Directed Energy Weapon High Energy Lasers (DEW HEL)
Introduction
High Energy Lasers (HELs) share many similarities with FSO systems, in that both have the purpose of providing light energy to a specific location at distance and operate on much the same principles but at higher energy levels. As a result of this shared purpose, they also share engineering challenges. Solutions for these challenges, such as beam focusing, are likely to be relevant to some degree across FSO and HEL use cases. Other types of directed energy weapons, such as microwave-based systems, share fewer similarities with FSO systems.
Relevance to FSO
HELs differ from FSOs in terms of the cost of materials used, their complexity, and most importantly the power levels used. However, due to their potential value for military applications they are currently an area of research. This ongoing research may mitigate these issues and result in shared technology trickling down into FSO communications applications. Ignoring current practical considerations, theoretically HELs could also potentially be used in novel ways to mitigate adverse atmospheric conditions.
For example HELs could potentially be used in conjunction with lower powered FSO lasers for communication to ionize or ablate atmospheric particles in the communication path, effectively either causing condensation or providing enough heat to evaporate fog or create filamentation of the air via the Kerr effect, [1] [2] creating a channel for the FSO laser. Hybrid systems could allow the use optical communication in adverse weather conditions where standard FSO systems would fail due to excessive scattering and absorption.
How HELs work
Directed energy weapons or DEWs use electric energy sources such as HELs. Currently visible range solid state HELs are the most common type, consisting of glass fiber lasers in the roughly 1 micron range, and Diode pumped Alkaline DPAL lasers in the roughly .795 micron range.
Historically, chemical lasers dominated HEL technology due to their extremely high energy density and efficient conversion of chemical energy into light. The drawbacks to these systems was largely their size, weight, and the difficulty of working with hazardous chemicals. Modern laser-pumped systems resolve these issues but require an external power source and a chiller to manage heat and improve efficiency. Also, in modern laser-pumped systems, roughly two-thirds of the energy is lost as waste heat.
Overall, modern HELs have lower wattages than Strategic Defense Initiative (SDI)-era systems, which reached tens of megawatts, but they are far more practical to deploy.
Comparison between Previous and New HEL systems
The primary difference between older HELs is that modern HELs use multiple combined laser diodes as a “pump source”, or seed laser instead of directly the final source of energy. The pump laser cycles through a gain medium or laser gain media such as fiber, crystal or gas. [3] The gain medium then amplifies the energy provided by the pump laser by orders of magnitude, which then generates the high-power output. This gain comes from the same process of stimulated emission used to generate the initial seed laser. In this process, atoms in the gain medium, excited by a pump source, release photons that trigger further emissions, amplifying the light into a powerful, focused beam.
At first this may seem like “free” energy and a violation of thermodynamics. However, in short, the optical pump serves to “charge up” the lasing medium with potential energy by creating a state of population inversion, where there are more atoms in excited states than in lower-energy states. This stored potential energy is then converted to light energy when the HEL is activated and produces a laser beam.
Pulsed vs Continuous WAVE HELs
HELs can operate in a Continuous Wave (CW) mode, or a pulsed/Q-switching mode. In the former the laser pump(s) must either provide continuous energy to counteract the depletion of energy from the emitted laser. In a pulsed or Q-switching mode, the laser releases all its energy in a short burst before recharging and firing again. The period of charging and discharging occurs very rapidly, in the range of milliseconds to nanoseconds. “Pulsed HELs deliver energy in bursts, causing material ablation and radiation, while CW lasers provide continuous energy, leading to gradual melting. The primary limitation for the effective output of both types of systems is the amount energy that can be provided by the laser diode pump, and the amount of waste heat that can be expelled from the system.
The excited state persists until it naturally decays to its ground state for a very brief time, typically under milliseconds. It also must recharge in order to return to popular inversion, but the time this takes is also similarly short, allowing pulse lasers to “fire” extremely rapidly, with the primary limitation being the energy provided by the laser pump.
The lasing medium is also used to preserve beam coherence and low spectral width, creating a high-quality beam.
It is worth noting that higher wattage in laser systems does not necessarily directly equate to more power on target. Higher power can have negative effects. For example, the heat transferred to the air by high powered laser can reduce its density, with the change in density being proportional to how close to the center of the laser beam the air is. This uneven heating of the air essentially creates a negative lens, which scatters light and reduces beam focus, resulting in less power on target.
