Design of achromatic holographic grating couplers for substrate and backplane optical interconnects

Holographic backplane optical interconnects for multi-board three-dimensional packaging of electronic modules have demonstrated certain interesting features. However, the effects of laser diode wavelength shifts, caused by variations in environmental temperatures and by bias fluctuations can cause undesirable coupling alignment problems, including shifting of the coupling angle and optical spot positions. These chromatic problems are particularly serious in terms of coupling from backplane to board-level waveguide interconnect networks. To solve these problems, an achromatization technique for holographic backplane couplers under substrate beam propagation geometry is presented in this paper.