Terahertz

Introduction in one sentence

Terahertz (also known as submillimeter radiation) consists of electromagnetic waves from 0.1 to 30 terahertz (THz). One terahertz is 1012 Hz or 1000 GHz. [Read more at Wikipedia]

Terahertz Research at I2R

Jun Long did his final year project at I2R in 2009 to 2010 as intern under the supervision of Prof. Shum, Ping Perry and co-supervision of Dr. Gong Yandong. He also worked closely with Dr. Ruixiang Guo who that point of time came from Tera-photonics Lab, Research Institute of Physics and Chemistry (RIKEN) to I2R. Jun Long thank Dr. Gong and Dr. Guo for the research experience at I2R.

References Related to Jun Long THz Research at I2R

  1. Lim, Jun Long (2010), Development of surface-emitted Terahertz measurement applications. Singapore, Nanyang Technological University. Retrieved from https://repository.ntu.edu.sg/handle/10356/40745
    • Abstract
      • The project contributed to the development of a powerful and compact Terahertz system that would replace decade old Terahertz systems that were expensive and bulky. The Terahertz Parametric Oscillator (TPO) was one of it and it operated under room temperature, making it a popular Terahertz source. Coherent and strong Terahertz wave was generated by the TPO for spectroscopy and imaging experiments. The two experiments of the THz spectroscopy and imaging were discussed in the report and later published in the conference below.
  2. Ruixiang Guo, Jun Long Lim, Varghese Paulose, Yandong Gong, Hiroaki Minamide, and Hiromasa Lto, "Monochromatic, wide tunable terahertz-wave spectrometer working at room temperature, " in Proc. of 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Rome, Italy, Sep. 2010. DOI: 10.1109/ICIMW.2010.5612622 . IEEE
    • Abstract
      • Using a surface-emitted THz parametric oscillator, an MgO:LiNbO3-based frequency up-conversion detector and a special optical design for fast frequency tuning and achromatic THz-wave detection, we realized a room-temperature-operated THz frequency-domain spectrometer (THz-FDS).

Keywords: Optical frequency conversion, terahertz parametric oscillator, spectroscopy, imaging

