Observation of giant photodarkening and temperature mediated transition to photobleaching in As2Se3/Ag/Se trilayer

• 532 nm continuous wave laser induced giant photodarkening (PD) in As2Se3/Ag/Se trilayer.
• Giant PD is permanent in nature which is as high as ~ 93% of total effect.
• Trilayer exhibits PD at 20 and 300 K and shows crossover to photobleaching at 420 K.
• We observed transition from three to two stage kinetics with increase in temperature.
• Raman spectra provide direct evidence of lightinduced structural rearrangements.

In this article, we report giant photodarkening (PD) in As2Se3/Ag/Se trilayer when illuminated with 532 nm continuous wave laser. Upon illumination, absorption edge of the trilayer exhibits dramatic redshift of ~ 100 nm that is much larger than any previous results. Impressively PD is permanent in nature which contributes ~ 93% of the total change and is accompanied by a weak transient part. Further, the temperature dependent light induced studies reveal remarkably contrasting characteristics of giant PD at 20 K, which switch to weak photobleaching (PB) at 420 K. Raman study on as-prepared and illuminated samples provide new insights that illumination enhances the number of Sen chains over AsSe3/2. We foresee that giant PD is useful in fabricating waveguides and memory devices.