Silicon nitride optical phased array for waveguide integration of atomic vapour MEMS cells

The design, fabrication and characterisation of a silicon nitride optical phased array (OPA) for waveguide integration with flip-chip bonded rubidium (Rb) atomic MEMS vapour cells are demonstrated. A one-dimensional OPA with a symmetric splitter tree design at 780 nm wavelength is fabricated by electron-beam lithography and plasma dry-etching. The waveguides were cladded with silicon dioxide before bonding to an Rb MEMS vapour cell. The characterisation was performed by end-fire coupling a 780.24 nm laser to the waveguide by a lens fibre. A saturated absorption spectroscopy measurement revealed the ~ 6 MHz hyperfine transition absorption dips that can be utilised for laser frequency stabilisation for atomic cooling.