Real-Time Detection of Long Lived Near Infrared luminescence from Colourless Cubic Zirconia by Time-Gated Imaging

Abstract

Here, we report a long-lived ms time scale decay luminescing in the near infrared >800 nm present in productions of ‘white’ colourless, facetted yttrium stabilized cubic zirconia and observed using time-gated imaging. The spectrum of the strong luminescing feature also has characteristics of Neodymium (Nd3+) and has a multiexponential decay behaviour. Real-time detection of cubic zirconia mounted in diamond jewellery containing very small stones (≤0.01 ct) is made possible, where observation by loupe is more challenging or other conventional techniques impractical and or slow to implement. The near infrared observed can be excited using a low-cost and eye/skin safe-visible green LED light source and the time-gated imaging of the luminescence using a machine vision monochrome camera. The use of near infrared, time-gated detection in combination with other verification instruments increases the robustness of screening diamond parcels. Therefore, it is recommended that any stone exhibiting strong delayed luminescence in the near infrared be treated with caution, as this is not a typical feature found in this precious gemstone. In this case, the instrument developed was expanded to incorporate a white LED illumination ring as a viewfinder, in order to aid the inspection of loose and mounted configurations.

Keywords

• cubic zirconia
• simulants
• diamond substitutes
• CZ
• time-gated
• real-time