A Study on the Gas Dynamic Laser

Abstract

A Gas Dynamic Laser (GDL) is a laser that uses variations in the molecular vibrational states\' relaxation velocities. since of the characteristics of the lasing medium gas, a population inversion is accomplished in a specific amount of time since an energetically lower vibrational state relaxes more quickly than a higher vibrational one. In 1966, Edward Gerry and Arthur Kantrowitz created it at the Avco Everett Research Laboratory.[1] A combustion chamber, supersonic expansion nozzle, and CO2 mixed with helium or nitrogen are typically used as the laser medium in pure gas dynamic lasers.[23]

Introduction

A laser is a device that emits coherent light through optical amplification based on stimulated emission of electromagnetic radiation. The term “laser” is an acronym for Light Amplification by Stimulated Emission of Radiation. The first laser was built in 1960 by Theodore Maiman, based on theoretical work by Charles Townes and Arthur Schawlow. Lasers produce highly coherent, collimated, and monochromatic light, which can be focused to small areas or kept narrow over long distances, enabling applications such as laser cutting, lithography, lidar, laser pointers, and ultrashort femtosecond pulses.

Applications:
Lasers are widely used in industry, medicine, communications, entertainment, and defense. Examples include cutting and welding, optical disc drives, barcode scanners, DNA sequencing, fiber-optic communication, photolithography, surgery, lighting displays, and military targeting. Semiconductor lasers in the blue to near-UV range can replace LEDs for white light sources, offering smaller emitting areas and higher radiance.

Historical Development:

• 1916: Einstein proposed the concept of stimulated emission.

• 1928: Rudolf Ladenburg observed stimulated emission.

• 1951–53: Townes developed the maser, a microwave version of the laser.

• 1958: Townes and Schawlow proposed the optical maser; Gordon Gould coined “laser.”

• 1960: Maiman created the first ruby laser; Bell Labs developed the first gas laser (He-Ne); semiconductor lasers followed in 1962.
  Lasers quickly found practical applications, from holography to laser surgery, scanners, printers, and space exploration.

Principle of Operation:
Lasers operate under quantum physics principles:

• Atoms absorb energy, moving electrons to higher energy states (excited states).

• Spontaneous emission releases photons randomly.

• Stimulated emission occurs when a photon triggers the emission of identical photons, producing coherent light.

• Population inversion is required to sustain lasing, achieved via optical or electrical pumping.

• Three-level and four-level systems manage energy states for pulsed or continuous laser operation.

Laser Components and Beam Characteristics:

• A laser medium (solid, liquid, or gas) is excited to produce light.

• An optical resonator (mirrors) amplifies light by repeated reflection.

• Laser light is narrow, monochromatic, coherent, and can be highly collimated.

• Wavelength, coherence, beam divergence, and output power vary by material, resonator design, and emission process.

• Lasers can operate in continuous-wave or pulsed modes, with pulsed lasers achieving extremely high peak powers and ultrashort durations.

Gas Dynamic Lasers (GDL):

• Developed in 1966 by Edward Gerry and Arthur Kantrowitz.

• Achieve population inversion using differences in vibrational state relaxation rates during gas expansion.

• Can be powered by adiabatic expansion or combustion; explosively pumped variants provide extremely high pulsed power, with potential for laser weapons.

Conclusion

A gas dynamic laser (GDL) is a type of laser that uses variations in molecular vibrational state relaxation velocities. Because of the characteristics of the lasing medium gas, a population inversion occurs at a specific period when an energetically lower vibrational state relaxes more quickly than a higher vibrational state. At Avco Everett Research Laboratory, Edward Gerry and Arthur Kantrowitz created it in 1966. A combustion chamber, a supersonic expansion nozzle, and CO2 combined with nitrogen or helium are typically used as the laser medium in pure gas dynamic lasers.Gas dynamic lasers can be powered by either adiabatic expansion or combustion. Any compressed, heated gas with the right vibrational structure could be used.A variation of GDL driven by the expansion of explosion products is called an explosively pumped gas dynamic laser. The ideal explosive is hexanitrobenzene or tetranitromethane combined with metal powder. This gadget may be able to provide extremely high pulsed peak power that is appropriate for laser weapons. Gas-dynamic processes are used in almost all chemical lasers to boost their efficiency. GDL is appropriate for military applications due to its strong power output and great energy efficiency up to 30%. [22]

