Topic Briefing Sheet for Laser Physics and Technology

Fundamentals of Laser Physics and Technology

Purpose

To provide learners with assessor-prepared notes summarising core laser physics concepts, terminology, principles, and UK regulatory context relevant to the safe operation of laser systems.

Introduction to Laser Physics

A laser (Light Amplification by Stimulated Emission of Radiation) is a device that emits a highly controlled, concentrated beam of light. Laser safety officers must understand the physics behind laser generation to ensure safe workplace practices.
Lasers differ from ordinary light sources because they exhibit coherence, monochromaticity, and directionality, allowing extremely high energy concentrations that pose hazard risks to skin, eyes, and materials.

Basic Principles of Laser Generation

Laser production involves three essential stages:

Stimulated Emission

Occurs when an excited atom/molecule releases a photon after stimulation by a matching photon.

Population Inversion

More atoms must be in an excited state than in a resting state to sustain laser action.

Optical Resonance (Cavity)

Mirrors on both ends of the laser medium reflect photons back and forth, amplifying the light.

Workplace relevance:

Understanding these principles helps LSOs evaluate hazards such as beam intensity, reflective surfaces, and equipment malfunction.

Key Light and Laser Properties

Wavelength (nm or µm)

Distance between consecutive peaks of a wave. Determines:

  • Penetration depth in tissue
  • Absorption by materials
  • Laser colour
    • Example: 1064 nm (Nd:YAG) penetrates deeper into tissue; 532 nm (KTP) targets pigment.

Beam Divergence

The spread of the laser beam over distance. Low divergence = highly focused, high-risk beam.

Coherence

Laser photons are in phase and travel uniformly, enabling precise cutting, focusing, and energy delivery.

Monochromaticity

Laser light contains a single wavelength, unlike ordinary white light.

Types of Lasers

Medical Lasers

  • CO₂ (10,600 nm): surgical cutting, dermatology.
  • Diode (800–980 nm): hair removal, vascular procedures.
  • Nd:YAG (1064 nm): coagulation, vascular use.

Industrial Lasers

  • Fiber lasers: metal cutting, welding.
  • CO₂ lasers: engraving and machining.

Aesthetic Lasers

  • Alexandrite (755 nm): hair removal.
  • IPL (intense pulsed light – not a laser but regulated similarly).

Laser–Material / Tissue Interactions

Laser energy interacts with materials via:

Absorption

Material absorbs photons → heat, cutting, coagulation.

Reflection

Can cause accidental beam exposure; requires controlled environments.

Scattering

Light disperses unpredictably, increasing risk of diffuse exposure.

Transmission

Laser energy passes through material and may impact underlying structures.

Example: In medical aesthetics, melanin absorption determines hair removal effectiveness and safety.

Laser Performance & Efficiency Factors

Key factors affecting output:

  • Laser medium quality (e.g., crystal purity)
  • Mirror alignment inside cavity
  • Cooling systems
  • Electrical power stability
  • Beam focusing lenses
  • Pulse duration & repetition rate

Poor maintenance reduces efficiency and increases hazard potential.

Continuous-Wave (CW) vs Pulsed Lasers

Continuous-Wave Lasers

Emit a constant, uninterrupted beam.
Use: metal cutting, CO₂ surgical systems.

Pulsed Lasers

Emit short bursts of high-energy light.

Types of pulses:

  • Q-Switched: nanosecond pulses (tattoo removal)
  • Long-pulsed: milliseconds (hair removal)
  • Ultrashort (fs, ps): precision applications

Pulse duration influences tissue effects and risk levels.

Common Components of Laser Systems

  • Laser medium: gas, crystal, semiconductor.
  • Pump source: flashlamp, electrical current, diode.
  • Optical cavity mirrors: amplify light.
  • Cooling systems: prevent overheating.
  • Beam delivery systems: fibers, articulated arms.
  • Control interface: power, wavelength, pulse settings.

Applying Laser Physics to Workplace Safety

Understanding these principles helps LSOs:

  • Identify beam hazards (eye/skin risk).
  • Select correct PPE and protective eyewear (matched to wavelength).
  • Control reflective surfaces and alignment procedures.
  • Implement controlled area signage and access restrictions.
  • Ensure equipment maintenance enhances safe operation.
  • Perform risk assessments based on wavelength, pulse type, and interaction potential.

UK Legislation and Standards for Laser Use

Laser safety responsibilities in the UK follow:

Key UK Regulations:

  • The Control of Artificial Optical Radiation at Work Regulations 2010 (AOR).
  • Health and Safety at Work Act 1974.
  • Management of Health and Safety at Work Regulations 1999.
  • COSHH Regulations 2002 (for laser plume exposure).

Relevant UK/International Standards:

  • BS EN 60825-1: Safety of laser products.
  • BS EN 60601-2-22: Medical laser equipment safety.
  • BS EN 207 & BS EN 208: Protective eyewear standards for lasers.
  • BS EN ISO/IEC 17025: Calibration and testing laboratories.

These define exposure limits, classification, testing, signage, shielding, and control measures.

Learner Task

Instructions:

  1. After studying the Topic Briefing Sheet, summarise in your own words:
    o The process of laser generation.
    o The difference between continuous-wave and pulsed lasers.
    o How wavelength affects tissue/material interaction.
  2. Identify three workplace decisions an LSO must make that require understanding of laser physics.
  3. Cite the specific UK regulation or standard that informs each decision.