Ruby Laser: Advantages and Disadvantages

This page covers the structure, basic working principles, advantages, and disadvantages of the Ruby Laser.

What is a Ruby Laser? (Introduction)

• It’s a solid-state laser used for high-power applications such as welding, cutting, drilling, and molding.
• The following criteria are essential for the operation of a solid-state laser:
  • Sufficient carriers must be pumped from the ground state to a metastable state to enable lasing action. This is achieved by:
    • Requiring two energy levels in the active amplifying medium. Doped ionic levels act as the metastable state.
    • Using pumping or carrier inversion for stimulated emission, typically achieved by high-energy flash lamp excitation.
    • Optical feedback provided by external mirrors or electro-optic crystals.
    • A cooling arrangement to manage heat.

alt: Ruby Laser

• The ruby laser utilizes a ruby crystal as its active or amplifying medium. This crystal is made from aluminum oxide doped with chromium (Cr). The chromium ions (Cr+3) replace aluminum ions (Al) in the Al2O3 lattice, which provides metastable energy states within the solid-state medium.
• Figure 1 (not included here, but described) illustrates a typical ruby laser cavity arrangement. It consists of a cylindrical ruby crystal rod and a cylindrical flash lamp housed along the focal lines of an elliptical reflector. This configuration ensures that reflected light from the lamp effectively excites the crystal rod.
• Population inversion is achieved through flash lamp irradiation of the ruby rod. The flash lamp consists of a quartz tube filled with a noble gas. Helical-type flash lamps are sometimes employed in specific ruby laser types for even more effective carrier pumping.
• Water coolant is necessary to maintain the stability of this high-power laser system.
• Flashlight intensity depends on several factors, including capacitor size, applied voltage, tube diameter, gas pressure, and gas type.
• When a ruby laser is operated in pulse mode, it is possible to obtain very high-power light output. In summary, pumping is accomplished using flash lamps, and the laser operates in a pulsed regime.

Benefits (Advantages) of Ruby Lasers

The following are benefits or advantages of Ruby Lasers:

• They are economical.
• The beam diameter of a ruby laser is comparatively less than that of a CO2 laser.
• The output power of a ruby laser is not as low as that of a He-Ne laser.
• Ruby is in solid form; hence, there is no risk of wasting the active medium.
• Due to their low output power, they are sometimes classified as Class-I lasers, making them suitable as toys for children, decorative pieces, and artistic displays.

Drawbacks (Disadvantages) of Ruby Lasers

The following are the drawbacks or disadvantages of Ruby Lasers:

• Significant stimulated emission does not occur in a ruby laser until at least half of the ground-state electrons have been excited to the metastable state.
• The efficiency of this laser type is comparatively lower than other types.
• The optical cavity of this laser is short compared to other laser types.