Conventional photonic integration technologies are inevitably substrate-dependent, as different substrate platforms stipulate vastly different device fabrication methods and processing compatibility requirements. Here we capitalize on the unique monolithic integration capacity of composition-engineered non-silicate glass materials (amorphous chalcogenides and transition metal oxides) to enable multifunctional, multi-layer photonic integration on virtually any technically important substrate platforms. We show that high-index glass film deposition and device fabrication can be performed at low temperatures (< 250 °C) without compromising their low loss characteristics, and is thus fully compatible with monolithic integration on a broad range of substrates including semiconductors, plastics, textiles, and metals. Application of the technology is highlighted through three examples: demonstration of high-performance mid-IR photonic sensors on fluoride crystals, direct fabrication of photonic structures on graphene, and 3-D photonic integration on flexible plastic substrates.
Mid-infrared (MIR, 2-6 μm wavelength) transparent metal oxides are attractive materials for planar integrated photonic devices for sensing applications. In this study, we present reactive sputtering deposited ZrO<sub>2</sub>-TiO<sub>2</sub> (ZTO) thin films as a new material candidate for integrated MIR photonics. We demonstrate that amorphous ZTO thin films can be achieved with Ti concentration of 40 at.%. With increasing Ti concentration, the optical band gap decreases monotonically from 4.34 eV to 4.11 eV, while the index of refraction increases from 2.14 to 2.24 at 1 μm wavelength. MIR micro-disk resonators on MgO substrates are demonstrated using Ge<sub>23</sub>/Sb<sub>7</sub>S<sub>70</sub>/Zr<sub>0.6</sub>Ti<sub>0.4</sub>O<sub>2</sub> strip-loaded waveguides with a loaded quality factor of ~11,000 at 5.2 μm wavelength. By comparing with a reference device of Ge<sub>23</sub>Sb<sub>7</sub>S<sub>70</sub> resonator on MgO and simulating the optical confinement factors, the ZTO thin film loss is estimated to be below 10 dB/cm. Single mode shallow ridge waveguides with a ridge height of 400 nm and a slab height of 1.7 μm are also demonstrated using ZrO<sub>2</sub> thin films on MgO substrates. The low loss, relatively high index of refraction, superior stability and proven CMOS compatibility of ZTO thin films make them highly attractive for MIR integrated photonics.
A high bandwidth density chip-to-chip optical interconnect architecture is analyzed. The interconnect design leverages
our recently developed flexible substrate integration technology to circumvent the optical alignment requirement during
packaging. Initial experimental results on fabrication and characterization of the flexible photonic platform are also
High-index-contrast optical devices form the backbone of densely integrated photonic circuits. While these devices are
traditionally fabricated using lithography and etching, their performance is often limited by defects and sidewall
roughness arising from fabrication imperfections. This paper reports a versatile, roll-to-roll and backend compatible
technique for the fabrication of high-performance, high-index-contrast photonic structures in composition-engineered
chalcogenide glass (ChG) thin films. Thin film ChG have emerged as important materials for photonic applications due
to their high refractive index, excellent transparency in the infrared and large Kerr non-linearity. Both thermally
evaporated and solution processed As-Se thin films are successfully employed to imprint waveguides and micro-ring
resonators with high replicability and low surface roughness (0.9 nm). The micro-ring resonators exhibit an ultra-high
quality-factor of 4 × 10<sup>5</sup> near 1550 nm wavelength, which represents the highest value reported in ChG micro-ring
resonators. Furthermore, sub-micron nanoimprint of ChG films on non-planar plastic substrates is demonstrated, which
establishes the method as a facile route for monolithic fabrication of high-index-contrast devices on a wide array of
Chalcogenide glasses, namely the amorphous compounds containing sulfur, selenium, and/or tellurium, have emerged as a promising material candidate for mid-infrared integrated photonics given their wide optical transparency window, high linear and nonlinear indices, as well as their capacity for monolithic integration on a wide array of substrates. Exploiting these unique features of the material, we demonstrated high-index-contrast, waveguide-coupled As2Se3 chalcogenide glass resonators monolithically integrated on silicon with a high intrinsic quality factor of 2 × 10<sup>5</sup> at 5.2 micron wavelength, and what we believe to be the first waveguide photonic crystal cavity operating in the mid-infrared.
Chalcogenide glasses, namely the amorphous compounds containing sulfur, selenium, and/or tellurium, have emerged as a promising material candidate for integrated photonics given their wide infrared transparency window, low processing temperature, almost infinite capacity for composition alloying, as well as high linear and nonlinear indices. Here we present the fabrication and characterization of chalcogenide glass based photonic devices integrated on silicon as well as on flexible polymer substrates for mid-IR sensing, optical interconnect and nonlinear optics applications.
Chalcogenide glasses, namely the amorphous compounds containing sulfur, selenium, and/or tellurium, have emerged as
a promising material candidate for integrated photonics given their wide infrared transparency window, low processing
temperature, almost infinite capacity for composition alloying, as well as high linear and nonlinear indices. Here we
present the fabrication and characterization of chalcogenide glass based photonic devices integrated on silicon as well as
on flexible polymer substrates for sensing, optical interconnect and nonlinear optics applications.