Saturable absorption properties at 1.54 µm of Cr²⁺:ZnS prepared by thermal diffusion at hot isostatic pressing

Abstract

Polycrystalline zinc sulfide (ZnS) samples obtained by chemical vapour deposition were doped with Cr 2+ ions using hot isostatic pressing (at 100 MPa/1250 °C). Their structure was studied by means of x-ray diffraction, SEM and Raman spectroscopy. The Cr 2+ :ZnS samples exhibited excellent transparency in the near-IR. Absorption saturation of Cr 2+ :ZnS is demonstrated at 1.54 µm ( 5 T 2 ( 5 D) → 5 E( 5 D) transition of Cr 2+ ions in tetrahedral sites) for ns-long pulses yielding a saturation fluence of 0.16 ± 0.03 J cm −2 . The laser-induced damage threshold is 6.0 ± 0.5 J cm −2 . The synthesized polycrystalline Cr 2+ :ZnS is promising for passive Q-switching of erbium lasers emitting at 1.5-1.7 µm.

Watt-level ultrafast laser inscribed thulium waveguide lasers

“…Considering the maximum F in values obtained on our experiments, LIDT !3.3 AE 0.5 J/cm 2 for both materials. This value agrees well with a recent report [92].…”

“…They provide (i) a broad and intense absorption in the near-IR related to the 5 T 2 → 5 E( 5 D) transition of Cr 2þ ions in tetrahedral (T d ) sites, Fig. 8(a); (ii) high ground-state absorption (GSA) cross-sections, σ GSA , (iii) low excited-state absorption and (iv) acceptable laser-induced damage threshold (LIDT) [90][91][92]. At the laser wavelength of~1.84 μm, the σ GSA are 0.62 Â 10 À18 cm 2 (for Cr 2þ :ZnS) and 0.95 Â 10 À18 cm 2 (for Cr 2þ :ZnSe).…”

Design and modeling of a passively Q-switched diode-pumped Thulium laser at 2.3 μm

“…These values are exceeding the calculated saturation fluence of the SA FS, so that it is deeply bleached. Besides, the determined Fin values are below the LIDT for zinc chalcogenides (e.g., LIDT = 6.0 ± 0.5 J/cm 2 for Cr 2+ :ZnS for ns pulses [12]).…”

“…Zinc chalcogenide crystals (ZnS and ZnSe) doped with chromium ions (Cr 2+ ) [4] are known as efficient SAs for lasers emitting at ~2 μm [5], i.e., those based on thulium (Tm 3+ ) [6,7] and holmium (Ho 3+ ) [8,9] ions. This is because they provide broad and intense absorption bands owing to the 5 T2 → 5 E( 5 D) transition of Cr 2+ ions in Td sites [10], high GSA cross-sections and weak excited-state absorption [11,12] and good thermal properties. In particular, Tm lasers emiting at ~1.9 μm (the 3 F4 → 3 H6 transition) passively Q-switched by Cr 2+ :ZnS and Cr 2+ :ZnSe SAs and featuring both short pulse durations (down to sub-ns) [13] and relatively high pulse energies (mJ-level) [6,7,14] were demonstrated.…”

Passive Q-switching of a Tm:LiYF4 Waveguide Laser by Cr2+:ZnSe and Co2+:ZnSe Saturable Absorbers

“…Nowadays, chalcogenide crystals (ZnS and ZnSe) doped with chromium (Cr 2+ ) ions [14] are widely used as "slow" SAs of bulk solid-state lasers emitting in the spectral range of ~2 μm [12,15]. They feature broadband and intense absorption bands due to the 5 T2 → 5 E( 5 D) transition of Cr 2+ ions in tetrahedral (Td) sites, low saturation fluence, almost zero excitedstate absorption (ESA) [16] and acceptable laser-induced damage thresholds (LIDTs) [17]. The host materials, in their turn, provide good transparency in the near-IR and attractive thermal properties.…”