Tunable external cavity laser diode based on wavelength controlled self-assembled InAs quantum dots for swept-source optical coherence tomography applications at 1100 nm wavelength band

We fabricated and characterized a grating-coupled external cavity laser with gain chips including self-assembled InAs quantum dots (QDs) for swept-source optical coherence tomography applications. By controlling the emission wavelength of the self-assembled InAs QDs, tunable lasing at a wavelength band of 1-1.1 mu m was obtained, which represents an optimal balance between absorption and scattering in biological tissues. Straight and J-shaped edge-emitting ridge waveguides (RWGs) were fabricated on a GaAs-based waveguide layer containing four InAs QDs layers. A diffraction grating with the quasi-Littrow configuration was employed as an external cavity for the fiber-coupled diodes. Electroluminescence spectra from the QD-based diodes revealed that broadband amplified spontaneous emissions appeared in a J-shaped RWG, whereas Fabry-Perot lasing occurred in the straight RWG. The external cavity was then introduced for the diode with a J-shaped RWG, and a tuning range of 65 nm centered at approximately 1100 nm was obtained from the QD gain chip with the J-shaped RWG.