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We propose and demonstrate a mode-division-multiplexed transmitter by employing a VCSEL-based 2-D matrix and a multi-plane light converter (MPLC). The triangular matrix light spots from VCSELs are designed with a 250-μ pitch in both x- and y- directions for scalable and low-loss mode multiplexing. The VCSELs are directly modulated by co-packaged BiCMOS drivers on a silicon interposer, fabricated on a wafer level. The MPLC is utilized to form seven phase masks to convert the individual Gaussian beams to multiplex Hermite-Gaussian modes, which can be coupled into a multi-mode fiber. In the demonstration, we packaged ten 10-G class VCSELs with the drivers, and the form factor of the co-packaged optics is 10-mm × 10-mm. With the fan-out evaluation board, the sub-module is characterized for short and long transmissions by multiplexing the ten directly modulated outputs from VCSELs. The testing results indicate 200-Gb/s capacity over 100-m MMF with direct detection and 28-km few-mode fiber with coherent detection.

We design an optical interface system for vertically coupling between Vertical-Cavity Surface-Emitting Lasers and 3-μm silicon waveguides. The system includes a photoresist lens and a total internal reflection mirror, which allows for passive alignment and flip-chip bonding of VCSELs. The simulated coupling loss is 0.7dB, in optimal conditions, which increases to 1 dB when 3-μm and 20-μm alignment tolerances are considered in lateral and longitudinal directions, respectively. The system is built by post-processing lens and metallic wiring on the backside of a 3-μm silicon photonic platform. After flip-chip bonding and embedding of the VCSELs, the system performance is characterized, and VCSEL-to-waveguide coupling efficiency of -7.5 dB is obtained.

At IMAPS2021, we reported on 1-dimensional VCSEL arrays and the packaging technology developed for these arrays, but this time we present the manufacturing workflow and look at the challenges presented by the packaging of special long-wavelength 2-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays in various dimensions. We will show that available packaging technologies for epoxy application by silk screening, die- and wire bonding can be adapted for the unique properties of the 2D VCSEL arrays, delivering high accuracy for production with great overall yield. Proof of the excellent reliability and lifetime will be given through mechanical and electro-optical testing results. The technologies developed for 2D laser arrays will enable new devices for various new applications like high channel count interconnects for data communication and high power VCSEL solutions for 3D sensing. The perfected wire bonding process secured a homogeneous monometallic structure of the wire bonds, a reduced, well defined bond loop height, with sufficient clearance of the bonding wire above the VCSEL surface. Properly set-up manufacturing procedures for the packaging of the VCSEL arrays are necessary to achieve high performance and reliability of the products presented. Processing of large 2D-VCSEL arrays will be part of the paper. 2D arrays have enabled VCSEL technologies to address a wide range of new laser-based sensing applications. VCSEL products vary from laser chips with only a few emitters for proximity sensors up to several thousands of emitters for LiDAR systems. Applications include systems for the automotive, industrial, medical and consumer markets. There is a strong and growing market opportunity for long wavelengths VCSELs, e.g. based on InP material enabling single mode and multi-mode 2D-VCSEL arrays from 1.3 to beyond 2 µm. For 3D sensing systems and free-space optical communication, long wavelength 2D-VCSEL arrays offer improved eye safety and further benefits. The long wavelength VCSELs discussed in this paper can be deployed in a wide range of sensing and optical communication applications.

