I believe though Landis proposals suggest using laser beams from Earth to power the craft, even for those that have ion engines to provide additional thrust. Perhaps this was because at that time the possibility of ultra thin films was not considered. This was even before the invention of carbon nanotubes remember.
Another problem is that his proposal would require an extremley large lens to focus the laser light, of the order of 1000 km across. This might be though because he was considering interstellar missions. It would certainly be much smaller for interplanetary missions.

Robert Zubrin and Dean Spieth have also discussed solar sail propulsion in this report:

Ultra-Thin Solar Sails for Interstellar Travel
Phase I Final Report
December 1999
http://www.niac.usra.edu/files/studies/final_report/333Christensen.pdf

With their proposal you could use solar light alone to power the craft, not lasers, because of the ultra-light sails.
The new transparent nanotube films are comparable to the weight requirements for the nanometer thin aluminum future sails they mention and so might make the future sails they discuss *currently* feasible.
Also the new transparent nanotube films' low weight density surpasses that of the micron thick metal-coated mylar sheets they discuss as the current technology by a factor of 100. So the acceleration would be larger by a factor of 100.
Zubrin and Spieth discuss that the metal-coated mylar sheets have an areal density of about 7g/m^2 and the acceleration of this material at 1 AU, excluding payload mass, will only be about 1.2 mm/s^2. A trip to Mars using solely solar sail propulsion would take about a year.
However, using the new transparent nanotube films, the acceleration would be 100 times larger so a trip to Mars might be smaller by a factor of the square root of this (using the relationship for distance travelled at constant acceleration s = (1/2)at^2). That is, the time
required would be smaller by a factor of 10, or about a month.
On page 16 of their report, they summarize trip times for various sail materials and suggest a mesh nanotube sail might allow a solar sail to reach Pluto in 1.7 days, the Oort cloud in 1.2 years and Alpha Centauri in 32 years.
I'm not sure if this type of material is already feasible. But the recent single atomic layer graphene sheets might do the trick:

Discovery Of Two-Dimensional Fabric Denotes Dawn Of New Materials Era.
Chernogolovka, Russia (SPX) Oct 22, 2004
"Researchers at The University of Manchester and Chernogolovka, Russia
have discovered the world's first single-atom-thick fabric, which
reveals the existence of a new class of materials and may lead to
transistors made from a single molecule. The research is to be
published in Science on 22 October."
http://www.spacedaily.com/news/materials-04zzt.html

Radical fabric is one atom thick.
"Professor Andre Geim, who leads the research team, explained that the
material they have discovered could be thought of as millions of
unrolled carbon nanotubes which have been stuck together to make an
infinitely large sheet, an atom thick.
They showed that electrons could travel sub-micron distances without
being scattered, which means fast-switching transistors."
http://news.bbc.co.uk/1/hi/sci/tech/3944651.stm

Electric Field Effect in Atomically Thin Carbon Films.
Science, Vol 306, Issue 5696, 666-669 , 22 October 2004
http://www.sciencemag.org/cgi/content/abstract/306/5696/666

Bob Clark