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In the present study, we report the preparation of ZnO nanoparticles and their linear and nonlinear optical (NLO) properties. The ZnO nanoparticles are prepared by chemical route method. The linear optical studies such as UV-Vis absorption and photoluminescence show the strong absorption at 333 nm and emission at 450 nm, respectively. The direct ban near optical (NLO) properties are investigated using Z-scan technique under DPSS CW laser at 532 nm wavelength. Mean time strong nonlinear absorption and negative nonlinear refractions are observed. The third order nonlinear optical coefficients and the magnitude of the susceptibility are determined. The optical limiting behavior of the nanoparticles is observed and the limiting threshold is calculated. The above results show that the prepared ZnO nanoparticles are suitable for nonlinear optical and optoelectronic applications.

To increase the efficiency of laser-driven ion acceleration, a method for in-situ target cleaning by heating action of the continuous wave (CW) laser was developed. On a 20 TW picosecond laser facility, experiments on ion acceleration from heated Ti and Ta targets of 1 μm thickness were conducted. CW laser cleaning allowed an increase in carbon and oxygen ion energies by 2.5 times up to 65 MeV. Ta ions with energies of up to 47 MeV were registered in experiments. Their linear energy transfer exceeds 35 MeV·cm2/mg, thus making these particles suitable for the investigation of single event effects in microelectronic devices induced by protons from solar flares.To increase the efficiency of laser-driven ion acceleration, a method for in-situ target cleaning by heating action of the continuous wave (CW) laser was developed. On a 20 TW picosecond laser facility, experiments on ion acceleration from heated Ti and Ta targets of 1 μm thickness were conducted. CW laser cleaning allowed an increase in carbon and oxygen ion energies by 2.5 times up to 65 MeV. Ta ions with energies of up to 47 MeV were registered in experiments. Their linear energy transfer exceeds 35 MeV·cm2/mg, thus making these particles suitable for the investigation of single event effects in microelectronic devices induced by protons from solar flares.

An optical-optical double resonance sub-Doppler experiment is used to measure short nonradiative lifetimes in the C 1Σ+ state of LiH. These lifetimes are expected to result from the strong electronic interaction between the C 1Σ+ state and the continuum of the A 1Σ+ state and to vary with the vibrational quantum number, from nanoseconds to milliseconds [F. Gemperle and F. X. Gadea, J. Chem. Phys. 110, 11197 (1999)]. The experimental setup combines a molecular beam of LiH, a first cw laser beam locked to a given A-X absorption line, and a second cw laser beam scanned over C-A absorption profiles. Analysis of these absorption profiles in terms of Voigt profiles shows that their Lorentzian components significantly vary with the vibrational quantum numbers of the C state. Nonradiative decay rates deduced this way are systematically larger than the calculated ones but their variations are similar. Coherent saturation effects cannot be invoked to explain this discrepancy.

An optically induced convection during IR laser interaction with water or any absorbing liquid is described theoretically. The numerical simulations performed using the developed model show that the optical pressure and ponderomotive forces produce water flow in the direction of the laser beam propagation. In the later stage of interaction, when the water temperature rises, the Archimedes force becomes comparable and, ultimately, dominant, producing convection directed against the vector of gravitational acceleration (upward). The theoretical estimates and numerical simulations predict fluid dynamics similar to what is observed in previous experiments.

We have demonstrated efficient all-optical polarization conversion of cw 1.55 μm laser in nematic liquid crystal films. The process is mediated by coherent two-beam coupling effect between an incident polarized laser and its orthogonally polarized noise component scattered by the director axis fluctuations. We report here a quantitative theory that accounts for severe pump depletion and high-efficiency polarization conversion and demonstrate good agreement with experimental observations.

The effects of pump polarization on the performance of cw dye lasers have been investigated. A recently developed semiclassical model for synchronously pumped mode‐locked dye lasers is adapted to the problem of cw dye‐laser oscillation, and analytic expressions are obtained for the relationship between the pump power, pump polarization, and dye‐laser output power. The theoretical results are compared with experimental data obtained using an argon‐laser‐pumped rhodamine 6G dye laser.

