Absorption by CS<Subscript>2</Subscript> molecules on “hot” band emission lines from a TEA CO<Subscript>2</Subscript> laser

We have measured absorption of emission from a TEA CO₂ laser, lasing on hot band lines, in pure CS₂ and a mixture of CS₂ with air, and we have determined the optimal lines for optical excitation. Numerical modeling has shown that as the peak intensity of the pump radiation is increased, we observe absorption saturation, the extent of which decreases as the pressure increases. The major factor responsible for absorption saturation is the “rotational bottleneck” effect. Depending on the peak intensity of the radiation, addition of a buffer gas can lead to an increase or decrease in the absorption. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 61–66, January–February, 2007.     

Change in the optical properties of paper when exposed to the magnetic component of a high-frequency electromagnetic field

We have used laser Stokes polarimetry to study changes in the structure of paper for offset printing when exposed to a high-frequency electromagnetic field. We have shown that the effect of a high-frequency electromagnetic field on paper appears as a decrease in the structural ordering of the material and a change in the shape of the indicatrix of the reflected radiation power from an He-Ne laser at the wavelength 632.8 nm, a decrease in the bidirectional reflection and transmission coefficients of the paper. We have established that when the force lines of the magnetic component of the high-frequency electromagnetic field are oriented perpendicular to the plane of the sheet of paper, we observe a more substantial decrease in the anisotropy in the surface layer and within the interior (the volume) of the paper than when the lines of force are oriented parallel to the plane of the paper. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 421–426, July–August, 2007.     

Study of structural phase transitions in YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6+δ</Subscript> by x-ray photoelectron spectroscopy

We have used x-ray photoelectron spectroscopy to investigate the charge state of oxygen found in the basal structural plane of YBa₂Cu₃O₆+γ.. We have observed a change in this state after thermal treatment, with a transition to the adjacent structural phase region. We have shown that changes in the charge state of oxygen can be used as an indicator of structural changes occurring in YBa₂Cu₃O₆+δ.. We have found that the rate of structural relaxation yttrium barium cuprate depends on the amount of structural water it contains. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 195–198, March–April, 2007.     

Single longitudinal mode pulse from a TEA CO<Subscript>2</Subscript> laser by using a three-mirror resonator with a Fabry–Pérot etalon

We present a single longitudinal mode (SLM) TEA CO₂ laser oscillation by using a three-mirror resonator with a Fabry–Pérot etalon. The etalon was inserted in the optical path taken out from the main resonator of the CO₂ laser for protecting the etalon from damage on the surface. A modified numerical model of the three- mirror resonator was investigated for design the laser. SLM pulse from the TEA CO₂ laser was achieved, and the experimentally measure values were found to have good agreement with the numerical model. The maximum pulse energy of reliable SLM emission is obtained in excess of 200 mJ at 9.57 μm. The reliability of producing SLM pulses was higher than 90%, and there was no damage on the etalon PACS  42.55.Lt; 42.60.Fc     

Effect of intravenous laser irradiation on the molecular structure of blood and blood components

We present the results of a spectral study of the effect of low-intensity laser radiation on the molecular structure of blood and blood components. Analysis of the Fourier transform IR absorption spectra of blood confirmed the changes we observed previously in the oxygen transport characteristics of blood with intravenous exposure to the emission from a He-Ne laser. We show that structural and conformational changes in the hemoglobin tetramer, initiated by laser-induced photoreactions between Hb and oxygen, lead to characteristic changes in the shape and intensity of the IR bands for NH stretching vibrations, and also the amide I and amide II absorption bands. In the IR spectra of irradiated blood samples, we note increased absorption in the bands for stretching vibrations of the phosphate groups (945–1280 cm⁻¹), which is evidence for an increase in the nucleic acid content (DNA, RNA). In the spectra of plasma and erythrocytes prepared from irradiated blood, there are no changes in this region of the IR spectrum. At the same time, in the IR spectra of samples of irradiated plasma, the intensity of the bands for stretching vibrations of the CH₂ groups increases substantially. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 106–112, January–February, 2006.     

