  A mirrored transformation optics (MTO) approach is presented to overcome the
material mismatch in transformation optics. It makes good use of the reflection
behavior and introduce a mirrored medium to offset the phase discontinuities.
Using this approach, a high-performance planar focusing lens of
transmission-type is designed, which has large concentration ratio than other
focusing lens obtained by generalized Snell law. The MTO will not change any
functionality of the original lens and promising potential applications in
imaging and light energy harvesting.
