Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037596
M. J. Kelly
Devices and circuits in volume production are the subject of very strong downward pressure on costs. Superior performance is not enough for devices and circuits, even where there is a clear market. In order to achieve low manufacturing costs, the designs have to be tolerant of fluctuations in relevant device parameters, the fabrication processes have to be reliable and highly reproducible, and a user-friendly simulator is required both for reverse engineering during the development stage and right-first-time design during manufacture. While prototype devices that exploit tunneling and resonant tunneling have many attractive performance features, the process of establishing low-cost manufacturability is as yet incomplete. Some recent results are however quite promising. They also have direct implications for the eventual manufacture of devices that incorporate mesoscopic or nanometer-scale features.
{"title":"Low cost manufacture of high frequency tunnel device systems","authors":"M. J. Kelly","doi":"10.1109/THZ.2002.1037596","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037596","url":null,"abstract":"Devices and circuits in volume production are the subject of very strong downward pressure on costs. Superior performance is not enough for devices and circuits, even where there is a clear market. In order to achieve low manufacturing costs, the designs have to be tolerant of fluctuations in relevant device parameters, the fabrication processes have to be reliable and highly reproducible, and a user-friendly simulator is required both for reverse engineering during the development stage and right-first-time design during manufacture. While prototype devices that exploit tunneling and resonant tunneling have many attractive performance features, the process of establishing low-cost manufacturability is as yet incomplete. Some recent results are however quite promising. They also have direct implications for the eventual manufacture of devices that incorporate mesoscopic or nanometer-scale features.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116816671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037608
S. Hadjiloucas, R. Galvão, V. Becerra, J. Bowen, R. Martini, M. Brucherseifer, H. Pellemans, P. Bolívar, H. Kurz, J. M. Chamberlain
A quasi-optical de-embedding technique for characterizing waveguides is demonstrated using wideband time-resolved terahertz spectroscopy. A transfer function representation is adopted for the description of the signal in the input and output port of the waveguides. The time domain responses were discretised and the waveguide transfer function was obtained through a parametric approach in the z-domain after describing the system with an ARX as well as with a state space model. Prior to the identification procedure, filtering was performed in the wavelet domain to minimize signal distortion and the noise propagating in the ARX and subspace models. The model identification procedure requires isolation of the phase delay in the structure and therefore the time-domain signatures must be firstly aligned with respect to each other before they are compared. An initial estimate of the number of propagating modes was provided by comparing the measured phase delay in the structure with theoretical calculations that take into account the physical dimensions of the waveguide. Models derived from measurements of THz transients in a precision WR-8 waveguide adjustable short will be presented.
{"title":"Wavelet filtered modelling applied to measurements of a waveguide's THz time domain response","authors":"S. Hadjiloucas, R. Galvão, V. Becerra, J. Bowen, R. Martini, M. Brucherseifer, H. Pellemans, P. Bolívar, H. Kurz, J. M. Chamberlain","doi":"10.1109/THZ.2002.1037608","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037608","url":null,"abstract":"A quasi-optical de-embedding technique for characterizing waveguides is demonstrated using wideband time-resolved terahertz spectroscopy. A transfer function representation is adopted for the description of the signal in the input and output port of the waveguides. The time domain responses were discretised and the waveguide transfer function was obtained through a parametric approach in the z-domain after describing the system with an ARX as well as with a state space model. Prior to the identification procedure, filtering was performed in the wavelet domain to minimize signal distortion and the noise propagating in the ARX and subspace models. The model identification procedure requires isolation of the phase delay in the structure and therefore the time-domain signatures must be firstly aligned with respect to each other before they are compared. An initial estimate of the number of propagating modes was provided by comparing the measured phase delay in the structure with theoretical calculations that take into account the physical dimensions of the waveguide. Models derived from measurements of THz transients in a precision WR-8 waveguide adjustable short will be presented.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130279134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037594
T. Baras, T. Kleine-Ostmann, M. Koch
Recently the marker free distinction between different kinds of biomolecules, e.g. hybridised (double-stranded) DNA (HDNA) and denatured (single-stranded) DNA (DDNA) using THz time-domain on-chip analysis has been demonstrated. Here we numerically examine the influence of critical experimental parameters on the transmission characteristics of a variety of microstrip resonators loaded with test samples of different thickness and refractive index.
