Two photon absorption quantum mechanism breaks through the resolution and efficiency limits of optical nanoprinting

Recently, a research team from the School of Physics and Optoelectronic Engineering at Jinan University has elucidated for the first time the time-dependent quantum mechanism of two-photon absorption and proposed a two-photon absorption (fpTPA) optical nanoprinting technology based on few photon irradiation, successfully breaking through the bottleneck of traditional two-photon printing technology and achieving a perfect combination of high resolution and high efficiency.

Two photon absorption (TPA) is a nonlinear optical phenomenon widely used in three-dimensional fluorescence imaging and nanostructure processing. Traditional TPA technology uses high-intensity focused laser beams to excite fluorescent molecules for three-dimensional fluorescence imaging, or induces local chemical cross-linking reactions for three-dimensional nanoprocessing. However, high-intensity focused laser beams not only cause unnecessary high-order nonlinear optical effects, leading to problems such as phototoxicity, photobleaching, and micro explosions, but also limit their resolution and efficiency improvement.

Based on the existing research paradigm of two-photon effects based on wave optics theory, the research team started from the basic principles of quantum theory and constructed a quantum image of the two-photon absorption process using optical quantum properties such as wave particle duality, superposition state, uncertainty principle, and random probability statistics. They established a spatiotemporal quantum model of two-photon absorption under few photon irradiation and elucidated the time-dependent quantum mechanism of two-photon absorption. The simulation results show that under highly focused few photon femtosecond laser pulse irradiation, the probability of two-photon absorption exhibits a completely different distribution state from the traditional Gaussian distribution. Under ultra-low optical flow density, the probability of two-photon absorption can be compressed to the nanometer scale, proving the feasibility of using the quantum mechanism of two-photon absorption to break through the diffraction limit of traditional wave optics theory.

Schematic diagram of time-dependent quantum mechanism of two-photon absorption

The research team utilized digital optical projection nanolithography (TPDOPL) technology, combined with low photon irradiation technology, to achieve a minimum feature size of 26 nanometers by precisely controlling photon flux and pulse accumulation times. This size is only one twentieth of the wavelength, far below the resolution limit of traditional optical exposure techniques. Compared with traditional point by point laser direct writing technology, TPDOPL technology has increased throughput by 5 orders of magnitude and can achieve large-area nanostructure manufacturing in a short period of time. In addition, the research team also proposed an in-situ multiple exposure technique (iDME), which can achieve high-density pattern manufacturing without violating the optical diffraction limit by loading multiple patterns on the DMD and alternately exposing them. For example, through two alternating exposures, the research team successfully manufactured a dense line array with a period of 210 nanometers (equivalent to 0.41 times the wavelength), which is far below the limit that traditional optical exposure techniques can achieve.

Schematic diagram and simulation and experimental processing results of two-photon digital optical projection lithography system

This research work re examines the two-photon absorption effect from the perspective of fundamental photon properties, providing new ideas for ultra weak light nonlinear optics and enormous potential for the development of new principle based super diffraction optical technology and its cutting-edge applications in related fields. In the field of microelectronics, this technology can be used for the preparation of highly integrated chips; In the field of optics, it can be used for the manufacturing of high-performance optical waveguides and micro ring resonators; In the field of biomedical research, this technology can produce microfluidic chips for cell culture and virus detection, providing new tools for biomedical research. The research team pointed out that the success of two-photon absorption (fpTPA) technology under low photon irradiation has brought new hope to the fields of nanomanufacturing and nanoimaging. Through further optimization, this technology is expected to be used for nanofabrication below 10 nanometers and even single-molecule imaging.

This research has received support from national key research and development programs, the "Guangdong Special Support Program" for leading talents in scientific and technological innovation, national natural science foundation projects, Guangzhou Key Field Research and Development Program, Guangdong Provincial Natural Science Foundation, and other projects.

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 Communications 16, 2086 (2025). 

Source: opticsky