scholarly journals Continuous wave terahertz receivers with 45 THz bandwidth and 112 dB dynamic range

2021 ◽  
Author(s):  
Milan Deumer ◽  
Steffen Breuer ◽  
Robert Kohlhaas ◽  
Simon Nellen ◽  
Lars Liebermeister ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Dynamic Range

scholarly journals Optoelectronic frequency-modulated continuous-wave terahertz spectroscopy with 4 THz bandwidth

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lars Liebermeister ◽  
Simon Nellen ◽  
Robert B. Kohlhaas ◽  
Sebastian Lauck ◽  
Milan Deumer ◽  
...  
Keyword(s):  
Fiber Optics ◽  
Continuous Wave ◽  
Dynamic Range ◽  
Terahertz Spectroscopy ◽  
Beat Signal ◽  
Photonic Integration ◽  
Terahertz Time Domain Spectroscopy ◽  
Destructive Testing ◽  
Optical Delay ◽  
Broadband Terahertz

AbstractBroadband terahertz spectroscopy enables many promising applications in science and industry alike. However, the complexity of existing terahertz systems has as yet prevented the breakthrough of this technology. In particular, established terahertz time-domain spectroscopy (TDS) schemes rely on complex femtosecond lasers and optical delay lines. Here, we present a method for optoelectronic, frequency-modulated continuous-wave (FMCW) terahertz sensing, which is a powerful tool for broadband spectroscopy and industrial non-destructive testing. In our method, a frequency-swept optical beat signal generates the terahertz field, which is then coherently detected by photomixing, employing a time-delayed copy of the same beat signal. Consequently, the receiver current is inherently phase-modulated without additional modulator. Owing to this technique, our broadband terahertz spectrometer performs (200 Hz measurement rate, or 4 THz bandwidth and 117 dB peak dynamic range with averaging) comparably to state-of-the-art terahertz-TDS systems, yet with significantly reduced complexity. Thickness measurements of multilayer dielectric samples with layer-thicknesses down to 23 µm show its potential for real-world applications. Within only 0.2 s measurement time, an uncertainty of less than 2 % is achieved, the highest accuracy reported with continuous-wave terahertz spectroscopy. Hence, the optoelectronic FMCW approach paves the way towards broadband and compact terahertz spectrometers that combine fiber optics and photonic integration technologies.

A theoretical study of digital silicon photomultiplier utilization in diffuse optical imaging systems

2019 ◽  
Vol 64 (3) ◽  
pp. 357-363 ◽  
Author(s):  
Taha Haddadifam ◽  
Mohammad Azim Karami
Keyword(s):  
Optical Imaging ◽  
Continuous Wave ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
High Dynamic Range ◽  
Diffuse Optical Imaging ◽  
Silicon Photomultiplier ◽  
Thoracic Imaging ◽  
Low Level

Abstract Digital silicon photomultiplier (dSiPM) is introduced for diffuse optical imaging (DOI) applications instead of conventional photomultiplier tubes and avalanche photodiodes (APDs) as a state-of-the-art detector. According to the low-level light regime in DOI applications, high sensitivity and high dynamic range (DR) image sensors are needed for DOI systems. dSiPM is proposed as a developing detector which can detect low-level lights. Also, an accurate equation is obtained for calculating the DR of dSiPMs. Different dSiPMs and the corresponding benefits are studied for DOI applications. Furthermore, a 120 dB DR dSiPM is chosen for use in DOI systems. It is shown that dSiPMs can be utilized in DOI configurations such as time domain (TD), frequency domain (FD) and continuous wave (CW) systems. Ultimately, by utilizing dSiPM in DOI systems, the DOI method can be used for thoracic imaging due to the high DR and signal-to-noise ratio (SNR) of the detector.

