Int J Infrared Milli Waves (2008) 29:1091–1102

DOI 10.1007/s10762-008-9423-0

Terahertz (THz) Frequency Sources

and Antennas - A Brief Review

P. Mukherjee & B. Gupta

Received: 14 May 2008 / Accepted: 4 September 2008 /

Published online: 17 September 2008
# Springer Science + Business Media, LLC 2008

Abstract In this paper we review THz radiation properties, generation methods, and antenna
configurations. This paper suggests some new class of antennas that can be used at THz
frequency, like optical antennas or Carbon nanotube antennas. THz technology has become
attractive due to the low energy content and nonionizing nature of the signal. This property
makes them suitable for imaging and sensing applications. But at the same time detection and
generation of THz signals has been technologically challenging. This paper presents a
comparative study of the generation techniques for THz frequency signals giving emphasis to
the some new techniques like Quantum Cascade lasers which has created significant research
interest. The main aim for this study is to find out the materials suitable for fabricating THz
devices and antennas, a suitable method for generation of high power at THz frequency and an
antenna that will make THz communication possible.

Keywords Terahertz (THz) . Antennas . Imaging . Sensing . Quantum cascade laser

1 Introduction

Terahertz (THz) frequency spectrum, can be defined as the portion of the sub millimeter
wavelength electromagnetic (EM) spectrum between approximately 1 mm and 100 μm of
wavelength (300 GHz-3 THz) (Fig. 1) and it has the potential of playing a major role in
technological and scientific application areas [1–4]. THz frequency range lies in the gap
between microwave band and infrared band of frequencies. Thus combination of technologies
used in these two ranges can be applied to develop THz systems.
THz radiation exhibits the following properties [5]:
& Penetration—THz waves pass through common clothing and packaging materials with
relatively little attenuation.

P. Mukherjee (*)
Department of Electronics and Telecommunication Engineering,
Institute of Engineering and Management, Salt Lake, Calcutta, India
e-mail: pinakimail@yahoo.co.in

B. Gupta
Department of Electronics and Telecommunication Engineering, Jadavpur University,
Calcutta 700032, India
1092 Int J Infrared Milli Waves (2008) 29:1091–1102

Fig. 1 The electromagnetic spectrum showing the 'THz gap' between microwave and infrared band.

& High-resolution imaging—the short wavelengths of THz signals in comparison to micro-

waves can be used to provide images with submillimeter resolution.
& Spectroscopy—many solids exhibit characteristic spectral features in the 0.5–3.0 THz
region. This enables different chemical substances to be detected—even when sealed inside
a packet or concealed in clothing.
& Non ionizing—THz radiation is nonionizing and can be used at very low power levels in
the microwatt range due to the availability of high sensitivity coherent detection schemes.
This property of THz radiation makes it suitable for use in biological and medical
applications [6, 7] like medical imaging for detection of infected tissues.
& Low scattering- The longer wavelength of THz signals compared to visible light allows
for much lower scattering.
& Intensity- THz signals are much easier to focus and collimate than radio waves.
Thus THz signals can be applied for sensing and imaging purposes. Detection, identification
and characterization of explosives and weapons, hidden under clothes for protecting citizens
and state from organized crime, preventing terrorist acts and responding to natural and man-
made disasters are some of the important areas of probable THz signal application. But there are
certain issues that need to be reviewed before applying them for these purposes. Atmospheric
condition is one of them. Atmospheric attenuation and scattering from atmospheric particulates
are two major concerns of development of sensors in the THz spectral region. Figure 2 shows
the variation of atmospheric attenuation as a function of frequency for different weather
conditions [8]. Figure 2 indicates that the most adverse condition is met in hot tropical
climates. Imaging is a technique in which the reflected signal from the object (also called
signature) is received by a receiver and the image of the reflector is created from this sig-
nature. The reflected signal will be affected by reflective properties of the materials as well as
the frequency of operation. As the frequency increases there will be more diffuse scattering
and resulting in a “natural” image. But higher attenuation at higher frequencies will limit the
range of detection. Imaging in transmission is also one of the upcoming research and appli-
cation areas in which the signal transmitted through the material is analyzed for detection.

