Bulky-Polymethylpentene Inscription Using Shg Femtosecond Laser Beams with Angular Momentums

Abstract

Thermoplastic polymer, poly methyl pentene (PMP), has been investigated for laser inscription. Near-ultraviolet (NUV) laser beam was generated by using second harmonic method (SHG) and focused by using lenses with numerical aperture (NA) in the range 0.08 - 0.7. A spatial light modulator addressed with computer-generated holograms created helical wavefronts carrying orbital angular momentum (OAM) at 775nm. Conservation of OAM during the SHG conversion is demonstrated. Using an advanced spectrometer to supercontinuum (SC) signal, it is observed that the integration of photonic energy in Anti-Stokes region is scale linearly with OAM. Laser beam carrying OAM is also investigated with spin angular momentum (SAM) . With high states of OAM, complex filamentary structures converging to the focus are observed which collapse to multiple filaments, in accord with theoretical expectations. Less coupling between two modes of AM in filamentation (FL) was observed in NA > 0.1 region. Linear polarization effect is clearly due to components of the strong third order susceptibility $\chi^{(3)}$ which is for the first time in PMP. Using lenses with NA>0.4. Spiral structure accompanied with rotation sense of optical vortex are constructed, suggesting that chirality structure was formalized in exposure zone. By using longitudinal inscription, tubular structures accompanied with waveguide efect can be constructed in bulky polymer.

Keywords: Femtosecond Laser, Spatial Light Modulator, SAM/OAM