Material that changes transparency when lased from side? I am into photonics research, and have been searching about this topic in vain, but almost nothing from Google shows up. So i turned here for some light.
Do you guys know any material that changes its transparency when a laser (or light) illuminates from its side? 
 A: Can you  define "side"?  Are you looking for a material which changes its absorptivity in one axis only when illuminated from a different axis?    I tend to doubt that even hyperboic, aka metamaterials, can demonstrate such a behavior.
As you may know, there a variety of organic dyes which are used as either saturable absorbers or saturable transmitters.   In either case,  there's a two-photon absorption process which puts the material into an excited state and as a result the transmissivity changes drastically.  Fast-transition material which is highly transmissive in the saturated/excited state is used for passive Q-switched lasers, for example.
At the other end of the time-spectrum are the materials used for photochromic eyeglasses.  However, in all these cases,  the absorptivity (and its change with illumination) is isotropic.
But seeing as I can't even think of a material whose absorptivity (exclusive of polarization effects) is a function of the direction of the light rays,  I doubt you can get what are looking for.   
