Research
  Key Laboratories
  Research Divisions
  Research Interests
  Supporting System
  Achievements
  Research Progress
  Research Programs
  Technology Transfer
    Location: Home > Research > Research Progress

Researchers Design First Lead/Tin Fluorooxoborates with Widely Divergent Second Harmonic Generation Effects

 

Nonlinear optical (NLO) materials have attracted extensive attention because they can produce coherent light via frequency conversion in all-solid-state lasers. However, due to the increasing demand for high-performance crystal, the search for new NLO crystals with large macroscopic second harmonic generation (SHG) effects and wide transparencies has never ceased.

In a study published in Journal of the American Chemical Society, the research group led by Prof. YE Ning at Fujian Institute of Research on the Structure of Matter (FJIRSM) of Chinese Academy of Sciences reported the first lead/tin , which were rationally designed by employing the nonlinear optical crystal Sr2Be2B2O7 (SBBO) as a parent model (Figure 1). Compared with the rigid [Be6B6O15] double layers in SBBO, MB2O3F2 have flexible two-dimensional [B6O12F6] single layer, which not only keeps the NLO-favorable layered structure but also overcomes the structural instability issues of SBBO.

UV/vis/NIR diffuse-reflectance spectra showed PbB2O3F2 and SnB2O3F2 exhibited relatively short UV absorption edges of 220 and 250 nm, respectively, which are far shorter than those of recently reported materials containing NLO-active structural units, such as Pb3Mg3TeP2O14 (250 nm), Pb2(NO3)2(H2O)F2 (300 nm), Pb2BO3I (330 nm), Bi3TeBO9 (385 nm) and K3[V(O2)2O]CO3 (420 nm).

Interestingly, the researchers found that these two fluorooxoborates showed widely divergent second harmonic responses (13×KDP and 4×KDP, respectively for PbB2O3F2 and SnB2O3F2), although they are isostructural and both contain stereochemically active lone-pair cations.

Further theoretical investigations revealed that the SHG difference is mainly attributed to the different anisotropies of Pb and Sn SHG-active orbitals (Figure 2), which make constructively and destructively contribution to the SHG effects in PbB2O3F2 and SnB2O3F2, respectively.

The study not only exhibited two promising UV NLO materials but also revealed an undiscovered mechanism for the contribution of stereochemically active lone-pair (SCALP) cations to hyperpolarizability.

 

 

Figure 1 Structural evolution from SBBO to PBOF.(Image by Prof. YE’s Group)

 

 

Figure 2 Electronic charge density maps from the orbitals near the band gaps in PBOF and SBOF. (a) and (b) from the top of VB (-0.5 eV – 0 eV), (c) and (d) from the bottom of CB (5eV – 7 eV), and (e) and (f) from their superposition in PBOF and SBOF, respectively. (Image by Prof. YE’s Group)

 

Contact:

Prof. YE Ning

Fujian Institute of Research on the Structure of Matter

Chinese Academy of Sciences

Email: nye@fjirsm.ac.cn 

 

 

 


Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences
Address: 155 Yangqiao Road West,Fuzhou,350002,P.R.China Tel: 0591-83714517 Fax: 0591-83714946 E-mail: fjirsm@fjirsm.ac.cn
Copyright @ 2000-2009 fjirsm. All rights reserved.