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High-Power Laser Optics

When it comes to precision optical components for high-power laser applications, standard optical coatings do not have the durability to withstand high-intensity irradiation. Specialized optical coatings are required.

At Blue Ridge Optics, we are experts in the development and application of optical coatings for high-power laser optic systems.

Knowing how high-power (high-energy) optics will perform means you need to measure the coating. At Blue Ridge Optics, metrology is our specialty. Our Surface Characteristic Mapping enables us to understand the relationship between optical surfaces and thin-film layering techniques in order to create the best optical coatings for your high-energy optics.

Give us a call at 540-586-8526 to learn more about our coatings for High-Power Laser Optics

How We Develop High-Power Optical Coatings

Substrate Preparation

Particulates and residue from polishing and cleaning optical components may result in unwanted laser energy absorption. It is essential to maintain rigorous standards at every stage of production from developing the initial substrate to packaging to ensure against absorption in high-power laser optics.

Substrates used in high-power applications commonly require low absorption raw substrate material, super-polished surfaces including sub-angstrom RMS roughness—which is better than 10-5 surface quality—and wavefronts (RWE/TWE) of better than lambda/20.

Maintaining the Standards of Cleanliness in Coating

Maintaining a clean coating chamber, selecting the best thin-film coating materials, and establishing and controlling deposition process parameters are also essential to the manufacture of high-powered laser optics. Blue Ridge Optics’ coating technicians work to control contamination called nodules that are deposited on the surface during the deposition process.

Our ISO-5 class clean-rooms minimize the risk of recontamination following the cleaning of optical components for coating.

Materials for High-Power
Laser Optics

Your application needs an optical system that operates within a certain range of wavelengths. At Blue Ridge Optics, we have the knowledge when it comes to applying coatings for both high-power continuous and high-power pulse irradiation laser applications. Continuous-wave lasers can cause an optical coating to overheat and melt, while short-pulse lasers generate high-intensity electromagnetic fields that can damage optics.

Our high-reflective mirror coatings, created by alternating layers of high-index and low-index materials can greatly reduce the laser-induced damage threshold (LIDT). When it comes to selecting the best low-index and high-index materials for high-powered coatings, we often use dielectric metal oxides due to their low absorption. Silicon dioxide is generally applied to create our low-index layers, while the materials we use in high-index layers vary by application: titanium oxides, zirconium, scandium, etc.

Process
Control

It is critical to set many parameters in the coating process for high-power laser optics. The rate of deposition, the temperature of the substrate, oxygen partial pressure, calibration of the thickness, preconditioning for material melt, and electron-gun sweeping are all important variables that need to be considered for these optical coatings.

For instance, if you don’t control the evaporation process, scatter will result. This can cause particulate condensation on both the substrate surface and coating. Materials used in the manufacture of high-powered optical coatings don’t easily cooperate during deposition. Achieving a smooth and even deposition requires an electron-gun sweep to ensure a high-damage threshold for your component.

Thin-Film Coating Design for High-Power Laser Optics

LIDT thresholds can be increased during the coating process. At Blue Ridge Optics, we use dual-monitored, Electron Beam deposition technology in creating our coatings for high-power laser optics. In combination with Ion-Assisted Deposition (IAD) and Advanced Plasma Assist (APA), E-Beam enables more concentrated coatings with properties that produce more compact thin film layers that lessen water absorption.

https://blueridgeoptics.com/precision-optics/thin-film-coating/

CNC Lens Manufacturing in Optical Fabrication

At Blue Ridge Optics, we have a number of tests used to determine the quality of optical coatings. Two methods for testing optical coatings for their ability to withstand laser damage are Damage Threshold Testing and Durability Certification.

Damage Threshold Testing: This process tests for failure. Irradiating the surface with a laser, we continue to increase output until the component is damaged.

Durability Certification: This is done according to precise specifications and testing parameters. These parameters might include pulse rate, pulse duration, pulse count, irradiance, and beam diameter.

Coating Failure Variables

Thin-film coating designers and technicians need precise parameters when testing optical components for their laser-induced damage threshold.

At Blue Ridge Optics, we have our pulsed high-power laser optics tested rigorously for Laser-induced Damage Threshold (LiDT). The main parameters & beam characteristics of this testing process are wavelength, pulse duration, temporal pulse shape, beam size/waist/focus, spatial intensity distribution, repetition rate, angle of incidence, polarization and mode of operation.

We also look at beam characteristics. These include:

Wavelength: As the laser wavelength DECREASES, the energy of the photon wave INCREASES. With this increase in energy comes an increase in the likelihood of laser-induced damage.
Mode of Operation: LiDT thresholds are lower for multimode lasers compared to single-mode lasers
Pulse Duration: Measured anywhere from femtoseconds in Ultra-fast applications to nanoseconds, the pulse duration is key to understanding the peak power experienced by your optical component. As the laser pulses get shorter, the same amount of energy equates to a higher peak power.
Temporal Pulse Shape: This shape refers to the intensity of the laser pulse plotted against the time domain. Pulse duration is generally pulled from this parameter by taking the length of time at full-width, half-max (FWHM) of the shape.
Beam Size/Waist/Focus and Spatial Intensity Distribution: As the laser beam size shrinks, the chance of laser damage increases—more power over less area. There are further nuances to the distribution of intensity across the size of the beam, but to first order, the beam waist is the main influencing variable.
Repetition Rate: The repetition rate refers to the number of laser pulses per second. As the pulse rate increases, the optic and coating has a shorter “cool-down” period, whether the chance of damage is from thermal or electronic effects.
Intensity Distribution: Testing for the distribution of energy intensity over the width of the beam.
Angle of Incidence and Polarization: Angle of incidence and polarization are intrinsically tied together. As the angle to the laser increases, reflectance from S-polarized light, while reflectance from P-polarized decreases. Depending upon your application, and whether the component is intended to reflect or transmit the laser beam, will determine how the laser damage is affected.

At Blue Ridge Optics, we pay close attention to the characteristics of our optical coatings as they relate to their intended irradiation sources. High-powered laser applications can easily lead to coating failure due to absorption or plasma burn.

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