Download this article in .PDF format
This file type includes high resolution graphics and schematics.

Since these materials can be influenced by an external applied voltage, the metamaterial resonance can be switched from active and passive and back again by tuning the sublayer conductivity.25 A hybrid semiconductor formed of these materials consists of SRR electronic plates fabricated on a 1-μm Si-GaAs layer [Fig. 8(a)]. By connecting all SRRs, the structure resembles a Schottky gate in function.25 The carrier electron density can be completely controlled by a reverse voltage, making control of metamaterial resonance and terahertz operation possible [Fig. 8(b)]. This structure can operate with 50% modulation depth at less than 15 V applied bias voltage.26 These metamaterial modulators offer potential as high-speed modulators for imaging and communications applications.27

A spatial light modulator (SLM), which can operate in the terahertz region, is capable of electronic and optical control of transmission and reflection of an optical beam and as a result change of direction and advance coding. These devices are essential for many optical and electronic applications, including imaging and spectroscopy.28 By introducing this technology for use in the terahertz region, it can play an important role in spectroscopy and communication applications.29 As an example, in recent terahertz single pixel imaging, an SLM served as a key component for decoding to terahertz waves.29

9. This schematic diagram shows the components in an amplifier designed for use from 160 to 180 GHz.

Figure 9 shows an amplifier consisting of five 150-GHz stages designed to operate between 160 and 180 GHz. It includes three cascaded stages and two common emitters. The final stage consists of two devices in parallel to achieve high output power. The amplifier is optimized by tuning its resistors, capacitors, and inductors for operation between 140 and 170 GHz. For operation at 170 GHz, capacitors with values of less than 30 fF are required. For such small capacitance values, a metal-oxide-metal structure was developed. Figure 10 offers a MMIC multiplier and amplifier for terahertz use; the MMIC amplifier consists of five simple stages.

10. These photographs offer a multiplier (a) and amplifier (b) designed to produce 125-GHz output signals.

Both photonic and electronic means are capable of reaching terahertz frequencies. As a comparison, Table 2 shows specifications for a 125-GHz transmitter realized by means of photonic (UTC-PD) and electronic (InP HEMT MMIC) approaches.2,4 Each method has advantages and disadvantages, with electronic approaches being somewhat limited in usable output-power levels and photonic approaches also allowing fiber connections from point to point in a system. The technologies are steadily improving, making terahertz applications more feasible in the near future.

 

A. Mohammadi, Researcher

Faculty of Electrical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran; e-mail: a.mohammadi23@aut.ac.ir.

M. Danaeifar, Researcher

Faculty of Electrical and Computer Engineering, K.N. Toosi University of Technology, Tehran, Iran.

References

1. Ho-Jin Song and Tadao Nagatsuma, “Present and Future of Terahertz Communications,” IEEE Transactions On Terahertz Science And Technology, Vol. 1, 2011, p. 1.

2. T. Kleine-Ostmann and T. Nagatsuma, “A review on terahertz communications research,” Journal on Infrared, Millimeter, and Terahertz Waves, Vol. 32, 2011, p. 143.

3.  J. Federici and L. Moeller, “Review of terahertz and subterahertz wireless communications,” Journal of Applied Physics Vol. 107, 2010, p. 111.

4. Jin-Wei Shi, Chen-Bin Huang, and Ci-Ling Pan, “Millimeter-wave photonic wireless links for very high data rate communication,” NPG Asia Mater Vol. 3, 2011, p. 41.

5. Mustafa Rangwala, Feinian Wang, and Kamal Sarabandi, “Study of Millimeter-Wave Radar for Helicopter Assisted-Land ing System,”  IEEE Antennas and Propagation Magazine, Vol. 50, 2008, p. 2.

6. Akihiko Hirata, Toshihiko Kosugi, Hiroyuki Takahashi, et al., “120-GHz-Band Wireless Link Technologies for Outdoor 10-Gbit/s Data Transmission,” IEEE Transactions On Microwave Theory & Techniques, Vol. 60, 2012, p. 3.

7. G.F. Brand, “Development and Applications of Frequency Tunable, Submillimeter-Wave Gyrotrons,” International Journal of Infrared and Millimeter Waves, Vol. 16,1995, p. 879.

8. X. Yin, “Terahertz Imaging for Biomedical Applications: Pattern Recognition and Tomographic Reconstruction,” Vol. 10, 2012, p. 1007.

9. Chen-Bin Huang, Sang-Gyu Park, Daniel E. Leaird, and Andrew M. Weiner, “Nonlinearly broadened phase-modulated continuous-wave laser frequency combs characterized using DPSK decoding,” Vol. 16, 2008, p. 2520.

10. Akihiko Hirata, Mitsuru Harada, and Tadao Nagatsuma, “120-GHz Wireless Link Using Photonic Techniques for Generation, Modulation, and Emission of Millimeter-Wave Signals,” Journal of Lightwave Technology, Vol. 21, 2003, p. 2145.

