mid-IR Laser Radiation Research Articles

Optimization of Pump Pulse Duration and Cr:ZnSe Crystal Length for Efficient Generation of Tunable Mid-IR Laser Radiation Pumped by Laser Diode at Room Temperature

Optimization of Pump Pulse Duration and Cr:ZnSe Crystal Length for Efficient Generation of Tunable Mid-IR Laser Radiation Pumped by Laser Diode at Room Temperature

Application of continuous wave quantum cascade laser in combination with CIVP spectroscopy for investigation of large organic and organometallic ions.

Rapidly developing mid-infrared quantum cascade laser (QCL) technology gives easy access to broadly tunable mid-IR laser radiation at a modest cost. Despite several applications of QCL in the industry, its usage for spectroscopic investigation of synthetically relevant organic compounds has been limited. Here, we report the application of an external cavity, continuous wave, mid-IR QCL to cryogenic ion vibrational predissociation spectroscopy to analyze a set of large organic molecules, organometallic complexes, and isotopically labeled compounds. The obtained spectra of test molecules are characterized by a high signal-to-noise ratio and low full width at half-maximum-values, allowing the assignment of two compounds with just a few wavenumber difference. Data generated by cw-QCL and spectra produced by another standard Nd:YAG difference-frequency generation system are compared and discussed.

Measurement of the absorption coefficient of a periodically poled LiNbO3 crystal at a radiation wavelength of 3 μm

Problem formulating. In the case of nonlinear-optical conversion of high-power laser radiation in nonlinear-optical crystals the optical absorption leads to a nonuniform heating of the crystals, which results in the violation of phase matching conditions, the formation of defects, and optical damage. Goal. Measurements of optical absorption coefficient of the periodically poled lithium niobate (PPLN) crystal at 3 μm radiation wavelength using the piezoelectric resonance laser calorimetry (PRLC). Result. The optical absorption coefficient of PPLN crystal at 3.045 μm radiation wavelength was measured using the piezoelectric resonance laser calorimetry. The value (1.15±0.15) 10⋅ -2cm-1 of absorption coefficient within the measurement error limits was independent of the initial temperature of PPLN and the incident radiation power in the ranges 293–343 K and 0.2–10 W respectively. Practical meaning. The interaction of mid-IR laser radiation with PPLN crystal was studied using the piezoelectric resonance laser calorimetry.

Comparison of novel Fe2+:Zn1-xMnxTe (x ≈ 0.3) laser crystal operating near 5 μm at 78 K with other known Mn co-doped A II-BVI solid solutions

Abstract Spectroscopic and laser output characteristics of novel Fe2+-doped Zn1-xMnxTe (x ≈ 0.3) active material are presented and compared to other known Fe2+-based materials. At ~3 μm pumping, the central laser oscillation wavelength was ~4.8 μm at 78 K and shifted to 5.15 μm at 160 K. At 4.1 μm pumping, the central oscillation wavelength was ~4.9 μm at 78 K and shifted farther to 5.25 μm at 160 K. 10-μJ-level output pulse energy was achieved. These results present a great potential of the Fe2+:Zn1-xMnxTe (x ≈ 0.3) crystal for mid-IR laser radiation generation.

Linear and Nonlinear Excitation of P3HT Induced by Spectral-Shaped Ultrafast Mid-IR Laser Radiation

This article discusses the linear vibrational and nonlinear electronic excitation of the organic material P3HT during processing by ultrafast laser radiation in the mid-IR spectral range. Therefore...

Surface Modifications of Poly(methyl methacrylate) Induced by Controlled Electronic and Molecular Vibrational Excitation Applying Ultrafast Mid-IR Laser Radiation

Optimizing the processing of organic photovoltaic devices by laser radiation requires a fundamental understanding of the excitation processes during laser radiation–matter interaction. Spatially an...

