OCT imaging with temporal dispersion induced intense and short coherence laser source

• Depth resolution can be increased in OCT by introducing temporal dispersion in probed beam.
• Photonic bandgap available in cholesteric liquid crystal is used to introduce this temporal dispersion.
• The coherence length is observed to be reduced by 730 times in a multimode He–Ne laser.

Lower coherence length and higher intensity are two indispensable requirements on the light source for high resolution and large penetration depth OCT imaging. While tremendous interest is being paid on engineering various laser sources to enlarge their bandwidth and hence lowering the coherence length, here we demonstrate another approach by employing strong temporal dispersion onto the existing laser source. Cholesteric liquid crystal (CLC) cells with suitable dispersive slope at the edge of 1-D organic photonic band gap have been designed to provide maximum reduction in coherence volume while maintaining the intensity higher than 50%. As an example, the coherence length of a multimode He–Ne laser is reduced by more than 730 times.