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Optical Coatings

Optical Coatings

Optimax has a range of thin film coating technologies available that can be tailored to best satisfy each customer’s spectral, environmental, mechanical and laser damage threshold requirements.

You’ll get finished optics faster and with less risk because of our ownership of the complete manufacturing process, which includes:

  • Coatings for wavelengths from 193nm to 6000nm
  • Sizes up to 500mm
  • World class high laser damage threshold coatings for CW and pulsed applications
  • The ability to deterministically correct coating uniformity on curved surfaces
  • Shift free, durable coatings
  • Coating stress tuning for improved wavefront control
  • Qualified for use in space

We can coat optics manufactured at Optimax, or in some cases optics supplied directly by our customers.

In-house Coating Facility

Optimax’s in-house equipment and expertise takes the risk out of this critical step. Our new state-of-the-art, 4,000 sq. ft. optical coating Close_up_coating_alleyfacility (complete in July 2013) houses eight optical coating chambers, three environmental testing chambers and metrology equipment for DUV through IR.

The facility has been designed to ensure the highest quality coatings across apertures up to 500mm; with considerations for cleanliness, safe handling and environmental control in testing. Our coating chambers are housed in a class 10,000 environment. Prior to coating, optics are cleaned and inspected in a class 100 environment using processes with demonstrated performance in semiconductor and high energy laser fusion applications.

Optical Coating Design

Optimax typically designs and manufactures custom coatings that are specific to each customer’s requirement. Our engineers have years of experience designing and manufacturing antireflection, mirror, beamsplitter, filter and polarization control coatings and can design coatings that will best meet your optical, mechanical, environmental and laser damage requirements.

We will work with you during the design phase to ensure that the optical balance of performance, maufacturability and cost of coating specifications. Optimax coating engineers strive to provide the industries best customer service.

Typical Optical Coating Designs

For more information please see Optimax’s Thin Film Coating Limits

Coating Uniformity

Error Free SurfacesIt is easy to introduce low and mid-spatial frequency errors when depositing an optical coating if no consideration for thickness uniformity is given during coating chamber design. These non-uniformities can cause changes in reflectance, transmittance and phase across different regions within the clear aperture of the optic. For optics with challenging spectral requirements, or significant curvature, it can become impossible to address these non-uniformities only through coating design.

Optimax has developed software that allows our engineers to model and correct uniformity for a wide range of optic geometries. Solutions for a wide range of spherical and aspheric surfaces are currently within our portfolio. Custom solutions can typically be engineered and implemented within 2-3 weeks.

Laser Damage Threshold

Laser

Optimax coatings have demonstrated performance in high-fluence pulsed and CW laser applications. Our coating and cleaning processes have been developed under National Ignition Facility and Omega laser guidelines to achieve low defect counts, low absorption and highest laser damage thresholds.

All coating operations are performed in a Class 10,000 environment. Cleaning and inspection are performed in a Class 100 environment. Our engineers have years of experience with designs (standing wave electric field control) and processes that have been developed specifically for high-fluence laser applications.

Laser damage testing is done by a certified independent third party. The following table gives an overview.

High Laser Damage Threshold Antirefelection Coating Performance
Wavelength
Pulse Length
Typical Specification
Demonstrated Optimax Performance
Notes
1064 nm 10 ns >30 J/cm² 65 J/cm² N/A
1064 nm 3 ns >15 J/cm² 40 J/cm² N/A
1064 nm 10 ps >1 J/cm² N/A not tested to failure
351 nm 3 ns >3 J/cm² 7 J/cm² N/A
266 nm 15 ns >3 J/cm² 11 J/cm² N/A
1064 nm CW >1 MW/cm² >4 MW/cm² topped out laser
1572 nm CW >1 MW/cm² >2.1 MW/cm² topped out laser

*inspection typically done under 100-200x Nomarski brighfield illumination
**pulsed testing results typically fluence at which 0 defects were found after raster testing many sites, 5-10Hz, per LLNL Spec NIF-5008633 MEL01-013-OD protocol

OTR Coatings

Optimax has developed a unique optical coating (OTR-AR) that protects optical surfaces in the most extreme environmental conditions. OTR coatings have proven to be resistant to latent

scratching, staining and dimming of chemically sensitive optical glass surfaces in humid environments.

 

For more information please see:

Testing Coatings

Optimax has four spectrophotometers that can measure coating performance at wavelengths from 175nm to 50 microns. Coating performance can also be measured as a function of polarization and angle of incidence (0 to 68°). Spectral calibration of these instruments is performed routinely using NIST traceable standards. Instruments are located in an environmentally controlled area and local enclosures can be used to match the customer use environment during testing to within +/- 2%RH.

Adhesion, abrasion, humidity, temperature, and solubility tests are available in-house to verify coating durability in accordance with sections of MIL-C-675C, MIL-C-48497A and MIL-M-13508C specifications. Laser damage testing is also available upon customer request.

For more information please see:

Coated Wavefront Control

Coating Stress

Stress in optical coatings can bend optics and change wavefront and as coating thickness, aspect ratio and coating stress increase so does the magnitude of bending. Coatings deposited using Ion Beam Sputtering (IBS) processes typically have high stress and can change optical wavefront after coating significantly.

Optimax has the ability to tune its dielectric mirror and filter coatings to near neutral stress. The processes used to realize neutral stress are often specific to the substrate on which the coating is being deposited.

Thermal Distortion

Coating stress induced bending of AR coated optics is often insignificant as the coating thickness is small and the coatings on opposite surfaces have equal and opposite effects (net neutral). Distortion can occur, however, when applying an AR coating to lenses made from thermally sensitive glasses. We understand these considerations and can provide durable, near room temperature coatings to ensure the best optical wavefront.

Optimax Coatings in Space

Optimax coatings are qualified to use in space; dosed with MRad’s of Gamma radiation by independent laboratories without exhibiting a measurable change in spectral performance. We use space qualified processes, which are both mechanically and spectrally robust in vacuum coatings tested spectrally under conditions representative of vacuum use.

Specifying Coatings

Coatings

Specifying coatings begins with the desired transmission or reflection requirements of the optical components surfaces, along with the wavelength band(s) of interest and angle of incidence (AOI). Other aspects to consider when specifying coatings include polarization requirements, laser damage threshold, witness sample requirements, coating aperture and environmental requirements. Pulsed laser damage threshold requirements should include both wavelength, pulse length and repetition rate, which are usually specified in J/cm². CW damage thresholds are typically specified as average power in w/cm².

An example coating specification is given below:

  • RAVG < 0.5% from 1042 to 1062nm, AOI = 0-20°, average polarization
  • Coating to withstand environmental durability requirements for Adhesion, Humidity and Moderate abrasion per MIL-C-48497A (Para 3.4.1.1-3.4.1.3).
  • Laser Damage Threshold Requirements: >5 J/cm^2 at 10ns pulse length, 1052nm, 10 H²
  • Coatings aperture is equal to the component clear aperture

For more information please see:

Quality Assurance

Optimax inspects 100% of all optics. Test data is provided with prototype orders. The use of state-of-the-art metrology assures customer satisfaction.

For more information on different measurement and inspection options please see:

Fast Delivery

Optimax manufactures a wide variety of optical components. When on-time delivery is crucial, Optimax offers an expedited delivery option with a money back guarantee.

For more information please see the information on Optimax’s On-Time Guarantee.

 

 

 

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