摘要
双波段窄带热辐射器在红外传感、加密、检测等众多领域具有重要的应用潜力。这种辐射器能够提供集中且精确的红外辐射能量,从而提高红外技术的灵敏度和分辨率。不过,在不同波段构建窄带辐射的条件通常会相互制约,同时实现双波段窄带热辐射仍具有一定的挑战性。本文提出了一种新型无需光刻的红外双波段窄带热辐射器。该辐射器由铝薄膜上非周期性的交替沉积Ge和YbF3薄膜组成,Ge和YbF3薄膜组成的分布式布拉格反射镜和铝基底在一定条件下可以激发Tamm等离激元(Tamm Plasmon Polaritons,TPPs),从而实现窄带辐射。首先使用多目标粒子群优化算法对辐射器的结构参数进行优化,以满足双波段TPP的激发条件。实验结果也验证了双波段辐射器在中波红外和长波红外波段具有窄带辐射的特性。本文提出的方法也可用于多波段辐射调控器件的设计,从而可以应用于多气体传感和多带红外伪装等领域。
红外波段窄带热辐射器件因其在大气科学、军事和能源工程方面的广阔应用前景而受到广泛关注。近年来,研究人员利用纳米光学结构的强电磁场操控能力精确调控红外波段的辐射行为,从而形成窄带辐射。如Rinnerbauer等使用多晶钽为基底制备的二维光子晶体在2 μm实现窄带辐
基于表面共振态的平面多层结构可以在不增加复杂度的情况下进行大面积制造。例如,法布里-珀罗结构已被证明可用作波长选择性辐射
此外,可以通过在平面多层结构中激发多个TPP来实现多波段窄带辐射。多波段辐射的优势在于可以与探测目标的多个吸收峰对齐,从而提高探测的灵敏度。同时,可以在单个器件上实现多种功能,从而简化器件架构并减少器件功
通过在200 nm铝基底上交替生长的Ge和YbF3层来构建双波段热辐射器。在双波段热辐射器的设计过程中,两个波段的相位匹配条件会相互冲突,这增加了寻找解的难度。因此,采用多目标粒子群优化法(Multi-Objective Particle Swarm Optimization,MOPSO)和转移矩阵法(Transfer-Matrix Method,TMM)相结合的逆向设计方法来优化每层薄膜的厚度。多目标粒子群算法是一种用于解决多目标优化问题的算法,它能同时处理多个优化目标,寻找在所有目标间取得平衡的解集,从而提供一组可行的
, |
其中,是目标辐射峰峰值;是辐射波长,Q是共振峰品质因子。通过将热辐射器的辐射光谱与目标光谱进行对比,得到了每个粒子的适应度函数值:。在对每个热辐射器进行评估之后,将单个热辐射器的非支配解记录为个人最佳位置,即Pbest。之后,在这些非支配解的集合中,使用轮盘赌的方式选出全局最佳位置Gbest。然后,根据个人最佳位置和全局最佳位置来更新每个粒子的速度和位置。这样,就完成了一次粒子的迭代搜索的过程。当达到预设的最大迭代次数,或者全局最佳位置的适应度函数值达到要求时,将终止算法的执行。

图1 基于MOPSO的双波段窄带热辐射器的流程图
Fig.1 Schematic of MOPSO-based dual-band narrowband thermal emitter

图2 使用MOPSO针对长波红外和中波红外波段优化得到的解集
Fig.2 Solution set obtained using MOPSO for LWIR and MWIR band

图3 最优解集合中热辐射器的几何参数及辐射光谱:(a) 优化的双波段热辐射器示意图;(b) A点对应的热辐射器的辐射光谱;(c) B点对应的热辐射器的辐射光谱;(d) C点对应的热辐射器的辐射光谱
Fig.3 Geometrical parameters and emission spectrum of thermal emitters in the set of optimal solutions:(a) schematic of the optimized dual-band emitter; (b) emission spectrum of thermal emitter at point A; (c) emission spectrum of thermal emitter at point B; (d) emission spectrum of thermal emitter at point C
为了探究双波段窄带热辐射器的性质,采用时域有限差分方法对其电磁场分布进行了数值模拟研究。

