Large Third-order Optical Non-linearities of Spin-cast Thin Films of Novel Metallo-naphthalocyanines

Abstract

Third-order non-linear optical susceptibilities of silicon, germanium, tin, aluminum, manganese and vanadium naphthalocyanine derivatives measured by third-harmonic generation technique from 1.05 μm to 2.1 μm are reported. Our results show the dependence of χ(3)(–3ω;ω,ω,ω) values on the variation of the central metal atom associated to different metal-ligand charge-transfer interactions. Silicon naphthalocyanines ( SiNc ) showed the χ(3)(–3ω;ω,ω,ω) values on the order of 10−10 esu at 1.5 μm, this does not appear to be due to a three-photon resonance, instead the increase in χ(3) could be the two-photon resonance lying just above the one-photon state. Degenerate four-wave mixing measurements on thin films of a SiNc derivative yielded the χ(3)(–3ω;ω,ω,ω) value as high as 5.0 × 10−7 esu at 800 nm, enhanced by one-photon resonance near the Q-band peak region. The figure of merit χ(3)/α at 800 nm is quite large corresponding to 4.2 × 10−12 esu cm. Effect of the metal atoms and plausible resonance contribution accounting for large third-order optical non-linearity of naphthalocyanines are discussed.