Light Weapons

Traditional ranged weapons come with some serious drawbacks.  They are hard to aim.  Projectiles can be dodged and slower projectiles can sometimes be caught and used against you by the enemy.  Ammunition is bulky and awkward to carry, and it tends to run out quickly.  Projectiles have a limited range.  Projectiles also only offer a limited set of options.  Projectile weapons can certainly be effective, but there are a lot of liming factors and inconveniences that make them less than ideal.

Light based weapons are much better in a number of ways.  Light sabers are a great, though fictional example.  A light saber blade will never go dull.  Light sabers can cut things that metal blades cannot.  Of course, real life light sabers with modern technology would run their batteries down in a matter of seconds, but for a weapon that can cut a hole in the side of a tank, maybe it is worth it.  Unfortunately, we do not actually have the technology to make the light saber itself.

Laser weapons have major advantages over projectile weapons.  They come with the same limitations as light sabers would though.  Lasers require enormous amounts of energy.  A practical laser weapon using modern technology would need a large and heavy battery or power generator with it.  This would be impractical for battle field use unless mounted on a moderate sized vehicle.  Outfitting individual soldiers with laser weapons is just impractical.  They would hardly be able to carry the battery required to operate the thing, and that is not even considering other gear they need to pack.  We would need much better battery technology for infantry lasers to be practical.

The benefits of lasers are massive though.  The list of limitations in the first paragraph are all eliminated with lasers.

Lasers can offer a broad range of options.  It is not difficult to design a laser that can be operated at different power levels.  In some scenarios, it might be valuable to have a laser weapon that can fire a continuous or pulsed beam, which can sweep the battle field.  For this to be effective, the power level would have to be quite high. This functionality might also be used to fire a laser through a line of people or vehicles, but for this to work, the laser would have to be able to handle many seconds of continuous operation.  This would require a good design for sinking heat as well as a good battery.  This can be done with lasers though.  Using this for a sweep would be similar to using a machine gun for cover fire, and using this for penetration would be similar to using a large gun with a hard projectile.  The difference is that a machine gun leaves gaps and a penetration round cannot control its depth.  Clearly lasers are superior for these functions.

Lasers have theoretically infinite range.  In practice, the beam tends to hit things as it goes, like dust and moisture in the air, but in a vacuum lasers have literally infinite range.  In an atmosphere, a laser beam will weaken with distance, but unlike a projectile weapon, this is easy to compensate for, merely by turning up the power.  Unlike projectiles, foggy conditions may make a laser weapon require higher power to be effective, but this is not a serious issue.  The only real downside with using a laser weapon in fog is that it creates a line back to the user, which would make laser weapons poor choices for covert ops weapons in these conditions.  In clear conditions though, laser weapons are nearly silent, and the beam is not visible, making them better covert ops weapons than guns.  Of course this only applies to visible light lasers.  Range is a major benefit of laser weapons.

Ammunition is less of a problem for lasers.  Lasers still require batteries, but batteries do not require a specific shape.  This means they don't have to be awkward like bullets or arrows.  Currently batteries are heavy.  There is a lot of room for improvement of batteries, while bullets and arrows are pretty close to as good as they can be.  We know that matter carries a lot of energy, and we even know how to extract some of it, but modern technology is not capable of safely extracting nuclear energy on an individual scale, and our abilities to efficiently extract chemical energy on small scales is also lacking.  Solar energy is a good option, but not for military use, because it is either dependent on the weather being good or requires a large battery.  Progress is being made though, and if we put sufficient resources into developing better battery technology, it would probably not be too difficult to come up with batteries that are suitable for infantry laser weapons.

Lasers are not technically much  easier to aim than other projectile weapons.  They do have the benefit of always shooting straight.  Light is not affected by wind or gravity, so it is not necessary to spend time and effort accounting for these things.  This provides a moderate advantage at very long ranges.  The real benefit of lasers in aiming is in their flexibility.  A visible spectrum laser weapon that can be adjusted can have its power turned down to where it merely makes a visible point of light on the target.  This is even better than a laser sight, because it always shows precisely where the shot will hit.  It cannot be misaligned, because it is the shot, just at a very weak power level.  In short, well designed laser weapons can be many times more accurate than projectile weapons.

Lastly, laser weapons cannot be dodged or caught.  The advantage with using light as a weapon is that light is the fastest known thing in the universe, and it is the primary thing humans used to sense things.  In other words, even with perfect reaction time, a laser cannot be dodged, because by the time you see it, it is already hitting you.  Laser can be reflected with mirrors, which is similar to catching and using an enemy projectile, except that there is no time to react, because the laser beam is not visible to the target until its light has reached the target.  To dodge a laser, the target would have to move so fast that it is literally traveling backwards in time, and that is not just faster than the speed of light.  That is faster than instant.  All evidence says that this is impossible.

Laser does have some downsides aside from requiring heavy power sources.  In theory, mirrored armor could reduce its effectiveness.  Since there is no known substance that is a perfect reflector, there is no way to reflect 100% of the energy.  This means that mirrored armor would still be heated and probably damaged by laser weapons, but it might be the difference between life and death or victory and defeat, and it could make an army or vehicle significantly more resistant against laser weapons.  This is not terribly difficult to deal with though.  Infantry can also be armed with handguns, and perhaps an infantry squad could have one person armed with a military class projectile weapon.  Vehicles mounted with laser weapons might also have a rocket launcher or some other heavy projectile weapon, just in case.  Alternatively, black paint grenades might be more effective.  A black paint grenade would easily make a mirrorized vehicle susceptible to laser.  Acid grenades could work as well, by putting a nice dark patina on the mirror finish (this would probably violate some war treaty if used anywhere near infantry though, since it would be classified as chemical weapons).  Alternatively, wavelengths of laser could be used that common armor materials will not reflect.

Most laser light is visible.  Most kinds of laser are not visible in the air, when it is clear, but dusty or foggy air will produce a visible line along the path of the beam.  This could have deadly consequences.  In addition, even when the air is very clear, the laser will produce a visible spot on the target while it is firing.  This can be useful for aiming, but it can also provide a clue as to where the wielder is shooting from.  Again, this could have deadly consequences.  We already discussed this in the context of covert ops, but even for infantry using guerilla tactics this could be a serious problem.  There is a solution though.  While most laser light is visible, it is theoretically possible to make laser radiation in any wavelength.  CD drives use infrared laser, which is quite good at producing heat.  IR laser will not produce a visible spot of light, so aiming will be slightly harder, but it also will not leave a line in air that is not clear, and it will not give the enemy additional clues about the position of the user.  In theory, laser could be emitted in the RF and microwave spectra, which are also good for producing heat (especially in water).  UV lasers would also be invisible.  In other words, where it is important to conceal position, there are options for lasers that will not give it away.

Given the massive benefits of laser weapons, I think the military should be spending most of its funding on making them viable for infantry combat use.  Yeah, it's nice to have good fighter planes, bombs, and such, but laser weapons would provide a substantial advantage.  If we were not dumb enough to give them away to what ever insurgent group is willing to do our dirty work, it would provide us with a substantial advantage over terrorist organizations.  Laser weapons also require special technical knowledge and skills to repair, so if they did come into enemy hands, they would slowly phase out as they got old and broke.  Imagine a war where our weapons can hit the enemy hours before the enemy's weapons are within range.  We do not need more military funding to have a strong national defense.  We just need to spend what we already have more wisely.