Radiation properties of sources inside an opal structure modified by changing the incident angle of pump light

In this paper we discuss the strong incident angle dependence of the modification of emission in an opal structure. We study the emission with oblique incidence and find that we can control the emission properties, such as emission intensity and spectral width, just by changing the incident angle of pump light. Calculations with varying incident angles show that the band gap of the structure blue shifts with the increase of incident angle and the emission power of embedded sources is strongly determined by this gap change. In addition, the photonic band gap determines the emission spectrum. With the incident angle increasing, the width of emission spectrum increases first and then decreases.