We are planning to use a light source with 18nm band width, mode lacked laser for OCT imaging. We are just at initial stage. How do we measure point spread function and coherence length for this source experimentally?
Thanking u
If you build an interferometer with two mirrors, and then translate one of your mirrors, the intensity of interference you measure will increase and then return to baseline as you move the mirror through a point where the arm lengths of the interferometer match. Plotting this intensity vs mirror position will give a peak, with a width equal to the coherence length of the laser.
Dear Alexander Malm, Thank you for your answer. The method you have mentioned is for Coherence length, that we have already measured, would you relate the coherence length and point spread function. Correct me if Im wrong. Thank you.
Dear Coherence team! If I understand Your question right it is connected with the spatial coherence of the mode-locked laser beam and a spatial beam divergence for the case. In the typical case in mode-locked regime laser operates ought operate on the many main longitudinal modes with spectral beam 18nm You provided. No transversal mode shall participate in oscillation. The spatial coherence in the case equals the total cross section of the laser beam and beam divergence appears to be diffraction one with the correcting coefficient for Gauss beam. In the case when mode-locking is not total due to participation of transversal modes or due to not appropriate operation of a phase locking modulator, the size of the spatial coherence will be less and divergence will increase correspondingly. So to my mind Your problem connected with the beam divergence measurements that described in many tutorials. Our original method of divergence measurements You can find in the next reference: "Interferometric method of measuring the angular divergence of laser beams"
EA Tikhonov, OV Kiselev - Journal of Optical Technology, 2007, 74 (4), 258-262
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