Source Of Mid-infrared Radiation Research Articles

Single quantum well diodes from GaInAsBi emitting at wavelengths up to 2.5 μm

Ga0.53In0.47As1−xBix/Al0.48In0.52As single quantum wells were grown by molecular-beam epitaxy on InP substrates with bismuth content as high as 7% in the well layer. The electroluminescence spectra with a peak wavelength as long as 2.5 μm was observed after applying electric bias on p-n diodes fabricated from these epitaxial structures. It has been shown that both the peak wavelength and the emitted light intensity change only slightly when the temperature of the experiment is varied from 10 °C to 60 °C. It was concluded that quaternary bismides grown on InP could be a prospective new technological system for the fabrication of mid-infrared radiation sources.

Watt-scale super-octave mid-infrared intrapulse difference frequency generation

The development of high-power, broadband sources of coherent mid-infrared radiation is currently the subject of intense research that is driven by a substantial number of existing and continuously emerging applications in medical diagnostics, spectroscopy, microscopy, and fundamental science. One of the major, long-standing challenges in improving the performance of these applications has been the construction of compact, broadband mid-infrared radiation sources, which unify the properties of high brightness and spatial and temporal coherence. Due to the lack of such radiation sources, several emerging applications can be addressed only with infrared (IR)-beamlines in large-scale synchrotron facilities, which are limited regarding user access and only partially fulfill these properties. Here, we present a table-top, broadband, coherent mid-infrared light source that provides brightness at an unprecedented level that supersedes that of synchrotrons in the wavelength range between 3.7 and 18 µm by several orders of magnitude. This result is enabled by a high-power, few-cycle Tm-doped fiber laser system, which is employed as a pump at 1.9 µm wavelength for intrapulse difference frequency generation (IPDFG). IPDFG intrinsically ensures the formation of carrier-envelope-phase stable pulses, which provide ideal prerequisites for state-of-the-art spectroscopy and microscopy.

Controlling single harmonic enhancement in laser-produced plasmas

We compare the plasma emission and harmonic generation spectra in the cases of resonance enhancement of single harmonic using various laser-produced plasmas. The analysis of these spectra showed that the enhancement of harmonics depended on the oscillator strengths of the nearby ionic transitions rather than the plasma emission transitions. To prove it, we used the tunable source of mid-infrared radiation from an optical parametric amplifier (1200–1600 nm) and the fixed wavelength source (810 nm) of femtosecond pulses. The comparison of resonantly enhanced and featureless plateaulike harmonic spectra from different laser-produced plasmas, as well as their plasma emissions, confirmed this assumption.

Detection of atmospheric multi-component based on a single quantum cascade laser

Quantum cascade lasers (QCLs) are relatively new sources of mid-infrared radiation (between 2.5 m and 25 m), and are very well suited to the application of in-field trace gas sensing, mainly due to their superiority of being robust, compact, wavelength-versatile, narrow line width and low power consumption. All these advantages make the laser absorption spectroscopy based on QCL light sources become one of the most popular technologies for the quantitative chemical detection in a variety of fields including atmospheric environmental monitoring, chemical analysis, industrial process control, medical diagnostics, security or bio-medical studies, etc. In the present work, a highly sensitive mid-infrared gas sensor employing a single continuous-wave distributed feedback QCL and an astigmatic multi-path optical absorption cell is demonstrated for the simultaneous measurement of atmospheric carbon monoxide (CO), nitrous oxide (N2O) and water vapor (H2O). By combining with an adaptive Savitzky-Golay (S-G) filter signal processing algorithm, the detection sensitivity and spectral resolution of the QCL sensor system are significantly improved. Compared with the traditional wavelet transform based signal de-noising technique, the developed adaptive S-G smoothing filter shows obvious advantages in terms of computational efficiency and selection of the optimal filter parameters, namely only two filter parameters (the width of the smoothing window and the degree of the smoothing polynomial) need to be considered. Currently, the QCL sensor system is estimated for the long term measurement of ambient air in laboratory environment. The results show that measurement precisions of 8.20 ppb (1 ppb=10-9) for CO, 7.90 ppb for N2O, and 64.00 ppm (1 ppm=10-6) for H2O at 1 s time resolution and 1 atmospheric pressure (atm) are obtained by using the quadratic differential detection scheme, which can be further improved to 1.25 ppb (for CO), 1.15 ppb (for N2O) and 35.77 ppm (for H2O) by increasing average time up to 85 s, respectively. On the whole, the QCL sensor system has significant features of portability and low-cost, moreover, it can be easily modified for the real-time analysis of other gas molecules through the choosing of corresponding QCL light sources. The QCL gas sensor can be widely used in the field of atmospheric chemistry and other applications. Future work will focus on H2O induced broadening coefficients for CO and N2O transitions near 4.57 m, which will be updated for the developed multi-species QCL sensor system, thus resolving the influence of water vapor broadening effect and achieving the measurement of gas concentration in a high humid environment with sub-percent precision.

