Dear professor,
I am one of the students who participated in one of your programs and I am really impressed by your work.
I am really thankful for the discussion we had in the conference and the thoughts and points we discussed. I am really amazed by the kind of contribution you have made on the field of ______________.
think I have learnt a lot from the discussion, it has changed the way we look at the perspective of life. The different articles and research papers are very enlightening and the one we got in the conference was very helpful and I am sure not everyone has the access to such papers. I have always followed your articles and research on the net but never got to read such wonderful articles and we would like you to know that I would want to attend more of such seminars and do something similar to what you are doing.
Sincerely,
Your Name