Single-detector polarization-sensitive optical frequency domain imaging using high-speed intra A-line polarization modulation

Abstract

We demonstrate a novel high-speed polarization-sensitive optical frequency domain imaging system employing high-speed polarization modulation. Rapid and continuous polarization modulation of light prior to illumination of the sample is accomplished by shifting the frequency of one polarization eigenstate by an amount equal to one quarter of the digitization sampling frequency. This approach enables polarization-sensitive imaging with a single detection channel and overcomes artifacts that may arise from temporal variations of the birefringence in fiber-optic imaging probes and spatial variation of birefringence in the sample.

Fig. 1

Schematic of the PS-OFDI system. FBG, fiber Bragg grating; PC, polarization controller; PBS, polarization beam splitter; FS, frequency shifter; GB, AMTIR glass block; Pol, polarizer; BS, beam splitter; BR, balanced receiver, HS-DAQ, high-speed digitizer.

Fig. 2

Phase plot and the Poincaré sphere representation. The parameter Δϕ_xy represents the phase difference between orthogonal components of the light polarization incident on the sample. Gray dots in the phase plot and the Poincaré sphere representation show the polarization states on the sample when the digitizer acquires data; Δϕ_xy=mod[|ϕ_x-ϕ_y|].

Fig. 3

(a) Intensity, (b) phase retardation, and (c) unwrapped phase retardation images of chicken muscle ex vivo. Scale bar, 1 mm.

Fig. 4

Intensity and phase retardation images of a swine coronary artery ex vivo acquired through the rapidly spinning fiber-optic catheter.