2 Terahertz Sources

Although THz frequency band lies in the gap between microwave band and infrared band,
the sources available in these two bands can not be used for THz range [9]. It is difficult to
Int J Infrared Milli Waves (2008) 29:1091–1102 1093

Fig. 2 Atmospheric attenuation at sea level pressures for six different conditions of temperature, humidity,
and atmospheric particulates [8].

fabricate solid state sources in THz range [10] because the size becomes very small leading
to very small power available. Figure 3 shows output power variation of conventional solid
state sources. It can be seen that the efficiency of the sources falls drastically for higher THz
range. The carrier transit time also becomes very short compared to microwave frequency
signals. On the other side, conventional laser sources are not available at THz band because
suitable semiconductors are not available. Recent researches have revealed the fact that
Quantum cascade concept for semiconductor GaAs/AlGaAs heterostructures (Quantum
Cascade laser) can be used for generation of THz signals. A Quantum Cascade laser comprises
a series of thin layers of semiconductors. The thickness of the layers is so small that this is

Fig. 3 Power performance of

different THz sources.
1094 Int J Infrared Milli Waves (2008) 29:1091–1102

referred to as one dimensional multiple quantum well confinement.When one electron passes
through a particular layer it emits a photon and immediately enters the second quantum well .
Typically 25 to 75 active wells are arranged in a QC laser, each at a slightly lower energy level
than the one before–thus producing the cascade effect, and allowing 25 to 75 photons to be
created per electron journey. Quantum cascade laser has been successfully operated between
1.9 THz and 4.8 THz with output power up to 90 mW, single mode operation and narrow
linewidth [11–16]. IMPATT diode, which is a powerful solid state source for mm amd sub-
mm wave frequencies can also be used as a THz source [17–18]. The semiconductor material
for developing IMPATTs should have higher breakdown voltage and higher thermal
conductivity for having high RF power out of it. Wide bandgap SiC meets this criterion
and is the ultimate choice for this. Ref. 17 presents a simulation based study of the dynamic
performance of wide-bandgap 4H-SiC based double drift region (p++-p-n-n++) IMPATT diode
at terahertz frequency (0.7 Terahertz) region. The simulation results show that the power out
of a SiC based IMPATT diode is quite high (2.5×1011 Wm−2) at a frequency of 0.7 THz.
Electro-optic rectification (different frequency mixing) is another process of producing THz
radiation. A semiconductor along with a femtosecond pulse source produces THz radiation. A
time dependent polarization in the THz frequency range is induced by a high electric field
femtosecond pulse. This method can not generate THz frequency signals over broad frequency
bands in THz frequency range. Another type of widely used THz source is Optically Pumped
Terahertz Laser (OPTL). It consists of a grating-tuned carbon dioxide pump laser and a Far-
Infrared (FIR) gas cell mounted in a laser resonator. These systems are smaller and can operate
at several discrete frequencies ranging from 300 GHz to10 THz in time domain THz
spectroscopy and sensing ultrashort laser pulses are generated to produce THz radiation.
A broadband short-pulse terahertz source used in Time Domain Spectroscopy (TDS) is
shown in Fig. 4.
A split antenna, fabricated on a semiconductor substrate is used as a switch. A dc bias is
applied across the two parts of the antenna, and an ultrashort pump-laser pulse (<100 fs) is
focused in the gap in the antenna. The bias–laser pulse combination allows electrons to rapidly
jump the gap, which induces current in the antenna and produces a terahertz radiation. This
radiation is collected and collimated by a hemispherical lens (shown at the bottom side of the
substrate) to produce a THz beam [19]. BWOs are electron tubes that can produce output
at lower end of THz Frequency range. However they require very high magnetic field

Fig. 4 A broadband short-pulse

terahertz source [19]. Femtosecond
pump laser

Collimating lens
Terahertz radiation
Int J Infrared Milli Waves (2008) 29:1091–1102 1095

(∼10 KG). Direct multiplied sources (DM) cannot produce THz signals directly. They take
signals at millimeter wave frequency and multiply them to THz frequency. They can produce
signals with frequency up to 1 THz (approx.). The output power available from them is small
(∼1 μW). These types of sources are mainly used as local oscillators in radio astronomy
applications. Free electron laser (FEL), synchrotron light sources and optical parametric
sources are also used for generation of THz signal. In free electron laser, an electron beam is
accelerated to relativistic speed and it is sent through an array of magnets placed within a
laser cavity. Due to the interaction of the accelerated electron beam with magnetic field a
photon is emitted whose wavelength can be tuned to THz range by changing the electron
beam energy or magnetic field strength. Synchrotron THz radiation from relativistic electrons
have high power (∼W) and broad linewidth [20]. However, FEL and synchrotron THz
sources suffer from limitations in terms of cost and size. In optical parametric process, by
using GaSe, ZnGeP2, GaP, LiNbO3 etc. more than hundreds of watt THz peak power can be
generated. These THz sources also have narrow linewidth and are tunable making them
useful for high resolution spectroscopy [21].

