I saw a post , in an astronomy blog, about a person who would use a laser (5mw i think) and aim it at the sensor on top of the street lamp. When he wanted to use his telescope, he would zap the lightpost.
He said red lasers work, green lasers do not.
Infrared would prob be best, no visible light. Shining a laser up to a light post seems to run the risk of blinding passing airplanes. If there is an accident in front of your home and they know you turned off the light, could be lawyer fodder. I wish there was a way to make a shade that would cast a shadow only on my home and leave the street illuminated.