Integrated optic, stellar interferometric two-beam and three-beam combiners have been designed and fabricated
for operation in the L band (3 μm - 4 μm). The devices have been realized in titanium-indiffused, x-cut lithium
niobate substrates, and on-chip electro-optic fringe scanning has been demonstrated. White light fringes were
produced in the laboratory using the two-beam combiner integrated with an on-chip Y-splitter. Furthermore, a
new design for next-generation, broadband, achromatic, astronomical, beam combiners operating in the N band
(8 μm - 12 μm) is proposed and analyzed. The design is based on adiabatic mode-evolution couplers fabricated
using Ge/Si heterostructure rib waveguides.