海歸學者發起的公益學術平臺
分享資訊，整合資源
交流學術，偶爾風月
來自美國賓夕法尼亞州立大學材料科學與工程系的Venkatraman
Gopalan教授和陳龍慶教授領導的團隊提出了一個全面綜合的光學二次諧波理論框架和一個開源軟體包♯SHAARP.ml，用於模擬任意單介面（與♯SHAARP.si相同(npj Comput Mater 8, 246 (2022).)）和複雜異質結構中的二次諧波響應。♯SHAARP.ml旨在為模擬和實驗表徵提供數值計算和半解析解，從而實現對複雜材料系統的快速、精確、靈活的非線性光學響應分析以滿足使用者不同的需求。
Gopalan教授和陳龍慶教授領導的團隊提出了一個全面綜合的光學二次諧波理論框架和一個開源軟體包♯SHAARP.ml，用於模擬任意單介面（與♯SHAARP.si相同(npj Comput Mater 8, 246 (2022).)）和複雜異質結構中的二次諧波響應。♯SHAARP.ml旨在為模擬和實驗表徵提供數值計算和半解析解，從而實現對複雜材料系統的快速、精確、靈活的非線性光學響應分析以滿足使用者不同的需求。
該研究團隊所開發的♯SHAARP.ml軟體具有如下特點：
（1）能夠模擬具有均勻光學性質的任意層數的多層結構；
（2）允許模擬具有任意對稱性 (從各向同性到三斜晶系)與取向的晶體，並且每層可以具有不同的吸收、雙折射和色散；
（3）提供反射和透射解以滿足試驗設計需求；
（4）可以控制入射光的入射角和任意偏振狀態（包括線偏振、圓偏振和橢圓偏振）；
（5）明確考慮線性和非線性波的多次反射所引入的干涉；
（6）提供使用者友好的圖形介面便於建模、計算與資料後處理。
該團隊進一步使用兩種主流實驗方法驗證和測試了模型的準確性，即Maker條紋（圖2a）和二次諧波偏振測量（圖2b，c），並研究了包括α-SiO2單晶、α-SiO2及金鍍層、LiNbO3和KTP單晶、ZnO//Pt//Al2O3薄膜，LiNbO3和α-SiO2雙層，以及扭角雙層MoS2在內的七種非線性光學體系。♯SHAARP.ml在提取擬合計算二次諧波係數、數值計算預測各向異性SHG響應和Maker條紋圖案、處理吸收、干涉和多次反射方面具有極高的準確性和靈活性。圖3展示了♯SHAARP.ml軟體的圖形使用者介面，為使用者提供多樣化的、需求導向的光學二次諧波分析（左側和右側分別對應引數區和結果區）。該研究為非線性光學材料的研究提供了更具普適性的模型、更完整而準確的分析框架、以及按照不同建模假設需求的解決方案，所開發的易於上手的開源軟體可以助力不同背景科研人員對非線性光學材料進行分析與模擬。
該文近期發表於npj Computational Materials | (2024) 10:1-15，英文標題與摘要如下，點選左下角“閱讀原文”可以自由獲取論文PDF。論文第一作者是美國賓州州立大學的俎瑞博士（現為高階研究工程師就職於3M公司）和王博博士（現於美國勞倫斯利弗莫爾國家實驗室進行博士後研究）。其他合作者還包括賓州州立大學的何景陽博士，Lincoln Weber和Akash Saha。論文通訊作者為俎瑞博士、王博博士、陳龍慶教授和Venkatraman Gopalan教授。
所開發的♯SHAARP.ml開源軟體原始碼可以到以下連結下載：https://github.com/bzw133/SHAARP.ml
♯SHAARP.si開源軟體原始碼：
https://github.com/Rui-Zu/SHAARP
（原文連結：https://www.nature.com/articles/s41524-024-01229-2）
圖1 光學二次諧波產生的基本原理示意圖
圖2 利用♯SHAARP.ml軟體建模結合三種實驗方法測量SHG係數
圖3 ♯SHAARP.ml軟體的圖形使用者介面
Optical second harmonic generation in anisotropic multilayers with complete multireflection of linear and nonlinear waves using ♯SHAARP.ml package
Rui Zua, Bo Wanga, Jingyang He, Lincoln Weber, Akash Saha, Long-Qing Chen and Venkatraman Gopalan
Optical second harmonic generation (SHG) is
a nonlinear optical effect widely used for nonlinear optical microscopy and
laser frequency conversion. Closed-form analytical solution of the nonlinear
optical responses is essential for evaluating materials whose optical
properties are unknown a priori. A recent open-source code, ♯SHAARP.si,
can provide such closed form solutions for crystals with arbitrary symmetries,
orientations, and anisotropic properties at a single interface. However,
optical components are often in the form of slabs, thin films on substrates,
and multilayer heterostructures with multiple reflections of both the
fundamental and up to ten different SHG waves at each interface, adding
significant complexity. 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 in
Multilayers (♯SHAARP.ml). The reliability and accuracy are established
by experimentally benchmarking with both the SHG polarimetry and Maker fringes
using standard and commonly used nonlinear optical materials as well as twisted
2-dimensional heterostructures.
a nonlinear optical effect widely used for nonlinear optical microscopy and
laser frequency conversion. Closed-form analytical solution of the nonlinear
optical responses is essential for evaluating materials whose optical
properties are unknown a priori. A recent open-source code, ♯SHAARP.si,
can provide such closed form solutions for crystals with arbitrary symmetries,
orientations, and anisotropic properties at a single interface. However,
optical components are often in the form of slabs, thin films on substrates,
and multilayer heterostructures with multiple reflections of both the
fundamental and up to ten different SHG waves at each interface, adding
significant complexity. 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 in
Multilayers (♯SHAARP.ml). The reliability and accuracy are established
by experimentally benchmarking with both the SHG polarimetry and Maker fringes
using standard and commonly used nonlinear optical materials as well as twisted
2-dimensional heterostructures.
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非線性光學
Npj Comput.Mater
二次諧波