Why Better Beam Shape Cannot Beat Lost Energy

Introduction

Adaptive optics can make a weather-degraded laser beam sharper, but it cannot recover energy that the atmosphere has already removed. This distinction is critical in discussions of directed energy weapons. Atmospheric turbulence mainly distorts the phase, or shape, of a laser wavefront. Adaptive-optics systems use sensors and deformable mirrors to correct those distortions and refocus the surviving light. By contrast, fog, smoke, dust, sea spray, haze, and some atmospheric gases physically remove energy from the beam through scattering and absorption. Once photons have been absorbed or scattered away from the intended path, no wavefront correction system can recreate them. The result is a fundamental limit: adaptive optics can improve how efficiently the remaining energy is delivered to a target, but it cannot restore power that never arrives. [NATO Publications+2RP Photonics]publications.sto.nato.intNATO Publications6.0 PROPAGATION AND ADAPTIVE OPTICSVirtually all the atmospheric effects on laser weapon systems can be traced to three…

How Scattering and Absorption Remove Power From the Beam

Atmospheric attenuation is not simply a focusing problem. It is an energy-loss problem.

When a high-energy laser propagates through air, three broad effects matter: turbulence, absorption, and scattering. Turbulence alters the beam’s optical phase and can cause spreading or beam wander. Absorption occurs when atmospheric constituents such as water vapour or other molecules convert part of the laser energy into heat. Scattering occurs when particles or droplets redirect photons away from the intended beam path. NATO educational material on laser propagation identifies absorption and scattering as distinct atmospheric mechanisms that degrade laser weapon performance alongside turbulence. [NATO Publications]publications.sto.nato.intNATO Publications6.0 PROPAGATION AND ADAPTIVE OPTICSVirtually all the atmospheric effects on laser weapon systems can be traced to three…

The crucial point is that scattering and absorption reduce the amount of optical power still travelling toward the target.

• Absorption destroys useful beam energy by converting it into thermal energy within the atmosphere.
• Scattering redirects photons into other directions, preventing them from contributing to the target spot.
• Dense aerosols, including fog, smoke, dust, and sea spray, can produce severe attenuation over comparatively short distances.
• Longer propagation paths accumulate more losses because attenuation compounds with distance. [repositum.tuwien.at+2Sejong University]repositum.tuwien.atAtmospheric Impact on Laser Beam PropagationMost of the power is absorbed by water vapor. In addition, small particles in the air deflect the laser…Read more…

A useful analogy is a leaking hose. Adaptive optics can straighten and aim the water stream that remains, but it cannot recover water that has already leaked out through holes along the hose.

This is why weather can reduce laser effectiveness even when beam-control systems are functioning perfectly. If only a fraction of the original optical power survives the atmospheric path, the target can receive only that surviving fraction, regardless of how accurately the beam is focused. [NATO Publications]publications.sto.nato.intNATO Publications6.0 PROPAGATION AND ADAPTIVE OPTICSVirtually all the atmospheric effects on laser weapon systems can be traced to three…

Why Deformable Mirrors Only Correct the Surviving Wavefront

Adaptive optics operates on wavefront errors, not on missing energy.

A typical adaptive-optics system measures distortions in the incoming or reflected optical wavefront and commands a deformable mirror to introduce an opposite distortion. The goal is to flatten the wavefront and concentrate the surviving light into the smallest possible spot. This can dramatically improve beam quality and irradiance when turbulence is the dominant problem. [RP Photonics+2Axiom Optics]rp-photonics.comOpen source on rp-photonics.com.

However, deformable mirrors manipulate the phase of light that still exists within the beam. They do not generate new photons.

If atmospheric scattering has redirected part of the beam away from the propagation axis, those photons are no longer available for correction. Likewise, photons absorbed by water droplets, aerosols, or gases have been converted into other forms of energy and are gone from the optical beam. A mirror can reshape the phase distribution of the remaining light, but it cannot restore energy that has already left the beam. [repositum.tuwien.at+2Sejong University]repositum.tuwien.atAtmospheric Impact on Laser Beam PropagationMost of the power is absorbed by water vapor. In addition, small particles in the air deflect the laser…Read more…

This limitation is reflected in the way adaptive optics is described across laser and optical engineering literature. Adaptive-optics systems are repeatedly characterised as tools for compensating aberrations, turbulence, and wavefront distortion. Their purpose is to improve beam quality, image quality, or focus quality—not to reverse atmospheric extinction. [RP Photonics+2Axiom Optics]rp-photonics.comOpen source on rp-photonics.com.