We have developed a KCl:Li (F+2)A color center laser which produces more than 1.2 W of cw laser power, over a factor of 3 greater than the highest power previously reported. This paper contains the results of this study, and presents guidelines for preparing laser crystals to routinely and reproducibly generate these high powers.

We report device results from channel guide InGaAs‐GaAs strained quantum well lasers with In0.49Ga0.51P cladding layers (λL = 980 nm). Channel guide lasers are demonstrated with a new current blocking scheme using a p‐n‐p InGaP junction on a p+‐GaAs substrate. The laser structure is grown by metalorganic vapor phase epitaxy on the channeled n‐InGaP layer. The reverse biased p‐n‐p InGaP junction is shown to be effective in preserving the current blocking properties for InGaAs‐GaAs‐InGaP lasers. The uncoated lasers show cw laser thresholds of 11 mA at RT and high output powers of 125 mW.

A vapor bubble is created by a weakly focused continuous-wave (CW) laser beam on the surface of a silver film. The temporal dynamics of the bubble is experimentally investigated with a tuned incident laser. The expansion and contraction rates of the vapor bubble are determined by the laser power. The diameter of the vapor bubble can be well controlled through tuning the laser power. A theory model is given to explain the underlying physics in the process. The method reported will have some interesting applications in micro-fluidics and bio-techniques.

An experimental study on a sustained optical discharge in argon was made. The discharge was initiated by using the high‐power radiation from a pulsed CO2 laser and was maintained by using the 10.6‐μ radiation from a low‐power cw laser. An extensive pressure range, where the discharge can be maintained indefinitely, is found to exist. The discharge exhibits four distinct characteristics in the pressure range 2–17 atm. It is also found that the minimum cw power required to maintain the discharge is several orders of magnitude smaller than the power to initiate it and has a p−2 dependence on the gas pressure at low pressures. This dependence came from the ambipolar diffusion losses. An electron production and loss rate balance equation is found to adequately describe this minimum maintenance power dependence on the gas pressure.

CsH produced by an electrical discharge in a Cs+H2 mixture is photoexcited to a A 1∑+ (v′, J′) state, either by a cw laser or a pulsed laser. We measure the ratios ρP,R of transition probabilities corresponding to the fluorescence lines A 1∑+ (v′=6, 1≤J′≤18)→X1∑+ (v″=1 and 2, J″) for the P and R branches. ρP,R is observed to vary slowly with J′. We determine also the radiative lifetime τr of A 1∑+ (v′=6, 7, 12, 15, 19) states; τr exhibits a strong decrease (90 to 35 ns) when v′ varies from 7 to 12. These experimental findings will be compared in the following paper (part II) with theoretical predictions.

InxGa1−xAs (x ∼0.23) p‐n junction lasers have been prepared which are capable of providing continuous‐wave (cw) operation at 1.085 μm at 77°K, and which emit 64 mW of coherent radiation at a current level of 1 A. Twelve‐element series‐connected laser arrays of InxGa1−xAs also have been fabricated, which emit more than 21 W of (peak) 1.058‐μm radiation at 77°K when driven at a (pulse) current level of 8 A.

A simple apparatus for the accurate measurement of the angular dependence of the reflectance, absorbtance, and transmittance of objects illuminated by a cw laser is described. Beam profiles and divergences can also rapidly be determined.

We present the results of a detailed experimental study of the self‐focusing of a low intensity cw laser in its passage through a nematic liquid‐crystal film. The results are in quantitative agreement with our theory of optically induced birefringence as a function of geometry, thickness, and intensity. We have also quantitatively measured the relative contribution from thermal lensing effect.

A complete rotational analysis of the E 2Σ–B 2Σ system of CaCl has been accomplished using two tunable dye lasers. The first cw laser is tuned to a known B 2Σ–X 2Σ transition to produce a finite concentration of molecules in a particular quantum state. Subsequently, a second pulsed dye laser is used to record the E 2Σ–B 2Σ excitation spectrum from this state prepared level. The method vastly simplifies an otherwise congested molecular spectrum. The data are combined with previous microwave measurements on the X 2Σ state and optical data on the B 2Σ–X 2Σ system to give the following molecular constants (cm−1). Uncertainties are 95% confidence limits in the last digit.