Observation of optical refrigeration in a holmium-doped crystal

We report the first demonstration of solid-state optical refrigeration of a Ho-doped material. A 1 mol% Ho-doped Yttrium Lithium Fluoride (YLF) crystal is cooled by mid-IR laser radiation, and its external quantum efficiency and parasitic background absorption are evaluated. Using detailed temperature-dependent spectroscopic analysis the minimum achievable temperature of a 1% Ho:YLF sample is estimated. Owing to its narrower ground- and excited-state manifolds, larger absorption cross-section, and coincidence of optimum cooling wavelength of 2070 nm with commercially available high-power and highly efficient Tm-fiber lasers, Ho^3+-doped crystals are superior to Tm^3+-doped systems for mid-IR optical refrigeration. With further improvement in material purity and increased doping concentration, they offer great potential towards enhancing the cooling efficiency nearly two-fold over the best current Yb:YLF systems, achieving lower temperatures as well as for realization of eye-safe mid-IR high-power radiation balanced lasers.

Broadband tunable source of mid-IR laser radiation for photoacoustic spectroscopy

Control over volatile products of metabolic processes in human body in exhaled air is a promising method for noninvasive medical diagnostics. The mid-IR range (2–12 μm) is of great interest for diagnostic applications of the exhaled air spectral analysis. Laser optoacoustic spectroscopy is quite attractive for detecting a large set of gaseous substances; however, high-power sources of tunable radiation are required to increase the method sensitivity. We consider the possibility of using a parametric light generator based on a BaGa4Se7 crystal as a broadband tunable mid-IR laser source for laser optoacoustic spectroscopy.

Silicon nanoparticles for nonlinear frequency conversion of mid-IR radiation

Here a new way to use silicon nanoparticles for medium-infrared photonics is suggested. This contribution is focused on solving the fundamental problem of optical interaction between subwavelength silicon resonators and mid-IR laser radiation. In this spectral range the coefficient of two-photon absorption, which is the main mechanism for limiting the efficiency of nonlinear optical processes in silicon, is close to zero. The study provides answers to the fundamental questions about high-efficient nonlinear-optical transformations of four-wave mixing, and will serve as the basis for new nonlinear devices of integrated silicon nanophotonics.

Physical Approaches to Designing a Two-Cascade Terahertz Laser Generating Difference-Frequency Radiation in a Nonlinear Optical ZnGeP2 Crystal

An optical layout of a two-cascade frequency converter of the mid-IR laser radiation into the terahertz (THz) radiation is proposed. In the first stage it is assumed to convert the Tm:YLF-laser frequency in a Cr+2:ZnSe polycrystal into the radiation with the wavelength ~2–3 μm. The second cascade can be presented as a parametric conversion of the frequencies of two laser sources operating in the ~2–3 μm range into the THz radiation via the difference-frequency mixing in a nonlinear optical ZnGeP2 crystal. The estimates of the terahertz output signal are reported.

Forecast of intense near- and mid-IR laser radiation propagation along slant atmospheric paths

The effectiveness of the use of intense radiation from different near- and mid-IR laser sources propagating along high-altitude slant optical paths is numerically estimated on the basis of the optical model of the Earth’s atmosphere developed by the authors. Different laser sources, including chemical oxygeniodine laser (COIL), chain chemical DF laser, and carbon-monoxide (CO) laser are considered with different optical weather conditions taking into account linear and nonlinear optical effects. A COIL source is shown to be the most preferable in terms of the total laser power transmitted along a path, because of weak atmospheric attenuation and minimal effects of nonlinear factors. In addition, this laser source shows the best performance in terms of the mean radiation intensity at a receiver. Among chemical multiwavelength lasers, DF lasers lead in terms of the power transfer function.

Lone-pair interactions and photodissociation of compressed nitrogen trifluoride.

