All this data is potentially out of date, and should be taken with a truckload of salt
Lasers are a turret group created and favored by the Amarrian race, and consequently used by Ammatar Mandate, and to a lesser extent the Khanid Kingdom, though latter prefer missiles. Several pirate factions are known to use lasers too, including Sansha's Nation and The Blood Raider Covenant. The Jove too have been cited as using laser weapons 
Lasers are the only directed energy weapon currently in existence that are used by the Faction Empires and Pod Pilots. Lasers link directly into the ship's capacitor reservoir firing a beam of light that is focused by a polished frequency crystal lens. Although lasers have the potential to cause a great deal of damage they are somewhat limited by the electromagnetic nature of the energy beam. These weapons work best against the defensive shield systems but have great difficulty penetrating the armor plating of targets. Laser have particular difficulty against advanced (tech 2) Minmatar ships. The Minmatar, after years of fighting their former slave master have developed strong defenses against the laser weapons.
Lasers do not require ammunition in the conventional sense. As mentioned above, Lasers use polished frequency crystals to focus the light beam into a specific part of the electromagnetic spectrum (for example, radio or infrared) or to focus the beam intensely for maximum firepower (multifrequency crystals). Altering the laser beam in this way changes the effective range of the weapon allowing a pilot to "range in" on a target.
There are wide variety of frequency crystals available, including advanced Beam Laser Crystals or Pulse Laser Crystals (only usable by Tech II turrets) and Faction Crystals (improved Tech I crystals) variations. Standard Crystals can be used indefinitely. However, the technologically enhanced lens manufactured by Empire Factions and Pod-pilot laboratories consist of more delicate crystalline structures which, while offering greater damage potential, degrade with use and eventually shatter. Faction crystals usually last for longer by comparison with advanced.
Lasers are medium range weapon and divide into two sub-groups:
Beam lasers have a shorter optimal range than their hybrid railgun counterparts, but do, as a whole, more damage. Advanced coolant technologies allow beam lasers to keep firing for a long time without overheating. The heaviest lasers, battleship-class tachyon beam lasers, are regarded by many as brutally devastating sniper weapons (although their range is limited) and are often used in fleet sieges.
Pulse lasers have better range than blasters, hybrid weapon from the same class, but do considerably less damage. Anyway, pulse lasers are in favor among skilled pilots because they provide good damage/range ratio. By contrast with beam turrets, pulses fire rapidly several times in a cycle.
As described in the technical section, lasers are energy weapons, so they require an exceptionally strong powergrid. Moreover, shooting them expends a huge amount of energy. Most Amarr ships are designed to lower energy weapon capacitor usage, have powerful energy grid and large capacitor capacity. This slightly negates the gluttonous nature of lasers, but automatically makes unwise any attempts to install lasers on non-Amarr spacecraft.
Like all tactical choices in New Eden, there are advantages and disadvantages in using lasers:
- Tech I crystal fitted lasers never run out of ammo and are ideal for deep space bounty hunting and raiding, far away from supply lines.
- Even though Tech II and faction crystals suffer from degradation with use, these crystals still outlast the ammo of other weaponry.
- Lasers can swap their lens fast, effectively bypassing the 10 second reload that plagues other weapon types. This allows for laser users to quickly change targets.
- Laser damage is set to EM and thermal types and is therefore predictable.
- Lasers essentially use a ship's capacitor as ammo; this means lasers will tend to drain capacitor fast unless preventative measures are taken.
- Due to high capacitor usage, laser boats are more vulnerable to energy neutralizing and have difficulties running a microwarpdrive without the skills to back it up.
As with the other kinds of weapon, lasers' damage output may be raised by installing weapon upgrades such as heat sinks. These modules efficiently dissipate heat from laser turrets, thus boosting maximum energy stream coming through them and allowing them to fire more rapidly. Other, non-system-specific upgrade modules (e.g. tracking computers) work as well.
Various laser characteristics may also be changed by using energy weapon rigs.
Tech I energy turret comparison
|Name||Size||Activation||Range||Rate of fire||Damage mod||Tracking speed||Signature res.|
|Gatling Pulse Laser||Small||1.82 GJ||4,000+500 m||2.10 s||1.5x||0.308125 rad/sec||40 m|
|Dual Light Pulse Laser||Small||2.67 GJ||4,500+1,500 m||2.70 s||2x||0.27375 rad/sec||40 m|
|Medium Pulse Laser||Small||4.44 GJ||5,000+2,000 m||3.50 s||3x||0.24625 rad/sec||40 m|
|Dual Light Beam Laser||Small||3.89 GJ||8,750+3,000 m||3.20 s||2x||0.13 rad/sec||40 m|
|Medium Beam Laser||Small||7.22 GJ||10,000+4,000 m||4.00 s||3x||0.1 rad/sec||40 m|
|Focused Medium Pulse Laser||Medium||8 GJ||9,000+3,000 m||4.05 s||2x||0.09 rad/sec||125 m|
|Heavy Pulse Laser||Medium||13.33 GJ||10,000+4,000 m||5.25 s||3x||0.08125 rad/sec||125 m|
|Quad Light Beam Laser||Medium||5.45 GJ||8,000+1,000 m||3.15 s||1.5x||0.081 rad/sec||125 m|
|Focused Medium Beam Laser||Medium||11.67 GJ||17,000+6,000 m||4.80 s||2x||0.042 rad/sec||125 m|
|Heavy Beam Laser||Medium||21.67 GJ||20,000+8,000 m||6.00 s||3x||0.033 rad/sec||125 m|
|Dual Heavy Pulse Laser||Large||25 GJ||18,000+6,000 m||6.08 s||2x||0.0375 rad/sec||400 m|
|Mega Pulse Laser||Large||40 GJ||20,000+8,000 m||7.88 s||3x||0.03375 rad/sec||400 m|
|Dual Heavy Beam Laser||Large||35 GJ||35,000+12,000 m||7.20 s||2x||0.0175 rad/sec||400 m|
|Mega Beam Laser||Large||65 GJ||40,000+16,000 m||9.00 s||3x||0.0153125 rad/sec||400 m|
|Tachyon Beam Laser||Large||95 GJ||44,000+20,000 m||12.50 s||4.5x||0.0139205 rad/sec||400 m|
|Dual Giga Pulse Laser||Extra large||320 GJ||32,000+5,000 m||11.81 s||8x||0.0040512 rad/sec||1000 m|
|Dual Giga Beam Laser||Extra large||520 GJ||72,000+22,000 m||13.50 s||5.5x||0.002296875 rad/sec||1000 m|