In this paper we present an optimized manufacturing technique for special long-wavelength 1-dimensional and 2-dimensional Vertical Cavity Surface Emitting Laser Diode (VCSEL) arrays with focus on die bonding and a special wire bonding process as well as additional possibilities to make the manufacturing more productive and to increase the product quality, reliability, and life time. VCSEL arrays have a very broad application potential. Objective of this paper is the development of an assembly technology for long-wavelength VCSEL arrays with high positioning accuracy for automated production with high total yield, using gold-based conductive glue (because silver migration is a concern) securing high yield and extremely high reliability and lifetime. Due to special customer requirements, a final thickness of the conductive glue of 35 micron with low standard deviation is necessary. For highest reliability, gold wire bonding of the top side contact of the VCSEL to a silicon substrate with gold metallization has been a customer requirement. With the described technique we develop and produce customer specific products with dedicated wavelength, performance, and packaging options. Bases on our findings, very flexible and scalable solutions are possible, matching many different applications. Finally, we will present an overview of our results on the physical and electro-optical characterization of the VCSEL devices. This yielded a very productive manufacturing technique, meeting the requirements mentioned above. Special design features of the VCSEL ensure that the relatively high thermal resistance of the cured conductive glue layer does not impair the electro-optical properties or the lifetime of the VCSELs. For the interconnection of the top side contact we used gold wire with 20 microns diameter, using ball-wedge, Stand-Off Stich Bond process with special loop geometry, required by the customer. Due to the properties of the semiconductor material of the VCSELs a low bonding temperature is required, enabled by our special wire bonding process. Gold wire bonding delivered excellent results, by far exceeding the customer specification. The optical spectrum of the VCSELs and other measurements indicate that the assembly processes do not harm the laser diodes or their electro-optical properties. All customer requirements for the 1-dimensional and 2-dimensional VCSEL arrays have been met. The electro-optical and burn-in data furnished proof of the quality of the engineered assembly technology. The technologies developed for low current as well as high current laser arrays will enable new devices for a huge amount of new applications because of the novel manufacturing processes as well as innovative packaging of the VCSEL arrays.

An example of continue breakthrough in Silicon Photonics (SiPh) is heterogeneous integration of active devices at wafer level not just to overcome the natural band-gap limit of the Silicon, but more importantly to exploit its high level of integration, significantly reducing packaging costs while driving down the cost of optical communications. In this paper, we describe a powerful combination and coupling of integrated 45°up-reflecting mirrors with longwavelength InP vertical cavity surface emitting lasers (VCSELs) used to develop a TX module with aggregated capacity up to 2-Tb/s capacity. The Photonic Integrated Circuit (PIC) designed and developed under the H2020 research project PASSION, heterogeneously embeds 40 VCSELs covering the C band on a single 3μm -thick Silicon-On-Insulator (SOI) multiplexer chip. The PIC exit-waveguide is also terminated with an up-reflective mirror and coupled with a fiber optic- based periscope, minimizing the form-factor while improving mechanical reliability of the overall packaged module. VCSELs are directly modulated with Discrete Multi-Tone (DMT) modulation format allowing 50 Gb/s rate per VCSEL. The PIC dimension is about 20 x 20 sqmm and power consumption < 5 pJ/bit at 2Tb/s. A Land Grid Array (LGA) interposer hosting the PIC sorrounded by 40 (flip-chip bonded) linear VCSEL drivers, providing electrical and thermal decoupling to the PIC is also described, achieving a compact and a thermally efficient packaging solution. Conveniently, a modular approach is pursued using the same identical 2-Tb/s TX module when building up a supermodule enabling an aggregating capacity up to 16 Tb/s on a single polarization state.

We demonstrate the coexistence of 100G-200G OTN channels with a novel transmitter technology based on directly modulated VCSELs exploiting DMT. Multi-Tb/s transmission is achieved in links typical of the metro network.

A mode-multiplexed transmitter combining a 2-D VCSEL matrix on a Si interposer and a multi-plane light converter is demonstrated. This enables 200-Gb/s transmission using 10G-class VCSELs over 100-m multimode fiber with direct detection and 28-km few-mode fiber with coherent detection.