High-pressure behavior of nitrogen trifluoride (NF3) was investigated by Raman and IR spectroscopy at pressures up to 55 GPa and room temperature, as well as by periodic calculations up to 100 GPa. Experimentally, we find three solid-solid phase transitions at 9, 18, and 39.5 GPa. Vibrational spectroscopy indicates that in all observed phases NF3 remains in the molecular form, in contrast to the behavior of compressed ammonia. This finding is confirmed by density functional theory calculations, which also indicate that the phase transitions of compressed NF3 are governed by the interplay between lone‑pair interactions and efficient molecule packing. Although nitrogen trifluoride is molecular in the whole pressure range studied, we show that it can be photodissociated by mid-IR laser radiation. This finding paves the way for the use of NF3 as an oxidizing and fluorinating agent in high-pressure reactions.

On the possibility of the generation of high harmonics with photon energies greater than upon interaction of intense mid-IR radiation with neutral gases

Based on the analytical quantum-mechanical description in the framework of the modified strong-field approximation, we have investigated high harmonic generation of mid-IR laser radiation in neutral gases taking into account the depletion of bound atomic levels of the working medium and the electron magnetic drift in a high-intensity laser field. The possibility is shown to generate high-order harmonics with photon energies greater than under irradiation of helium atoms by intense femtosecond laser pulses with a centre wavelength of .

On the potential of mid-IR lasers for generating high harmonics with subnanometer wavelengths in gases

The influence of the magnetic field of a laser pulse and the depletion of bound levels of working-medium atoms on the generation of high harmonics of mid-IR laser radiation in gases is investigated using numerical quantum-mechanical calculations. The maximum attainable spectral widths of high harmonics are estimated for model atoms with different ionisation potentials taking into account the aforementioned limiting effects. It is shown (within a two-dimensional model) that high harmonics with wavelengths to several angstroms can be generated by irradiating helium atoms with high-power femtosecond pulses of a laser [] with a centre wavelength of 3.9 μm. The possibility of observing experimentally relativistic effects using modern desktop mid-IR laser sources is demonstrated.

Direct Analysis of Single Cells by Mass Spectrometry at Atmospheric Pressure

Analysis of biochemicals in single cells is important for understanding cell metabolism, cell cycle, adaptation, disease states, etc. Even the same cell types exhibit heterogeneous biochemical makeup depending on their physiological conditions and interactions with the environment. Conventional methods of mass spectrometry (MS) used for the analysis of biomolecules in single cells rely on extensive sample preparation. Removing the cells from their natural environment and extensive sample processing could lead to changes in the cellular composition. Ambient ionization methods enable the analysis of samples in their native environment and without extensive sample preparation.1 The techniques based on the mid infrared (mid-IR) laser ablation of biological materials at 2.94 μm wavelength utilize the sudden excitation of water that results in phase explosion.2 Ambient ionization techniques based on mid-IR laser radiation, such as laser ablation electrospray ionization (LAESI) and atmospheric pressure infrared matrix-assisted laser desorption ionization (AP IR-MALDI), have successfully demonstrated the ability to directly analyze water-rich tissues and biofluids at atmospheric pressure.3-11 In LAESI the mid-IR laser ablation plume that mostly consists of neutral particulate matter from the sample coalesces with highly charged electrospray droplets to produce ions. Recently, mid-IR ablation of single cells was performed by delivering the mid-IR radiation through an etched fiber. The plume generated from this ablation was postionized by an electrospray enabling the analysis of diverse metabolites in single cells by LAESI-MS.12 This article describes the detailed protocol for single cell analysis using LAESI-MS. The presented video demonstrates the analysis of a single epidermal cell from the skin of an Allium cepa bulb. The schematic of the system is shown in Figure 1. A representative example of single cell ablation and a LAESI mass spectrum from the cell are provided in Figure 2.

