Continuous THz-wave generation using antenna-integrated uni-travelling-carrier photodiodes

Itô, Hiroshi; Nakajima, Fumito; Furuta, Tadaomi; Ishibashi, Tadao

doi:10.1088/0268-1242/20/7/008

Cited by 154 publications

(84 citation statements)

References 26 publications

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“…The RC 3 dB frequency of the emitter was calculated from geometry to 0.14 THz when attached to a broadband spiral antenna. The total 3 dB frequency is comparable to that of the UTC diode given by Ito et al, 90 which is a factor of 6 smaller. Using improved recombination diodes, such as the one shown in Fig.…”

Section: -20supporting

confidence: 52%

“…This concept is used in the two approaches discussed in Secs. II D 5 and II D 6, uni-traveling-carrier (UTC) photodiodes 90 and n-i-pn-i-p superlattice photomixers with ballistic electron transport. 91 In both cases only electrons contribute to the current [strictly speaking, the fraction ð1 À Dz=2d i Þ], and the hole contribution (strictly speaking, the fraction Dz=2d i ) becomes negligible.…”

Section: Realistic Transit Time Roll-off Of P-i-n Diodesmentioning

confidence: 99%

“…v sat . UTC diodes 90 have been operated with current densities around 100 kA=cm 2 , about an order of magnitude higher than conventional p-i-n diodes. 94 c. Ballistic diode.…”

Section: Influence Of Screening At High Current Densitiesmentioning

confidence: 99%

“…The doping was abruptly changed from 2 Á 10 18 cm À3 to 2 Á 10 17 cm À3 , resulting in a conduction band offset of 60 meV. An excellent review of UTC diodes is given by Ito et al 90 …”

Section: Uni-traveling-carrier Diode Designsmentioning

confidence: 99%

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Tunable, continuous-wave Terahertz photomixer sources and applications

Preu

Döhler

Malzer

et al. 2011

Journal of Applied Physics

424

293

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Realization of gigahertz-frequency impedance matching circuits for nano-scale devices Appl. Phys. Lett. 101, 053108 (2012) Synchronization of a renewable energy inverter with the grid J. Renewable Sustainable Energy 4, 043103 (2012) Monolithic high-temperature superconducting heterodyne Josephson frequency down-converter Appl. Phys. Lett. 100, 262604 (2012) Generation of pure phase and amplitude-modulated signals at microwave frequencies Rev. Sci. Instrum. 83, 064705 (2012) Additional information on J. Appl. Phys. This review is focused on the latest developments in continuous-wave (CW) photomixing for Terahertz (THz) generation. The first part of the paper explains the limiting factors for operation at high frequencies $ 1 THz, namely transit time or lifetime roll-off, antenna (R)-device (C) RC rolloff, current screening and blocking, and heat dissipation. We will present various realizations of both photoconductive and p-i-n diode-based photomixers to overcome these limitations, including perspectives on novel materials for high-power photomixers operating at telecom wavelengths (1550 nm). In addition to the classical approach of feeding current originating from a small semiconductor photomixer device to an antenna (antenna-based emitter, AE), an antennaless approach in which the active area itself radiates (large area emitter, LAE) is discussed in detail. Although we focus on CW photomixing, we briefly discuss recent results for LAEs under pulsed conditions. Record power levels of 1.5 mW average power and conversion efficiencies as high as 2 Â 10 À3 have been reached, about 2 orders of magnitude higher than those obtained with CW antenna-based emitters. The second part of the paper is devoted to applications for CW photomixers. We begin with a discussion of the development of novel THz optics. Special attention is paid to experiments exploiting the long coherence length of CW photomixers for coherent emission and detection of THz arrays. The long coherence length comes with an unprecedented narrow linewidth. This is of particular interest for spectroscopic applications, the field in which THz research has perhaps the highest impact. We point out that CW spectroscopy systems may potentially be more compact, cheaper, and more accurate than conventional pulsed systems. These features are attributed to telecom-wavelength compatibility, to excellent frequency resolution, and to their huge spectral density. The paper concludes with prototype experiments of THz wireless LAN applications. For future telecommunication systems, the limited bandwidth of photodiodes is inadequate for further upshifting carrier frequencies. This, however, will soon be required for increased data throughput. The implementation of telecom-wavelength compatible photomixing diodes for down-conversion of an optical carrier signal to a (sub-)THz RF signal will be required.

