Multi-spectral bands optical coherence tomography assisted by ultrawide band photonic crystal fiber splitter

We report fabrication and performance of the 2×2 photonic crystal fiber (PCF) splitter that enables multi-spectral bands operation of an optical coherence tomography (OCT) system. The PCF splitter was made by coupling PCFs to a planar lightwave circuit (PLC) splitter chip, which worked as a single mode splitter from visible to near infrared wavelengths. The core size of the PLC splitter chip was about 3 μm×3 μm and the core-cladding index difference was about 0.25%, which gave the cutoff wavelength at 630 nm. The implemented PCF-PLC splitter showed a small excess loss of 1.2∼3.3 dB and a low polarization-dependent loss of 0.15∼0.19 dB over a wide wavelength range from 640 nm to 1000 nm. With the splitter, OCT images of a human finger and a nail have been successfully obtained at several spectral bands; 680 nm, 840 nm, and 930 nm center wavelengths.