An Ultra-Compact Broadband Polarizing Beam Splitter Utilizing Hybrid Plasmonic Waveguide

Polarizing beam splitter has rather significant applications in polarization diversity circuits and polarization multiplexing systems.In this paper,we present an asymmetric polarizing beam splitter utilizing hybrid plasmonic waveguide.The special hybrid structure with a hybrid waveguide and a dielectric waveguide can limit the energy of TE and TM modes to a different layer.Therefore,we can achieve beam splitting by adjusting the corresponding parameters of the two waveguides.First,we studied the influences of different structure parameters on the real part of the effective mode refractive index of the two waveguides,and obtained a set of parameters that satisfy the condition of strong coupling of TM mode and weak coupling of TE mode.Then,the performance of our proposed polarizing beam splitter is evaluated numerically.The length of the coupling section is only 4.1μm,and the propagation loss of TM and TE modes is 0.0025 d B/μm and 0.0031 d B/μm respectively.Additionally,the extinction ratios of TM and TE modes are 10.62 d B and 12.55 d B,respectively.Particularly,the proposed device has excellent wavelength insensitivity.Over the entire C-band,the fluctuation of the whole normalized output power is less than 0.03.In short,our proposed asymmetric polarizing beam splitter features ultra-compactness,low propagation loss,and broad bandwidth,which would provide promising applications in polarization multiplexing system and polarization diversity circuits relevant to optical interconnection.

A mechanical reliability study of 3-dB waveguide hybrid couplers in submillimeter and terahertz bands

This paper presents a mechanical reliability study of 3-dB waveguide hybrid couplers in submillimeter and terahertz bands.To show the necessity of improving the mechanical properties of the coupler’s branch in submillimeter and terahertz bands,a comprehensive study regarding the displacement of hybrid branch variation with varying width-length ratio and height-length ratio has been completed.In addition,a modified 3-dB waveguide hybrid coupler is designed and presented.Compared with the traditional branch structure,the proposed hybrid consists of a modified middle branch with circular cutouts at the top and bottom on both sides instead of the traditional rectangle branch,which increases the branch size and improves its mechanical reliability while achieving the same performance.Simulation results show that the deformation of the modified hybrid branch is 22%less than those of other traditional structure designs under the same stress.In practice,a vibration experiment is set up to verify the mechanical reliability of hybrid couplers.Measurement results show that the experiment deteriorates the coupling performance.Experimental results verify that the performance of the novel structure coupler is better than that of a traditional structure branch hybrid coupler under the same electrical properties.

A low-threshold nanolaser based on hybrid plasmonic waveguides at the deep subwavelength scale

A novel nanolaser structure based on a hybrid plasmonic waveguide is proposed and investigated. The coupling between the metal nanowire and the high-index semiconductor nanowire with optical gain leads to a strong field enhancement in the air gap region and low propagation loss, which enables the realization of lasing at the deep subwavelength scale.By optimizing the geometric parameters of the structure, a minimal lasing threshold is achieved while maintaining the capacity of ultra-deep subwavelength mode confinement. Compared with the previous coupled nanowire pair based hybrid plasmonic structure, a lower threshold can be obtained with the same geometric parameters. The proposed nanolaser can be integrated into a miniature chip as a nanoscale light source and has the potential to be widely used in optical communication and optical sensing technology.

Hybrid plasmon waveguides with metamaterial substrate and dielectric substrate:A contrastive study

Hybrid plasmon waveguides, respectively, with metamaterial substrate and dielectric substrate are investigated and analyzed contrastively with a numerical finite element method. Basic properties, including propagation length Lp, effective mode area Aeff, and energy distribution, are obtained and compared with waveguide geometric parameters at 1.55 gin. For the waveguide with metamaterial substrate, propagation length Lp increases to several tens of microns and effective mode area Aeff is reduced by more than 3 times. Moreover, the near field region is expanded, leading to potential applications in nanophotonics. Therefore, it could be very helpful for improving the integration density in optical chips and developing functional components on a nanometer scale for all optical integrated circuits.

Tunable coupling of a hybrid plasmonic waveguide consisting of two identical dielectric cylinders and a silver film

The propagation length of surface plasmon polaritons（SPPs） is intrinsically limited by the metallic ohmic loss that is enhanced by the strongly confined electromagnetic field. In this paper, we propose a new class of hybrid plasmonic waveguides（HPWs） that can support long-range SPP propagation while keeping subwavelength optical field confinement. It is shown that the coupling between the waveguides can be well tuned by simply varying the structural parameters. Compared with conventional HPWs, a larger propagation length as well as a better optical field confinement can be simultaneously realized. The proposed structure with better optical performance can be useful for future photonic device design and optical integration research.

