Despite their impressive capabilities, laser weapons do have some significant downsides. These can be taken advantage of to give the battlefield soldier a measure of defense against them.
Because lasers are basically light, a number of everyday means can be used to diminish their effectiveness. Their performance can be significantly decreased or negated altogether by phenomena like fog, rain, snow, smoke, and so on, which can disperse or refract the weapon’s beam to ineffectualness, depending on how thick it is.
Reflective surfaces also present an obstacle, bouncing the beam off a potential target, but this is not as big an impediment as one would tend to think. Mirrors are usually frequency-specific; one that reflects visible light will not necessarily reflect UV or infrared wavelengths, making them vulnerable to weapons that can easily change their beam wavelength. Also, mirror quality is an issue. Most mirrored surfaces are not 100% smooth, meaning that some of the energy from the laser will be absorbed by it, probably melting or marring the reflective surface. Thus unless the mirror unusually tough and is smooth down to its component molecules, it probably won’t be able to reflect a laser hit in the same spot more than once or twice.
Also, with visible light lasers, objects that happen to have the exact same color as the beam can completely neutralize the laser, no matter what material its made of. Like mirrors, there’s still the problem of energy absorption eventually degrading such a defense, but something as simple as a cotton blanket with the right color can degrade or deflect a tank-destroying multi-megajoule beam. Manufacturers of non-tunable laser weapons would probably go out of their way to make sure the color of their laser beams were not that common in real life.
Reflective surfaces and same-color pigments would be of dubious value against laser weapons with changeable frequencies. Besides, having a highly-reflective or bright surface easily found by enemy sensors would be a profound disadvantage that may significantly outweigh any protection provided.
Tech Level: 9
Lasers can easily, permanently blind a person with unprotected eyesight. Some lasers, called dazzlers, are specifically designed for this. However, any laser of significant power can also cause occular damage by reflection or diffraction off a target surface to any soldier who was unlucky enough to be caught too close.
The most obvious defense against this are high-quality, impact-resistant, full-vision (fully covering the eyes and leaving no gaps for unwanted light to get through) sunglasses whose protection extends both into the infrared and ultraviolet bandwidths.
Tech Level: 12
One unusual but effective defense against lasers would be aerosol dispensers. These come in either a "bomb" form (where a canister of compressed air releases the substance omni-directionally from a casing) or spray-can form. Either way, the aerosol would pump ultrafine but reflective particles into the air around a potential target. The particles would be fine enough to hang suspended in the air from several minutes to up to half an hour, depending on weather and wind conditions. A laser beam hitting these particles would disperse just as if it had hit a thick dust cloud, even though to the naked eye the area would appear only mildly hazy. Again, though, the reflective properties of the aerosol particles may only work against certain wavelengths.
Tech Level: 12
Another defense would be ablative armor, usually made of an array of tightly-clustered gel or foam packs. When a laser hits one of these packs, the heat from the laser instantly boils the gel or foam away, the explosive reaction almost instantly absorbing, dispersing, and redirecting most of the laser energy away from the target. This is much like modern day explosive reactive armor, but carried out on a much smaller scale.
Like reflective surfaces, ablative armor would not be effective if hit more than once in the same spot.
SUPERCONDUCTIVE ENERGY DISPERSIVE ARMOR
Tech Level: 15
If room-temperature superconductors are ever developed, an even more effective defense against lasers becomes available. Fabric interwoven with superconductor wire would instantly absorb the incoming electromagnetic energy of the laser beam and disperse it evenly over its entire surface area. The energy re-radiates almost instantly into the surrounding air as heat. The laser would have to pump enough energy to completely destroy the entire armor all at once before it could penetrate through to its true target. If the superconductor mesh in the armor were cooled via refrigeration unit or a heat sink, even more energy would be required to overcome the armor.
Fire, Fusion, and Steel: The Traveller Technical Architecture
On The Web:
How modern day lasers work:
Report on the US laser weapons program circa 1995:http://www.hrw.org/reports/1995/Us2.htm
Article on the state of modern-day laser weapons:>http://www.icltd.org/laser_weapons.htm
On Laser Blinders:http://www.phys.ksu.edu/perg/vqm/laserweb/Ch-9/F9s3t4p5.htm
Specifics on Dye Lasers:http://220.127.116.11/lapd/General/Diagnostics/LIF/Dye.html
DOE article on laser weapon research:http://www.eurekalert.org/features/doe/2002-04/dlnl-bff053102.php