Selected THz Research at I2R

  1. Wang Dacheng, Yandong Gong, and Minghui Hong, “Complimentary bilayer metasurfaces for enhanced terahertz wave amplitude and phase manipulation,” Opto-Electronics Engineering, vol. 44, no. 1, pp. 77-81, Jan. 2017. DOI: 10.3969/j.issn.1003-501X.2017.01.007
  2. Ma Zhijie, Stephen M. Hanham, Paloma Arroyo Huidobro, Yandong Gong, Minghui Hong, Norbert Klein, and Stefan A. Maier, “Terahertz particle-in-liquid sensing with spoof surface plasmons,” APL Photonics, vol. 2, pp. 116102, Oct. 2017. DOI: 10.1063/1.4998566
    • Open access article at URL https://aip.scitation.org/doi/10.1063/1.4998566
    • We present a highly sensitive microfluidic sensing technique for the terahertz (THz) region of the electromagnetic spectrum based on spoof surface plasmon polaritons (SPPs). By integrating a microfluidic channel in a spoof SPP waveguide, we take advantage of these highly confined electromagnetic modes to create a platform for dielectric sensing of liquids. Our design consists of a domino waveguide, that is, a series of periodically arranged rectangular metal blocks on top of a metal surface that supports the propagation of spoof SPPs. Through numerical simulations, we demonstrate that the transmission of spoof SPPs along the waveguide is extremely sensitive to the refractive index of a liquid flowing through a microfluidic channel crossing the waveguide to give an interaction volume on the nanoliter scale. Furthermore, by taking advantage of the insensitivity of the domino waveguide’s fundamental spoof SPP mode to the lateral width of the metal blocks, we design a tapered waveguide able to achieve further confinement of the electromagnetic field. Using this approach, we demonstrate the highly sensitive detection of individual subwavelength micro-particles flowing in the liquid. These results are promising for the creation of spoof SPP based THz lab-on-a-chip microfluidic devices that are suitable for the analysis of biological liquids such as proteins and circulating tumour cells in buffer solution.
  3. Ma Zhijie, Zhijie Ma, Stephen M. Hanham, Pablo Albella, Binghao Ng, Hsiao Tzu Lu, Yandong Gong, Stefan A. Maier, and Minghui Hong, “Terahertz All-Dielectric Magnetic Mirror Metasurface,” ACS Photonics, vol. 3, no. 6, pp. 1010–1018, May 2016. DOI: 10.1021/acsphotonics.6b00096
  4. Wang Dacheng, Gu Yinghong, Gong Yandong, Qiu ChengWei, and Hong Minghui, “An ultrathin terahertz quarter-wave plate using planar babinet-inverted metasurface,” Optics Express, vol.23, no.9, pp. 11114-11122, Apr. 2015. DOI: 10.1364/OE.23.011114
  5. Dacheng Wang, Lingchao Zhang, Yinghong Gu, M. Q. Mehmood, Yandong Gong, Amar Srivastava, Linke Jian, T. Venkatesan, Cheng-Wei Qiu, and Minghui Hong, “Switchable Ultrathin Quarter-wave Plate in Terahertz Using Active Phase change Metasurface” Nature: Scientific Reports, vol.5, no. 15020, Oct. 2015. DOI: 10.1038/srep15020
    • Open access article at URL https://www.nature.com/articles/srep15020
    • Abstract: Metamaterials open up various exotic means to control electromagnetic waves and among them polarization manipulations with metamaterials have attracted intense attention. As of today, static responses of resonators in metamaterials lead to a narrow-band and single-function operation. Extension of the working frequency relies on multilayer metamaterials or different unit cells, which hinder the development of ultra-compact optical systems. In this work, we demonstrate a switchable ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide (VO2), with a metasurface. Before the phase transition, VO2 behaves as a semiconductor and the metasurface operates as a quarter-wave plate at 0.468 THz. After the transition to metal phase, the quarter-wave plate operates at 0.502 THz. At the corresponding operating frequencies, the metasurface converts a linearly polarized light into a circularly polarized light. This work reveals the feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel applications of ultrathin terahertz meta-devices.
  6. Banghong Zhang and Yandong Gong, “Achromatic terahertz quarter waveplate based on silicon grating,” Optics Express, vol. 23, no. 11, pp. 14897-14902, May 2015. DOI: 10.1364/OE.23.014897
  7. Yandong Gong, Banghong Zhang, Takashi Notake, and Hiroaki Minamide, “Investigations on Polarimetric Terahertz Frequency Domain Spectroscopy,” Applied Physics A, vol. 115, no. 1, pp. 83-86, Apr. 2014. DOI: 10.1007/s00339-013-8000-0
  8. T. Notake, Yandong Gong, H. Minamide, "Development of a Stokes polarimeter system for high terahertz frequency region," Japanese Journal on Applied Physics (JJAP), vol. 53, no. 9, pp. 092601, Sep. 2014. DOI: 10.7567/JJAP.53.092601
  9. Banghong Zhang, Yandong Gong, and H. Dong. “Thin-form birefringence quarter-wave plate for lower terahertz range based on silicon grating,” Optical Engineering, vol. 52, no. 3, pp. 030502, Feb. 2013. DOI: 10.1117/1.OE.52.3.030502
  10. Yandong Gong, H. Dong, and Zhining Chen, “Cross-polarization Response of a Two-contact Photoconductive Terahertz Detector,” International Journal of Terahertz Science and Technology, vol.4, no.3, 137-148, Sep. 2011. http://www.tstnetwork.org/10.11906/TST.137-148.2011.09.21
  11. Gong Yandong, Dong H., and Varghese Paulose, “Simple Methods to Measure Partial Polarization Parameters in the Terahertz Band Using THz-TDS,” Microwave and Optical Technology Letters, nol.52, no.9, pp. 2005-2007, Sep. 2010. DOI: 10.1002/mop.25407
  12. Guobin Ren, Yandong Gong, Shum, Ping, Yu Xia, and Hu Juanjuan, “Polarization Maintaining Air-core Bandgap Fibers for Terahertz Wave Guiding,” IEEE Journal of Quantum Electronics, Volume 45, No.5, 506 – 513, (2009). DOI: 10.1109/JQE.2009.2013099

THz Funding Support

  1. A-STAR/SERC grant No.: 102 163 0069
  2. CRP Award No. NRF-CRP10-2012-04
  3. CRP Award No. NRF-CRP4-2008-04
  4. SERC A*STAR, Singapore under Project No.1420200044
  5. EDB, Singapore Grant No. S15-1322-IAF OSTIn-SIAG
  6. Grant No. EP/M001121/1 from the UK’s Engineering and Physical Science Research Council (EPSRC)

Note: Funding data extracted from publication listed above.

Notable THz Researchers in Singapore

  1. Professor Minghui Hong [NUS]
    • Fellow of Optical Society of America (OSA), The International Society for Optics and Photonics (SPIE) and International Academy of Photonics and Laser Engineering (IAPLE)