图4 双波段热辐射器的电磁场分布和时间平均功率耗散密度:波长为4 μm的平面波正入射时的(a) 归一化电场强度、(b) 归一化磁场强度和(c) 时间平均功率耗散密度;波长为8.2 μm的平面波正入射时的(d) 归一化电场强度、(e) 归一化磁场强度和(f) 时间平均功率耗散密度
Fig.4 Electromagnetic field distributions and time-averaged power dissipation density of the dual-band thermal emitter:(a)simulated normalized electric field intensity, (b) simulated normalized magnetic field intensity and (c)time-averaged power dissipation density at 4 μm plane wave normal incidence; (d)simulated normalized electric field intensity, (e) simulated normalized magnetic field intensity and (f)time-averaged power dissipation density at 8.2 μm plane wave normal incidence
为了在实验中证明上述结果,本文利用电子束蒸发设备制备了近2 cm × 2 cm大小的Al/Ge/YbF3结构的薄膜,样品如

图5 双波段窄带热辐射器的实验表征:(a) 制备好的样品扫描电子显微镜(SEM)图像(插图中为样品光学图像);(b) 30°入辐射角下的双波段热辐射器样品的理论和实验辐射率光谱;(c) 样品在50~150 ℃温度下测得的法线方向辐射强度光谱;(d) 样品在4个温度下测得的辐射率光谱
Fig.5 Experimental characterization of the dual-band narrowband thermal emitter:(a) SEM image of part of prepared samples (an optical image of the sample is shown in the inset); (b) the theoretical and experimental emissivity spectra of the dual-band thermal emitter samples at 30° incident angle; (c) the measured radiation intensity spectra in the normal direction for 50—150 ℃; (d) the measured emissivity spectra at four different temperatures
本文提出并通过实验证明了一种无需光刻的大面积双波段窄带热辐射器。该热辐射器主要包括由Ge和YbF3薄膜组成的DBR结构与铝金属基底组成。通过使用MOPSO并结合TMM对其中DBR结构的几何参数进行了优化,得到了可以同时在4.0 μm和8.2 μm处实现高品质因子的双波段热辐射器。使用时域有限差分方法分析了这两个峰值处的电磁场分布及时间平均功率耗散密度,发现电磁场主要局域在结构底部,电磁场能量主要被底部金属耗散,证明双波段窄带热辐射器的窄带辐射特性均源于Tamm等离激元共振。利用电子束蒸发镀膜设备成功制备了双波段热辐射器。使用傅里叶变换红外光谱仪在室温下测量了样品在30°入射角下的s偏振光的反射率和透射率,并据此计算得到了双波段热辐射器的辐射光谱。将其与使用时域有限差分方法在相同条件下得到的辐射光谱进行对比,发现二者具有一致性,其中的微小差异可能主要是由于制作的样品不完善造成的。使用电加热板加热样品,然后通过傅里叶变换红外光谱仪测量得到了其在50~150 ℃(10 ℃为间隔)下的辐射强度光谱,并观察到了其在长波红外8.2 μm处的窄带辐射峰。最后,测量了相同温度下黑体的辐射强度谱线,通过计算得到了样品在120~150 ℃(10 ℃为间隔)的辐射率谱线,并成功观察到其双波段(4.0 μm和8.2 μm)窄带辐射特性。
References
Rinnerbauer V, Yeng Y X, Chan W R, et al. High-temperature stability and selective thermal emission of polycrystalline tantalum photonic crystals[J]. Optics Express, 2013, 21(9): 11482. [百度学术]
Chan W R, Bermel P, Pilawa-Podgurski R C N, et al. Toward high-energy-density, high-efficiency, and moderate-temperature chip-scale thermophotovoltaics[J]. Proceedings of the National Academy of Sciences, 2013, 110(14): 5309-5314. [百度学术]
Chan D L C, Soljačić M, Joannopoulos J D. Thermal emission and design in 2D-periodic metallic photonic crystal slabs[J]. Optics Express, 2006, 14(19): 8785. [百度学术]
Pralle M U, Moelders N, McNeal M P, et al. Photonic crystal enhanced narrow-band infrared emitters[J]. Applied Physics Letters, 2002, 81(25): 4685-4687. [百度学术]
Ikeda K, Miyazaki H T, Kasaya T, et al. Controlled thermal emission of polarized infrared waves from arrayed plasmon nanocavities[J]. Applied Physics Letters, 2008, 92(2): 021117. [百度学术]
Miyazaki H T, Ikeda K, Kasaya T, et al. Thermal emission of two-color polarized infrared waves from integrated plasmon cavities[J]. Applied Physics Letters, 2008, 92(14): 141114. [百度学术]
Biener G, Dahan N, Niv A, et al. Highly coherent thermal emission obtained by plasmonic bandgap structures[J]. Applied Physics Letters, 2008, 92(8): 081913. [百度学术]
