Miniature Surface Plasmon Polariton Amplitude Modulator by Beat Frequency and Polarization Control.

Cheng-Wei Chang,Chu-En Lin,Chih-Jen Yu,Ta-Jen Yen,Ting-Tso Yeh

doi:10.1038/srep32098

Cheng-Wei Chang, Chu-En Lin + Show 3 more

Open Access

https://doi.org/10.1038/srep32098

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Abstract

The miniaturization of modulators keeps pace for the compact devices in optical applications. Here, we present a miniature surface plasmon polariton amplitude modulator (SPPAM) by directing and interfering surface plasmon polaritons on a nanofabricated chip. Our results show that this SPPAM enables two kinds of modulations. The first kind of modulation is controlled by encoding angular-frequency difference from a Zeeman laser, with a beat frequency of 1.66 MHz; the second of modulation is validated by periodically varying the polarization states from a polarization generator, with rotation frequencies of 0.5–10 k Hz. In addition, the normalized extinction ratio of our plasmonic structure reaches 100. Such miniaturized beat-frequency and polarization-controlled amplitude modulators open an avenue for the exploration of ultrasensitive nanosensors, nanocircuits, and other integrated nanophotonic devices.

Highlights

A plasmonic modulator can certainly be compact, but it requires a coupler to compensate the mismatched wave momentum between the propagating mode and the surface mode[7]
The integration of the FB coupler and the continuous wave (CW) lasers is developed for the surface plasmon polaritons (SPP) amplitude modulator (SPPAM)
The controlled polarized lights were transmitted through an array of 4 × 4 FB couplers (Fig. 1(b,c)), exciting SPP propagation along the air/Ag interface

Summary

Introduction

A plasmonic modulator can certainly be compact, but it requires a coupler to compensate the mismatched wave momentum between the propagating mode and the surface mode[7]. Several types of unidirectional couplers have appeared that guide the SPP waves by breaking the phase symmetry and controlling the polarization states, such as an aperiodic groove[13], a double slit[14], a guiding-mode controller[15,16,18], a dipole mode rotator[32], and a Fishbone (FB) structure[17]. Among these unidirectional couplers, the FB structure exhibits further advantages of directing the SPP by the specific polarization states, and of exciting the SPP under the normal incidence[17]. The presence of the SPPAMs can be further explored for use in nanosensors[19], plasmonic switches[23], and other applications

Methods

Results

Discussion

Conclusion