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Coatingless Anti-reflection Device (i-ARD)

For the world's first we have succeeded in establishing a mass production process for fabricating a nanostructure on a fused silica substrate. This has enabled us to commercialize an inorganic coatingless AR device "i-ARD (inorganic-anti reflection device)" that has an excellent durability and reliability.

image:i-ARD

Product name Coatingless Anti-reflection Device (i-ARD)
Dimensions for STD sample Clear aperture :φ12mm(Outer dimension of holder :φ30mm)
Price for STD sample JPY 100,000(For reference only, consumption tax not included)
Release date Apr. 12, 2010
Production volume 1,000 pcs/year

In recent years, a moth-eye patterned film is known as a new anti-reflection technique. However, this polymer-based product is not durable enough for high power light applications such as laser machining.
As a light source in laser machining equipment, YAG laser is widely employed with modulated wavelength by harmony generation technique: fundamental wave(1064nm,) SHG of 532nm, THG of 355nmand FHG of 266nm.
In order to solve these problems we have developed a technique of fabricating nanostructure designed for AR function on substrate without giving any AR coating. As a consequence of the achievement we have succeeded in mass-manufacturing optical AR device which combines an excellent light resistance for high power and a broadband character at once.

Benefits

  • High transmittance and low reflectance in a wide range of wavelength from UV to IR (266-1200nm) in one device
  • Excellent durability against high power light due to its coatingless configuration
  • Applicable to any polarization state: linear, circular and non polarization
  • Incidence angle dependence is much lower than conventional thin film AR layer

Application

  • Optical window for high power solid state laser (e.g. Laser machining equipment)
  • Other equipment requiring broad bandwidth characteristics and light resistance

Specification

Dimension Aperture size 12mm square for standard sample
(Aperture size can be customized upon request.)
透過率 T>97% (266 ~ 340nm) and T>98% (340 ~ 1200nm) for non polarized light
T>98% (266 ~ 1200nm) for TM light*
Reflectance R<2%(266~340nm) and R<1%(340~1200nm)
Note Transmittance property can be customized upon request.

* When the polarization direction of linearly-polarized light is orthogonal to the optical axis of the device

What is different from conventional AR coating?

Until now optical multilayer coating (i.e. use of light interference) has been the most popular technique for adding anti-reflectivity to optical element. But our new product named "i-ARD (inorganic coatingless Anti-Reflection Device)" is of different concept of anti-reflection device. The i-ARD is not given any AR coating but fine nanostructure on its substrate (fused silica) surface for adding anti-reflectivity. This concept has brought great advantages. First, excellent high transmittance and low reflectivity for wide wavelength range have become available at one device.
Specifically, unlike the conventional coating film, there is no film interface, because a nanostructure is directly fabricated on the fused silica substrate. Due to its coatingless this technique completely avoids coating layer-derived problems: heat generation by absorbing light energy, deterioration of optical characteristics or weakening of layer adhesion etc. As a consequence new AR device has given excellent light resistance and durability.
The device is strong enough to be utilized in high power laser equipment, such as laser cutting machine.

Comparison test

Condition of a light resistance test
Type of Laser Mixed wave (355nm,532nm,1064nm) irradiation
Laser energy
(Laser wavelength: λ=355nm)
(1)Power : 250mJ
(2)Type : Pulse laser irradiation
(3)Beam diameter : φ9mm
(4)Frequency : 70Hz (Pulse width : 7~8nsec)
i-ARD No deterioration was shown with more than 50 million pulses irradiated
Conventional AR coating Performance degrade and damages on layer were shown

More than 100 times as durable as conventional AR coating

Spectrum Characteristics

image:Spectrum Characteristics

  • High transmittance and low reflectance in a wide range of wavelength from UV to IR (266nm~1200nm) in one device
  • Incidence angle dependence is much lower than conventional thin film AR layer

Application example

Optical window for high power solid state laser for laser machining

image:Application example

How the anti-reflection Window works

By sealing wavelength conversion elements to prevent crystal from deteriorating due to dust or deliquescence, and by making the ant-reflection effect broadband, optical feedback from the window, as well as degradation of the wavelength conversion elements, can be prevented.
(This is particularly a high-value added characteristic for THG or a higher harmonic that requires broad band.)