Can I turn Radio waves into light?
Can I do this circuit practically o_O? 
  Is there any transistor or IC that can oscillate 300 THz? 
  Can I find an inductance (coil) of 0.0025 pH and capacitor of 1 pF?


Not quite, no, and no. But this is an area of active research: The Truth About Terahertz.

The basic principle of the tuned LC radio emitter is resonance. The techniques for producing high frequency tuned signals at higher frequencies are also based on resonance, but because the frequency is higher the resonant elements need to be much smaller. You also need some system for amplifying the signal, bearing in mind that terahertz is above the operating speed of almost all transistors. You can get tuned light of a particular frequency using a LASER (Light Amplification by Stimulated Emission of Radiation), which is also a resonant process. Intermediate frequencies can be produced by a device called a Klystron, which is halfway between a vacuum tube and a laser in its operation.