Optical Coatings

Laser Optics offers optical coatings that conform to the tightest military and industrial specifications. Capabilities include complex, high-efficiency, multilayer coatings designed for applications in the ultraviolet, visible, and infrared spectral regions.

Our chambers are designed for full-scale production, while having the ability to run smaller prototype jobs efficiently. We can accommodate large numbers of standard sized optics or large diameter single substrates.

Laser Optics uses state-of-the-art computer controlled coating processes for virtually all of our work. Optical monitors allow precision monitoring required for demanding coatings. By using a crystal oscillator for rate control we achieve consistent and reproducible results from run-to-run.

Our facilities include:

• Fully Automated Box Coaters
• Capability for Production Lots and Large Substrates
• Multiple e-beam Guns
• Ion Assisted Deposition Capabilities
• Low Temperature Coatings
• Class 1000 Clean Room
• Humidity and Temperature Controlled Laboratory
• Laser Damage Certification
• Environmental and Custom Test Equipment
• Automated Ultrasonic Substrate Cleaning
• Computerized Optical and Crystal Quartz Monitoring

Our coating repertoire includes anti-reflective, reflective, polarizing, and beamsplitter coatings for the UV, visible and infrared. Most of these coatings are designed specifically for high power laser applications. Lower power laser coatings include high reflectors, polarizing beamsplitters, and neutral density filters. Sol-gel coatings are available for glass or hygroscopic crystals. Laser Optics coats customer supplied materials (CSM) as well as in-house precision polished substrates. Short descriptions of typical coatings are included in the following sections.

High Power Laser Coatings

Coated UV, VIS, and NIR Optics

Laser Optics has developed particular expertise in the manufacture of components
and coatings for high power lasers -- Nd:YAG, Nd:glass, Ti-Sapphire, and Ruby.

All of these coatings are designed for high-energy laser applications. Special care is taken to prepare low-defect optical surfaces and to utilize damage resistant optical materials that are well suited for use with high field densities. All coating designs have been modeled to minimize the electric field intensity within the coating as much as possible.

Our multi-layer high power laser coatings are composed of electron-beam deposited refractory oxides. The result is a hard, extremely durable coating that is able to withstand repeated cleaning. Careful attention to detail in the manufacturing
process assures very low scatter and absorption.
 
Custom fabrication is performed routinely. If you are unable to find the specific
coating you require, contact us with your requirement for a prompt quotation.

Durability

All coatings pass the temperature requirements of MIL-M-13508C and the abrasion,
adhesion, humidity, salt fog and solubility demands of MIL-C-675 and MIL-C-48497.
These coatings can be cleaned repeatedly, utilizing industry-standard techniques.

Damage Threshold

Laser Optics does periodic testing on each of our coating designs to assure that they meet specified damage thresholds. Damage threshold certification for a specific coating run is available by special order at extra cost. For reflective and anti-reflective coatings, damage thresholds are the following.

≥1 GW/cm², pulsed*
> 5 MW/cm², cw*

*These damage thresholds refer to 1064 nm coatings deposited on fused silica.
 

AR Coatings
A number of different wavelength ranges can be accommodated on a variety of
substrates such as BK-7, fused silica, or filter glasses.

For example, windows can be anti-reflection coated for minimum loss at both 1064
nm and 633 nm to aid in laser alignment. Such coatings are optimized for use at
normal incidence. They are electron beam deposited and will pass the moderate
abrasion, adhesion, and solubility requirements of MIL-C-675C. Reflectivity is 0.3%
per surface at 1064 nm with <0.5% at 633 nm. Of course, the coating can be
designed for alternative wavelengths as well.

Another alternative is a window that is anti-reflection coated for minimum loss at
both 1064 nm and 532 nm for use in systems in which both the primary and
frequency doubled beams are transmitted. Such coatings are optimized for use at
normal incidence. These anti-reflection coatings are electron beam deposited and
will pass the abrasion, adhesion, and solubility requirements of MIL-C-675C.
Reflectivity is 0.3% per surface at 1064 nm with <0.5% at 532 nm.

Coatings, of course, can be optimized for a single wavelength at normal incidence, as shown below. These anti-reflection coatings are electron beam deposited and will pass the abrasion, adhesion, and solubility requirements of MIL-C-675C. Reflectivity is less than 0.2% per surface.

Specifications:
Material: Fused Silica, UV Grade
Optical figure: λ/10 @ 633nm
Surface: 20-10 per MIL-PRF-13830
R2: Plano, polished

Partial Reflectors
Partially reflective front reflectors have been designed for a wide variety of
commercial lasers. Coatings are all-dielectric refractory oxides, selected for low
absorption, low scatter, and resistance to high field intensities.

