CO2 Laser Optics at the Forefront: Pushing Boundaries with CO2 Laser Lenses and CO2 Laser Mirrors

Author: Bryan Ng – Marketing Manager

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Carbon dioxide (CO2) lasers have become a cornerstone technology in numerous industries, including laser processing, medicine, and research. These lasers emit a beam of infrared light with a wavelength of 9.6 or 10.6 µm, enabling them to interact with a wide range of materials. However, the successful utilization of CO2 lasers heavily relies on high-quality CO2 laser optics.

1. The Importance of CO2 Laser Optics in CO2 Laser Systems

CO2 Laser Optics at the Forefront. Pushing Boundaries with CO2 Laser Lenses and CO2 Laser Mirrors
Wavelength Opto-Electronic ZnSe Lenses

CO2 laser optics play a vital role in beam delivery, control, and focusing, ultimately influencing the laser’s precision, efficiency, and overall performance. The specific optical components used in a CO2 laser system will depend on the application. For example, a laser cutting system will typically use a focusing lens to focus the beam onto the workpiece, while an engraving system may use a beam expander to widen the beam.

The most common optical materials used in CO2 laser optics are zinc selenide (ZnSe) and germanium (Ge). These materials are transparent to infrared light and have high thermal conductivity, which helps to dissipate the heat generated by the laser beam. The specific optical components used in a CO2 laser will depend on the application.

The quality of the optical components used in a CO2 laser system has a significant impact on the performance of the laser. High-quality optical components will ensure that the laser beam is transmitted and focused accurately, which will result in better cutting, welding, and engraving results.

2. Components of CO2 Laser Optics

CO2 laser optics encompass a diverse range of components that facilitate the manipulation and control of the laser beam. The primary components include CO2 laser mirrors, lenses, windows, beam splitters, and attenuators, each playing a crucial role in optimizing the laser’s characteristics.

2.1 CO2 Laser Mirrors

CO2 Laser Optics CO2 Laser Mirrors
Wavelength Opto-Electronic CO2 Laser Mirrors

CO2 laser mirrors are integral to the beam delivery and control in a CO2 laser system. They are responsible for reflecting the laser beam and maintaining its alignment. Reflective CO2 laser mirrors must have low reflection losses, high optical quality, and good resistance against extreme optical intensity.

Product TypePart NumberWavelength (nm)MaterialDia (mm)ET (mm)
Reflective MirrorRSI-0.75-310600Silicon19.13.0
Reflective MirrorRSI-1-310600Silicon25.43.0
Reflective MirrorRSI-1.1-310600Silicon27.93.0
Reflective MirrorRSI-1.5-410600Silicon38.14.0
Reflective MirrorRSI-2-510600Silicon50.85.1
Reflective MirrorRSI-2-9.510600Silicon50.89.5
Reflective MirrorRMO-0.75-3Polished SurfaceMolybdenum19.03.0
Reflective MirrorRMO-1-3Polished SurfaceMolybdenum25.43.0
Wavelength Opto-Electronic CO2 Laser Mirrors Table

CO2 laser cavity optics consist of a rear mirror and a front mirror (also called an output coupler or partial reflector ). Rear mirrors, typically ZnSe, with very high reflectivity (>99.7%) are key optical components in laser resonators. Output couplers are partially reflective mirrors to extract a portion of the laser beam from the laser resonator. They often require a slight wedge to prevent interference from multiple reflections inside the component. High-quality CO2 laser mirrors minimize losses and ensure efficient beam delivery.

Product TypePart NumberWavelength (nm)MaterialDia (mm)ET (mm)RadiusReflectivity (%)
Rear MirrorRSI-1-4.5-3MCC10600ZnSe25.44.53M Concave>99.7%
Rear MirrorRSI-1-4.5-5MCC10600ZnSe25.44.55M Concave>99.7%
Output CouplerOCZ-0.5-2-80%R10600ZnSe12.72.0Plano80+/-3%
Output CouplerOCZ-0.5-3-92%R10600ZnSe12.73.0Plano92+/-3%
Output CouplerOCZ-0.75-2-70%R10600ZnSe19.12.0Plano70+/-3%
Output CouplerOCZ-0.75-3-85%R10600ZnSe19.13.0Plano85+/-3%
Output CouplerOCZ-0.75-2-95%R-5MCC10600ZnSe19.12.05M Concave95+/-3%
Output CouplerOCZ-20-85%R-3MCC10600ZnSe20.03.53M Concave85+/-3%
Output CouplerOCZ-25-3-70%R10600ZnSe25.03.0Plano70+/-3%
Output CouplerOCZ-25-3-95%R10600ZnSe25.03.0Plano95+/-3%
Output CouplerOCZ-1-3-80%R10600ZnSe25.43.0Plano80+/-3%
Output CouplerOCZ-1-3-85%R10600ZnSe25.43.0Plano85+/-3%
Wavelength Opto-Electronic Cavity Optics Table

