On-Chip Hybrid Photonic-Plasmonic Waveguides with Ultrathin Titanium Nitride Films

Abstract

A solid-state hybrid photonic–plasmonic (HPP) waveguide geometry has been experimentally demonstrated with plasmonic titanium nitride. The configuration is made with robust fabrication techniques, CMOS-compatible materials, and features a straightforward design with dielectric cladding layers that exhibit a significant index mismatch with the substrate. The resulting waveguide is shown to reduce both the propagation loss (0.6 dB/mm) and mode size (7.7 μm) when compared to previously reported long-range surface plasmon polariton (LRSPP) waveguides using both noble metal and alternative metals of similar configurations. In addition, the structure removes the need to match the cladding indices with the substrate index, allowing for a thin film superstrate cladding (∼300 nm) that can be readily deposited using numerous methods. This flexibility allows for additional optimization factors to be considered in the design, such as metal film epitaxy, etching selectivity, device function, and compatibility with subsequent fabrication steps. For example, the top cladding layer can be made of silicon nitride for photonic circuits, a gain medium for loss compensation, as well as lithium niobate or zinc oxide for electrical or optical modulation, without sacrificing performance.

Broadband Ultrafast Dynamics of Refractory Metals: TiN and ZrN

“…Recent work on transition metal nitrides has highlighted their optical properties as alternatives to noble metals employed in plasmonics such as gold (Au). [ 1–9 ] Titanium nitride (TiN), zirconium nitride (ZrN), and other plasmonic nitrides such as hafnium nitride (HfN) and tantalum nitride (TaN) are particularly attractive due to their high melting points that bolster stability at higher ambient temperatures [ 10–12 ] and/or under higher laser irradiation intensities, [ 13–16 ] in addition to their mechanical hardness [ 17,18 ] and complementary metal‐oxide‐semiconductor compatibility. [ 19–21 ] Recent work has demonstrated that TiN shows strong local heating compared to Au, [ 22–24 ] which may be exploited for photothermal therapy, [ 25,26 ] shape‐memory effects, [ 27 ] thermochromic windows, [ 28 ] photoreactions, [ 29–32 ] heat transducers or thermophotovoltaic materials, [ 22,33–37 ] or photodetection.…”

High-bandwidth and high-responsivity waveguide-integrated plasmonic germanium photodetector

“…Recently, another plasmonic waveguide was proposed, the so-called hybrid photonic-plasmonic waveguide, which offers extremely long propagation length. However, the mode confinement exceeds 7 μm so it is not practical for onchip integration [29]. Furthermore, the FoM for this waveguide exceeds other plasmonic waveguides, but it still over 30 times lower compared to the LR-DLSPP waveguide.…”

“…The FoM for LR-DSLPP is at least two orders magnitude higher than other plasmonic waveguide configurations (Table 1) [7,26,29]. Recently, another plasmonic waveguide was proposed, the so-called hybrid photonic-plasmonic waveguide, which offers extremely long propagation length.…”

Nanowires Integrated to Optical Waveguides

“…In this same sense, when placing periodic arrays of metallic nanoparticles on top of dielectric waveguides, the plasmonic chain modes can couple to the photonic modes of the waveguide [8]. These integrated structures give rise to the so-called hybrid photonic-plasmonic waveguide modes [9], and they are the main subject of interest in this chapter. We will focus our attention to integrated structures consisting of periodic arrays of metallic nanowires integrated on top of twodimensional dielectric photonic waveguides.…”