OPTICAL HETERODYNE TECHNIQUES FOR PHOTOACOUSTIC AND PHOTOTHERMAL DETECTION H.K. Wickramasinghe, Y. Martin, D.A.H. Spear et E.A. Ash J. Phys. Colloques, 44 C6 (1983) C6-191-C6-196 DOI: 10.1051/jphyscol:1983629