Ertugrul Cubukcu, Nanfang Yu, Elizabeth J. Smythe, Laurent Diehl, Kenneth B. Crozier, and Federico Capasso. 2008. “Plasmonic Laser Antennas and Related Devices.” IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, 14, 6, Pp. 1448-1461.
This paper reviews recent work on device applications of optical antennas. Localized surface plasmon resonances of gold nanorod antennas resting on a silica glass substrate were modeled by finite difference time-domain simulations. A single gold nanorod of length 150 or 550 nm resonantly generates enhanced near fields when illuminated with light of 830 nm wavelength. A pair of these nanorods gives higher field enhancements due to capacitive coupling between them. Bowtie antennas that consist of a pair of triangular gold particles offer the best near-field confinement and enhancement. Plasmonic laser antennas based on the coupled nanorod antenna design were fabricated by focused ion beam lithography on the facet of a semiconductor laser diode operating at a wavelength of 830 nm. An optical spot size of few tens of nanometers was measured by apertureless near-field optical microscope. We have extended our work on plasmonic antenna into mid-infrared (mid-IR) wavelengths by implementing resonant nanorod and bowtie antennas on the facets of various quantum cascade lasers. Experiments show that this mid-IR device can provide an optical intensity confinement 70 times higher than that would be achieved with diffraction limited optics. Near-field intensities similar to 1 GW / cm(2) were estimated for both near-infrared and mid-IR plasmonic antennas. A fiber device that takes advantage of plasmonic resonances of gold nanorod arrays providing a high density of optical ``hot spots'' is proposed. Results of a systematic theoretical and experimental study of the reflection spectra of these arrays fabricated on a silica glass substrate are also presented. The family of these proof-of-concept plasmonic devices that we present here can be potentially useful in many applications including near-field optical microscopes, high-density optical data storage, surface enhanced Raman spectroscopy, heat-assisted magnetic recording, and spatially resolved absorption spectroscopy.