Superluminescent diodes for optical coherence tomography

We summarize the results of development of superluminescent diodes (SLEDs) for OCT applications. It is shown that powerful, wide spectrum and low rippled SLEDs may be realized at different spectral bands from 800 nm to 1600 rim on the base of relatively simple bent-angled SLED structure with double-layer protective/antireflective(AR) coatings on both facets of SLED crystal. Up to 100 mW free space and 30 mW SM fiber coupled outputs are realized at 820 and 980 nm bands, and 15-35 mW free space (5-15 mW SM fiber) at 1550 nm and 1300 nm bands. Various methods to widen SLED spectrum are presented. 50 nm of gaussian-like spectrum is obtained from 1040 nm SLD. 70 nm FWHM and 20 mW free space output power is realized at 940 nm by using two-electrode pumping of strained QW SLED. 70 tun FWHM is obtained from 1550 nm band MQW SLED with 5 mW output power, All SLDs are characterized by very low parasitic Fabry-Perot modulation. Example of SLED use in commercial OCT setup is presented.