11. Zhensheng Jia, G.A. Jianjun Yu, Yu-Ting Hsueh, A. Chowdhury, et al., “Multiband Signal Generation and Dispersion-Tolerant Transmission Based on Photonic Frequency Tripling Technology for 60-GHz Radio-Over-Fiber Systems,” IEEE Photonics Technology, Vol. 20, 2008, p. 1027.

12. F.-M.Kuo, J.-W. Shi, H.-C. Chiang, H.-P. Chuang, et al., “Spectral Power Enhancement in a 100 GHz Photonic Millimeter-Wave Generator Enabled by Spectral Line-by-Line Pulse Shaping,” IEEE Photonics Journal, Vol. 2, 2010, p. 719.

13. John D. Albrecht, Mark J. Rosker, H. Bruce Wallacet, and Tsu-Hsi Chang, “THz Electronics Projects at DARPA: Transistors, TMICs, and Amplifiers,” IEEE MTT-S International, Vol. 978, 2010, p. 1118.

14. M. Asada, N. Orihashi, and S. Suzuki, “Voltage-controlled harmonic oscillation at about 1 THz in resonant tunneling diodes integrated with slot antennas,” Japanese Journal of Applied Physics, Vol. 46, 2007, p. 2904.

15. T. Unuma, N. Sekine, and K. Hirakawa, “Dephasing of Bloch oscillating electrons in GaAs-based superlattices due to interface roughness scattering,” Applied Physics Letters, Vol. 89, 2006, p. 161913.

16. T. Suemitsu, Y.M. Meziani, Y. Hosono, M. Hanabe, T. Otsuji, and E. Sano, “Novel plasmon-resonant terahertz-wave emitter using a double-decked HEMT structure,” DRC (Tohoku University, Sendai, 18-20 June 2007), p. 157.

17. W.R. Deal, “Solid-State Amplifiers for Terahertz Electronics Northrop Grumman Aerospace Systems,” IEEE MTT-S International (Redondo Beach CA, May 23-28, 2010), p. 90278.

18. B. Chan, B. Oyama, C. Monier, and A. Gutierrez-Aitken, “An ultra-wideband 7-bit 5-Gsps ADC implemented in submicron InP HBT technology,” IEEE Journal of Solid-State Circuits, Vol. 43, 2008, p. 2187.

19. V. Radisic, X.B. Mei, W.R. Deal, et al., “Demonstration of Sub-Millimeter Wave Fundamental Oscillators Using 35-nm InP HEMT Technology,” IEEE Microwave & Wireless Components Letters, Vol. 17, 2007, p. 223.

20. R. Lai, “Sub 50 nm InP HEMT Device with Fmax Greater than I THz,” IEEE IEDM Digest (Northrop Grumman Space Technology, Redondo Beach, CA, December 10-12, 2007), p. 609.

21. W. Snodgrass, “Pseudomorphic InP/lnGaAsheterojunction bipolar transistors (PHBTs) experimentally demonstrating ft = 765 GHz at 25°C increasing to ft = 845 GHz at -55°C,” IEEE International Electron Devices Meeting (SanFrancisco, CA, December 11-13, 2006).

22. Tong Chen, Willie J. Padilla, Joshua M.O. Zide et al., “Terahertz Switch/Modulator Based on Metamaterials,” IEEE, 2007.

23. Hou-Tong Chen, Willie J. Padilla, Michael J. Cich, et al., “A Broadband Terahertz Metamaterial Electrical Modulator,” IEEE, Vol. 978, 2009, p. 55752.

24. Wai Lam Chan, Hou-Tong Chen, Antoinette J. Taylor, et al., “A Spatial Light Modulator for Terahertz Radiation,” CLEQ/QELS Department of Electrical and Computer Engineering, Rice University (Houston, TX, June 2-4, 2009), p. 1.

25. D. Engstrom, J. Bengtsson, E. Eriksson, and M. Goksor, “A spatial light modulator for terahertz beams,” Optical Express, Vol. 16, 2008, p. 18275.

26. W. L. Chan, K. Charan, D. Takhar, et al., “A single-pixel terahertz imaging system based on compressed sensing,” Applied Physics Letters, Vol. 93, 2008, p. 121105.

27. C. Jastrow, K. Munter, R. Piesiewiczand, et al., “300 GHz transmission system,” Electronics Letters, Vol. 44, 2008, p. 213.

28. E. Laskin, K.W. Tang, K.H.K. Yau, et al., “170-GHz Transceiver with On-Chip Antennas in SiGe,” RFIC IEEE, Toronto University (Toronto, Canada, June 1, 2008), p. 637.

29. Toshihiko Kosugi, Masami Tokumitsu, Koichi Murata, et al., “120-GHz Tx/Rx Waveguide Modulesfor 1O-Gbit/s Wireless Link System,” CSIC IEEE, NTT Corp. (Atsugi, Japan, November 2006),p. 26.

Download this article in .PDF format
This file type includes high resolution graphics and schematics.