Polarization-resolved second harmonic generation microscopy with a four-channel Stokes-polarimeter

Abstract

We developed a four-channel photon counting based Stokes-polarimeter for spatial characterization of polarization effects in second harmonic generation (SHG). We have implemented a calibration technique allowing quantitative measurement of polarization parameters, such as the degree of polarization (DOP), degree of linear polarization (DOLP), degree of circular polarization (DOCP), as well as anisotropy from the acquired Stokes parameters. The technique is used as contrast mechanism to characterize the polarization properties from two potassium dihydrogen phosphate (KDP) micro-crystals and collagen type-I in SHG microscopy.

Ultrastructural features of collagen in thyroid carcinoma tissue observed by polarization second harmonic generation microscopy

“…The SHG signals from non-tumorous thyroid tissue and tumors differed significantly in their DOLP values, indicating that tumor tissue has a greater degree of ultrastructural collagen disorder. This conclusion is somewhat similar to a previous study of the DOLP of SHG from collagen type I gels formed from bovine tendon [19]. Generally, care must be taken in interpreting DOLP data, since the circular polarization component can alter the DOLP due to SHG radiation propagation through a birefringent sample.…”

Investigating starch gelatinization through Stokes vector resolved second harmonic generation microscopy

“…Stokes vector based SHG microscopy resolves the polarization states of the SH signal and allows the deduction of the molecular organization of collagen, skeletal muscle, starch etc 111213…”

Imaging molecular structure with Stokes-polarimeter based second harmonic generation microscopy

“…The experimental arrangement of our SHG imaging system used to measure the polarization states of the SHG signal is described in detail in [20]. A femtosecond Ti:Sapphire (Coherent Mira Optima 900-F) laser oscillator was as the excitation light source.…”

“…We used SH signal at 400 nm as a light source and was created by focusing the 800 nm laser beam into KDP micro-crystals (SIGMA, Germany) immersed in oil for optimal index matching and sandwiched between two cover glass slips. The SH light is collimated by the condenser lens in transmission mode then passed through the PSG as described in the Materials and Methods of our previous work [20] to generate 0°, 90°, 45° and RC polarization states. We have optimized our fourchannel Stokes-polarimeter at 400 nm by minimizing the propagation of relative errors on the intensities after multiplication by the instrument matrix (A 4x4 ) -1 .…”