Showing papers on "Laser power scaling published in 1969"
TL;DR: A review of papers published on laser induced gas breakdown can be found in this paper, where the material is divided into four parts: 1) breakdown mechanism, 2) plasma expansion under the influence of the laser pulse, 3) plasma decay after the end of a laser pulse.
Abstract: This paper provides a review of papers published on laser induced gas breakdown. The material is divided into four parts: 1) breakdown mechanism, 2) plasma expansion under the influence of the laser pulse, 3) plasma decay after the end of the laser pulse, and 4) bibliography of papers published on the subject up to the end of May, 1968.
180 citations
TL;DR: In this paper, self-focusing of a laser beam in a plasma is treated in terms of the ponderomotive acceleration due to the gradient of the light intensity, and the focusing of radiation within the first minima of diffraction sets a lower limit to the laser power which is of the order of 1 MW for the usual lasers if cut-off density and a plasma temperature of about 10 eV are assumed.
Abstract: Self-focusing of a laser beam in a plasma is treated in terms of the ponderomotive acceleration due to the gradient of the light intensity The focusing of radiation within the first minima of diffraction sets a lower limit to the laser power which is of the order of 1 MW for the usual lasers if cut-off density and a plasma temperature of about 10 eV are assumed
178 citations
01 Aug 1969
TL;DR: In this paper, the effect of the triplet state on the critical inversion of a flashlamp-excited dye laser has been investigated in terms of the singlet state absorption and fluorescence and triplet-state absorption spectra.
Abstract: The flashlamp-excited dye laser is presently the only type of laser capable of tunable emission throughout most of the visible spectrum. Gain and power output of the device are comparable to solid-state systems although the laser performance is hindered by thermal effects, produced by spatially nonuniform excitation of the dye, and optical losses associated with the molecular triplet state. In most of the known laser dyes, steady-state lasing is prevented by triplet state effects. The analysis of the gain of the dye laser is discussed in terms of the singlet-state absorption and fluorescence and triplet-state absorption spectra. The gain analysis is used to study the influence of the triplet state upon the critical inversion, and application of the analysis to a specific system is illustrated by the detailed discussion of the rhodamine 6G laser. A criterion for the maximum permissible triplet-state lifetime consistent with CW operation is given. The quenching of the triplet state of rhodamine 6G is shown to be rapid enough to allow CW operation, although thermal effects seem to be serious. The investigation of thermal effects is reviewed and the advantages of uniform excitation of the dye are pointed out. The minimum optical excitation power required for CW operation of a 7-cm-long rhodamine 6G laser of 2 mm diameter is estimated to be 850 watts neglecting thermal effects. A catalog of dyes, with their structures, that have been used in flashlamp-excited dye lasers is given. Various methods of tuning and mode locking the dye laser are reviewed. With a single dye a tuning range of 40 nm may be obtained by substituting a diffraction grating for one of the laser mirrors. Mode locking can be produced by placing a saturable dye absorber in the cavity.
161 citations
TL;DR: In this paper, the quantum phase-noise-limited Lorentzian power spectral densities of diode lasers were directly measured and quantitatively analyzed, and the predicted inverse dependence of linewidth on laser power was also demonstrated.
Abstract: The quantum-phase-noise-limited Lorentzian power spectral densities of ${\mathrm{Pb}}_{0.88}$${\mathrm{Sn}}_{0.12}$Te diode lasers were directly measured. Linewidths as narrow as 54 kHz were observed and quantitatively analyzed. The predicted inverse dependence of linewidth on laser power was also demonstrated. These results were obtained from the beat-note spectra produced by heterodyning the diode laser, operating cw at 10.6 \ensuremath{\mu}m, with a stable, single-frequency C${\mathrm{O}}_{2}$ gas laser.
127 citations
TL;DR: In this article, the effect of rotational-vibrational relaxation and molecular diffusion on the saturation parameter of the CO 2 laser was investigated experimentally, showing that diffusion effects can play an important role in laser beams with radii of less than a few millimeters.
