There is a lot of misunderstanding around laser teeth whitening and its potential effects on teeth and enamel. In short, while laser teeth whitening can cause temporary sensitivity to the light that's used to treat your teeth, it does not in any way weaken them or damage the enamel.
What actually happens during laser tooth whitening is that the light is directed onto the teeth using a tiny spotlights and then activated by a special gel. This results in the removal of discolorations and stains from your teeth, which usually takes about two hours per session. While it may seem like your teeth are getting lighter every time you go for a treatment, this is only because they are becoming more visible. Your tooth color will still be exactly the same after treatment as before it - it's just that they will look brighter because of the removal of stains and discolorations.