Extending the spectrum of fully integrated photonics to submicrometre wavelengths

Abstract

Integrated photonics has profoundly affected a wide range of technologies underpinning modern society1–4. The ability to fabricate a complete optical system on a chip offers unrivalled scalability, weight, cost and power efficiency5,6. Over the last decade, the progression from pure III–V materials platforms to silicon photonics has significantly broadened the scope of integrated photonics, by combining integrated lasers with the high-volume, advanced fabrication capabilities of the commercial electronics industry7,8. Yet, despite remarkable manufacturing advantages, reliance on silicon-based waveguides currently limits the spectral window available to photonic integrated circuits (PICs). Here, we present a new generation of integrated photonics by directly uniting III–V materials with silicon nitride waveguides on Si wafers. Using this technology, we present a fully integrated PIC at photon energies greater than the bandgap of silicon, demonstrating essential photonic building blocks, including lasers, amplifiers, photodetectors, modulators and passives, all operating at submicrometre wavelengths. Using this platform, we achieve unprecedented coherence and tunability in an integrated laser at short wavelength. Furthermore, by making use of this higher photon energy, we demonstrate superb high-temperature performance and kHz-level fundamental linewidths at elevated temperatures. Given the many potential applications at short wavelengths, the success of this integration strategy unlocks a broad range of new integrated photonics applications.

High-performance Kerr microresonator optical parametric oscillator on a silicon chip

“…1(c)). This equation shows that η max s,i in a χ (3) OPO increases to a maximum value of 0.5 as K p,s,i increase without bound. However, strongly overcoupling the resonator decreases the total Q = ν/ (κ ext + κ int ) of the corresponding cavity mode(s), yielding a less efficient nonlinear enhancement.…”

“…In a χ (3) OPO, pump photons at ν p are converted to up-shifted signal photons (ν s , with ν s > ν p ) and down-shifted idler photons (ν i , with ν i < ν p ) that satisfy energy conservation (2ν p = ν s + ν i ). Appreciable conversion efficiency requires phase-matching, so that 2β p = β s + β i where β p,s,i, is the propagation constant for the pump, signal, and idler modes, respectively.…”

“…Here, we demonstrate a silicon photonics OPO device with unprecedented performance. Our OPO device, based on the third-order (χ (3) ) nonlinearity in a silicon nitride microresonator, produces output signal and idler fields widely separated from each other in frequency ( > 150 THz), and exhibits a pump-toidler conversion efficiency up to 29 % with a corresponding output idler power of > 18 mW on-chip. This performance is achieved by suppressing competitive processes and by strongly overcoupling the output light.…”

“…While integrated photonics lasers are highly developed in the telecommunications band 1 , many of the aforementioned technologies operate at other wavelengths. To this end, the extension of heterogeneously integrated lasers to other bands has been pursued, with recent demonstrations at 980 nm 2,3 and 2000 nm 4 . However, wavelength access across the entirety of a broad spectral range would demand the challenging integration of several material platforms.…”

“…Here, we demonstrate high-performance χ (3) OPO on a silicon microchip. By suppressing competing nonlinear processes that would otherwise saturate parametric gain and by strongly overcoupling the output mode while retaining high overall Q, we simultaneously realize wide spectral separation between the participating modes (signal-idler separation > 150 THz), high conversion efficiency (up to ≈ 29%), and useful output power (up to ≈ 21 mW), a compelling combination of properties that, to the best of our knowledge, has not previously been simultaneously achieved in on-chip OPO.…”