An SPIE article on ultra-short fiber-grating lasers less than 1cm long  for sensing applications.

The gratings were inscribed in the active fiber using a 193nm excimer laser. Because it induces index grating in the fiber core by a two-photon excitation process, it does not require hydrogenation to photosensitize the fiber. This not only avoids laser efficiency degradation, but also simplifies fabrication.

via SPIE Newsroom.