Transverse light coupling from GaAs lasers into optical fibres

We report a method for transverse light coupling from GaAs lasers into optical fibres. The fibre end is positioned perpendicular to the laser-beam direction and is cut at the end under 45° to reflect the laser radiation. We measured 10% coupling efficiency for a plastics fibre which was simply cut by a blade. We used this method for an automatic-gain-control circuit and picked up reference light from the back side of a d.h. laser.