Modelling and excitation of a thermo-optical delay line for Optical Coherence Tomography

This paper presents the modelling and excitation of a non-mechanical rapid scanning delay line for Optical Coherence Tomography (OCT). The optical delay line exploits the thermo optic effect of silicon by applying electrical power to a silicon membrane, affecting its temperature and therefore the refractive index. Based on a nonlinear model of the device, voltage excitation waveforms can be generated that compensate for the nonlinearities inherent to the device. The bandwidth of the device can be extended significantly by pre-emphasis of the higher frequencies of the voltage excitation. Line scanning rates up to 10 kHz with a good linearity are presented. The residual non-linearity results in an inaccuracy less than 5μm with a system resolution of 15μm.