More Like this

1. Generalized analytical and numerical modeling of optical second harmonic generation in anisotropic crystals and complex heterostructures using ♯SHAARP package

   https://doi.org/10.1117/12.2676223  

   Zu, Rui ; Wang, Bo ; He, Jingyang ; Weber, Lincoln ; Wang, Jianjun ; Chen, Long-Qing ; Gopalan, Venkatraman ( October 2023 , SPIE)

   Liu, Zhiwen ; Psaltis, Demetri ; Shi, Kebin (Ed.)

   Optical Second Harmonic Generation (SHG) is a nonlinear optical effect widely used for nonlinear optical microscopy and laser frequency conversion. The closed-form analytical solution of the nonlinear optical responses is essential for evaluating the optical responses of new materials whose optical properties are unknown a priori. Many approximations have therefore been employed in the existing analytical approaches, such as slowly varying approximation, weak reflection of the nonlinear polarization, transparent medium, high crystallographic symmetry, Kleinman symmetry, easy crystal orientation along a high-symmetry direction, phase matching conditions and negligible interference among nonlinear waves, which may lead to large errors in the reported material properties. To avoid these approximations, we have developed an open-source package named Second Harmonic Analysis of Anisotropic Rotational Polarimetry (♯SHAARP) for single interface (si) and in multilayers (ml) for homogeneous crystals. The reliability and accuracy are established by experimentally benchmarking with both the SHG polarimetry and Maker fringes predicted from the package using standard materials. SHAARP.si and SHAARP.ml are available through GitHub https://github.com/Rui-Zu/SHAARP and https://github.com/bzw133/SHAARP.ml, respectively. 

   more » « less
2. Wide‐Bandgap R Ba 3 (B 3 O 6 ) 3 ( R = Nd, Sm, Tb, Dy, and Er) Single Crystals for Ultraviolet Nonlinear Optics

   https://doi.org/10.1002/adom.202401437  

   Sarker, Saugata ; Wang, Yu ; Benyacko, Caeli ; Guan, Yingdong ; Yoshida, Suguru ; Yennawar, Hemant ; He, Jingyang ; Mao, Zhiqiang ; Gopalan, Venkatraman ( August 2024 , Advanced Optical Materials)

   Discovery of new materials with enhanced optical properties in the visible and UV‐C range can impact applications in lasers, nonlinear optics, and quantum optics. Here, the optical floating zone growth of a family of rare earth borates,RBa₃(B₃O₆)₃(R= Nd, Sm, Tb, Dy, and Er), with promising linear and nonlinear optical (NLO) properties is reported. Although previously identified to be centrosymmetric, the X‐ray analysis combined with optical second harmonic generation (SHG) assigns the noncentrosymmetricPspace group to these crystals. Characterization of linear optical properties reveals a direct bandgap of ≈5.61–5.72 eV and strong photoluminescence in both the visible and mid‐IR regions. Anisotropic linear and nonlinear optical characterization reveals both Type‐I and Type‐II SHG phase matchability, with the highest effective phase‐matched SHG coefficient of 1.2 pm V⁻¹at 800‐nm fundamental wavelength (for DyBa₃(B₃O₆)₃), comparable to β‐BaB₂O₄(phase‐matchedd₂₂≈ 1.9 pm V⁻¹). Laser‐induced surface damage threshold for these environmentally stable crystals is 650–900 GW cm⁻², which is four to five times higher than that of β‐BaB₂O₄, thus providing an opportunity to pump with significantly higher power to generate about six to seven times stronger SHG light. Since the SHG arises from disorder on the Ba‐site, significantly larger SHG coefficients may be realized by “poling” the crystals to align the Ba displacements. These properties motivate further development of this crystal family for laser and wide bandgap NLO applications.

