The interaction between the chiral light and matter is vital to construct on-chip multi-functional photonic circuits. The well-known spin-orbit interaction has obtained significant attention in manipulation of light with different circular polarization states. We propose a robust Y-type surface plasmon nano-waveguide structure to effectively sort spin-dependent photons. The optimized simulation results demonstrated that the waveguide modes excited by circularly polarized light with different spin states can be selectively coupled to one of two branching waveguides, with a unidirectionality efficiency up to 0.95. This research may open up new ways for the on-chip implementation of complex photonic functions, nano-photonic circuits, and nano-optical manipulation.
All-dielectric waveguide modulators nowadays are critical for on-chip photonic circuit’s integration. We propose and theoretically demonstrate a graphene-based all-dielectric waveguide modulator with offset nanowires. The displacement between the nanowires causes the electric field parallel to the graphene to increase, thereby realizing an enhanced field modulation effect. We obtain the best modulation performance by optimizing the structural parameters and changing the offset distance of the nanowires. Analysis of the simulation results indicate that the structure offers a high modulation depth (>0.13 dB / μm) covering the S , C, and L bands. Benefitting from the strong subwavelength confinement and excellent broadband modulation performance, the proposed optical waveguide modulators offer a significant potential to realize various long-wave integrated modulators, interconnects, and optoelectronic devices.
A high sensitivity refractive index (RI) sensor based on a tapered small core singlemode fibre (SCSMF) structure is proposed and developed. By tapering the SCSMF section, this sensor has very high sensitivity around the RI of water. Experimentally we have demonstrated a sensitivity of 1988.5 nm/RIU (RI unit) in the RI range from 1.3325 to 1.3407 by tapering a SCSMF section from a diameter of 125 μm to a diameter of 16 μm. The feasibility of using this type of sensor for biosensing application has also been verified by experiments. This was undertaken using a suitable Fibrinogen antigen surface functionalisation, which successfully showed that the sensor can in principle detect differences in the concentration of a Fibrinogen antibody.
An integrated hybrid waveguide coupled long range surface plasmon polaritons (LRSPPs) biosensor is
proposed and analyzed by the Finite Element Method (FEM). The influence of the structural parameters on the
coupling between the dielectric waveguide (DWG) and LRSPPs modes are numerically investigated.
Simulation results show that the resonant coupling wavelength between the DWG and LRSPPs modes is very
sensitive to small refractive index changes i.e. the estimated sensitivity is as high as 4180 nm/RIU (refractive
index unit). Furthermore, when operating in intensity interrogation, its detection of limit has been shown as
small as 3.7 x 10-7 RIU.
A novel plasmonic biosensor based on coupled metal-dielectric buffer grating is proposed and analyzed by the rigorous
coupled wave analysis (RCWA) method. The metal-dielectric buffer grating structure offers surface plasmon resonance
suitable for high sensitivity biosensing applications. The calculated FWHW (full width at half maximum) of the
transmission peak is 5 nm and the optical transmission efficiency is significantly enhanced at the resonant wavelength of
800.8 nm by introducing the dielectric buffer grating. The highly concentrated field distribution is sensitive to
surrounding refractive index changes of the metal surface providing a sensitivity of 560 nm/RIU (refractive index unit)
for optical biosensing applications.
An enhanced refractive index (RI) sensor with combination of long period fiber grating (LPG) and a small core
singlemode fiber (SCSMF) structure is proposed and developed. Since the LPG and SCSMF transmission spectra
experience a blue and red shift respectively as the surrounding RI (SRI) increases, the sensitivity is improved by
measuring the separation between the resonant wavelengths of the LPG and SCSMF structures. Experimental results
show that the sensor has a sensitivity of 1028 nm/SRI unit in the SRI range from 1.422 to 1.429, which is higher than
individual sensitivities of either structure alone used in the experiment.
In this paper, a novel T-shaped plasmonic metal-insulator-metal (MIM) splitter with one input and two outputs is
proposed, which uses simple stacked Bragg reflectors placed on both the left and right branches. Simulation results
show that the resonance wavelengths of the surface plasmon polaritons (SPPs) can be effectively controlled and
guided along the desired direction with high confinement by properly designing the parameters of the structure, such
as the refractive index of the dielectric, the period and the number of dielectric modulations N. Moreover, the splitting
ratio is found to be adjustable by tuning the value of N.
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