We have identified photothermal displacement as a mechanism for optical bistability (OB) in prism coupling into absorbing planar waveguides: heating by the absorbed incoupled power causes a buckling of the waveguide, a reduction in air-gap width, and thus an increase in incoupling efficiency and a positive feedback. We developed a theory of this OB that qualitatively agrees well with experimental results obtained by coupling argon-laser light into indium–tin oxide layers as strongly absorbing waveguides. This new OB is quite different from dispersive OB in prism or grating couplers caused by a power-dependent effective guide index.
© 1987 Optical Society of America
Original Manuscript: November 7, 1986
Manuscript Accepted: January 6, 1987
Published: April 1, 1987
W. Lukosz, P. Pirani, and V. Briguet, "Optical bistability by photothermal displacement in prism coupling into planar waveguides," Opt. Lett. 12, 263-265 (1987)