In a significant leap forward for photonics engineering, researchers at Zhejiang University (ZJU) in China have pioneered a breakthrough method to fabricate intricate micro/nano optical fibers (MNFs) with tailored geometric precision. Led by Prof. Yaoguang Ma, the team’s innovation overcomes a longstanding barrier in optical fiber production, potentially accelerating advancements in sensing, quantum computing, and nonlinear optics. MNFs—thread-like structures with diameters matching light’s wavelength—serve as foundational components in technologies ranging from biomedical sensors to ultra-fast lasers. Yet, until now, creating MNFs with sophisticated cascaded structures (multi-segment designs with varied diameters) has been hampered by uncontrollable thermal airflows during conventional fabrication, introducing instability and limiting structural complexity.

The ZJU team’s solution centers on a custom-engineered ​vertical drawing system, which fundamentally reorients the fabrication process. Unlike established horizontal tapering approaches, this table-top setup aligns thermal airflow parallel to the gravitational pull direction. This critical co-directionality neutralizes turbulence-induced deviations that typically distort microfiber geometry. By stabilizing the thermal environment, the system enables meticulous control over diameter transitions along the fiber’s length, allowing engineers to "program" cascaded segments with nanometer-scale accuracy. This stability translates to more compact, efficient, and functionally tailored MNFs—designs previously unattainable using traditional methods.

Leveraging their vertical platform, Prof. Ma’s group successfully fabricated ​four-segment cascaded MNFs​ measuring a record 120 millimeters in length, with the narrowest section tapered to a remarkable ​1-micron diameter. Such extended, structurally graded fibers unlock new possibilities for manipulating light-matter interactions. The team specifically optimized these fibers for ​supercontinuum generation—a nonlinear optical phenomenon essential for creating ultrabroadband light sources. Through rigorous simulations followed by experimental validation, the researchers demonstrated a strikingly ​flat supercontinuum spectrum spanning 1463–1741 nanometers, achieving a high efficiency of ​264.62 nanometers per kilowatt​ of input power. This spectral breadth and uniformity could enhance applications in optical coherence tomography, spectroscopy, and telecommunications.

Published in the journal Frontiers of Optoelectronics under the title ​​“Precision Vertical Drawing of Diameter-Gradient Microfibers: Cascaded Geometries for Tailored Nonlinearity” (published on Aug. 4, 2025), this research transforms how scientists construct and exploit micro-scale optical platforms. Beyond supercontinuum generation, the vertical drawing technique opens avenues for creating fibers with customized nonlinear responses for quantum light sources, precision environmental sensors, and ultra-compact photonic circuits. Prof. Ma’s approach doesn’t merely refine existing methods—it redefines the limits of optical fiber engineering, positioning cascaded MNFs as versatile tools for tomorrow’s photonics revolution.
DOI: 10.1007/s12200-025-00160-8