wavelength of 10th Doctor's sonic screwdriver?

Basically the title... I'm hoping someone out there has played with one of these blue/uv sonic screwdrivers and know what the wavelength might be. I'm looking for photoreceptors sensitive to something in the general range it might put out.

Thanks.

http://4.bp.blogspot.com/-5QZH36JSsYU/UYXxu8IBYMI/AAAAAAAAAOk/oK2Dghh9ap8/s640/IMG_2488.jpg

around 405nm, could be 445nm cause the camera might make it look more purple.

A140 diode might do, it's purple/bluish