Negative-index imaging by an index-matched photonic crystal slab

We report negative-index imaging at near infrared wavelengths using a photonic crystal (PC) with an effective index matched closely to air as the incident medium. A tapered waveguide is used to generate a point-sourcelike object field; and to probe the focusing behavior of the PC, an array of $500\mathrm{nm}$ wide photonic wire waveguides is placed in the backplane of the PC lens. This represents a sampling of the image field at the rate of one data point per free space wavelength $\left({\lambda }_0\right)$. For TM polarization, a well-defined $1.7{\lambda }_0$ spot is observed, while the TE polarization lies near the photonic band edge and exhibits spreading and low transmission. We also investigate the wavelength dependence and experimentally show the performance of the negative index lens as a function of frequency.