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Engineering the transverse optical guiding in GaN-based VCSELs to avoid detrimental optical loss

Seyed Ehsan Hashemi (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; Johan S. Gustavsson (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; Jörgen Bengtsson (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; Martin Stattin (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; Anders Larsson (Institutionen för mikroteknologi och nanovetenskap, Fotonik) ; Gatien Cosendey ; Nicolas Grandjean ; Åsa Haglund (Institutionen för mikroteknologi och nanovetenskap, Fotonik)
International Workshop on Nitride Semiconductors 2012, October 14-19, 2012, Sapporo, Japan, p. ThP-OD-33 (2012)
[Konferensbidrag, poster]

In order to improve the current injection in GaN-based blue vertical cavity surface emitting lasers (VCSELs) a dielectric aperture is generally used in combination with an indium-tin-oxide (ITO) layer on the top intracavity p-contact layer. The most straightforward way to realize this introduces a depression of the structure near the optical axis and we show, by using a 2D effective index method and a 3D coupled-cavity beam propagation method, that this typically results in optically anti-guided structures with associated high optical losses and thus very high threshold gains. Remarkably, the threshold gain reduces with increased negative guiding, which is due to improved lateral confinement and reduction of lateral leakage. Still, moderately positively guided designs should be preferred to avoid the detrimental effect of lateral leakage and high diffraction loss. To ensure positive index guiding, we propose to planarize the structure or introduce an elevation near the optical axis by additional processing, with an associated reduction in threshold material gain from 6000 cm-1 to 2000 cm-1 for the studied structures.

Nyckelord: Blue Microcavity lasers, Blue VCSEL, Gallium Nitride based lasers



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Denna post skapades 2013-01-07. Senast ändrad 2016-04-11.
CPL Pubid: 169373