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Topological insulator laser: Experiments
Science ( IF 44.7 ) Pub Date : 2018-02-01 , DOI: 10.1126/science.aar4005 Miguel A. Bandres 1 , Steffen Wittek 2 , Gal Harari 1 , Midya Parto 2 , Jinhan Ren 2 , Mordechai Segev 1 , Demetrios N. Christodoulides 2 , Mercedeh Khajavikhan 2
Science ( IF 44.7 ) Pub Date : 2018-02-01 , DOI: 10.1126/science.aar4005 Miguel A. Bandres 1 , Steffen Wittek 2 , Gal Harari 1 , Midya Parto 2 , Jinhan Ren 2 , Mordechai Segev 1 , Demetrios N. Christodoulides 2 , Mercedeh Khajavikhan 2
Affiliation
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Topological protection for lasers Ideas based on topology, initially developed in mathematics to describe the properties of geometric space under deformations, are now finding application in materials, electronics, and optics. The main driver is topological protection, a property that provides stability to a system even in the presence of defects. Harari et al. outline a theoretical proposal that carries such ideas over to geometrically designed laser cavities. The lasing mode is confined to the topological edge state of the cavity structure. Bandres et al. implemented those ideas to fabricate a topological insulator laser with an array of ring resonators. The results demonstrate a powerful platform for developing new laser systems. Science, this issue p. eaar4003, p. eaar4005 Lasing is observed in an edge mode of a designed optical topological insulator. INTRODUCTION Physical systems that exhibit topological invariants are naturally endowed with robustness against perturbations, as was recently demonstrated in many settings in condensed matter, photonics, cold atoms, acoustics, and more. The most prominent manifestations of topological systems are topological insulators, which exhibit scatter-free edge-state transport, immune to perturbations and disorder. Recent years have witnessed intense efforts toward exploiting these physical phenomena in the optical domain, with new ideas ranging from topology-driven unidirectional devices to topological protection of path entanglement. But perhaps more technologically relevant than all topological photonic settings studied thus far is, as proposed by the accompanying theoretical paper by Harari et al., an all-dielectric magnet-free topological insulator laser, with desirable properties stemming from the topological transport of light in the laser cavity. RATIONALE We demonstrate nonmagnetic topological insulator lasers. The topological properties of the laser system give rise to single-mode lasing, robustness against fabrication defects, and notably higher slope efficiencies compared to those of the topologically trivial