Broadly tuneable, short external cavity diode laser for optical coherence tomography

The application of a broadly tuneable asymmetric multiple-quantum-well (AMQW) laser is demonstrated in an external cavity for both time-domain and Fourier-domain optical coherence tomography (OCT). The AMQW laser was custom designed and fabricated to have a large tuning range when operated with no facet coatings in a diffractive optical element (DOE) short external cavity (SXC). The depth resolution of Fourier domain OCT was found to be as short as 13 mum in air with the 117 nm tuning range (full-width-half-maximum of 80 nm) of the AMQW DOE SXC source. For time domain OCT, synthesised OCT with the AMQW sources was investigated. It was found that the depth resolution is set by the tuning range of the AMQW DOE SXC laser. The depth resolution can be improved as 117 nm is not the limit to the tuning range of AMQW lasers.