I want to know about the project"communication between two personal computers using laser beams"?

Answer 1

Extensive information on
http://www.geocities.com/SiliconValley/Lakes/7156/laser.htm

Answer 2

there are several ways to achieve this. Basically u need some hardware like;

1) Level Converter IC like MX232,
2) Modulator using 4011 Quad Nand Gates, even 555 in astable mode can be used.
3) and Laser Diodes / Tx module (readily avbl).

at the Receiving end u need Laser Diode, Pre-Amp, & Schmitt Trigger.

1) Use Serial Port : Simle S/w, and easy to implement but h/w is bit complex. U can adjust the baud rate using s/w, typically developed in C.

2) Parallel Port: U can use its Input pins for reception & Output pins for trasnmission. But note, PCs used here must be identical to keep the s/w simple.

Coming to Software Part; you may use C, VB etc.