Measurement of Photoluminescence of Cu₂O at 2K

We present our measured photoluminescence of the quadrupolar transitions of the yellow series excitons of cuprous oxide at 2K. By tuning the excitation energy in the two-photon quadrupolar absorption scheme of Cu₂O, it is found that the band-gap value associated with this optical process can be characterized by a sharp resonance at 2.036eV at cryogenic temperature. This energy value is helpful to guide a proper excitation for creating cold excitonic gas in this crystal.