Photonic integrated circuits (PICs) are vital for high-speed data transmission. However, optical routing is limited in PICs composed of only one or a few stacked planes. Further, coupling losses must be low in deployed systems. Previously, we developed the subsurface controllable refractive index via beam exposure (SCRIBE) technique to write accurate 3D gradient refractive index (GRIN) profiles within a mesoporous silica scaffold. Here, we apply SCRIBE to fabricate low loss, broadband, polarization insensitive, fiber-coupled, single-mode volumetric interconnects that include waveguides traversing arbitrary 3D paths. By seamlessly integrating mode-matching subsurface lenses and GRIN waveguide tapers, calibrating for positional writing errors, implementing multipass exposure, automating alignment, and switching to antireflection coated fibers, we reduced the insertion loss for a fiber-PIC-fiber interconnect from 50 to 2.14 dB, or 1.47 dB, excluding the fiber array’s loss. Further, we establish an upper bound of 0.45 dB loss per coupler. We report quality factors of 27,000 and 77,000 and bending losses of 6 and 3 dB/cm for 15 and 30 µm radii microrings, respectively. We also demonstrate Bézier escalators, polarization-rotating and polarization-splitting interconnects, and a seven-channel 25 µm pitch volumetric interconnect. The SCRIBE platform presents a clear path toward realizing 3D PICs with unique functionality.

中文翻译：

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通过直接激光写入制造的低损耗光纤耦合体积互连


光子集成电路（PIC）对于高速数据传输至关重要。然而，光路由在仅由一个或几个堆叠平面组成的 PIC 中受到限制。此外，已部署系统中的耦合损耗必须较低。此前，我们开发了通过光束曝光控制次表面折射率 (SCRIBE) 技术，可在介孔二氧化硅支架内写入精确的 3D 梯度折射率 (GRIN) 剖面。在这里，我们应用 SCRIBE 来制造低损耗、宽带、偏振不敏感、光纤耦合、单模体积互连，其中包括穿过任意 3D 路径的波导。通过无缝集成模式匹配次表面透镜和 GRIN 波导锥度、校准位置写入误差、实施多遍曝光、自动对准以及切换到抗反射涂层光纤，我们将光纤-PIC-光纤互连的插入损耗从 50 降低到 2.14 dB，即 1.47 dB，不包括光纤阵列的损耗。此外，我们确定每个耦合器的损耗上限为 0.45 dB。我们报告称，半径为 15 µm 和 30 µm 的微环的质量因数分别为 27,000 和 77,000，弯曲损耗分别为 6 和 3 dB/cm。我们还演示了贝塞尔自动扶梯、偏振旋转和偏振分离互连以及七通道 25 µm 节距体积互连。 SCRIBE 平台为实现具有独特功能的 3D PIC 提供了一条清晰的途径。