Hi Joris,
Sounds like an interesting research project. I am aware of many successful projects carried out using QS Nd:YAG lasers to remove unwanted surface deposits from terracotta - as always, care is needed but assuming initial testing is carried out and a safe fluence used then the cleaning process can be extremely sensitive. I am aware of research carried out at Tokyo National Museum last year investigating the effectiveness of laser cleaning (QS Nd:YAG) on ancient unglazed ceramic roof tiles. Unfortunately, I'm not aware of any research carried out using active fibre lasers on glazed ceramics - I guess this could be a good thing for your research! You could try contacting the El.En. Light for Art group in Italy as they supply fibre lasers to the heritage field and have excellent links with many research groups, particularly in Italy. It might also be worth contacting G.C.Lasers in Chicago who have been working with high frequency solid-state lasers for many years.
Good luck with your research and please feel free to contact me if you have any questions. Maybe you could update the LDG on your research findings in a year or so - we'd be very interested to hear how you get on.
Regards,
Martin