Accuracy in determination of the temperature and partial pressure of CO<Subscript>2</Subscript> in CO<Subscript>2</Subscript>:N<Subscript>2</Subscript>:H<Subscript>2</Subscript>O:NO<Subscript>2</Subscript> mixtures by multiple-frequency laser probing

We present the results of analysis of the errors introduced by hot-band transitions 11¹0-01¹1, 03¹0-01¹1, 12⁰0-12⁰1 of the CO₂ molecule and the absorption lines of the H₂O and NO₂ molecules in determination of the temperature and partial pressure of CO₂, included in the gas mixture CO₂: N₂:H₂O: NO₂ at atmospheric pressure, by multiple-frequency laser probing using a CO₂ laser tunable over the lines of the 00⁰1-[10⁰0,02⁰0]_I,II ground-state laser transitions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 810–815, November–December, 2007.     

Role of coherence in interaction of opticalradiation with macromolecules

Based on analysis of the properties of macromolecules in a coherent optical radiation field and taking into account experimentally established data on the specificity of the interaction between laser radiation and biomolecules (the dependence of the efficacy of the interaction on the coherence length, the presence of an effect in a region of the spectrum far away from the absorption band), we propose a mechanism for wave interaction of coherent optical radiation with macromolecules, and we construct a very simple mathematical model for such interaction. Using the mathematical model, we calculate the dependence of the vibrational energy of the macromolecule in a coherent radiation field on the coherence time and the intramolecular relaxation rate. We show that the increase in the vibrational energy of the macromolecules strongly depends on the radiation coherence length. When exposed to incoherent radiation, the vibrational energy of the biomolecules remains practically constant, while when exposed to laser radiation (coherence length ≈3 cm), the vibrational energy of the atoms increases by 2–4 orders of magnitude, leading to a change in the conformation of the biomolecules and the activity of enzymes. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 225–231, March–April, 2006.     

Tunable optical parametric oscillator based on a KTP crystal,pumped by a pulsed Ti<Superscript>3+</Superscript>:Al<Subscript>2</Subscript>O<Subscript>3</Subscript> laser

We present the characteristics of an optical parametric oscillator based on a KTP crystal, pumped with noncritical phase matching by a pulsed Ti³⁺:Al₂O₃ laser, tunable in the range 677–970 nm. Tunable generation of signal and idler waves is obtained in the ranges 1030–1390 nm and 2690–3050 nm respectively. The efficiency of conversion of the pump to the signal wave is ≈23%, which for pulses of duration ≈8 nsec ensures an energy in the range 1.0–11.5 mJ. The width of the emission spectrum for the signal wave is within the range 0.8–1.8 nm and is predominantly determined by the linewidth of the Ti³⁺:Al₂O₃ pump laser. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 3, pp. 351–356, May–June, 2007.     

Nonlinear dynamics of the dual-wavelength CO2 laser

Theoretical studies have been made of the nonlinear-dynamic modes of operation of a dual-wavelength CO₂ laser with continuous pumping by electric discharge and loss modulation in one of the lasing channels. It is shown that by varying the modulation depth and frequency, it is possible to control, over a fairly wide range, the time and energy parameters of lasing in both channels, going from regular to chaotic modes of operation. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 316–321, May–June, 2000.     

Influences of CO2 laser annealing on mechanical and laser-induced damage properties of ZrO2 thin films

Zirconium dioxide (ZrO₂) thin films were deposited on BK7 glass substrates by the electron beam evaporation method. A continuous wave CO₂ laser was used to anneal the ZrO₂ thin films to investigate whether beneficial changes could be produced. After annealing at different laser scanning speeds by CO₂ laser, weak absorption of the coatings was measured by the surface thermal lensing (STL) technique, and then laser-induced damage threshold (LIDT) was also determined. It was found that the weak absorption decreased first, while the laser scanning speed is below some value, then increased. The LIDT of the ZrO₂ coatings decreased greatly when the laser scanning speeds were below some value. A Nomarski microscope was employed to map the damage morphology, and it was found that the damage behavior was defect-initiated both for annealed and as-deposited samples. The influences of post-deposition CO₂ laser annealing on the structural and mechanical properties of the films have also been investigated by X-ray diffraction and ZYGO interferometer. It was found that the microstructure of the ZrO₂ films did not change. The residual stress in ZrO₂ films showed a tendency from tensile to compressive after CO₂ laser annealing, and the variation quantity of the residual stress increased with decreasing laser scanning speed. The residual stress may be mitigated to some extent at proper treatment parameters.     