3 Terahertz Antennas

Different antenna structures have been proposed and used for the THz frequency range. In
most of the cases the polarization state of the radiation emitted by THZ antenna has
received less attention. Rudd et al. [22] first reported the measurement of cross-polarized
component of the fields radiated from a THz dipole antenna as shown in Fig. 5. A dipole
antenna situated in a pyramidal horn cavity etched in silicon, as shown in Fig. 8, has been
operated at 0.8 THz (λ=375 μm) [23]. Corner reflector array antennas are widely used in
THz frequencies. An array of four wavelength traveling wave antennas backed by 90°
corner reflectors have been tested at 2.52 THz [24]. Figure 9 shows the configuration of the
antenna. Centrally fed Bow-Tie antennas, which is a flat-plane version of the biconical
antenna can also be used as a THz antenna. These antennas are very wideband in nature. A
3/2 λ bow tie antenna coupled to a MOM (metal oxide metal) diode designed at 28 THz
[25] has the potential for use in arrays of antenna-coupled IR detectors.. A Planar antenna in
the form log-periodic spirals or twin slots or twin dipoles [26], mounted on the back of a
dielectric lens, is a typical configuration that is used in astronomical receiver for sending
signal to a quasi-optical mixer [27]. This structure has the advantage that it can be easily
fabricated along with the mixing device on the same substrate P. J. Burke [28] first
predicted that it is possible to have a nanotube transistor with THz cutoff frequencies. Zeng
et al. first reported [29] the simulated results for carbon nanotube THz antenna array. A

Fig. 5 (a) Schematic of the THz

dipole antenna (b) and its radia- a b
tion pattern. The dashed curve
corresponds to free space radia-
tion pattern and the solid curve
shows the pattern when the
structure is fabricated on a high
dielectric substrate.
1096 Int J Infrared Milli Waves (2008) 29:1091–1102

photoconductive terahertz antenna with radial symmetry has been reported in [30]. Yagi
antennas, consisting of array of dipoles of different lengths, have one driven element, one
reflector and a number of directors. They can be used as optical antennas.
The THz dipole antenna shown in Fig. 5 generates a cross-polarized component of electric
field which is orthogonal to the axis of the dipole. The dipole antenna of length 60 μm is fed
by two strip lines at both the ends. The arrows indicate the flow of current from one of the
strips through the dipole to the other strip. The antenna is fabricated upon low temperature
grown GaAs. The electric field component of the antenna is given by

EQ / sin q cos q sin 2 8 b

q þ sin q cos 2 8 8
b; ð1Þ

Where 8 is measured from x axis. For the s-polarized emission, (s polarization is in the
plane of polarization perpendicular to the surface) the largest peak-to-peak electric field
amplitude is approximately 7% of the p-polarized (in the plane of the surface) emission. The
radiation pattern is distorted by the presence of the dielectric substrate [31]. In ref. [22],this
antennas has been used in THz time domain spectroscopy as a transmitting antenna, which is
also shown in Fig. 4 where the antenna has been coupled with a lens.
Reference [29] discusses about a novel THz antenna made of array of Carbon nanotubes.
Finite length dipole antennas can be formed with CNT. They can be investigated using
Hallen’s-type integral equation. Antenna effect of Carbon nanotubes have been confirmed in
Ref. [32]. As a receiving antenna the effect is maximized when the length of the antenna is
multiple of half-wavelength. Carbon nanotube antennas may be analyzed using transmission
line model. In this model several additional effects are to be considered [33]. In addition to
the magnetic inductance and electrostatic capacitance, two additional components called
quantum capacitance and kinetic inductance must be included in the equivalent circuit. The
wave velocity in a CNT will be modified to