Advances in Remote Sensing Research on Oil and Ice from the IOGP Arctic Oil Spill Response Technology JIP

2017 ◽  
Vol 2017 (1) ◽  
pp. 1819-1835
Author(s):  
David Palandro ◽  
Joseph Mullin
Keyword(s):  
Remote Sensing ◽  
Oil Spill ◽  
Continuous Wave ◽  
Dynamic Range ◽  
Laser Fluorescence ◽  
Army Corps ◽  
Second Phase ◽  
Wave Radar ◽  
Oil Spill Response ◽  
Ice Conditions

ABSTRACT (2017-044) The IOGP Arctic Oil Spill Response Technology Joint Industry Program’s Remote Sensing Technical Working Group was initiated in 2012 with the objective to expand the oil industry’s detection and monitoring capabilities for spills on, under, around or in ice. The first phase produced two state-of-knowledge reports assessing sensor capabilities above and below the ice. A key finding from these studies was that many existing remote sensing platforms and sensors originally developed for oil on open water can also provide effective sensing in a broad range of ice conditions. The second phase covered an integrated experiment that included sensor testing in a cold basin, followed by modeling to determine potential applicability of different sensors in a wider range of sea-ice conditions. Five above-ice (Frequency Modulated Continuous Wave Radar (FMCW), ground penetrating radar (GPR), visible and infrared cameras and laser fluorescence polarization [LP] sensor) and seven below-ice (high dynamic range optical camera, visible and infrared spectrometer, LP sensor, broadband and narrowband sonar and multibeam echo sounder) sensors were tested with varying ice thickness and oil concentrations at the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL) over a three-month period. All of the sensors used during this experiment showed some ability to detect oil on, in, or below ice under certain conditions and major advances in the knowledge of sensor applicability were made. Three follow-on projects (late 2016) include an operations guide providing a concise operationally oriented review of the different sensor technologies in key oil and ice scenarios, and additional field testing with medium to long-wave infrared, and the FMCW radar.

scholarly journals Modeling of Millimeter-Wave Modulation Characteristics of Semiconductor Lasers under Strong Optical Feedback

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Ahmed Bakry
Keyword(s):  
Semiconductor Lasers ◽  
Continuous Wave ◽  
Dynamic Range ◽  
Optical Feedback ◽  
Harmonic Distortion ◽  
Wave Band ◽  
Third Order ◽  
Signal Characteristics ◽  
Simulated Time ◽  
Photon Resonance

This paper presents modeling and simulation on the characteristics of semiconductor laser modulated within a strong optical feedback (OFB-)induced photon-photon resonance over a passband of millimeter (mm) frequencies. Continuous wave (CW) operation of the laser under strong OFB is required to achieve the photon-photon resonance in the mm-wave band. The simulated time-domain characteristics of modulation include the waveforms of the intensity and frequency chirp as well as the associated distortions of the modulated mm-wave signal. The frequency domain characteristics include the intensity modulation (IM) and frequency modulation (FM) responses in addition to the associated relative intensity noise (RIN). The signal characteristics under modulations with both single and two mm-frequencies are considered. The harmonic distortion and the third order intermodulation distortion (IMD3) are examined and the spurious free dynamic range (SFDR) is calculated.

THz Pulse Spectroscopy of Dynamic Plasmas: A New Diagnostic Tool

2009 ◽  
Vol 1163 ◽  
Author(s):  
Brian H. Kolner
Keyword(s):  
Continuous Wave ◽  
Dynamic Range ◽  
Molecular Spectroscopy ◽  
Collision Frequency ◽  
Diagnostic Techniques ◽  
New Technique ◽  
Dc Discharge ◽  
Pulsed Dc ◽  
Minimization Technique ◽  
Optical Fluorescence

