Maintaining polarization in polarimetric multiphoton microscopy

Polarimetric measurements in multiphoton microscopy can reveal information about the local molecular order of a sample. However, the presence of a dichroic through which the excitation beam propagates will generally scramble its polarization. We propose a simple scheme whereby a second properly‐oriented compensation dichroic is used to negate any alteration regardless of the wavelength and the initial polarization. We demonstrate how this robust and rapid approach simplifies polarimetric measurements in second‐harmonic generation, two‐photon excited fluorescence and coherent anti‐Stokes Raman scattering. Illustration of the polarization maintaining strategy with the compensating dichroic oriented such that its s‐ and p‐axes are interchanged with these of the primary dichroic. Polarimetric measurements in multiphoton microscopy can reveal information about the local molecular order of a sample. However, the presence of a dichroic through which the excitation beam propagates will generally scramble its polarization. A simple scheme is proposed whereby a second properly‐oriented compensation dichroic is used to negate any alteration regardless of the wavelength and the initial polarization. It is demonstrated how this robust and rapid approach simplifies polarimetric measurements in second‐harmonic generation, two‐photon excited fluorescence and coherent anti‐Stokes Raman scattering.