Saturable absorption of CO2-laser radiation by CH3F

A theory of the saturable absorption of pulsed CO₂-laser radiation by CH₃F is described. It is valid for arbitrary pulse shapes and durations in the rate-equation regime. The theoretical predictions agree satisfactorily with available experimental data. The effect of vibrational exchange and the influence of the Boltzmann population factor on transmission are discussed.     

Beam profile monitor for pulsed CO2-laser

Commercial beam profile monitors for pulsed CO₂ lasers (10.6 μm wavelength) are expensive and suffer from a low damage threshold. To overcome these problems, a robust detector with a high damage threshold was developed. The detector is made of a special type of graphite which is evaporated during the interaction with the laser beam. A plasma is formed which radiates visible light. Using a conventional fast shutter imaging system, this plasma light directly shows the spatial intensity distribution of the laser beam. The detector works in the power range of 10⁵-10⁷ W/cm²      

CO2-laser with vibration-proof Q-switch

A CO₂-laser with vibration-proof Q-switching is described. Modulation is achieved by spinning a plane-parallel Ge or Si plate as Fabry-Perot interferometer. A 1.4 mm thick Si interferometer makes it possible to obtain pulses with duration of about 100 ns and a power of 50 kW, which is higher than cw generation by a factor of 2000.     

Self-pulsing instability of a CH2F2-laser

A single mode self-pulsing instability is reported for the 117 μm optically pumped far infrared CH₂F₂ laser     

Upconversion from the I13/2 and I11/2 levels in Er:YAG

The efficiency of erbium three-micron laser (laser transition ⁴I_11/2→⁴I_13/2) depends essentially on the ratio of the parameters of active energy transfer upconversion (ETU) from the laser levels. The parameters of both ETU processes can be obtained from the analysis of the shape of the kinetics of the ⁴I_11/2 level in concentrated Er:YAG crystals, under short pulse pumping. Mathematical modeling is used to evaluate the sensitivity of the method and to estimate the errors which can be introduced by the inhomogeneous pumping and accidental impurities. It was found that the ratio of the parameters corresponding to the ETU from the laser levels is less sensitive to the pumping inhomogeneities than that corresponding to the lower laser level. A reduction of this ratio with increasing erbium concentration is observed.     

Reliable and efficient tea N2-laser

Employing high-quality electrodes and an optimized C-to-C excitation circuit we have developed a simple and reliable TEA N₂-laser. The efficiency is 0.07%, the highest reported to date for this type of laser.     

Absorption properties of the near infrared CO2 bands

The equivalent widths of the near i.r. CO₂ bands at 1.4, 1.6, 2.0, 2.7, 4.8 and 5.2 μm have been measured for various sample parameters. By comparing the data obtained for pure CO₂ samples with theoretical values resulting from line0by-line calculations, band intensities have been determined for these six bands. The data obtained for the mixtures of CO₂ with N₂ have been used to check the validity of the band intensities thus determined. These data have also been used to check the applicability of the empirical formulae proposed by Howard, Burch and Williams.     

Experimental investigation of a multichannel N2-laser

A multichannel UV-laser is described which provides a flexible high repetition rate pulsed light source for the generation of short duration light pulses.     

CO2-laser photoacoustic detection of gaseous n-pentylacetate

The absorption spectra of gaseous n-pentylacetate were investigated by FT IR spectroscopy as well as CO₂-laser photoacoustic spectroscopy for simulation of the dispersion of a nerve agent (sarin) within a modeled atmospheric boundary layer. Three CO₂-laser emission lines were used for photoacoustic detection of n-pentylacetate with detection limit in the range of 1-3 ppm.     

Far infrared absorption of Fe2+ in KMgF3

Far infrared absorption in cubic KMgF₃ doped with Fe²⁺ is reported . A line is observed at 87cm^?1, which is assigned to the (Γ_5g → Γ_3g, Γ_4g) transition in the Fe²⁺. The reduction in the spin-orbit coupling from the free ion value has been predicted by Ham, Schwarz and O'Brien.     

Reflectance and absorption spectra near the band gap in CuInSe2

The reflectance and absorption spectra of CuInSe₂ near the band gap were obtained at 7 K. From the analysis of the data, an estimate of the exciton binding energy, Bohr radius, and low frequency dielectric constant has been made, which are 15 meV, 5.5 nm, and 8.5 respectively.     

Investigation on nonradiative decay of I13/2→I15/2 transition of Er-doped oxide glasses

Nonradiative decay of ⁴I_13/2→⁴I_15/2 transition of Er³⁺ has been investigated in a series of oxide glasses. For Er³⁺-doped glass samples, the Judd-Ofelt analysis on absorption spectra was performed and the fluorescence lifetime was determined by extrapolating to zero Er³⁺ concentration limit. Infrared spectra were measured in order to investigate the influence of OH⁻ groups in different glasses. The effects of glass matrix on the decay rate were discussed from the viewpoint of phonon energy, variations of effective fields, and OH⁻ groups. Compared to other glasses, phosphate glass presents low quantum efficiency and large nonradiative decay rate due to its high phonon energy and hygroscopic behavior.     