1
Vp ¼ pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ð2Þ
Lk Ctotal

1
where Ctotal ¼ C1q þ C1ES , Cq is the quantum capacitance ,CES is the electrostatic capacitance
and Lk is the kinetic inductance.
As can be seen from Fig. 6(b), that gain improves with increase in the length of the
antenna. Gain can also be increased with increase in the number of elements in the array and
suitably choosing the inter element distance d. The directivity is also good for the antenna
(Fig. 6(c). So the Carbon Nanotube antenna can be properly designed to get sufficient power
radiated or received from it.
Figure 7 shows a photoconductive terahertz antenna with radial symmetry, which has been
reported in [30]. In quasi-optical configurations, it is difficult to design waveguides or coaxial
waveguides for carrying terahertz pulses. This is due to the fact that lowest-order (TEM)
mode of such guides possesses a radial electric field polarization. Here, a novel cylindrically
symmetric substrate antenna design which is compatible with THz time domain spectroscopy
is presented. Using theoretical analysis and finite elements method, properties of the radiated
far-field pattern has been explored and it has been shown that the field possesses the desired
radial polarization pattern. Design of this antenna is based on Finite Element Method (FEM)
model. Neglecting the effect of the dielectric substrate, the fields radiated from the antenna
can be thought of as a superposition of those from a large number of dipoles, each pointing
radially away from the origin. The resulting field can be easily computed, since the field from
each one of these point dipoles can be found by simply shifting and rotating a classical far-
Int J Infrared Milli Waves (2008) 29:1091–1102 1097

Fig. 6 (a) Carbon Nanotube Antenna array (b) variation of gain with diameter and length of Carbon
Nanotube. (c)Directivity pattern of the antenna for d=λ/8 (inside pattern) and d=λ/40(outside pattern).

field dipole pattern. Then the antenna is fabricated on a substrate of high dielectric constant
€=12.25, the approximate value for GaAs.
The integrated horn antenna [23] comprises of two stacked wafers where the horn cavity is
etched on the front wafer. A dipole antenna suspended in a 1 pm thin dielectric is placed at
the back side of the front wafer and the back wafer acts as a reflecting structure (Fig. 8). The
horn antenna is treated as a number of stepped waveguides connected to each other and the
Green’s function for the dipole antenna is obtained. The electric field inside the horn may be
written in terms of the electric current on the strip dipole as shown below:
Z
E ¼ Sd G:Jdx0 dy0 ð3Þ

where G is the modified dyadic Green’s function for the structure and Sd is the surface of the
strip dipole. The green's function is used for calculation of input impedance and resonant
properties of the feeding strip. Results show that this antenna is a very high efficiency
antenna with a very high gain. This may solve the power problem for THz antennas. The
theoretical and experimental results for the antenna has been presented in Ref. [34, 35]. A
256-element imaging array [36] of this kind of integrated horn antenna has been fabricated
1098 Int J Infrared Milli Waves (2008) 29:1091–1102

Fig. 7 (a) The proposed radially

symmetric antenna and (b) it’s
far field radiation pattern.

and tested at 802 GHz. The array period is 500 pm, and the total array size is 8×8 mm2. The
radiation patterns of the antenna array have been measured at 802 GHz (Fig. 9b), showing a
directivity12.3± 0.2dB for 1.41 λ horn aperture. The measured patterns are symmetrical with
a main-beam efficiency of 88% in a 100° beamwidth.
Corner cube antenna consisting of a traveling wave antenna backed by a corner reflector
is extensively used in submillimeter-wave receivers [37–42]. The integrated corner-cube
Int J Infrared Milli Waves (2008) 29:1091–1102 1099

Fig. 8 (a) An integrated horn

antenna (b) theoretical and ex-
perimental E-plane & H-plane
pattern measured at 802 GHz for
a 256 element two dimensional
horn array.

antenna consists of a cavity etched in silicon wafers, inside which a traveling-wave antenna
is suspended on a 1-μm dielectric membrane formed by depositing a 3-layer Si0,-Si,N4,
(Fig. 9(a)). The membrane electrical thickness is 0.02 λ at 3 THz, so the traveling-wave
antenna effectively radiates in free space at 119 μm. Figure 9(b) shows that this antenna has
a high gain and can work efficiently at low power level
Length of the antenna and the distance of the antenna from the apex of corner reflector
are the design parameters in this design. This antenna has the advantage that it is fully
monolithic and is easily reproducible for array applications.
1100 Int J Infrared Milli Waves (2008) 29:1091–1102

Fig. 9 (a) A corner reflector

imaging array (b) and its radia-
tion pattern measured at 3 THz.

