Frequency stabilization and measurements of 543 nm HeNe lasers

In this paper we report our investigations on the frequency stabilization and frequency measurements of 543 nm HeNe laser. It contains following four different works. (1) Using a metal laser tube we have built an iodine-stabilized 543 nm HeNe laser by the Frequency-Modulation (FM) spectroscopy. The signal-to-noise ratio of the hyperfine spectrum reached 2 × 10^–12 at 1 s sampling time. (2) We have built a compact iodine-stabilized 543 nm HeNe laser system using the third-harmonic locking technique. Stability better than 1 × 10^–12 for sampling time >1 s is obtained. We also suggest the b₁₀ line for the future recommendation. (3) We constructed the Lamb-dip stabilized He-²⁰Ne and He-²²Ne lasers and measured their frequency stability, reproducibility, and absolute frequencies. The results suggest that the Lamb-dip stabilized lasers are appropriate for secondary wavelength standards. We have also deduced the isotope shift of Ne atom at 543 nm. (4) We have developed two two-mode stabilized 543 nm HeNe lasers using the bang-bang control method. The Allan variance is 1 × 10^–11 at 1 s sampling time.     

A simple fibre Fabry-Pérot sensor

A simple fibre Fabry-Pérot sensor is described in which the uncoated cleaved ends of a lenght of single mode fibre are employed as the mirror surfaces to produce high visibility near perfect cosine-squared fringes in the back-reflected light. The experimentally observed signal-to-noise performance of the interferometer illuminated by a HeNe gas laser and a semiconductor diode laser is reported. In an accelerometer configuration the device displayed a below resonance sensitivity of ≥200 rad g^-1.     

Electroluminescence at p-n junctions in ZnSe

Electroluminescent radiation at p-n junctions and the photovoltaic effect in ZnSe monocrystals were investigated. The p-n junctions were prepared by melting dots of indium on p-type ZnSe (ZnSe contained Cu impurities).The measurements were made at room temperature and at –150°C. The acceptor level depths estimated from a maximum emission are in accordance with the data in the literature.The decay time of electroluminescence measured at –150°C is 2·1×10^–6 sec. In sunlight a photovoltage of about 1·1 V was observed.I wish to thank Prof. Dr A. Jablonski for his interest in this problem.     

Formation of zirconium dioxide in molybdenum alloy tsm-6

The formation of zirconium dioxide was observed during annealing of deformed molybdenum alloy TsM-6. Particles of ZrO₂ are formed in former subboundaries, grain boundaries, and within the grains. The size, shape, and distribution of particles at different depths after annealing at different temperatures were determined. The crystallographic orientation of ZrO₂ particles in relation to the matrix was determined. The results indicate penetration of oxygen into the alloy during annealing (in vacuum of 1 · 10^–4 to 7 · 10^–5 mm Hg) through enrichment of the subboundaries in oxygen and internal oxidation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 107–112, August, 1973.Our thanks to A. D. Korotaev, on whose initiative this work was undertaken.     

Visible photoluminescence of co-sputtered Ge–Si duplex nanocrystals

The photoluminescence (PL) characteristics of co-sputtered Ge–Si duplex nanocrystal films were examined under excitation by a 325-nm HeCd laser, combined with Raman and Fourier-transform infrared reflection spectra analysis. A broad visible PL spectrum from the as-deposited Ge–Si nanocrystal films was observed in the wavelength range 350–700 nm. Basically, the PL spectrum can be considered to consist of two distinct parts originating from different emission mechanisms: (i) the spectrum in the range 350–520 nm, consisting of characteristic double peaks at 410 and 440 nm with PL intensities decreasing after vacuum annealing, probably due to vacancy defects in Si nanocrystals; and (ii) the spectrum in the range 520–700 nm, consisting of a characteristic peak at 550 nm with a PL intensity not affected by vacuum annealing, probably due to Ge-related interfacial defects. No size dependence of PL peak energy expected from quantum confinement effects was observed in the wavelength range investigated. However, with an increase of crystal size, the PL peak intensity in the blue zone decreased. The PL intensity is found to be strongly affected by silicon concentration. A film heated in air has a different PL mechanism from the as-deposited and vacuum-annealed films. PACS 78.67.Bf; 81.05.Cy; 81.15.Cd     

Dynamic moiré patterns produced by sinusoidal gratings superposition in the Bi12 TiO20 crystal

In the present note a real-time holographic moire-like pattern is shown. It is produced by the superposition of two rotated sinusoidal phase gratings and the result represents a promising technique for possible metrological applications. The experiments were performed in a diffusion-only recording mechanism in a photorefractive Bi₁₂TiO₂₀ crystal illuminated by λ = 0.633 μm from a HeNe laser light source.     

