You can download a fully functional SPICE based simulator here...
http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html
It's free and has no limitations, well except it only has TI chips in the default model library.
Zax.
P.S. Daedal - the 555 IC is included and makes an excellent pulse...
Daedal, Great job on the circuit explanation - however, you say the 1N4001 diode reduces the voltage to the LD but it's in reverse polarity (so is in fact an open in normal operation).