Si samples implanted with As+ have been annealed with a modified commercial scanning electron microscope and with a scanning cw Ar+ laser. A comparison of these two techniques is presented, using electron‐beam‐induced current as a probe of minority‐carrier effects. With a minimum of parameter optimization, it is found that electron‐beam annealing is usually superior to laser annealing with respect to both lateral and vertical uniformity.

Up to 6 W of cw laser power has been extracted from vibrationally excited CO produced in free‐burning CS2/O2/N2O flames burned at pressures of 10–40 Torr. A peak efficiency of approximately one laser photon for every eight fuel molecules has been obtained.

We have observed 22 new laser transitions in singly ionized selenium, ranging in wave‐length from 4467 A to 1. 26 μ. Output powers varying from 3 to 50 mW have been measured over the entire spectral range of operation in a 2‐m discharge tube. This same tube produces a combined output power of 250 mW on the six strongest blue‐green transitions. We have also studied the current saturation behavior of the laser and the effects of isotope structure on the laser output.

We have observed 31 cw laser transitions in the spectrum of singly ionized Te II, ranging in wavelength from 4843 to 9378 A. 16 transitions were observed with He as a buffer gas, and 20 transitions were observed with Ne (5 were common to both gases). The experimental evidence indicates that charge transfer is the dominant excitation mechanism for both gases.

Continuous‐wave laser operation at 10.6μ has been achieved in the DF–CO2 and HF–CO2 molecular systems by purely chemical means. No external energy sources are required; both lasers operate solely by the simple mixing of bottled gases. Experimental results are presented which demonstrate that cw chemical laser operation at high power and high efficiency is realizable in the DF–CO2 system.

cw laser action has been observed at 24 wavelengths in the visible spectrum of Se II in a He–Se discharge. The wavelengths range from 4604 to 6535 A. A power output of 30 mW was measured on six lines oscillating simultaneously. We obtained as many as 13 wavelengths lasing at the same time in a cavity with broad‐band high‐reflectivity mirrors.

We report the results of measurements of the first‐order Raman spectrum of Si under conditions of large temperature inhomogeneities generated by a critically focused cw laser beam. We find that the Stokes and anti‐Stokes bands are extensively deformed due to large asymmetric broadenings which develop on the side of the low‐frequency shifts. The broadenings are thus attributed to temperature gradients and are shown to be important in determining temperature distributions.

cw laser action in an optically pumped Li‐doped KCl crystal containing FA (II) centers has been demonstrated. The laser wavelength was continuously tunable over the range 2.6–2.8 μm. Pump power at threshold was 50 mW, and threshold powers in the submilliwatt range can be predicted for an improved cavity design. Laser action was obtained for crystal temperatures in the range 77≲ T ≲ 200 °K.

The possibility of mode locking of high‐powered laser oscillators by injection locking to a weak mode‐locked signal from a cw laser is proposed and demonstrated. The experiment was carried out using a flash‐lamp–pumped pulsed dye laser injection locked to a mode‐locked cw dye laser. Gains on the order of 3×104 and nearly Fourier‐transform–limited mode‐locked pulses were obtained.

Several new luminescence transitions are found in cw laser‐annealed silicon. We report the spectra, temperature dependences, and thermal‐annealing effects. At least two defects are shown to be present, and their possible identity is discussed.

We have observed optical bistability in a Fabry‐Perot cavity with a nematic liquid crystal film. Switching phenomenon was observed with a low power single‐mode cw laser of about 300 mW.

The enhancement of cw laser melt‐through of solids resulting from melt removal produced by a blowoff impulse generated by short superimposed laser pulses is investigated. A simple model is used to develop an expression for the minimum impulse criteria.

cw laser emission has been obtained from vibrationally excited HF produced by the reaction of F with C3H8 and C4H10. F atoms are obtained by combusting F2 and D2, diluted with He, with F2 in excess. The combustor products are mixed with C3H8 or C4H10 using parallel flow (pressure matched) produced by supersonic nozzles for both the F, F2, DF, and He combustor product mixture and C3H8 and C4H10.