    

   more » « less
3. Prediction of Large Second Harmonic Generation in the Metal-Oxide/Organic Hybrid Compound CuMoO3(p2c)

   https://doi.org/10.3390/sym14040824  

   Yang, Tingting ; Huang, Xueli ; Cheng, Xiyue ; Maggard, Paul A. ; Whangbo, Myung-Hwan ; Luan, Chengkai ; Deng, Shuiquan ( April 2022 , Symmetry)

   Noncentrosymmetric hybrid framework (HF) materials are an important system in discovering new practical second-order nonlinear optical materials. We calculated the second harmonic generation (SHG) response of a noncentrosymmetric (NCS) organic–inorganic HF compound, CuMoO3(p2c) (p2c = pyrazine-2-carboxylate) to find that it exhibits the largest SHG response among all known NCS HF materials with one-dimensional helical chains. Further atom response theory analysis revealed that the metal atoms Cu and Mo contribute much more strongly than do nonmetal atoms in determining the strength of the SHG response, which is a novel example in nonlinear optical materials known to date. 

   more » « less
4. Photocarrier‐Induced Active Control of Second‐Order Optical Nonlinearity in Monolayer MoS 2

   https://doi.org/10.1002/smll.201906347  

   Taghinejad, Mohammad ; Xu, Zihao ; Wang, Hua ; Taghinejad, Hossein ; Lee, Kyu‐Tae ; Rodrigues, Sean P. ; Adibi, Ali ; Qian, Xiaofeng ; Lian, Tianquan ; Cai, Wenshan ( January 2020 , Small)

   Atomically thin transition metal dichalcogenides (TMDs) in their excited states can serve as exceptionally small building blocks for active optical platforms. In this scheme, optical excitation provides a practical approach to control light‐TMD interactions via the photocarrier generation, in an ultrafast manner. Here, it is demonstrated that via a controlled generation of photocarriers the second‐harmonic generation (SHG) from a monolayer MoS₂crystal can be substantially modulated up to ≈55% within a timeframe of ≈250 fs, a set of performance characteristics that showcases the promise of low‐dimensional materials for all‐optical nonlinear data processing. The combined experimental and theoretical study suggests that the large SHG modulation stems from the correlation between the second‐order dielectric susceptibility χ⁽²⁾and the density of photoexcited carriers in MoS₂. Indeed, the depopulation of the conduction band electrons, at the vicinity of the high‐symmetryK/K′points of MoS₂, suppresses the contribution of interband electronic transitions in the effective χ⁽²⁾of the monolayer crystal, enabling the all‐optical modulation of the SHG signal. The strong dependence of the second‐order optical response on the density of photocarriers reveals the promise of time‐resolved nonlinear characterization as an alternative route to monitoring carrier dynamics in excited states of TMDs.

    

   more » « less
5. Anisotropic optical responses of layered thallium arsenic sulfosalt gillulyite

   https://doi.org/10.1038/s41598-021-01542-6  

   Tripathi, Ravi P. ; Gao, Jie ; Yang, Xiaodong ( December 2021 , Scientific Reports)

   Abstract Multi-element two-dimensional (2D) materials hold great promise in the context of tailoring the physical and chemical properties of the materials via stoichiometric engineering. However, the rational and controllable synthesis of complex 2D materials remains a challenge. Herein, we demonstrate the preparation of large-area thin quaternary 2D material flakes via mechanical exfoliation from a naturally occurring bulk crystal named gillulyite. Furthermore, the anisotropic linear and nonlinear optical properties including anisotropic Raman scattering, linear dichroism, and anisotropic third-harmonic generation (THG) of the exfoliated gillulyite flakes are investigated. The observed highly anisotropic optical properties originate from the reduced in-plane crystal symmetry. Additionally, the third-order nonlinear susceptibility of gillulyite crystal is retrieved from the measured thickness-dependent THG emission. We anticipate that the demonstrated strong anisotropic linear and nonlinear optical responses of gillulyite crystal will facilitate the better understanding of light-matter interaction in quaternary 2D materials and its implications in technological innovations such as photodetectors, frequency modulators, nonlinear optical signal processors, and solar cell applications. 

   more » « less