Question

In aeroplan which is used as a glass windows to control intensity of light

Answer 1

Generally aircraft windows are made of "plexiglass"

This material is light, relatively strong (not shatter-proof, but it'll take a moderate beating) and has decent optical properties.
Its major drawback is "crazing" -- hairline cracks on the surface of the material that form over time from dirt, stress, temperature, UV exposure.