A Mach–Zehnder interferometer (MZI)-based liquid refractiveindex sensor, utilizing a hollow hybrid plasmonic (HP)waveguide as the sensing element, has been investigated,showing large sensitivity to the refractive index changesof the tested liquids, as well as lower propagation loss incomparison to typical plasmonic waveguide-based ones.The sensor is fabricated using conventional silicon-oninsulator(SOI) technology; therefore, it is compatible toother standard SOI devices. The waveguide sensitivity, Sw,is experimentally demonstrated to be 0.64, with a propagationloss less than 0.25 dB/μm. Using a 20 μm long hollowHP waveguide in the sensing arm, the sensitivity of the MZIsensor (device sensitivity, Sd ) is about 160 nm/RIU, with anextinction ratio larger than 40 dB.

A MEMS tunable hybrid plasmonic-Si (HP) waveguide is investigated, showing verylarge changes of both effective refractive index and propagation loss when applying bias voltage.Preliminary experimental results show that: with 15μm MEMS structure in Si waveguideplatform, the extinction ratio can be over 20dB between “on” and “off” states.

We propose and demonstrate an ultracompact on-chip photothermal power monitor based on a silicon hybrid plasmonic waveguide (HPWG), which consists of a metal strip, a silicon core, and a silicon oxide (SiO2) insulator layer between them. When light injected to an HPWG is absorbed by the metal strip, the temperature increases and the resistance of the metal strip changes accordingly due to the photothermal and thermal resistance effects of the metal. Therefore, the optical power variation can be monitored by measuring the resistance of the metal strip on the HPWG. To obtain the electrical signal for the resistance measurement conveniently, a Wheatstone bridge circuit is monolithically integrated with the HPWG on the same chip. As the HPWG has nanoscale light confinement, the present power monitor is as short as ~3 μm, which is the smallest photothermal power monitor reported until now. The compactness helps to improve the thermal efficiency and the response speed. For the present power monitor fabricated with simple fabrication processes, the measured responsivity is as high as about 17.7 mV/mW at a bias voltage of 2 V and the power dynamic range is as large as 35 dB.

Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline semiconducting nanostructures, which are known for their application in photovoltaics. Due to the internal arrangement, P3HT nanofibers possess optical anisotropy, which can be enhanced on a macroscale if nanofibers are aligned. Alternating electric field, applied to a solution with dispersed nanofibers, causes their alignment and serves as a method to produce solid layers with ordered nanofibers. The transmission ellipsometry measurements demonstrate the dichroic absorption and birefringence of ordered nanofibers in a wide spectral range of 400–1700 nm. Moreover, the length of nanofibers has a crucial impact on their degree of alignment. Using electric birefringence technique, it is shown that external electric field applied to the solution with P3HT nanofibers can cause direct birefringence modulation. Dynamic alignment of dispersed nanofibers changes the refractive index of the solution and, therefore, the polarization of transmitted light. A reversible reorientation of nanofibers is organized by using a quadrupole configuration of poling electrodes. With further development, the described method can be used in the area of active optical fiber components, lab-on-chip or sensors. It also reveals the potential of 1D conducting polymeric structures as objects whose highly anisotropic properties can be implemented in electro-optical applications.​

An electro-optic polymer-based hollow hybrid plasmonic phase modulator has beenproposed. Estimating from our preliminary experimental results, related to a hollow HP liquidsensor, the proposed device shows unique advantages in high speed modulation applications.

We analyze whispering gallery-type disk resonators with radii down to 50 nm. Single interface waveguiding is accomplished by a plasmonic-dielectric interface operating near the surface plasmon polariton (SPP) resonance, employing a hypothetical material with lower loss than what is currently available in metals or negative permittivity media. The disk is immersed in a second dielectric, nonresonant to the plasmonic medium. Due to the high effective index of the disk mode and the concomitant low radiation losses, the quality (Q) values of the resonator are solely determined by material losses, in contrast to more conventional nanoscale resonators. We calculate the dependence of the effective indices of the guided mode, the Q values of absorption and radiation, and the Purcell factor on the deviation from the SPP resonance.

Highly-efficient double-slot hybrid plasmonic cavity is demonstrated. By measuring phase change with different liquids, we show that this sub-wavelength structure has better modulation efficiency than Si-based one for applications in ultra-compact highly-efficient sensors and modulators.

The nanofiber morphology of regioregular Poly-3- hexylthiophene (P3HT) is a 1D crystalline structure organized by π - π stacking of the backbone chains. In this study, we report the impact of electric field on the orientation and optical properties of P3HT nanofibers dispersed in liquid solution. We demonstrate that alternating electric field aligns nanofibers, whereas static electric field forces them to migrate towards the cathode. The alignment of nanofibers introduces anisotropic optical properties, which can be dynamically manipulated until the solvent has evaporated. Time resolved spectroscopic measurements revealed that the electro-optical response time decreases significantly with the magnitude of applied electric field. Thus, for electric field 1.3 V ·μm-1 the response time was measured as low as 20 ms, while for 0.65 V ·μm-1 it was 110-150 ms. Observed phenomenon is the first mention of P3HT supramolecules associated with electrooptical effect. Proposed method provides real time control over the orientation of nanofibers, which is a starting point for a novel practical implementation. With further development P3HT nanofibers can be used individually as an anisotropic solution or as an active component in a guest-host system.

AC electric poling introduces in P3HT nanofibers anisotropic electro-optical response and birefringence. Along with birefringence, such material exhibits strong amplitude modulation which makes it more efficient alternative to liquid crystals. © 2015 OSA.

A Mach-Zehnder Interferometer (MZI) liquid sensor, employing ultra-compact double-slot hybrid plasmonic (DSHP) waveguide as active sensing arm, is developed. Numerical results show that extremely large optical confinement factor of the tested analytes (as high as 88%) can be obtained by DSHP waveguide with optimized geometrical parameters, which is larger than both, conventional SOI waveguides and plasmonic slot waveguides with same widths. As for MZI sensor with 40 mu m long DSHP active sensing area, the sensitivity can reach as high value as 1061nm/RIU (refractive index unit). The total loss, excluding the coupling loss of the grating coupler, is around 4.5dB.