To deal with the challenging requirements of metropolitan area networks (MANs), it is essential to design cost-effective systems that can support high capacity and dynamic adaptation, as well as a synergy of programmability and efficient photonic technologies. This becomes crucial for very large MANs that support 5G, where multihop connections will need to be dynamically established at target capacities beyond Tb/s. Programmability, automation, and modularity of network elements are key desired features. In this work, a modular photonic system, programmable via a software-defined networking platform, designed for dynamic 5G-supportive MANs, is described and analyzed. We consider modular sliceable bandwidth/bit rate variable transceivers (S-BVTs) based on vertical-cavity surface-emitting laser (VCSEL) technology and dense photonic integration. The proposed system and its programmability are experimentally assessed using a VCSEL with 10 GHz bandwidth. The experiments are performed over connections as long as six-hop and 160 km, from low-level aggregation nodes to metro-core nodes, thereby enabling IP off-loading. Furthermore, a numerical model is derived to estimate the performance when adopting higher bandwidth VCSELs ( ≥ 18 G H z ) and integrated coherent receivers, as targeted in the proposed system. The analysis is performed for both 50 GHz and 25 GHz granularities. In the former case, 50 Gb/s capacity per flow can be supported over the targeted connections, for optical signal-to-noise ratio values above 26 dB. When the granularity is 25 GHz, the filter narrowing effect severely impacts the performance. Nevertheless, 1.2 Tb/s capacity (scalable to higher values if spectral/spatial dimensions are exploited) can be achieved when configuring the S-BVT to enable 40 VCSEL flows. This confirms that the system is promising to support Tb/s connections in future agile MANs.

A sustainable transmitter enabling multi Tb/s capacity is designed and realized in a silicon photonics platform exploiting the benefits of InP VCSEL sources in terms of cost, power consumption and footprint. 40 VCSELs covering the C band integrated together in a single module achieve 2 Tb/s transmission rate thanks to DMT modulation format. © VDE VERLAG GMBH · Berlin · Offenbach., This paper is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement PASSION No 780326. © 2021, IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work.

The effect of SOA-based MAN node crossing on DMT high-capacity transmission is experimentally evaluated. A capacity of more than 50 Gb/s per channel is demonstrated for a multi-hop multi-channel transmission up to 116 km SSMF.

The high capacity demand, to support broadband services and everything-to-internet connectivity is pushing the limits of both access and metro networks, requiring the adoption of novel strategies for the optical transceiver modules. This represents an opportunity for the adoption in these network scenarios of novel photonic technologies based on single-mode vertical cavity surface emitting lasers (VCSELs) at long wavelengths. On one hand, the access network evolution requires a line rate increase beyond 10 Gb/s, targeting 50 Gb/s propagation in passive optical networks (PONs) over a few tens of kms in standard single mode fiber (SSMF) with simple, cost effective and energy efficient transceivers. On the other hand, the future metropolitan area network (MAN) will need to handle multi-Tb/s traffic in a very dynamic scenario, over variable distances up to hundreds of kms while promoting sustainability, reducing the CapEx and OpEx costs and power consumption. Both needs can be fulfilled by adopting VCSEL direct modulation with multicarrier modulation formats such as discrete multitone (DMT), in combination with distinct transmitter architectures and receiver solutions to support different aggregate capacity requirements and transmission reaches. In any case DMT with bit/power loading enables flexible rate and adaptive distance for metro network applications and link adaptation and PON resource usage optimization for future access networks. In this work, we report our recent results on the adoption of VCSEL technology in both scenarios, with special focus on the receiver and transmitter adopted architectures.

C-band InP vertical cavity surface emitting laser (VCSEL) exploitation can be appealing also for high-capacity transmission over hundreds of kilometres. Long-wavelength VCSELs can represent an alternative solution for the development of transmitters with reduced cost, power consumption and footprint by adopting direct modulation (DM) and single sideband (SSB) discrete multitone (DMT) modulation to achieve dense wavelength division multiplexing (WDM) granularity. Due to numerous hops between nodes inside metropolitan area networks the effect of filtering can severely impact the transmission performance. We present preliminary experimental assessments of DM VCSEL sources with multi-carrier modulation formats, for more than 50 Gb/s per-channel transmission to target a metro network including nodes, handling 25-GHz granularity.