TECHNOLOGY FOR ETIs MORE EXPENSIVE AT OPTICAL WAVELENGTHS
Optical and laser technology is inherently more complicated and expensive than its
microwave counterpart, and since optical photons are more energetic than "warm
fuzzy" microwave photons, economic considerations would dictate the use of the
lower-cost microwave system.
Counter Argument
It is always dubious to make economic comparisons between technologies, which in late
20th Century earth are such that one is mature and the other has a long way to go yet.
There is no doubt that if we tried to field a high-power space-based laser transmitter
system today, the cost would be extremely high, notwithstanding the fact that we don't yet
have the knowledge-base and capability to do the required point-ahead targeting. However,
for ETIs this would be trivial, and the reason for choosing a particular technology for
contacting other civilizations would not be governed by our present-day economics.
Remember, the ETIs will be able to target very narrow beams, so the energy cost per
optical photon landed on the target will most likely be a lot less than the energy cost to
land a microwave photon! This is notwithstanding the fact that the former photons require
more energy to be generated.
How can we compare the cost of a PC with an abacus? By early next century, the cost of
manufacturing a PC, far more powerful than today's Pentiums, will be more than the cost to
manufacture an abacus. On grounds of today's economics, one would say that if one just
wanted to add up some numbers, it would be foolish to pay extra for a PC. But next
century, the economics could be very different!