Gallium Arsenide based photonic crystal surface emitting lasers

Optimal photonic crystal design parameters are then determined for a prospective PCSEL<br>structure.<br><br>Informed by these modelling results, the growth, fabrication, and characterisation of 1070 nm GaAs based PCSELs is discussed. Four PCSEL devices with varying void geometries in the photonic crystal are analysed, utilising transmission electron microscopy imaging of each device. It is shown how the position and size of a void in the photonic crystal region affects the threshold and slope efficiency of a PCSEL, and the results are compared to simulation, the first time a study of this kind has been carried out to the best of my knowledge.

It will be shown how improved void geometries result in strong coupling strengths, and how this improved coupling strength leads to lower threshold, more efficient devices. The photonic bandstructure of the best performing device is mapped and analysed to determine photonic crystal coupling strength, and the lasing band of this device is identified.<br><br>The power efficiency benefits of PCSEL arrays are then investigated.

Coherent PCSEL arrays offer the possibility of realising a very high brightness laser diode through large area scaling of PCSEL power, but are still in their infancy. It this thesis, it is shown that that for two and three element PCSEL arrays, with electrically driven waveguide regions, that utilisation of an array structure results in increased device efficiency compared to devices operating individually. The improved efficiency is attributed to the reduction of in-plane cavity losses of the PCSELs when the waveguide regions are in transparency.

The results obtained are then compared to expected values and show strong agreement. The coherence of the two and three element arrays is also discussed.<br><br>Finally, a method for the in-line non-destructive characterisation of PCSELs at the point of photonic crystal etch is outlined. It is shown that a simple photoluminescence measurement provides information on the fill factor and height of the etched photonic crystal structure prior to regrowth, without the need of any advanced microscopy techniques.

It is discussed how this method could be applied in an industrial context, improving the manufacturability of PCSELs.<br><br><br>