counterparts. We further exploit the properties of the active topological platform by assembling topological insulator lasers from S-chiral microresonators that enforce predetermined unidirectional lasing even in the absence of magnetic fields. RESULTS Our topological insulator laser system is an aperiodic array of 10 unit cell–by–10 unit cell coupled ring resonators on an InGaAsP quantum wells platform. The active lattice uses the topological architecture suggested in the accompanying theoretical paper. This two-dimensional setting is composed of a square lattice of ring resonators coupled to each other by means of link rings. The intermediary links are judiciously spatially shifted to introduce a set of hopping phases, establishing a synthetic magnetic field and two topological band gaps. The gain in this laser system is provided by optical pumping. To promote lasing of the topologically protected edge modes, we pump the outer perimeter of the array while leaving the interior lossy. We find that this topological insulator laser operates in single mode even considerably above threshold, whereas the corresponding topologically trivial realizations lase in multiple modes. Moreover, the topological laser displays a slope efficiency that is considerably higher than that in the corresponding trivial realizations. We further demonstrate the topological features of this laser by observing that in the topological array, all sites emit coherently at the same wavelength, whereas in the trivial array, lasing occurs in localized regions, each at a different frequency. Also, by pumping only part of the topological array, we demonstrate that the topological edge mode always travels along the perimeter and emits light through the output coupler. By contrast, when we pump the trivial array far from the output coupler, no light is extracted from the coupler because the lasing occurs at stationary modes. We also observe that, even in the presence of defects, the topological protection always leads to more efficient lasing compared to that of the trivial counterpart. Finally, to show the potential of this active system, we assemble a topological system based on S-chiral resonators, which can provide new avenues to control the topological features. CONCLUSION We have experimentally demonstrated an all-dielectric topological insulator laser and found that the topological features enhance the lasing performance of a two-dimensional array of microresonators, making them lase in unison in an extended topologically protected scatter-free edge mode. The observed single longitudinal-mode operation leads to a considerably higher slope efficiency as compared to that of a corresponding topologically trivial system. Our results