Abstract
We theoretically investigate the possible increase of the second harmonic generation (SHG) efficiency in silicon compatible waveguides by considering an asymmetrical plasmonic slot waveguide geometry and a χ((2)) nonlinear polymer infiltrating the slot. The needed phase matching condition is satisfied between the fundamental waveguide mode at the fundamental frequency (FF) and second-order waveguide mode at the second harmonic frequency (SHF) by an appropriate design of the waveguide opto-geometrical parameters. The SHG signal generated in our starting waveguide is three orders of magnitude higher than those previously reported for a FF corresponding to λ = 1550 nm. Then, the SHG performance was further improved by increasing the asymmetry of the structure where nonlinear coupling coefficients as large as 292 psm(-1)W(-1/2) are predicted. The device length is shorter than 20 µm and the normalized SHG conversion efficiency comes up to more than 1 × 10(5) W(-1)cm(-2).
Highlights
Recent years, efficient optical nonlinear effects induced at nanoscale and within short distances have been the hotspot of research and considerably studied for the sake of their key role in future highly-integrated nanophotonic functionalities, such as electro-optic modulation, all-optical signal processing, generation of ultra-short pulses, and ultrafast switching [1, 2]
For the second harmonic generation (SHG) induced in this plasmonic slot waveguide (PSW), the phase matching condition between the fundamental frequency (FF) and second harmonic frequency (SHF) can be satisfied with appropriate designs of the opto-geometrical parameters
Efficient SHG, about three orders of magnitude above the one reported in recent works obtained for LiNbO3-based structures, was demonstrated and the influence of the slot width on SHG efficiency was numerically analyzed
Summary
Efficient optical nonlinear effects induced at nanoscale and within short distances have been the hotspot of research and considerably studied for the sake of their key role in future highly-integrated nanophotonic functionalities, such as electro-optic modulation, all-optical signal processing, generation of ultra-short pulses, and ultrafast switching [1, 2]. In order to further increase the efficiency of SHG and reduce the sizes of devices, plasmonic based nonlinear devices are among the most promising candidates to match this expectation due to the ability to allow strong local-enhanced confinement of light beyond the limits imposed by the laws of diffraction in dielectric media [2, 8, 9]. We propose a second-order nonlinear PSW configuration in hybrid polymer-silicon photonics and choose a NP with high χ(2) as its core nonlinear material. This waveguide is able to tightly confine fields in the subwavelength nonlinear slot both at FF and SHF [24], which is helpful to efficiently reinforce the nonlinear effects.
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