Carbon-dioxide laser
The carbon-dioxide laser (CO2 laser) was one of the earliest
Amplification
The
2), around 10–20% nitrogen (N
2), a few percent hydrogen (H
2) and/or xenon (Xe), with the remainder being helium (He).[citation needed
2 is continuously pumped through it. The specific proportions vary according to the particular laser.
The
2 collisionally de-excites by transferring its vibrational mode energy to the CO2 molecule, causing the carbon dioxide to excite to its {v3(1)} (asymmetric stretch) vibrational mode quantum state. The CO
2 then radiatively emits at either 10.6 μm[i] by dropping to the {v1(1)} (symmetric-stretch) vibrational mode, or 9.6 μm[i]
The addition of helium also plays a role in the initial vibrational excitation of N
2, due to a near-resonant dissociation reaction with metastable He(23S1). Substituting helium with other noble gases, such as neon or argon, does not lead to an enhancement of laser output.[2]
Because the excitation energy of molecular vibrational and rotational mode quantum states are low, the photons emitted due to transition between these quantum states have comparatively lower energy, and longer wavelength, than visible and near-infrared light. The 9–12 μm wavelength of CO2 lasers is useful because it falls into an important window for atmospheric transmission (up to 80% atmospheric transmission at this wavelength), and because many natural and synthetic materials have strong characteristic absorption in this range.[3]
The laser wavelength can be tuned by altering the isotopic ratio of the carbon and oxygen atoms comprising the CO
2 molecules in the discharge tube.
Construction
Because CO2 lasers operate in the infrared, special materials are necessary for their construction. Typically, the
The most basic form of a CO2 laser consists of a gas discharge (with a mix close to that specified above) with a total reflector at one end, and an output coupler (a partially reflecting mirror) at the output end.[4]
The CO2 laser can be constructed to have continuous wave (CW) powers between
Because the laser transitions are actually on vibration-rotation bands of a linear triatomic molecule, the rotational structure of the P and R bands can be selected by a tuning element in the
Applications
Industrial (cutting and welding)
Because of the high power levels available (combined with reasonable cost for the laser), CO2 lasers are frequently used in industrial applications for cutting and welding, while lower power level lasers are used for engraving.[8] In selective laser sintering, CO2 lasers are used to fuse particles of plastic powder into parts.
Medical (soft-tissue surgery)
Carbon-dioxide lasers have become useful in surgical procedures because water (which makes up most
The 10.6 μm CO2 laser remains the best
The CO2 laser at the 9.25–9.6 μm wavelength is sometimes used in dentistry for hard-tissue ablation. The hard-tissue is ablated at temperatures as high as 5,000 °C, producing bright thermal radiation.[16]
Other
The common plastic
Because the
CO2 lasers are used in
In semiconductor manufacturing, CO2 lasers are used for extreme ultraviolet generation.
The Soviet Polyus was designed to use a megawatt carbon-dioxide laser as an in-orbit weapon to destroy SDI satellites.
See also
Notes
References
- .
- .
- ^ a b [1] Yong Zhang and Tim Killeen, Gas Lasers: CO2 Lasers - progressing from a varied past to an application-specific future, LaserFocusWorld (4 November 2016)
- ^ "Output Couplers". ophiropt.com. Ophir Optronics Solutions Ltd. Retrieved 17 February 2014.
- ^ "Carbon-Based Curtain Absorbs Stray Laser Light". Tech Briefs Media Labs. 30 November 2007. Retrieved 17 February 2014.
- Brookhaven National Lab.
- ^ F. J. Duarte (ed.), Tunable Lasers Handbook (Academic, New York, 1995) Chapter 4.
- S2CID 137296053.
- ISBN 978-1-4511-0955-9.
For practical purposes, there are three methods of resurfacing: mechanical sanding (dermabrasion), chemical burn (chemical peels), and photodynamic treatments (laser ablation or coagulation).
- S2CID 46081244.
- ^ "Israeli researchers pioneer laser treatment for sealing wounds". Israel21c. 16 November 2008. Archived from the original on 28 July 2009. Retrieved 8 March 2009.
- PMID 12580643.
- ^ Vitruk, Peter (2014). "Oral soft tissue laser ablative and coagulative efficiencies spectra". Implant Practice US. 6 (7): 22–27. Retrieved 15 May 2015.
- ^ Fisher, J. C. (1993). "Qualitative and quantitative tissue effects of light from important surgical lasers". Laser Surgery in Gynecology: A Clinical Guide: 58–81.
- ^ Fantarella, D.; Kotlow, L. (2014). "The 9.3 μm CO2 Dental Laser" (PDF). Scientific Review. J Laser Dent. 1 (22): 10–27.
- ^ "Laser Surgery Basics". American Laser Study Club. Retrieved 4 May 2018.
- PMID 15100818. Retrieved 21 October 2009.
- ^ C. P. Bewick, A. B. Duval, and B. J. Orr, Rotationally selective mode-to-mode vibrational energy transfer in D2CO/D2CO and D2CO/Ar collisions, J. Chem Phys. 82, 3470 (1985).
External links