Ultra-compact waveguide electroabsorption optical switches and photodetectors with micron- and sub-micron lengths and compatible with silicon (Si) waveguides are demonstrated using the insulator-metal phase transition of vanadium dioxide (VO(2)). A 1 μm long hybrid Si-VO(2) device is shown to achieve a high extinction ratio of 12 dB and a competitive insertion loss of 5 dB over a broad bandwidth of 100 nm near λ = 1550 nm. The device, operated as a photodetector, can measure optical powers less than 1 μW with a responsivity in excess of 10 A/W. With volumes that are about 100 to 1000 times smaller than today's active Si photonic components, the hybrid Si-VO(2) devices show the feasibility of integrating transition metal oxides on Si photonic platforms for nanoscale electro-optic elements.

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...

Voltage-controlled switching in lateral VO2 nano-gap junctions with different gap lengths and thermal properties was investigated. The effect of Joule heating on the phase transition was found to be strongly influenced by the device geometry, the contact material, and the current. Our results indicate that the VO2 phase transition was likely initiated electronically, which was sometimes followed by a secondary thermally induced transition.

We present two types of designs for plasmonic switches based on hybridization between single interface surface plasmon polaritons and modes of a thin film of transition metal oxide material, vanadium dioxide (VO(2)). The design includes integrated, localized heaters that activate the VO(2) transition. The device operation is investigated and optimized by electromagnetic, electrical, and thermal simulations. The large change in the VO(2) refractive index in the infrared wavelength range enables highly compact and efficient plasmonic switches. The proposed designs achieve extinction ratios of 23-32 dB using only a 5 μm active region, a switching voltage of about 60 mV, and a switching power of about 9 mW.

A norbornene-mediated palladium-catalyzed sequence is described in which an alkyl-aryl bond and an aryl-heteroaryl bond are formed in one reaction vessel. The aryl-heteroaryl bond-forming step occurs via a direct arylation reaction. A number of six-, seven-, and eight-membered ring-annulated indoles, pyrroles, pyrazoles, and azaindoles were synthesized from the corresponding bromoalkyl azole and an aryl iodide.