Collisional excitation X-ray laser experiments in plasmas produced by 0.53-μm and 0.35-μm laser light

Recent Ne- and Ni-like X-ray laser experiments carried out at the Centre d'Etudes de Limeil-Valenton (CEL-V) are reviewed. A variety of experiments in Ne-like X-ray lasers were performed; here we discuss measurements of soft X-ray amplification in Ge (Z=32) and Sr (Z=38) plasmas. In Ge plasmas produced by 0.53-m laser light at an irradiance of 6.0×10¹³ W/cm², gains between 2.2–2.5 cm^–1 on the 232.2 and 236.2 Å J=2–1 lines and a gain of 1.0 cm^–1 on the 196.1 Å J=0–1 line were measured. In addition, gains of 4.4 cm^–1 and 4.0 cm^–1 have been demonstrated on the J=2–1 transitions at 164.1 and 166.5 Å in Nelike Sr at laser intensities of 1.3×10¹⁴ W/cm². The effects of pumping the Ne-like Se X-ray laser with 0.35-m laser light have also been investigated; the Se lasing spectra is similar to that obtained with 0.53-m light. Experiments have also been carried out to optimize the gain of the 50.3 Å Ni-like Yb (Z=70) J=0–1 line. For Yb, no significant increase in gain over that previously reported was seen, but the time history of the Ni-like Yb X-ray laser was measured for the first time. Finally, attempts to extrapolate the Ni-like results to shorter wavelength were made using Ta (Z=73), W (Z=74), and Re (Z=75). No definitive observation of the Ni-like J=0–1 lasing lines was made in these experiments.     

Femtosecond pump and probe measurement of all-optical modulation based on intersubband transition in n-doped quantum wells

An all-optical modulation of interband-resonant light (near-infrared signal light: 800 nm) by intersubband-resonant light (mid-infrared control light: 4–7 μm) in n-doped AlGaAs/GaAs multiple quantum wells is investigated by two-color femtosecond pump–probe experiments at room temperature. The modulation of the near-infrared signal light with an ultrafast recovery as short as 1 ps is successfully observed when the quantum wells are pumped by the mid-infrared control light pulse (4 fJ/μm²). The dependence of the modulation depth on the wavelength of the control light is also measured, which is shown to be consistent with the intersubband absorption spectrum of the quantum wells. The results indicate that the utilization of the intersubband transition is promising for the ultrafast all-optical modulation and switching.     

Optoelectronic array interconnections

Two-dimensional parallel optoelectronic links are proposed for interconnections between electronic boards. Experiments were performed with LED-arrays and laserdiodes as the light transmitter, multimode fibre-arrays and imaging systems for light guiding and a CMOS opto-ASIC as highly sensitive light-receiver (detection limit is 1 fJ bit^–1 at a bit error rate of less than 10^–9). In the experiment each channel has a data rate of 10 Mbits^–1, the system is designed for 128 parallel channels occupying an area of less than 1 cm² and thus providing an overall throughput of more than 1 Gbits^–1. The applications are connections between CPUs and shared memories within a multiprocessor system.     

Absorption spectra of benzophenone derivatives containing donor groups

The absorption spectra of benzophenone derivatives with donor groups have been examined and measured in alcohol and benzene at concentrations of 10^–2210^–5 and 10^–3–10^–5 mole/l respectively. The characteristics of the spectra are explained by the participation in the light absorption of conformations, in which either one or both of the rings are noncoplanar, relative to the plane of the carbonyl.     

Eu-doped glass materials for red luminescence

Red luminescence (at wavelength about 622 nm) from Eu³⁺ ions embedded in PbO–Bi₂O₃–Ga₂O₃–BaO glass hosts is reported for room and liquid helium temperatures. The substantial influence of energy transfer processes between the host and Eu³⁺ ions is shown experimentally through the dependences of photoluminescence on light polarization and excitation wavelength. Only polarized, excited pulsed XeII laser light (λ=714 nm) gives substantial luminescence with efficiency up to 14.3%. The role of phonon-relaxation subsystem in the observed luminescence is discussed.     

Radical-Recombination Luminescence of the Uranyl Nitrate Complex in the Adsorbed State

We have investigated the luminescence of uranyl nitrate molecules on the surface of powdery SiO₂ upon excitation by UV light (PhL) and hydrogen atoms (radical-recombination luminescence (RRL)). It has been found that the PhL and RRL spectra have a clearly defined vibrational structure. The luminescence peaks of the adsorbed UO₂ ^2– ion are characterized by a systematic longwave shift from the same peaks of crystalline uranyl nitrate (by 230–430 cm^–1 at 130 K). Moreover, in the adsorption centers the vibration frequencies of UO₂ ^2– are 20–80 cm smaller than in crystalline salt and the RRL bands are 150–350 cm^–1 (130 K) wider than the corresponding PhL bands.     

The ellipticity introduced by interferential mirrors on a linearly polarized light beam orthogonally reflected

Modifications of the state of polarization of a light beam trapped in a multipass cavity formed by interferential mirrors were studied. It was found that the mirrors analysed introduced ellipticities ranging from 3×10^–5 to 2×10^–4 per reflection.     

