1.   You must take adequate precautions and care when you try these experiments because the "light" generated can harm one's eyes.

To build a simple home made nitrogen laser clik on the URL below:

    http://www.allegedlyfunny.com/laser.html

You must also go to the link below to find more information about how lasers work, basics of an atom, the laser/atom connection types of lasers, laser classifications, useful links and so on.

    http://www.howstuffworks.com/laser.htm

Take care and enjoy yourself.