BAADER APO 95/580 CaF2 SWIR – LaserCOM Refractor

The BAADER APO 95/580 CaF2 SWIR – LaserCOM Refractor is the application-optimized SWIR/LaserCOM version of our compact 95 mm fluorite apochromat. It was developed for optical communication, measurement and SWIR applications where not only high transmission, but also precise point imaging at the actual laser wavelengths used is essential.

SWIR stands for Short-Wave Infrared and describes the spectral range beyond visible light, which is used in numerous communication, measurement and sensor technologies.

Commercially available refractors are generally optimized for the visible spectral range. For applications beyond the visible range – especially at 850 nm and 1550 nm – good visual color correction alone is not sufficient. Focal position, point imaging and transmission characteristics must be matched to the operating wavelength. This is exactly what this SWIR version of the BAADER APO 95/580 was designed for.

The optical system is based on an oil-spaced triplet design with a genuine calcium fluoride center element. This design combines the high optical quality of a true CaF₂ apochromat with a coating optimized for LaserCOM and SWIR applications. As a result, the refractor is especially suitable for applications where laser power, received signals or image information must be delivered to the focal plane as efficiently and precisely as possible.

The dedicated SWIR/LaserCOM coating is designed for high transmission in the typical operating ranges of optical communication and measurement systems. The following wavelengths were given particular consideration:

• 685 nm
• 850 nm
• 1550 nm

The optical transmission data sheet specifies very low reflection of R < 0,3 % in these ranges. This makes the refractor particularly suitable for applications where the highest possible light throughput must be available at the focal plane – for example when coupling light into sensors, receiver optics or other optical assemblies.

The wavelength around 1550 nm is particularly important for Free-Space Optical Communication, ground-to-satellite communication and optical space communication. At the same time, systems operating at 685 nm or 850 nm can also benefit from the specially optimized coating and the very high point imaging quality.

The oil-spaced design is a key element of the optical concept. In an air-spaced triplet, light has to pass through several glass-to-air transitions. Each of these transitions causes reflection losses and can generate stray light. An oil-spaced triplet, by contrast, behaves optically much like a compact glass block. For the light path, essentially only the entrance and exit surfaces of the objective remain relevant.

This is a particular advantage for LaserCOM and SWIR applications, where every percentage point of transmission counts. In addition, the oil-spaced design supports high thermal stability, rapid temperature equalization and robust alignment stability of the lens assembly.

More about oil spacing in fluorite apochromats: Why an oil-spaced CaF₂ triplet offers advantages in transmission, thermal behavior and long-term stability..

The BAADER APO 95/580 CaF2 LaserCOM/SWIR is designed as a compact, serially produced COTS optic. COTS stands for Commercial off-the-shelf and describes a commercially available solution that can be integrated into professional systems without the need for a complete custom optical design.

The combination of an oil-spaced CaF₂ triplet, LaserCOM-optimized coating and corrected point imaging up to 1550 nm makes this refractor an exceptionally sensitive optical platform for industrial, scientific and institutional applications.

Typical fields of application include:

• Free-Space Optical (FSO) Communication
• Building-to-building data links
• Ground-to-satellite communication and optical ground stations / Optical Ground Stations (OGS)
• Satellite communication
• Quantum Key Distribution (QKD) and quantum communication setups
• SWIR imaging and narrowband measurement applications
• Laboratory, test and demonstrator systems for optical data transmission

The SWIR APO is not only available as a standalone optic, but also as a project-specific configured system on request. Depending on the application, the refractor can be equipped with additional components for focusing, adaptation, filtering and optical-axis alignment.

Possible configurations include:

• motorized focusing, e.g. for precise focus positioning in camera or laser applications
• C-Mount or project-specific camera adaptation
• mechanical adaptation for laser, sensor or receiver modules
• filter holders for attenuation filters and narrowband filters
• iris diaphragm for aperture limitation
• repeatable alignment of the optical axis to the main instrument
• integration of multiple cameras or optical assemblies at the focal plane
• project-specific switching via physical optical switches

This allows the BAADER APO 95/580 CaF2 SWIR to be used as a compact optical platform for a wide range of LaserCOM and SWIR setups – from laboratory systems to application-oriented demonstrators.

Some application examples. Please contact us regarding your desired configuration.