Dielectric high-reflection coatings delivering >99.5% reflectance for laser resonators, interferometers and precision optical systems. Superior to metallic mirrors in reflectance and laser damage threshold.
High-reflection dielectric coatings use alternating quarter-wave stacks of high and low refractive index materials to create constructive interference for reflected light. Each interface contributes a small reflection that adds coherently.
A typical HR design uses 20-40 alternating layers of Ta2O5 (n≈2.1) and SiO2 (n≈1.46). The reflectance bandwidth increases with the index contrast ratio. More layer pairs yield higher peak reflectance.
Unlike metallic mirrors that absorb 2-15% of incident light, dielectric HR mirrors can achieve total reflectance exceeding 99.99% with minimal absorption (< 10 ppm). This makes them essential for high-finesse optical cavities and high-power laser systems.
The reflectance bandwidth of a standard HR coating is typically 5-15% of center wavelength. Broader bandwidth designs require more layers or specialized designs like chirped mirrors for ultrafast laser applications.
| Parameter | Typical Values | Notes |
|---|---|---|
| Reflectance | > 99.5% (up to 99.999%) | At design wavelength |
| Wavelength Range | 248nm - 10.6μm | Deep UV to far-IR |
| Bandwidth | 5-15% of center λ | Custom designs available |
| Absorption Loss | < 50 ppm typical | IBS deposition |
| LIDT (ns pulses) | Available: 10-60 J/cm² | 1064nm, 10ns, ISO 21254 |
| LIDT (CW) | Available: 5-50 MW/cm² | Depends on absorption |
| Surface Quality | 20/10 to 60/40 scratch-dig | Per MIL-PRF-13830 |
| Flatness | λ/10 to λ/2 | At 632.8nm |
| Deposition | IBS, IAD, e-beam | IBS for highest LIDT |
| Material Pair | Index Contrast | Range | Application |
|---|---|---|---|
| Ta2O5/SiO2 | 2.1/1.46 | 350nm-10μm | General laser HR |
| HfO2/SiO2 | 1.9/1.46 | 250nm-10μm | High-LIDT UV-VIS |
| TiO2/SiO2 | 2.35/1.46 | 400nm-8μm | Visible broadband HR |
| Al2O3/SiO2 | 1.63/1.46 | 200nm-4μm | Deep UV HR (193nm+) |
| ZnS/YbF3 | 2.2/1.5 | 2-12μm | IR HR mirrors |
| Ge/SiO2 | 4.0/1.46 | 2-14μm | Far-IR HR |
HR mirrors form the cavity end mirrors in solid-state, fiber and gas lasers. Requirements: R > 99.8%, high LIDT, low absorption.
High-finesse Fabry-Perot interferometers require R > 99.9% mirrors for narrow linewidth filtering and precision metrology.
Fold mirrors in laser beam delivery systems need HR coatings at the operating wavelength with minimal wavefront distortion.
Cavity-enhanced filters and wavelength-division multiplexing devices use HR coatings as part of thin-film filter stacks.
PhotonEdge offers coated optical components compatible with High-Reflection (HR) Coatings. Explore related products below.
State-of-the-art dielectric mirrors can achieve R > 99.999% using 40+ layer designs with IBS deposition. Such mirrors are used in gravitational wave detectors and cavity QED experiments.
Dielectric HR mirrors offer higher reflectance (>99.5% vs 85-95% for metals), higher LIDT, and lower absorption. However, they are wavelength-specific, while metallic mirrors work across broad spectral ranges.
LIDT varies by material and deposition. Ta2O5/SiO2 by IBS typically achieves 30-60 J/cm² at 1064nm/10ns. HfO2/SiO2 designs for UV can reach 10-20 J/cm² at 355nm.
Yes, but the design must be optimized for the specific AOI. The reflectance band shifts toward shorter wavelengths at oblique angles, and s/p polarization splitting occurs.
Our optical engineers can help you select or design the optimal coating for your application.
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