International Journal of Thermophysics vol:36 issue:5 pages:819-828
Bio-organic materials such as bones, teeth and tendon generally show nonlinear optical, pyro- and piezoelectric properties, implying a permanent polarization, the presence of which can be rationalized by describing the growth of the sample and the creation of a polar axis according to Markovs theory of stochastic processes.
Two proven, versatile techniques for probing spontaneous polarization distributions in solids are Scanning PyroElectric Microscopy (SPEM) and Second Harmonic Generation Microscopy (SHGM). We demonstrate the combination of pyroelectric scanning with SHG-microscopy in a single experimental setup leading to complementary pyroelectric and nonlinear optical data, providing us with a more complete image of the polarization in organic materials. Crystals consisting of the known polar and hyperpolarizable material, CNS (4-chloro-4'-nitrostilbene) are used as a reference sample, to verify the functionality of the setup, with both SPEM and SHGM images revealing the same polarization domain information. In contrast, feline and human nails exhibit a pyroelectric response, but a second harmonic response is absent for both keratin containing materials, implying that there may be symmetry-allowed SHG, but with very inefficient second harmonophores. This new approach to polarity detection provides additional information on the polar and hyperpolar nature in a variety of (bio) materials.