UCLA Researchers Unveil Unidirectional Light Focusing Using Diffractive Optics

Researchers at the University of California, Los Angeles (UCLA) have unveiled a new optical technology that enables precise focusing of light – only in one direction. This novel unidirectional focusing design uses structured diffractive layers that are optimized using deep learning to transmit light efficiently in the forward direction of operation while effectively suppressing unwanted backward focusing of light. This innovation offers a compact and broadband solution for the unidirectional delivery of radiation with significant potential for applications in security, defense, and optical communications.

A New Frontier in Unidirectional Light Control with Diffractive Optics
Controlling asymmetric light propagation—where light preferentially travels in one direction while being blocked or scattered in the opposite direction—has been a longstanding need in optical systems. Traditional solutions often rely on specialized material properties or nonlinear materials, which require relatively complex and costly fabrication methods, bulky hardware, and high-power laser sources. Other approaches, including asymmetric gratings and metamaterials, have shown promise but remain limited due to their polarization and wavelength sensitivity, complex design constraints, and poor performance under oblique illumination.

The new diffractive unidirectional light focusing system developed by UCLA researchers addresses these challenges through a different approach. By using deep learning to optimize the structures of a series of passive, isotropic diffractive layers, the team created a compact and broadband optical system that efficiently focuses light in the forward direction while suppressing light focusing in the reverse direction. This design is inherently polarization-insensitive and scalable across multiple wavelengths, enabling consistent unidirectional light control over a broad spectral range. Unlike traditional methods that rely on complex materials or nonlinear optical effects, this deep learning-based optimized 3D structure achieves asymmetric light propagation using passive, isotropic diffractive layers, eliminating the need for active modulation or high-power sources.

The UCLA research team demonstrated the effectiveness of their system using terahertz (THz) radiation. Using a 3D printer, they fabricated a two-layer diffractive structure that successfully focused the THz radiation in the forward direction while blocking backward-propagating energy. This experimental validation confirmed the system’s practical capability for all-optical, passive control of unidirectional light propagation.

By enabling directional control of light without relying on active modulation, nonlinear materials or high-power sources, this technology can be used to enhance the efficiency and security of free-space optical links, particularly under dynamic or noisy conditions. Furthermore, the compact and passive nature of the system makes it ideal for integration into advanced imaging and sensing platforms, where directional light control can enhance signal clarity and reduce background interference in complex or cluttered settings. By suppressing unwanted back-reflections, this technology can also be used to enhance the stability and performance of a wide range of optical systems—including laser machining platforms, biomedical instruments, and precision metrology setups—where the reflected light can otherwise introduce noise, reduce accuracy, or damage sensitive components.

The versatility and robustness of this diffractive unidirectional focusing design make it a strong candidate for diverse optical applications. Following its successful demonstration in the terahertz regime, the UCLA team is working to scale the technology to other parts of the electromagnetic spectrum, including the visible and infrared wavelengths, using advanced nanofabrication techniques.

“Our diffractive unidirectional focusing system introduces a compact, passive, and scalable approach to asymmetric light processing and control,” said Professor Aydogan Ozcan, the senior author of the publication and the Volgenau Chair for Engineering Innovation at UCLA. “We are excited about the wide range of possibilities this technology can enable in next-generation optical communication and sensing systems as well as light delivery systems.”

The study was supported by the US National Science Foundation (NSF). The co-authors of this publication include graduate students Y. Li, T. Gan, J. Li as well as Professors M. Jarrahi and A. Ozcan, all from UCLA.