Twin defect modes are found in one-dimensional photonic crystals stacking with single- negative-permittivity and single-negative-permeability media layers and a single-negative defect. The frequency interval of the two defect modes can be changed by varying the thickness of the defect layer or the thickness ratio of the two stacking layers. Conditions for the emergence of such twin defect modes only relate to the phase thicknesses of the defect layer and the two stacking layers. In addition, the electric fields at the frequencies of the defect modes are strongly localized at the interfaces between the defect layer and its adjacent layers.
We propose a new scheme of attosecond pulse generation by starting from a narrow-band transform-limited highpower solid-state laser and phase lock the fundamental and its first four cascaded harmonics generated by the second-order nonlinear optical processes. The relative phase among the optical fields of the harmonics can be maintained a constant at least for thousands of nanosecond pulses. The worst-case relative phase fluctuation is 0.04π rad. It is shown that sub-single-cycle (∼ 0.37 cycle) sub-femtosecond (360 attosecond) pulses with carrier-envelope phase (CEP) control can be generated in this manner. The peak intensity of each pulse exceeds 10 14 W/cm 2 when it is focused to a spot size of 20 μm. We also demonstrate synthesis of square and saw-tooth waveforms. Correlation signal, a.u. 1 2 3 0 2 4 8 6 Time delay, fs CEP = 0 4 2 0 -2 -4 1 0 -1 The electric field synthesized waveform retrieving by the method of shaper-assistant linear cross-correlation at CEP = 0. The inset figures show the simulation of electric field waveform in black solid line and pulse envelope in blue dash line
From the view of crystallography, a systematic theoretical study on one-step formation of two-dimensional compound photonic lattices by four noncoplanar elliptical waves is presented. A general formula for the interference intensity of N elliptically polarized waves, and relevant phase shifts that compensate for the initial phases and control the relative position and size of the motifs, have been deduced. Using appropriate polarization configurations, four kinds of beam geometries can be used to form various compound lattices. This provides an ideal new experimental platform for fabricating large-area compound photonic lattices.
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