Professor Yun Feng’s team from Xi’an Jiaotong University has made new progress in the field of online polarized LEDs

Nitride-based light-emitting diodes (LEDs) can be widely used in lighting, display and communication fields. Among them, the linear polarization characteristics of the light source are a key functional expansion, opening up new application paths for display backlight, 3D imaging, information encryption, biomedical diagnosis and other fields. However, existing LEDs epitaxially grown on c-plane sapphire substrates are generally regarded as non-polarized light sources with extremely low polarization extinction ratios (ER), making it difficult to meet application requirements.

Research has found that ER can be improved by integrating linearly polarized optical structures on the surface of LEDs. These structures serve as mode-selective layers to extract transverse magnetic (TM) modes to achieve polarized emission. However, at least 50% efficiency loss inevitably results as the transverse electric (TE) modes are absorbed or reflected. This contradiction between polarized emission and luminous efficiency restricts the development and application of linearly polarized LEDs.

In response to this problem, Professor Yun Feng's team from the Institute of Advanced Optoelectronics, School of Electronic Science and Engineering, Department of Telecommunications, Xi'an Jiaotong University, successfully introduced an Ag/GaN superstructure grating structure with a loss mode recycling mechanism through innovative design, solving the contradiction between polarization and efficiency in linearly polarized LEDs, and achieving a dual improvement in luminous efficiency and polarization degree. The specially designed metagrating structure is manufactured using low-cost laser interference lithography technology. It induces TE/TM mode conversion through the birefringence effect, and at the same time establishes momentum compensation through Bragg scattering to promote the decoupling of the trapped TM mode.。

On this basis, the team further integrated the mode selection layer of the Al nanograting, and successfully realized the blue linear polarized Micro-LED based on gallium nitride. The Micro-LED achieves an average polarization extinction ratio (ER) of 21.92 dB at a viewing angle of ± 60°, which is 2.04 times more efficient and 1.32 times more ER than traditional Ag reflector designs. This research result significantly reduces energy loss, successfully breaks the efficiency bottleneck of polarized emission light source, and opens the way for the next generation of high-efficiency and low-cost optoelectronic devices applied in the fields of information encryption, future display, optical communication and medicine.

Performance of high-efficiency linearly polarized miniature light-emitting diodes

The result was titled "High-efficient and linearly polarized light emission of Micro-LED integrated with double-functioned meta-grating" and was published in the international authoritative journal "Nano-Express"

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Yun Feng, Professor Li Feng and Associate Professor Tian Zhenhuan of the School of Electronics are the co-authors of the paper. Xi 'an Jiaotong University is the first author unit and the only correspondent author unit. The work was given to the National Natural ScienceSupported by the fund project, the characterization and testing of the thesis were supported by researchers from Jia Chunlin's Scientist Studio.