Dysprosium thiogallate laser: source of mid-infrared radiation at 2.4, 4.3, and 5.4 µm

Various Dy:PbGa2S4 laser-active material energy transitions originating from the 6H9/2 + 6F11/2 or 6H11/2 energy level were investigated, and the mid-infrared radiation generation has been demonstrated. The Dy:PbGa2S4 laser was pumped by a 1.32-µm free-running Nd:YAG laser or laser diode radiation corresponding to the Dy:PbGa2S4 absorption peak. The Dy:PbGa2S4 crystal was placed in the stable optical resonator with the mirrors chosen according to the required generated wavelength. New laser wavelengths of 2.4 and 5.4 µm were generated from the Dy:PbGa2S4 laser at room temperature. Laser output characteristics at 4.3 µm are also presented.

Widely tunable, all-polarization maintaining, monolithic mid-infrared radiation source based on differential frequency generation in PPLN crystal

We present a difference frequency generation based (DFG) mid-infrared (mid-IR) laser source using an all-polarization-maintaining-fiber (all-PM) amplifier capable of simultaneous amplification of 1064 nm and 1550 nm signals. The amplifier incorporates a single piece of a standard erbium:ytterbium (Er:Yb) co-doped double-clad (DC) active fiber and a limited number of off-the-shelf fiber-based components. Excited by a single 9 W multimode pump, the amplifier delivered over 12.1 dB and 17.8 dB gain at 1 µm and 1.55 µm, respectively. Due to an all-PM configuration, the amplifier was exceptionally convenient for DFG of mid-IR radiation in periodically polled lithium niobate (PPLN) crystal, yielding an output power of ~200 µW in a wide spectral range spanning from 3300 to 3470 nm.

Improved Performance of Plasmonic Thermal Emitter via Incorporation of Gold Nanoparticles

The improved performance of plasmonic thermal emitter by incorporating randomly distributed gold nanoparticles is demonstrated in the mid-infrared range. Gold films with different thicknesses were deposited on top of the devices and then annealed to form separate nanoparticles. Experimental results showed that the size and distribution of nanoparticles depend mainly on the gold film thickness, rather than annealing temperature. It is observed that thermal emitters with smaller particles embedded exhibit significant enhancement in emission intensity. It is the strong scattering between gold nanoparticles that contributes to the enhanced infrared thermal emission. As an efficient mid-infrared radiation source, this device has the potential to be applied in various fields such as second harmonic generation of infrared source and biosensors.

Twelve type II-P supernovae seen with the eyes ofSpitzer

Core-collapse supernovae (CC SNe), especially those of type II-plateau (II-P), are thought to be important contributors to cosmic dust production. The most obvious indicator of the presence of newly-formed and/or pre-existing dust is the time-dependent mid-infrared (MIR) excess coming from the environment of SNe. Our goal was to collect publicly available, previously unpublished measurements on type II-P (or peculiar IIP) SNe from the Spitzer database. The temporal changes of the observed fluxes may be indicative of the underlying supernova, while spectral energy distribution (SED) fitting to the fluxes in different IRAC channels may reveal the physical parameters of the mid-IR radiation, presumably due to warm dust. IRS spectra were extracted and calibrated with SPICE, while photometric SEDs were assembled using IRAF and MOPEX. Calculated SEDs from observed fluxes were fit with simple dust models to get basic information on the dust presumed as the source of MIR radiation. We found twelve SNe satisfying the criterion above, observed at late-time epochs (typically after +300 days). In three cases we could not identify any point source at the SN position on late time IRAC images. We found two SNe, 2005ad and 2005af, which likely have newly-formed dust in their environment, while in the other seven cases the observed MIR flux may originate from pre-existing circumstellar or interstellar dust. Our results support the previous observational conclusions that warm new dust in the environment of SNe contributes only marginally to cosmic dust content.

