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Epsilon near zero (ENZ) materials exhibit strongly confined optical modes and plasmonic response around and beyond the ENZ wavelength (λENZ). In order to exploit the novel properties of ENZ materials for real-world applications, it is important to develop material platforms that offer continuous tuning of λENZ. We report octave span, controllable, and reversible tuning of λENZ from 1280 nm to 2900 nm in commercially available thin films of indium tin oxide (ITO), employing a low temperature annealing protocol. Electrical, spectroscopic, and optical measurements establish the physical basis of the observed tunability in free electron density by over an order of magnitude and quantify the real and imaginary components of the refractive index for ITO thin films. Excitation of surface plasmon polaritons (SPPs) in the metallic regime of ITO probes its infrared plasmonic response demonstrating continuous tunability of SPP frequency and crossover to the tunable ENZ plasmon mode in ultrathin films. Finally, dispersion tuning of optical fiber modes by optical coupling with a tunable λENZ platform is demonstrated by investigating modal interference in a tapered silica fiber in contact with various custom tuned ITO films.

The extraordinary mechanical properties of two-dimensional transition-metal dichalcogenides make them ideal candidates for investigating strain-induced control of various physical properties. Here we explore the role of nonuniform strain in modulating optical, electronic, and transport properties of semiconducting, chemical vapor deposited monolayer MoS2, on periodically nanostructured substrates. A combination of spatially resolved spectroscopic and electronic properties explore and quantify the differential strain distribution and carrier density on a monolayer, as it conformally drapes over the periodic nanostructures. The observed accumulation in electron density at the strained regions is supported by theoretical calculations which form the likely basis for the ensuing ×60 increase in field effect mobility in strained samples. Though spatially nonuniform, the pattern-induced strain is shown to be readily controlled by changing the periodicity of the nanostructures thus providing a robust yet useful macroscopic control on strain and mobility in these systems.

Combined experimental and theoretical calculations shed light on the enhancement of conductivity through I2 incorporation in an indium metal–organic framework.

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