Photorefractive photonic crystals fabricated with PMMA and 5CB based materials using three-dimensional colloidal crystals

The variation of the refractive index is the key property of photorefractive materials and an important factor that affects photonic crystals. Therefore, photorefractive photonic crystals are interesting optical materials in physics. One of the typical groups of photorefractive materials, polymer dispersed liquid crystals (PMMA, 5CB, and C60), are filled into three dimensional silica colloidal crystals by solvent-induced phase separation to fabricate photonic crystals. The stop band shifts to shorter wavelength when a low voltage is applied. By using the z-scan and two-beam coupling technique, several band gap dependent optical properties of photorefractive photonic crystals are studied whilst continuously adjusting the wavelength of the stop band. The third-order nonlinear refractive coefficient is enhanced at the edge of the photonic stop band. The photorefractive diffraction efficiency achieves a maximum value when the stop band wavelength overlaps with the laser beam wavelength.