Photonic crystals for light-emitting devices

Photonic crystals or photonic bandgap (PBG) structures promise to revolutionise optoelectronics by making a new class of highly efficient, low noise light emitters possible. We present data to show that their properties, in particular 2-D systems, have now been fully characterised in the relevant semiconductor material system and at near-infrared wavelengths, so effort can be redirected towards making active light emitters, As a first example, we present a semiconductor laser with one output mirror designed according to PBG principles. From threshold and efficiency data, we derive a reflectivity of 95+/-10 % for this mirror which underlines the viability of the PBG approach for practical devices, In order to realise the full potential of photonic crystal light emitters, however, important material issues need to be considered. Non-radiative recombination, for example, is a big problem when tile photonic crystal is an integral part of the active region because of the relatively large areas of exposed surface. Several possible solutions to this problem are presented.