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Laser spectroscopy based trace gas detection systems are implemented in various applications: industry, medicine, homeland security, environmental monitoring and several more [1]. More sophisticated applications require simultaneous monitoring of several gas species, that possess strong absorption lines in the mid-IR wavelength region. This usually requires using several independent laser sources...
Molecular precision spectroscopy opens new perspectives on tests of fundamental laws of physics and of fundamental constants variation [1]. The mid infrared (IR) is a key region for molecular spectroscopy, and the efforts towards the development of versatile, spectrally pure, and tunable coherent sources in this region have been constantly growing in the last decade. A convenient way to generate a...
Diode-pumped erbium-doped fluoride glass (Er:FG) fiber lasers operating near the water absorption peak have a potential use in medical [1] and spectroscopy [2] applications. However, their efficiency is generally limited to the maximum Stokes efficiency limit of ∼35%. Until now, the only way demonstrated to exceed this limit takes advantage of an energy transfer upconversion process (ETU). Nonetheless,...
Quantum cascade lasers (QCLs) are powerful sources of coherent radiation covering the frequency range from mid-infrared to terahertz. In the terahertz frequency range the active region is normally realized using a GaAs/AlxGa1−xAs semiconductor heterostructure. This material system enables a variable conduction band offset by changing the Al-content in the barrier layers without introducing a significant...
High-energy, few-cycle THz pulse generation by high-intensity (∼1018 W/cm2) femtosecond laser with plasma mirrors have received significant attention in recent years [1-3]. This novel THz source has the potential of generating large bandwidth millijoule pulse energies, opening up applications in THz nonlinear optics, single-shot imaging and spectroscopy [4]. Solid density plasma shaping has already...
Single mode THz QCLs have already shown their huge potential for metrological grade THz spectroscopy [1, 2] while, on the contrary, continuous-wave multimode broadband operation has only recently been demonstrated [3]. These sources show a comb emission regime with up to 600 GHz spectral coverage. This kind of sources are very promising for metrological-grade applications, such as high precision spectroscopy,...
Terahertz (THz) quantum-cascade lasers (QCLs) constitute a very promising candidate for compact, wide bandwidth, integrated frequency combs [1, 4-7]. QCLs based on heterogeneous cores display the widest spectral coverage reaching more than one octave [2]. The possibility to engineer the gain profile turns out to be fundamental also with respect to dispersion compensation in order to extended the comb...
Quantum cascade lasers (QCLs) are small and powerful sources covering a wide spectral range from infrared to terahertz (THz) radiation. When fabricated in metal-metal ridge waveguides, the output aperture is typically very small compared to the long wavelength of THz radiation, therefore it is challenging to obtain collimated, directional emission from such devices.
Since the first theoretical prediction by Yang [1] and the first experimental realization [2] interband cascade lasers (ICL) became more and more established for gas sensing applications. The ICL combines the cascading of several active stages known from the quantum cascade laser (QCL) and the interband transition of the diode lasers (DL) enabled by the semimetallic interface between InAs and GaSb...
Interband cascade lasers (ICLs) [1, 2] combine two concepts for semiconductor lasers, in particular the long carrier lifetime of photodiodes together with the voltage-efficient cascading of the quantum cascade laser. The low threshold power makes them very attractive for mobile systems used for spectroscopy, process control or medical applications. To date no suitable overgrowth process exists for...
Modem western societies suffer from diseases of civilization which are mainly associated with smoking, fatty diets and obesity. One of those is the Gastroesophageal reflux disease (GERD) often also loosely called heartburn. GERD can in some cases lead to an abnormal change of cells (metaplasia) in the lining of the oesophagus. This syndrome is defined as Barrett's oesophagus (BO). If the oesophagus...
Extended-cavity quantum cascade lasers (EC-QCLs) enable mode-hope-free frequency sweeps in the mid-infrared region over ranges in excess of 100 cm−1, at speeds up to 1 THz/s and with a 100-mW optical power level. This makes them ideally suited for broadband absorption spectroscopy and for the simultaneous detection of multiple gases. On the other hand, their use for precision spectroscopy has been...
Pulsed fiber laser operating at 2000 nm is of great interest in applications such as LIDAR system using very low atmospheric absorption bands, material processing for transparent plastics, etc. Thulium- and holmium-doped silicate glass fibers have been the best choice as a gain medium for the fiber lasers. In particular, a holmium-doped fiber laser (HDFL) has drawn much attention because it opened...
Novel designs and fabrication of multi-wavelength mid-IR quantum cascade lasers [1, 2] have triggered highly attractive progress in instrumental developments towards compactness and multispecies detection, addressing the demands for high-precision and selective measurements of a large variety of molecular species, as well as for compact, robust and field deployable gas analyzers. This work highlights...
Molecular spectroscopy can potentially achieve very high frequency resolution, but transitions are generally very weak. The scientific community has tried to tackle this problem by increasing the interaction path length using extremely long cells, sophisticated multipass cells and Fabry-Perot cavities. As such, molecular spectroscopic methods do not lend themselves naturally to miniaturization. Compact...
Since many molecules possess their specific fingerprint in the mid-infrared (MIR) wavelength regime, MIR absorption spectroscopy is a powerful technique to determine the composition and species concentration of an unknown substance [1]. Due to the broad MIR-wavelength operation regime from 2.63 μm up to 250 μm, the high quantum efficiency and the customizable output wavelength, Quantum Cascade Lasers...
The development of a compact, continuous wave (CW), room-temperature, broadly-tunable terahertz (THz) laser source is of great interest for a number of applications ranging from biomedical imaging and indoor communication to spectroscopy, security and defence. Among the usually used laser sources, direct quantum cascade lasers (QCLs) and semiconductor mixers of mid-IR QCLs are regarded as most popular...
Quantum cascade lasers (QCLs) are powerful semiconductor light sources, based on intersubband transitions, which can be tailored to operate in the mid-infrared (MIR) region of the electromagnetic spectrum [1]. This region is of particular interest for applying various gas absorption spectroscopy schemes, as many of the characteristic transitions of several gas molecules occur at energies that are...
Tm, Ho co-doped crystals are prospective laser materials for realization of compact laser systems emitting at 2 μm, interesting for remote sensing and medical applications [1]. Recently [2, 3] diode-pumped microchip lasers on monoclinic double tungstate crystals co-doped with Tm3+ and Ho3+ions were demonstrated. However the study of influence different doping ions concentrations on laser characteristics...
We present a side-respectively end-pumped Nd:YAG laser system at a laser wavelength of 1116 nm. The third harmonic of this wavelength at 372 nm can be used for LIDAR detection of molecular iron in the middle atmosphere at the height of about 70 to 120 km. Such measurements give information about temperature profiles and wind speeds in this atmospheric region and thus help in validating and calibrating...
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