Noncollinear frequency doubling in a random nonlinear photonic crystal of strontium tetraborate via nonlinear diffraction from virtual beam is investigated. This effect is shown to be useful for ultrashort pulses characterization in broad spectral range. Nonlinear photonic crystals of strontium tetraborate are a promising medium for ultrafast diagnostics in short-wavelength applications.

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We propose an elegant approach to produce photonic band gap structures with multiple photonic band gaps (PBGs) by constructing quasiperiodic photonic crystals (QPPCs) composed by a superposition of photonic lattices with different periods. Generally QPPC structures exhibit both aperiodicity and multiple PBGs due to their long-range order. They are described by a simple analytical expression instead of quasiperiodic tiling approaches based on substitution rules. Here we describe the optical properties of quasiperiodic photonic crystals exhibiting two PBGs that can be tuned independently. PBG interband spacing and their depths can be varied by choosing appropriate reciprocal lattice vectors and their amplitudes. These effects are confirmed by the proof-of-concept measurements made for the porous silicon based QPPC of the appropriate design.