2.2 CO2 Laser Lenses

CO2 laser lenses are employed to shape and focus the laser beam. They’re typically made ZnSe material and can be either convex or concave, where their focal length determines the beam’s focus point. Plano-convex lenses have a positive focal length and are used to focus a collimated beam to a small spot size. Plano-concave lenses have a negative focal length and are used for diverging collimated beams. The curved surfaces of these lenses should face the source to minimize spherical aberration.

Positive meniscus convex-concave lenses are converging lenses being thick at the center and thin at the edges and producing real images. The radius of the curvature of the concave side is greater than the convex side of the lens. The convex side of the lens should face the source to minimize spherical aberration. It is designed to minimize spherical aberration and produce minimum focal spot size for incoming collimated light. CO2 laser lenses are essential for applications such as cutting, engraving, and welding, where precise control of the beam’s shape and intensity is crucial.

2.2.1 ZnSe Aspheric Lenses

CO2 laser lenses also come in other shapes such as aspheric, spherical, cylindrical, and axicon. Compared to conventional ZnSe spherical lenses, the most significant advantage of ZnSe aspherical lenses is that they can perform spherical aberration correction. Aspheric lenses allow the designer to correct the aberration with fewer optical lenses than spherical lenses, so the optical system can be lower cost and more compact in size.

Part NumberEFL (mm)Dia (mm)Material
LZSE-25.4-12.712.725.4Zinc Selenide
LZSE-25.4-25.425.425.4Zinc Selenide
LZSE-25.4-50.850.825.4Zinc Selenide
Wavelength Opto-Electronic ZnSe Aspheric Lenses Table

2.2.2 ZnSe Cylindrical Lenses

Cylindrical Lenses Diagram 1
ZnSe Cylindrical Lenses Diagram
Cylindrical Lenses Diagram 2
ZnSe Cylindrical Lenses Diagram

ZnSe cylindrical lenses are used to focus an incoming beam in a single focal line than at a single focal point, it comes with both positive and negative focal lengths. They are either round or rectangular objects with cylindrically shaped surfaces, either in plano-concave or plano-convex. They differ from spherical lenses in that they focus a beam on a focal line rather than a focal point.

Part No.MaterialWavelength (nm)Dimension (mm)EFL (mm)CT (mm)Type
LZCY-25.4×25.4-25ZnSe10600/940025.4 x 25.425.45.0Plano-Convex
LZCY-25.4×25.4-38ZnSe10600/940025.4 x 25.438.15.0Plano-Convex
LZCY-25.4×25.4-50ZnSe10600/940025.4 x 25.450.85.0Plano-Convex
LZCY-25.4×25.4-63ZnSe10600/940025.4 x 25.463.55.0Plano-Convex
LZCY-25.4×25.4-76ZnSe10600/940025.4 x 25.476.23.8Plano-Convex
LZCY-25.4×25.4-101ZnSe10600/940025.4 x 25.4101.65.0Plano-Convex
LZCY-25.4×25.4-127ZnSe10600/940025.4 x 25.4127.05.0Plano-Convex
LZCY-25.4×25.4-190ZnSe10600/940025.4 x 25.4190.55.0Plano-Convex
LZCY-25.4×25.4-254ZnSe10600/940025.4 x 25.4254.05.0Plano-Convex
LZCY-25.4×25.4-381ZnSe10600/940025.4 x 25.4381.05.0Plano-Convex
LZCY-50.8×50.8-127ZnSe10600/940050.8 x 50.8127.06.5Plano-Convex
LZCY-50.8×50.8-254ZnSe10600/940050.8 x 50.8254.06.5Plano-Convex
LZCY-25.4×25.4+38.1ZnSe10600/940025.4 x 25.4-38.14.0Plano-Concave
LZCY-25.4×25.4+72.4ZnSe10600/940025.4 x 25.4-72.42.5Plano-Concave
LZCY-25.4×25.4+254ZnSe10600/940025.4 x 25.4-254.03.0Plano-Concave
Wavelength Opto-Electronic ZnSe Cylindrical Lenses Table

2.2.3 ZnSe Axicon Lenses

CO2 Laser Optics CO2 Laser Lenses ZnSe Axicon Lens
Wavelength Opto-Electronic ZnSe Axicon Lens

ZnSe axicon focus lenses have one conical surface and are used to produce a ring focus beam. Typically, axicon focus lenses have a second flat surface and are used in combination with a focusing lens. They’re made from a manufacturing process suited to the axicon angle and the accuracy required. For small-angle, high-accuracy lenses, the manufacturing process involves diamond machining.

