Optical Penetration Depth: The Hidden Variable
Understanding Optical Penetration Depth in Polymers
Optical penetration depth (δ) defines how deeply laser energy penetrates into a material before being absorbed. This critical parameter varies dramatically with wavelength and material composition:
δ = 1 / α
Where α is the absorption coefficient (cm⁻¹)
Wavelength vs. Penetration Depth in Engineering Polymers
Critical Relationship: Penetration Depth vs. Marking Quality
| Penetration Depth | Energy Distribution | Thermal Effect | Marking Result |
|---|---|---|---|
| < 50 μm | Surface concentrated | Minimal heat spread | Clean ablation, high contrast |
| 50-150 μm | Moderate depth | Controlled heating | Partial foaming possible |
| > 150 μm | Deep bulk absorption | Extensive heat accumulation | Severe foaming, poor control |
Material-Specific Penetration Depths
Our precision spectroscopic analysis reveals dramatic variations in optical penetration:
| Polymer | IR (1064nm) | Green (532nm) | UV (355nm) |
|---|---|---|---|
| PEEK | 380-450 μm | 120-180 μm | 25-40 μm |
| PEI (Ultem) | 290-350 μm | 90-140 μm | 20-35 μm |
| PC | 150-220 μm | 60-100 μm | 15-25 μm |
| PLA | 870-950 μm | 180-250 μm | 30-50 μm |