Optical Coherence Tomography with Classical Phase-Sensitive Light

Optical coherence tomography (OCT) produces 3-D imagery through focused-beam scanning (for transverse resolution) and interference measurements (for axial resolution). Quantum optical coherence tomography (Q-OCT) offers a factor-of-two improvement in axial resolution and the advantage of even-order dispersion cancellation when it is compared to conventional OCT (C-OCT). These features have been ascribed to the non-classical nature of the biphoton state employed in former, as opposed to the classical state used in the latter. We have introduced a new OCT configuration, called phase-conjugate OCT (PC-OCT), which shows that non-classical light is not necessary to reap Q-OCT's advantages. PC-OCT uses classical-state signal and reference beams, which have a phase-sensitive cross-correlation, together with phase conjugation to achieve the axial resolution and even-order dispersion cancellation of Q-OCT with a signal-to-noise ratio that can be comparable to that of C-OCT.