References

[1] Taylor, Nick (2000). Laser: The Inventor, The Nobel Laureate, and The Thirty-Year Patent War. Simon & Schuster. p. 66. ISBN 978-0684835150. [2] Ross T., Adam; Becker G., Daniel (2001). Proceedings of Laser Surgery: Advanced Characterization, Therapeutics, and Systems. SPIE. p. 396. ISBN 978-0-8194-3922-2. [3] \"December 1958: Invention of the Laser\". aps.org. Archived from the original on December 10, 2021. Retrieved January 27, 2022 [4] Semiconductor Sources: Laser plus phosphor emits white light without droop\". November 7, 2013. Archived from the original on June 13, 2016. Retrieved February 4, 2019. [5] Laser Lighting: White-light lasers challenge LEDs in directional lighting applications\". February 22, 2017. Archived from the original on February 7, 2019. Retrieved February 4, 2019. [6] How Laser-powered Headlights Work\". November 7, 2011. Archived from the original on November 16, 2011. Retrieved February 4, 2019. [7] Laser light for headlights: Latest trend in car lighting | OSRAM Automotive\". Archived from the original on February 7, 2019. Retrieved February 4, 2019. [8] Heilbron, John L. (March 27, 2003). The Oxford Companion to the History of Modern Science. Oxford University Press. pp. 447. ISBN 978-0-19-974376-6. [9] Bertolotti, Mario (October 1, 2004). The History of the Laser. CRC Press. pp. 215, 218–219. ISBN 978-1-4200-3340-3. [10] McAulay, Alastair D. (May 31, 2011). Military Laser Technology for Defense: Technology for Revolutionizing 21st Century Warfare. John Wiley & Sons. p. 127. ISBN 978-0-470-25560-5. [11] Renk, Karl F. (February 9, 2012). Basics of Laser Physics: For Students of Science and Engineering. Springer Science & Business Media. p. 4. ISBN 978-3-642-23565-8. [12] LASE\". Collins Dictionary. Retrieved January 6, 2024. [13] \"LASING\". Collins Dictionary. Retrieved January 6, 2024. [14] Strelnitski, Vladimir (1997). \"Masers, Lasers and the Interstellar Medium\". Astrophysics and Space Science. 252: 279–287. Bibcode:1997Ap&SS.252..279S. doi:10.1023/ [15] Chu, Steven; Townes, Charles (2003). \"Arthur Schawlow\". In Edward P. Lazear (ed.). Biographical Memoirs. Vol. 83. National Academy of Sciences. p. 202. ISBN 978-0-309-08699-8 [16] Al-Amri, Mohammad D.; El-Gomati, Mohamed; Zubairy, M. Suhail (December 12, 2016). Optics in Our Time. Springer. p. 76. ISBN 978-3-319-31903-2. [17] Hecht, Jeff (December 27, 2018). Understanding Lasers: An Entry-Level Guide. John Wiley & Sons. p. 201. ISBN 978-1-119-31064-8. [18] https://www.ulsinc.com/learn [19] https://www.fiberoptics4sale.com/blogs/wave-optics/semiconductor-laser-physics [20] https://www.szlaser.com/index.php/wiki/laser-physics/ [21] https://www.britannica.com/technology/laser [22] https://www.wikiwand.com/en/articles/Gas_dynamic_laser [23] \"History of Gas Lasers, Part 1—Continuous Wave Gas Lasers\" Archived 2017-09-28 at the Wayback Machine, Optics & Photonics News. Retrieved 4 June 2013

Copyright

Copyright © 2025 Muhammad Arif Bin Jalil. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.