Abstract
Our research is mainly about designing flat focuser by using photonic crystal structure. By arranging non-periodic photonic crystal with square lattice, we can distribute the phase for a focusing element like traditional curved focusing lens. It let us have much more design of freedom by using square lattice, we can either gradually vary the period between lattices or the radius of cylindrical holes. The center wavelength we design is at 1310 nm, and the not only concern about the overall transmission of the photonic crystal slab (PCS), we also introduce the concentration of the focusing spot at focal plane. In this thesis, we design two cases of the PCS focuser, one has bigger numerical aperture (NA), the other one has a smaller NA. The overall transmission is above 85% for both cases, and for smaller NA case is up to 94%. But for the application of receiver, the concentration of the focusing spot is also a key factor. At last, the PCS focuser of large NA has no improvement compared to single mode source. But the smaller NA case has great improvement for concentration. The 90% of the power can be confined within circle radius of 3.7 micron meter.