One of the things I learned last night is that the only benefit to good reflectors, even parabolic reflectors, is that you get more light from the bulb into the tank, but that light still loses intensity per the inverse square law (approximately). If it were possible to have a point source light, of one discrete wave length, in a very deep parabolic reflector you could avoid the inverse square law. We can't do that. But, a very good laser would come very close to eliminating the inverse square law. To work as a tank light it would take an array of those lasers to cover the entire tank. I don't expect to ever see this.

Another thing I learned is that our plants are extremely adaptable to a wide range of light intensity. Within just one tank there is a 50 to 1 range of PAR and the plants grow in the full range.

One more obvious fact I learned is an explanation for why my Limnophilia aromatica grew so slowly - no pruning required - for a month, then suddenly it requires weekly heavy pruning. It grew taller, reaching out to a much higher light intensity, thus much faster growth. A corrolary to that is an explanation for the need for high light intensity for carpet plants - they are as far from the light as they can get, so they never, ever see that 1500 PAR intensity.