Electrically generated unidirectional surface plasmon source.

We experimentally demonstrated an electrically excited surface plasmon source, which was fulfilled in a silver coated light emitting diode (LED) with well-designed gratings. With a DC current supply, surface plasmon polariton (SPP) waves were generated directly from the illuminations of the LED via the grating coupler. By adjusting the grating to a tilted one, a unidirectional SPP beam was successfully attained with a high extinction ratio (ER~10) and an improved launching efficiency. Detailed analyses show that this electrically generated unidirectional SPP has a considerable long propagation distance (~14 μm), allowing for further manipulations in plasmonic integrations and sensors.