convert PIR to laser detector?

Hi all.
First time here.
I wonder if any one could help to, as simple as possible, convert a PIR detector to operate as a laser trip wire.
So i am thinking rip out the IR parts and put in photo diode to change its operation.
In the end the detector would need to operate or trigger, in the absence of the laser pointer beam.
Help would be awesome as my shop was broken into the other day.
Thanks.
Darren.

It just becomes a matter of remove PIR sensor and replace with a LASER type sensor. Signal conditioning depends on how the existing sensor is setup. A circuit schematic of the existing would be a good start.

Ron

Why can't you use the PIR to detect an intruder?