pave the way toward a new class of active topological photonic devices, such as laser arrays, that can operate in a coherent fashion with high efficiencies. Topological insulator laser. (A) Top-view image of the lasing pattern (topological edge mode) in a 10 unit cell–by–10 unit cell array of topologically coupled resonators and the output ports. (B) Output intensity versus pump intensity for a topological insulator laser and its trivial counterpart. The enhancement of the slope efficiency is about threefold. Comparing the power emitted in the single mode of the topological array to that of the highest power mode in the trivial array, the topological outperforms the trivial by more than a factor of 10. (C) Emission spectra from a topological insulator laser and its topologically trivial counterpart. au, arbitrary units. Physical systems exhibiting topological invariants are naturally endowed with robustness against perturbations, as manifested in topological insulators—materials exhibiting robust electron transport, immune from scattering by defects and disorder. Recent years have witnessed intense efforts toward exploiting these phenomena in photonics. Here we demonstrate a nonmagnetic topological insulator laser system exhibiting topologically protected transport in the cavity. Its topological properties give rise to single-mode lasing, robustness against defects, and considerably higher slope efficiencies compared to the topologically trivial counterparts. We further exploit the properties of active topological platforms by assembling the system from S-chiral microresonators, enforcing predetermined unidirectional lasing without magnetic fields. This work paves the way toward active topological devices with exciting properties and functionalities.
中文翻译：
拓扑绝缘体激光器：实验
激光器的拓扑保护基于拓扑的思想最初是在数学中发展起来的，用于描述变形下几何空间的特性，现在在材料、电子和光学中得到应用。主要驱动因素是拓扑保护，这种特性即使在存在缺陷的情况下也能为系统提供稳定性。哈拉里等人。概述了将这些想法应用于几何设计的激光腔的理论建议。激光模式仅限于腔结构的拓扑边缘状态。班德雷斯等人。实施这些想法来制造具有环形谐振器阵列的拓扑绝缘体激光器。结果证明了开发新激光系统的强大平台。科学，这个问题 p。eaar4003，第。在设计的光学拓扑绝缘体的边缘模式中观察到 eaar4005 激光。介绍 表现出拓扑不变量的物理系统天生具有抗扰动的鲁棒性，正如最近在凝聚态物质、光子学、冷原子、声学等的许多设置中所证明的那样。拓扑系统最突出的表现是拓扑绝缘体，它表现出无散射的边缘状态传输，不受扰动和无序的影响。近年来见证了在光领域利用这些物理现象的巨大努力，新想法从拓扑驱动的单向器件到路径纠缠的拓扑保护。但也许比迄今为止研究的所有拓扑光子设置在技术上更相关的是，正如 Harari 等人随附的理论论文所提出的那样，一种全介电无磁拓扑绝缘体激光器，其具有来自激光腔中光的拓扑传输的理想特性。基本原理我们展示了非磁性拓扑绝缘体激光器。与拓扑无关紧要的对应物相比，激光系统的拓扑特性产生了单模激光、对制造缺陷的鲁棒性以及显着更高的斜率效率。我们通过组装来自 S 手性微谐振器的拓扑绝缘体激光器，即使在没有磁场的情况下也能强制执行预定的单向激光，从而进一步利用有源拓扑平台的特性。结果我们的拓扑绝缘体激光系统是一个非周期性阵列，由 10 个单位×10 个单位单元耦合环形谐振器组成，位于 InGaAsP 量子阱平台上。有源晶格使用随附的理论论文中建议的拓扑结构。这种二维设置由通过连接环相互耦合的环形谐振器的方形格子组成。中间链接明智地在空间上移动以引入一组跳跃相位，建立合成磁场和两个拓扑带隙。该激光系统的增益由光泵浦提供。为了促进受拓扑保护的边缘模式的激光发射，我们泵浦阵列的外周，同时使内部有损。我们发现这种拓扑绝缘体激光器以单模运行，甚至远高于阈值，而相应的拓扑微不足道的实现在多种模式下。此外，拓扑激光器显示的斜率效率远高于相应的琐碎实现中的斜率效率。