Multilevel phase shifters are key components in photonic integrated circuits. A major requirement in many applications is achieving non-volatile operation and low insertion loss simultaneously. Electrically, multiple phase levels can be encoded by controlling the heater power and employing different microheater architectures to induce varying degrees of phase-change material (PCM) amorphization, thereby modulating the device's optical properties and the amplitude and phase of the propagating field. Here, we explore a platform based on the integration of a low-loss PCM, namely GeSe, sandwiched between microheaters and silicon waveguides. To achieve a large number of levels, we modify standard straight microheaters and propose a segmented heater design that breaks the heater's symmetry along the propagation direction. We numerically demonstrate under pulse-width/pulse-amplitude modulation (PWM/PAM) that multilevel phase shifts can be achieved due to non-uniform heating in the GeSe PCM layer. However, the resulting phase levels for the basic configuration are highly abrupt because the constant power dissipation along the light propagation direction, associated with a uniform cross-section, does not permit a wide range of amorphization patterns. The proposed segmented heater, whose width gradually increases in steps along the light propagation direction, allows overcoming this limitation. This configuration enables the encoding of 164 well-spaced phase levels between 0 and π (>7-bit resolution), facilitated by smoother amorphization arising from the combined effects of non-uniform heating across segments and within each segment, while maintaining an insertion loss of only 0.6 dB in the fully crystalline state (worst case).

Global interconnect on interposers between chiplets is currently mostly limited to nearest-neighbor communication. We propose an electro-optical router in 28nm on a photonic interposer to handle queuing and routing between dies and optical link drivers capable of 18ns link setup time for frame-level routing, with 1-to-6 lambda flexible wavelength capacity. Compact analog drivers and standard-cell-based SerDes and clocking achieve 0.007mm2 active area per link and 3.19pJ/b power.

Phase-change material (PCM)-based non-volatile multilevel phase shifters are key components in photonic integrated circuits. Electrically, multiple phase levels can be encoded by controlling the heater power and employing different microheater architectures to induce varying degrees of PCM amorphization. However, encoding a large number of levels is not straightforward. In this work, we first investigate a phase shifter structure based on a GeSe PCM integrated on top of a silicon-on-insulator waveguide, employing a simple rectangular-shaped heater under pulse-width modulation (PWM). We numerically demonstrate that multilevel phase shifts can be achieved because of non-uniform heating in the GeSe PCM layer. However, the resulting phase levels for this basic configuration are highly non-linear because of the uniform power dissipation along the light propagation direction characterized by the same cross-section. To overcome this limitation, we designed a novel PCM-based phase shifter with a segmented heater whose width gradually increases along the light propagation direction. This configuration enables the encoding of hundreds of well-spaced phase levels between 0 and π, facilitated by smoother amorphization arising from the combined effects of non-uniform heating across segments and within each segment, while achieving an insertion loss of only 0.6 dB in the worst case. Furthermore, when evaluating both heater architectures under pulse amplitude modulation (PAM) at a fixed pulse duration, we observe behavior consistent with the trends observed for PWM, confirming the superior performance of the segmented heater design.

To overcome the bandwidth and latency limitations of electrical links, the next breakthrough in high performance computing and data center performance will come through the use of silicon photonics technology thanks to Co-Packaged Optics (CPO) and Optical Network-on-Chip (ONoC) systems. These technologies involve the co-integration of integrated silicon photonic devices and Through Silicon Vias (TSV). This study investigates the mechanical stress induced by by $10 \mu \mathrm{m}$ diameter and $100 \mu \mathrm{m}$ deep copper filled TSVs on the waveguides of a Mach-Zehnder interferometer (MZI). Based on a dedicated analytical model, the optical phase shift measurement has been analyzed and an effective index variation of $0.9 \times 10^{-3}$ was found. This stress measurement approach will be discussed with respect of its perspectives and limitations. This study can lead to improvements in the co-integration density of silicon photonic elements in 3D packaging architectures.

We report the dynamic performance of a heterogeneously integrated III-V-on-SOI distributed feedback quantum well laser (QWL), directly modulated at 1.54 mu m under strong optical feedback. A 28 Gbps data transmission with direct non-return-to-zero modulation using a pseudo-random bit sequence was performed under various optical feedback levels in a back-to-back configuration. The QWL demonstrated robust performance with a power penalty below 1 dB at a bit error rate of 10-3. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

With the rise of optical computing, phase-change materials (PCM) are attractive candidates for implementing programmable optical functionalities in photonic circuits. Integrating them as tunable media in photonic waveguides appears to be a simple but effective way to program their optical transfer function in both amplitude and phase through near-field interactions. This is exactly what is being addressed in this work by integrating Ge2Sb2Te5 (GST) patches on top of silicon waveguides. A scalable fabrication process is described, and the optical properties and programming capabilities are reported obtained from heterodyne interferometry to access the complex transmission of waveguides on the fly. It is reported that both amorphization and crystallization energy thresholds are at least an order of magnitude lower than previous reports, and programming endurance is successfully tested up to 108 cycles, exceeding all previous results obtained with GST or any other PCM for use in photonics. Finally, the morphological and chemical characterization of PCM against aging is presented, revealing a failure mechanism due to phase segregation and ope ning new avenues to further optimize device endurance. As such, these results will be valuable to the large community of scientists seeking to integrate phase-change materials into advanced photonic architectures where reconfigurability is required.

