Radiation field screening in photoconductive antennae studied via pulsed terahertz emission spectroscopy

Loata, G.; Thomson, Mark D.; Löffler, Thomas; Roskos, Hartmut G.

doi:10.1063/1.2823590

Cited by 74 publications

(53 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…From Figure 6 it can be noted that there is an amplitude increment in the THz pulse shape at higher excitation densities due to an increment in the density of photo-carriers at the PC gap. The saturation behavior reported in experimental works (Loata, Thomson, Loffler, & Roskos, 2007;Tani et al, 1997), that is presented at high fluences of photo-generated carriers in photoconductive antennas is not evident in the Figure 6 because screening effects are not included in the simulation, therefore the results are valid only for low laser power levels. The smallest optical power level at which the PC antenna generates a pulse of photocurrent is below 20mW, where the peak current of the pulse shape is reduced at 0.09µA.…”

Section: Multi-physics Simulation Of Pc Antennamentioning

confidence: 88%

Simulation of photoconductive antennas for terahertz radiation

Paredes

Ávila

2015

ing.inv.

View full text Add to dashboard Cite

Simulation of terahertz (THz) emission based on PC antennas imposes a challenge to couple the semiconductor carrier phenomena, optical transport and the THz energy transport. In this paper a Multi-physics simulation for coupling these phenomena using COMSOL Multi-physics 4.3b is introduced. The main parameters of THz photoconductive (PC) antenna as THz emitter have been reviewed and discussed. The results indicate the role of each parameter in the resulting photocurrent waveform and THz frequency: The radiated THz photocurrent waveform is determined by the photoconductive gap (the separation between the metallic electrodes), the incident laser illumination and the DC excitation voltage; while the THz frequency depends on the dipole length. The optimization of these parameters could enhance the emission. The simulations extend the advance of compact and cost-effective THz emitters.Keywords: Multi-physics simulation, photoconductive antennas, semiconductor physics, electromagnetics. RESUMENLa emisión de Terahertz (THz) empleando antenas fotoconductoras representa un reto de simulación en la integración de los fenó-menos de transporte en semiconductores, de óptica y de transporte de energía por radiación THz. En el presente artículo se propone una simulación Multi-Física para integrar estos fenómenos utilizando COMSOL Multiphysics 4.3b. Los principales parámetros de las antenas fotoconductoras empleadas como emisores de THz son estudiados. Los resultados de la simulación demuestran cómo estos parámetros inciden en la fotocorriente generada y en la frecuencia de radiación THz: la abertura fotoconductora (la separación de los electrodos metálicos de la antena), la potencia promedio del láser incidente y el voltaje de polarización, determinan la forma de onda de la fotocorriente generada; mientras que la longitud del dipolo determina la frecuencia de radiación. La emisión de las antenas fotoconductoras puede mejorarse optimizando estos parámetros. Esta simulación es útil para el diseño e implementación de antenas fotoconductoras como emisores de THz de diseño compacto y bajo costo.Palabras clave: Antena fotoconductora, simulación multi-física, electromagnetismo, física de semiconductores.

show abstract

Section: Multi-physics Simulation Of Pc Antennamentioning

confidence: 88%

Simulation of photoconductive antennas for terahertz radiation

Paredes

Ávila

2015

ing.inv.

View full text Add to dashboard Cite

show abstract

“…For pulsed operation, however, the radiated field may cause strong screening of the accelerating DC field. 68,114 In the schematic shown in Fig. 1(a), the direction of the DC electric field in the active layer responsible for the acceleration of the photogenerated carriers had not been specified.…”

Section: F Detailed Discussion Of Large Area Emittersmentioning

confidence: 99%

“…Trapped charge carriers are responsible for space charge screening but do not contribute to the THz current. There is evidence that the recombination takes place on a much longer time scale (i.e., 10 ps to several ns 66,68 ) than the trapping time, which is shorter than 1 ps for high-quality material. Within the fs and THz community, however, the trapping time is referred to as s rec as it is responsible for reducing carrier contributions to the current.…”

Section: Thermal and Electrical Optimizationmentioning

confidence: 99%

“…The total power obtained by integrating overall frequency components is approximately 35 mW, close to the reported 1.5 mW average power. For the intensities and carrier densities the authors used, we also expect some degradation of the THz power due to feedback of the local THz field on the current (radiation screening) 68 and Coulomb screening, 114 explaining the remaining difference.…”

Section: Laes With Surface-parallel Electric Fieldmentioning

confidence: 99%

See 1 more Smart Citation

Tunable, continuous-wave Terahertz photomixer sources and applications

Preu

Döhler

Malzer

et al. 2011

Journal of Applied Physics

428

293

View full text Add to dashboard Cite

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.

show abstract

“…3(a)]. This is because of the carrier screening effect [25] that impacts the plasmonic photomixer more than the conventional photomixer at high optical pump powers [8]. In the absence of the carrier screening effect at very low optical pump power levels, two orders of magnitude higher terahertz power levels are expected from the plasmonic photomixer [8,9].…”

mentioning

confidence: 99%

Plasmonics enhanced photomixing for generating quasi-continuous-wave frequency-tunable terahertz radiation

et al. 2014

View full text Add to dashboard Cite

We experimentally demonstrate an order of magnitude enhancement in the quasi-continuous-wave radiated power from a photomixer with plasmonic contact electrodes in comparison with an analogous conventional photomixer without plasmonic contact electrodes in the 0.25-2.5 THz frequency range when pumped at an optical wavelength of 1550 nm. The significant efficiency enhancement results from the unique capability of the plasmonic contact electrodes to reduce the average transport path of photocarriers to the device contact electrodes, increasing the ultrafast photocurrent that drives the terahertz antenna.

show abstract

Radiation field screening in photoconductive antennae studied via pulsed terahertz emission spectroscopy

Cited by 74 publications

References 21 publications

Simulation of photoconductive antennas for terahertz radiation

Simulation of photoconductive antennas for terahertz radiation

Tunable, continuous-wave Terahertz photomixer sources and applications

Plasmonics enhanced photomixing for generating quasi-continuous-wave frequency-tunable terahertz radiation

Contact Info

Product

Resources

About