Defect solitons in optically induced kagome photonic lattices in photovoltaic-photorefractive crystals

We study defect solitons (DSs) and their stability in optically induced kagome photonic lattices with a defect in photovoltaic-photorefractive crystals. We show that these DSs exist only in the semi-infinite gap when the defect is positive and both in the semi-infinite gap and the first gap when the defect is negative. For a positive defect, DSs are stable in the low power region and unstable in the high power region. For a negative defect, DSs in the semi-infinite gap are stable in the moderate power region and unstable in the high and low power regions. In the first gap, DSs are stable in the all power region for the low negative defect depth and in the high power region for the high negative defect depth. We find that the stable region of DSs increases with the defect depth when the defect is positive and decreases with an increase in the defect depth when the defect is negative.