Hello Hussam,

Well, if you have the light source of 30mW/m2 and trying to increase the intensity using a lenses then that would not be the best way.

And from your question you have stated that you need an intensity of "ONE SUN". What does that mean? Do you want the "intensity" that of the sun as total or that received from the sun on the earth? Also think whether your source is monochromatic or polychromatic!!!

You might be aware that the intensity of light changes (or reduces!) with the square of the distance from the source. And what a lense would do is just concentrate (focus) the light from the source into one fine spot (The collimation effect). Now, this spot will also not give you the same intensity of 30mW/m2 but would be affected by the distance (d2) and also some attenuation due to the lense (material). Kindly also note that the solar irradiance (on a bright sunny day) is not in mW or Watts but exceeds more than 1kW/m2 in the optical spectrum (UV/VISIBLE/IR).

So, if you have to increase the light intensity you will have to increase it at the source level. If the amplification is needed, then you know what and why we talk about LASER (Light Amplification by Stimulated Emission of Radiation). Now with a source of 30mW, you can imagine what amplification is needed.

I have tried to put the facts together and hope that this will help you in finding the proper solution to your experiment.

Best wishes!

thanks  for all