Types of Pumped Systems
Spectrally combined Fiber (SCF)
This architecture uses multiple fiber lasers that are themselves diode-pumped. Each fiber laser generates light at a different wavelength, which is then spectrally combined to merge them into a single high-power beam via a diffraction grating or wavelength multiplexer – essentially the reverse of a light prism.
Coherently Combined Fiber (CCF)
A fiber seed laser is used as the initial source. The light is then split to multiple phase shifters and its light is amplified by multiple diode-laser-pumped fiber amplifiers. Each phased beam of light passes through a laser-pumped amplifier, and is then phase-shifted and combined coherently to form a single beam with higher power.
Diode Pumped Alkali Laser (DPAL)
This system uses diode lasers to excite alkali atoms (e.g., cesium, rubidium) to higher energy states Unlike SCF or CCF systems, DPALs rely directly on gaseous mediums instead of fibers. Energy transfer between gas molecules helps achieve the population inversion needed for lasing. In other words the pump laser or lasers “charges” the gas medium with energy, resulting in a higher gain than the pump laser(s) itself can produce. This is the most straightforward “pumped” system, as the pumped energy is directly transferred to the alkali atoms via collisional energy transfer.
Distributed Gain Laser (DGL)
A fiber seed laser generates the initial beam, which is then amplified by an array of diode-pumped solid-state laser amplifiers. These amplifiers provide gain distributed along the optical path in series, somewhat like coils in a coilgun. As the starting laser passes through each amplifier it’s power increases.
Future Challenges
Currently it remains to be seen if HELs will find use outside of military scenarios, and what these specific scenarios may be.
The primary concern will be if the higher power from HELs is able to mitigate challenges in FSO systems, such as atmospheric conditions. Innovations in techniques to keep energy directed in as small an area as possible is the most likely bleed over between the two.
Conclusion
High Energy Lasers (HELs) represent a major technological shift in directed energy weaponry, evolving from early chemical laser systems to modern solid-state and fiber-based architectures. While historical HELs, such as those from the Strategic Defense Initiative era, achieved higher peak power outputs, modern systems emphasize practicality, efficiency, and deployability.
HEL research continues to drive advancements in beam control, energy efficiency, and atmospheric compensation techniques, many of which could have crossover applications in Free-Space Optical (FSO) communication and other civilian fields. Despite challenges such as waste heat management and beam distortion, ongoing innovation is steadily improving HEL effectiveness and scalability.
As HEL technology matures, its applications will likely expand beyond military air defense and missile interception. Potential future uses could include space-based laser platforms, atmospheric clearing for optical communications, and even high-precision industrial applications.
Recent HEL systems
DE-MSHORAD (Directed Energy Maneuvering Short Range Air Defense)
DE-MSHORAD is a US Army Directed Energy Variant of the MSHORAD striker. [4] It is also referred to as “Guardian”. This system is intended to shoot down drones, rockets, mortars and similar projectiles. Currently four vehicles are deployed.
Leonardo DRS Counter-Uncrewed-Arial Systems Directed Energy (C-UAS DE) Stryker
Leonardo DRS [5] has also built an anti-Drone Stryker comparable to the DE-MSHORAD. Mounted to the demonstrator striker is the 26kW BlueHalo Locust [6].
Compact Laser Weapons Systems (CLaWS)
CLaWS is a Boeing designed 5kW class system for the US Marines, intended for perimeter defense against drones. 5 systems are currently in evaluation. [7]
HELWS High Energy Laser Weapons System
HELWS is a Raytheon 10kW cUAS system mounted to larger vehicles, 3 systems are currently in deployment evaluation. [8]
LaWS on USS Ponce
The XN-1 LaWS or AN/SEQ-3, built by Northrup Grumman, was an early laser-pumped HELs to be deployed in field. [9] It featured a 3kW fiber HEL laser and was deployed on the USS Ponce from 2014 to 2017.
A follow-on system, the 150-kilowatt Laser – Technology Maturation Laser Weapons System Demonstrator (LSWD) [10] has also been built by Northrop Grumman. [11] In 2022 it finished its first deployment after being installed on the USS Portland in 2019. [12]
HELIOS
HELIOS is a 60 kW laser weapon system designed by Lockheed Martin [13] and currently onboard the USS Preble. In addition to the laser weapon, it also features Long Range Intelligence, Surveillance, Reconnaissance capabilities (ISR) and a Couter UAS Dazzler (C-ISR).
