The use of thermoresponsive poly(N-isopropylacrylamide)-based hydrogel (pNIPAAm) for rapid tuning of surface plasmon resonance (SPR) is reported. This approach is implemented by using an SPR layer architecture with an embedded indium tin oxide microheater and pNIPAAm film on its top. It takes advantage of rapid thermally induced swelling and collapse of pNIPAAm that is accompanied by large refractive index changes and leads to high thermo-optical coefficient of dn/dT = 2 × 10–2 RIU/K. We show that this material is excellently suited for efficient control of refractive index-sensitive SPR and that it can serve simultaneously as a 3D binding matrix in biosensor applications (if modified with biomolecular recognition elements for a specific capture of target analyte). We demonstrate that this approach enables modulating of the output signal in surface plasmon-enhanced fluorescence spectroscopy biosensors and holds potential for simple time-multiplexing of sensing channels for parallelized readout of fluoresc...

Active Control of SPR by Thermoresponsive Hydrogels for Biosensor Applications

We report on photo-thermal modulation of thin film surface plasmon polaritons (SPP) excited at telecom wavelengths and traveling at a gold/air interface. By operating a modulated continuous-wave or a Q-switched nanosecond pump laser, we investigate the photo-thermally induced modulation of SPP propagation mediated by the temperature-dependent ohmic losses in the gold film. We use a fiber-to-fiber characterization set-up to measure accurately the modulation depth of the SPP signal under photo-thermal excitation. On the basis of these measurements, we extract the thermo-plasmonic coefficient of the SPP mode defined as the temperature derivative of the SPP damping constant. Next, we introduce a figure of merit which is relevant to characterize the impact of temperature onto the properties of bounded or weakly leaky SPP modes supported by a given metal at a given wavelength. By combining our measurements with tabulated values of the temperature-dependent imaginary part of gold dielectric function, we compute the thermo-optical coefficients (TOC) of gold at telecom wavelengths. Finally, we investigate a pulsed photo-thermal excitation of the SPP in the nanosecond regime. The experimental SPP depth of modulation obtained in this situation are found to be in fair agreement with the modulation depths computed by using our values of gold TOC.

https://hal.archives-ouvertes.fr/hal-00911957/document

Photo-thermal modulation of surface plasmon polariton propagation at telecommunication wavelengths.

An optical waveguide accelerometer based on tunable asymmetrical Fano resonance in a ring-resonator-coupled Mach–Zehnder interferometer (MZI) is proposed and analyzed. A Fano resonance accelerometer has a relatively large workspace of coupling coefficients with high sensitivity, which has potential application in inertial navigation, missile guidance, and attitude control of satellites. Due to the interference between a high-Q resonance pathway and a coherent background pathway, a steep asymmetric line shape is generated, which greatly improves the sensitivity of this accelerometer. The sensitivity of the accelerometer is about 111.75 mW/g. A 393-fold increase in sensitivity is achieved compared with a conventional MZI accelerometer and is approximately equal to the single ring structure.

High sensitivity optical waveguide accelerometer based on Fano resonance

We demonstrate theoretically a tunable optical ring resonator incorporating an asymmetric Mach-Zehnder interferometer (MZI) and two phase shifters. The optimal resonance state of the ring resonator with different geometries can be achieved by tuning the two embedded phase shifters. Distinct intensity and phase responses and transmission spectra characteristics are newly observed by setting different structural parameters such as the asymmetrical path lengths of the waveguides and the coupling ratio of the directional couplers in the MZI. The performance characteristics related to the radius of the ring cavity and the propagation losses in the waveguides are also discussed. At optimal resonance, it is shown that sharp intensity response and tunable narrow-bandwidth spectra can be achieved especially for resonators with a highly asymmetrical configuration. Such device has a potential in sensing, switching and filtering applications.

