Full, complex dispersion calculations for the TE- and TM-guided modes are shown for a 150-nm-thick film, periodically patterned with alternating stripes of β- and glassy-phase PFO. A period of Λ=290 nm was selected with the β- and glassy-phase regions spanning, respectively, 75% and 25%. In (a), the modal dispersion, displayed in a reduced zone scheme, highlights the distinct band gaps (horizontal grey bars) for both TE (blue) and TM (red) modes. Propagation losses for both modes are shown in (b) along with the absorption in the β-phase region (dotted line). The unit cell of the photonic structure is shown in (c), with the upper and lower red horizontal lines indicating film interfaces with air and the substrate, respectively. The vertical solid black line delineates the centre of a single period and the vertical dashed lines delineate the edges of the β-phase stripe. The stripe long axis runs into the page, in the y-direction. The illustrative calculated field distributions (|Hy(x,z)|2) at 454.5 and 458 nm (darker=larger modulus) clearly reveal the characteristic standing wave patterns (and their spatial displacement) for wavelengths selected to lie on either side of the TM band gap.