We report on an integrated plasmonic ultraviolet (UV) photodetector composed of aluminum Fano-resonant heptamer nanoantennas deposited on a Gallium Nitride (GaN) active layer which is grown on a sapphire substrate to generate significant photocurrent via formation of hot electrons by nanoclusters upon the decay of nonequilibrium plasmons. Using the plasmon hybridization theory and finite-difference time-domain (FDTD) method, it is shown that the generation of hot carriers by metallic clusters illuminated by UV beam leads to a large photocurrent. The induced Fano resonance (FR) minimum across the UV spectrum allows for noticeable enhancement in the absorption of optical power yielding a plasmonic UV photodetector with a high responsivity. It is also shown that varying the thickness of the oxide layer (Al₂O₃) around the nanodisks (tox) in a heptamer assembly adjusted the generated photocurrent and responsivity. The proposed plasmonic structure opens new horizons for designing and fabricating efficient opto-electronics devices with high gain and responsivity.

No abstract

We report on photo-thermal modulation of thin film surface plasmon polaritons (SPP) excited at telecom wavelengths and traveling at a gold/air interface. By operating a modulated continuous-wave or a Q-switched nanosecond pump laser, we investigate the photo-thermally induced modulation of SPP propagation mediated by the temperature-dependent ohmic losses in the gold film. We use a fiber-to-fiber characterization set-up to measure accurately the modulation depth of the SPP signal under photo-thermal excitation. On the basis of these measurements, we extract the thermo-plasmonic coefficient of the SPP mode defined as the temperature derivative of the SPP damping constant. Next, we introduce a figure of merit which is relevant to characterize the impact of temperature onto the properties of bounded or weakly leaky SPP modes supported by a given metal at a given wavelength. By combining our measurements with tabulated values of the temperature-dependent imaginary part of gold dielectric function, we compute the thermo-optical coefficients (TOC) of gold at telecom wavelengths. Finally, we investigate a pulsed photo-thermal excitation of the SPP in the nanosecond regime. The experimental SPP depth of modulation obtained in this situation are found to be in fair agreement with the modulation depths computed by using our values of gold TOC.

No abstract

International audienceDielectric loaded gratings (DLGs) comprised of polymer gratings lying on a thin gold film are used to couple light at telecommunication frequencies in and out of plasmonic waveguides featuring sub-micron cross-sections. The grating couplers are found to be efficient and easy to implement to perform direct fiber-to-fiber telecommunication characterizations of dielectric loaded surface plasmon polariton waveguide (DLSPPW) components. By analyzing the dispersion of the plasmonic Bloch modes supported by DLGs as a function of the period and the filling factor of the gratings, efficient couplers comprised of gratings with a filling factor around 0.5 are designed and fabricated by a simple one-step electron beam lithography process. Typical losses in the range of dB per coupler are obtained for gratings designed to operate at normal and 30 -tilted incidence. The performance of the couplers for normal incidence can be further improved by adding a back-reflecting Bragg mirror. We demonstrate the transmission of a 10 Gbits/s signal along a 75 m-long DLSPPW by using DLG couplers for light injection and extraction. A power penalty below below 0.4 dB on the bit-error-rate has been measured over the entire C-band demonstrating the suitability of DLSPPWs for Wavelength-Division-Multiplexed high bit rate traffic and the efficiency of DLG couplers for fiber-to-fiber characterizations of stand alone DLSPPW components