Sub-volt broadband hybrid plasmonic-vanadium dioxide switches

Abstract

Surface plasmon polaritons can substantially reduce the sizes of optical devices, since they can concentrate light to (sub)wavelength scales [1-3]. However, (sub)wavelengthscale electro-optic plasmonic switches or modulators with high efficiency, low insertion loss, and high extinction ratios remain a challenge due to their small active volumes [4][5][6]. Here, we use the insulator-metal phase transition of a correlated-electron material, vanadium dioxide, to overcome this limitation and demonstrate compact, broadband, and efficient plasmonic switches with integrated electrical control. The devices are micron-scale in length and operate near a wavelength of 1550 nm. The switching bandwidths exceed 100 nm and applied voltages of only 400 mV are sufficient to attain extinction ratios in excess of 20 dB. Our results illustrate the potential of using phase transition materials for highly efficient and ultra-compact plasmonic switches and modulators.The miniaturization of optical devices, whether using surface plasmon polaritons (SPPs) at metal-dielectric interfaces or strongly confined electromagnetic modes in high-indexcontrast dielectric waveguides, presents an opportunity to reduce the sizes of electro-optic switches and modulators. As the volume of the active region shrinks, if the optical confinement is maintained, the amount of energy required to activate the material for modulation decreases. However, small active regions and low power consumption often come at the cost of a reduced extinction ratio. In dielectric devices, this trade-off is often overcome by recirculating light in high-Q microcavities, which restrict the operation wavelengths to narrowband cavity resonances [7]. Plasmonic devices can be significantly more broadband, but the losses of SPPs typically prevent high-Q microcavities from being formed and limit the devices to micron or sub-micron lengths. These constraints have led to large switching voltages > 10 V [8,9] and extinction ratios that are at best ∼ 10 dB [4, 10] for short plasmonic switches that are no more than several microns long.Efficient and compact electro-optic plasmonic switches require materials that exhibit exceptionally large changes in their refractive indices when subjected to electrical control signals. A promising material for infrared wavelengths is the correlated-electron material, vanadium dioxide (VO 2 ). The electronic distribution and lattice of VO 2 can reversibly reconfigure to produce an insulator-metal phase transition with a resistivity change of up to three orders of magnitude. The phase transition can be initiated by temperature changes [11], optical [12] face charge accumulations [15], or mechanical strain [16]. In this work, we demonstrate plasmonic switches with low switching voltages and record high extinction ratios using a hybrid SPP-VO 2 geometry and the thermally-induced VO 2 phase transition. In contrast to previous proposals and demonstrations [4,10,[17][18][19][20], our devices are highly compact (between 5 to 15 µm long) and have integrated el...

Transparent conducting oxides for electro-optical plasmonic modulators

“…In particular, an ER up to 2.4 dB/µm was demonstrated for a hybrid plasmonic modulator based on the metal-insulator phase transition in vanadium dioxide [154]. However, neither structural transitions nor thermo-optic responses provide the necessary bit rate, so only megahertz modulation operations are expected due to microsecond timescales of the aforementioned alternative processes.…”

“…silicon [40,41,[130][131][132][133][134][135][136] and TCOs [112,113,128,[137][138][139][140][141][142][143][144][145][146][147]), and structural phase transitions (e.g. gallium [148][149][150][151] and vanadium dioxide [152][153][154][155][156][157]). In addition, plasmonic modulators based on thermo-optic [158][159][160][161] or nonlinear polymer [162,163], graphene [164][165][166], indium phosphide [167,168], barium titanate [169], bismuth ferrite [170], and germanium [171] were also reported.…”

Optically Monitored Electrical Switching in VO2

“…21,23 In order to deploy the electrical SMT in photonic and electronic devices, further insight into the phase-transition dynamics is needed.…”

Ultra-Compact On-chip Electro-Optic Waveguide Ring Resonators Based on Asymmetric Au-(Pb, La)(Zr, Ti)O3-Au Structure

“…Moreover, the reliability of waveguide devices based on PLZT thin films is much better than the same type devices dependent on EO polymers and NLCs. In comparison with the EO modulators based on VO 2 [17,34] and doped silicon [35], the electro-optical control of PLZT waveguide devices can be accomplished through modulating the electric field directly, making the fabrication process and structure of total device much simpler. Hence, we believe an improvement of the performance of EO modulators can be obtained with the combination of PLZT thin films and plasmonic components.…”