Low insertion loss is essential for the practical deployment of silicon photonics. In this talk I shall review some of our recent work towards improving the performance of waveguide grating couplers for coupling between silicon waveguides and standard single mode fiber. I shall introduce the shift-pattern polysilicon overlay grating which can reduce insertion loss at the fiber-chip interface to under 1dB. The overlay can also be engineered to make polarization independent grating couplers with less than 0.5dB PDL. I shall also describe new approaches for wide optical bandwidth waveguide grating couplers, which can provide ultrawide 1dB optical bandwidth of over 200nm. I shall also discuss some emerging applications for silicon photonic integrated circuits and describe some of our recent work optical matrix processors for optical signal processing applications, optical convolution and discuss the observation of Kerr-Raman frequency comb generation in multimode silicon resonators.