Online PhD defence by Kristoffer Skaftved Mathiesen

Title: Design and fabrication of photonic crystal nanolasers


Principal supervisor: Jesper Mørk
Co-supervisor: Kresten Yvind
Co-supervisor: Yi Yu

Evaluation Board
Prof. John McInerney, University College Cork, Ireland
Researcher Yacomotti Giacomotti, France

Assoc. Prof. Nicolas Stenger, DTU Fotonik, Denmark

Master of the Ceremony
Assoc. Prof. Nika Akopian, DTU Fotonik

AbstractDriven by the increase in global data consumption, and the limitations of current semiconductor technology, the interest in integrated optics for communication and data processing applications is growing. Replacing the electrical interconnects with optical ones on the chip-scale can overcome the present limitations. A key ingredient is small footprint integrated lasers, where devices based on the 2D photonic crystal platform has seen rapid progression in the past decade. These lasers have shown an energy consumption low enough to compete with the current electronic interconnects, and efforts towards integration with silicon are steadily advancing.

This thesis focuses on the design and fabrication of photonic crystal lasers and passive photonic crystal cavities to improve their efficiency and enhance the understanding of such nanoscale devices.

The laser threshold is optimized in fabricated devices by shifting holes in the photonic crystal and device characteristics such as the penetration depth and mirror phase has been investigated numerically. The mirror phase is found to primarily be dependent on the change in resonance wavelength due to the design variations, while the penetration depth is found to increase as the Q-factor is increased due to gentler confinement of the cavity fields.

As the second group worldwide, photonic crystal devices with a buried heterostructure gain medium have been fabricated. Two different devices; a standard line defect laser and the novel Fano laser is characterised. Numerical investigations are also carried out on equivalent cavities and open photonic crystal waveguides with buried heterostructures of varying lengths. The addition of the buried heterostructure to the line defect laser cavity redshifts the cavity resonance above the bandgap of the surrounding photonic crystal. Keeping the nanocavity passive in the Fano laser, the first all CW operating photonic crystal Fano laser is realized.

The photonic crystal nanolasers promise exciting future opportunities with experimental realizations of novel device designs of ultra-compact lasers with very low energy consumption enabling optical interconnects on the chip-scale.

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tor 28 maj 20
13:30 - 16:30



Online. Please write to Susanne Kolodziejczyk to sign up.