Infrared‐microwave pumping of two‐photon transitions in NH3 has led to cw laser emission of a number of NH3 transitions in the far infrared.

It is shown by transmission electron microscopy (TEM) investigation that the dark line defect (DLD) structure induced by optical pumping of undoped Ga1−xAlxAs–GaAs double‐heterostructure (DH) laser material is identical to the DLD's which develop during laser diode operation of devices fabricated from similar p‐n structure material. This confirms the DLD generation, and subsequent failure of cw laser diodes can be a growth‐related property of Ga1−xAlxAs–GaAs DH laser material and is not necessarily associated with p‐n junction dopants or contact metallization technology.

Several factors not previously associated with cw laser degradation are shown to influence the life and reliability of (AlGa)As cw injection laser diodes. They include zinc diffusion, sawing damage, and facet erosion. When proper attention is paid to these factors, lasers showing no significant degradation for at least 2000 h can be made.

Experiments have been carried out to check the validity of calculated temperature distributions in cw‐laser‐irradiated silicon on sapphire. Both implanted and unimplanted samples were investigated. The implantations did not significantly change the temperature induced by the laser beam. At low laser scan velocities the agreement between the experiments and the calculations is good, but at high scan velocities the existing theoretical expressions are shown to be inadequate. Some of the problems involved in applying the calculations to an experimental situation are discussed.

A simple model is presented that describes the enhancement of cw laser melt‐through of opaque solids due to gravitationally induced melt removal. It is shown that a stationary target whose front surface is oriented at an angle from the horizontal may experience significant reduction in melt‐through time due to laminar flow of molten material. As a direct consequence of the high viscosity of the melt, the rate of melt removal is related to the cube of the melt thickness. This model shows that gravitational enhancement effects can be quite significant for thick targets.

Room−temperature cw laser operation has been achieved in Nd : CeCl3 at a threshold 0.6 times that of Nd : YAG, in excellent agreement with theoretical predictions.

The usefulness of cw laser irradiation for semiconductor surface processing is evaluated. While perfect surface cleaning has not yet been obtained, surface annealing of silicon by this technique equals and even beats classical techniques or pulsed‐laser irradiation. cw laser ‘‘writing’’ of fine surface patterns is also demonstrated.

An optical interferometric method has been used to measure the static surface deformations caused by a point‐focused cw laser. Experiments carried out in Plexiglass show that one can guess for defects or inhomogeneities under the surface through the topography of these deformations.

Fabry‐Perot nonlinear optic devices may undergo regenerative pulsations. Such effects may be used to convert cw laser power into a train of light pulses.

Deep level transient spectroscopy has been used to study the influence of the beam scan speed on quenched‐in defects in cw laser processed virgin silicon. It is shown that the averaged defect concentration decreases by almost two orders of magnitude as the scan speed is increased from 1 to 100 cm/s for a fixed temperature distribution in the material. Implications regarding technological applications of cw laser processing are briefly discussed.

We have obtained cw laser action using electron beam excitation of a He‐Hg mixture. This represents a new method of exciting cw lasers and offers the possibility of increased efficiency for ion lasers.

We have developed an optical technique for in situ measurement of temporal change and spacial profile of Si lattice temperature during cw laser annealing. This technique utilizes time‐dependent optical interference in Si films on insulator. By using a microscope for focusing a laser probe beam to 2.0 μm, time‐resolved and space‐resolved Si lattice‐temperatures were measured below the melting point (1412 °C) on a time scale of 10−4–100 s during cw laser annealing of Si on sapphire.

A high‐power noble gas cw ion laser has been constructed using a tungsten disk structure capable of dissipating over 70 kW of input power. Quasi‐continuous laser outputs in the near ultraviolet have been observed at 3638 and 3511 A of ArIII and true cw output was obtained at 3507, 4067, and 4131 A of KrIII. The latter has been identified as a new cw laser line. Over one watt of quasi‐continuous output was demonstrated with the 3638‐A line. However, high‐power continuous output in the uv is limited by serious optical degradation effects.

