Black ceiling tiles reduce occupational UV exposure for staff in clinical area containing phototherapy cabinets.

Phototherapy clinics administer UV light to patients via phototherapy cabinets. The UV radiation from these cabinets reflects on the white ceiling tiles of the clinic and is directed towards both staff and patients in the area. This is particularly problematic for clinical technologists who must undertake dosimetry in these areas and have a particular time (often as low as 30 minutes) before they reach their maximum exposure limit. By replacing the white tiles with black alternatives which absorb the stray radiation, we have been able to reduce these reflections by almost 90%, prolonging the time to maximum exposure by nearly 10 times. We therefore present these findings to encourage similar clinics to undertake the simple protocols outlined which will significantly improve staff and patient safety.

Ultrashort pulse generation by semiconductor mode-locked lasers at 760 nm.

We demonstrate the first semiconductor mode-locked lasers for ultrashort pulse generation at the 760 nm waveband. Multi-section laser diodes based on an AlGaAs multi-quantum-well structure were passively mode-locked, resulting in the generation of pulses at around 766 nm, with pulse durations down to ~4 ps, at pulse repetition rates of 19.4 GHz or 23.2 GHz (with different laser cavity lengths of 1.8 mm and 1.5 mm, respectively). The influence of the bias conditions on the mode-locking characteristics was investigated for these new lasers, revealing trends which can be ascribed to the interplay of dynamical processes in the saturable absorber and gain sections. It was also found that the front facet reflectivity played a key role in the stability of mode-locking and the occurrence of self-pulsations. These lasers hold significant promise as light sources for multi-photon biomedical imaging, as well as in other applications such as frequency conversion into the ultraviolet and radio-over-fibre communications.