The requirements for package-to-package input-output (I/O) interfaces in future high performance computing systems scale up to multiple Terabytes per second. The traditional scaling of I/O’s using electrical links for data transmission faces many bottlenecks such as pin count and bandwidth-distance-power trade-off. The advantages of Si photonics, very high bandwidth and low propagation loss and delay, allow the implementation of in-package optical transceiver modules with a direct interface to CMOS chips by using integrated silicon photonics modulators and detectors. The Si photonic elements are however significantly affected by changes in local and ambient temperature variations, e.g. caused by the highly non-uniform power generation in the ASIC or FPGA CMOS chip, the laser sources, and also the optical devices themselves. Temperature changes can cause a wavelength shift which leads to an optical power loss due to wavelength mismatch and to laser power degradation. The objective of this PhD is to gain fundamental understanding of the thermal behavior of such tightly integrated photonic-electronic systems and to use this insight to develop solutions to limit the impact of temperature fluctuations on the optical transceiver performance.
The first part of the research involves the development of a multi-scale modeling framework to couple the electrical, thermal and optical fields in order to assess the extent of the thermal impact on the optical link between laser, modulator, waveguide and detector. The modeling scales range from the cm-level, including the chip package and the impact of the cooling solution and boundary conditions, down to the µm-level of the integrated optical devices. Finite element simulations will be used to model the temperature distribution and transient temperature changes in the complete package and to extract thermal compact model formulations that can be coupled with electrical and optical compact models. Furthermore, test vehicles will be designed for the validation of the modeling study and for the experimental thermal and optical characterization of the system.
In the second part of the research, the developed modeling framework is applied to reduce the impact of temperature changes, either caused by the environment or by self-heating in the system itself, on the optical performance of the system. A dynamic thermal control strategy for power generation in integrated heaters will be developed to compensate the temperature variations and to maintain a constant temperature of the components. In parallel, solutions will be developed to reduce the temperature sensitivity of the Si photonics module by improving the design of the system, the geometry of the devices and the choice of material combinations.
Required background: mechanics, material science, energy or microtechnology, physics, chemistry
Type of work: 10% literature study, 50% modeling, 30% experimental analysis, 10% reporting in meetings, conferences and journals
Supervisor: Ingrid De Wolf
Daily advisor: Herman Oprins
The reference code for this PhD position is STS1712-23. Mention this reference code on your application form.