Regular Paper

[OPTICAL REVIEW Vol. 21, No. 5 (2014) 560-562]
© 2014 The Japan Society of Applied Physics

Improvement of Focusing Characteristics of a Spiral Plasmonic Lens

Shinpei OKUDA1, Naoyuki KIMURA1, Minoru TAKEDA2*, Tsutomu INOUE3, and Kento AIZAWA3

1Department of Electronics, Kyoto Institute of Technology, Kyoto 606-8585, Japan
2Department of Mathematical and Physical Sciences, Kyoto Institute of Technology, Kyoto 606-8585, Japan
3Spectroscopy Engineering Division, JASCO Corporation, Hachioji, Tokyo 192-8537, Japan

(Received November 29, 2013; Revised May 7, 2014; Accepted May 30, 2014)

We designed and fabricated a spiral plasmonic lens (PL) with multi-circular grooves to increase light intensity in a far-field region via the constructive interference of the light scattered by the multi-circular grooves. To compare the beam focusing characteristics of a spiral PL with multi-circular grooves with those of a conventional spiral PL, we simulated the electric field distribution of the PLs operating at a 405 nm wavelength. We confirmed that the light intensity increased about twofold at 0.75 μm above the PL surface owing to the effect of the multi-circular grooves. Furthermore, the circular grooves negligibly affect the full width at half-maximum of the focal spot, keeping the subwavelength size (∼200 nm) of incident light.

Key words: surface plasmon, plasmonic lens, far-field focusing, FDTD simulation

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