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Section: -20supporting

confidence: 52%

Section: Realistic Transit Time Roll-off Of P-i-n Diodesmentioning

confidence: 99%

“…v sat . UTC diodes 90 have been operated with current densities around 100 kA=cm 2 , about an order of magnitude higher than conventional p-i-n diodes. 94 c. Ballistic diode.…”

Section: Influence Of Screening At High Current Densitiesmentioning

confidence: 99%

“…The doping was abruptly changed from 2 Á 10 18 cm À3 to 2 Á 10 17 cm À3 , resulting in a conduction band offset of 60 meV. An excellent review of UTC diodes is given by Ito et al 90 …”

Section: Uni-traveling-carrier Diode Designsmentioning

confidence: 99%

See 2 more Smart Citations

Tunable, continuous-wave Terahertz photomixer sources and applications

Preu

Döhler

Malzer

et al. 2011

Journal of Applied Physics

424

293

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show abstract

“…In particular, to be used as a local oscillator in communications systems the THz source should produce stable output power > 10 µW [8,11]. Among the various techniques being pursued [6,8,11,12,13] electrical down conversion of optical microwave sources in a suitable photomixer [6,11,12] are appealing due to the easy availability of tunable, narrow-linewidth, and stable solid state lasers. However, until now the output power from these photomixers is limited to < 10 µW in the cru- cial THz range.…”

mentioning

confidence: 99%

Enhancing the photomixing efficiency of optoelectronic devices in the terahertz regime

Pilla

2007

Applied Physics Letters

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A method to reduce the transit time of majority of carriers in photomixers and photo detectors to < 1 ps is proposed. Enhanced optical fields associated with surface plasmon polaritons, coupled with velocity overshoot phenomenon results in net decrease of transit time of carriers. As an example, model calculations demonstrating > 280× (or ∼2800 and 31.8 µW at 1 and 5 THz respectively) improvement in THz power generation efficiency of a photomixer based on Low Temperature grown GaAs are presented. Due to minimal dependence on the carrier recombination time, it is anticipated that the proposed method paves the way for enhancing the speed and efficiency of photomixers and detectors covering UV to far infrared communications wavelengths (300 to 1600 nm).Recent experimental observation of extraordinary optical transmission through a normal metal film having subwavelength holes[1] has generated intense interest in harnessing the underlying physics for photonic applications. It is widely believed that quasi two-dimensional electromagnetic excitations tightly bound to the metal surface known as Surface Plasmon Polaritons (SPPs) are responsible for the observed near field enhancement of the optical radiation. Exponential decay of field components arising from SPPs (penetrating ∼100, ∼10 nm in dielectric and metal respectively), make them highly attractive for miniature photonic circuits and devices [2]. Currently, several potential applications of SPPs are being explored including wave guiding [3] and near-field microscopy [4]. However, application of SPPs to enhance the speed and efficiency of photo detectors or photomixers has not been attempted due to the complexity of underlying physics and optimal device designs involving complicated dielectric-metal structures.In this letter we propose a simple interdigitated metal structure embedded in a suitable semiconductor material to harness SPPs for improving the speed and efficiency of photomixers and detectors. Such a device can be realized with the existing material growth techniques [5]. As an example, we demonstrate via model calculations, significant (> 280×) improvement in the efficiency of a THz photomixer based on Low Temperature grown GaAs (LT-GaAs). Microwave to THz radiation sources in the 0.1 to 10 THz are being extensively studied for their application in communications, medical imaging, and spectroscopy [6,7,8,9,10]. For many applications-compact, narrow-linewidth, widely tunable continuous wave sources are necessary. In particular, to be used as a local oscillator in communications systems the THz source should produce stable output power > 10 µW [8,11]. Among the various techniques being pursued [6,8,11,12,13] electrical down conversion of optical microwave sources in a suitable photomixer [6,11,12] are appealing due to the easy availability of tunable, narrow-linewidth, and stable solid state lasers. However, until now the output power from these photomixers is limited to < 10 µW in the cru- . When the top and bottom interdigitated structures in (b) are con...

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