Â鶹ÒùÔº

In a development that could reshape the future of microelectronics, optics, and biomedicine, researchers from Jinan University, in collaboration with the Institute of Chemistry at the Chinese Academy of Sciences, have unveiled a new nanoprinting technology that simultaneously achieves unprecedented resolution and efficiency.

Their study, titled "Two-photon absorption under few-photon irradiation for optical nanoprinting," is in Nature Communications.

For decades, two-photon absorption (TPA) has been a cornerstone in optical nanoprinting, but it has faced a fundamental trade-off: high light intensity boosts printing speed but degrades resolution and risks damaging materials, while low light intensity preserves resolution but drastically slows down the process. This inherent conflict has long constrained the evolution of high-performance nanofabrication.

Now, a team led by Associate Professor Yuanyuan Zhao and Professor Xuanming Duan at the Institute of Photonic Technology, Jinan University, alongside Researcher Meiling Zheng's group at the Chinese Academy of Sciences, has introduced an innovative strategy called few-photon two-photon absorption (fpTPA).

By precisely controlling the number of photons within femtosecond laser pulses, they have demonstrated that efficient two-photon absorption can occur even under ultra-low photon exposure—shattering the long-standing performance bottleneck.

The fpTPA technique leverages the wave-particle duality of light, carefully orchestrating femtosecond pulses to ensure that two photons are absorbed by a molecule in rapid succession, even at remarkably low photon fluxes. A newly developed space-time model describes the quantum-mechanical interaction pathways under these sparse photon conditions.

Unlike traditional TPA, which relies on strong, continuous photon fields, fpTPA enables highly localized two-photon events within nanometer-scale regions, effectively breaking through the diffraction limit dictated by classical optics.

Pushing resolution to the edge—and beyond

Using their few-photon approach integrated with two-photon digital optical projection lithography (TPDOPL), the team achieved feature sizes as small as 26 nanometers—just one-twentieth of the operating wavelength. This represents a massive leap compared to traditional laser direct writing methods. Moreover, the TPDOPL system enhanced throughput by five orders of magnitude, allowing large-scale, high-resolution structures to be printed rapidly.

An additional innovation, termed in-situ double mask exposure (iDME), was also introduced. By sequentially exposing multiple digital mask patterns, the researchers fabricated dense nanostructures with a periodicity of just 210 nanometers (around 0.41 times the wavelength), well below traditional optical limits without sacrificing structural integrity.

Applications across optics, electronics, and biomedicine

Beyond pushing the limits of printing resolution, the few-photon TPA technology demonstrated exceptional versatility. The researchers successfully fabricated a wide range of micro- and nanostructures—including optical waveguides, microring resonators, and complex bio-microfluidic channels—highlighting its potential across optical communication and biomedical engineering.

Notably, the technique has been applied to build microfluidic chips used for virus detection and cell culture, offering a powerful new tool for life sciences research.

A new era of accessible nanomanufacturing

Crucially, this breakthrough does not require extensive modifications to existing optical setups. The few-photon TPA method is compatible with standard digital optical projection systems, offering a cost-effective, stable, and highly scalable pathway to next-generation nanomanufacturing.

"This technology fundamentally changes how we think about two-photon processes," says Zhao. "It opens up a practical and efficient route to achieve ultra-high-resolution fabrication without compromising throughput, paving the way for new advances in microelectronics, photonics, and biomedicine."

With its deep theoretical foundation and wide-ranging applications, few-photon two-photon absorption stands poised to redefine the future landscape of nanoscale fabrication.