AbstractRapidly evolving plasmas represent a challenging environment for both study and control. Density, collision frequency and temperature fluctuations can change over orders of magnitude on time scales of one ns with spatial features less than one cm and thus are not amenable to conventional continuous-wave diagnostic techniques such as microwave or mm-wave interferometry. We have developed a new technique for studying plasmas undergoing rapid nonequilibrium changes that uses THz time-domain spectroscopy (THz-TDS) in conjunction with optical fluorescence imaging. The advantages of using THz pulses lie in the fact that the broad bandwidth of a THz pulse contains frequency components both above and below the plasma frequency allowing a single ps-duration pulse to carry away information about the complex path-integrated susceptibility. Transverse fluorescence gives us a model of the longitudinal plasma distribution and using a novel rms error-minimization technique we can recover the real and imaginary parts of the susceptibility with <5 mm spatial and, potentially, ps time resolution (we are currently limited by S/N considerations to averaging over several THz pulses and thus obtain 40 ns resolution). From this we obtain the electron density and collision frequency, spatially and temporally resolved, with dynamic range >103. The principle of this new technique will be discussed along with results on a pulsed DC-discharge plasma. We will also present some new ideas such as concurrent molecular spectroscopy and computed tomography.

scholarly journals Improved alpha-beta power reduction via combined Electrical and Ultrasonic stimulation in a Parkinsonian Cortex-Basal Ganglia-Thalamus Computational Model

2021 ◽  
Author(s):  
Thomas Tarnaud ◽  
Wout Joseph ◽  
Ruben Schoeters ◽  
Luc Martens ◽  
Emmeric Tanghe
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Basal Ganglia ◽  
Neuronal Network ◽  
Continuous Wave ◽  
Dynamic Range ◽  
Cortical Cell ◽  
Acoustic Stimulation ◽  
Isolated Neurons ◽  
Beta Power

AbstractObjectiveTo investigate computationally the interaction of combined electrical and ultrasonic modulation of isolated neurons and of the Parkinsonian cortex-basal ganglia-thalamus loop.MethodsContinuous-wave or pulsed electrical and ultrasonic neuromodulation is applied to isolated Otsuka plateau-potential generating subthalamic nucleus (STN) and Pospischil regular, fast and low-threshold spiking cortical cells in a temporally-alternating or simultaneous manner. Similar combinations of electrical/ultrasonic waveforms are applied to a Parkinsonian biophysical cortex-basal ganglia-thalamus neuronal network. Ultrasound-neuron interaction is modelled respectively for isolated neurons and the neuronal network with the NICE and SONIC implementations of the bilayer sonophore underlying mechanism. Reduction in α—β spectral energy is used as a proxy to express improvement in Parkinson’s disease by insonication and electrostimulation.ResultsSimultaneous electro-acoustic stimulation achieves a given level of neuronal activity at lower intensities compared to the separate stimulation modalities. Conversely, temporally alternating stimulation with 50 Hz electrical and ultrasound pulses is capable of eliciting 100 Hz STN firing rates. Furthermore, combination of ultrasound with hyperpolarizing currents can alter cortical cell relative spiking regimes. In the Parkinsonian neuronal network, high-frequency pulsed separated electrical and ultrasonic deep brain stimulation (DBS) reduce pathological α — β power by entraining STN-neurons. In contrast, continuous-wave ultrasound reduces pathological oscillations by silencing the STN. Compared to the separated stimulation modalities, temporally simultaneous or alternating electro-acoustic stimulation can achieve higher reductions in α — β power for the same contraints on electrical/ultrasonic intensity.ConclusionContinuous-wave and pulsed ultrasound reduce pathological oscillations by different mechanisms. Electroacoustic stimulation further improves α— β power for given safety limits and is capable of altering cortical relative spiking regimes.Significancefocused ultrasound has the potential of becoming a non-invasive alternative of conventional DBS for the treatment of Parkinson’s disease. Here, we elaborate on proposed benefits of combined electro-acoustic stimulation in terms of improved dynamic range, efficiency, resolution, and neuronal selectivity.

