Growth and Properties of LiGaX₂ (X: S, Se, Te) Single Crystals for Nonlinear Optical Applications in the Mid‐IR.

Abstract

Optical Applications in the Mid-IR. -Single crystals of the title compounds are synthesized from the elements using the Bridgman-Stockbarger technique and characterized by UV/VIS and Raman spectroscopy. LiGaS2 and LiGaSe2 crystallize in the orthorhombic space group Pna21 with Z = 4 and LiGaTe2 in the tetragonal space group I42d with Z = 16 (single crystal and powder XRD). Refractive indices for LiGaS 2 and LiGaSe 2 are measured over the whole transparency range. Sellmeier equations are fitted and phase-matching conditions for second harmonic generation are calculated. The 1.467-11.72 µm spectral range for the fundamental is covered by LiGaS2 and LiGaSe2. -(ISAENKO, L.; YELISSEYEV*, A.; LOBANOV, S.; TITOV, A.; PETROV, V.; ZONDY, J.-J.; KRINITSIN, P.; MERKULOV, A.; VEDENYAPIN, V.; SMIRNOVA, J.; Cryst.

Terahertz emission from lithium ternary chalcopyrite crystals

“…On the other hand, high group refractive indices at shorter wavelength than 800 nm are given by using the reported Sellmeier parameters. 3 We may find the velocity-matching on lithium ternary compounds and strong THz generation by illumination of shorter wavelength laser.…”

“…Furthermore, it is known that lithium ternary compound crystals have Raman active vibration modes in the THz frequency range from Raman spectroscopy. 3 For this reason, narrow-band THz emission by laser illumination can be expected. We report here the observation of THz coherent generation from lithium ternary chalcopyrite crystals illuminated by 800 and 1560 nm femtosecond laser pulses and the optical properties of these crystals at THz frequency, and we discuss the mechanism of the emission.…”

A novel solid solution LiGa(S1–x Se x )2 for generating coherent ultrafast mid-IR sources

“…LGSe have an orthorhombic structure with a Pna2 1 space group and an mm2 point group, and are isostructural to LiInS 2 (LIS) and LiInSe 2 (LISe) crystals. The transparency ranges of LGS and LGSe are 0.32-11.6 μm and 0.37-13.2 μm at 5 cm −1 [1], respectively. Their bandgap energies-4.15 eV (299 nm) for LGS and 3.43 eV (371 nm) for LGSe [2], respectively-definitely exclude twophoton absorption for a typical 800 nm pump.…”

“…The ternary chalcogenides LiGaS 2 (LGS) and LiGaSe 2 (LGSe), as nonlinear crystals, are transparent from the UVvisible to the mid-IR spectral range, and can thus be pumped by visible and all solid state near-IR lasers [1]. Since the beginning of the new century, this has attracted the attention of many researchers [2][3][4][5][6][7][8][9].…”

“…In a different way, Seidel et al adopted an OPA scheme to generate 8.5 μm pulses using longer LGS crystals [14], which produced an efficiency 25 times higher than that in a former Laser Physics Letters A novel solid solution LiGa(S 1-x Se x ) 2 for generating coherent ultrafast mid-IR sources work of Pupeza et al [12]. Isomorph LGSe has similar optical properties to LGS-but with a lower damage threshold and higher nonlinearity [1]-and it has been employed in an optical parametric oscillation (OPO) setup to generate mid-IR light, showing a threshold that is three times lower due to its higher nonlinearity and larger size [6]. Since the late 1970s, a number of solid solutions of nonlinear isomorphic IR crystals have been synthesized as potential alternatives to the parent crystals.…”