scholarly journals Roadmap of Terahertz Imaging 2021

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4092
Author(s):  
Gintaras Valušis ◽  
Alvydas Lisauskas ◽  
Hui Yuan ◽  
Wojciech Knap ◽  
Hartmut G. Roskos
Keyword(s):  
Room Temperature ◽  
Continuous Wave ◽  
Computational Imaging ◽  
Imaging Systems ◽  
Thz Imaging ◽  
Operational Conditions ◽  
Frequency Combs ◽  
Wave Imaging ◽  
On Chip ◽  
Nano Imaging

In this roadmap article, we have focused on the most recent advances in terahertz (THz) imaging with particular attention paid to the optimization and miniaturization of the THz imaging systems. Such systems entail enhanced functionality, reduced power consumption, and increased convenience, thus being geared toward the implementation of THz imaging systems in real operational conditions. The article will touch upon the advanced solid-state-based THz imaging systems, including room temperature THz sensors and arrays, as well as their on-chip integration with diffractive THz optical components. We will cover the current-state of compact room temperature THz emission sources, both optolectronic and electrically driven; particular emphasis is attributed to the beam-forming role in THz imaging, THz holography and spatial filtering, THz nano-imaging, and computational imaging. A number of advanced THz techniques, such as light-field THz imaging, homodyne spectroscopy, and phase sensitive spectrometry, THz modulated continuous wave imaging, room temperature THz frequency combs, and passive THz imaging, as well as the use of artificial intelligence in THz data processing and optics development, will be reviewed. This roadmap presents a structured snapshot of current advances in THz imaging as of 2021 and provides an opinion on contemporary scientific and technological challenges in this field, as well as extrapolations of possible further evolution in THz imaging.

On-chip integration solutions of compact optics and detectors in room-temperature terahertz imaging systems

2015 ◽  
Author(s):  
Linas Minkevičius ◽  
Vincas Tamošiūnas ◽  
Irmantas Kašalynas ◽  
Rimvydas Venckevičius ◽  
Karolis Madeikis ◽  
...  
Keyword(s):  
Room Temperature ◽  
Terahertz Imaging ◽  
Imaging Systems ◽  
On Chip

scholarly journals From the Lugiato–Lefever equation to microresonator-based soliton Kerr frequency combs

2018 ◽  
Vol 376 (2135) ◽  
pp. 20180113 ◽  
Author(s):  
L. A. Lugiato ◽  
F. Prati ◽  
M. L. Gorodetsky ◽  
T. J. Kippenberg
Keyword(s):  
Pattern Formation ◽  
Continuous Wave ◽  
Laser Frequency ◽  
Dissipative Structures ◽  
Low Noise ◽  
Optical Systems ◽  
Frequency Synthesis ◽  
Frequency Combs ◽  
Optical Microresonators ◽  
On Chip

The model, that is usually called the Lugiato–Lefever equation (LLE), was introduced in 1987 with the aim of providing a paradigm for dissipative structure and pattern formation in nonlinear optics. This model, describing a driven, detuned and damped nonlinear Schroedinger equation, gives rise to dissipative spatial and temporal solitons. Recently, the rather idealized conditions, assumed in the LLE, have materialized in the form of continuous wave driven optical microresonators, with the discovery of temporal dissipative Kerr solitons (DKS). These experiments have revealed that the LLE is a perfect and exact description of Kerr frequency combs—first observed in 2007, i.e. 20 years after the original formulation of the LLE—and in particular describe soliton states. Observed to spontaneously form in Kerr frequency combs in crystalline microresonators in 2013, such DKS are preferred state of operation, offering coherent and broadband optical frequency combs, whose bandwidth can be extended exploiting soliton-induced broadening phenomena. Combined with the ability to miniaturize and integrate on-chip, microresonator-based soliton Kerr frequency combs have already found applications in self-referenced frequency combs, dual-comb spectroscopy, frequency synthesis, low noise microwave generation, laser frequency ranging, and astrophysical spectrometer calibration, and have the potential to make comb technology ubiquitous. As such, pattern formation in driven, dissipative nonlinear optical systems is becoming the central Physics of soliton micro-comb technology. This article is part of the theme issue ‘Dissipative structures in matter out of equilibrium: from chemistry, photonics and biology (part 2)’.

