Untitled Document

(*) Summary: A calibrated two-beam mode-mismatched thermal lens method aimed at determination of the absorption coefficient and the photo thermal parameters of nearly transparent materials was developed. This scheme provides the maximal possible response optimizing the sensitivity of the photo thermal lens experiment. The signal becomes independent from the Rayleigh parameters and waist positions of the beams. The method was applied to determine the absolute value of the thermal diffusivity and absorption coefficient of distilled water and organic solvents at 533 nm. Additionally, we generalized this thermal lens model to account for the Soret effect in binary liquid mixtures. The behavior of the Soret coefficient for water/organic mixtures was characterized, including its sign change with composition. The experimental results were compared with the existing data in the literature and good agreement was achieved.

(**) Biodata: Prof. Humberto Cabrera obtained his first degree in Physics at the University of Sofia in Bulgaria in 1990. His MSc degree was in optics at the University of Havana, going on to his PhD at the Venezuelan Institute for Scientific Research (IVIC).
    He was one the founders of the Applied Physics Centre at IVIC-Mérida, where he is currently Head of the Applied Optics Laboratory and scientific leader of various research projects. The main focus of research are new laser technologies for industrial and medical applications (***).
    His laboratory research is centered on optical techniques and methods for the characterization of media and processes in different scientific disciplines, in technology and biomedicine. They have facilities for thermal lens spectroscopy, speckle and self-mixing interferometry, optical tweezers, and photodynamic therapy.
    The laboratory offers advice in optics, laser technology, and optical radiation metrology for scientific and medical institutions, industries and research projects. In 2011 he was appointed a Regular Associate Member of the Abdus Salam International Centre for Theoretical Physics, Trieste, Italy.

(***) Recent publications
• Humberto Cabrera, Jorge Castro, Hilda C. Grassi, Efren D. J. Andrades, and Santos A. Lopez-Rivera, ” The Effect Photodynamic Therapy on Contiguous Untreated Tumor” , Dermatologic Surgery, 38, p. 1097-1099 (2012).

• Jorge Castro, Humberto Cabrera, H. Cristina Grassi, Efrén D.J. Andrades, “Treatment of Basal-Cell Carcinoma with Systemic Photodynamic Therapy”, Revista Colombiana de Cancerología 16 (3), p 154-161 (2012).

• Cabrera H., Castro J., Grassi H, and Andrades E., “First clinical experience using chlorin derivatives in Venezuela”, J Med. Med Science, 3 (9) p. 578-583 (2012).

• H. Cabrera, J Castro , and C. Grassi, “Photodynamic therapy for multiple basal cell carcinoma”, Ciencia 20, p. 52-56 (2012).

• Humberto Cabrera, Flaminio Cordido, Ana Velázquez, Pablo Moreno, Eloy Sira, and Santos A. López-Rivera, “Measurement of the Soret coefficients in organic/water mixtures by thermal lens spectrometry”. C. R. Mecanique 341, 372-377 (2013).

• Humberto Cabrera, “Experimental Investigation of Thermal Diffusion in Binary Fluid Mixtures“. Computational and Experimental Fluid Mechanics with Applications to Physics, Engineering and the Environment (Ed. Leonardo Sigalotti et al.). Springer-Verlag, Berlin ISBN: 978-3319001906. (2013).

• H. Cabrera, J.J. Suárez-Vargas, A. López, H. Núñez, G. Carvalh, G. Coceano, and D. Cojoc, “Experimental determination of trapping efficiency of optical tweezers“. Phil. Mag. Lett, DOI:10.1080/09500839.2013.835078. (2013).