Why is copper so difficult to cut with fiber laser?

Copper reflects ~95% of near-infrared (1070nm) radiation at room temperature. However, once copper starts melting, absorption increases dramatically to 50-70%. The challenge is getting enough energy coupled into the material to start the melt. Solutions: 1) Use green laser (532nm) - copper absorbs 40%+ at this wavelength. 2) Use higher power fiber with fast piercing. 3) Surface treatment to increase initial absorption. 4) Blue laser (450nm) for thin copper.

How does surface condition affect laser absorption?

Polished surfaces: Maximum reflectivity, minimum absorption. Ground/machined: 1.2-1.5× absorption vs polished. Rough/sandblasted: 1.5-2× absorption - light scatters and has multiple reflection opportunities. Oxidized: Oxide layer significantly increases absorption (2-3× for steel). Painted/coated: Absorption often 80-90% initially, then drops to base material value once coating burns off.

Does absorption change during laser processing?

Yes, dramatically for metals. Cold absorption is lowest. As material heats: 200-500°C: Absorption increases 1.5-2×. At melting point: Absorption jumps 2-3×. In keyhole (vaporization): Absorption can reach 70-90% due to multiple reflections in the vapor cavity. This is why high-power lasers can process reflective materials - once the keyhole forms, efficiency increases. Initial "coupling" is the challenge.

Material Absorption Calculator

⚡ Quick Answer: Why Fiber vs CO₂?

Metals: Fiber (1070nm) absorbs 30-45% vs CO₂ 5-10% → Fiber wins | Organics: CO₂ (10.6μm) absorbs 90-95% → CO₂ only

Understand why different laser wavelengths work better for different materials. Calculate absorption, reflectance, and get laser type recommendations.

Material

Surface Condition

Laser Wavelength

Absorption Analysis

Select material and wavelength to see absorption analysis.

Laser Absorption by Material & Wavelength

Material	Fiber (1070nm)	CO₂ (10600nm)	Green (532nm)	Best Laser
Mild Steel	35%	5%	42%	Fiber
Stainless Steel	32%	8%	38%	Fiber
Aluminum	8%	3%	15%	Fiber (high power)
Copper	5%	2%	40%	Green / Blue
Wood	25%	95%	30%	CO₂ only
Acrylic	5%	95%	8%	CO₂ only

Values at room temperature for ground/machined surfaces. Absorption increases significantly at elevated temperatures.

Frequently Asked Questions

CO₂ laser wavelength (10.6μm) is strongly absorbed by organic materials - wood and acrylic absorb ~95% of the energy. Fiber laser wavelength (1.07μm) passes through or scatters in these materials with only ~5-25% absorption. The 10.6μm wavelength excites molecular vibrations in polymers and organic compounds, causing efficient vaporization. This is why CO₂ is the only practical choice for cutting wood, paper, fabric, leather, and most plastics.

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CO₂ vs Fiber Guide

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Cutting Reflective Materials

Tips for copper, brass, aluminum

Note: Absorption values are approximate for typical industrial conditions. Actual absorption varies with surface finish, temperature, alloy composition, and beam angle. For highly reflective materials, consider starting with lower power and back-reflection monitoring.