Compact chip-scale filter based on curved waveguide Bragg gratings

We propose a method for miniaturization of filters based on curved waveguide Bragg gratings, so that long structures can be packed into a small area on a chip. This eliminates the stitching errors introduced in the fabrication process, which compromise the performance of long Bragg gratings. Our approach relies on cascading curved waveguide Bragg gratings with the same radius of curvature. An analytical model for the analysis of these devices was developed, and a filter based on this model was designed and fabricated in a silicon on insulator platform. The filter had a total length of 920μm, occupied an area of 190μm×114μm, and exhibited a stop band of 1.7nm at 1.55μm and an extinction ratio larger than 23dB.     

Efficient conversion of light from sparse laser arrays into single-lobed far field using phase structures

An efficient beam-combining technique based on aperture filling is introduced to direct virtually all the energy of a mutually coherent laser array to the far-field main lobe. A comparison between this method and the Dammann grating method for beam superposition reveals the connection between the two and suggests specific applications for each.     

Effect of preparation parameters on properties and performance of Pd/Al2O3 catalyst in saturation of olefins

Research on Chemical Intermediates - The complete saturation of commercial olefin-containing (3.3 mol%) C4 stream over Pd/γ-Al2O3 catalysts was studied. The catalysts were prepared by...     

Single mode lasing in transversely multi‐moded PT‐symmetric microring resonators

Conventional techniques for transverse mode discrimination rely on introducing differential external losses to the different competing mode sets, enforcing single‐mode operation at the expense of additional losses to the desirable mode. We show how a parity‐time (PT) symmetric design approach can be employed to achieve single mode lasing in transversely multi‐moded microring resonators. In this type of system, mode selectivity is attained by judiciously utilizing the exceptional point dynamics arising from a complex interplay of gain and loss. The proposed scheme is versatile, robust to deviations from PT symmetry such as caused by fabrication inaccuracies or pump inhomogeneities, and enables a stable operation considerably above threshold while maintaining spatial and spectral purity. The experimental results presented here were obtained in InP‐based semiconductor microring arrangements and pave the way towards an entirely new class of chip‐scale semiconductor lasers that harness gain/loss contrast as a primary mechanism of mode selectivity.