How to Prevent Secondary Pollution of Laser Lenses?

In general laser output devices, most of the lenses would absorb specific laser wavelengths due to manufacturing processes or external contamination, shortening their lifetimes. The damage of laser lenses can cause impact on usage or even shutdown.

Increased absorption of laser wavelengths by lenses can cause uneven heating and changes in reflectivity and refractive index, resulting in uneven distribution of power when the laser passes through or reflects off highly absorbing lenses. This can cause the center of the lens to be hot and the edges to be cold, a phenomenon known as thermal lensing effect in optics.

Problems caused by thermal lensing effect due to high absorption of laser lenses caused by contamination

The generation of irreversible thermal stress in the lens substrate, power loss when the beam passes through laser lens, offset of the focus position, and premature damage of the coating layer can cause lens damage. When cleaning lenses exposed to the air, we often do not follow the requirements and precautions for lens cleaning, and use improper materials, which can result in new contamination or even scratch the lens, causing irreparable damage.

Cleaning of laser lenses is very important

Based on years of experience, keeping optical laser lenses free of contaminants is the most critical. Careful cleaning of lenses with good cleaning habits can reduce or eliminate contamination caused by human factors, such as fingerprints or saliva droplets. As a rule of thumb, when working with an optical system, finger cots or medical gloves should always be worn during cleaning, disassembly, and installation. The requirements and precautions for lens cleaning must always be followed, and only specified materials such as optical lens cloths and medical-grade ethanol should be used during the cleaning process.

Taking shortcuts in cleaning, disassembly, or installation of any lens will result in shorter lifespan and even permanent damage. When it is determined that a lens is contaminated, it is best to use an ear syringe to blow the lens until there are no particles on the surface. Do not blow with your mouth because the air expelled from the mouth usually contains oil and water, which will further contaminate the lens. If there are still contaminants on the surface after the ear syringe treatment, we must use a special cotton swab dipped in a mixture of acetone and ether to gently wipe them off, in order to remove most of the pollutants. Contamination of laser mirrors or laser lenses in a laser system can seriously affect the laser output power, even causing serious errors in the data acquisition system. If we can keep the lenses clean regularly, it will undoubtedly extend the lifespan of the entire machine.