This review provides a perspective on the recent developments in the transmission of light through subwavelength apertures in metal films. The main focus is on the phenomenon of extraordinary optical transmission in periodic hole arrays, discovered over a decade ago. It is shown that surface electromagnetic modes play a key role in the emergence of the resonant transmission. These modes are also shown to be at the root of both the enhanced transmission and beaming of light found in single apertures surrounded by periodic corrugations. This review describes both the theoretical and experimental aspects of the subject. For clarity, the physical mechanisms operating in the different structures considered are analyzed within a common theoretical framework. Several applications based on the transmission properties of subwavelength apertures are also addressed.

http://digital.csic.es/bitstream/10261/47904/1/Light%20passing.pdf

Light passing through subwavelength apertures

The realization of miniaturized optofluidic platforms offers potential for achieving more functional and more compact devices. Such integrated systems bring fluid and light together and exploit their microscale interaction for a large variety of applications. The high sensitivity of compact microphotonic devices can generate effective microfluidic sensors, with integration capabilities. By turning the technology around, the exploitation of fluid properties holds the promise of highly flexible, tunable or reconfigurable microphotonic devices. We overview some of the exciting developments so far.

/pdf/integrated-optofluidics-a-new-river-of-light-3c3hleoeeg.pdf

Integrated optofluidics: A new river of light

We show a scheme for achieving high-speed operation for carrier-injection based silicon electro-optical modulator, which is optimized for small size and high modulation depth. The performance of the device is analyzed theoretically and a 12.5-Gbit/s modulation with high extinction ratio >9dB is demonstrated experimentally using a silicon micro-ring modulator.

/pdf/12-5-gbit-s-carrier-injection-based-silicon-micro-ring-1ts65w3d1i.pdf

12.5 Gbit/s carrier-injection-based silicon micro-ring silicon modulators

Exploring dynamics in the far-infrared with terahertz spectroscopy.

Biomedical Applications of Terahertz Spectroscopy and Imaging.

The development of ultrahigh-quality-factor Q silicon-on-insulator (SOI) microring resonators based on silicon wire waveguides is presented. An analytical description is derived, illustrating that in addition to low propagation losses the critical coupling condition is essential for optimizing device characteristics. Propagation losses as low as 1.9±0.1 dB/cm in a curved waveguide with a bending radius of 20 µm and a Q factor as high as 139.000±6.000 are demonstrated. These are believed to be the highest values reported for a curved SOI waveguide device and for any directly structured semiconductor microring fabricated without additional melting-induced surface smoothing.

Ultrahigh-quality-factor silicon-on-insulator microring resonator

Observation of Bloch oscillations in a semiconductor superlattice

Low-loss high dielectric-constant materials are analyzed in the terahertz frequency range using time-domain spectroscopy. The dielectric constant and loss tangent for steatite, alumina, titania loaded polystyrene, and zirconium-tin-titanate are presented and compared to measurements on high-resistivity silicon. For these materials, the real part of the dielectric constant ranges from 6 to 90. All of the samples were found to have reasonable low-loss tangents. Applications as photonic crystal substrates for terahertz frequency antenna are envisaged.

Measurement of the dielectric constant and loss tangent of high dielectric-constant materials at terahertz frequencies

We demonstrate the extraordinary transmission of terahertz THz radiation through gratings of subwavelength apertures structured in indium antimonide InSb. This transmission can be attributed to the tunneling of surface plasmons polaritons which are excited in semiconductors at THz frequencies. By thermally controlling the permittivity of the grating the transmittance increases by more than one order of magnitude. This increase might be associated to the larger the skin depth in InSb at low temperatures, nwhich gives rise to a larger effective size of the apertures.

/pdf/transmission-of-thz-radiation-through-insb-gratings-of-3h2snuy6pb.pdf

Transmission of THz radiation through InSb gratings of subwavelength apertures

We report on improved filter characteristics of microring resonators (MRs) used as add-drop multiplexers for integrated photonic circuits. By introducing an asymmetrical coupling of the signal waveguides to the resonator, a higher throughput attenuation and drop efficiency is attained. The throughput attenuation is the decisive property for the application of microrings in photonic networks since it determines the crosstalk between drop signal and add signal at the throughput channel of an add-drop multiplexer. Experimental results are compared with analytical relations. MRs with a free-spectral range of 24 nm are fabricated on silicon-on-insulator substrates. A crosstalk reduction by 8.8 dB due to asymmetrical coupling is demonstrated.

P.H. Bolivar

Papers

Ultrahigh-quality-factor silicon-on-insulator microring resonator

Observation of Bloch oscillations in a semiconductor superlattice

Measurement of the dielectric constant and loss tangent of high dielectric-constant materials at terahertz frequencies

Transmission of THz radiation through InSb gratings of subwavelength apertures

Asymmetrically coupled silicon-on-insulator microring resonators for compact add-drop multiplexers