scholarly journals Continuous-Wave THz Imaging for Biomedical Samples

2020 ◽  
Vol 11 (1) ◽  
pp. 71
Author(s):  
Yaya Zhang ◽  
Chuting Wang ◽  
Bingxin Huai ◽  
Shiyu Wang ◽  
Yating Zhang ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Biomedical Imaging ◽  
Continuous Wave ◽  
Biological Tissues ◽  
Thz Spectroscopy ◽  
Label Free ◽  
Thz Imaging ◽  
Malignant Tumours ◽  
Advantages And Disadvantages ◽  
Imaging Application

In the past few decades, the applications of terahertz (THz) spectroscopy and imaging technology have seen significant developments in the fields of biology, medical diagnosis, food safety, and nondestructive testing. Label-free diagnosis of malignant tumours has been obtained and also achieved significant development in THz biomedical imaging. This review mainly presents the research status and prospects of several common continuous-wave (CW) THz medical imaging systems and applications of THz medical imaging in biological tissues. Here, we first introduce the properties of THz waves and how these properties play a role in biomedical imaging. Then, we analyse both the advantages and disadvantages of the CW THz imaging methods and the progress of these methods in THz biomedical imaging in recent ten years. Finally, we summarise the obstacles in the way of the application of THz bio-imaging application technology in clinical detection, which need to be investigated and overcome in the future.

scholarly journals Spectral Broadening in a Continuously Pumped Singly Resonant Second-Harmonic Cavity

2021 ◽  
Vol 11 (15) ◽  
pp. 7122
Author(s):  
Simona Mosca ◽  
Tobias Hansson ◽  
Maria Parisi
Keyword(s):  
Continuous Wave ◽  
Frequency Comb ◽  
Second Harmonic ◽  
Input Power ◽  
Second Order ◽  
Optical Frequency ◽  
Frequency Combs ◽  
Research Areas ◽  
Mixed Regime ◽  
Wide Range

Optical frequency comb synthesizers with a wide spectral range are an essential tool for many research areas such as spectroscopy, precision metrology, optical communication, and sensing. Recent studies have demonstrated the direct generation of frequency combs, via second-order processes, that are centered on two different spectral regions separated by an octave. Here, we present the capability of optical quadratic frequency combs for broad-bandwidth spectral emission in unexplored regimes. We consider comb formation under phase-matched conditions in a continuous-wave pumped singly resonant second-harmonic cavity, with large intracavity power and control of the detuning over several cavity line widths. The spectral analysis reveals quite distinctive sidebands that arise far away from the pump, singularly or in a mixed regime together with narrowband frequency combs. Notably, by increasing the input power, the optical frequency lines evolve into widely spaced frequency clusters, and at maximum power, they appear in a wavelength range spanning up to 100 nm. The obtained results demonstrate the power of second-order nonlinearities for direct comb production within a wide range of pump wavelengths.

scholarly journals Characteristics Of Room Temperature-CW Operated InGaN Multi-Quantum-Well-Structure Laser Diodes

1997 ◽  
Vol 2 ◽  
Author(s):  
Shuji Nakamura
Keyword(s):  
Quantum Well ◽  
Carrier Density ◽  
Room Temperature ◽  
Continuous Wave ◽  
Laser Diodes ◽  
Gain Coefficient ◽  
Threshold Current ◽  
Quantum Well Structure ◽  
Multi Quantum Well ◽  
Structure Laser

The continuous-wave (CW) operation of InGaN multi-quantum-well-structure laser diodes (LDs) was demonstrated at room temperature (RT) with a lifetime of 35 hours. The threshold current and the voltage of the LDs were 80 mA and 5.5 V, respectively. The threshold current density was 3.6 kA/cm2. When the temperature of the LDs was varied, large mode hopping of the emission wavelength was observed. The carrier lifetime and the threshold carrier density were estimated to be 2-10 ns and 1-2 × 1020/cm3, respectively. From the measurements of gain spectra and an external differential quantum efficiency dependence on the cavity length, the differential gain coefficient, the transparent carrier density, threshold gain and internal loss were estimated to be 5.8×10−17 cm2, 9.3×1019 cm−3, 5200 cm−1 and 43 cm−1, respectively.

scholarly journals Compact CH4 sensor system based on a continuous-wave, low power consumption, room temperature interband cascade laser

2016 ◽  
Vol 108 (1) ◽  
pp. 011106 ◽  
Author(s):  
Lei Dong ◽  
Chunguang Li ◽  
Nancy P. Sanchez ◽  
Aleksander K. Gluszek ◽  
Robert J. Griffin ◽  
...  
Keyword(s):  
Power Consumption ◽  
Low Power ◽  
Room Temperature ◽  
Continuous Wave ◽  
Sensor System ◽  
Low Power Consumption ◽  
Interband Cascade Laser
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