Ring modulators for silicon photonic (SiPho) optical transceivers are extremely thermally sensitive and require thermal tuning for stable operation. This tuning is achieved with integrated heaters and in this work two aspects of the heaters are investigated: firstly, how to thermally model the heater-waveguide system in a SiPho ring modulator. Secondly, how to improve the energy efficiency by adapting the design in order to minimize the thermal tuning power consumed by the heater. Silicon substrate undercut (UCUT) is done in order to achieve out-of-plane thermal isolation and prevent heat flow directly into the Si substrate below the device. Introducing the UCUT increases the heater efficiency (η h ) with a factor X3.08. It is shown that the influence of the UCUT cross section on the heater efficiency can be neglected, only the total area and metals significantly influence the thermal behaviour. Comparison between electro-thermal and pure thermal simulation shows very similar behaviour. Finally, the UCUT causes an increase in thermal time constant with factor X3.68.

InP DFB lasers are flip-chip bonded to 300 mm Si photonic wafers using a pick-and-place tool with an advanced vision system, realizing high-precision and high-throughput passive assembly. By careful co-design of the InP-Si Photonics electrical, optical and mechanical interface, as well as dedicated alignment fiducials, sub-300 nm post-bonding alignment precision is realized in a 25 s cycle time. Optical coupling losses of −1.5±−0.5 dB are achieved at 1550 nm wavelength after epoxy underfill, with up to 40 mW of optical power coupled to the SiN waveguides on the Si photonics wafer. The bonding interface adds less than 10% to the series resistance of the laser diodes and post-bonding thermal resistance is measured to be 76 K/W (or 27 K.mm/W), mostly dominated by heat spreading resistance in the InP lasers as suggested by in-depth thermal modeling. Although the assembled lasers suffer from significant, unintentional optical backreflection

Thermal modelling of photonic integrated circuits (PICs) is required for circuit design and for the development of thermal control algorithms. In this work, we present a methodology for obtaining a compact dynamic thermal RC-model of a PIC. PICs are sensitive to thermal coupling, and in this paper it is shown that traditional resistive coupling does not suffice and a new coupling method is derived. The case study to which the new methodology is applied, is a dense wavelength division multiplexing ring filter with 8 channels. With the obtained RCmodel, computational time is reduced from 5.5 hours for finite element simulation to <1 second for a single step response. Using the compact model, circuit-level analysis of frequency response is carried out. Because of its high computational efficiency, the compact model opens possibilities of simulating thermal tuning algorithms.