Evanescent field interaction with Fe3O4 nano particle for passively Q switched thulium doped fiber laser at 1.94 mm
Abstract We experimentally demonstrate the use of Fe3O4 based saturable absorber (SA) to generate self starting, passively Q switched pulses at 1943 nm. The Fe3O4 particles were characterized with scanning electron microscopy with energy dispersive spectroscopy. The size distribution of Fe3O4 particles was varied from ~150 nm to 980 nm. The proposed SA was fabricated with combination of a side polished fiber and the Fe3O4 particle by using evanescent field interaction between the side polished fiber and the Fe3O4 particle. The insertion loss and polarization dependent loss of the proposed SA were measured as ~4 dB and 0.3 dB, respectively at a wavelength of 1930 nm. The stable passively Q switched pulses were readily generated from thulium doped fiber laser incorporating the proposed SA at 1943 nm. The pulse width was changed from ~8.1 ms to ~880 ns while the repetition rate was changed from ~61 kHz to ~87 kHz. The tuning capability of both pulse width and repetition rate was also shown according to pump power.
Optics Laser Technology