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Nature Communications | Breaking the Limits of Resolution and Efficiency in Optical Nano-Printing

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Introduction

In today's rapidly developing technological era, nanoprinting technology is gradually becoming a key force driving progress in fields such as microelectronics, optics, and biomedicine. However, traditional two-photon absorption (TPA) technology has always faced an irreconcilable contradiction between high resolution and high efficiency. High light intensity, while improving printing efficiency, easily causes problems such as photobleaching and micro-explosions, while also limiting the printing resolution; while low light intensity makes it difficult to achieve effective photon absorption, resulting in slow printing speeds. This contradiction has long plagued the development of nanoprinting technology.

Recently, the Photonics Technology Institute of Jinan UniversityAssociate Professor Zhao Yuanyuan、Professor Duan Xuanmingteam, in collaboration with the Institute of Physics, Chinese Academy of SciencesResearcher Zheng Meilingteam, proposed a two-photon absorption (fpTPA) technology based on few-photon irradiation, successfully breaking through the bottleneck of traditional TPA technology and achieving a perfect combination of high resolution and high efficiency. This achievement is titled "Two-photon absorption under few-photon irradiation for optical nanoprinting" and published inNature CommunicationsThe co-first authors of the paper are from the Photonics Technology Institute of Jinan UniversityDr. Liang Zixin、Associate Professor Zhao Yuanyuan、Dr. Chen JingtaoandAssociate Researcher Dong XianziThe corresponding authors areAssociate Professor Zhao Yuanyuan、Researcher Zheng MeilingandProfessor Duan Xuanming。

Figure 1: Schematic diagram of the time-correlated quantum mechanism of two-photon absorption

Few-photon irradiation technology ideas and principles

The two-photon absorption (fpTPA) technology based on few-photon irradiation is based on the principle of wave-particle duality of light. By precisely controlling the number of photons in femtosecond laser pulses, it achieves efficient two-photon absorption under ultra-low photon irradiance. The spatiotemporal model developed by the research team details the time-dependent quantum mechanism of two-photon absorption under few-photon conditions. Under this mechanism, the interaction between photons and molecules is no longer limited to traditional high-intensity conditions, but by precisely controlling the number of photons and pulse width, two photons can be absorbed by molecules within a very short time interval, thus effectively triggering the two-photon absorption process, and the two-photon absorption probability shows a distribution state completely different from the traditional Gaussian distribution. Under ultra-low light flux density, the two-photon absorption probability can be compressed to a nanometer scale range, proving the feasibility of using the two-photon absorption quantum mechanism to break through the diffraction limit of traditional wave optics theory.

Figure 2: Spatiotemporal probability distribution of effective two-photon absorption under few-photon irradiation

Key breakthroughs in high-efficiency and high-resolution printing technology

The research team experimentally verified the enormous potential of few-photon irradiation two-photon absorption technology in nanoprinting. In the experiment, the research team used two-photon digital optical projection lithography (TPDOPL), combined with few-photon irradiation technology, and by precisely controlling the photon flux and the number of pulse accumulations, successfully achieved a minimum feature size of 26 nanometers, which is only one-twentieth of the wavelength, far below the resolution limit of traditional optical exposure technology. Compared with the traditional point-by-point laser direct writing technology, the throughput of TPDOPL technology is increased by five orders of magnitude, enabling the fabrication of large-area nanostructures in a short time. In addition, the research team also proposed an in-situ multiple exposure technology (iDME), which loads multiple patterns on the DMD and performs alternating exposure to achieve the fabrication of high-density patterns without violating the optical diffraction limit. For example, through two alternating exposures, the research team successfully fabricated a dense line array with a period of 210 nanometers (equivalent to 0.41 times the wavelength), which is far below the limit achievable by traditional optical exposure technology.

Figure 3: Schematic diagram of two-photon digital optical projection printing system and simulation and experimental processing results

Multi-scenario application verification and outlook

Few-photon irradiation technology has not only made breakthrough progress in the field of nanoprinting, but also shows broad application prospects in the fields of optical imaging and biomedicine. The research team successfully printed a variety of micro-nano structures using this technology, including optical waveguides, micro-ring resonators, and complex biological microfluidic channels. The feature sizes of these structures cover a cross-scale range from micrometers to nanometers, demonstrating the flexibility and efficiency of few-photon irradiation technology in different application scenarios. In addition, this technology has also been applied to the field of biomedicine, successfully constructing microfluidic chips for virus detection and cell culture, providing new tools for biomedical research.

Figure 4: Two-photon digital optical projection printing optical waveguide, micro-ring resonator, and complex biological microfluidic channel patterns

Summary and outlook

The core innovation of two-photon absorption technology with few-photon irradiation lies in achieving efficient two-photon absorption under ultra-low photon irradiance by precisely controlling the number of photons and pulse width. Compared with traditional TPA technology, this technology not only breaks through the resolution limit but also significantly improves printing efficiency. In addition, this technology does not require complex optical path modification and is compatible with existing digital optical projection systems, with the advantages of low cost, high stability, and high efficiency. This technology not only provides new theoretical and experimental evidence for the field of nanoprinting but also provides an efficient and flexible solution for manufacturing and detection in fields such as microelectronics, optics, and biomedicine, and is expected to promote the further development of related technologies.

Paper Information

Zi-Xin Liang, Yuan-Yuan Zhao, Jing-Tao Chen, Xian-Zi Dong, Feng Jin, Mei-Ling Zheng, Xuan-Ming Duan. Two-photon absorption under few-photon irradiation for optical nanoprinting.Nature Communications16, 2086 (2025).

https://doi.org/10.1038/s41467-025-57390-9