The supercontinuum source we are working with are commercial products from NKT Photonics and have the great feature of covering a large spectral bandwidth. These sources cover from the visible light up to the infrared wavelengths, to be precise from around 450 nm to 2400 nm. Because of this broad bandwidth we can use different wavelengths for optical coherence tomography (OCT). Optical coherence tomography works comparable to ultrasound or radar, where the light (or sound) is split into a reference and a sample. If the light (or sound) travel a different length interference occurs based on the path length difference. This interference is measured and the depth information can be reconstructed. The benefit of OCT is that by using a larger bandwidth the accuracy with depth can be improved.
Classical OCT light sources, such as superluminescent diodes (SLD) or swept source laser are mainly centred at 800 nm or 1300 nm and cover around 50 to 100 nm bandwidth. Here the supercontinuum has a large advantage.
We have implemented an OCT system at NKT at 800 nm with a spectral bandwidth of 300 nm. The bandwidth was limited by the detector of the set-up and not the source. Another set-up we built was for visible light covering from 465 to 730 nm. A third system was built centred at 1300 nm and a bandwidth of 400 nm. All these systems were functional and are used for further investigations.
Written by: Felix FLEISCHHAUER