1,721,157 research outputs found
"Size-dependent lattice contraction in CdS1-xSex nanocrystals embedded in galass observed by Raman scattering"
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Quartz-Enhanced Photoacoustic Spectroscopy: A Review
Full text linkA detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis
Demonstration of high wall plug efficiency THz QCLs: investigation of the optical, electronic and thermal performance
No full textHigh-performance terahertz quantum cascade lasers operating at 106 μm: analysis of the thermal and electronic properties
No full textWe report on the investigation of the electronic and thermal properties of high performance terahertz (THz) quantum cascade lasers (QCLs) based on a bound-to-continuum scheme and grown by molecular beam epitaxy (MBE) by a commercial provider. The local lattice temperatures, the subband electronic temperatures and the electron-lattice coupling constant have been extracted from the analysis of microprobe band-to-band photoluminescence spectra measured on devices operating in continuous wave (cw). We found that the electronic distributions in both the active region and the injector are thermalized and that all the subbands share the same electronic temperatures. The measured device thermal conductance C(*) = 4.6 W/(Kxm) reflects the good thermal management of the investigated devices. The electron-lattice coupling constant alpha = 78.5 Kcm(2)/kA is a factor 1.65 higher than in mid-IR QCLs thus indicating the inefficient cooling of the electronic ensemble caused by the strong reduction of electron-LO phonons scattering channels
Deep-level electroluminescence at 3.5 μm from semi-insulating InP layers ion implanted with Fe
No full textMid-infrared electroluminescence associated with internal transitions of Fe2+ deep levels in semi-insulating InP:Fe layers, obtained by ion implantation at high doses in the range 1013-1015 cm-2, is reported. The characteristic line spectrum corresponding to the symmetry-allowed d-shell transitions of Fe2+ can be observed up to 30 K, while a broader band emission is detectable up to 200 K. The estimated conversion efficiency of electrical into mid-IR optical power is approx. 4 × 10-5, a factor of approx. 40 larger than previously reported values in MOCVD-grown planar electroluminescent devices
Time resolved μ-photoluminescence assessment of the heat tranfer processes in quantum cascade lasers
No full textFilling the terahertz gap
No full textRecent breakthroughs in nanotechnologies are pushing up the efficiency of compact semiconductor laser sources
and detectors of radiation in the terahertz (THz) range of the electromagnetic spectrum. At these frequencies, many
molecules have their spectroscopic fingerprints due to rotational and vibrational transitions. Hence, long-dreamed
killer applications of THz photonics such as sensing, imaging, diagnostics, coherent spectroscopy in strategic fields
like medicine, microelectronics, petrochemical industry, forensic science, cultural heritage are coming true
High Fe2+/3+ trap concentration in heavily compensated implanted InP
No full textHigh Fe concentrations (up to 2 × 1019 cm-3) have been implanted in n-doped InP to compensate the substrate donors. The resulting semi-insulating layers have been investigated by current-voltage (I-V) measurements and photo-induced current transient spectroscopy (PICTS) analyses to characterise the Fe activation process and to study the Fe related deep levels. The activation of the Fe2+/3+ trap has been assessed by the identification of the deep level located at EC - 0.64 eV. The outcomes of the PICTS measurements have been correlated with the electrically active Fe concentration calculated from a numerical simulation of the I-V characteristics. We observe an increasing linear relation between the electrically active Fe concentration and the substrate doping density, with a maximum active Fe concentration as high as 2 × 1018 cm-3, i.e. more than an order of magnitude above the equilibrium Fe solid solubility. These data are presented and their implications discussed
Deep-level electroluminescence at 3.5 Âμm from semi-insulating InP layers ion implanted with Fe
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