-Se is a combination of GeSe2, As2Se3, and PbSe. The upper and lower cladding are made of SiO2. The varying height of the rib layer results in a reduced effective mode area and an increased nonlinear coefficient. To achieve a desirable and intended supercontinuum spectrum in this waveguide, we utilize a pump pulse with a pulse duration of 100 fs and a power of 1 kW at a wavelength of 3.1 µm. We can change the waveguide dimensions to control and engineer the dispersion properties, which give us two zero dispersion wavelengths at 2.81 µm and 4.91 µm. As a result, we get a supercontinuum spectrum from 2.2 to 5 µm with a bandwidth of 2.8 µm. This design can be useful for different purposes such as biomedical, sensors, and optical coherence tomography. [ABSTRACT FROM AUTHOR]

A technique to solve generalized dispersion equation of multilayer planar waveguide has been demonstrated to obtain all the expected guided modes. The solution is based on the derivative free method for computing the zeros of an analytical function in complex plane. The derivative free method extracts the roots which are very close to actual zeros of the function. Roots are further refined using the robust iteration method to achieve the desired accuracy. Application of the proposed method has been verified by solving the modes of a variety of structures including lossless structure, leaky structure, quantum well waveguide, active waveguide, ARROW waveguide and metal clad waveguide. The method is efficient and computes all modes of planar waveguide with high accuracy. [ABSTRACT FROM AUTHOR]

The use of grating couplers in high index contrast waveguides like silicon on insulator (SOI) offers several advantages over other coupling approaches, including better alignment tolerances and allowing for wafer-scale testing. The grating couplers were developed for nanometric SOI waveguides (Si-wires), and recently also for micrometric rib waveguides. In this paper we review our work in fiber-to-chip grating couplers for thick SOI rib waveguides, where a coupling efficiency of −2.2 dB was demonstrated experimentally. We also discuss the use of grating couplers to improve optical throughput ( étendue) of a planar waveguide Fourier-Transform (FT) spectrometer implemented in thick rib waveguides. [ABSTRACT FROM AUTHOR]

The numerical simulations of nanogratings integrated with gallium nitride (GaN) planar waveguides as well as the experimental in-coupling results are presented. A simulation tool based on the eigenmode expansion method and advanced boundary conditions provided a rigorous model of 400-nm-period grating couplers. A full-vectorial Maxwell solver allowed performing a number of simulations with varying grating parameters, where coupling efficiency, reflection and transmission characteristics of device were calculated. Gratings with different etch depths and arbitrary shapes were simulated using a staircase approximation, with an optimized number of steps per single slope. For the first time, an impact of dry etch processing on GaN coupler efficiency was evaluated, due to the inclusion of the sloped sidewalls, with regard to the technological constrains. Finally, the experimental results in the visible spectrum region (λ = 633 nm), for 400-nm-deep gratings etched in GaN waveguide, were presented together with theoretical data for binary and trapezoidal profiles of a grating, for different optical mode profiles ( $${{\rm TE}_{0}\div {\rm TE}_{3}\,{\rm modes}}$$). [ABSTRACT FROM AUTHOR]

we present here a simple numerical method to obtain the mode effective indices as well as field distributions of modes of any arbitrary profile planar optical waveguide. The method is based on the solutions of scalar and semivectorial Helmoltz’s equation by finite difference algorithm and devised with a field convergence technique. This approach is quite general and can be applied straightforwardly to calculate the guided as well as quasi- or leaky modes of any arbitrary planar structure without the need to solve any eigenvalue equation or any complex matrix formalism. Besides providing the ease of application, the algorithm is particularly useful for waveguides with any graded index profile or with irregular multilayered structure and multilayered waveguides with a localised arbitrary nonlinear film. The performance of our method is verified against typical problems with analytical solutions or having results known otherwise, and is shown to yield results with good accuracy. [ABSTRACT FROM AUTHOR]

Characteristics of propagation of bright screening solitons are studied in a photorefractive waveguide. The investigation is performed under paraxial wave approximation and Wentzel-Kramers-Brillouin-Jefferys approximation. A Gaussian ansatz for the soliton shape is used instead of the numerical solutions. The planar waveguide structure intensifies the self-focussing while decreasing the minimum or threshold power required for self trapping. The waveguide structure embedded in the crystal can self trap a soliton of power lower than the threshold power. As the waveguide parameter increases, minimum required power to self trap the beam decreases. The existence of bistable states is also predicted. Four regimes of power are identified in which the solitons behaviour is studied. Propagation of screening solitons in a photorefractive waveguide is studied in the absence of the photovoltaic and pyroelectric effect for the first time. [ABSTRACT FROM AUTHOR]

In this paper, novel single-mode (SM) photonic-crystal planar waveguides (PCPW) and linear arrays have been proposed and systematically studied. Advanced elliptic features are embedded into the basic photonic crystal design to differentiate leakage losses between the fundamental and high-order modes, which ensures SM propagation property. Furthermore, linear arrays of PCPWs are proposed to generate fundamental supermodes with ultra-large SM areas. Our study shows that these multi-unit PCPW linear arrays can perform equivalently as ultra-wide planar waveguides that are possible to achieve SM modal areas as large as over 10,000 μm2 with preferable Gaussian-shaped far-field intensity patterns, readily supporting optical powers well over 100 kW. The presented study can be inspiring for designs of single-waveguide solid-state lasers and amplifiers to generate laser beams of extremely high power and high brightness. [ABSTRACT FROM AUTHOR]