Abstract: The effect of rotational-vibrational relaxation and molecular diffusion on the saturation parameter of the CO 2 laser is investigated experimentally. A summary is presented of how the theory of a two-level system can be extended to a multilevel laser system like the CO 2 laser. Published experimental results for the rate of relaxation of the upper levels are such as to suggest that diffusion effects can play an important role in laser beams with radii of less than a few millimeters. For experimental verification of the diffusion hypothesis, the gain of a sealed CO 2 amplifier is measured as a function of input power for four different beam radii. The equivalent saturation parameter derived from these measurements decreases monotonically from 97 to 25 W/cm2as the average input beam radius increases from 0.9 to 2.5 mm in the 9-mm-radius discharge tube of the amplifier.
76 citations
TL;DR: In this article, the steady-state thermal defocusing of CO 2 laser radiation (106-μ wavelength) in gases has been investigated experimentally and theoretically and the increase in the beam diameter and change in intensity caused by the self-induced index of refraction variations in absorbing gases was studied as a function of laser beam power, the absorption coefficient of the gas, and the absorption pathlength.
Abstract: The steady-state thermal defocusing of CO 2 laser radiation (106-μ wavelength) in gases has been investigated experimentally and theoretically The increase in the beam diameter and change in intensity caused by the self-induced index of refraction variations in absorbing gases has been studied as a function of laser beam power, the absorption coefficient of the gas, and the absorption pathlength A Mach-Zehnder interferometer was used to examine directly the changes in the index of refraction of the absorbing gas, which cause the thermal defocusing The experimental results compare favorably with a perturbation solution of thermal defocusing, taking into account the effects of thermal conduction and natural convection
65 citations
TL;DR: In this paper, the output power and gain saturation characteristics for a class of high speed flowing gas molecular laser are analyzed for an electrically excited fluid mixing CO2 laser based upon recent experimental measurements.
Abstract: Output power and gain saturation characteristics are analyzed for a class of high speed flowing gas molecular lasers. Those flow lasers are treated for which laser action occurs within an optical cavity with an axis transverse to the flow direction, during the vibrational relaxation period following an initial excitation process that takes place upstream of the cavity. Performance predictions for an electrically excited fluid mixing CO2 laser based upon recent experimental measurements are presented. The concept of an ``equivalent nonflow laser'' is introduced which facilitates flow laser performance analysis in certain cases.
60 citations
TL;DR: It is shown that the holographic signal depends upon dye concentration, sample thickness, and writing laser power, and it is thought that this can be improved by choice of either more highly doped systems or pure materials.
Abstract: The fluorescein–boric acid glass organophosphor has been characterized as a transient photochromic hologram receptor medium in which an excited electronic state gives rise to the holographic grating. It is shown that the holographic signal depends upon dye concentration, sample thickness, and writing laser power. The decay rate of the hologram, after the writing laser is turned off, is determined by the excited state lifetime of 1 sec, while holographic rise times are in the order of 0.1 sec. Diffraction efficiencies are in excess of 0.2% at hologram writing powers of about 500 mW cm−2. It is thought that this can be improved by choice of either more highly doped systems or pure materials.
47 citations
Patent•
26 Jun 1969
TL;DR: In this article, the first and second LASers are focused on the same spot so that the different CHARACTERISTICS can be employed on the SAME SPOT.
Abstract: FIRST AND SECOND LASERS HAVING DIFFERENT CHARACTERISTICS ARE FOCUSED ON THE SAME SPOT SO THAT THE DIFFERENT CHARACTERISTICS CAN BE EMPLOYED ON THE SAME SPOT FOR EXAMPLE, A SOLID-STATE LASER CAN MELT A SPOT ON A WORKPIECE, AND A FLUID-STATE LASER CAN MAINTAIN THE LIQUID SPOT A POSITIONING AND FEEDING TABLE IS PREFERABLY EMPLOYED TO LOCATE THE SPOT ON THE WORKPIECE AT WHICH THE COMBINATION OF THE LASERS IS ACTIVE
32 citations
TL;DR: In this article, it was shown that an axial magnetic field is not necessary to achieve high laser power in the absence of additional magnetic fields, and the laser construction was considerably simplified.
