How to overcome the challenges of UV optics used in industrial lasers
Jan. 14, 2022
Engineering and manufacturing have become dependent on the many advantages offered by industrial lasers. Improvements in quality, accuracy, cost and energy efficiency have led to significant advances in manufacturing production and control processes, resulting in a sea change in quality and safety.
Clean, precise processes that provide superior quality results; uninterrupted consistency and no damage to surrounding materials are all characteristics associated with lasers that have dramatically changed the field of manufacturing.
For this reason, lasers have widely replaced traditional production methods, and we now see cutting, drilling and welding processes handled primarily by laser instruments. Many industries now rely heavily on excimer and lasers.
Common Industrial Laser Applications
Solid-state lasers operate at high power and are used to etch, mark and engrave a range of materials. The automotive industry is a heavy user of this type of laser because it is so efficient at cutting and welding steel. Pulsed Nd:YAG lasers are commonly used for drilling high-temperature alloys such as those used to produce gas turbine parts. In addition, these lasers are used in aerospace applications for drilling cooling holes to improve heat dissipation and airflow efficiency, and for a process called laser blasting; a flash laser system that produces very high power on the surface of a part without generating heat or adding material. Laser blasting is widely used in aerospace and power generation for gas turbine engines.
Excimer lasers, also known as excimer lasers, are gas-driven UV lasers that are widely used in the production of semiconductor integrated circuits (chips) through photolithography, micromachining and microelectronics. These lasers are considered to be the most powerful in the UV region.
A very important consideration ......
Indeed, lasers have enabled and automated processes that were previously impossible, or at least very dangerous. Extreme environments, challenging access standards and complex processes offer little or no competition for industrial laser applications that offer superior power and capability.
Of course, power and capability place very high demands on the components of a laser application. Therefore, if laser applications are to be delivered under demanding conditions, one important condition must be met: their optical components must be able to deliver at the highest possible performance.
The challenges of UV optics
Optical components used in modern laser systems and applications need to withstand exceptionally high fluxes of short wavelength radiation, including billions of intense laser pulses, without causing damage. They also need to be chemically resistant; have excellent heat resistance and be very robust.
For example, laser blasting typically uses very high energy levels of 10 to 40 joules and pulses of 10-30 nanoseconds to produce several gigawatts of power.
For industrial strength, high-power grade optical components are essential. Windows, lenses, mirrors and other optical components must be able to perform at peak performance. However, there are challenges to overcome to achieve this goal.
With industrial laser optics, there is no room to deviate from specifications. Surface tolerances are tighter, and applying coatings with precise accuracy can be challenging. Defects in the optics used in UV applications are magnified, which means a higher probability of multiphoton absorption, a problem that can damage the optics.
Overcoming UV optics challenges
To ensure the high performance and longevity of UV optics, various factors must be considered.
Advanced fused silica is one of the most stable substrates and is widely used in UV laser components such as high-power grade ND:YAG laser mirrors and high-energy grade excimer laser mirrors, as well as aspheric windows. The benefit of using fused silica is that it provides very high surface quality and high surface accuracy, which means that the components can withstand excessive damage thresholds.
Sapphire is another material that is widely used in UV applications. Sapphire components such as sapphire windows are very robust because the material is second only to diamond in hardness, can withstand temperatures up to 2030 degrees Celsius, and is resistant to almost all chemicals and abrasion.
Applying anti-reflective coatings to both surfaces of UV laser components reduces surface loss to almost zero for the most efficient transmission. Anti-reflective coatings have extremely high damage thresholds and can increase durability.
For example, precision front surface mirrors are used in a range of demanding manufacturing control applications. Reflective mirrors are coated to optimize the specific spectral region in which they are used. As coatings, enhanced aluminum protects the optics, while enhanced dielectric coatings improve durability, ease of handling and prevent oxidation. The outer coating can be further customized to improve the reflectivity of the metal coating. Customizations such as these make precision front surface mirrors ideal for a variety of laser and other manufacturing applications.
The diameter of the optical lens used in UV applications is an important consideration for two reasons. First, higher power lasers require a larger lens diameter to avoid thermal overload. Second, if the incident beam expands to fill a larger lens size, the larger diameter will produce a more concentrated focal spot at any given focal length.
Most Nd:YAG laser applications tend to use biconvex lenses. They have convex curves on both the incident and exit surfaces and are designed to produce an optimal focus point, which is usually smaller than what can be achieved with a plano-convex lens. If achieving the smallest spot size is not a critical consideration, then a plano-convex lens is usually a more cost-effective option.
Customization of UV optical components, such as edge or square or rectangular hole design, fire polishing, diamond turning or thermal toughening, can prepare them for a range of manufacturing and engineering environments and applications.
The key consideration is that customization should meet specific requirements and challenges. It is critical to work with an optical industry consultant to determine a fully customized precision solution.
Meticulous measurement and testing of optical components is absolutely critical. Through expert metrology, precisely conform to the specifications that have been determined to be critical to your UV application optics. The combination of the best, top-of-the-line, state-of-the-art metrology instruments, best-in-class industry expertise, and a thorough understanding of the specific needs, goals, and challenges of optical applications will ensure superior quality and compliance.
Optical Component Experts for UV Laser Applications
CLZ has always focused on the custom design of precision optical components. Our technical expertise covers all aspects of custom optical component design and manufacturing.
Our state-of-the-art metrology instruments are the best in the industry and are designed to take optical testing to a new level with equipment capable of measuring the most complex materials and precision optical surfaces. In addition, our metrology experts are able to share a wealth of in-depth knowledge.
If you would like to discuss your individual optical component requirements for any industrial laser application, our experienced multilingual sales team and industry-trained technical experts are at your disposal.
Laser technology has become a groundbreaking and efficient production process, which is why there is a continuous demand for the most precise optical components. We welcome you to get in touch with us.