Optical delay line for high time resolution measurement: W-type delay line.

We propose and demonstrate a newly designed optical delay line (W-type delay line) that improves the resolution of optical path length, namely, time resolution, by an order of more than 3 in comparison to the spatial resolution of a conventionally used translational stage. Using a conventional mechanical translational stage having a spatial resolution of 1 mum, the performance of the W-type delay line was evaluated by interferometric measurements with a diode laser, and the time resolution of 16 as was confirmed.