The meaning of the parameter indicators of 99.999% PLANAR REFLECTO

99.999% PLANAR REFLECTOR (Ultra-High Reflectivity Planar Mirror) Parameter Index Meanings (Technical Description)

UltraOpto 99.999% PLANAR REFLECTOR (Ultra-High Reflectivity Planar Mirror) is a core component for high-end optical applications such as deep ultraviolet lithography, excimer laser systems, and high-precision spectral analysis. Its parameter indices directly determine the performance ceiling of optical systems. The following are professional explanations of the core parameter indices to assist customers in precise selection and application.

I. Core Optical Performance Indicators

1. Reflectivity: 99.999%

This is the core index of the planar mirror, indicating that the ratio of the reflected light flux to the incident light flux in the target wavelength band reaches 99.999%, meaning the light loss is only 0.001%.

For deep ultraviolet bands (such as 193nm), this index can significantly reduce energy attenuation during laser transmission, ensuring the accuracy of lithography and the stability of the laser system;

The realization of this index depends on the precise design and deposition of multi-layer dielectric films, with the film thickness deviation needing to be controlled within ±0.2nm.

2. Operating Wavelength

Refers to the effective spectral range in which the mirror maintains a 99.999% ultra-high reflectivity. Common specifications include deep ultraviolet (193nm/248nm), visible light (400-760nm), near-infrared (760-1100nm), etc.

The wavelength band selection needs to match the specific application scenario. For example, the 193nm band is specifically designed for deep ultraviolet lithography equipment, and the substrate needs to be UV-grade fused silica with low hydroxyl content.

3. Surface Roughness (Ra)

Refers to the arithmetic mean deviation of the microscopic contour of the mirror surface. The Ra value of UltraOpto's series of mirrors is ≤0.01nm.

This index determines the scattering loss of the mirror surface. The lower the roughness, the less stray light, and the higher the signal-to-noise ratio of the optical system;

It needs to be achieved through ultra-precision polishing processes, and the polishing environment needs to meet 10-level cleanliness, constant temperature and humidity (20±0.1℃, 40±5% RH) requirements.

II. Key Geometric Precision Indicators

1. Flatness

Measures the deviation of the mirror surface from an ideal plane. The flatness of UltraOpto's series of mirrors reaches λ/[email protected] (λ is the wavelength of helium-neon laser, approximately 632.8nm).

λ/20 represents a surface deviation of less than 31.64nm, ensuring no wavefront distortion after the incident light is reflected, suitable for devices with extremely high requirements for beam quality, such as laser resonators and interferometers;

It needs to be detected and corrected in real time through a phase-shifting interferometer.

2. Parallelism

Refers to the tilt deviation of the two optical surfaces of the mirror, with an index of ≤0.1arcmin.

Non-compliance with parallelism standards will cause the reflected light direction to shift, affecting the alignment accuracy of the optical system's light path;

It needs to be achieved through dedicated fixtures and real-time calibration during the grinding and polishing process.

3. Dimensional Tolerance

Covers the allowable deviations of the mirror's diameter, thickness, and other dimensions. The conventional specification diameter tolerance is ≤±0.05mm, and the thickness tolerance is ≤±0.05mm.

The dimensional tolerance needs to match the installation interface of the customer's optical system. Customized dimensions are supported for irregular shapes.

III. Environmental Reliability Indicators

1.Tested according to ISO 15184 standard, the index is ≥5B grade. 

5B grade indicates that after peeling off with tape, there is no film layer detachment or scratch, ensuring the stable operation of the mirror in complex environments such as high and low temperatures and vibration. The film layer and substrate adhesion must be strengthened through post-coating annealing treatment.

2. Laser-induced damage threshold (LIDT)

The conventional index is ≥500mJ/cm²@193nm, 10ns pulse. This index represents the maximum laser power density that the mirror surface can withstand. The higher the value, the more suitable it is for high-power laser systems. It is directly related to the purity of the substrate and the density of the film layer.

3. Temperature and humidity stability

It can withstand temperature cycling from -40°C to 85°C and a humid heat environment of 85% RH. After the test, the reflectivity attenuation is ≤±0.0002%. This ensures that the performance of the mirror does not drift under different working conditions, meeting the long-term usage requirements of industrial-grade equipment.

Parameter selection suggestions

If used in deep ultraviolet lithography, it is recommended to choose the model with a 193nm band, surface shape accuracy of λ/20, and a laser-induced damage threshold of ≥500mJ/cm².

If used in aerospace optical equipment, additional attention should be paid to temperature and humidity stability and anti-vibration performance. Custom vacuum-compatible models can be made.

When there are no special coating requirements, the delivery cycle of conventional products is shorter. Customized coating systems require an additional 3-5 days for research and development and production.

UltraOpto 99.999% flat mirrors, through strict parameter control and full-process quality control, provide high stability and high-precision core components for high-end optical systems.