If you want to make an organic dye laser operate continuously, just mix the dye with a little soapy water. That recipe worked for Otis G. Peterson, Sam A. Tuccio and Benjamin B. Snavely of the Eastman Kodak Research Laboratories. Since the group reported making a cw laser (Appl. Phys. Lett. 17, 245, 1970) it has managed to make it tunable in the range 5500–6500 A and hopes soon to extend the work to other parts of the visible spectrum. Snavely says the dye laser should be tunable over the entire visible region. Although cw semiconductor lasers are tunable in the infrared, Snavely noted that the Kodak laser is the first cw tunable source in the visible range.

The two highest cw absolute frequency measurements as yet reported are described. Frequencies of the P(18) and P(20) 10.6‐μm lines from a cwCO2 laser were found to be 28.359800 THz and 28.306251 THz±0.000025 THz, respectively. The frequencies were measured by beating each of these lines with 3.8‐THz (78μm) and 10.7‐THz (28μm) radiation from a water vapor laser and a 26‐ to 28‐GHz klystron in a tungsten‐on‐nickel point contact diode.

The spontaneous and laser spectral behavior of high‐quality In1−x Gax P grown slowly from an In solution in a small temperature gradient is described. The band‐to‐band carrier decay times are measured below (2.3 nsec, 77°K) and above (0.85 nsec) laser threshold by an optical phase shift technique and indicate low bulk and surface losses (s≤104 cm/sec). Continuous laser operation of a thin In1−x Gax P sample is demonstrated at a photoexcitation level of ∼103 W/cm2 (hνpump =1.96 eV).

A gain of 20%/m and a power output of 50 mW have been measured on the 5s2 2D5/2 → 5p2P03/2 4416‐A laser transition in Cd (II) using a single isotope of Cd114. The system was operated in a tubular furnace at temperatures in the range of 200°C with He as a buffer gas. The laser output with respect to He pressure, discharge current, and furnace temperature are discussed along with a proposed excitation mechanism. The system appears to have the prospect of being one of the most efficient, high power lasers operating in the visible region of the spectrum.

cw laser action is obtained on two lines in methyl fluoride, three lines in vinyl chloride, and 23 lines in methyl alcohol by optically pumping the gases with various lines of the CO2 laser. The laser wavelengths range from 70 to 700 μm.

This letter shows that strain is a controlling factor in the rapid degradation of GaAs double‐heterostructure junction lasers. A birefringence study of these lasers reveals extensive strain fields introduced during the bonding procedure resulting from the different thermal‐expansion coefficients of the materials involved. A new bonding procedure was developed which does not introduce significant strains. Lasers fabricated with the old and new bonding procedures were subjectively categorized as low, moderate, or high strained. A direct correlation was measured between low‐strain and room‐temperature cw laser lifetime. Lasers fabricated with the new bonding procedure have operated cw for as long as 880 h.

Room‐temperature cw laser operation well into the visible spectrum (λ ∼ 6000 A) is reported for In1−xGaxP (x ≤ 0.60). Thin (1–5‐μ) experimental samples are compressed into In, under a thick (∼ 250‐μ) high‐index (η > 2. 6) SiC window, with a thin (10–50‐μ) narrow SiC platelet under part of the In1−xGaxP sample. The thin In1−xGaxP samples, in the compound cavity, are volume excited in a small spot with an argon laser so that the heat is easily removed by the SiC windows and nearby In heat sink.

A cw laser using a 2.5×10−4 M solution of rhodamine 6G in water containing a deaggregating agent (1.5% Triton‐X100) is described. The laser consists of a 4.5‐mm transverse‐flow hemispherical cavity excited longitudinally by the 5145‐A output of a 1‐W argon ion laser. With mirror reflectances of 97.5% and 99.5%, a 200‐mW threshold excitation was measured. Power output was approximately 30 mW at 597 nm with 960 mW excitation power.

We have observed cw laser oscillation on ten transitions of singly ionized iodine in a He–I2 mixture using a multiple anode‐hollow cathode laser tube of metal construction. Output characteristics as a function of helium pressure, iodine partial pressure, and discharge current have been investigated.