Product TypePart NumberWavelength (nm)Cone Angle (deg)Dia (mm)MaterialET (mm)Assembly
Axicon LensLZAX-1-ET3-140DEG1060014025.4ZnSe3Single
Axicon LensLZAX-1-ET3-160DEG1060016025.4ZnSe3Single
Axicon LensLZAX-1-ET3-170DEG1060017025.4ZnSe3Single
Axicon LensLZAX-1-ET3-175DEG1060017525.4ZnSe3Single
Axicon LensLZAX-1-ET3-178DEG1060017825.4ZnSe3Single
Axicon LensLZAX-1-ET3-179.5DEG10600179.525.4ZnSe3Single
Wavelength Opto-Electronic ZnSe Axicon Lenses Table

2.2.4 Medical Laser Lenses

There is also another range of CO2 laser lenses used for varieties of medical laser systems such as CO2, Q-switched ND:YAG, ER:YAG, Ruby and Alex Laser systems. These optics have been used as replacements in most well-known medical systems such as Continuum-Biomedical, ESC, Sharplan, Candela, and Coherent.

Product TypePart NumberWavelength (nm)EFL (mm)Dia (mm)ET (mm)MaterialApplications
Medical Laser LensLZ-5.5-9.8-ET1.72E29409.85.51.7ZnSeEr:YAG
Medical Laser LensLZ-7.7-32-ET1.8E2940327.71.8ZnSeEr:YAG
Medical Laser LensLZ-0.5-1.5-ET2E294038.112.72ZnSeEr:YAG
Medical Laser LensLZ-15-36.5-ET2E294036.5152ZnSeEr:YAG
Medical Laser LensLZ-20-47-ET2E294047202ZnSeEr:YAG
Medical Laser LensLZ-20-72-ET3E294072203ZnSeEr:YAG
Medical Laser LensLFS-0.75-400-ET2.5E2940/63340019.12.5ZnSeEr:YAG
Medical Laser LensLFS-0.75-600-ET2.5E2940/63360019.12.5ZnSeEr:YAG
Wavelength Opto-Electronic ZnSe Medical Laser Lenses for Er:YAG Table

2.3 CO2 Laser Windows

CO2 laser windows are typically flat, transparent plates made of materials with excellent optical properties, acting as a protective barrier between the laser system and the external environment. They’re designed to transmit light with minimal distortion, scattering, or absorption. CO2 laser windows are typically made of materials with low absorption at the CO2 laser wavelength, such as ZnSe or Ge.

ZnSe Window Diagram
ZnSe Laser Windows Diagram

ZnSe laser windows are commonly used in high-power CO2 laser systems. They’re available in either coated or uncoated form and come in a wide variety of shapes and sizes. While Ge laser windows isolate different physical environments while allowing light to pass through.

Part NumberWavelength (nm)MaterialDiameter (mm)Thickness (mm)Application
WZB-0.5×1.3-2C(Corner cut)10600/9400ZnSe12.7 x 33.02.0Protective
WZB-0.5×1.3-210600/9400ZnSe12.7 x 33.02.0Protective
WZ-15×18-110600/9400ZnSe15.0 x 18.01.0Protective
WZB-0.6×1.5-210600/9400ZnSe15.2 x 38.12.0Protective
WZB-0.7×1.8-210600/9400ZnSe17.7 x 45.72.0Protective
WZB-0.75×1.5-310600/9400ZnSe19.0 x 38.13.0Protective
WZB-20.3×52.8-310600/9400ZnSe20.3 x 52.83.0Protective
WZB-25×50-310600/9400ZnSe25.0 x 50.03.0Protective
WZB-25×66-310600/9400ZnSe25.0 x 66.03.0Protective
WZB-1.0×2.6-310600/9400ZnSe25.4 x 66.03.0Protective
WZB-26.42×10.16-210600/9400ZnSe26.42 x 10.162.0Protective
WZB-30×75-510600/9400ZnSe30.0 x 75.05.0Protective
WZ-31.75×31.75-410600/9400ZnSe31.7 x 31.74.0Protective
WZB-1.5×3.9-410600/9400ZnSe38.1 x 99.14.0Protective
WZ-50×80-310600/9400ZnSe50.0 x 80.03.0Protective
WZB-2.0×5.2-510600/9400ZnSe50.8 x 132.15.0Protective
WZB-53×20-310600/9400ZnSe53.0 x 20.03.0Protective
WZ-65×85-310600/9400ZnSe65.0 x 85.03.0Protective
WZ-90×60-310600/9400ZnSe90.0 x 60.03.0Protective
WZ-92×68-310600/9400ZnSe92.0 x 68.03.0Protective
WZ-95×95-310600/9400ZnSe95.0 x 95.03.0Protective
WZ-150×105-310600/9400ZnSe150.0 x 105.03.0Protective
WZ-185×125-610600/9400ZnSe185.0 x 125.06.0Protective
Wavelength Opto-Electronic ZnSe Laser Windows Table