4 Conclusion

THz sources and THz antennas are two critical areas where advances of technology are
required. Sources are also to be designed that can produce high power at an affordable cost.
From the information available from different surveys and investigations it can concluded
that conventional electronics fails to produce THz frequency signals efficiently. The available
technology is very costly and to work with THz signals, one needs to be well funded. Among
the different types of sources reviewed Quantum Cascade Laser works best for generation of
THz signals. However extending this concept below 10 THz is a challenge. Among the
semiconductors available Wide band gap SiC is a good choice for fabricating solid state
sources at THz frequencies. Research on IMPATT THz sources is still in the simulation level.
Because of its huge scope of applications, new and simple antenna configurations are
required to be designed in THz frequency region which will be ultrawideband as well as easily
integrable with transmitters and receivers. In THz region the size of the antenna becomes so
small that it becomes difficult to fabricate them. Each of the various types of THz antennas
Int J Infrared Milli Waves (2008) 29:1091–1102 1101

reviewed in this paper possesses some unique feature. Figure 5 gives the simplest design for
generation of THz signal- a dipole antenna. Carbon nanotube is a technology which has many
potential applications. Ref. 29 shows that they can be used in THz frequency also. But the
research is still in nascent stage. Experimental results are not yet available. Both integrated
horn antenna and corner cube antenna are part of an integrated monolithic receiver. These
structures are very compact and leave sufficient space for the electronic circuitry of the
receiver. GaAs or Si is the obvious choice for the basic substrate of most of the antennas. All
the antennas can be used as an array thus improving gain of the antenna. Also in optical
domain, the antenna concept is new. An optical antenna is a device that efficiently couples the
energy of free space radiation to a confined region of subwavelength size. In recent years
optical antennas has acquired great interest because a number of interesting applications have
emerged. For example, it is found that the radiative decay rate of fluorescent dye molecules
are strongly enhanced by the presence of an optical nanoantenna [43]. Dipoles, monopoles,
bowties, patches, and Yagi–Uda arrays are some of the structures that have been investigated
in optical regime. Optical antennas have become possible in large part due to recent advances
in fabrication technology, allowing sub-100 nm structures to be routinely produced.

