Wide bandgap optoelectronics

Our research interests encompasses III-nitride lasers and light-emitting diodes, with a focus on nanostructuring for new optical functionality and thin-film devices enabled by electrochemical etching.
A strong focus is on vertical-cavity surface-emitting lasers (VCSELs) where we have identified and proposed schemes to combat a large optical loss mechanism, which has contributed to today’s state-of-the-art devices. High-contrast gratings have been implemented to demonstrate blue VCSELs with built-in polarization selection and more recently nanostructures for optical engineering have enabled ultraviolet photonic crystal surface-emitting lasers (PCSELs).
The boundaries on what can be selectively etched has been pushed by electrochemical etching, which led to the demonstration of the world’s shortest emission wavelength from a VCSEL at the time at 300 nm. This etch technique have also resulted in UVC VCSELs emitting at 276 nm with an accurate cavity length control.

Master students

Nelson Rebelo

Post-docs

Michael Bergmann

PhD students

Filip Hjort “Ultraviolet vertical-cavity surface-emitting lasers and vertical microcavities for blue lasers”​, PhD. 2021. Present affiliation: NVIDIA

Michael Bergmann, “Thin-film ultraviolet light-emitting diodes realized by electrochemical etching of AlGaN”​, PhD. 2020. Present affiliation, Chalmers University of Technology​

Ehsan Hashemi, “Optical Guiding and Feedback in Gallium Nitride Based Vertical Cavity Surface Emitting Lasers”, PhD 2016. Present affiliation: Tobii​

Martin Stattin, “Elements of AlGaN-Based Light Emitters” PhD 2013. Present affiliation: II-VI​

Master students

Erik Strandberg, “Design of a photonic-crystal surface-emitting laser for emission in the ultra-violet”, 2021

Mahdi Mohajeri​​, ”Fabrication of high-reflectivity HfO2/SiO2 distributed Bragg reflectors for UVC VCSELs”, 2020

Lars Persson, ”Thermal and optical simulations of blue- and UV-emitting vertical-cavity surface-emitting lasers”, 2020

Giulia Cardinali , ” Thermal management of ultraviolet LEDs and VCSELs: computer-aided multiphysics optimization”, 2019

Saeed Taheri, “Probing optical properties of nano-structured materials by measuring micro-reflectivity spectrum”, 2018

Marcus Bengths, “Design of nanowire-based vertical-cavity surface-emitting lasers”​, 2018

Filip Hjort, “Electrical Conductivity of n-doped GaN-based Distributed Bragg Reflectors”, 2016

Wei Wang, “Direct integration of CVD graphene on p-GaN as transparent conductive films for light-emitting diodes”, 2016

Rickard Andersson, “Investigation of electrical contacts on n-type 4H-SiC”, 2015

Salwa Salam Cynthia, “TiO2/SiO2 Distributed Bragg Reflectors by Sputtering for GaAs based VCSELs”, 2014

Marcus Johansson, “HfO2/SiO2 Distributed Bragg Reflectors for GaN-based VCSELs”, 2013

Stefan Carlsson, “Towards High Contrast Gratings in the GaN/ZnO Materials System”, 2013

César Javier Lockhart de la Rosa, “Graphene as Transparent Conductive Film for GaN-Based Vertical Cavity Surface Emitting Lasers”​, 2012

Guests

Giulia Cardinali, Politecnico di Torino (Italy), 2019
Johannes Enslin, TUB (Germany)​​, 2019
TsuChi Chang, NCTU (Taiwan), 2018

"Nytt världsrekord i laserlabbet", Elektroniktidningen, June 2021

"Out of the blue: UV VCSELs", Compound Semiconductor, vol. 27, issue 3, May 2021

"MC2 researcher gets major grant from The European Research Council", 10 Dec., 2019​

"Electrochemical membrane release for aluminium gallium nitride devices”, Semiconductor Today, 28 Nov., 2019

”Chalmers lyfter UV-lysdioden ifrån substratet”​, Elektroniktidningen, 12 June 2019 

"Ny laserteknik öppnar en helt ny värld av möjligheter", Framtidens forskning, 26 June, 2018

“On the way towards blue surface emitting laser” /
“Mot blå ytemitterande laser”, Elektroniktidningen, 8 Feb., 2017

Youtube videos by the Foundation for Strategic Research, 2017:
”Blue lasers might become the future lighting”
“Blå lasrar kan bli framtidens belysning”