Photonic chips are becoming increasingly complex, combining even more optical building blocks on the same chip. With this growing complexity we also see an expanding need for, and use of electrical tuning. This imposes opportunities, as photonic circuits can now become reconfigurable at run time, even to the point of creating arbitrary connectivity between functional building blocks, serving as a general-purpose optical processor. But at the same time, large-scale configurability comes with some tremendous challenges in terms of power consumption, electrical and optical packaging, driver electronics and control algorithms. We will discuss our recent progress in these domains in our path to building general-purpose programmable photonic chips. Expanding silicon photonics with high-efficiency electro-optic tuners, high-density packaging solutions, and electronics and software layers to govern the behavior of these photonic circuits that can be used for both photonic and microwave analog signal processing.
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.
Micro-transfer-printing (µTP) enables the intimate integration of diverse non-inherent functionalities on a target substrate and hence allows for the realization of complex photonic integrated circuits (PICs) with small footprint. By employing a polydimethylsiloxane (PDMS) elastomeric stamp with an array of posts, a large number of micro-components can be integrated on a target wafer in one transfer printing operation, which leads to substantial cost reduction of the resulting PICs. This paper discusses the use of µTP for the realization of III-V lasers on Si and SiN PICs and summarizes the recent progress that has been made in this field.
Transfer printing is an enabling technology for the efficient integration of III-V semiconductor devices on a silicon waveguide circuit. In this paper we discuss the transfer printing of substrate-illuminated III-V C-band photodetectors on a silicon photonic waveguide circuit. The devices were fabricated on an InP substrate, encapsulated and underetched in FeCl3, held in place by photoresist tethers. Using a 2x2 arrayed PDMS stamp with a pitch of 500 μm in x-direction and 250 μm in y-direction the photodiodes were transfer printed onto DVS-BCB-coated SOI waveguide circuits interfaced with grating couplers. 83 out of 84 devices were successfully integrated
Directly interfacing a photonic integrated circuit allows at best an alignment tolerance of a few micrometer due to the small dimensions of optical (coupling) features on chip, but when using microlenses integrated on the substrate-side, alignment tolerances for interfacing the chips can greatly be relaxed. This is demonstrated on a 750 μm thick chip with standard grating couplers (operation wavelength around 1550 nm). Low roughness silicon microlenses were realized by transferring reflowed photoresist into the silicon substrate using reactive ion etching. The microlens allows interfacing the chip from the backside with an expanded beam, drastically increasing lateral alignment tolerances. A 1 dB alignment tolerance of ±8 μm and ±11 μm (along and perpendicular to the grating coupler direction, respectively) was experimentally found when a 40 μm mode field diameter beam was used at the input.
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