Dispersion characteristics of optically excited coplanar striplines: pulse propagation

Phatak, Dhananjay S.; DeFonzo, Alfred P.

doi:10.1109/22.54935

Cited by 43 publications

(14 citation statements)

References 18 publications

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“…Physically, as the operating frequency increases, the dielectric loss, radiation loss, and ohmic loss of CPWs have significant effects on the pulse-waveform distortion [7,8]. In particular, Liao and Ponchak et al have presented two sets of new empirical formulas to predict the ohmic loss for CPWs [8,9], respectively, which are characterized by different conductivities and thicknesses of the center strip and ground planes over a wideband frequency range.…”

Section: Introductionmentioning

confidence: 99%

Lossy effects on the transient propagation in LTCC coplanar waveguides (CPWs)

Wang

Guo

Dong

et al. 2003

Micro & Optical Tech Letters

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The effects of dielectric, radiative leakage and ohmic losses in CPWs on the propagation of Gaussian and sinusoidally modulated Gaussian pulses are investigated. These CPWs are assumed to be fabricated on a single‐layer low‐temperature co‐fired ceramic (LTCC) substrate. It is shown that, based on the improved empirical formula for accurate prediction of the ohmic attenuation constant presented by Liao et al., the lossy effects in LTCC CPWs are dominated by the ohmic loss of the center and ground conductive planes in the frequency range up to 40 GHz. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 94–97, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11137

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Section: Introductionmentioning

confidence: 99%

Lossy effects on the transient propagation in LTCC coplanar waveguides (CPWs)

Wang

Guo

Dong

et al. 2003

Micro & Optical Tech Letters

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“…Other groups have studied the loss mechanisms involved in the propagation of ultrashort electrical pulses on coplanar transmission lines [29]- [31]. It is generally agreed that the main absorption loss at lower frequencies ( 200 GHz) is through conduction losses in the lines ( , where is the frequency), whereas the high-frequency absorption ( ) is predominantly due to Cherenkov radiation.…”

Section: Cherenkov Shock Wave Radiation From Transmission Linesmentioning

confidence: 99%

Optoelectronic characterization of transmission lines and waveguides by terahertz time-domain spectroscopy

Grischkowsky

2000

IEEE J. Select. Topics Quantum Electron.

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Abstract-An overview is presented of an experimental search for an ultrawide-band transmission channel with low dispersion and loss. Such a terahertz (THz) interconnect will soon be required by the insatiable demand for higher speed devices and wider bandwidth communication. Starting with the early optoelectronic generation and detection of single-mode, subpicosecond electrical pulses on coplanar transmission lines, their complete characterization by THz time-domain spectroscopy (THz-TDS) is described. The consequent discovery of phase-coherent Cherenkov radiation in the form of an electromagnetic shock wave from these propagating electrical pulses is discussed together with its dominant role in the large measured propagation loss of these pulses. Various techniques to reduce this radiation are presented. The importance of dielectric materials characterization is explained and illustrated by THz-TDS measurements of high substrates. Newly obtained THz waveguide results are presented and compared to the performance of coplanar transmission lines.

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“…However, for high values of CPS impedance the lines become very narrow, which means their current carrying capacity decreases and ohmic loss increases. Literature describing propagation of THz signals on CPS and CPW focuses a lot of attention on radiation loss [78,79,80,81]. However, the radiation loss is only high in these structures because the dimensions of the waveguide are so large compared to the wavelength of the THz radiation and the substrates are so small compared to the wavelength.…”

Section: Coplanar Stripsmentioning

confidence: 99%

Distributed photomixers

Duerr

McIntosh

Verghese³

2000

Conference on Lasers and Electro-Optics (CLEO 2000). Technical Digest. Postconference Edition. TOPS Vol.39 (IEEE Cat. No.00CH37

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Although the terahertz domain has been explored scientifically, components, especially sources, are needed to enable further exploration of the frequency range. A photomixer generates coherent THz radiation through optical heterodyne down-conversion. A terahertzfrequency beat signal on an optical carrier illuminates an ultrafast photoconductor, modulating the conductance. The time-varying conductance together with a constant voltage bias generates time-varying current at the beat frequency. Low-temperature-grown gallium arsenide (LTG-GaAs) is the photoconductive material of choice, because its short carrier lifetime allows the conductance to be efficiently modulated at THz frequencies.The distributed photomixer described in this thesis is a new style of LTG-GaAs photomixer which uses an optical waveguide to couple the beat signal to an active area which is large relative to the terahertz wavelength. This large, traveling-wave mode active area distributes the heat load from absorbed optical power and ohmic heating from photocurrent and avoids the ¡ £ ¢ rolloff associated with a lumped-element photomixer's intrinsic capacitance and the load resistance. The distributed photomixer structure consists of coplanar strips (CPS) fabricated on top of a dielectric strip-loaded waveguide that guides the optical beat. The conductance of a thin layer of LTG-GaAs between the CPS and optical guide is modulated by the weakly coupled optical signal. The THz conductance wave between the dc-biased CPS creates a THz electromagnetic wave which propagates along the CPS. To velocity match the THz and optical waves, the CPS are periodically loaded with thin electrodes that add a small shunt capacitance to the line. The CPS are terminated in a planar antenna that radiates the THz wave.This thesis describes the design, fabrication, and testing of waveguide-coupled distributed photomixers. The photomixers demonstrated in this thesis operated in travelingwave mode and produced 100 nW of power at 0.3 THz and the power output rolled off at 6 dB/octave until 1.4 THz. A model which qualitatively and quantitatively predicts the device performance as a function of frequency, illumination and voltage bias is developed. A general design methodology, detailed discussion of fabrication steps and possible methods to increase output power are also presented.

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Dispersion characteristics of optically excited coplanar striplines: pulse propagation

Cited by 43 publications

References 18 publications

Lossy effects on the transient propagation in LTCC coplanar waveguides (CPWs)

Lossy effects on the transient propagation in LTCC coplanar waveguides (CPWs)

Optoelectronic characterization of transmission lines and waveguides by terahertz time-domain spectroscopy

Distributed photomixers

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