2.4 CO2 Dichroic Mirrors

CO2 Dichroic mirrors, typically consisting of beam combiners and beam splitters, are ZnSe filters that selectively transmit a certain wavelength range of light while reflecting another wavelength based on their coating layers’ properties. 

2.4.1 ZnSe Beam Combiners

CO2 Laser Optics CO2 Laser Lenses ZnSe Beam Combiners
Wavelength Opto-Electronic ZnSe Beam Combiner

ZnSe beam combiners merge two or more beams into one and are used for CO2 laser system alignment. They usually transmit a long-wavelength beam and reflect a short-wavelength beam whereas reverse beam combiners transmit a short-wavelength beam and reflect a long-wavelength beam. CO2 beam combiners are designed at a 45° angle of incidence and transmit a laser beam, combining the beam with the 90° reflected visible alignment beam.

Part NumberWavelength (nm)MaterialDimension (mm)Thickness (mm)
BCZ-0.5-310600T / 650RZnSe12.73.0
BCZ-0.75-310600T / 650RZnSe19.13.0
BCZ-20-210600T / 650RZnSe20.02.0
BCZ-1.5-310600T / 650RZnSe38.13.0
BCZ-2-510600T / 650RZnSe50.85.0
Wavelength Opto-Electronic ZnSe Beam Combiners Table

2.4.2 ZnSe Beam Splitters

Unlike beam combiners, ZnSe beam splitters are utilized to divide the laser beam into multiple paths, allowing for simultaneous processing or monitoring. They can also redirect a portion of the beam for alignment or calibration purposes. ZnSe beam splitters are often coated to achieve a specific reflectance or transmission ratio at the CO2 laser wavelength.

Part NumberWavelength (nm)MaterialDimension (mm)Thickness (mm)AOIReflectivity
Wavelength Opto-Electronic ZnSe Beam Splitters Table

The transmission and reflection of the light depend upon various parameters such as the incident angle, state of polarization, and wavelength of the input beam. There is a substantial difference in the transmittance and reflectance values of s and p polarization at a 45° incident angle, so the ZnSe beam splitters designed are for this angle.

2.5 Laser Attenuators

Polarizing Laser Attenuator Diagram
Polarizing Laser Attenuator Diagram
Laser Attenuator Diagram
Polarization Insensitive Laser Attenuator Diagram

Laser attenuators are employed to control the laser power by reducing its intensity. They are useful when fine-tuning the energy delivered to the workpiece, especially in applications where excessive power may cause undesirable effects. Laser attenuators utilize filters or variable mechanisms to achieve the desired power adjustment.

Part No.Wavelength (nm)Clear Aperture (mm)Attenuation RangeOptimizationDimensions (mm)
ATTN-3553552.0-10.05% – 95%Transmission88 x 93.5 x 79
ATTN-5325322.0-10.05% – 95%Transmission88 x 93.5 x 79
ATTN-106410642.0-10.05% – 95%Transmission88 x 93.5 x 79
ATTN-940094002.0-10.05% – 95%Transmission80x 84 x 95
ATTN-10600106002.0-10.05% – 95%Transmission80 x 84 x 95
ATTP-35535514.00.5% – 95%Transmission78 x 87 x 75
ATTP-53253214.00.5% – 95%Transmission78 x 87 x 75
ATTP-1064106414.00.5% – 95%Transmission78 x 87 x 75
Wavelength Opto-Electronic Laser Attenuators Table

