The materials that are used for laser optics will depend on the desired wavelength of the laser.
These laser materials can be configured into windows, lenses, output couplers, high reflectors and must be of the highest purity to minimize absorption. To achieve high transmission, a wavelength optimized anti-reflection coating is added.
Optical cavity is an arrangement of mirrors that forms a standing wave cavity resonator for light waves. The optical cavity is the major component of lasers. One mirror is coated with a high reflective coating (99% or 99.5% R) and the second mirror is a partial reflector for outputting the laser energy.
Both substrates must be free of defects, have minimal absorption and have a high laser damage threshold coating. The substrates can be flat or curved and have better than lambda/10 and a surface quality of 10/5 or better.
Output couplers are mirrors that are designed to reflect a percentage of the laser beam back into the resonator for continuous amplification while transmitting some energy out of the laser cavity. ZnSe substrate material is typically used for 10.6 that include a partial reflective coating on the inside and AR coating on outside of the substrate. The partial reflective coatings have very low absorption and can range from a reflection of 50% to 95%.
Optical power limiters (OPLs) are essential for protecting sensitive electronic or photonic sensors and detectors from damage due to abnormally high radiation exposure, accidental or attacked. The optic limits the amount of power transmitted through the optical component even as the input power continues to increase. In comparison to notch filters, designed to always block out a single laser wavelength, OPLs are broadband and respond to the power intensity of the incoming attack, at any wavelength in the response band. Most detectors can accept an attack to a certain power level without damage or without affecting performance. Hence, OPLs have a broad appeal over complex single or multi-notch filter solutions.
With innovative thin film design and precision deposition process control, Reynard has produced a variety of very high reflection coatings. High reflection coatings can be implemented across any wavelength band from the UV to the Far IR. Narrow band designs typically perform better than wide-band, and can be tuned for an optimal performance band, or a single laser line.
Reynard’s high-reflection (HR) coatings have been validated to achieve over 99.9% reflection. Measurement of these high reflectors becomes very difficult at higher performance values, as they are typically comparisons against a known reflective standard, such as an unprotected gold or silver reflector. Known standards can degrade over time due to oxidation, environmental changes, or even handling, among other possibilities, changing the reflective performance. This degradation of the standard affects the validity of all future product measurements. For that reasons, an indirect measurement can also be used. For example, Reynard has measured transmission through a reflective device to be less than 0.1%, indicating a better than 99.9% reflection value. However, this indirect measurement does not account for material absorption or surface scattering, which can affect the true reflection value. Careful substrate design and coating material specification can help to minimize these concerns. High reflection coatings are used in applications such as reflecting telescopes, such as in a Cassegrain design, galvo mirrors, and space applications.
Reynard Corporation offers a wide range of CO2 laser optics (9.4 - 10.6 micron), including focusing optics, beamsplitters, turning mirrors and debris shields. Low-loss, high damage-threshold optics ensure long lifetime and superb performance. Our optics can serve as OEM replacements, or we can help you with your custom application.