References

1. D. L. Woolard, W. R. Loerop, and M. S. Shur, Eds., Terahertz Sensing Technology, Singapore: World
Scientific, 1, (2003), Electronic Devices and Advanced Systems Technology.
2. D. L. Woolard, W. R. Loerop, and M. S. Shur Eds., Terahertz Sensing Technology. Singapore: World
Scientific, 2, (2003), Emerging Scientific Applications and Novel Device Concepts.
3. D. Mittleman Ed., Sensing With Terahertz Radiation, ser. Opt. Sci., Berlin Berlin, Germany: Springer-
Verlag, (2003).
4. F. C. De Lucia, D. T. Petkie, R. K. Shelton, S. L. Westcott, and B. N. Strecker, THz + ‘X’—a Search for
New Approaches to Significant Problems, Proc. SPIE., 5790, (2005), pp. 219–230.
5. Dwight L. Woolard, Elliott R. Brown, Michael Pepper, And Michael Kemp, Terahertz Frequency
Sensing and Imaging : A Time of Reckoning Future Application ?, Proceedings of The IEEE, 93, No. 10,
(2005) pp.1722-1743.
6. P. H. Siegel, Terahertz Technology in Biology and Medicine. IEEE Transaction on Microwave Theory
and Techniques. 52, 2438 (2004).
7. P. H. Siegel, Terahertz Technology. IEEE Transactions on Antennas and Propagation 50, 912 (2002).
8. R. Appleby, and H. B. Wallace, Standoff Detection of Weapons and Contraband in the100 GHz to 1 THz
Region. IEEE Transactions On Antennas And Propagation. 55(), (11)), 2944–2956 (2007).
9. A. G. Davies, E. H. Linfield, and M. B. Johnston, The Development Of Terahertz Sources and Their
Applications. Phys. Med. Biol. 47, 3679–3689 (2002).
10. J. M. Chamberlain, R. E. Miles, C. E. Collins and D. P. Steenson, New Directions in Terahertz
Technology, ed. J M Chamberlain and R E Miles (NATO ASI Series, Kluwer) 1997.
11. B. S. Williams, S. Kumar, Q. Hu, and J. L. Reno, Operation of Terahertz Quantum-Cascade Lasers at
164 K in Pulsed Mode and at 117 K In Continuous-Wave Mode. Opt. Express 13, 3331–3339 (2005).
12. S. Barbieri, J. Alton, H. E. Beere, J. Fowler, E. H. Linfield, and D. A. Ritchie, 2.9 THz Quantum
Cascade Lasers Operating up to 70 K in Continuous Wave. Appl. Phys. Lett. 85, 1674–1676 (2004).
13. L. Ajili, G. Scalari, J. Faist, H. E. Beere, J. Fowler, E. H. Linfield, D. A. Ritchie, and A. G. Davies, High
Power Quantum Cascade Lasers Operating at λ≈87 μm and 130 μm. Appl. Phys. Lett. 85, 3986–3988 (2004).
14. A. Tredicucci, L. Mahler, T. Losco, J. Xu, C. Mauro, R. Köhler, H. E. Beere, D. A. Ritchie, and E. H.
Linfield, Advances in THz Quantum Cascade Lasers: Fulfilling The Application Potential, in Novel In-
Plane Semiconductor Lasers IV, C. Mermelstein, D. P. Bour, eds., Proc. SPIE, 5738, (2005), 146–158.
15. L. Mahler, R. Köhler, A. Tredicucci, F. Beltram, H. E. Beere, E. H. Linfield, D. A. Ritchie, and A. G.
Davies, Single-mode Operation of Terahertz Quantum Cascade Lasers with Distributed Feedback
Resonators. Appl. Phys. Lett. 84, 5446–5448 (2004).
16. A. Barkan, F. K. Tittel, D. M. Mittleman, R. Dengler, P. H. Siegel, G. Scalari, L. Ajili, J. Faist, H. E.
Beere, E. H. Linfield, A. G. Davies, and D. A. Ritchie, Linewidth and Tuning Characteristics of
Terahertz Quantum Cascade Lasers. Opt. Lett. 29, 575–577 (2004).
1102 Int J Infrared Milli Waves (2008) 29:1091–1102

