Experimental investigation of wavelength dependence of penetration depth and imaging contrast for ultrahigh-resolution optical coherence tomography

Optical coherence tomography (OCT) is a non invasive optical imaging technology for micron-scale cross-sectional imaging of biological tissue and materials. Although OCT has many advantages in medical equipments, low penetration depth is a serious limitation for other applications. To realize the ultrahigh resolution and the high penetration depth at the same time, it is effective to choose the proper wavelength to maximize the light penetration and enhance the image contrast at deeper depths. Recently, we have demonstrated ultrahigh resolution and high penetration depth OCT by use of all-fiber based Gaussian shaped supercontinuum source at 1.7 mu m center wavelength. Gaussian-like supercontinuum with 360 nm bandwidth at center wavelength of 1.7 mu m was generated by ultrashort pulse Er doped fiber laser based system. In this paper, using 0.8 mu m and 1.3 mu m SC sources in addition to the 1.7 mu m SC source, we have investigated the wavelength dependence of ultrahigh resolution OCT in terms of penetration depth. Longitudinal resolutions at each wavelength region are almost 4.6 mu m in air. The obtained sensitivity was 95 dB for all wavelength regions. We confirmed the difference of imaging contrast and penetration depth with hamster's cheek pouch and so on. As the wavelength was increased, the magnitude of penetration depth was increased for these samples.