UP-conversion of terahertz radiation induced by photon drag effect (original) (raw)
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Diffusion and drift in terahertz emission at GaAs surfaces
We study terahertz ͑THz͒ emission from GaAs as a function of photon energy and electric field. THz radiation arises from transport of photogenerated charge in an electric field and by hot carrier diffusion ͑the photo-Dember effect͒. These mechanisms can be separated by experiments in which either the electric field or the kinetic energy of the carriers is varied. For electric fields E ϳ4 kV/cm, we find that the electric field controls THz emission for carrier temperatures k B T C р0.1 eV, while hot-carrier diffusion dominates for k B T C Ϸ1 eV. Both mechanisms contribute at intermediate fields and carrier temperatures. Our results are consistent with estimates of the relative magnitudes of these two effects.
Excitation wavelength dependence of terahertz emission from semiconductor surface
Applied Physics Letters, 2006
The authors have measured terahertz radiation from InSb, InAs, and InGaAs excited by femtosecond optical pulses at wavelengths of 1560, 1050, and 780 nm. The amplitude of the terahertz field strongly depends on the pump wavelengths. Among the materials, the InSb emitter shows the largest terahertz emission amplitude at high power 1560 nm excitation, whereas 780 nm excitation provides the weakest. With increasing photon energy, the increase in emission amplitude from InAs is less as compared to that from InGaAs. The decrease from InSb and InAs originates in low mobilities of L or X valley carriers generated by intervalley scatterings.
THz generation using 800 to 1550 nm excitation of photoconductors
2009
We demonstrate the efficient generation of terahertz (THz) radiation from Fe-doped InGaAs-based photoconductive antennas. We present time-domain data showing generation of pulsed THz radiation from antennas fabricated on two different wafers, optimized to maximize the near-infrared-to-THz conversion efficiency. Detection was performed using both (110) ZnTe and GaP crystals, with pump and probe wavelengths being adjusted from 800 nm to 1550 nm using a cavity-tuned OPO pumped by a pulsed near-infrared Ti:Sapphire laser.
Optical detection of terahertz radiation by using nonlinear parametric upconversion
Optics Letters, 2007
We describe and demonstrate sensitive room-temperature detection of terahertz (THz) radiation by nonlinearly upconverting terahertz to the near-infrared regime, relying on telecommications components. THz radiation at 700 GHz is mixed with pump light at 1550 nm in a bulk GaAs crystal to generate an idler wave at 1555.6 nm, which is separated and detected by using a commercial p-in diode. The THz detector operates at room temperature and has an intrinsic THz-to-optical photon conversion efficiency of 0.001%.
Optical and Quantum Electronics, 2016
We present a fast and robust optical method of determining carrier concentrations in heavily doped layered structures. We discuss several advantages of the technique as compared to other, more commonly applied methods using as an example InAs based devices used for THz radiation generation. Our approach leads to a more accurate estimation of doping levels in the investigated structures and aids the standard Hall measurements in precise predictions of radiative efficacy in the THz region. Predicted enhancement factors reproduce THz-Time Domain Spectroscopy (TDS) experiment results within a 2 % accuracy. Keywords FDR Á Doping density Á Carrier concentration Á THz Á InAs This article is part of the Topical Collection on TERA-MIR: Materials, Generation, Detection and Applications.
Photothermal converters for quantitative 2D and 3D real-time TeraHertz imaging
Qirt Journal, 2010
Recent advances for the measurement of TeraHertz (THz) radiation by using original IR temperature flux sensors are presented. The bolometer principle is used for designing simple thermal converters for THz radiations (measurement of the temperature increase of a sensitive absorber). Most of these sensors are efficient, sensitive and fast enough for quantitative measurement of THz source power as well as for 2D and 3D THz imaging. By combining optical and thermal technologies, we extend and adapt the use of thermal sensors to large THz wavelength till 3 mm (0.1 THz). A large variety of mono- or arrayed- thermal sensors is used and optimized for real-time room temperature THz imaging using adapted IR focal-plane microbolometers array (FPMA) camera. Optimisation and adaptation of such FPMA is discussed and a new arrayed prototype device of THz-Thermal Converter, “TTC”, for full-field real-time THz imaging is presented. This small size, low cost and efficient prototype design is discussed from the thermal point of view and is characterized using a compact powerful THz source. Their sensitivity is evaluated and the obtained 2D and 3D images clearly illustrates the high potential of this new kind of THz camera. Finally, it is shown that non-arrayed extended plane TTCs (EMIR sensitive screens) coupled to FPA cameras produce THz images free of diffraction phenomena.