17. M. Mukherjee, N. Mazumder, and Sitesh Kumar Roy, Prospects of 4H-SiC Double Drift Region
IMPATT Device as a Photo-Sensitive Terahertz Frequency Regime, Hindawi Publishing Corporation,
Active and Passive Electronic Components, Volume 2008, Article ID 275357, 9 pages doi:10.1155/2008/
275357
18. M. Mukherjee, N. Mazumder, S. K. Roy, and K. Goswami, GaN IMPATT Diode: a Photo-Sensitive High
Power Terahertz Source. Semiconductor Science and Technology 22(12), 1258–1267 (2007) (10).
19. E. R. Mueller, Terahertz Radiation: Applications and Source, The Industrial Physicist, American Institue
of Physics, (2003), 27–29.
20. G. L. Carr, M. C. Martin, W. R. Mckinney, K. Jordon, G. R. Neil, and G. P. Williams, High-Power
Terahertz Radiation From Relativistic Electrons. Nature 420, 153–156 (2002).
21. K. Kawase, J. Shikata, and H. Ito, Terahertz Wave Parametric Source. J. Phys. D: Appl. Phys. 34, R1–
R14 (2001).
22. J. V. Rudd, J. L. Johnson, and D. M. Mittleman, Quadrupole Radiation from Terahertz Dipole Antennas.
Opt. Letters. 25(20), 1556–1558 (2000).
23. C. Fumeaux, G. D. Boreman, W. Herrmann, F. K. Neubuhi, and H. Rothuizen, Spatial Impulse Response
of Lithographic Infrared Antennas. Appl. Phys. Lett. 38, 37–46 (1999).
24. S. S. Gearhart, C. C. Ling, G. M. Rebeiz, H. Davee, and G. Chin, Integrated 119-μm Linear Corner-
Cube Array. IEEE Microwave and Guided Wave Letters 1, 155–157 (1991).
25. G. M. Rebeiz, L. F. B. Katehi, W. Y. Ali-Ahmad, G. V. Eleftheriadws, and C. C. Ling, Integrated Horn
Antennas for Millimeter-Wave Applications. IEEE Antenna and Propagation Magazine. 34, 7–16 (1992).
26. P. Goldsmith, Quasioptical Systems, IEEE Press, (1998)169.
27. M. Bin, Ph.D thesis, Cal.Inst.Tech., (1997).
28. P. J. Burke, Carbon Nanotube Devices for GHz to THz Applications, Proceedings of SPIE, 5593 (SPIE,
Bellingham, WA, 2004),pp.52-61.
29. Y. Lan, B. Zeng, H. Zhang, B. Chen, and Z. Yang, Simulation of Carbon Nanotube THz Antenna Array.
International Journal of Infrared and Millimeter Waves. 27(6), 871–877 (2006).
30. J. A. Deibel, M. D. Escarra, and D. M. Mittleman, Photoconductive Terahertz Antenna with Radial
Symmetry, Quantum Electronics and Laser Science Conference (QELS), (2005) pp. 1239–1241.
31. P. U. Jepsen, THz Radiation Patterns from Dipole Antennas and Guided Ultrafast Pulse Propagation, M.S.
Thesis (Odense Universitet, Odense, Denmark, 1994).
32. G. W. Hanson, Fundamental Transmitting Properties of Carbon Nanotube Antennas. IEEE Transactions
on Antennas and Propagation 53(11), 3426–3435 (2005).
33. P. J. Burke, S. Li, and Z. Yu, Quantitative Theory of Nanowire and nanotube Antenna Performance.
IEEE Transactions on Nanotechnology 5(4), 314–334 (2006).
34. W. Y. Ali-Ahmad, G. V. Eleftheriades, L. P. Katehi, and G. M. Rebeiz, Millimeter-Wave Integrated-Horn
Antennas, Part 1-Theory. IEEE Transactions on Antennas and Propagation 39(11), 1575–1581 (1991).
35. W. Y. Ali-Ahmad, G. V. Eleftheriades, L. P. Katehi, and G. M. Rebeiz, Millimeter-Wave Integrated-Horn
Antennas, Part II- Experiment. IEEE Transactions on Antennas and Propagation 39(11), 1582–1586 (1991).
36. W. Y. Ali-Ahmad, G. M. Rebeiz, H. Davee, and G. Chin, 802 GHz Integrated Horn Antennas Imaging
Array. Intl. J. Infrared Millimeter Waves 12, 481–486 (1991).
37. H. R. Fetterman et al., Far-IR Heterodyne Radiometric Measurements with Quasi-Optical Schottky
Diode Mixers. Appl. Phys. Lett. 33, 151–154 (1978).
38. E. Sauter, G. V. Schultz, and R. Wohleben, Antenna Pattern of an Open Structure Mixer at a Submillimeter
Wavelength and of Its Scaled Model. Int. J. Infrared and Millimeter Waves 5(4), 451–463 (1984).
39. J. Zmuidzinas, A. L. Betz, and R. T. Boreiko, A Corner-Reflector Mixer for Far-Infrared Wavelengths.
Infrared Phys. 29, 119–131 (1989).
40. H. P. Roser, E. J. Dunven, R. Wattenbach, and G. V. Schultz, Investigation of a Heterodyne Receiver with
Open Structure Mixer at 324 and 693 GHz. Int. J. Idrared and Millimeter Waves. 5(3), 301–314 (1984).
41. W. M. Kelly, M. J. Gans, and J. G. Eivers, Modeliing the Response of Quasi-Optical Comer Cube Mixers,
Instrumentation for Submillimeter Spectroscopy, E. Kollberg, Ed., Proc. SPIE. 598, 72–78 (1986).
42. E. N. Grossman, The Coupling of Submillimeter-Wave Corner-Cube Antenna to Gaussian beams.
Infrared Phys. 29, 875 (1989).
43. G. W. Hanson, and P. de Maagt, Guest Editorial for the Special Issue on Optical and THz Antenna
Technology. IEEE Transactions On Antennas And Propagation 55(11), 2942–2943 (2007).