{"title":"Design considerations for on-chip THz analysis of biomolecules","authors":"T. Baras, T. Kleine-Ostmann, M. Koch","doi":"10.1109/THZ.2002.1037594","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037594","url":null,"abstract":"Recently the marker free distinction between different kinds of biomolecules, e.g. hybridised (double-stranded) DNA (HDNA) and denatured (single-stranded) DNA (DDNA) using THz time-domain on-chip analysis has been demonstrated. Here we numerically examine the influence of critical experimental parameters on the transmission characteristics of a variety of microstrip resonators loaded with test samples of different thickness and refractive index.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125361276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037618
Y.C. Shen, P. Upadhya, A. Davies, E. Linfield
Laser-induced difference THz spectroscopy has been used to investigate three samples with different lifetimes. The spectroscopy system is based on a 10 nJ titanium sapphire laser with a pulse duration of 12 fs and a centre wavelength of 790 nm. For semi-insulting (SI) GaAs and high-resistivity (HR) silicon samples, absorption in the THz range is mainly a result of mobile electrons. A lifetime of about 50 ps has been determined for the SI-GaAs sample, whereas the lifetime of the HR-Si samples was found to be much larger than the time interval between two successive laser pulses (12 ns). As a result, the differential THz signal is about twenty times larger than that for SI-GaAs. We also observed that the THz pulse arrives at the detector 100 fs earlier when it transmitted through an optically excited HR-Si wafer. For copper pathancyonine (CuPc) pellet samples, the excited state remains for at least 1 ms. The absorption peak at 1.08 THz changes significantly under 790 nm laser excitation, suggesting that we have observed the first evidence of light-induced vibrational mode changes, in the THz range.
{"title":"Light-induced difference Terahertz spectroscopy and its biomedical applications","authors":"Y.C. Shen, P. Upadhya, A. Davies, E. Linfield","doi":"10.1109/THZ.2002.1037618","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037618","url":null,"abstract":"Laser-induced difference THz spectroscopy has been used to investigate three samples with different lifetimes. The spectroscopy system is based on a 10 nJ titanium sapphire laser with a pulse duration of 12 fs and a centre wavelength of 790 nm. For semi-insulting (SI) GaAs and high-resistivity (HR) silicon samples, absorption in the THz range is mainly a result of mobile electrons. A lifetime of about 50 ps has been determined for the SI-GaAs sample, whereas the lifetime of the HR-Si samples was found to be much larger than the time interval between two successive laser pulses (12 ns). As a result, the differential THz signal is about twenty times larger than that for SI-GaAs. We also observed that the THz pulse arrives at the detector 100 fs earlier when it transmitted through an optically excited HR-Si wafer. For copper pathancyonine (CuPc) pellet samples, the excited state remains for at least 1 ms. The absorption peak at 1.08 THz changes significantly under 790 nm laser excitation, suggesting that we have observed the first evidence of light-induced vibrational mode changes, in the THz range.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122132802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037607
M. R. Stone, M. Naftaly, N. N. Zinov'ev, R. Miles
Presents experimental characterization of large-aperture coplanar strip-line antennas, including a determination of the two-dimensional horizontal radiation cone and the dependence of the emitted power on the laser intensity and bias. Autocorrelation techniques were used to observe the frequency response of several antenna geometries.
{"title":"Characteristics of large-aperture photoconductive terahertz antennas","authors":"M. R. Stone, M. Naftaly, N. N. Zinov'ev, R. Miles","doi":"10.1109/THZ.2002.1037607","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037607","url":null,"abstract":"Presents experimental characterization of large-aperture coplanar strip-line antennas, including a determination of the two-dimensional horizontal radiation cone and the dependence of the emitted power on the laser intensity and bias. Autocorrelation techniques were used to observe the frequency response of several antenna geometries.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"359 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115871039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037612
J. Cao, H. Liu, S. Feng
Theoretically studied current self-oscillations and spatiotemporal current patterns in quantum-well (QW) negative-effective-mass (NEM) p/sup +/pp/sup +/ diodes when the electric field is applied along the direction of the well. The origin of current self-oscillations is the formation and traveling of electric-field domains in the well. In the calculations we have accurately considered scattering contributions from carrier-impurity, carrier-acoustic phonon, and carrier-optic phonon. It is indicated that, both the applied bias and the doping concentration in the well largely influence the current patterns and self-oscillating frequencies, which lie in the THz range for the NEM p/sup +/pp/sup +/ diode having a submicrometer p-base. The NEM p/sup +/pp/sup +/ diode presented here may therefore be used as an electrically tunable THz source.
