  Localized polymerization in subwavelength volumes using two photon dyes has
now become a well-established method for fabrication of subwavelength
structures. Unfortunately, the two photon absorption dyes used in such process
are not only expensive but also proprietary. LTPO-L is an inexpensive, easily
available single photon photoinitiator and has been used extensively for single
photon absorption of UV light for polymerization. These polymerization volumes
however are not localized and extend to micron size resolution having limited
applications. We have exploited high quantum yield of radicals of LTPO-Lfor
absorption of two photons to achieve localized polymerization in subwavelength
volumes, much below the diffraction limit. Critical concentration (10wt%) of
LTPO-Lin acrylate (Sartomer) was found optimal to achieve subwavelength
localized polymerization and has been demonstrated by fabricating 2D/3D complex
nanostructures and functional devices such as variable polymeric gratings with
nanoscaled subwavelength resolution. Systematic studies on influence of LTPO-L
concentration on two photon polymerization of commercially available
photopolymer (Sartomer) show that resolution of the fabricated structures
critically depend on loading of LPTO-L. This is expected to unleash the true
potential of two photon polymerization for fabrication of complex polymeric
nanodevices at a larger scale.
