Diffraction of light from thin-film polymethylmethacrylate opaline photonic crystals

Abstract

Photonic crystals in the form of large area thin films consisting of closely packed polymethylmethacrylate beads were sedimented on glass substrates. The high ordering of the opaline films made it possible to observe a number of fine features in the optical diffraction, including Fabry-Perot oscillations of the reflectivity and branching of the angular dispersion of the Bragg resonances with increase of the angle of incidence of the light beam. Results of calculations of the photonic band structure and simulations of the reflectance spectra agree well with experimental observations.

Enhanced Bragg reflections from size-matched heterostructure photonic crystal thin films prepared by the Langmuir-Blodgett method

“…Thus by plotting 2 vs sin 2 it is possible to obtain the value of D. It should be noted that, in the angular region of 45°for a fcc lattice, diffraction from the ͑200͒ plane also appears and thus the expression given above is no longer correct and a double diffraction peak appears. This phenomenon has been explained by Romanov et al 12 However, for films formed by the LB method this double peak does not appear and the apparent diameter of the particles derived from the Bragg expression is somewhat larger than the value obtained by other methods showing that although an ordered structure appears it is not fcc. This feature of the LB growth of photonic crystals from colloidal particles will be discussed in detail elsewhere.…”

Erasing diffraction orders: Opal versus Langmuir-Blodgett colloidal crystals

“…Exceptions from the diffraction model occur in the angle range from 40°to 50°, where multiple diffraction takes place. 16 This phenomenon is well explained in the PBG model of the opal. 17 The dispersion of the 01T transmission minimum in the spectra of the LB crystal obeys the same law as the ͑111͒ diffraction branch of the opal ͑Fig.…”

“…These minima correspond to the gaps between 1-4 and 5-6 eigenmodes in the PBG structure of the opal. 16 These minima show the losses of the incoming beam due to its coupling to the diffraction orders of a 3D grating. As illustrated in Fig.…”

( 2 + 1 ) -dimensional photonic crystals from Langmuir-Blodgett colloidal multilayers

“…Moreover, no spectroscopic evidence has been demonstrated to prove the formation of a 3D lattice in LB multilayers. 9 On the other hand, optical spectra of 2D hexagonal sphere crystals were studied only at wavelengths shorter than the sphere diameter, 10,11 i.e., in the range of their 2D PBG.…”