Characterization of a Br(2P1/2)–CO2(1001-1000) transfer laser driven by photolysis of iodine monobromide

2 laser operating on the 10⁰1-10⁰0 transition at λ=4.3 μm and pumped by E –V energy transfer from Br(²P_1/2) has been demonstrated. The dynamics and performance of this device were characterized by observing the time-resolved stimulated emission and the steady-state spontaneous side fluorescence after photolysis of IBr or Br₂ by a frequency-doubled Nd:YAG laser or Ar⁺ laser, respectively. Although the E –V excitation kinetics are favorable, rapid vibrational relaxation limits laser action to CO₂ pressures of less than 1 Torr. Numerical modeling of laser pulse shapes and the dependence on IBr and CO₂ pressure and photolysis energy establish a relatively high gain of 0.33%/cm, a CO₂-pressure-dependent optical loss of 0.04–0.06%/cm, and an efficiency of 2×10^-5 4.3-μm-laser photons per incident photolysis photon. The CO₂ fluorescence after photolysis of a fixed Br₂/CO₂ gas mixture decreases as a function of photolysis time by about 30%/h, indicating the photolytic production of an important quencher. Received: 23 June 1997/Revised version: 23 September 1997     

Amplitude-detuning characteristic of a CO2 laser with biharmonic loss modulation

The nonlinear response of a CO₂ laser to biharmonic loss modulation was theoretically investigated for tuning of the radiation frequency within the limits of the amplification band. It is shown that the value and form of the amplitude-detuning characteristic (and, consequently, the temporal and energy parameters of the laser radiation) can be controlled within sufficiently wide limits by changing the modulation frequency and the phase shift of oscillations. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 43–47, January–February, 1999.     

Amplitude-detuning characteristic of a CO2 laser with simultaneous modulation of two parameters

Analytical expressions have been obtained in a linear approximation for the amplitude-detuning characteristic of a CO₂ laser with simultaneous modulation of two its parameters. It is shown that the value and form of the laser response can be controlled over a wide range by way of changing the modulation frequency, the value of the detuning, and the phase difference of the oscillations of the simultaneously modulated parameters. B. I. Stepanov Institute of Physics of the Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 190–196, March–April, 1997.     

Remote detection of sulfur dioxide by means of a CO2 laser

The possibility of remote detection of SO₂ in the 9-μm region of the spectrum by means of a TEA CO₂ laser was theoretically and experimentally investigated with regard to the real state of the atmosphere and the contribution of background concentrations of H₂O, CO₂ and NH₃ to absorption. For sounding along short paths (2L=2 km), the method of detection of small concentrations of SO₂ (at the MPC level) with the use of the lines of the CO₂-molecule regular transitions (00^o1–02^o0 band) has been devised and experimentally tested. It is shown that in sounding along longer paths (2L=6 km), a noticeable increase in sensitivity can be achieved by the generation lines of the CO₂-molecule sequential 00^o2–02^o1 band. B. I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 508–515, July–August, 1998.     

Nonlinear amplitude-tuning characteristic of a CO2 laser with pump-current modulation

The nonlinear amplitude-tuning characteristic of a CO₂ laser with discharge-current modulation was investigated by mean of numerical simulation. It is shown that in the general case the magnitude and shape of the laser response depend on the ratio between the frequency of the pump modulation and the fundamental resonance frequency of the laser. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 640–644, September–October, 1999.     

