Key Takeaways & Executive Findings
- •• Submicron light sources are realized using only standard UV photolithography, enabling arbitrary patterns without complex nanofabrication. • A novel shadow-assisted sidewall emission (SASE) technique precisely controls polymer sidewall emission via metal shadow modulation. • Red, green, and blue submicron light sources are successfully demonstrated, with linewidth tunable by exposure dose, development time, and metal thickness. • The SASE-based light sources show strong scalability and are proven applicable in optical anti-counterfeiting, offering a cost-effective route for high-resolution micro-optics.
Abstract
Micro light sources are crucial tools for studying the interactions between light and matter at the micro/nanoscale, encompassing diverse applications across multiple disciplines. Despite numerous studies on reducing the size of micro light sources and enhancing optical resolution, the efficient and simple fabrication of ultra-high-resolution micro light sources remains challenging due to its reliance on precise micro-nano processing technology and advanced processing equipment. In this study, a simple approach for the efficient fabrication of submicron light sources is proposed, namely shadow-assisted sidewall emission (SASE) technology. The SASE utilizes the widely adopted UV photolithography process, employing metal shadow modulation to precisely control the emission of light from polymer sidewalls, thereby obtaining photoluminescent light sources with submicron line widths. The SASE eliminates the need for complex and cumbersome manufacturing procedures. The effects of process parameters, including exposure dose, development time, and metal film thickness, on the linewidth of sources are investigated in detail. It is successfully demonstrated red, green, and blue submicron light sources. Finally, their potential application in the field of optical anti-counterfeiting is also demonstrated. We believe that the SASE proposed in this work provides a novel approach for the preparation and application of micro light sources.
1. Introduction
The development and application of microscale light sources have provided unprecedented optical resolution and precision for scientific research, enabling the manipulation of light–matter interactions at the nanoscale [1–3]. This progress not only extends the frontier of optical field control but also establishes a foundation for ultra-high-resolution optical detection, precise light modulation, and the development of novel optical functional devices. With continuous improvements in fabrication techniques, microscale light sources are also evolving toward stability, and tunability, offering new avenues for surpassing the performance limitations of conventional optical devices. The core characteristic of microscale light sources is their ability to generate light output within micron and even submicron spatial ranges, allowing precise control over the interaction region between light and matter, thereby obtaining material information at submicron scales [4–6].
This high-precision control capability is of great significance in various fields, particularly in bioimaging, optogenetics, microspectroscopy, and biomedical applications [7–10]. For instance, in bioimaging, high-resolution microscale light sources enhance super-resolution fluorescence microscopy. Wijesooriya reported that photoactivatable BODIPY probe is used as microscale light sources for single-molecule localization-based super-resolution microscopy. It has been proved to be effective for live-cell imaging and is compatible with various biological samples [11]. In optogenetics, they enable precise stimulation of specific cells, thereby enhancing spatial selectivity and experimental controllability. Dai proposed a new type of tiny multimaterial glass fiber, which allows for simultaneous deep neural stimulation and detection for more than 2 weeks at a single cellular level. The microscale light sources promote the development of neuroscience and brain science through the ability to manipulate neural circuits in the deep brain [12]. Therefore, enhancing the optical resolution of microscale light sources to precisely target smaller spatial scales has always been a major objective in scientific research [13–17].
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Junlong Li, Yanmin Guo, Kun Wang, Wei Huang, Hao Su, Wenhao Li, Xiongtu Zhou, Yongai Zhang, Tailiang Guo, Chaoxing Wu (2025). Shadow-Assisted Sidewall Emission for Achieving Submicron Linewidth Light Source by Using Normal UV Photolithography. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01737-w
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Frequently Asked Questions
What is shadow-assisted sidewall emission (SASE) technology?
SASE is a novel fabrication method that uses standard UV photolithography and metal shadow modulation to precisely control light emission from polymer sidewalls, enabling the creation of submicron linewidth light sources without complex nanofabrication equipment.
How does SASE achieve submicron linewidths?
By employing metal shadow modulation during UV photolithography, SASE selectively blocks or allows UV exposure to define narrow polymer sidewall regions. The linewidth can be tuned by adjusting exposure dose, development time, and metal film thickness.
What materials are used in the SASE process?
The process utilizes quantum dots (QDs) for photoluminescence, polymer materials for the sidewalls, and metal films for shadow modulation. Red, green, and blue submicron light sources have been demonstrated.
What are the potential applications of SASE-based light sources?
The submicron light sources are scalable and have been proven applicable in optical anti-counterfeiting. They also hold promise for bioimaging, optogenetics, microspectroscopy, and other fields requiring high-resolution light sources.
What are the advantages of SASE over conventional micro/nanofabrication methods?
SASE simplifies the fabrication process by relying on widely available UV photolithography, eliminating the need for expensive and complex equipment such as electron beam lithography or focused ion beam. This makes it more efficient, cost-effective, and accessible for producing submicron light sources.
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