Large area bolometers for THz power measurements

A theoretical model for the responsivity and noise-equivalent power (NEP) of photoconductive antennas (PCAs) as coherent, homodyne THz detectors is presented. The model is validated by comparison to experimental values obtained for two ErAs:InGaAs PCAs. The responsivity and NEP were obtained from the measured rectified current, the current noise floor in the PCAs, and the incoming THz power for the same conditions. Since the THz power measurements are performed with a pyroelectric detector calibrated by the National Metrology Institute of Germany (PTB), the experimentally obtained values are directly traceable to the International System of Units (SI) for the described conditions. The agreement between the presented model and the experimental results is excellent using only one fitting parameter. A very low NEP of 1.8 fW/Hz at 188.8 GHz is obtained at room temperature.

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Novel pyroelectric detectors for accurate THz power measurements

tm - Technisches Messen ◽

10.1515/teme-2015-0083 ◽

2016 ◽

Vol 83 (6) ◽

Cited By ~ 6

Author(s):

Andreas Steiger ◽

Werner Bohmeyer ◽

Karsten Lange ◽

Ralf Müller

Keyword(s):

Spectral Range ◽

Time Domain ◽

National Metrology Institute ◽

Time Domain Spectroscopy ◽

Thz Detectors ◽

Pyroelectric Detectors ◽

Close Cooperation ◽

Power Measurements ◽

First Time ◽

Thz Power

AbstractNovel pyroelectric THz detectors have been developed in close cooperation between PTB, the National Metrology Institute of Germany, and the Sensor- und Lasertechnik company. Covering the broad spectral range from below 50 GHz to beyond 5 THz, these detectors are suited to measure the absolute THz power of time-domain spectroscopy (THz-TDS) systems for the first time.

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Convergent Beam Electron Diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070072 ◽

1978 ◽

Vol 36 (3) ◽

pp. 304-315

Author(s):

G. Lehmpfuhl

Keyword(s):

Electron Diffraction ◽

Diffraction Pattern ◽

Crystal Surface ◽

Diffraction Spot ◽

Crystal Thickness ◽

Large Area ◽

Electron Microscopic ◽

Additional Information ◽

Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

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TEM Study of a Tilt Boundary in Hot-Pressed Silicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100097454 ◽

1981 ◽

Vol 39 ◽

pp. 160-161

Author(s):

C. B. Carter ◽

J. Rose ◽

D. G. Ast

Keyword(s):

Electron Diffraction ◽

Imaging Technique ◽

Interface Structure ◽

Large Area ◽

Weak Beam ◽

Lattice Fringe ◽

Electron Diffraction Technique ◽

Tilt Boundaries ◽

Beam Technique ◽

Twist Boundaries

The hot-pressing technique which has been successfully used to manufacture twist boundaries in silicon has now been used to form tilt boundaries in this material. In the present study, weak-beam imaging, lattice-fringe imaging and electron diffraction techniques have been combined to identify different features of the interface structure. The weak-beam technique gives an overall picture of the geometry of the boundary and in particular allows steps in the plane of the boundary which are normal to the dislocation lines to be identified. It also allows pockets of amorphous SiO2 remaining in the interface to be recognized. The lattice-fringe imaging technique allows the boundary plane parallel to the dislocation to be identified. Finally the electron diffraction technique allows the periodic structure of the boundary to be evaluated over a large area - this is particularly valuable when the dislocations are closely spaced - and can also provide information on the structural width of the interface.

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P20 phosphor on polyimide as a large area high-resolution transmission screen for slow scan CCD systems

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100136477 ◽

1995 ◽

Vol 53 ◽

pp. 20-21

Author(s):

C. C. Ahn ◽

S. Karnes ◽

M. Lvovsky ◽

C. M. Garland ◽

H. A. Atwater ◽

...

Keyword(s):

Mechanical Stability ◽

High Energy ◽

Practical Implementation ◽

Line Pair ◽

Modulation Transfer ◽

Large Area ◽

Ccd Imaging ◽

Transmission Electron ◽

The One ◽

Beam Broadening

The bane of CCD imaging systems for transmission electron microscopy at intermediate and high voltages has been their relatively poor modulation transfer function (MTF), or line pair resolution. The problem originates primarily with the phosphor screen. On the one hand, screens should be thick so that as many incident electrons as possible are converted to photons, yielding a high detective quantum efficiency(DQE). The MTF diminishes as a function of scintillator thickness however, and to some extent as a function of fluorescence within the scintillator substrates. Fan has noted that the use of a thin layer of phosphor beneath a self supporting 2μ, thick Al substrate might provide the most appropriate compromise for high DQE and MTF in transmission electron microcscopes which operate at higher voltages. Monte Carlo simulations of high energy electron trajectories reveal that only little beam broadening occurs within this thickness of Al film. Consequently, the MTF is limited predominantly by broadening within the thin phosphor underlayer. There are difficulties however, in the practical implementation of this design, associated mostly with the mechanical stability of the Al support film.

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