Frequency upconversion and two-photon absorption of salicylaldehyde azine 1

• Infrared-to visible upconversion was observed from salicylaldehyde azine crystals.
• This phenomenon was characterized as a two-photon absorption process.
• Large molecule’s two-photon absorption cross-section was measured.
• This organic crystal is a promising material for nonlinear photonic applications.

Two-photon absorption and two-photon excitation fluorescence of salicylaldehyde azine 1 crystals were investigated. It was observed an intense visible fluorescence when this material was excited with a laser tuned at the near infrared region. Varying the laser intensity we characterized this phenomenon as a simultaneous two-photon laser absorption process. Using open aperture Z-scan measurements we characterized this two-photon absorption phenomenon and measured the value of the two-photon absorption cross-section of this molecule to be equal to 87 GM. Our results indicate that this is a promising organic material aiming nonlinear photonics applications.