{"title":"Terahertz generation in negative-effective-mass diodes","authors":"J. Cao, H. Liu, S. Feng","doi":"10.1109/THZ.2002.1037612","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037612","url":null,"abstract":"Theoretically studied current self-oscillations and spatiotemporal current patterns in quantum-well (QW) negative-effective-mass (NEM) p/sup +/pp/sup +/ diodes when the electric field is applied along the direction of the well. The origin of current self-oscillations is the formation and traveling of electric-field domains in the well. In the calculations we have accurately considered scattering contributions from carrier-impurity, carrier-acoustic phonon, and carrier-optic phonon. It is indicated that, both the applied bias and the doping concentration in the well largely influence the current patterns and self-oscillating frequencies, which lie in the THz range for the NEM p/sup +/pp/sup +/ diode having a submicrometer p-base. The NEM p/sup +/pp/sup +/ diode presented here may therefore be used as an electrically tunable THz source.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"198 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114431204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037600
D. Indjin, P. Harrison, R. Kelsall, Z. Ikonić
In this work, electron transport in GaAs/AlGaAs quantum cascade lasers operating at far-infrared wavelengths is calculated self-consistently using an intersubband scattering model. Subband populations and carrier transition rates are calculated and all relevant electron-electron and electron-LO phonon scatterings between the injector/collector and active region levels (13-levels in total) are included. Employing an energy balance equation which includes the influence of both electron-LO phonon and electron-electron scattering, the method also includes the evaluation of the electron temperature of the non-equilibrium carrier distributions in the device. The calculated threshold currents (J/sub th/ = 250-300 kA/cm/sup 2/) and electric field-current density characteristics (current saturation is predicted at /spl sim/680 A/cm/sup 2/), are in good qualitative and quantitative agreement with measurements in a recent experimental realization (Kohler et al, Nature, vol. 417, pp. 156-159, 2002). Due to the increased influence on electron-electron scatterings, the electron temperature is found to be more sensitive to the current density than in mid-infrared devices. The technique promises to be a powerful tool for the optimization of new, improved Terahertz quantum cascade lasers.
{"title":"Self-consistent rate equation modelling of a Terahertz GaAs/AlGaAs quantum-cascade laser","authors":"D. Indjin, P. Harrison, R. Kelsall, Z. Ikonić","doi":"10.1109/THZ.2002.1037600","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037600","url":null,"abstract":"In this work, electron transport in GaAs/AlGaAs quantum cascade lasers operating at far-infrared wavelengths is calculated self-consistently using an intersubband scattering model. Subband populations and carrier transition rates are calculated and all relevant electron-electron and electron-LO phonon scatterings between the injector/collector and active region levels (13-levels in total) are included. Employing an energy balance equation which includes the influence of both electron-LO phonon and electron-electron scattering, the method also includes the evaluation of the electron temperature of the non-equilibrium carrier distributions in the device. The calculated threshold currents (J/sub th/ = 250-300 kA/cm/sup 2/) and electric field-current density characteristics (current saturation is predicted at /spl sim/680 A/cm/sup 2/), are in good qualitative and quantitative agreement with measurements in a recent experimental realization (Kohler et al, Nature, vol. 417, pp. 156-159, 2002). Due to the increased influence on electron-electron scatterings, the electron temperature is found to be more sensitive to the current density than in mid-infrared devices. The technique promises to be a powerful tool for the optimization of new, improved Terahertz quantum cascade lasers.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121505968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037619
Yaochun Shen, P. Upadhya, E. Linfield, A. Davies
We have designed and built a vacuum-capable terahertz (THz) time-domain spectrometer which allows THz spectroscopy measurements to be made whilst avoiding interference from, for example, water vapour absorption. Using a biased semi-insulating GaAs emitter and a 1-mm-thick [110] oriented ZnTe crystal as an electro-optic detection sensor, we achieved a dynamic range of over 10/sup 10/ in THz power and a useful frequency range of over 3 THz. The system is very stable with a <2% day-to-day spectral variation, and up to ten samples can be measured without the need to open the vacuum chamber. In addition, the broadband (over 30 THz) capability of the system has been demonstrated by using a 30 /spl mu/m GaSe crystal as the emitter and a 20 /spl mu/m ZnTe crystal as the detector. The fine absorption features of uric acid were resolved at room temperature with this spectrometer, and are also presented.