Even studies exploring the theoretical limits of adaptive optics focus on how well phase distortions can be corrected under given turbulence conditions. They do not suggest that adaptive optics can recover energy removed by absorption or scattering processes. [Optica Open]preprints.opticaopen.orgAdaptive optics limitations for laser beam propagation along slant pathsOptica OpenAdaptive-optics limitations for laser beam propagation…by M Kalensky · 2025 · Cited by 9 — In this paper, we use wave-optic…

Sharper Does Not Mean More Powerful

This distinction often causes confusion because adaptive optics can increase the intensity measured at a target.

Suppose atmospheric turbulence spreads a beam over a large spot. Correcting the wavefront may concentrate the surviving energy into a much smaller area, producing a higher energy density. The target may therefore experience greater heating or damage even though the total surviving power has not increased. The system has improved delivery efficiency, not restored lost energy. [Axiom Optics+2ResearchGate]axiomoptics.comAxiom OpticsFrom Blur To Clarity: A Deep Dive Into Adaptive OpticsAdaptive Optics: What it is, how deformable mirrors can be used to corr…

In other words:

When Attenuation Matters More Than Optical Distortion

The practical importance of adaptive optics depends on which atmospheric effect dominates.

In relatively clear air, turbulence may be the primary source of performance degradation. Under those conditions, wavefront correction can produce substantial improvements because most of the beam energy still survives the journey. Correcting the phase of that surviving light can significantly tighten the spot and raise irradiance on the target. [Axiom Optics+2RP Photonics]axiomoptics.comAxiom OpticsFrom Blur To Clarity: A Deep Dive Into Adaptive OpticsAdaptive Optics: What it is, how deformable mirrors can be used to corr…

Dense fog presents a very different situation. The atmosphere is no longer mainly distorting the beam; it is removing energy from it. Water droplets scatter and absorb light so strongly that the available power reaching the target may collapse regardless of wavefront quality. In such circumstances, the dominant limitation becomes transmission loss rather than optical aberration. [repositum.tuwien.at+2Sejong University]repositum.tuwien.atAtmospheric Impact on Laser Beam PropagationMost of the power is absorbed by water vapor. In addition, small particles in the air deflect the laser…Read more…

The same logic applies to smoke, dust clouds, maritime aerosols, and other particle-rich environments. A perfectly corrected wavefront carrying only a small fraction of the original laser power may still be ineffective because the target receives insufficient energy for the intended effect. This is one reason why weather remains a central operational constraint for laser weapons despite advances in adaptive-optics technology. [NATO Publications+2Semantic Scholar]publications.sto.nato.intNATO Publications6.0 PROPAGATION AND ADAPTIVE OPTICSVirtually all the atmospheric effects on laser weapon systems can be traced to three…

The Core Limitation

The fundamental limitation is conservation of energy. Adaptive optics can redistribute and concentrate the optical energy that survives atmospheric propagation, but it cannot recreate photons that have been absorbed or scattered away. As atmospheric attenuation increases, a point is reached where improving beam shape yields diminishing returns because the dominant problem is no longer distortion—it is the absence of energy. For directed energy weapons operating through fog, smoke, dust, or sea spray, this distinction explains why better wavefront correction cannot overcome severe atmospheric losses. [NATO Publications+2Semantic Scholar]publications.sto.nato.intNATO Publications6.0 PROPAGATION AND ADAPTIVE OPTICSVirtually all the atmospheric effects on laser weapon systems can be traced to three…

Amazon book picks

Further Reading

Books and field guides related to Why Better Beam Shape Cannot Beat Lost Energy. Use these as the next step if you want deeper reading beyond the article.

Book

Principles of adaptive optics

By Robert K. Tyson

First published 1991. Subjects: Adaptive Optics, Optics, Adaptive.

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Introduction to adaptive optics

By Robert K. Tyson

First published 2000. Subjects: Adaptive Optics, Optical detectors, Optical instruments, Optical measurements, Optics, Adaptive.

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Adaptive Optics in Astronomy

By François Roddier

First published 1999. Subjects: Optique, Adaptive Optics, Imaging systems in astronomy, Astronomie, [études diverses].

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Directed Energy Weapons

By Bahman Zohuri

First published 2016. Subjects: Lasers.