Tunable Optical Ring Resonator Integrated With Asymmetric Mach–Zehnder Interferometer

We show theoretically plasmonic antennas based on two-step chemical synthesized silver nano-flags constructed by a silver nanowire and a nanoplate. The silver nano-flag antennas exhibit high polarization sensitivity and diversity of spectral signatures dependent on the structural parameters arising from the observed mode competition. With specific configuration engineering, the antennas show controllable electric-field enhancement and ultra narrow bandwidths down to about 2 nm. These nano-antennas promise exciting applications in lasing spaser, optical modulation, and enhanced nonlinear processes.

Controllable plasmonic antennas with ultra narrow bandwidth based on silver nano-flags

The invention relates to an SPPs tunable optical resonance loop filter which is characterized in that an SPPs waveguide is adopted to form an optical loop, thus realizing the SPPs tunable optical resonance loop filter. The filter is integrated with an SPPs tunable direction coupler and an SPPs tunable resonance loop to realize a multi-purpose filter, the resonance frequency, resonance depth and filtering bandwidth of which can be tuned, by tuning the loss of the resonance loop and coupling ratio K of transmission phase and the direction coupler. As a metal core layer of the SPPs waveguide can realize the multiplexing function of opto-electrical signals. The SPPs waveguide tunable optical resonance loop filter proposed in the invention not only can be applied to an integrated optics system, but also can be applied to an integrated opto-electrical hybrid system.

Tunable optical resonance ring wave filter for surface plasmon

Ring resonators integrated with tunable couplers are useful devices in integrated optics systems. The resonant frequency shift characteristic of tunable resonators is theoretically analyzed. It is shown that the resonant frequency shift range is dependent on the configurations and tuning methods of couplers. It provides an analytical explanation of the frequency shift effect by the phase transmission method and the coupled-mode theory (CMT) of asymmetric waveguides. Optimized designs of different kinds of tunable couplers are discussed in order to improve the resonant frequency stability. Moreover, the intensity–phase relationship induced by the resonant frequency shift effect is also discussed, and a more efficient configuration of optical sensors using phase modulation is proposed.

http://iopscience.iop.org/article/10.1088/1464-4258/11/8/085411/pdf

Resonant frequency shift characteristic of integrated optical ring resonators with tunable couplers

Integrated optical ring resonators are essential elemental components for integrated optical circuits. An ultrasmall thermo-optical microring resonator with two bus waveguide-configuration based on surface plasmon polariton waveguide is theoretically analyzed. The thermo-optical coefficient, the temperature-dependent amplitude attenuation coefficient and the temperature distribution properties of the waveguide are investigated numerically by finite element method. The critical resonant conditions of the microring resonator are discussed by considering the propagation losses in the plasmonic ring cavity. The transmission characteristics and the tunability of the ring resonator with different structural parameters are investigated. The results show that the proposed ring resonator with a low driving power and high efficient tunability has potential to develop nano-scope wavelength tunable channel drop filters, low power optical switches, attenuators, and other high compact integrated optical devices.

Tunable microring resonator based on dielectric-loaded surface plasmon polariton waveguides.

A cantilever beam structural resonant-type integrated optical waveguide accelerometer, includes an input waveguide (1), a dissymmetrical structural Mach-Zehnder interferometer (2), a micro-mechanical vibration cantilever beam (3), a short curved waveguide (4) and an output waveguide (5); all the waveguide structures and the cantilever beam use the integrated optical micromachining technique, and the device single-scale integration can be realized by using the temperature-insensitive organic polymer optical waveguide structure and the organic polymer substrate, the key technique indexes such as detection sensitivity, dynamic range are extensively adjusted The phase difference of the optical signal can be measured by detecting the optical intensity of the resonant frequency of the optical circuit so as to achieve high sensitive acceleration detection, and to be free from the effect of the ambient temperature disturbance and waveguide birefringence

Pengqin Wu

Papers

Tunable Optical Ring Resonator Integrated With Asymmetric Mach–Zehnder Interferometer

Tunable optical resonance ring wave filter for surface plasmon

Resonant frequency shift characteristic of integrated optical ring resonators with tunable couplers

Tunable microring resonator based on dielectric-loaded surface plasmon polariton waveguides.

Cantilever beam structural resonant-type integrated optical waveguide accelerometer