{"title":"Design and performance of a novel vacuum-capable terahertz time-domain spectrometer","authors":"Yaochun Shen, P. Upadhya, E. Linfield, A. Davies","doi":"10.1109/THZ.2002.1037619","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037619","url":null,"abstract":"We have designed and built a vacuum-capable terahertz (THz) time-domain spectrometer which allows THz spectroscopy measurements to be made whilst avoiding interference from, for example, water vapour absorption. Using a biased semi-insulating GaAs emitter and a 1-mm-thick [110] oriented ZnTe crystal as an electro-optic detection sensor, we achieved a dynamic range of over 10/sup 10/ in THz power and a useful frequency range of over 3 THz. The system is very stable with a <2% day-to-day spectral variation, and up to ten samples can be measured without the need to open the vacuum chamber. In addition, the broadband (over 30 THz) capability of the system has been demonstrated by using a 30 /spl mu/m GaSe crystal as the emitter and a 20 /spl mu/m ZnTe crystal as the detector. The fine absorption features of uric acid were resolved at room temperature with this spectrometer, and are also presented.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"70 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120842565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037617
C. Schildknecht, T. Kleine-Ostmann, P. Knobloch, E. Rehberg, M. Koch
Applies numerical image enhancement methods to THz time-domain spectroscopy images in order to improve the quality of experimental data suffering from low resolution and finite focus diameter aperture effects. As an example, the level of detail in a biomedical image of a histopathological sample is shown to increase significantly.
{"title":"Numerical image enhancement for THz time-domain spectroscopy","authors":"C. Schildknecht, T. Kleine-Ostmann, P. Knobloch, E. Rehberg, M. Koch","doi":"10.1109/THZ.2002.1037617","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037617","url":null,"abstract":"Applies numerical image enhancement methods to THz time-domain spectroscopy images in order to improve the quality of experimental data suffering from low resolution and finite focus diameter aperture effects. As an example, the level of detail in a biomedical image of a histopathological sample is shown to increase significantly.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117027501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-11-07DOI: 10.1109/THZ.2002.1037605
J. R. Thorpe, J. R. Fletcher, J. M. Chamberlain, R. Miles, J. García-García, C. Mann, E. Huq, M. Oldfield, J. Spencer
The development of a micromachined submillimeter wave reflex klystron structure is described. An outline analysis is given of the key theoretical issues, such as oscillation and starting conditions, and how the output power scales with frequency. Two techniques for the realisation of the cavity assembly are outlined. The preferred method results in a free-standing gold re-entrant cavity of high surface quality. Field emitter tips are planned for use in this device: the present status of performance of these is described.
{"title":"Development of a submillimeter wave reflex klystron","authors":"J. R. Thorpe, J. R. Fletcher, J. M. Chamberlain, R. Miles, J. García-García, C. Mann, E. Huq, M. Oldfield, J. Spencer","doi":"10.1109/THZ.2002.1037605","DOIUrl":"https://doi.org/10.1109/THZ.2002.1037605","url":null,"abstract":"The development of a micromachined submillimeter wave reflex klystron structure is described. An outline analysis is given of the key theoretical issues, such as oscillation and starting conditions, and how the output power scales with frequency. Two techniques for the realisation of the cavity assembly are outlined. The preferred method results in a free-standing gold re-entrant cavity of high surface quality. Field emitter tips are planned for use in this device: the present status of performance of these is described.","PeriodicalId":143116,"journal":{"name":"Proceedings, IEEE Tenth International Conference on Terahertz Electronics","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127009651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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