Abstract

Pulsed laser deposition (PLD) has often been avoided as a preferred fabrication method due to the large number of particulates generated on the waveguides during growth. We have grown uncapped and buried Nd:GGG waveguide lasers, as before[1], to study the effect of particulates on the lasing power threshold. A comparison between the lasing power threshold of the waveguide and the particulate density is shown in fig.1. It can be seen that the effect of the particulates has a far more dramatic effect on those guides with increased confinement. An increase in particulate density from 3.5 × 10⁴ to 9.7 × 10⁵ particulates cm^-2 led to an increase in absorbed power threshold from 2.5mW to 167mW. A 4μm thick guide with a particulate density of 3.2 × 10⁶ particulates cm^-2, however, lased easily at 19mW where a 2μm thick waveguide would be unable to lase at the pump powers available. Even an increase up to 1 × 10⁷ particulates cm^-2 (a very poor quality film) would still allow lasing at around 60mW. The 8μm thick waveguide showed good waveguide performance regardless of particulate density, lasing at 2.2m W and 12.2mW with particulate densities of 5.5 × 10⁴ cm^-2 and 6.6 × 10⁶ cm^-2 respectively, a change in particulate density of over 2 orders of magnitude. The particulate density of the Capped layer is higher than that of the other 4μm unclad waveguides at 1.5 × 10⁷ cm^-2. A film with such a high particulate density has been made in a 4μm unclad structure but was unable to lase at the incident laser powers available (~ 700mW @ 808nm). The buried laser had a lasing threshold of 14.8mW of absorbed power. For comparison lasing action in an uncapped layer with a particulate density 4 times lower was observed at 19mW absorbed power.

© 2001 EPS