Metric showing ablationThreshold with value 2.2 J/cm², ranging from 2 to 6 J/cm². Press Enter or Space to search for this metric.
Ablation Threshold
Current value: 2.2 J/cm². Range: 2 to 6 J/cm². Progress: 5% of maximum.
2.2
J/cm²
Fused Silica Laser Cleaning
Precision Laser Cleaning Restores Fused Silica's Optical Purity
Todd DunningMA
Optical Materials for Laser Systems
United States (California)
Properties: Fused Silica vs. other glasses
Laser-Material Interaction
Material Characteristics
Other Properties
Machine Settings: Fused Silica vs. other glasses
Fused Silica surface magnification
Laser cleaning parameters for Fused Silica
Before Treatment
Under microscopy, fused silica's contaminated surface reveals clustered particulates and oily residues, forming hazy films. Contaminants manifest as submicron to 5-micron irregular specks, likely airborne dust or handling oils. Surface degradation shows micro-pitting and subtle etching, reducing optical clarity in laser diode assembly.
After Treatment
After cleaning, fused silica surfaces restore to pristine optical clarity, preserving full material integrity and smoothness. This supports reliable performance in laser system optics for precision manufacturing.
Fused Silica Laser Cleaning FAQs
Can fused silica be laser cleaned without causing damage or micro-cracks?
Yes, fused silica can be safely laser cleaned by carefully controlling parameters. Using a 1064 nm wavelength with a fluence below 2.5 J/cm² and nanosecond pulses minimizes thermal shock risks to its amorphous structure. This approach effectively removes contaminants while preventing subsurface damage and micro-crack formation in the glass.
What is the best laser wavelength for cleaning contaminants from fused silica optics?
For fused silica optics, UV wavelengths around 355nm are superior. They are strongly absorbed by most contaminants, enabling effective ablation at fluences below the substrate's ~2.5 J/cm² damage threshold. This provides the necessary separation to clean thoroughly without harming the optic's surface.
How do you remove thin film coatings from fused silica using a laser without etching the surface?
We use 1064 nm nanosecond pulses at ~2.5 J/cm² to selectively ablate thin films. This fluence is above the coating's ablation threshold but safely below the level that would etch the pristine fused silica substrate.
What are the LIDT (Laser-Induced Damage Threshold) concerns when laser cleaning fused silica optics?
Laser cleaning near the 2.5 J/cm² threshold risks creating microscopic damage precursors, which can lower Fused Silica's LIDT. Post-cleaning measurements often reveal a reduced damage threshold from these subsurface modifications, compromising performance in high-power systems.
Does laser cleaning create OH group contamination or other chemical changes on the fused silica surface?
Properly configured laser cleaning below the 2.5 J/cm² threshold avoids OH group formation. However, excessive fluence can induce surface chemistry changes, potentially increasing hydrogen bonding and degrading UV transmission. Maintaining optimal parameters is critical for long-term optical stability.
What safety precautions are specific to laser cleaning fused silica compared to metals?
The key precaution is staying below fused silica's 2.5 J/cm² damage threshold to prevent subsurface cracking. Unlike metals, its low thermal conductivity creates stress fractures. Always use respiratory PPE for the fine silica particulates generated.
How effective is laser cleaning for removing sub-surface damage (SSD) in fused silica?
Laser cleaning can mitigate existing sub-surface damage when operated below fused silica's ~2.5 J/cm² damage threshold. However, exceeding this fluence with 10 ns pulses will certainly introduce new microfractures, defeating the conditioning objective.
Can laser cleaning replace traditional methods like CO2 snow or solvent cleaning for fused silica in cleanroom environments?
Laser cleaning effectively replaces traditional methods for fused silica, achieving superior particle removal below 2.5 J/cm². This non-contact process, using 1064 nm wavelength, eliminates organics without solvents, enhancing throughput and enabling validation via light scatter testing for critical optics.
What is the maximum allowable surface temperature during laser cleaning of fused silica to prevent thermal stress failure?
Fused silica's remarkably low 0.55 ppm/°C thermal expansion coefficient allows surface temperatures up to approximately 300°C before stress failure. To maintain this, keep your fluence below the 2.5 J/cm² damage threshold and utilize high 500 mm/s scan speeds to minimize localized heating and prevent destructive thermal gradients.
How do you verify the success of a laser cleaning process on a fused silica optic?
Verification requires multiple techniques. We confirm surface integrity using white-light interferometry, ensuring no profile change above 2 nm. Scatterometry checks for residual particles, while transmission measurements at 1064 nm must show no degradation from the baseline. This multi-faceted approach guarantees the optic's performance is fully restored.
Regulatory Standards & Compliance
FDA
FDA 21 CFR 1040.10 - Laser Product Performance Standards
ANSI
ANSI Z136.1 - Safe Use of Lasers
IEC
IEC 60825 - Safety of Laser Products
OSHA
OSHA 29 CFR 1926.95 - Personal Protective Equipment