Harmonic and sum-frequency generation of pulsed laser radiation in BBO,LBO, and KD*P

The optical properties of the nonlinear crystals lithium borate (LBO), barium borate (BBO) and deuterated potassium phosphate (KD*P) are compared for second and third harmonic generation of Nd:YAG laser radiation. In an experimental investigation the conversion efficiency has been measured as a function of the energy density of 8 ns long laser pulses, generated by a commercial Nd:YAG oscillator-amplifier system. In LBO and BBO the second harmonic generation saturates at an energy density of about 1.5 J cm^–2 at efficiencies of 55–60%. In KD*P comparable efficiencies (40–55%) require energy densities of 2–2.6 J cm^–2. Similar results are obtained for frequency tripling. In LBO and BBO saturated efficiencies of 20–25% are measured at an energy density of about 1.5 J cm^–2. In KD*P efficiencies of 20% are obtained at energy densities exceeding 2 J cm^–2. Besides for doubling and tripling of Nd:YAG laser radiation the phase-matching is calculated for frequency conversion of tunable laser light. The results demonstrate that in LBO and BBO phase-matched sum-frequency mixing of UV and infrared laser light generates tunable radiation at wavelengths as short as the transmission cut-off at 160 nm and 190 nm, respectively.     

Effect of dimensional and magnetic quantization hybridization in the optical absorption spectra of nanoheterosystems with <Emphasis Type="Italic">D</Emphasis><Superscript>(−)</Superscript>-states

The magnetoabsorption of light by quantum dot — D^(–)-center complexes synthesized in a transparent dielectric matrix — is theoretically studied with allowance for dispersed quantum dot (QD) sizes. In the effective mass approximation, an analytical expression for the impurity magnetoabsorption coefficient of light polarized in the quantizing magnetic polarization field direction is derived.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 67–72, October, 2004.     

Light Source with a Thermoionic Cathode

A light source with a thermoionic cathode has been investigated in helium at atmospheric pressure; the spectral radiance of the light source in the range 200–800 nm and the cathode temperature (3510 K) have been determined. Its employment as a light source in absorption spectroscopy for determination of the concentration of triplet and singlet metastable helium atoms in an atmospheric-pressure glow discharge has been demonstrated. The total concentration of metastable atoms was 3.5·10¹³ cm^–3.     

Resonant elastic scattering of light from single quantum wells in semiconductor multilayers

A theory is developed for steady-state elastic scattering of light via quasi-2D excitons from a quantum well (QW) whose interfaces are randomly rough. The study is mainly focused on the angle dependences of radiation giving direct information about static disorder responsible for the elastic scattering. A nonlocal excitonic susceptibility is expressed in terms of random profile functions of QW interfaces. Treated is elastic scattering of light from a disordered QW in the following actual dielectric environments: (i) a uniform background, (ii) a Fabry–Perot film with rough boundaries, and (iii) a semiconductor microcavity. The cross-sections are derived analytically for scattering of linearly polarized light to the lowest (Born's) approximation with arbitrary roughness statistics. The spectral and angle dependencies of scattering intensity are analyzed numerically in the absolute-value scale with Gaussian correlation of interface roughness. The probability 10⁻² was found for the exciton-mediated scattering of a photon from a QW interface roughness whose root-mean-square height is on the level of 2×10⁻¹ nm. This probability is shown to exceed by two orders of magnitude that is typical of resonant scattering from either a single semiconductor surface or rough boundaries of a semiconductor Fabry–Perot film containing the QW. The scattering spectrum of a QW placed in a microcavity is predicted to have a doublet structure whose components are associated with the cavity exciton–polaritons.     

PbO–Bi2O3–Ga2O3–BaO glasses doped by Er as novel materials for IR emission

Infra-red luminescence (at wavelengths about 1600 and 2500 nm) from Er³⁺ ions embedded in PbO–Bi₂O₃–Ga₂O₃–BaO glass hosts is reported for room and helium liquid temperatures. The substantial influence of energy transfer processes between the host and Er³⁺ ions is shown experimentally through the dependences of photoluminescence on light polarization and excitation wavelength. Only the application of the polarized pumping YAG–Nd laser beam (λ=1060 nm) stimulates substantial luminescence with quantum efficiency up to 24%. The role of phonon-relaxation subsystem in the observed luminescence is discussed.     

Picosecond pulse generation in a benzene raman generator amplifier system

Picosecond ruby laser pulses generate simultaneously Stokes pulses of the 992 cm^–1 ring breathing mode and of the 3063 cm^–1 CH-stretching mode of benzene in a Raman generator cell by stimulated Raman scattering under self-focusing conditions. The Raman generator light is spectrally filtered, collimated, and amplified in three Raman amplifier cells pumped by ruby laser pulses. Both first Stokes lines have been selectively amplified to short, low divergence, intense light pulses.     

Drift mobility and kinetics of transport of excess charge carriers in glassy CdGexAs2

Conclusions We tried to measure transient conductivity response to pulse strongly absorbed excitation (light, accelerated electrons) in sandwich type samples of glassy CdGe _x As₂ compounds. We observed the signal due to transport of free excess carriers. From analysis of experimental results we conclude that in our materials strong trapping effects are present, so the range of excited carriers is very short (10^–4-10^–3 cm) even in the highest electrical fields used (to 10⁴ V. cm^–1). Estimates of upper limit of drift mobility give the values 10^–1- 1 cm² V^–1 sec^–1. We did not succeed in determining the type of carriers which are responsible for the observed effects.