LASER mic question. Shortest range?

I'm writing a novel and need to know if a LASER mic could work with this set-up: the characters are trying to listen in on a conversation by bouncing a laser beam off a window pane. But they need to do this (for various reasons) at close range. The device sending the beam and the reciever are both set-up on the balcony outside the window that the beam is bouncing off of.

Would this close range set up work or does the LASER beam need a longer distance? Thanks, guys!

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As a writer you just need the dam thing to work .
As an engineer I have to force it to work which takes time and is a novel in its self.

I suggest one of two options.
1) It just works, don't explain how, why, etc. The how is not part of your story. (fiction)
2) If you don't know how close is too close but you think it is a problem.......have one person adjust the knobs many times, the sound is garbled and some of the conversation is lost, but enough of the audio is clear that you can move on with the plot. (non-fiction)