Helium Cadmium laser

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Helium Cadmium laser

• Rianne t Hoen
• 8 april 2008

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Content

• He-Cd laser
• Energy level scheme
• Broadening
• Threshold conditions
• Mode profile
• Applications
• Research

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Helium Cadmium laser
Tube length 0.25-1.5 m Bore 1-2 mm Gas
pressure 5-10 Torr He Gas mixture CdHe at
1001 Gas temperature 600 K Te 15.000
20.000 K

• Metal Vapor Gas laser
• Lasing at 325.0nm, 353.6 nm and 441.6 nm
• Evaporation Cd by cataphorese

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Energy level scheme
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Energy level schemeExcitation mechanisms

• Penning ionization
• Electron excitation Cd
• Photo-ionization via emission from He

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Energy level schemeThree level system
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Energy level schemeThree level system
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Broadening

• Natural broadening
• Doppler broadening
• Isotope broadening
• 1.5 GHz

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Threshold conditions

• Population inversion occurs
• That is unless
• Radiation trapping occurs when

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Typical parameters
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Mode profile

• Longitudinal modes 1-15
• TEM00 and multimode
• Power output
• multi-mode at 441.6 nm up to 200mW
• multi-mode at 325.0 nm up to 100mW
• single TEM00 mode at 441.6 nm up to 50mW
• No laser spiking.

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Applications

• Lithography
• Holography
• Photosensitive materials
• Used in Compact Disk and Laser Disk

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Recent experiment
Thick film lithography using laser
write simplicity ? shortens the fabrication
duration of X-ray mask
Thick-Film lithography using laser write, Y.Cheng
et al., Microsystem Technologies 9 (2004) 1722
Springer-Verlag 2004