我们通过观察拓扑阵列中的所有位点以相同的波长相干发射，进一步证明了该激光器的拓扑特征，而在普通阵列中，激光发生在局部区域，每个区域的频率不同。此外，通过仅泵浦拓扑阵列的一部分，我们证明了拓扑边缘模式总是沿着周边传播并通过输出耦合器发射光。相比之下，当我们将微阵列泵浦远离输出耦合器时，没有光从耦合器中提取出来，因为激光发生在固定模式下。我们还观察到，即使存在缺陷，与普通对应物相比，拓扑保护总是会导致更有效的激光发射。最后，为了展示这个有源系统的潜力，我们组装了一个基于 S 手性谐振器的拓扑系统，它可以提供控制拓扑特征的新途径。结论我们已经通过实验证明了全介电拓扑绝缘体激光器，并发现拓扑特征增强了二维微谐振器阵列的激光性能，使它们以扩展的拓扑保护无散射边缘模式一致地发射。与相应的拓扑微不足道系统相比，观察到的单纵模操作导致显着更高的斜率效率。我们的结果为开发一类新的有源拓扑光子器件（例如激光阵列）铺平了道路，这些器件可以以相干方式高效运行。拓扑绝缘体激光器。(A) 拓扑耦合谐振器和输出端口的 10 个单位单元×10 个单位单元阵列中激光图案（拓扑边缘模式）的俯视图。(B) 拓扑绝缘体激光器及其普通对应物的输出强度与泵浦强度的关系。斜坡效率的提高大约是三倍。将拓扑阵列的单模发射功率与普通阵列中最高功率模式的发射功率进行比较，拓扑优于普通阵列的 10 倍以上。 (C) 拓扑绝缘体激光器及其拓扑结构的发射光谱琐碎的对应物。au，任意单位。表现出拓扑不变量的物理系统天生就具有抗扰动的鲁棒性，正如拓扑绝缘体所体现的那样——材料表现出强大的电子传输，不受缺陷和无序散射的影响。近年来，人们为在光子学中利用这些现象做出了巨大的努力。在这里，我们展示了一种非磁性拓扑绝缘体激光系统，该系统在腔中表现出拓扑保护的传输。与拓扑无关紧要的对应物相比，它的拓扑特性产生了单模激光、对缺陷的鲁棒性以及显着更高的斜率效率。我们通过从 S 手性微谐振器组装系统，在没有磁场的情况下执行预定的单向激光，进一步利用有源拓扑平台的特性。
更新日期：2018-02-01
中文翻译：
拓扑绝缘体激光器：实验
激光器的拓扑保护基于拓扑的思想最初是在数学中发展起来的，用于描述变形下几何空间的特性，现在在材料、电子和光学中得到应用。主要驱动因素是拓扑保护，这种特性即使在存在缺陷的情况下也能为系统提供稳定性。哈拉里等人。概述了将这些想法应用于几何设计的激光腔的理论建议。激光模式仅限于腔结构的拓扑边缘状态。班德雷斯等人。实施这些想法来制造具有环形谐振器阵列的拓扑绝缘体激光器。结果证明了开发新激光系统的强大平台。科学，这个问题 p。eaar4003，第。在设计的光学拓扑绝缘体的边缘模式中观察到 eaar4005 激光。介绍 表现出拓扑不变量的物理系统天生具有抗扰动的鲁棒性，正如最近在凝聚态物质、光子学、冷原子、声学等的许多设置中所证明的那样。拓扑系统最突出的表现是拓扑绝缘体，它表现出无散射的边缘状态传输，不受扰动和无序的影响。近年来见证了在光领域利用这些物理现象的巨大努力，新想法从拓扑驱动的单向器件到路径纠缠的拓扑保护。但也许比迄今为止研究的所有拓扑光子设置在技术上更相关的是，正如 Harari 等人随附的理论论文所提出的那样，一种全介电无磁拓扑绝缘体激光器，其具有来自激光腔中光的拓扑传输的理想特性。基本原理我们展示了非磁性拓扑绝缘体激光器。与拓扑无关紧要的对应物相比，激光系统的拓扑特性产生了单模激光、对制造缺陷的鲁棒性以及显着更高的斜率效率。我们通过组装来自 S 手性微谐振器的拓扑绝缘体激光器，即使在没有磁场的情况下也能强制执行预定的单向激光，从而进一步利用有源拓扑平台的特性。结果我们的拓扑绝缘体激光系统是一个非周期性阵列，由 10 个单位×10 个单位单元耦合环形谐振器组成，位于 InGaAsP 量子阱平台上。有源晶格使用随附的理论论文中建议的拓扑结构。这种二维设置由通过连接环相互耦合的环形谐振器的方形格子组成。中间链接明智地在空间上移动以引入一组跳跃相位，建立合成磁场和两个拓扑带隙。该激光系统的增益由光泵浦提供。为了促进受拓扑保护的边缘模式的激光发射，我们泵浦阵列的外周，同时使内部有损。我们发现这种拓扑绝缘体激光器以单模运行，甚至远高于阈值，而相应的拓扑微不足道的实现在多种模式下。此外，拓扑激光器显示的斜率效率远高于相应的琐碎实现中的斜率效率。我们通过观察拓扑阵列中的所有位点以相同的波长相干发射，进一步证明了该激光器的拓扑特征，而在普通阵列中，激光发生在局部区域，每个区域的频率不同。此外，通过仅泵浦拓扑阵列的一部分，我们证明了拓扑边缘模式总是沿着周边传播并通过输出耦合器发射光。相比之下，当我们将微阵列泵浦远离输出耦合器时，没有光从耦合器中提取出来，因为激光发生在固定模式下。我们还观察到，即使存在缺陷，与普通对应物相比，拓扑保护总是会导致更有效的激光发射。最后，为了展示这个有源系统的潜力，我们组装了一个基于 S 手性谐振器的拓扑系统，它可以提供控制拓扑特征的新途径。结论我们已经通过实验证明了全介电拓扑绝缘体激光器，并发现拓扑特征增强了二维微谐振器阵列的激光性能，使它们以扩展的拓扑保护无散射边缘模式一致地发射。与相应的拓扑微不足道系统相比，观察到的单纵模操作导致显着更高的斜率效率。我们的结果为开发一类新的有源拓扑光子器件（例如激光阵列）铺平了道路，这些器件可以以相干方式高效运行。拓扑绝缘体激光器。(A) 拓扑耦合谐振器和输出端口的 10 个单位单元×10 个单位单元阵列中激光图案（拓扑边缘模式）的俯视图。(B) 拓扑绝缘体激光器及其普通对应物的输出强度与泵浦强度的关系。斜坡效率的提高大约是三倍。将拓扑阵列的单模发射功率与普通阵列中最高功率模式的发射功率进行比较，拓扑优于普通阵列的 10 倍以上。 (C) 拓扑绝缘体激光器及其拓扑结构的发射光谱琐碎的对应物。au，任意单位。表现出拓扑不变量的物理系统天生就具有抗扰动的鲁棒性，正如拓扑绝缘体所体现的那样——材料表现出强大的电子传输，不受缺陷和无序散射的影响。近年来，人们为在光子学中利用这些现象做出了巨大的努力。在这里，我们展示了一种非磁性拓扑绝缘体激光系统，该系统在腔中表现出拓扑保护的传输。与拓扑无关紧要的对应物相比，它的拓扑特性产生了单模激光、对缺陷的鲁棒性以及显着更高的斜率效率。我们通过从 S 手性微谐振器组装系统，在没有磁场的情况下执行预定的单向激光，进一步利用有源拓扑平台的特性。
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