In 2024 an image was released of the system being fired on a drone target. [14]
Iron Beam
Iron Beam is a 100kW class Israeli system built by Rafael [15], with similar objectives as the current “Iron Dome” rocket interception system. Deployment is expected to potentially begin in 2025. [16]
HELCAP
HELCAP is a US Navy HEL project with a reported power of 300 kW. [17]
Dragonfire
The Dragonfire Laser Directed Energy Weapon (LDEW) is a UK MoD project led by MBDA UK partnered with Leonardo and QinetiQ as a demonstrator of suitability of HELs for naval applications.[18]
The system currently has a 50kW laser, with tests firing at ranges of 2.1 miles. Currently plans are to begin fielding similar systems on other royal navy ships by 2027. Energy is stored via a Flywheel Energy Storage System. [19]
Test footage of the system firing has been released. [20][21]
Laboratory lasers
In laboratory to “transportable” settings, 300kW lasers are the current upper range of HELs of the pump types described earlier, such as the General Atomics 300 kW DGL [22], InLight 300kW CCF, [23] LLNL DPAL laser, [24] and Lockheed SCF laser, [25] with effective ranges in the realm of 20 km. Lockheed is also currently developing a 500 kW class laser as part of its HELSI initiative, [26] a scaled up version the 300 kW laser previously used as part of the IFPC-HEL or “Valkyrie” system. [27] [28]
References
[1] https://www.nature.com/articles/s41598-019-48542-1
[2] https://pubs.aip.org/aip/apl/article-abstract/125/1/011103/3300554/Extending-femtosecond-laser-superfilamentation-in?redirectedFrom=fulltext
[3] https://www.rp-photonics.com/laser_gain_media.html
[4] https://www.rtx.com/raytheon/what-we-do/integrated-air-and-missile-defense/lasers
[5] https://www.twz.com/sponsored-content/leonardo-drs-gives-details-on-its-directed-energy-counter-drone-stryker
[6] (This $10M U.S. Army Laser Melts Drones With $3 Beams) https://www.youtube.com/watch?v=eFiDYFnlp7s
[7] https://www.popularmechanics.com/military/research/a28120435/laser-weapon-claws/
[8] https://www.rtx.com/raytheon/what-we-do/integrated-air-and-missile-defense/lasers
[11] https://www.globalsecurity.org/military/systems/ship/systems/lwsd.htm
[12] https://seapowermagazine.org/northrop-grumman-laser-weapon-system-completes-deployment-on-uss-portland/
[14] https://www.cbsnews.com/news/us-navy-warship-photo-firing-laser-weapon-preble/
[15] https://www.rafael-usa.com/programs/iron-beam/
[16] https://www.nationaldefensemagazine.org/articles/2025/1/29/israels-iron-beam-set-for-historic-deployment
[17] US Navy Readies 300 kW HELCAP Laser System for Intercept Tests – Naval News
[18] https://www.janes.com/osint-insights/defence-news/weapons/uk-dragonfire-laser-weapon-demonstrator-completes-first-high-power-firings
[19] https://www.gov.uk/government/news/uk-usa-test-naval-power-systems
[20] (DragonFire: New declassified footage of £10-a-shot laser precision weapon in action) https://www.youtube.com/watch?v=Vg2IuPKqvt4
[21] (Test footage of UK DragonFire Laser Directed Energy Weapon) https://www.youtube.com/watch?v=XCK9ghnv-VA
[22] https://www.ga.com/ga-ems-and-boeing-team-to-develop-300kw-class-helws-prototype-for-us-army
[23] https://www.nlight.net/press-releases-content/nlight-awarded-86-million-contract-to-develop-high-energy-laser
[24] https://www.laserfocusworld.com/executive-forum/article/14290785/high-energy-lasers-await-pentagon-green-light
[25] https://www.popsci.com/technology/lockheed-martin-new-laser-weapon/
[26] https://news.lockheedmartin.com/2023-07-28-Lockheed-Martin-to-Scale-Its-Highest-Powered-Laser-to-500-Kilowatts-Power-Level
[27] https://www.ga.com/ga-ems-and-boeing-team-to-develop-300kw-class-helws-prototype-for-us-army
[28] https://missiledefenseadvocacy.org/defense-systems/directed-energy/
https://web.archive.org/web/20230328131437/https://lasers.llnl.gov/science/photon-science/directed-energy
https://www.rp-photonics.com/high_power_fiber_lasers_and_amplifiers.html
https://www.rp-photonics.com/optical_amplifiers.html
https://www.rp-photonics.com/seed_lasers.html
https://www.rp-photonics.com/high_power_lasers.html
https://www.laserfocusworld.com/executive-forum/article/14290785/high-energy-lasers-await-pentagon-green-light