The temperature dependence of the spectral width of singlet oxygen dimole emission

In the temperature range of T = 150–400 K, the dependence of spectral widths (cm⁻¹) on temperature, 182 + 0.38(±0.01)T and 217 + 0.48(±0.01)T, respectively, has been obtained for dimole emission of O₂(a, 0) + O₂(a, 0) → O₂(X, 1) + O₂(X, 0) + hν (λ = 703 nm) and O₂(a, 0) + O₂(a, 0) → O₂(X, 0) + O₂(X, 0) + hν (λ = 634 nm). It was shown that the ratio of dimole emission rate constants does not depend on temperature in the range of 150–400 K and is 1.06 ± 0.01.     

Calculation of the quenching rate constants for electronically excited singlet molecular nitrogen

The quenching rate constants for the singlet states (a′)⁽¹⁾Σ _u ⁻ (v = 1−17), a ⁽¹⁾Π _g (v = 0−14), and w ⁽¹⁾Δ _u (v = 0−13) of molecular nitrogen colliding with an N₂ molecule are calculated using quantum-chemical approximations. It is shown for the first time that both the intramolecular and intermolecular processes of electronic excitation transfer are significant for these states. Calculated rate constants are in satisfactory agreement with experimental data.     

A diode laser spectrometer at 634nm and absolute frequency measurements using optical frequency comb

This paper reports that two identical external-cavity-diode-laser (ECDL) based spectrometers are constructed at 634 nm referencing on the hyperfine B-X transition R(80)8-4 of ¹²⁷I₂. The lasers are stabilized on the Doppler-free absorption signals using the third-harmonic detection technique. The instability of the stabilized laser is measured to be 2.8×10^-12 (after 1000 s) by counting the beat note between the two lasers. The absolute optical frequency of the transition is, for the first time, determined to be 472851936189.5 kHz by using an optical frequency comb referenced on the microwave caesium atomic clock. The uncertainty of the measurement is less than 4.9 kHz.     

Investigation of atmospheric emission and attenuation at wavelengths 2.07 and 3.34 mm

The results of processing the data of an annual cycle of synchronous measurements of the Earth's atmosphere emission in two transparency windows are reported.     

同时辐射六种可见波长的CW-氦氖激光器的稳频及其输出的650nmCW氦氖受激Raman辐射

在中国计量科学研究院研制的612激光管上,利用反射率为99.95%宽带激光反射镜,得到同时辐射六种波长的连续振荡,其波长为:611.8,629.8,632.8,635.1,640.1和650um,测量了它们的物理参数,验证了650nm为氦氖Raman激光.对六种波长在简易装置上进行了稳频,各条激光谱线的频率稳定性优于10~(-10),利用锁模技术,各条激光谱线的频率稳定性可达10~(-12).     

Tantalum irradiation by high power pulsed laser at 1315 and 438 nm wavelengths

The high power pulsed laser Prague asterix laser system (PALS), operating at the fundamental (1ω) and third (3ω) harmonics (1315 and 438 nm wavelengths, respectively), is employed in a single-shot mode to irradiate tantalum targets in vacuum. The laser pulse width is 400 ps and the laser pulse energy ranges between 43 and 736 J at 1ω and between 12 and 230 J at 3ω. High ablation yields (0.1–0.6 mg per pulse) are measured as a function of the laser pulse energy at both wavelengths; at 438 nm higher etching rates are observed. The produced craters are analysed by the scanning electron microscope (SEM) and by the high sensitivity surface profiler system. They are investigated in dimension, shape and angle aperture as a function of the incident laser energy. Different possible mechanisms responsible for the different crater shapes are presented and discussed.     

LD side-pumped Nd:GGG CW laser operating at 1110 and 1105 nm dual wavelengths and 1110 nm single wavelength

A diode-side-pumped continuous-wave Nd:GGG laser operating at dual-wavelength (1110 and 1105 nm) and single wavelength of 1110 nm is demonstrated for the first time. The maximum output power of the 1110 and 1105 nm dual-wavelength operation is 13.2 W. By adjusting the orientation of an insertion mirror, the relative intensities of the two wavelengths can be changed. Thus single wavelength operation at 1110 nm is obtained, and the output power is 9.6 W.     

1064 nm Nd:YVO4 laser intracavity pumped at 912 nm and sum-frequency mixing for an emission at 491 nm

We present for the first time a Nd:YVO(4) laser emitting at 1064 nm intracavity pumped at 912 nm by a Nd:GdVO(4) laser. We carried out a model to design the system properly, and laser performance was experimentally investigated. Intracavity sum-frequency mixing at 912 and 1064 nm was then realized in a BiBO crystal to reach the blue range. We obtained a cw output power of 155 mW at 491 nm with a pump laser diode emitting 20 W at 808 nm.     