Specifications:
Material: Fused Silica, UV Grade
Optical figure: λ/10 @ 633nm
Surface: 20-10 per MIL-PRF-13830
R2: Plano, polished, AR coated

High Reflection Dielectrics
Mirrors with high reflectivity coatings are used as rear reflectors in a wide variety of
laser cavities. Reflectivity of Max-R coatings is >99.7%, typically with leakage of
<0.2%.

Specifications:
Material: Fused Silica
Optical figure:λ /10 @ 633nm
Surface: 20-10 per MIL-PRF-13830
R2: Plano, polished, AR coated

Dichroic Filters

Coatings can be designed as filters or beamsplitters for separating or combining laser beams of different wavelengths. All coatings are hard, all dielectric refractory
oxides. Typically, these components are anti-reflection coated on the rear surface.
Typical reflection for one wavelength is greater than 99% and transmission for the
other wavelength is greater than 90%.

Harmonic beamsplitters separate or combine harmonic laser beams such as 1064 nm and 532 nm. All coatings are hard, all dielectric refractory oxides. Typically, these components are anti-reflection coated on the rear surface. Typical reflection for one wavelength is greater than 99% and transmission for the other wavelength is greater than 90%.

Specifications:
Material: Fused Silica, UV Grade
Optical figure: /10 @ 633nm
Surface: 20-10 per MIL-PRF-13830
R2: Plano, polished, AR coated


Beam Folding Mirrors

Beam folding mirrors can have high reflectivity, for example, at 1064 nm and 632.8
nm for use in systems where a helium neon laser is used for alignment. Such
mirrors can be designed for use at 45° angle of incidence. Reflectivity is >99.5% at
1064 nm with >90% at 632.8 nm for randomly polarized beams. Reflectivity of s-
polarized beams will be slightly higher; p-polarized beams will be slightly lower than
the stated value. All coatings are hard, all-dielectric refractory oxides. Of course,
the high reflectivity wavelength can be changed upon application.

Specifications:
Material: Fused Silica, UV Grade
Optical figure: λ/10 @ 633nm
Surface: 20-10 per MIL-PRF-13830
R2: Plano, polished, AR coated

Harmonic beam folding mirrors can have high reflectivity at 1064 nm and 532 nm.
Such mirrors can be designed for use at 45° angle of incidence. Reflectivity is
>99.5% at 1064 nm and 532 nm for randomly polarized beams. Reflectivity of s-
polarized beams will be slightly higher; p-polarized beams will be slightly lower than
the stated value. All coatings are hard, all-dielectric refractory oxides.

Specifications:
Material: Fused Silica, UV Grade
Optical figure: λ/10 @ 633nm
Surface: 20-10 per MIL-PRF-13830
R2: Plano, polished, AR coated

Front surface mirrors can be designed to fold a single wavelength laser beam 90
degrees. All coatings are hard, all-dielectric refractory oxides.

Specifications:
Material: Fused Silica, UV Grade
Optical figure: /10 @ 633nm
Surface: 20-10 per MIL-PRF-13830
R2: Plano, polished, AR coated

Lower Power Laser Coatings

High Reflection Metallic, Protected Metallic, Enhanced Metallic

Metallic coatings of protected or enhanced aluminum, silver, or gold, can be selected for single wavelength or broadband applications.


Polarizing Beamsplitters

Fine optical finishing, advanced thin film deposition techniques, and superior
assembly procedures result in high precision polarizing beamsplitter (PBS) cube
assemblies by Laser Optics. Features include high contrast polarizing coatings,
precise dimension and optical pathlength control, excellent transmitted wavefront,
and tight tolerance on angles.
 

Neutral Density Filters

These optical elements are made by vacuum deposition of special metallic alloys on a
substrate of your choosing for broadband neutral attenuation at ultraviolet, visible,
or infrared wavelengths. Typical optical densities are 0.1, 0.3, 0.5, 1.0 and 2.0.
Since these elements have both reflective and absorptive components, they are not
suitable for use with high power density sources.


Filter Coatings (Short, Long, and Band Pass)

Short-wavelength-pass (SWP) and long-wavelength-pass (LWP) edge filters can be
deposited on a variety of high quality substrates. These coatings are more difficult
to produce than simple bandpass filters with the SWP being more difficult than the
LWP.


Custom Coatings

The above coating types are meant to be illustrative of the types of coatings
available from Laser Optics. As always, we would be glad to offer a quotation for
your particular custom application.


Substrates

Laser Optics has broad expertise in working with a wide range of substrate materials. A few of the more common substrate types are listed below.