How to Detect Back-EMF from Inductor
I wouldn't use your circuit because the size of the inductor needed is going to be large and overall, the change in light level needed is going to be significant to get the 555 to trigger. I would however consider using a photodiode ampliier like this: -



So you start from a point of strength in that you can get a really good signal for only moderate changes in light intensity and R\$_F\$ can be lowered to reduce sensitivity. See also this google image page for hundreds of other ideas related to amplification of a photodiode.

What you need next is a simple high pass filter between V\$_{OUT}\$ and your 555: -



So now the RC circuit is replacing the LR circuit and you are dealing with components that are more manageable in size and cost. High pass filter circuits are found on this google image page.