Luxtera and TSMC have jointly developed a new generation 100Gbps/λ-capable silicon photonics platform in a commercial 300 mm CMOS line. We present process details and the performance of the photonic device library.
Silicon photonics has drawn a lot of attention over the last decades, mainly in telecom-related application fields where the nonlinear optical properties of silicon are ignored or minimized. However, silicon’s high χ(3) Kerr optical nonlinearity in sub-micron-scale high-confinement waveguides can enable significant improvements in traditional nonlinear devices, such as for wavelength conversion, and also enable some device applications in quantum optics or for quantum key distribution. In order to establish the viability of silicon photonics in practical applications, some big challenges are to improve the optical performance (e.g., optimize nonlinearity or minimize loss) and integration of optics with microelectronics. In this context, we discuss how electronic PIN diodes improve the performance of wavelength conversion in a microring resonator based four-wave mixing device, which achieves a continuous-wave four-wave mixing conversion efficiency of −21.3 dB at 100 mW pump power, with enough bandwidth for the wavelength conversion of a 10 Gbps signal. In the regime of quantum optics, we describe a coupled microring device that can serve as a tunable source of entangled photon pairs at telecommunications wavelengths, operating at room temperature with a low pump power requirement. By controlling either the optical pump wavelength, or the chip temperature, we show that the output bi-photon spectrum can be varied, with implications on the degree of frequency correlation of the generated quantum state.
Within the ambitious quest for an electrically pumped version of the optical parametric oscillator (OPO), we demonstrate
the first near-infrared integrated OPO in a direct gap semiconductor. This nonlinear device is based on a selectively
oxidized GaAs/AlAs heterostructure, the same “AlOx” technology that is at the heart of VCSEL fabrication. The
heterostructure and waveguide design allows for type-I form-birefringent phase matching, with a TM00 pump around 1 μm and TE00 signal and idler around 2 μm. Relying on the high non-resonant χ(2) of GaAs, relatively weak guided-wave optical losses, and monolithic SiO2/TiO2 dichroic Bragg mirrors, we observe a threshold of 210 mW at degeneracy in the continuous-wave regime, with a single-pass-pump doubly resonant scheme. Further improvement can be achieved by adopting a double-pump-pass scheme and, in a more fundamental way, by further optimizing the waveguide optical
losses. The latter are induced by a not entirely mastered AlAs oxidation process and are of two distinct types: Rayleighlike
scattering at signal and idler wavelength (α ≤ 1cm-1), due to the interface roughness between GaAs and AlOx layers; and absorption at pump wavelengths (α ≈ 3cm-1), due to volume defects in the GaAs layers adjacent to the aluminum oxide. This result marks a milestone for integrated nonlinear photonics and represents a significant step toward the goal of a broadly tunable coherent light source on chip.
The miniaturization of quantum information technology is a subject attracting a growing attention. The exploitation of
spontaneous parametric down conversion in AlGaAs waveguides to generate photon pairs presents several advantages:
high nonlinear susceptibility, room-temperature operation and high emission directionality in the telecom range. In this
work we will present our recent results on three different kinds of AlGaAs devices: a selectively oxidized source based
on form birefringence, a waveguide based on modal phase matching and a microcavity-based source based on
counterpropagating phase matching. We will discuss and compare the figures of merit characterizing the three devices
for quantum communication applications.
Continuously tunable sources with room-temperature operation are required in the mid-infrared region for applications
such as spectroscopy or pollutants monitoring. In this spectral range, optical parametric oscillators (OPOs) are more
versatile than laser diodes.
Guided-wave OPOs constitute a promising perspective, thanks to higher conversion efficiency provided by the
confinement of the interacting waves. While LiNbO3 has been the crystal of choice for a long time, GaAs is a good
alternative thanks to higher nonlinearity, broader transparency range, and optoelectronic integrability. So far, a GaAs
integrated OPO has not yet been demonstrated due to technology induced propagation losses.
Here we present a detailed investigation of the propagation losses in partially oxidized multilayer GaAs/AlAs
waveguides. We have studied the impact of oxidation on the roughness of the multilayer interfaces, via transmission
electron microscopy. While the roughness of our MBE-grown GaAs/AlAs heterostructures is the standard 0.3 nm, it
increases to at least 0.53 nm after AlAs oxidation. Semi-analytical modeling shows that this level of roughness is
responsible for scattering losses, in fair agreement with the measured values. Optimization of the oxidation process is
currently under way with the aim of reaching the OPO oscillation threshold.