Distributed Bragg grating frequency control in

Abstract-We show that Bragg gratings can be readily incorporated into metallic nano-lasers which exploit waveguides with semiconductor cores, via modulation of the waveguide width. This provides a simple way to implement laser wavelength control. Sub-wavelength confinement of light in passive plasmonic devices, such as waveguides, has received considerable attention in the last couple of years [1,2,3]. For a long time it was believed that, due to the high optical loss, it was impossible to achieve lasing in a plasmonic cavity. However, Hill and colleagues have shown that it is possible to reproducibly fabricate plasmonic cavities with moderate Q-factors and that it is also possible to sustain a lasing mode inside such a cavity [4,5]. The devices made by Hill are circular and rectangular shaped, with dimensions down to 80 nm, and are fully enclosed in silver. The devices are characterized by collecting light scattered through the substrate on which they are fabricated. To open the way for integration of these lasers in optical systems, side-emission is required. We believe that distributed feedback is suitable to enable side-emission in plasmonic cavities and propose to implement this via incorporation of vertical groove gratings inside the cavity. To ensure that the propagating mode in the laser cavity is indeed the fundamental plasmon mode of the structure, the width of the waveguide has to be such that it is below cut-off of the 1st order plasmon mode and below the cut-off of the fundamental TE mode of the waveguide. For operation at 1550 nm, the waveguide widths that satisfy these conditions were determined from 2-D FDTD simulations [6] and were found to be ±140 nm, for a waveguide with a 20 nm thick Si3N4 insulation layer and ±150 nm for a waveguide with a 10 nm thick insulation, figures 1 and 2