scholarly journals Sub-THz Characterisation of Monolayer Graphene

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Ehsan Dadrasnia ◽  
Sujitha Puthukodan ◽  
Vinod V. K. Thalakkatukalathil ◽  
Horacio Lamela ◽  
Guillaume Ducournau ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Dynamic Range ◽  
Monolayer Graphene ◽  
Network Analyzer ◽  
Electrical Characteristics ◽  
Scattering Parameters ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Wave Measurement ◽  
Direct Measurements

We explore the optical and electrical characteristics of monolayer graphene by using pulsed optoelectronic terahertz time-domain spectroscopy in the frequency range of 325–500 GHz based on fast direct measurements of phase and amplitude. We also show that these parameters can, however, be measured with higher resolution using a free space continuous wave measurement technique associated with a vector network analyzer that offers a good dynamic range. All the scattering parameters (both magnitude and phase) are measured simultaneously. The Nicholson-Ross-Weir method is implemented to extract the monolayer graphene parameters at the aforementioned frequency range.

scholarly journals SELECTED PROBLEMS OF PROCESSING A RADAR SIGNAL WITH A LFM-FSK MODULATION

Aviation ◽  
2015 ◽  
Vol 19 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Tadeusz Grabowski ◽  
Jan Dziupiński ◽  
Ewelina Szpakowska-Peas
Keyword(s):  
Moving Objects ◽  
Continuous Wave ◽  
Dynamic Range ◽  
Mutual Influence ◽  
Radar Signal ◽  
Foam Material ◽  
Multiple Objects ◽  
Operational Model ◽  
Wave Radar ◽  
Transmitted Signal

An operational model of continuous-wave radar designed for detection of stationary and moving objects in the air was built at the Institute of Aviation. The LFM-FSK modulation of radiated signal was selected, due to its advantages (short measurement time, not very complicated algorithm of calculations, the possibility of simultaneous measurement of the range and velocity of multiple objects). The modulation waveform is composed of two intertwined strictly linear or stepwise sweeps. Two adverse phenomena (the mutual influence, resulting from not perfect transmittance of receiver channel, of the samples related to even and odd steps of the transmitted signal and the leakage of transmitted signal into the receiver antenna causing an excessive increase of receiver output dynamic range) were encountered during the development process. The issues relating to them are presented in the paper. The first issue was solved by the use of a pre-compensation digital filter. The dynamics of the leakage signal was reduced by mixing of quadrature output signals of the radar head in a proper proportion, and by using the dome made of foam material, instead of a laminate one, which was designed initially.

scholarly journals CW Direct Detection Lidar with a Large Dynamic Range of Wind Speed Sensing in a Remote and Spatially Confined Volume

2021 ◽  
Vol 13 (18) ◽  
pp. 3716
Author(s):  
Lichun Meng ◽  
Christian Pedersen ◽  
Peter John Rodrigo
Keyword(s):  
Wind Speed ◽  
High Speed ◽  
Continuous Wave ◽  
Dynamic Range ◽  
Weighting Function ◽  
Direct Detection ◽  
Coherent Detection ◽  
Axial Profile ◽  
Update Rate ◽  
Wind Lidar

A novel continuous-wave (CW) direct detection lidar (DDL) is demonstrated to be capable of wind speed measurement 40 m away with an update rate of 4 Hz using a fiber-based scanning Fabry–Perot interferometer as an optical frequency discriminator. The proposed CW DDL has a large dynamic wind speed range with no sign ambiguity and its sensitivity is assessed by comparing its performance with that of a CW coherent detection lidar (CDL) in a side-by-side wind measurement. A theoretical model of the spatial weighting function of the fiber-based CW DDL is also presented and validated experimentally. This work shows that the CW DDL has a spatially confined measurement volume with a Lorentzian axial profile similar to that of a CW CDL. The proposed DDL has potential use in various applications in which requirements such as high-speed wind sensing and directional discrimination are not met by state-of-the-art Doppler wind lidar systems.

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