Crystal growth and optical characteristics of beryllium-free polyphosphate, KLa(PO3)4, a possible deep-ultraviolet nonlinear optical crystal

Abstract

Deep-ultraviolet nonlinear optical crystals are of great importance as key materials in generating coherent light with wavelength below 200 nm through cascaded frequency conversion of solid-state lasers. However, the solely usable crystal in practice, KBe2BO3F2 (KBBF), is still commercially unavailable because of the high toxicity of beryllium-containing and the extreme difficulty of crystal growth. Here, we report the crystal growth and characteristics of an beryllium-free polyphosphate, KLa(PO3)4. Centimeter-sized single crystals have been easily obtained by the flux method and slow-cooling technique. The second-harmonic generation efficiency of KLa(PO3)4 powder is 0.7 times that of KH2PO4; moreover, the KLa(PO3)4 crystal is phase-matchable. Remarkably, the KLa(PO3)4 crystal exhibits an absorption edge of 162 nm, which is the shortest among phase-matchable phosphates so far. These attributes make KLa(PO3)4 a possible deep-ultraviolet nonlinear optical crystal. An analysis of the dipole moments of the polyhedra and theoretical calculations by density functional theory were made to elucidate the structure-properties relationships of KLa(PO3)4.

KLaP4O12:Tb3+ Nanocrystals for Luminescent Thermometry in a Single-Band-Ratiometric Approach

“…They are associated with ν s vibrations of P−O−P groups, and they result from different positions of the lanthanum and potassium ions. 28 With an increase in the concentration of Tb 3+ ions, some slight shifts of the Raman peaks are observed (Figure S1). The positions of the two peaks around 670 and 720 cm −1 change in opposite ways; the energy of the former decreases, while that of the latter slightly increases with the dopant concentration.…”

“…Two additional intense peaks characteristic of alkali-metal lanthanide metaphosphate are visible around 670 and 720 cm –1 . They are associated with ν s vibrations of P–O–P groups, and they result from different positions of the lanthanum and potassium ions . With an increase in the concentration of Tb 3+ ions, some slight shifts of the Raman peaks are observed (Figure S1).…”

Single crystal growth, optical absorption and luminescence properties under VUV-UV synchrotron excitation of type III Pr3+:KGd(PO3)4

“…Another compound whose thermal decomposition has been studied in the literature is KLa(PO 3 ) 4 26 , which decomposes into La(PO 3 ) 3 , LaPO 4 and an amorphous phase containing phosphorus and potassium oxides. Thus, Figure 4.…”

Tellurium–oxygen group enhanced birefringence in tellurium phosphates: a first-principles investigation

“…29 Recently, phosphates have been reported to be good candidates as UV and deep-UV NLO crystal materials because of their short UV cut-off edge, 30,31 including Rb 2 Ba 3 (P 2 O 7 ) 3 (<200 nm), 32 Ba 5 P 6 O 20 (about 167 nm), 33 and KLa(PO 3 ) 4 (162 nm). 34 However, phosphates also have drawbacks. Most of the reported phosphates have a relatively small birefringence, which has relationship with the regular tetrahedron of the PO 4 units.…”