Omer Khayam

General recipe for flatbands in photonic crystal waveguides

We present a general recipe for tailoring flat dispersion curves in photonic crystal waveguides. Our approach is based on the critical coupling criterion that equates the coupling strength of guided modes with their frequency spacing and results in a significant number of the modes lying collectively in the slow-light regime. We first describe the critical coupling scheme in photonic crystal waveguides using a simple coupled mode theory model. We also determine that canonical photonic crystal waveguides natively correspond to strongly coupled modes. Based on these analyses, our design recipe is as follows: Tune the profile of the first Fourier component of the waveguide periodic dielectric boundary to lower the coupling strength of the guided modes down to its critical value. We check that this generalized tuning may be accomplished by adjusting any desired optogeometric parameter such as hole size, position, index etc. We explore the validity of this general approach down to the narrow two-missing rows waveguides. The interest of this method is to circumvent most of the common trial-and-error procedures for flatband engineering.

Analysis and Optimization of Compact Demultiplexer Monitor Based on Photonic-Crystal Waveguide

A wavelength selective lateral outcoupler based on multimode photonic-crystal waveguides (WGs) is presented. Its fundamental advantages are a small footprint, an inherently flexible and versatile design, and a natural WG integration. Devices can serve demultiplexing or monitoring purposes. We numerically discuss design and optimization issues and corresponding details of experimental investigations.

In-plane Littrow lasing of broad photonic crystal waveguides

Broad photonic crystal waveguides forming open resonators are shown to support an hitherto unnoticed lasing pattern. The feedback for lasing originates in Littrow-type reflections of higher-order modes from the waveguide boundaries. The authors employ plane wave and finite-difference time-domain simulations of bulk crystal and waveguide to substantiate the concept of a distributed Littrow reflector. Experimental results are reported for a 10-μm-wide photonic crystal waveguide deeply etched into InP substrate. In-plane lasing and low modal threshold gain due to longer path lengths are the key features of this resonator.

Spontaneous Emission and Coupled-Mode Theory in Multimode 1-D Systems With Contradirectional Coupling

By means of source terms and coupled-mode theory, the essential features of spontaneous emission in multimode waveguides with counterdirectional feedback, such as corrugated and photonic crystal waveguides, are described in a heuristic manner. These multimode source terms generalize a similar approach evoked in multilayer structures. We account for features such as the “mini-stopband,” and the “stripe of minigaps” of broad photonic crystal waveguides, modeling previous experimental data. The result holds in several situations for which the differences in source terms for the uncoupled waveguide modes are not important. The approach yields significant results through a simple path.

Compact integrated photonic crystal demultiplexer for emitting and receiving InP photonic integrated circuits

Photonic-crystal-based demultiplexers, compact and versatile, are successfully used to demonstrate a polarisation-diversity receiving InP-based chip and a laser with integrated wavelength monitor. Selectivity improvements are discussed.

Experimental Observation of Band-Edge Lasing in Broad Planar 2D Photonic Crystal Waveguides

We report preliminary experiments on in-plane lasing in large-area planar 2D photonic crystal waveguides used as open resonators. Lasing is attributed to an unexpected feedback mechanism originating from Littrow diffraction at the photonic crystal walls.

Littrow Lasing in Photonic Crystal Waveguides

We propose Littrow based lasing of band edge modes in an open resonator formed by broad photonic crystal waveguide. The concept is developed by plane wave and FDTD simulations of bulk crystal and waveguide.