Laser Technology Overview

Study Notes

Laser: Light Amplification by Stimulated Emission of Radiation
Components:
- Power Supply: Provides energy for laser operation.
- Lasing Medium: Can be gas, solid, or liquid, generates laser light.
- Pumping Device: Creates population inversion necessary for laser functioning.
- Optical Resonant Cavity: Houses reflecting surfaces where population inversion occurs.

Solid-State Lasers: Lasing material within a solid matrix (e.g., ruby); typically uses flash lamps as power source.
Semiconductor Lasers: Known as diode lasers; utilize p-n junctions, current serves as pump source; common in laser printers and CD players.
Dye Lasers: Utilize complex organic dyes for lasing.
Gas Lasers: Pumped by current; notable types include:
- Helium-Neon (He-Ne) Lasers: Operate in visible and infrared, with a typical wavelength of 632.8 nm.
- Argon Lasers: Output in visible and ultraviolet regions.
- CO2 Lasers: Emit infrared light, widely used for cutting hard materials.

Type: Solid-state laser utilizing a ruby crystal as gain medium.
Wavelength: Operates at 694.3 nm.
Construction: Uses aluminum oxide (Al2O3) with 0.05% chromium for its unique color.
Operation:
- Flash lamp energizes Cr3+ ions, promoting them to an excited state.
- Population inversion occurs when ions populate the metastable state.
- Spontaneous emission triggers stimulated emission, leading to coherent light output.
- Reflective mirrors direct and amplify photons; emits laser light through a partially silvered mirror.

Type: Small gas laser frequently used in scientific and industrial applications.
Wavelength: Typically operates at 632.8 nm, within the red visible light spectrum.
Mode: Functions in Continuous Wave (CW) mode; first continuous laser developed.

Wavelength: Measured in nanometers (nm); longer wavelengths provide greater tissue penetration.
Power Output: Expressed in watts (W) or milliwatts (mW), crucial for assessing laser safety and effectiveness.
Intensity: Power density is calculated as power divided by beam area; influences treatment efficacy.

Dosage: Reported in Joules per square meter (J/m²); relies on laser output, exposure time, and beam area.
Formula:
- Treatment time for a designated area: TA = (E/Pav) x A
  - TA: treatment time
  - E: energy in joules per m²
  - Pav: average power in watts
  - A: beam area in m²

Depend on the specific type of laser energy delivered.
Direct Effect: Results from photon absorption.
Indirect Effect: Chemical events resulting from tissue interaction with laser light.
He-Ne Absorption: Generally occurs within the first 2-5 mm of soft tissue with potential indirect effects extending beyond this range.