Induced heating by nonlinear absorption in LiNbO3-type crystals under continuous-wave laser irradiation

• Light-induced heating under CW laser light is investigated in LiNbO3-type crystals.
• Two-photon excited polarons work as absorption center, generating heat source.
• The accumulation effect of the polarons causes catastrophic breakdown of crystals.
• The threshold intensity is estimated to be on the order of MW/cm2 for LiNbO3.

We investigate light-induced heating by nonlinear absorption in LiNbO3-type crystals under continuous-wave (CW) laser irradiation. The heat source is one-photon absorption by long-lived excited states created by two-photon absorption. The accumulated effect of excited states, which act as light absorbers, is significant for a CW laser. Light-induced heating causes catastrophic CW laser breakdown in LiNbO3-type crystals in which the band-gap energy is less than twice the photon energy and in which long-lived excited states, like polarons, can exist. For LiNbO3, the threshold intensity for catastrophic breakdown is estimated to be in the order of MW/cm2.