January 28th, 2018
A 16 MHz frequency-comb stretched-pulse mode-locked (SPML) laser using a continuously chirped fiber Bragg grating for subsampled OCT
Session 6: OCT New Technology I
Tuesday 30 January 2018
10:30 AM - 12:00 PM
In this work we demonstrate circular ranging by using a frequency comb source to subsample an extended depth field into a reduced measurement space. As a result, imaging at significant higher voxel rates and reduced data load become possible. Using a continuously chirped fiber Bragg grating we present an improved cavity layout compared to a previously reported laser design. Wavelength-stepping is demonstrated in a stretched-pulse active mode locking architecture using a single continuously chirped fiber Bragg grating, achieving a repetition rate of 16 MHz and a coherence length of 5 cm.
Definitive depolarization contrast for optical frequency domain imaging
Session 10: Polarization
Wednesday 31 January
10:30 AM - 12:00 PM
Depolarization of light provides intrinsic contrast for tissue heterogeneity. Different metrics have been used to characterize depolarization such as cross-polarization, degree-of-polarization (uniformity), (differential) depolarization index and entropy. Due to its complexity, the origin of depolarization can be manifold, making the current characterization of depolarization ambiguous and/or incomplete. In this work, we start with a general form of a mixed state to derive depolarization from the eigenvalues of a density matrix that describes polarization entropy. Furthermore, we highlight the dependency of depolarization on an incident polarization state by imaging the retinal pigment epithelium (RPE) and using gold nanorods as a depolarizing phantom. We present polar decomposition and eigenvalue decomposition as a definitive measure of sample depolarization that is independent of an input polarization state, sample depth and sample birefringence. Definitive depolarization is demonstrated by imaging GNRs in lymphatic vessels of the hind limb of mice and human RPE in vivo.