Fast response 2×2 thermo-optic switch with polymer/silica hybrid waveguide

A polymer/silica hybrid 2×2 multimode-interference switch is designed and fabricated. Instead of polymer Mach-Zehnder interferometer thermo-optic （TO） silica is used as under-cladding to accelerate heat release because of its large thermal conductivity. The developed switch exhibits low power consumption of 6.2 mW, low crosstalk of about 28 dB, and short response time. The rise and fall times of 103 and 91 its for this hybrid switch are shortened by 40.8% and 52.4%, respectively, compared with those of the fabricated TO switch （174 and 191 μs） using polymer as both upper- and under-claddings.

Hybrid silicon slotted photonic crystal waveguides:how does third order nonlinear performance scale with slow light?

We investigate in this paper the influence of slow light on the balance between the Kerr and two-photon absorption(TPA) processes in silicon slotted hybrid nonlinear waveguides. Three typical silicon photonic waveguide geometries are studied to estimate the influence of the light slow-down factor on the mode field overlap with the silicon region, as well as on the complex effective nonlinear susceptibility. It is found that slotted photonic crystal modes tend to focalize in their hollow core with increasing group index(n_G) values. Considering a hybrid integration of nonlinear polymers in such slotted waveguides, a relative decrease of the TPA process by more factor of 2 is predicted from n_G=10 to n_G=50. As a whole, this work shows that the relative influence of TPA decreases for slotted waveguides operating in the slow light regime, making them a suitable platform for third-order nonlinear optics.

Optical Waveguides from Organic/Inorganic Hybrid Materials

Organic/inorganic material has attracted great attentions because its importance as photonic materials. We report on our recent results on organic/inorganic hybrid sol-gel materials and optical waveguides like splitter, thermo-optic switch and micro-cavity laser.

Polarization-Insensitive Hybrid Plasmonic Waveguide Design for Evanescent Field Absorption Gas Sensor

We propose a polarization-insensitive design of a hybrid plasmonic waveguide(HPWG)optimized at the 3.392µm wavelength which corresponds to the absorption line of methane gas.The waveguide design is capable of providing high mode sensitivity(Smode)and evanescent field ratio(EFR)for both transverse electric(TE)and transverse magnetic(TM)hybrid modes.The modal analysis of the waveguide is performed via 2-dimension(2D)and 3-dimension(3D)finite element methods(FEMs).At optimized waveguide parameters,Smode and EFR of 0.94 and 0.704,can be obtained for the TE hybrid mode,respectively,whereas the TM hybrid mode can offer Smode and EFR of 0.86 and 0.67,respectively.The TE and TM hybrid modes power dissipation of~3 dB can be obtained for a 20-µm-long hybrid plasmonic waveguide at the 60%gas concentration.We believe that the highly sensitive waveguide scheme proposed in this work overcomes the limitation of the polarization controlled light and can be utilized in gas sensing applications.

Nonlinear hybrid plasmonic slot waveguide for second-harmonic generation

A nonlinear hybrid plasmonic slot waveguide composed of periodically poled lithium niobate(PPLN) and two separated silver films is investigated. The e?ective refractive index, propagation length, and energy confinement of the hybrid anti-symmetric mode in this waveguide are calculated using the structure parameters at the fundamental wavelength of λ = 1550 nm and its second harmonic(SH) λ = 775 nm. Through the above indices, coupling e?ciency(maximum SH conversion e?ciency during propagation) and peak position(propagation location of the conversion e?ciency) of SH generation are analyzed. Finally, higher conversion e?ciency can be achieved at a shorter propagation distance by changing the waveguide into a tapered structure.

Energy intensity analysis of modes in hybrid plasmonic waveguide

A hybrid plasmonic waveguide containing silicon core, silver cap and ultra-thin sandwiched SiO2 layer is studied. By analyzing the mode distribution patterns and the curves of mode effective index, we show how the plasmonic mode around the metal surface is coupled with the fundamental mode in the silicon core to form a squeezed hybrid mode. The ability of the hybrid plasmonic waveguide in energy confinement is also discussed quantitatively.

Efficient second harmonic generation in silicon covered lithium niobate waveguides

We theoretically propose a hybrid lithium niobate(LN) thin-film waveguide that consists of an amorphous silicon stripe and etch-free z-cut LN for highly efficient wavelength conversion, circumventing the challenging etching on LN material.Profiting from the spatial symmetry breaking of the waveguide, the asymmetric hybrid modes can spontaneously achieve phase matching with small modal area and large spatial mode overlap, enabling enhanced second harmonic generation with a normalized conversion efficiency over 3900% W^(-1)· cm^(-2)(0.5-mm-long propagation distance). The choice of integrating silicon with LN alleviates the fabrication challenge, making the platform potentially compatible with silicon photonics.