Subjects

- Integrated optics

- Nonlinear optics

- Optical materials and structures

Abstract

The photonics landscape encompasses a wide scope of material platforms, each optimized for specific functionalities, yet no platform meets the demands of all current and evolving photonic applications. Although combining integrated-photonics materials enhances overall capability, such as unifying nonlinear optics, low-loss passive devices and electro-optics, material and process compatibility remains a major challenge. Here we introduce full-wafer, monolithic 3D integration of tantalum pentoxide (Ta2O5, hereafter tantala1) photonics directly onto a patterned substrate, demonstrated here with thin-film lithium niobate2. Tantala’s unique properties, importantly room-temperature deposition, moderate-temperature annealing and low residual stress in thick films optimized for phase matching, make it well suited for monolithic 3D integration without compromising substrate performance or compatibility. We demonstrate low-loss, high-quality-factor microresonators and nanophotonics in tantala, robust quasi-phase-matching in poled lithium niobate waveguides3, and efficient 3D interlayer routing. These capabilities enable us to demonstrate a rich palette of nonlinear frequency conversion processes, including χ(3) four-wave mixing for supercontinuum generation, optical parametric oscillation and dark-pulse microcomb generation in tantala microresonators and photonic crystal resonators, χ(2) second-harmonic generation in periodically poled lithium niobate, and combinations thereof.

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Fig. 1: Monolithic 3D integration of tantala photonics on patterned substrates.

Fig. 2: Tantala–LN fabrication, tantala material properties and microresonator Q.

Fig. 3: Tantala–LN interlayer routing and SHG.

Fig. 4: Tantala–LN χ(3)/χ(2) designs and demonstrations.

Data availability

The data necessary to evaluate the conclusions of this work are provided in the paper. Requests can be accommodated by contacting the corresponding author.

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Monolithic 3D integration of tantalum pentoxide nonlinear photonics | Nature