Fiber to planar waveguide interconnects and planar beam modifiers are crucial for the implementing efficient silicon photonic devices for communication applications. In this work, broadband performance in the 1300nm- 1600nm region is ensured by appropriately controlling the spatial variation of the effective index of silicon to realize a beam splitter (1×2) and a quarter wave GRIN lens. Sub wavelength (λ/10) 1D periodic array of low-index air holes in the high index host silicon, along the propagation direction of the optical beam, is repeated, with decreasing or increasing periodicities in the transverse direction to form a 2D photonic crystal(PhC) structure to realize a beam splitter or GRIN lens respectively. The lowest wavelength of 1300nm is used as the design wavelength to ensure less than λ/10 periodicities for all useful wavelength ranges. A decreasing transverse periodicity of 1D hole arrays from the horizontal axis at the centre along the direction of propagation results in formation of 2 high index wave guiding structures towards the edges of the crystal separated by low effective index central region thus leading to formation of a beam splitter. On the other hand increasing transverse periodicity of the defect array leads to lowering of effective index gradually to the edges of the device resulting in the formation of a GRIN lens. FEM analysis of the propagation of electromagnetic field through these structures show that GRIN lens focuses the input beam to a mode field diameter (MFD) of 1.5μm and that MFD of each output arm of the 1×2 splitter is 1.75μm. The decrease in intensities at the focal point of the GRIN lens with increasing input wavelength in the 1300-1600nm is found to be within 6% and that in the two arms of the beam splitter is found to be less than 13%.