Pierre Noé, Benoît Cluzel, Stéphane Malhouitre, and Benoît Charbonnier, discuss phase change materials for reconfigurable photonic integrated circuits. Phase-change materials (PCMs) have gained increasing interest over the past decade for their potential in photonic applications. This article reviews their properties, key advantages over competing reconfigurable photonic technologies, and the challenges limiting their widespread adoption.

We present a new design of semiconductor mode-locked laser. It is based on a non-uniform DFB cavity engineered to support multiple equi-spaced optical modes. Moreover, we observe that the mode-locked frequency is broadly tunable, unlike traditional mode-locked lasers.

We present a new concept of integrated semiconductor laser providing broad, continuous and potentially fast tunable mode-locked frequency.

We demonstrate an ultra-fast athermal continuous wavelength-swept III-V-on-SOI MOSCAP DFB laser with a mode-hop-free-tuning up to 10 GHz in less than 2 ns. We also propose a new method to linearize the frequency response without any pre-distortion or active feedback in the gain’s current injection ramp. Instead, we polarize the III-V gain Section under direct current injection, and we drive the hybrid MOSCAP waveguide with an AC voltage signal. By optimizing its driving frequency, we demonstrate an ultra-fast athermal triangular-shaped time-varying frequency tuning with a speed of $4\times 10 ^{4}$ PHz/s and a laser’s frequency excursion of 4 GHz.

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 externally modulated widely tunable lasers co-integrated with semiconductor optical amplifiers (SOAs) heterogeneously integrated on silicon. The widely tunable laser enables continuous single-mode operation over a tuning range of approximately 40 nm, with a side-mode suppression ratio (SMSR) of at least 50 dB and an average waveguide-coupled optical power of 5 mW. The integrated electro-absorption modulator (EAM) exhibits an extinction ratio (ER) of 16 dB when reversed biased at -2 V. The bit-error-rate (BER) measurements conducted across the available optical bandwidth (15 nm) showcase error-free transmission at 32 Gbps using non-return-to-zero (NRZ) signals for the majority of wavelengths in a back-to-back (B2B) configuration. Additionally, transmission measurements over distances of up to 10 km through a standard single-mode fiber (SSMF) have been successfully demonstrated. Dynamic extinction ratio (DER) values exceeding 4.5 dB are achieved for all wavelengths. Open-eye diagrams were measured up to 56 Gbps. These results demonstrate that this compact mono-epitaxial externally modulated tunable laser with integrated optical amplification can be a cost-effective transmitter solution for dense wavelength division multiplexing (DWDM) metropolitan and access networks.

