Ultrafast Nonlinear Absorption and Second Harmonic Generation in Cu_0.33In_1.30P₂S₆ van der Waals Layered Crystals

Abstract

The advancement of ultrafast photonics and optoelectronic devices necessitates the exploration of new materials with optical and chemical stability to implement practical applications. Layered quaternary metal-thio/selenophosphate has attracted much interest over the past few years. Ferroelectric CuInP 2 S 6 (CIPS) is an emerging material that belongs to this family. When synthesized with Cu deficiencies, CIPS forms self-assembled in-plane heterostructures, which in turn exhibit properties that are both compositionally and thermally dependent. These characteristics can be explored for applications in nonlinear optoelectronic and photonic devices. Herein, we study the second and third order nonlinear optical behavior of Cu 0.33 In 1.30 P 2 S 6 bulk heterostructure. We observed large two photon induced nonlinear absorptions and self-defocusing at 1032 nm pulsed laser excitation using the Z-scan technique. Furthermore, we identified a polarization-dependent second harmonic signal and determined the laser-induced optical damage threshold. Our observations allow for the designing of optoelectronic and ultrafast photonic devices based on these materials.

AgScP2S6 van der Waals Layered Crystal: A Material with a Unique Combination of Extreme Nonlinear Optical Properties

“…Later the same group reported a detailed study on NLO response and ultrafast dynamics of photogenerated carriers in the AgInP 2 S 6 crystal . Recently our group demonstrated NLO properties of the Cu 0.33 In 1.34 P 2 S 6 crystal at 1032 nm excitation …”

“…Next, we utilized the Z-scan technique to address the third order optical nonlinear properties of AgScP 2 S 6 . Details of our Z-scan setup can be found in our recent work . We used a 1032 nm (1.20 eV) laser as the excitation source with a pulse duration of 77 fs; the repetition rate was 1 kHz, and we coupled the laser with a lock-in amplifier.…”

“…We characterized the Gaussian focal spot radius to be 48 μm. We calibrated our setup with zinc selenide (ZnSe) single crystal as reported in our previous work …”

“…Furthermore, to ensure TPA as observed in the Z-scan, we recorded two photon excitation emission spectra at different excitation energies. Figure shows the two photon induced photoluminescence (2PPL) spectra at 1.55 eV (800 nm) and 1.20 eV (1032 nm) for AgScP 2 S 6 with an acquisition time of 2000 ms (the experimental details of our two photon induced PL setup is found in our previous work) . The two photon induced PL spectrum obtained at 1.55 eV excitation is analogous to the one obtained for one photon excitation at 3.10 eV (400 nm).…”

“…Details of our Zscan setup can be found in our recent work. 23 We used a 1032 nm (1.20 eV) laser as the excitation source with a pulse duration of 77 fs; the repetition rate was 1 kHz, and we coupled the laser with a lock-in amplifier. Prior to performing our Z-scan traces, we ensured a Gaussian beam profile using spatial filtering; we then used a 20 cm focal length plano-convex lens for focusing the light on to the sample.…”