Mid-infrared radiation sources based on coupled disk cavities

IR radiation sources representing optically coupled semiconductor disk lasers with active regions based on quantum-confined GaInAsSb/AlGaAsSb heterostructures have been created. It is shown that this system ensures single-mode generation in optically coupled cavities operating on whispering gallery modes (WGMs). Conditions for WGM lasing are determined as dependent on the distance between two optically coupled disk cavities.

A Possible Dusty Microplasma Source of Mid-Infrared Radiation

Microplasmas have been discussed as novel sources of photons in the ultraviolet to infrared (IR). Recently, the addition of dust to a microplasma has been discussed in various contexts. In this paper, we theoretically investigate thermal radiation from heated dust in microplasmas to explore dusty microplasmas as possible sources of mid-IR (MIR) radiation. We consider grains that are selective absorbers (and, thus, selective emitters) in the MIR. Heating of the dust by impinging plasma and cooling of the dust by conduction and thermal radiation are studied for a range of plasma parameters and dust sizes. Possible applications of such sources may include spectroscopy since many gases absorb strongly in the MIR.

Development of Digital Signal Processor Controlled Quantum Cascade Laser Based Trace Gas Sensor Technology

This paper reports the design and integration of a custom digital-signal-processor (DSP) system into a pulsed quantum-cascade-laser (QCL)-based trace gas sensor to improve its portability, robustness, and operating performance. Specifically, this paper describes the implementation of a custom prototype DSP data acquisition and system controller based on the Texas Instruments TMS320F2812 for embedded control and processing. In addition, the sensor incorporates oversampling by taking advantage of the high-speed conversion capabilities of an analog-to-digital converter, which is embedded within the DSP. A carbon monoxide sensor, employing a thermoelectrically cooled, pulsed 4.6-mum distributed feedback QCL as a mid-infrared radiation source, is used to evaluate the performance characteristics of such a DSP controlled spectroscopic gas sensor

Excitation paths in RE-doped III–V semiconductors

Optical properties of III–V compound semiconductors are frequently engineered by doping with RE ions. In that way narrow emission bands with a temperature-independent wavelength can be obtained. In order to achieve intense luminescence, efficient and temperature-stable excitation mechanism, as well as suppression of nonradiative recombinations of the optical dopant is required. Investigation of these processes is usually done by analysis of thermal effects and by excitation spectroscopy. Recently, we have proposed that energy transfer mechanisms in optically doped semiconductor hosts can be conveniently studied using two-color experiments combining band-to-band pumping with spectral probing by a free-electron laser as a tunable source of mid-infrared radiation. In this paper, we review shortly some results obtained by this novel approach on InP:Yb, and discuss perspectives of future research.

Generation of infrared radiation by stimulated Raman scattering in para-hydrogen crystal at 5 K.

We report the preliminary results of our experiments with stimulated Raman scattering in para-hydrogen crystal aimed at developing a continuously tunable laboratory laser source of mid-infrared radiation. With laser pulses at 532 nm, a conversion efficiency for the first Stokes beam of as much as 20% in the forward direction was observed through a single-pass, 5-cm-long crystal. Generation of mid-infrared pulses at 4.5 microm was achieved by use of the output of a near-infrared pulsed laser (1.6 microm, 3 ns), and an absorption spectrum of gaseous CD4 molecules was successfully recorded. These results suggest use of the solid para-hydrogen Raman shifter as a promising light source for mid-infrared spectroscopy.

Calorimetric investigation of intersublevel transitions in charged quantum dots

Intersublevel transitions in InGaAs quantum dots (QD's) are observed by means of midinfrared Fourier transform calorimetric absorption spectroscopy. This technique permits one to measure spectrally resolved the heating ofa sample illuminated by a midinfrared radiation source. Thus, effectively a QD bolometer for the midinfrared energy range has been realized, allowing for sensitive absorption studies. Absorption peaks observed in the 70 to 110 meV range are attributed to electron intersublevel transitions based on a comparison to exciton properties derived from photoluminescence and photoluminescence-excitation measurements. For charge-tunable QD's in a space charge region, the population of ground and excited electron sublevels can be changed by the applied reverse bias, allowing for an identification of the observed intersublevel transitions on the basis of their charging dependence. Charging-dependent energy shifts and intensity changes of the intersublevel absorption peaks are ascribed to few-particle effects and to Pauli blockade effects, respectively. The QD intersublevel absorption cross section is estimated to he of the order of 10 - 1 3 cm 2 , the according absorption coefficient is comparable to that of QD interband (exciton) transitions.