The integration of active devices such as lasers, modulators or photodetectors on silicon photonics platforms has enabled the development of efficient, performant, low-cost and scalable high-speed integrated transceivers for optical communications. In this invited contribution, we will review the most relevant work in the field so far and we will present our recent progress on high-speed integrated transceivers for silicon photonics. The most relevant figures of merit for integrated lasers and electro-absorption modulators for high-speed optical communications will be discussed, as well as our vision for future developments.
We demonstrate a III-V-on-silicon-nitride mode-locked laser through the heterogeneous integration of a semiconductor optical amplifier on a passive silicon nitride cavity using the technique of micro-transfer printing. Specifically, we explore the impact of the gain voltage and saturable absorber current on the locking stability of a tunable mode-locked laser. By manipulating these parameters, we demonstrate the control of the optical spectrum across a wide range of wavelengths spanning from 1530 nm to 1580 nm. Furthermore, we implement an optimization approach based on a Monte Carlo analysis aimed at enhancing the mode overlap within the gain region. This adjustment enables the achievement of a laser emitting a 23 nm wide spectrum while maintaining a defined 10 dB bandwidth for a pulse repetition rate of 3 GHz.
Tunable lasers and photonic integrated circuits are a promising technology to provide compact and high performance solutions for coherent remote sensing applications such as Lidar, and distributed acoustic fiber sensing (DAS). A hybrid tunable laser was fabricated within the EU funded INSPIRE project, based on the micro-transfer printing of a pre-fabricated InP gain section on the IMEC low-loss silicon nitride platform. By simultaneously modulating the laser SOA current and Vernier ring resonators, we demonstrate a 20 GHz chirp amplitude, while maintaining a <5 kHz linewidth. DAS measurement with this laser are presented.
In this paper we present the developments carried out at III-V lab in collaboration with CEA-Leti on the hybrid integration of III-V chips with ultra-low-loss silicon nitride circuits for optical detection and RF systems. Different types of hybrid circuits will be presented: 1- a narrow linewidth laser based on the combination of an InP R-SOA and a long Bragg grating on SiN, 2- a Kerr frequency comb based on a high-power InP DFB laser butt-coupled to a high-Q SiN micro-ring, 3- a long cavity mode-locked laser based on an R-SOA and a SiN circuit with a delay line and a Bragg grating.
We will present our design strategies adopted to boost the performance of heterogeneously integrated III-V-on-Si quantum well lasers for optical communications. For that, we will revisit our recent work on the co-integration of dual-ring widely tunable lasers with semiconductor optical amplifiers on a silicon photonic platform. Also, we will present a nanosecond-tunable capacitive III-V-on-Si distributed feedback laser able to continuously tune its emission wavelength over a 10 GHz span in only 2 ns. Finally, we will show our latest results on low-k distributed feedback lasers with backside sample gratings, showing a high output power and a low laser linewidth.
We review our work on integrated lasers for optical communications. An InP-based multilayer stack containing Al-based quantum wells with optical gain in the telecom window is bonded onto a silicon-on-insulator wafer with patterned photonic circuits and cavities. Ring-based widely tunable lasers and narrow linewidth DFB lasers are demonstrated.
In the frame of the H2020 PICTURE project, we designed and developed densely integrated photonic devices and transceiver (TRx) circuits for high bit-rate telecom and datacom applications. We implemented a process with four different InP-based dies bonded on SOI wafers. With one sole back-end processing run, we achieved the fabrication of multiple components of the complex TRx circuits, and many building block devices, such as III-V/Si SOAs & Fabry-Perot lasers, photodiodes or fast tunable capacitive DFB lasers. First testing of these devices shows promising results. 13dBm-saturation power SOAs and less than 2ns-tuning time capacitive DFB lasers were fabricated and demonstrated.
In this work, we present an advanced heterogeneous integration scheme which consists in integrating a thin InP layer by
wafer-bonding onto a silicon wafer (InPoSi) on which a regrowth step of III-V materials is implemented. Vertical p-i-n
AlGaInAs lasers obtained from a single Selective Area Growth (SAG) step on InPoSi were fabricated. Thanks to SAG,
the AlGaInAs-MQW structures successfully cover a PL range of 160 nm in the C+L band. Based on these structures, a 5-
channel laser array was fabricated. The latter successfully covers a 155 nm-wide spectral band from 1515 nm to 1670 nm
with a maximum output power of 20 mW under continuous-wave regime at 20°C. High thermal stability up to 70°C is
demonstrated with a characteristic temperature of 69°C for the lasers emitting from 1515 nm to 1600 nm.
We present an innovative approach for the growth of crystalline silicon on GaAs using plasma-enhanced chemical vapor deposition (PECVD). In this process the substrate is kept at low temperature (175 °C) and epitaxial growth is obtained via the impact of charged silicon clusters which are accelerated towards the substrate by the plasma-potential and melt upon impact. Therefore, this is a nanometer size epitaxial process where the local temperature (nm scale) rises above the melting temperature of silicon for extremely short times (in the range from ps to ns). This allows obtaining epitaxial growth even on relatively rough GaAs films, which have been cleaned in-situ using a SiF4 plasma etching. We present in-plane X-Ray Diffraction (XRD) measurements which are consistent with the hypothesis that the epitaxial growth happens at a local high temperature. Indeed, the tetragonal structure observed and the low in-plane lattice parameter determined from XRD can only be explained by the thermal mismatch induced by a high growth temperature. The effect of the plasma on the underlying GaAs properties, in particular the formation of hydrogen complexes with GaAs dopants (C, Si, Te) is studied in view of the integration of the c-Si epi-layers into devices.
We fabricated (n) c-Si/ (p) GaAs heterojunctions, by combining low temperature (∼175°C) RF-PECVD for Si and metal organic vapor phase epitaxy for GaAs, aiming at producing hybrid tunnel junctions for Si/III-V tandem solar cells. The electrical properties of these heterojunctions were measured and compared to that of a reference III-V tunnel junction. Several challenges in the fabrication of such heterostructures were identified and we especially focused in this study on the impact of atomic hydrogen present in the plasma used for the deposition of silicon on p-doped GaAs doping level. The obtained results show that hydrogenation by H2 plasma strongly reduces the doping level at the surface of the GaAs:C grown film. Thirty seconds of H2 plasma exposition at 175°C are sufficient to reduce the GaAs film doping level from 1×1020 cm−3 to <1×1019 cm−3 at the surface and over a depth of about 20 nm. Such strong reduction of the doping level is critical for the performance of the tunnel junction. However, the doping level can be fully recovered after annealing at 350°C.
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