Liu X, Tyler T, Starr T, et al. Taming the blackbody with infrared metamaterials as selective thermal emitters[J]. Physical Review Letters, 2011, 107(4): 045901. [百度学术]
Mason J A, Smith S, Wasserman D. Strong absorption and selective thermal emission from a midinfrared metamaterial[J]. Applied Physics Letters, 2011, 98(24): 241105. [百度学术]
Molesky S, Dewalt C J, Jacob Z. High temperature epsilon-near-zero and epsilon-near-pole metamaterial emitters for thermophotovoltaics[J]. Optics Express, 2012, 21(S1): A96-A110. [百度学术]
Wang Z, Luk T S, Tan Y, et al. Tunneling-enabled spectrally selective thermal emitter based on flat metallic films[J]. Applied Physics Letters, 2015, 106(10): 101104. [百度学术]
Wang L P, Basu S, Zhang Z M. Direct measurement of thermal emission from a fabry-perot cavity resonator[J]. Journal of Heat Transfer, 2012, 134(7): 072701. [百度学术]
Liu X, Li Z, Wen Z, et al. Large-area, lithography-free, narrow-band and highly directional thermal emitter[J]. Nanoscale, 2019, 11(42): 19742-19750. [百度学术]
Wang Z, Clark J K, Ho Y L, et al. Ultranarrow and wavelength-tunable thermal emission in a hybrid metal-optical Tamm state structure[J]. ACS Photonics, 2020, 7(6): 1569-1576. [百度学术]
Wu H, Gao Y, Xu P, et al. Plasmonic nanolasers: pursuing extreme lasing conditions on nanoscale[J]. Advanced Optical Materials, 2019, 7(17): 1900334. [百度学术]
Symonds C, Lheureux G, Hugonin J P, et al. Confined tamm plasmon lasers[J]. Nano Letters, 2013, 13(7): 3179-3184. [百度学术]
Ma R M, Oulton R F. Applications of nanolasers[J]. Nature Nanotechnology, 2019, 14(1): 12-22. [百度学术]
Lochbaum A, Fedoryshyn Y, Dorodnyy A, et al. On-chip narrowband thermal emitter for mid-IR optical gas sensing[J]. ACS Photonics, 2017, 4(6): 1371-1380. [百度学术]
Vlk M, Datta A, Alberti S, et al. Extraordinary evanescent field confinement waveguide sensor for mid-infrared trace gas spectroscopy[J]. Light: Science & Applications, 2021, 10(1): 26. [百度学术]
Lochbaum A, Dorodnyy A, Koch U, et al. Compact mid-infrared gas sensing enabled by an all-metamaterial design[J]. Nano Letters, 2020, 20(6): 4169-4176. [百度学术]
Zhang C, Wu K, Zhan Y, et al. Planar microcavity-integrated hot-electron photodetector[J]. Nanoscale, 2016, 8(19): 10323-10329. [百度学术]
He M, Nolen J R, Nordlander J, et al. Deterministic inverse design of Tamm plasmon thermal emitters with multi-resonant control[J]. Nature Materials, 2021, 20(12): 1663-1669. [百度学术]
Hassan A K S O, Etman A S, Soliman E A. Optimization of a novel nano antenna with two radiation modes using kriging surrogate models[J]. IEEE Photonics Journal, 2018, 10(4): 1-17. [百度学术]
Nagar J, Campbell S D, Ren Q, et al. Multiobjective optimization-aided metamaterials-by-design with application to highly directive nanodevices[J]. IEEE Journal on Multiscale and Multiphysics Computational Techniques, 2017, 2: 147-158. [百度学术]
Wiecha P R, Arbouet A, Girard C, et al. Evolutionary multi-objective optimisation of colour pixels based on dielectric nano-antennas[J]. Nature Nanotechnology, 2017, 12(2): 163-169. [百度学术]