*2.4. Spectral-Domain Optical Coherence Tomography (Sd-OCT)*

Cross-sectional analysis was performed with a commercial OCT device, Thorlabs Telesto-II, using a superluminescent diode (central wavelength: 1300 nm, bandwidth: about 100 nm) with axial resolution of 5.5 μm in air, and lateral resolution of 13 μm. The maximum field of view (FOV) is 10.0 × 10.0 mm2, with 3.5 mm imaging depth. The detector consists of a spectrograph made of a diffraction grating and a fast camera. The system is controlled via a 64-bit software preinstalled on a high-performance computer. The 3D scanning path probe with integrated video camera performs high-speed imaging (76 kHz) for rapid volume acquisition and live display. The sample stage provides XY translation and rotation of the sample along with axial travel of the probe.
