Dimali Amarasinghe

Broadband solid state optical amplifier based on a semiconducting polymer

A compact, solid state optical amplifier based on the conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] has been demonstrated. The amplifier was optically pumped. Gratings were used to couple the signal into and out of the film. The transmitted signal was amplified over 100 times in a 1mm long waveguide giving 21dB gain at 630nm. A gain of >13dB was observed at 615 and 650nm giving a gain bandwidth of >26THz. The gain dynamics at pump densities below 5μJ∕cm2 are described by an exciton-exciton annihilation model. At higher pump intensities, amplified spontaneous emission and photoinduced losses become significant.

Organic Semiconductor Optical Amplifiers

Organic semiconducting materials have been researched for novel optoelectronic devices due to their efficient light emission and high gain properties. Such devices range from organic light-emitting diodes and solar cells to lasers and amplifiers. This paper explores the research carried out on one of these devices: organic semiconductor amplifiers that have shown to give high gains of 20-40 dB in solution and solid state.

Picosecond gain switching of an organic semiconductor optical amplifier

All-optical switching of an individual pulse within a sequence of amplified pulses is demonstrated in a conjugated polymer optical amplifier. The switching was achieved using a control pulse resonant with the excited state absorption. An extinction ratio of ∼5.5dB was observed, while the intensities of the remaining pulses in the sequence, spaced at 50ps intervals, were unaffected. A pump-probe study was performed and showed full gain recovery within 2ps.

Amplification of optical pulse sequences at a high repetition rate in a polymer slab waveguide

Amplification of three short light pulses in a 140ps time window at 5kHz repetition rate has been demonstrated using a compact amplifier based on the conjugated polymer poly(9,9′-dioctylfluorene-co-benzothiadiazole). The amplifier was optically pumped and gratings were used to couple the signal into and out of the film. A gain of 22dB was observed for a signal pulse temporally aligned with the pump pulse in a 1mm waveguide. For a signal pulse delayed by 140ps, the maximum gain achieved was 14dB. The results are a step towards the use of polymer amplifiers in data communications.

Synthesis and properties of novel star-shaped oligofluorene conjugated systems with BODIPY cores

Summary Star-shaped conjugated systems with varying oligofluorene arm length and substitution patterns of the central BODIPY core have been synthesised, leading to two families of compounds, T-B1–T-B4 and Y-B1–Y-B4, with T- and Y-shaped motifs, respectively. Thermal stability, cyclic voltammetry, absorption and photoluminescence spectroscopy of each member of these two families were studied in order to determine their suitability as emissive materials in photonic applications.

Recent Advances in Polymer Lasers and Optical Amplifiers

Advanced polymer photonic devices are reported. These include a directly diode-pumped polymer laser, a femtosecond polymer laser, and a broadband solid state polymer optical amplifier.