Direct Analysis of Single Cells by Mass Spectrometry at Atmospheric Pressure

Analysis of biochemicals in single cells is important for understanding cell metabolism, cell cycle, adaptation, disease states, etc. Even the same cell types exhibit heterogeneous biochemical makeup depending on their physiological conditions and interactions with the environment. Conventional methods of mass spectrometry (MS) used for the analysis of biomolecules in single cells rely on extensive sample preparation. Removing the cells from their natural environment and extensive sample processing could lead to changes in the cellular composition. Ambient ionization methods enable the analysis of samples in their native environment and without extensive sample preparation.1 The techniques based on the mid infrared (mid-IR) laser ablation of biological materials at 2.94 μm wavelength utilize the sudden excitation of water that results in phase explosion.2 Ambient ionization techniques based on mid-IR laser radiation, such as laser ablation electrospray ionization (LAESI) and atmospheric pressure infrared matrix-assisted laser desorption ionization (AP IR-MALDI), have successfully demonstrated the ability to directly analyze water-rich tissues and biofluids at atmospheric pressure.3-11 In LAESI the mid-IR laser ablation plume that mostly consists of neutral particulate matter from the sample coalesces with highly charged electrospray droplets to produce ions. Recently, mid-IR ablation of single cells was performed by delivering the mid-IR radiation through an etched fiber. The plume generated from this ablation was postionized by an electrospray enabling the analysis of diverse metabolites in single cells by LAESI-MS.12 This article describes the detailed protocol for single cell analysis using LAESI-MS. The presented video demonstrates the analysis of a single epidermal cell from the skin of an Allium cepa bulb. The schematic of the system is shown in Figure 1. A representative example of single cell ablation and a LAESI mass spectrum from the cell are provided in Figure 2.

Synchrotron study of laser-thermally oxidized thin titanium films

The features of oxidation of thin titanium films on single-crystal silicon have been investigated and the character and mechanism of the action of mid-IR laser radiation on the oxidation of these films in the temperature range 400–500°C have been established. The effects of “laser acceleration” and “laser breaking” of the oxide film growth are revealed. X-ray diffraction data and X-ray absorption near-edge structure spectra of the grown oxides are reported and the change in the phase composition of the oxide films is explained by resonant absorption of laser radiation.

Laser swelling of soft biological tissue by IR pulses

The temporal dynamics of biological tissue swelling under the effect of mid-IR laser radiation is considered theoretically following the experimental investigation published earlier. The probable mechanism of laser swelling is suggested. This mechanism consists of deformation of tissue protein base by vapor pressure, which appears due to evaporation of tissue water. The formation and relaxation of a hump on the surface was determined by both mechanical properties (elastic, plastic) and porosity of material providing water vapor transfer within tissue. It is found that these mechanisms can lead to the formation of both transient and stationary hump structures on the surface. To describe the hump relaxation, we consider a new, evaporation-condensation, mechanism of heat transfer within the region of biotissue with microchannels. This mechanism allows us to explain the value of relaxation time of the hump measured in experiment.

Beam shape analysis of waveguide delivered infrared lasers

A comprehensive theoretical model is developed to describe mid-IR laser radiation propagation in an optical cylindrical waveguide. The effects of various parameters of the beam as well as of the wave- guide on the output beam shape are studied and analyzed. Parameters such as beam coupling misalignment, waveguide diameters, and inner wall roughness are studied. The same conditions are applied in the the- oretical calculations as well as in the experiments. Good agreement be- tween the theoretical and experimental results is found. © 2002 Society of

Birefringence compensation, improved fringe contrast and trimming in an integrated asymmetric Mach–Zehnder interferometer using mid-IR laser processing

Tuning of an asymmetric Mach–Zehnder interferometer using mid-IR laser radiation is demonstrated. The device birefringence is compensated for by processing at the surface above one of the arms with 10.6 μm light from a CO 2 laser. The spectral contrast of the component is improved from ∼7 to ∼12 dB for the TE and TM eigenstates, respectively to ∼20 dB for both eigenstates by balancing the optical energy in each arm before the output coupler.