PhD Defence by Gyeong Cheol Park

Title:  “Vertical-cavity laser with a novel grating mirror” 



Principal supervisor: Associate Professor Il-Sug Chung, DTU Fotonik

Co-supervisor: Senior Researcher Elizaveta Semenova-Huck, DTU Fotonik 


Evaluation Board:

Senior Researcher Lars H. Frandsen, DTU Fotonik

Professor Martijn Heck, Aarhus University, Denmark

Professor Elyahou Kapon, EPFL, Switzerland  


Master of the Ceremony:

Prof. Emeritus Jørn Marcher Hvam 



Hybrid 111-V on silicon (Si) 'vertical cavity lasers' (hybrid VCLs), which can emit lightlaterally into a Si waveguide, are fabricated and investigated.For the experimental demonstration of optically-pumped hybrid VCLs, CMOS­ compatible fabrication processes are designed and developed. These include a low­ temperature direct wafer bonding process for integrating 111-V layers onto a SOI wafer, as well as two types of DBR formation processes: a lift-off and an etch-back process.The  hybrid VCL  is capable  of  in-plane  emission  into  a  Si waveguide.  Thebottom HCG, abutting the Si waveguide, functions as a high reflective mirror as well as a router, which guide the vertically-amplified light laterally into the Si waveguide. The measured in-plane emission proves the lasing action with a side-mode suppression ratio of 27.5 dB at a peak wavelength of 1486 nm.The  potential for  high-speed  operation  using hybrid VCL structure  is provenby squeezing the effective cavity length. Using a dielectric DBR and a TM-HCG with a very short evanescent tail, the hybrid VCL proves a 3 dB bandwidth of 27.2 GHz at a long wavelength  of  1541 nm. A  modulation current  efficiency factor  (MCEF)  of 42.1GHz/mA 112 is estimated.Last, a new type of hybrid grating (HG) mirror for hybrid VCLs is analyzed and demonstrated. The HG mirror consists of a bottom grating and a high index cap layer integrated on the grating. The interaction between the cap and the bottom grating results in strong Fabry-Perot (FP) resonance as well as weak guided mode (GM) resonance. The GM resonance performs a crucial role in achieving a reflectance of almost 100% as well as broadening the stopband as wide as 300 nm.


Wed 08 Jun 16
13:30 - 16:30


DTU Fotonik


Lyngby Campus

Building 341, Auditorium 22