Product Description
Precision 2″ (50.8mm) Diameter, 0.5″ (12.7mm) Thick Optical Mirror – Broadband Dielectric Coating
This precision 2″ (50.8mm) diameter, 0.5″ (12.7mm) thick optical mirror is crafted from a fused silica substrate, prized for its low thermal expansion, high optical clarity, and durability in varying environmental conditions. It features a multi-layer broadband dielectric coating that delivers exceptional reflectivity (>98-99%) across a wide visible to near-infrared wavelength range (approximately 400-1100nm), outperforming standard metallic coatings with lower absorption and higher laser damage resistance.
Fused silica is an ideal substrate for precision mirrors, offering excellent thermal stability, resistance to thermal shock, and high purity that minimizes absorption and scatter . Dielectric coatings provide superior performance compared to metallic coatings, with higher reflectivity and greater durability in high-power laser applications .
Key Specifications
| Specification | Details |
|---|---|
| Diameter | 2 inches (50.8 mm) |
| Thickness | 0.5 inch (12.7 mm) |
| Substrate Material | Fused silica (UV-grade) |
| Coating Type | Multi-layer broadband dielectric |
| Reflectivity | >98-99% across 400-1100 nm |
| Wavelength Range | Visible to near-infrared (400-1100 nm) |
| Surface Quality | High-grade (specifics unknown) |
| Surface Figure | Precision grade (specifics unknown) |
| Clear Aperture | >90% of diameter (typical) |
| Parallelism | Precision grade (typical for laser mirrors) |
| Back Surface | Uncoated / commercial polish |
| Condition | Great surplus condition overall |
Condition Note – Minor Scratch
The mirror is in great surplus condition overall, with only a minor fragmented straight line scratch in one place near the center. This cosmetic defect may have negligible impact for non-critical applications.
Practical Impact of Minor Scratches:
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Visual use (telescopes, imaging): Minor scratches often have negligible impact on visual performance. As noted in astronomy forums, “unless the issue described is a significant damage, the answers are constantly the same: ‘…you won’t notice a difference for visual use…'”
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Laser applications: May cause minimal scatter depending on beam size and location. For applications where the beam can be positioned away from the scratch, impact is minimal.
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Non-critical setups: Ideal for educational, prototyping, or alignment applications where absolute perfection is not required.
This scratch represents an opportunity to acquire a high-quality precision optic at a significant discount compared to new equivalents.
Material Advantages – Fused Silica
Fused silica offers exceptional properties for precision optical mirrors :
| Property | Benefit |
|---|---|
| Low Thermal Expansion | Maintains figure under temperature changes – ideal for laser systems |
| High Thermal Shock Resistance | Can withstand rapid temperature changes |
| High Purity | Minimizes absorption and scatter |
| Excellent Durability | Resists abrasion and environmental degradation |
| Broadband Transmission | Excellent performance from UV through near-IR |
Dielectric Coating Advantages
Dielectric coatings offer significant advantages over metallic coatings :
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>98-99% Reflectivity: Significantly higher than metallic coatings (typically 90-96%)
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Lower Absorption: Reduced heating in high-power applications
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Higher Laser Damage Threshold: Suitable for demanding laser systems
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Durability: Hard, environmentally stable coatings resistant to cleaning
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Broadband Performance: High reflectivity across entire 400-1100nm range
Daheng Optics’ broadband laser mirrors with similar specifications (fused silica substrate, 400-700nm, 50.8mm diameter, 9mm thickness) offer >99% reflectivity and laser damage thresholds >5J/cm² . This mirror’s 12.7mm thickness provides enhanced rigidity and thermal management.
Applications
Laser Beam Steering:
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Ideal for directing laser beams in research, industrial, or educational setups
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High reflectivity minimizes power loss in beam delivery systems
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Broadband coating accommodates multiple laser wavelengths
Optical Alignment:
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Precision reference for aligning optical systems
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Visible coating aids in visual alignment with HeNe or diode lasers
Scientific Instruments:
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Spectrometers and interferometers
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Imaging systems and telescopes
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Machine vision and inspection systems
Research and Education:
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University and laboratory optics experiments
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Photonics and laser demonstrations
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Prototyping and system development
Custom Optics Projects:
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Beam expanders and telescopes
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Optical path folding
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Multi-wavelength experiments
Comparative Value – New vs. Surplus
| Parameter | This Mirror | New Commercial Equivalent |
|---|---|---|
| Diameter | 2″ (50.8 mm) | 2″ (50.8 mm) |
| Thickness | 12.7 mm | 6-10 mm typical |
| Substrate | Fused silica | Fused silica |
| Coating | Broadband dielectric, 400-1100nm | Broadband dielectric |
| Reflectivity | >98-99% | >99% typical |
| Surface Quality | High-grade (minor scratch) | 20-10 scratch-dig typical |
| Condition | Great overall, minor scratch | New |
| Typical New Price | — | $200-$400+ |
| This Price | $125 OBO | Exceptional value |
Condition Summary
| Aspect | Description |
|---|---|
| Overall Condition | GREAT – excellent optical quality throughout |
| Surface Defect | Minor fragmented straight-line scratch near center |
| Impact on Use | Negligible for most non-critical applications |
| Coating Integrity | Excellent throughout, unaffected by scratch |
| Substrate | No chips, edge damage, or other defects |
| Readiness | Ready for immediate integration |
⚠ NOTE: The minor scratch is described accurately to ensure full transparency. For many applications, this will have no practical impact on performance .