Formation of excited states of atoms and ions in laser plasma from CuInS2

Emission spectra and the energy distribution of the excited-state population density of atoms and ions in erosion laser plasma from CuInS₂ with various crystal-structure orderings are analyzed. It is shown that increased ordering of the target crystal structure causes the excited-state energies of indium atoms generated in the laser erosion plume to increase and that sulfur atoms always emit only in transitions from highly excited states. The ratio of relative ion concentrations in the laser plasma plume is Cu⁺/In⁺/S⁺ = 0.3/0.08/2, which corresponds neither to the atomic ratio of Cu/In/S (1/1/2) in the target nor to the ratio of ionization energies. The results are explained by recombination processes for ions and by the atomization specifics of the CuInS₂ target exposed to long-wavelength radiation. The atomization consists essentially of dissociative processes expressed by CuInS₂ → CuInS + S and CuInS₂ → Cu + InS + S. The electron temperature of polycrystal (single-crystal) plasma at a distance of 1 mm from the target is 0.3 eV (0.4 eV) for atoms and 1.3 eV (2.7 eV) for ions and varies negligibly for plasma up to a distance of 7 mm from the target. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 217–223, March–April, 2008.     

Laser radiation resistance of prospective materials for high-power IR optics

We have conducted comprehensive studies of resistance to radiation from a wide-aperture TEA CO₂ laser. We have classified the types of damage and the conditions for occurrence of damage and we give a qualitative explanation for the characteristic features of fracture of the materials. We have determined the thresholds for laser-induced breakdown of actual IR materials for laser apertures of 0.5–30 cm. We propose a criterion for choosing materials for high-power laser optics. Raduga State Laser Testing Center. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 68–84, October, 1998.     

Effect of the external medium on the spectral characteristics of polypropylene films doped with Eu(fod)<Subscript>3</Subscript> molecules

We have studied the effect of external factors (humidity, pressure, temperature) on the stability of the organometallic compound Eu(fod)3 (fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octadione) impregnated into polypropylene (PP) using supercritical CO₂. We have established that under the influence of external conditions, there is a decrease in the integrated intensity of the absorption band for the Eu(fod)₃ molecule and the photoluminescence (PL) of Eu³⁺ ions as a function of the properties of the medium, and in the presence of water molecules the shape of the bands for these spectra changes. We propose a physical model explaining the behavior of the absorption and photoluminescence spectra when the polypropylene films are stored under different conditions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 42–47, January–February, 2007.     

Optically pumped submillimeter laser lines from CD2Cl2 using a large tunability CW CO2 laser

Twenty-five new laser lines have been obtained in the wavelength region from 155 to 830 μm by optically pumping the CD₂Cl₂ (deuterated dichloromethane) molecule with a CW CO₂ laser having a tunability range of 300 MHz. The wavelength, polarization relative to that of CO₂ pumping radiation, and offset relative to the CO₂ center frequency were determined for all of the new lines and some other already known laser emissions. For all of them we give also the relative intensity and the optimum pressure of operation. Permanent address: Depto de Física e Química da FEIS — UNESP 15.378-000 Ilha Solteira-SP, Brazil     

Tunable te-CO2 laser-pumped formaldehyde far-infrared lasers: Offsets, assignment, and superfluorescence

Sixty and three absorption transitions in D₂CO and H₂CO, respectively, have produced a number of far infrared laser lines when they are pumped by an etalon-tuned TE-CO₂ laser. Almost all the absorption transitions pumped previously by a free runing TE-CO₂ laser have been efficiently pumped by the etalon tuned CO₂ laser and found to have offset within ±500 MHz from the line-center of the relevant CO₂ pump lines. 22 (1) absorption and 63 (4) emission lines of D₂CO (H₂CO) are assigned. Some of these lines have generated superfluorescence. In paticular, the D₂CO 319-m line pumped by CO₂-9P(32) delivered an output energy of approximately one half that of the well-known D₂O 66-m. It is shown that a large electric dipole moment and an appreciable amount of fractional population in the lower level of the pump transition of this line are responsible to the superfluorescence.