A Terahertz Photomixing Spectrometer: Application to SO2Self Broadening

Pine, A. S.; Suenram, R. D.; Brown, E. R.; McIntosh, K. A.

doi:10.1006/jmsp.1996.0006

Cited by 104 publications

(64 citation statements)

References 19 publications

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“…(7) and Eq. (8). The generation rate in an absorbing layer with thickness d, absorption coefficient a, and a surface reflection coefficient R is given by the product of incident photons per second, P L ðtÞ=ðhm 0 Þ and the external quantum efficiency, g ext , is deposited on a semi-insulating substrate.…”

Section: Transport and Rc Roll-offmentioning

confidence: 99%

“…6 The THz range covers the energy range for molecular rotation of polar molecules and librations of macromolecules. Because rotation spectra with many narrow characteristic lines in this frequency range represent highly selective fingerprints of molecules, [7][8][9] including (large) organic molecules, [10][11][12][13] high-resolution THz absorption spectroscopy is very appealing for chemical composition analysis, even down to the parts-per-million range. 14 In combination with imaging techniques-in particular by transmission or reflection scanningthe strong spectral sensitivity of the absorption allows for pictures that isolate certain materials or substances, 15 a property of interest to medicine, biology, and industrial production processes.…”

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confidence: 99%

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Tunable, continuous-wave Terahertz photomixer sources and applications

Preu

Döhler

Malzer

et al. 2011

Journal of Applied Physics

432

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: Transport and Rc Roll-offmentioning

confidence: 99%

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confidence: 99%

Tunable, continuous-wave Terahertz photomixer sources and applications

Preu

Döhler

Malzer

et al. 2011

Journal of Applied Physics

432

293

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“…By substituting the MIM diode by a modern photo mixer, THz radiation can be produced as a beat frequency of two dye lasers in the visible region (Pine et al 1996). The spectral purity and stability of the output radiation depend on those of the parent lasers.…”

Section: Fir Lasermentioning

confidence: 99%

THz and Submillimeter‐wave Spectroscopy of Molecular Complexes

Tanaka

Harada

Yamada

2011

Handbook of High‐resolution Spectroscopy

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This article reviews the recent progress of terahertz (THz) and submillimter‐wave (SMMW) spectroscopy in the frequency range of 10–300 cm −1 and its application to the study of weakly bound molecular complexes. The first section describes the light sources used for generating THz radiation, which includes the backward‐wave oscillators (BWO), the multipliers with the GaAs monolithic membrane diode (MOMED), and the supperlattice electronic devices (SLED), as well as the tunable far infrared (TuFIR) lasers. In the following section, we introduce extremely sensitive spectrometers developed for observing very weakly bound molecular complexes, such as the intra‐cavity OROTRON spectrometer and the millimeterwave‐Fourier transform microwave (MMW‐FTMW) double resonance spectrometer. We also review the traditional millimeter‐wave spectrometers, electric‐resonance optothermal spectrometers (EROS), and the tunable far‐infrared (TuFIR) laser spectrometers, which have also been applied successfully to study weakly bound molecular complexes. In the last section, the recent topics of the THz and millimeterwave spectroscopy of molecular complexes are reviewed in the four subsections; (i) Rare gas‐molecule complexes: Rg‐HX, Rg‐CO, and Rg‐HCN, (ii) dimers: (CO) 2 , CO‐N 2 , HCN‐H 2 , and (H 2 O) 2 , (iii) water complexes (H 2 O) n , with n up to 6, and (iv) ion and radical complexes: ArSH, ArH 2 O, H 2 OHO 2 , and ArH 3 + .

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“…2 A frequency-domain spectrometer was recently introduced 3 with a frequency resolution of better than 1 MHz, 4 which is adequate for molecular line spectroscopy. 4,5 Its source is a photomixer, which is a voltage-biased antenna-coupled photoconductor that generates a cw output at the difference frequency of the two tunable diode lasers that illuminate it. 6 A photomixer is tunable from dc to about 5 THz, 6 and its linewidth is determined by the stability of the lasers that drive it.…”

Section: ͓S0003-6951͑99͒01650-2͔mentioning

confidence: 99%

“…2 A frequency-domain spectrometer was recently introduced 3 with a frequency resolution of better than 1 MHz, 4 which is adequate for molecular line spectroscopy. 4,5 …”

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On-chip frequency-domain submillimeter-wave transceiver

Zamdmer

McIntosh

et al. 1999

Applied Physics Letters

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We demonstrate and model an on-chip frequency-domain transceiver which uses low-temperature-grown GaAs photoconductors to emit and detect continuous waves in the frequency range from 20 to 700 GHz propagating in a coplanar waveguide circuit. Our device has a possible frequency resolution (ϳ1 MHz) that is about 10 3 times better than similar devices used for time-domain spectroscopy, and is therefore appropriate for high-resolution spectroscopy with a ''lab-on-a-chip''-type integrated circuit. © 1999 American Institute of Physics. ͓S0003-6951͑99͒01650-2͔Photoconductive emitters and receivers are attractive as components of submillimeter-wave spectroscopy systems because of their tunability, compactness, and ability to be monolithically integrated with antennas, transmission lines, and microelectronic devices. Such systems can be classified in either of two ways: as time-domain or frequency-domain systems, or as systems involving free-space or on-chip submillimeter-wave propagation. Time-domain systems, which contain a photoconductive pulse emitter and sampler excited by a mode-locked laser, are the most investigated. They have been used for free-space characterization of semiconductor materials, 1 and on-chip characterization of ultrafast devices and circuits with 2.7 ps time resolution. 2 The frequency resolution is the inverse of the time span over which the propagating pulse is sampled. This span is determined by the length of an optical delay line, which usually results in a frequency resolution greater than 1 GHz. 2 A frequency-domain spectrometer was recently introduced 3 with a frequency resolution of better than 1 MHz, 4 which is adequate for molecular line spectroscopy. 4,5

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A Terahertz Photomixing Spectrometer: Application to SO2Self Broadening

Cited by 104 publications

References 19 publications

Tunable, continuous-wave Terahertz photomixer sources and applications

Tunable, continuous-wave Terahertz photomixer sources and applications

THz and Submillimeter‐wave Spectroscopy of Molecular Complexes

On-chip frequency-domain submillimeter-wave transceiver

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