Special Section Guest Editorial: Advances in Terahertz and Infrared Optoelectronics
Optical Engineering
This special section presents recent results in the field of infrared (IR) and terahertz (THz) optoelectronics, which have been developing rapidly over the past decades. The progress of IR and THz technologies affects a variety of fundamental problems in material science, astrophysics, chemistry and biology, medical diagnosis, and high-resolution and multispectral imaging modalities. Novel and improved IR and THz sources, detectors, and optical components enabled for filtering and waveguiding have revolutionized the IR and especially THz technology, where the problem of limited efficiency and high cost still need to be solved. The emergence of THz and IR quantum-cascade lasers, uncooled and multi-element detectors, novel types of photoconductive antennas, low-loss waveguides, advanced metamaterials have a potential for addressing these problems and, in turn, spawn further applications of THz and IR optoelectronics, including near-field and real-time imaging and high-resolution microscopy. The increased power of novel sources poses a question of the THz safety and dosimetry. The special section is focused on cutting-edge fundamental and applied trends including novel materials, the interaction of THz and IR radiation with biological tissues, THz quantum-cascade lasers, nonlinear effects and optical light confinement in media, THz and IR spectroscopic and imaging systems, and advanced THz sources. Ryzhii et al. proposed far-IR photodetectors using the graphene nanoribbon arrays and the black phosphorus (BP) base layers as the photosensitive element. The detector operation involves the interband photogeneration of the electron-hole pairs in the graphene nanoribbon array followed by the tunneling injection of either electrons or holes into a wide gap BP base layer. The detector is predicted to have a rather short response time. Kruchunina et al. applied THz spectroscopy and dielectrophoresis for the studies of the erythrocytes of the patients with diffuse liver diseases with applications to diagnostics and differentiation of liver fibrosis. The authors obtained strong correlations of the THz spectroscopy indices with electrical and viscoelastic parameters of red blood cells. They also showed that the increase in the degree of liver fibrosis is associated with an increase in the number of deformed cells prone to aggregation and destruction. Dorofeev et al. reported on the role of the tangential electric field component to the THz jet and the curved waves that could be produced when a light wave is passing through a dielectric cuboid or a sphere. The authors showed that the magnitude of the power flux density after passing the object is higher in a cuboid, but the focusing characteristics are better in a sphere. They
The challenging world of Terahertz radiation and imaging
… , Proceedings of the …, 2011
THz propagation through materials may reveal unique macroscopic and physical properties of their internal structure without the damage associated with ionizing radiation. The generation, radiation, and detection of THz signals relays into an intermediate region between microwave and optical frequencies seen as a transition in device physics from classical transport to quantum transition. The physical properties and parameters of the antennas and electronic devices at these frequencies (0.1-10THz) will we compared with their microwave and optical counterparts, the important differences highlighted and its significance in terms of spectral bandwidth and signal-tonoise ratio for near and short range imaging systems reviewed. Finally, some of the recent significant developments in the field will be summarized and the potential applications and future challenges and opportunities identified.
Terahertz Spectroscopy and Imaging
John Wiley & Sons, Inc. eBooks, 2007
, provides an expanding selection of research monographs in all major areas of optics: lasers and quantum optics, ultrafast phenomena, optical spectroscopy techniques, optoelectronics, quantum information, information optics, applied laser technology, industrial applications, and other topics of contemporary interest. With this broad coverage of topics, the series is of use to all research scientists and engineers who need up-to-date reference books.