The field of Silicon Photonics has experienced a solid and continuous progress over the last few years, gaining in technological maturity, design tools, and new methods [1]. The deployment of low-cost, compact, and power-efficient photonic circuits with a high wafer yield and robustness stands as one of the fundamental pillars that sustain such progress [2]. Presently, photonic circuit technology has diversified its number of available platforms. Despite the fact that indium phosphide (InP) [3] and silicon-on-insulator (SOI) platforms are still considered as the workhorses of integrated photonics in terms of maturity and deployment of active (InP) and passive (SOI) components, other alternatives such as germanium-on-silicon [4], silicon nitride-on-insulator [2] or hybrid solutions combining different functional materials with Si are gaining momentum [5]. A representative example is the heterogeneous III-V/Si platform [6], which has been used to develop compact photonic circuits with on-chip gain. Contrarily to the hybrid integration, the III-V-on-Si heterogeneous integration avoids the constraints of chip-to-chip alignment while enabling the simultaneous integration of hundreds of III-V gain chips in a scalable fashion. Still, the integration methods of such III-V materials on silicon need to be improved to attain the maturity level of the monolithic III-V platform, which benefits from a complete palette of technological solutions not yet available in the III-V-on-Si heterogeneous integration. More recently, an advanced heterogeneous scheme based on wafer-seed-bonding and epitaxial regrowth has emerged [7]–[9]. The ambition is to create a generic integration scheme combining the best offered by the III-V and the Si-photonics platforms. The regrowth capability gives access to the large epitaxial toolkit available in the conventional InP monolithic platform, where several epitaxial steps are often implemented [10][11]. To cite some of them, the epitaxial regrowth of III-V materials to bury III-V lasers bonded onto silicon are object of intense research nowadays to overcome the thermally inefficient buried oxide [12]. In this paper, we will review the advances on III-V-on-Si heterogeneous integration through the implementation of several key demonstrators and building blocks for silicon photonics, including on-chip semiconductor optical amplifiers, lasers and electro-absorption modulators. We will discuss the progress and benefits of the direct seed bonding and regrowth as well as new device designs to improve the performance. References: [1] D. Thomson et al. , “Roadmap on silicon photonics,” J. Opt. , vol. 18, no. 7, p. 73003, 2016, doi: 10.1088/2040-8978/18/7/073003. [2] S. Y. Siew et al. , “Review of Silicon Photonics Technology and Platform Development,” Journal of Lightwave Technology , vol. 39, no. 13. Institute of Electrical and Electronics Engineers Inc., pp. 4374–4389, Jul. 01, 2021, doi: 10.1109/JLT.2021.3066203. [3] M. Smit, K. Williams, and J. Van Der Tol, “Past, present, and future of InP-based photonic integration,” APL Photonics , vol. 4, no. 5, May 2019, doi: 10.1063/1.5087862. [4] J. Chrétien et al. , “GeSn Lasers Covering a Wide Wavelength Range Thanks to Uniaxial Tensile Strain,” ACS Photonics , vol. 6, no. 10, pp. 2462–2469, Oct. 2019, doi: 10.1021/acsphotonics.9b00712. [5] S. Lin et al. , “Efficient, tunable flip-chip-integrated III-V/Si hybrid external-cavity laser array,” Opt. Express , vol. 24, no. 19, p. 21454, Sep. 2016, doi: 10.1364/oe.24.021454. [6] D. Liang and J. E. Bowers, “Recent Progress in Heterogeneous III-V-on-Silicon Photonic Integration,” Light Adv. Manuf. , vol. 2, no. 1, pp. 1–25, 2021, doi: 10.37188/lam.2021.005. [7] K. Takeda, S. Matsuo, T. Fujii, K. Hasebe, T. Sato, and T. Kakitsuka, “Epitaxial growth of InP to bury directly bonded thin active layer on SiO2/Si substrate for fabricating distributed feedback lasers on silicon,” IET Optoelectron. , vol. 9, no. 4, pp. 151–157, 2015, doi: 10.1049/iet-opt.2014.0138. [8] C. Besancon et al. , “AlGaInAs Multi-quantum Well Lasers On Silicon-on-insulator Photonic Integrated Circuits Based On InP-seed-bonding And Epitaxial Regrowth,” Appl. Sci. , vol. 12, no. 1, Jan. 2022, doi: 10.3390/app12010263. [9] Y. Hi et al. , “Electrically-Pumped 1.31 μm MQW Lasers by Direct Epitaxy on Wafer-Bonded InP-on-SOI Substrate,” in Proceedings of 2018 IEEE Photonics Conference (IPC) , 2018, pp. 1–2. [10] V. Rustichelli et al. , “Monolithic integration of buried-heterostructures in a generic integrated photonic foundry process,” IEEE J. Sel. Top. Quantum Electron. , vol. 25, no. 5, Sep. 2019, doi: 10.1109/JSTQE.2019.2927576. [11] F. Lemaître et al. , “96 nm Extended Range Laser Source Using Selective Area Growth,” in European Conference on Optical Communication, ECOC , 2018, doi: 10.1109/ECOC.2018.8535218. [12] C. Besancon et al. , “AlGaInAs Multi-Quantum Well Laser on Silicon Achieved byDirect-Bonding and MOVPE Semi-Insulating Buried Heterostructure Regrowth,” in Compound Semiconductor Week 2023 , Jan. 2023, vol. 12, no. 1, doi: 10.3390/app12010263.

To overpass the bandwidth and the latency limitations of electrical links, the next breakthrough in high performance computing integration will eventually come through photonic technology and Optical Network-on-Chip (ONoC). This work introduces a global architecture of an ONoC and reports the detail integration and fabrication on the 200 mm Leti's platform of a Si photonic interposer on SOI wafers. Active photonic circuit operating at 1310 nm wavelength, $\mathbf{12}\ \boldsymbol{\mu} \mathbf{m}$ diameter $\mathbf{100}\ \boldsymbol{\mu} \mathbf{m}$ height Through Silicon Via (TSV) middle process, four metal layers Back-End Of Line (BEOL) with $\boldsymbol{\mu}-\mathbf{pillars}$ and backside redistribution layer with thermal cavity above heaters have been successfully achieved. Morphological characterizations as cross-sections assess the process developments and integration results. Optical propagation losses measured on Rib and Deep Rib structures and insertion losses on Single Polarization Grating Couplers (SPGC) structures both at the end of the active photonic and after TSV / BEOL processes show no deviation. The TSV middle resistance is evaluated below $\mathbf{22}\ \mathbf{m}\mathbf{\Omega}$ with a yield greater than 95 %. Finally, all individual process blocks required for the functional ONoC system, especially Ring Modulators is discussed regarding their successful optimized co-integration.

Heterogeneous integration of III-V materials on silicon photonics circuits has emerged as an attractive approach to demonstrate compact lasers that address a wide range of applications ranging from short distance data communication to long distance optical transmission. Directly modulated III-V-on-SOI lasers (DML) with high bandwidths such as distributed feedback (DFB) lasers are particularly well suited for those applications that require high optical power and stable single-mode performance [1].