I just have to have him (THE older man of my dreams)?

I am completely head over heels for an older man (about 15 years older!!). He is the most lovely person i have ever known but i think even if he feels the same about me as i do about him, he would think any sort of relationship would be inappropriate becasue of the age difference. How can i show him i'm interested without embarring myself?? It is also a bit more complicated as he is my lecturer at uni and thus far has had a very positive effect on my future career so i don't want him to think this is some sort of extreme student gratitude!! please please help me. I will go down any road- whether it be a direct or some sort of subtle advice. I have no idea how to go about this!