Organic copolymer lasing from single defect microcavity fabricated using laser patterning

Reducing the lasing threshold in optically pumped organic lasers is a necessary component of the drive to develop an organic laser diode, as this may help mitigate the losses associated with electrical contacts and charge injection. In this study we show how increasing the binaphthyl (BN) spacer content in polydioctylfluorene (PFO) decreases its amplified spontaneous emission threshold (ASE) through the suppression of intermolecular interactions. Using co-polymers with low lasing thresholds, we use a laser patterning technique to fabricate physical defects (having a diameter of ∼2.5 μm) within a vertical microcavity. Such defects create additional lateral confinement, with this approach allowing us to reduce the lasing threshold from 11 μJ cm−2 to 7 μJ cm−2 and increase cavity Q-factor from 495 (planar cavity) to 2300. The enhanced performance and the stack structure of the defect microcavity show it is a promising architecture for an electrically-pumped laser device

Realisation of a sub-wavelength dimple using a 193 nm wavelength photonic nano jet

There are many areas of research that benefit from tight focussing of light. We report experimental and computational results of a laser irradiated silica microsphere, 1 μm diameter localised on an SU-8 substrate. A single pulse from an ArF excimer laser (λ = 193 nm) was used to generate a Photonic Nano Jet (PNJ). Subsequently the PNJ was used as a processing tool to produce a dimple cavity in the supporting SU-8 layer. Atomic Force Microscopy (AFM) was employed to determine dimple geometry. Measurements revealed a diameter of 150 ± 10 nm at full-width-half-maximum and a depth of 180 ± 10 nm. Finite Difference Time Domain (FDTD) simulations were carried out to visualise the propagation of 193 nm radiation through a microsphere. Experimental measurements and simulations were in close agreement confirming that the electromagnetic radiation is tightly focussed by the microsphere. Finite Element Method (FEM) simulations were also carried out to calculate the laser induced temperature rise of SU-8 in the region beneath the microsphere. FEM simulations predicted a temperature of 775 K which is above the boiling point of SU-8 (480 K). We briefly discuss the ejection mechanism of the microsphere in terms of the increase in temperature of the underlying SU-8