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Browse more on Amazon: Principles of adaptive optics to adaptive optics books Adaptive Optics in Astronomy

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Endnotes

1. Source: publications.sto.nato.int
   Link: https://publications.sto.nato.int/publications/STO%20Educational%20Notes/STO-EN-SCI-340/EN-SCI-340-06.pdf
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   NATO Publications6.0 PROPAGATION AND ADAPTIVE OPTICSVirtually all the atmospheric effects on laser weapon systems can be traced to three...

2. Source: rp-photonics.com
   Link: https://www.rp-photonics.com/adaptive_optics.html

3. Source: repositum.tuwien.at
   Title: Atmospheric Impact on Laser Beam Propagation
   Link: https://repositum.tuwien.at/bitstream/20.500.12708/14294/2/Atmospheric%20impact%20on%20laser%20beam%20propagation.pdf
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   Most of the power is absorbed by water vapor. In addition, small particles in the air deflect the laser...Read more...

4. Source: researchgate.net
   Link: https://www.researchgate.net/publication/282410226_Adaptive_optics_system_for_real-time_wavefront_correction
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   The degree of correction of an adaptive...Read more...

5. Source: researchgate.net
   Link: https://www.researchgate.net/publication/358049406_Wide-Aperture_Bimorph_Deformable_Mirror_for_Beam_Focusing_in_42_PW_TiSa_Laser
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   (PDF) Wide-Aperture Bimorph Deformable Mirror for Beam...20 Jan 2022 — This paper reports a large-aperture adaptive optical system with...

6. Source: pdfs.semanticscholar.org
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   Beam Atmospheric Propagation Modelling for...by T Fahey · 2021 · Cited by 109 — The underlying causes of laser beam attenuation in the a...

7. Source: sjuairi.com
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   Sejong UniversityUntitledabsorption and scattering—which leads to power loss and waveform distortion. Atmospheric attenuation τATM can be...

8. Source: axiomoptics.com
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   Axiom OpticsFrom Blur To Clarity: A Deep Dive Into Adaptive OpticsAdaptive Optics: What it is, how deformable mirrors can be used to corr...

9. Source: preprints.opticaopen.org
   Title: Adaptive optics limitations for laser beam propagation along slant paths
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   Optica OpenAdaptive-optics limitations for laser beam propagation...by M Kalensky · 2025 · Cited by 9 — In this paper, we use wave-optic...

Additional References

1. Source: eso.org
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   8. Adaptive OpticsAdaptive Optics is absolutely essential for OWL, to concentrate the light for spectroscopy and imaging and to reach the...

2. Source: biophotonics.illinois.edu
   Link: https://biophotonics.illinois.edu/research/optical-coherence-imaging/aberration-correction-and-adaptive-optics
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   Aberration correction and adaptive opticsOptical aberrations can be corrected by using reconfigurable optical elements such as deformable...

3. Source: issp.ac.ru
   Link: https://www.issp.ac.ru/ebooks/books/open/Topics_in_Adaptive_Optics.pdf
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   Topics in Adaptive OpticsThe first widely used application of adaptive optics was for compensating atmospheric turbulence effects in astr...

4. Source: eureka.patsnap.com
   Title: report atmospheric effects on long range laser power transmission
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   PatSnap EurekaAtmospheric Effects On Long-Range Laser Power...28 Aug 2025 — Discover how atmospheric conditions impact laser power trans...

5. Source: youtube.com
   Title: Why Laser Weapons Cannot Replace Missiles In Modern Warfare | WION Podcast
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   How Iron Beam Turns Electricity Into a Weapon in Milliseconds | WION Podcast...

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   Laser Weapons Are Becoming Reality Faster Than You Think...

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   by B Gu · 2022 · Cited by 5 — To assess the performance of adaptive optics and predict an optimal wavefront correction, we built a wav...

8. Source: youtube.com
   Title: The Pentagon’s Laser Problem and The Company To Fix it
   Link: https://www.youtube.com/watch?v=iyBkTwFyIqY
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   Why Laser Weapons Cannot Replace Missiles In Modern Warfare | WION Podcast...

9. Source: adsabs.harvard.edu
   Link: https://adsabs.harvard.edu/full/1992ESOC…40..245M
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   In the case of active optics, it is the compensation of wavefront aberrations due to...Read m...

10. Source: researchportal.hw.ac.uk
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    simulating the beam shaping capabilities of...by S Scholes · 2023 · Cited by 9 — Predominately, deformable mirrors have been used in ada...