We report the photosensitive transient increase in transmission of a probe HeNe beam in a HiBi fibre when a counter propagating beam from a frequency doubled Nd. YAG of peak power 150W and 8ns pulse length is propagating in the fibre. Increases in transmission of upto 50%, in 100m of fibre, have been observed. The increase in transmission is observed to decrease when the YAG laser is switched off, but with a long decay time. This behaviour is counter to previously reported effects were attenuation is decreased and remains so by photobleaching, or attenuation is increased by Blue/green light. We propose a tentative model for this effect in terms of the photobleaching and production of Ge defect centres.
H. O. Jamshidi,
A. J. Rogers,
"Transient Photosensitive Transmission In Hibi Fibres", Proc. SPIE 1120, Fibre Optics '89, (29 October 1989); doi: 10.1117/12.960988; https://doi.org/10.1117/12.960988