Two-beam coupling of a series of reduced BaTiO3:Rh at wavelengths of 514 nm and 633 nm

Dedicated to Prof. Dr. Eckard Kr?tzig on the occasion of his 60th birthday.Five annealed BaTiO₃:Rh crystals, including as-grown and those reduced at 10^-5 atm, 10^-10 atm, 10^-12 atm, and 10^-14 atm oxygen partial pressures, were produced and investigated by two-beam coupling at wavelengths of 514 nm and 633 nm. The carrier type is a function of reduction degree and incident wavelength. The compensation points are around 10^-3 atm and 10^-11 atm oxygen partial pressures for 514 nm and 633 nm, respectively. The electrooptic gain is controlled by the photoconductivity–dark conductivity ratio, effects from the deep and shallow traps, and hole–electron competition, which are dependent on the reduction degree and incident wavelength. Received: 23 November 1998 / Revised version: 10 February 1999 / Published online: 12 April 1999     

Observation of self-amplified spontaneous emission and exponential growth at 530 nm

Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator.     

Dual-wavelength Nd:YAP laser at 930 and 1341 nm and sum-frequency mixing for an emission at 549 nm

A dual-wavelength continuous-wave (CW) diode end-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser that generates simultaneous laser action at the wavelengths 930 and 1341 nm is demonstrated. A total output power of 778 mW for the dual-wavelength was achieved at the incident pump power of 17.8 W. Furthermore, intracavity sum-frequency mixing at 930 and 1341 nm was then realized in a LBO crystal to reach the yellow-green range. We obtained a total CW output power of 103 mW at 549 nm.     

The 352 nm emission spectrum of difluorodiazirine

Difluorodiazirine fluoresces strongly in the vapor phase showing an extensive band system from about 352 to 451 nm and with no background continuum. The fluorescence is assigned as $\text{A}\text{?}{}^1\text{B}{}_1\text{(nπ}{}^1\text{)-}\text{X}\text{?}{}^1\text{A}{}_1$ and corresponds to the 352 nm absorption system previously studied.The band system is dominated by a progression in ν₁″, the a₁N = N stretching vibration, with ν₄″, the a₁ CF₂ symmetrical deformation vibration, showing a shorter progression.The 0₀⁰ and most others show type B rotational contours but type C bands, involving ν₅″ (a₂), and probably type A bands, involving ν₇″ (b₁) and perhaps ν₆″ (b₁) are also observed.The extremely low intensity of bands involving ν₃″ (a₁) is surprising but there seems to be no reason to doubt the assignment from infrared and Raman data.There is a strong vibrational perturbation affecting some quite strong bands in a region within about 275 cm^?1 of bands 1_n⁰4₀⁰, where n = 0 – 3. The cause of the perturbation is not known.There is no evidence for the emission spectrum consisting of more than one band system.     

Electrical and optical characteristics of GaN-based light-emitting diodes fabricated with emission wavelengths of 429-467 nm

The electrical and optical characteristics of GaN-based light-emitting diodes (LEDs) fabricated with emission wavelengths of 429-467 nm were investigated. The optical output increased with increasing emission wavelength, which is attributed to the enhanced quantum confinement effect as a result of indium composition fluctuation. With higher indium content, the LEDs exhibited unfavorable performance, including a larger efficiency droop, spectral blueshift, and spectral broadening, due to indium-induced strains. The effect of heterointerfaces associated with the indium content of the active region on the device resistance was negligible.     

Determination of the rate constant of oxygen quenching of the excited states of molecules from the singlet oxygen luminescence

We have pioneered a method of determining the rate constant of quenching of the excited electronic states of molecules by molecular oxygen from measurements of the kinetics of photosensitized luminescence of singlet molecular oxygen (^lδ_g). The method can be used in the case where the lifetime of the excited electronic state in an air-saturated solution is comparable with or larger than the luminescence time of the singlet molecular oxygen in the given solvent. It is shown that this situation is implemented on quenching, by molecular oxygen, of the excited triplet states associated with the biopolymers of tetrapyrrole molecules in aqueous (H₂O and D₂O) solutions. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 401–404, May–June, 2000.     

Power absorption coefficient constants for water, acetonitrile, and methylene chloride at far infrared wavelengths

The problem of multiple internal reflections within the windows of an optical cell is analysed using Abele's matrix method. The Beer-Lambert power law is modified by the standing waves formed in between the cell and the detector. Power absorption coefficient of a material is calculated by a fit to the modified version of the equation. Precise values for water, acetonitrile and methylene chloride are calculated at far infrared wavelengths using a molecular laser source.     

Bulk optical parameters of porcine skin dermis at eight wavelengths from 325 to 1557 nm

We introduce a method with which to obtain accurately the bulk optical parameters of fresh biological tissues in vitro by combining measurements of the sample surface profiles, reflectance, and transmittances with Monte Carlo-based inverse calculations. The bulk optical parameters of fresh porcine dermis tissue were determined at eight wavelengths from 325 to 1557 nm and were found to be much different from those determined without consideration of surface roughness.     

The effect of frozen soil layer thickness on thermal emission at the wavelengths 3.6–11 cm

The results of experimental investigation of temporal dynamics of radiobrightness temperature at the wavelengths 3.6, 5, and 11 cm in the course of frost penetration and thawing are presented for the soils with different humus content. Using the method of simulating emission from a horizontally stratified medium, it is shown that radiobrightness temperature variation is related to changes in the frozen soil layer thickness. It is noted that that dielectric permittivity of the frozen layer at the temperatures around 0 °C is controlled by non-frozen bound water, whose content depends on the soil type. It is also underlined that in certain cases proper interpretation of the experimental data requires inclusion of the soil moisture motion towards the cold front into consideration. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 5–10, September, 2006.