Chinese researchers have made a groundbreaking advance in terahertz (THz) technology, developing a novel device that enables precise, achromatic control of THz wave polarization. This innovation, led by experts from the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences (CAS) in collaboration with Nanjing University, promises to revolutionize high-speed communications, advanced imaging, and material science. As China positions itself as a global leader in next-generation wireless technologies like 6G, this breakthrough underscores the pivotal role of its higher education institutions in driving cutting-edge research.

Terahertz waves, lying between microwaves and infrared light on the electromagnetic spectrum (typically 0.1 to 10 THz), offer immense potential due to their high bandwidth and non-ionizing nature. However, controlling their polarization— the orientation of their electric field—has been challenging because of dispersion and material limitations. The new phase-compensated mirror-total internal reflection (PCMT) device overcomes these hurdles, achieving over 90% relative bandwidth with polarization purity exceeding 0.996 across 1.6 to 3.4 THz. Published in Optica (DOI: 10.1364/OPTICA.540172), the work demonstrates dynamic switching between linear, circular, and arbitrary polarization states with minimal intensity loss.

🔬 Understanding Terahertz Waves and Their Challenges

Terahertz radiation, often called the 'T-ray' gap, has unique properties: short wavelengths for high resolution and vast bandwidth for data rates up to terabits per second. In higher education, Chinese universities have invested heavily in THz research amid national priorities for 6G and beyond. Challenges include atmospheric absorption, limited sources/detectors, and polarization control, where phase mismatches distort signals.

Historically, THz polarization devices relied on bulky setups like wire grids or metasurfaces, limited to narrow bands (<30%). The PCMT device uses a tunable liquid crystal layer between a mirror and prism, compensating phase via distance adjustment and birefringence tuning. Step-by-step: (1) THz wave reflects off mirror-prism interface, (2) liquid crystal introduces controllable delay, (3) total internal reflection preserves intensity, (4) output polarization is precisely manipulated electrically.

• Bandwidth advantage: 1.8 THz tunable center, >90% relative.
• Purity: DoLP/DoCP >0.996.
• Switching speed: Milliseconds via voltage.

Key Players: Nanjing University and CAS Collaboration

Nanjing University, a top-tier institution in China with strong physics and optics programs, partnered with AIR-CAS. Prof. Chen Xuequan, lead researcher at AIR, highlighted, "THz waves can now be tamed with precision." This exemplifies China's 'Double First-Class' initiative, elevating universities like Nanjing (ranked top 10 nationally) in strategic tech.

Recent THz efforts at Chinese universities include Tianjin University's switchable THz skyrmions (Optica 2026), enabling vortex beams for multiplexing. Southeast University and Tsinghua also lead in THz emitters/detectors, fostering interdisciplinary labs.

Technical Breakdown: How the PCMT Device Works

The innovation lies in phase compensation. THz enters via prism, hits mirror, reflects through liquid crystal (birefringence Δn tunable 0-0.2 via voltage), undergoes total internal reflection, exits with controlled phase difference δ between s/p components. Formula: δ = (2π/λ) * d * Δn, where d is path length.

Test results: At 2 THz, linear-to-circular switch in 1 ms; arbitrary Stokes parameters controlled. Compared to metasurfaces (narrowband), PCMT offers universality.

Applications Revolutionizing Industries

In 6G, polarization multiplexing boosts capacity 2-4x for wireless backhaul. Security: THz penetrates plastics/non-metals for concealed weapon detection. Biomed: Non-destructive pharma quality control, cultural relic scanning without damage.

China's THz market projected $1B by 2030; universities commercialize via spin-offs, e.g. THz imaging firms from Southeast U.

China's Higher Education Ecosystem Fueling THz Innovation

Under 'Made in China 2025', universities receive billions in grants. CAS-NU model: PhD students gain dual mentorship. Tianjin U's Center for Terahertz Waves trains 100+ grads yearly. Enrollment in optics/EE up 20% since 2020.

• National labs + unis: 500+ THz papers/year from China.
• Talent: 10k THz specialists by 2030 target.

Challenges: IP protection, international collab post-US bans.

Global Context and Competitive Edge

US/EU lead detectors; China excels emitters/modulators. Vs Japan (NTT THz), China's bandwidth superior. Implications: China 6G patents 40% global.

Future Outlook: 6G and Beyond

Next: Integrated chips, AI-optimized control. Unis like Peking U eye THz quantum comm. Projections: THz in consumer devices by 2030.

Stakeholder Perspectives

Experts: "Game-changer for THz deployment" - Prof. Han Jiaguang, Tianjin U. Industry: Huawei integrates similar tech.

Actionable Insights for Researchers and Students

Aspiring THz experts: Pursue optics at Nanjing/Tsinghua. Grants via NSFC. Collaborate via Belt-Road THz forums.

Photo by Blaz Erzetic on Unsplash

This breakthrough cements China's HE as THz powerhouse, blending academia-industry for societal impact. Explore opportunities in China's vibrant research landscape.