It is called "Laser Encounters: and is in the Portal 1 WIP. However it is Portal 2.
What an interesting map it is - needs work but it is a long play with 4 large areas.

You will probably get frustrated in the room the the rotating Laser - white gel surfaces change from portable to non-portable. Gradually you see that he is trying to prevent you from getting through it using certain methods and after a while should find the solution.

It is a great map - what can I say ?
Complex, long, and FUN.

Fixed, the download should now be in the Portal 2 released maps section.