Photonic Sourcing

Knight Optical have supplied many markets with interference bandpass filters over many years. These include Defence & Aerospace, Oil & Gas, Opto-Electronic and Medical & Biotech, to name just a few.

Our filters are used in many applications, from optical sensor systems in military hardware to automatic number plate recognition systems.
They are also widely used in research and development, particularly in the Medical and Biotech industries, where the isolation and blocking of wavelengths is required for medical analyser spectroscopy instruments and precision farming systems. Oil & Gas industries utilise our interference bandpass filters for spectroscopic analysers and to isolate infrared wavelengths for imaging systems.

Interference bandpass filters allow the transmission of a wavelength or various wavelengths whilst blocking those not required. As their name suggest, interference bandpass filters depend on the destructive interference at certain wavelengths of light.
A beam of light travels through two reflecting surfaces and wavelengths destructively interfere or are passed through the filter, depending on the distance between the reflective layers.
A dielectric spacer is placed between these reflecting surfaces whose thickness depends on the desired wavelength permitted through the filter.

This “stack” of layers form the workings of the interference bandpass filter. Knight Optical’s filters are then CNC scribed and hermetically sealed in nested rigs. This acts to make the filter more durable and increases the life of a filter dramatically, particularly when used in a system requiring filter changeover or regular position adjustment.   Knight Optical’s optical filters offer steep tranmission cut-off slopes and high levels of band blocking, as well as uniform and high band pass transmission.  

We are happy to quote for custom requirements of size and specifications with the following ranges:

Size: 1 - 250mm

Thickness: 0.2 - 40mm

Surface Quality: Fine Ground - 10/5 and flatness suitable for epitaxial film growth.

Flatness: Up to λ/4 We offer C-plane, M-plane, R-plane and random orientations.

Filters can be supplied unmounted, or mounted in black anodized aluminium rings for increased durability. Sapphire's high refractive index means it reflects more light than glass of fused silica windows. For this reason anti-reflection coatings are recommended.

Contact our technical sales team to find out more about our custom filter capabilities or to send your bespoke and custom specification drawings.