Vacancy: Colloidal Nanocrystal Lasers (Open)

Context

Colloidal Nanocrystals have been heavily investigated for over more than 25 years, crowned with the Nobel Prize in Chemistry in 2023, as interesting optical materials both for their bright emission and their good detection capabilities. Both for spontaneous emission and absorption several applications and products already exist, probably most notable the QLED television made by Samsung. Despite demonstrations of optical gain and lasing already in the year 2000 [1] however, no commercial laser diode exists based on colloidal nanocrystals.
In the Photonics Research Group at Ghent University, Silicon Photonics is heavily investigated as a low-loss, rapidly growing technology. Specifically, we attempt to solve one of its last remaining bottlenecks: the lack of ability to directly grow an efficient emitter on this platform. By heterogeneously integrating different materials on Silicon Photonics, we can combine the best of both worlds and make use of Silicon Photonics' low losses with efficient emitters and/or gain materials.
One of these materials that is being investigated is the use of colloidal nanocrystals. Besides their good optical properties, a big advantage is their solution-processibility. The fact that they can be processed as a liquid allows for extremely cheap and fast integration. In parallel to the integration efforts made by the Photonics Research Group, the Physics and Chemistry Group (PCN), also at Ghent University, has been working on making and studying new colloidal nanocrystals with better gain properties, different wavelength ranges, different morphology and so on. These materials are then used to develop more lasers in the Photonics Research Group. This collaboration has been going on for more than 15 years, and has recently made some great process making use of larger nanocrystals, which boost the gain significantly [2][3][4].
Despite this progress, the initial comment still remains: there is no commercial laser diode available yet based on these materials. We argue that the main reason this is the case is no longer a subpar material, but at this stage the main bottleneck is the photonic integration. There is a need to develop consistent methods, combined with low-loss materials and smart design, to increase the quality of colloidal nanocrystal based devices. This next step of development will be crucial to go to a working product, and is the essence of this project.

Job Description

The task of the Photonics Research Group within the project and hence your task as PhD student relates to the development of a colloidal nanocrystal lasers. It will consist out of exploring various laser designs, both with out-of-plane and in-plane light coupling to tackle various applications. The idea is to use a specific, optimized colloidal nanocrystal material and focus mainly on that so that the priority always remains looking into the optical cavity. The final goal is then to optimize the laser cavities for certain parameters, like smallest size, highest power output, most narrow linewidth, etc

Candidate Profile

You have a master in Photonics, Applied Physics, Microelectronics or similar. You are willing to combine simulation and design, cleanroom fabrication and characterisation

More information

• Contact: Dries Van Thourhout
• [1] Klimov, Victor Ivanovich, et al. "Optical gain and stimulated emission in nanocrystal quantum dots." science 290.5490 (2000): 314-317.
• [2] Tanghe, Ivo, et al. "Optical gain and lasing from bulk cadmium sulfide nanocrystals through bandgap renormalization." Nature Nanotechnology 18.12 (2023): 1423-1429
• [3] Tanghe, Ivo, et al. "Two-dimensional electron hole plasma in colloidal quantum shells enables integrated lasing continuously tunable in the red spectrum." ACS nano 18.22 (2024): 14661-14671

Related research topics

• Integration of colloidal quantum dots with PICs