As light sources, digital sensors, and coating chamber technologies continue to improve, optical filters will naturally evolve and continue to advance. Optical filters are critical for some of the most demanding applications in automation, energy, medical imaging, security, and multi-element optical systems.

These advancements require developments on new substrates such as flexible thin film polymers and IR grade materials including silicon and germanium, or with new chemicals and compounds that yield high transmission and high blocking filters in the UV and IR spectrums. Advancements in coating chamber technology have resulted in higher precision filters yielding bandwidths of <1nm with tolerances of <1%, which truly pushes the limits of top of the line spectrophotometers. With each advancement, tolerances and specifications have been further optimized to better represent a precision substrate with improved surface quality, surface flatness, parallelism, and transmitted wavefront.

New materials, sub-nanometer specifications, deep UV to far IR spectral coverage, and various improved tolerances will continue the advancement of optics and photonics in nearly every consumer and scientific application.

• Ultra-Narrow
   
• Broadening Spectral Range
   
• Thin, Flexible
   
• Tighter Tolerances and Specs
   

Ultra-Narrow Designs

For many years, laser line filters have featured bandwidths as narrow as 1.5 – 2nm, but with new advancements in coating technology and metrology, laser line filters can now achieve bandwidths of <1nm across the visible spectrum. This precision will greatly benefit single photon, Raman, and other imaging applications that detect very subtle and weak signals.

Figure 1 (left): Transmission plots for 355nm and 533nm Ultra-Narrow Bandpass Filters

Broadening Spectral Range

Hard coated filters are primarily used to focus on the Visible and NIR spectral regions from around 400 – 1800nm. Recent advancements and technological developments in coating and material design have broadened this range into the UV and IR regions as low as 250nm and as high as 7300nm.

Figure 2 (left): Transmission plot for the 7.30µm, 25mm Diameter, Infrared Longpass Filter (#68-656)

Thin, Flexible Materials

Ultra-thin, flexible filters are achieved using a unique extrusion process and feature a polymeric material design with thicknesses as small as 200µm. These filters are also scratch insensitive and flexible, allowing for unmet integration into some of the most complex form factors and compact optical systems.

Figure 3 (left): Structure of All-Polymer Flexible Filters

Tighter Tolerances and Specifications

Sputtering platforms used to coat filters involve hazardous temperatures, pressures, and particles moving at very high speeds. Ensuring a clean, pristine, and flat filter surface can therefore prove very challenging. Surface specifications such as parallelism, surface quality, surface flatness, transmitted wavefront, and power or irregularity typically suffer in traditional magnetron and ion-beam sputtering platforms; advancements in these techniques will lead to filters with tighter surface tolerances.

Figure 4 (right): Edmund Optics Sputtering Platform Used to Coat Optical Filters