ABSTRACT
Nanomaterials have ignited new interest due to their distinctive electronic, mechanical, and optical properties. Zinc oxide nanostructures are fabricated into thin film and then inserted between two fiber ferrules to act as a saturable absorber (SA). The modulation depth and insertion loss of the SA are 5% and 3.5 dB, respectively. When the ZnO-SA is incorporated into the laser cavity, a stable Q-switched pulse tunable from 1536 to 1586 nm (50 nm range) with pulse energy up to 46 nJ was observed. Our result suggests that ZnO is a promising broadband SA to generate passively Q-switched fiber lasers.
ABSTRACT
We demonstrate a Q-switched erbium-doped fiber laser using tungsten disulfide (WS2) as a saturable absorber. The WS2 is deposited onto fiber ferrules using a drop-casting method. Passive Q-switched pulses operating in the C-band region with a central wavelength of 1560.7 nm are successfully generated by a tunable pulse repetition rate ranging from 27.2 to 84.8 kHz when pump power is increased from 40 to 220 mW. At the same time, the pulse width decreases from a maximum value of 3.84 µs to a minimum value of 1.44 µs. The signal-to-noise ratio gives a stable value of 43.7 dB. The modulation depth and saturation intensity are measured to be 0.99% and 36.2 MW/cm², respectively.
ABSTRACT
Gabapentin (GAB) is a newer second-line antiepileptic drug (AED) used in children. This is a multi-centre retrospective observational study of the efficacy, tolerability and retention rate in 105 children, aged 0-17.5 years (mean 10.1) over a 14 year period. The median age of epilepsy onset was 2.5 years (range 0-14.6). 72% started GAB as at least the 3rd AED, with 43% having been withdrawn from at least 2 AEDs. 77% had focal and 52% symptomatic epilepsies. The maintenance doses for GAB ranged 6.0-87.3 mg/kg/day (mean 43.7). The study comprised 157 person-treatment years for GAB. GAB was well tolerated with 55% remaining on treatment beyond 1 year. No serious adverse events were reported whilst on GAB, but 39% reported possibly and probably related adverse events. Seizure improvement (<50% seizure frequency compared to baseline) at more than 12 months of treatment, was reported in 35% of patients starting GAB, including 6% who remained seizure free. The results demonstrated the efficacy and tolerability of GAB in children with difficult to treat epilepsies, and a good response to treatment beyond 12 months, in both focal and generalised epilepsies.