SF6 ground-based infrared solar absorption measurements: long-term trend, pollution events, and a search for SF5CF3 absorption

Infrared solar spectra recorded with the Fourier transform spectrometer in the McMath solar telescope complex on Kitt Peak (31.9°N latitude, 111.6°W, altitude), southwest of Tucson, Arizona, have been analyzed to retrieve average SF₆ tropospheric mixing ratios over a two-decade time span. The analysis is based primarily on spectral fits to absorption by the intense, unresolved ν₃ band Q branch at . A best fit to measurements recorded with SF₆ near typical background concentrations yields a SF₆ increase in the average tropospheric mixing ratio from (10⁻¹² per unit volume) in March 1982 to in March 2002. The long-term increase by a factor of 3.34 over the time span is consistent with the rapid growth of surface mixing ratios measured in situ at Northern Hemisphere remote stations, though the infrared measurements show a large scatter. Average tropospheric mixing ratio enhancements above background by 2-3 orders of magnitude have been identified in spectra recorded on 5 days between November 1988 and April 1997. These spectra were individually analyzed in an attempt to detect the strongest 8- band of SF₅CF₃, a molecule recently identified with an atmospheric growth that has closely paralleled the rise in SF₆ during the past three decades. Absorption by the strongest SF₅CF₃ band was predicted to be above the noise level in the Kitt Peak spectrum with the highest average mean tropospheric SF₆ mixing ratio, assuming the reported atmospheric SF₅CF₃/SF₆ ratio and a room temperature absorption cross sections reported for the SF₅CF₃ 903-cm⁻¹ band. An upper limit of 8×10¹⁵ for the SF₅CF₃ total column was estimated for this case. We hypothesize that the highly elevated SF₆ levels above Kitt Peak resulted from a local release experiment rather than production via electrochemical fluoridation of intermediate products, the proposed source of atmospheric SF₅CF₃. The absence of the SF₅CF₃ feature in the spectra with elevated SF₆ is consistent with the absence of SF₅CF₃ reported in a pure SF₆ sample.     

Far infrared measurements of (TMTSF)2ClO4

Polarized far infrared reflectance measurements from 20 to 330 cm^?1 have been made on the organic superconductor (TMTSF)₂ClO₄. The feature in the reflectance at 28 cm^?1 has been studied as a function of temperature and applied magnetic field. Our results suggest that this feature is associated with a coupled electron-phonon mode rather than a pseudogap due to fluctuational superconductivity as has been suggested by others. In addition, a Kramers-Kronig analysis of the reflectance indicates that there is a concentration of oscillator strength above 100–150 cm^?1.     

Laser-microwave double-resonance spectroscopy in CF3I with four CO2-laser lines

Double-resonance effects produced by three CO₂-laser lines, the 9.4-μmR(12),R(14), and R(18), have been newly observed. From an analysis of the observed laser-induced changes in intensity of various microwave transitions, the infrared transitions which were accidentally coincident with these three laser lines were determined. In every case an exact rotational assignment of the infrared transition was possible, but in some cases the assignment of the vibrational band involved was difficult. When the previously discussed (l) effects produced by the R(16) laser line are included these four consecutive laser lines pump a total of seven infrared transitions of CF₃I. It appears that all seven transitions belong to different fundamental, combination, and hot bands.     

High-Q measurements of fused-silica microspheres in the near infrared

Measurements of the quality factor Q approximately 8x10(9) are reported for the whispering-gallery modes (WGM's) of quartz microspheres for the wavelengths 670, 780, and 850 nm; these results correspond to finesse f approximately 2.2x10(6) . The observed independence of Q from wavelength indicates that losses for the WGM's are dominated by a mechanism other than bulk absorption in fused silica in the near infrared. Data obtained by atomic force microscopy combined with a simple model for surface scattering suggest that Q can be limited by residual surface inhomogeneities. Absorption by absorbed water can also explain why the material limit is not reached at longer wavelengths in the near infrared.     

New CW laser lines from CO2-laser pumped CH3OD

New laser wavelenghts have been observed from CW CO₂-laser optically pumped CH₃OD.     

High-temperature infrared spectrum of HCN near 3300 cm−2

The infrared absorption of HCN near the fundamental band at 3311 cm^?1 has been measured at temperatures up to 1200 K. Transitions involving high rotational states (up to J = 62) have been measured. These give an improved value for the sextic centrifugal distortion term H₀. Many hot-band transitions have been observed and assigned to transitions originating in vibrationally excited states up to 4000 cm^?1 above the ground state. These measurements give new data on vibrational states involving moderately high bending quantum numbers and indicate that new terms are needed to fit the ro-vibrational energy levels.     

Magneto-optical study of the I2 bound exciton in ZnTe

The 1L0-phonon replica of the I₂ bound exciton in ZnTe at 2.374 eV is fully resolved into a quintet at fields of 130 kG. Analysis of the data shows that the I₂ complex consists of an exciton bound to an $\text{ionized}$ donor or acceptor; the electron and hole gyromagnetic ratios deduced, $\text{g}{}_{\mathrm{h}}\text{= ? 1.2}$ and g_e = ± 1.7, are in excellent agreement with the values determined from recent spin-flip scattering experiments, viz. g_h = 1.07 ± 0.1, g_e = 1.74 ± 0.05.     

Optically pumped continuous I2 molecular laser

Continuous laser oscillation was observed for various B ³Π_0⁺u → X ¹Σ_0⁺g transitions of molecular iodine in the wavelength range of 583.0 nm to 1338 nm excited by a single frequency 514.5 nm argon laser. For pump powers of 3W output powers up to 250 mW were obtained. Some properties of the laser system are discussed.