3. CO2 Laser Optics Applications

CO2 Laser Optics CO2 Laser Lenses CO2 Laser Mirrors Applications
CO2 Laser Optics Applications

The significance of CO2 laser optics lies in their ability to optimize beam quality, control beam parameters, and enhance overall system performance. High-quality optics ensure minimal losses, reduced beam divergence, and improved focusability, ultimately resulting in increased process efficiency, reduced downtime, and higher-quality output. CO2 laser optics find extensive use in a wide range of applications due to their ability to deliver high-power laser beams with excellent precision. Some notable applications include:

3.1 Material Processing

CO2 lasers are extensively employed for cutting, engraving, marking, and welding various materials, including metals, plastics, wood, and ceramics. High-quality optics ensure accurate focusing, beam shape control, and enhanced process efficiency.

3.2 Medical

CO2 lasers are utilized in surgical procedures, dermatology, and ophthalmology due to their precise tissue ablation capabilities. Optics enable surgeons to deliver highly controlled laser energy for procedures such as skin resurfacing, tumor removal, and eye surgery.

3.3 Scientific Research

CO2 lasers are indispensable tools in scientific research, particularly in fields such as spectroscopy, atmospheric monitoring, and particle acceleration. Optics enable precise beam control, alignment, and manipulation, facilitating accurate data acquisition and analysis.

4. Conclusion

CO2 laser optics are integral components in harnessing the full potential of CO2 laser systems across various industries. Through careful selection and implementation of mirrors, lenses, windows, beam splitters, and attenuators, these optics enable precise control, manipulation, and delivery of high-power laser beams. As technology advances, further advancements in CO2 laser optics are expected, opening up new possibilities for enhanced precision, efficiency, and innovation in diverse applications.

Overall, CO2 laser optics are a critical component of CO2 lasers. They play a vital role in the transmission and focusing of the laser beam, which ultimately determines the performance of the laser. With proper care and maintenance, CO2 laser optics can provide years of reliable service. Wavelength Opto-Electronic design and manufacture various CO2 laser optics like CO2 laser lenses and CO2 laser mirrors for your CO2 laser systems.

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What is a CO2 laser?

A CO2 laser (carbon dioxide laser) is a type of gas laser that uses carbon dioxide gas as the active medium to produce a highly concentrated beam of light at the infrared wavelength.

What is a CO2 laser used for?

CO2 laser optics find extensive use in a wide range of applications due to their ability to deliver high-power laser beams with excellent precision. Some notable applications include industrial material processing, medical treatment, and scientific research.

What wavelengths are in a CO2 laser?

A CO2 laser emits light primarily at a wavelength of 10.6 μm, which corresponds to the far-infrared region of the electromagnetic spectrum. CO2 lasers can also emit some secondary wavelengths in the near-infrared region. These secondary wavelengths are typically at 9.4 μm and 9.6 μm.

What lens is best for CO2 laser cutting?

Focusing lenses are used for cutting with a CO2 laser. The most suitable type of lens for cutting with a CO2 laser depends on several factors, including the laser’s power, the material being cut, and the desired cutting depth and speed. There are two common types of focusing lenses used in CO2 laser cutting machines, they’re plano-convex and meniscus lenses.

What is the focal length of a CO2 laser lens?

The most common focal lengths for CO2 laser lenses are in the range of 1.5 inches (38.1 mm) to 5 inches (127 mm). Here are some common focal lengths and their typical applications:

Short Focal Length (e.g., 1.5 inches): Short focal length lenses produce a small and highly focused spot, making them suitable for cutting thin materials with high precision. They are ideal for intricate designs and fine details.

Medium Focal Length (e.g., 2.5 inches to 3.5 inches): Lenses with medium focal lengths offer a good balance between cutting speed and edge quality. They are versatile and commonly used for a wide range of applications on materials of various thicknesses.

Long Focal Length (e.g., 5 inches): Long focal length lenses provide a larger depth of field, making them suitable for cutting thicker materials and applications where cutting speed is more critical than fine detail.

What are the different types of CO2 laser lenses?

Different types of CO2 laser lenses include plano-convex, plano-concave, meniscus, aspherical, spherical, cylindrical, and axicon.

What type of mirror is best for CO2 laser?

The two primary types of mirrors used in CO2 lasers are copper mirrors and silicon mirrors (silicon-plated mirrors).

What are CO2 laser mirrors made of?

CO2 laser mirrors are typically made of copper and silicon.

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