Abstract: Investigations on ion lasers with large bored tubes (7 ... 15 mm I.D.) without additional axial magnetic field are performed. An axial magnetic field is shown to be not necessary to achieve high laser power. By absence of additional magnetic fields the laser construction is considerably simplified. Experimental criterions for maximum laser power are derived by means of a previously published theoretical paper.
31 citations
TL;DR: In this paper, measurements have been made on a plasma created in a vacuum magnetic field by the focused beam from a Q-spoiled neodymium laser, which was either a 20 mu quartz or pyrex fiber or a paraffin (CNH2N+2) sphere 20 mu dia. suspended by a 1 mu quartz fiber.
Abstract: Measurements have been made on a plasma created in a vacuum magnetic field by the focused beam from a Q-spoiled neodymium laser. The target material was either a 20 mu quartz or pyrex fiber or a paraffin (CNH2N+2) sphere 20 mu dia. suspended by a 1 mu quartz fiber. The laser power was approximately 150 MW with 20 nsec pulse width. Plasma parameters were measured by means of diamagnetic loops and probes, Langmuir probes and a biased ion electron collector. High speed framing photographs show an initial spherical expansion. In the presence of the magnetic mirror field of 1200 G the expansion is stopped at a radius of approximately 1.5 cm. In agreement with theoretical predictions a slight 'bounce' is observed after which the emission light configuration becomes elliptical in shape with a dark non-luminous central region. The diamagnetic probes show beta >or=1 at this 1.5 cm radius, and the signals show a 'bounce' for r>or=1.5 cm. By scanning a photodiode across the laser beam at the exit window of the vacuum system, the time dependence of the absorbed energy by the target as a function of radius was determined.
TL;DR: In this paper, a laser interferometer for the study of earth strain is described, where changes in the length of an 800 m arm are measured by counting fringes in the interference pattern with a least count of 4×10−10.
Abstract: A laser interferometer for the study of earth strain is described. Changes in the length of an 800 m arm are measured by counting fringes in the interference pattern with a least count of 4×10−10. The output is linear and has a flat response from dc to 1 MHz and a dynamic range of 106. The laser wavelength is controlled by reference to a passive optic resonator contained in a stable environment. The wavelength stability is a few parts in 1010 for periods up to a laser lifetime (∼3000 h).
TL;DR: A flashlamp-pumped coumarin dye laser mode-locked by means of intracavity loss modulation has produced subnanosecond, millijoule pulses suitable for pumping other dye lasers or for application to fast photochemical reaction studies.
Abstract: A flashlamp-pumped coumarin dye laser mode-locked by means of intracavity loss modulation has produced subnanosecond, millijoule pulses suitable for pumping other dye lasers or for application to fast photochemical reaction studies.
TL;DR: In this paper, the power and gain capabilities of a CO2 laser are dependent upon the saturation intensity of the laser media, and a significant increase in saturation intensity for small beam radii is attributed to diffusion of excited CO2 molecules into the beam.
Abstract: The power and gain capabilities of a CO2 laser are dependent upon the saturation intensity of the laser media. Saturation intensities reported in the literature range from 22 to 100 W/cm2 for seemingly similar laser discharge tube bores, currents, gas flow rates, and gas mixtures. Measurements of saturation intensities between 7.5 and 57 W/cm2 in a CO2 laser amplifier indicate that this parameter is inversely related to the radius of the amplified beam. A significant increase in saturation intensity for small beam radii is attributed to diffusion of excited CO2 molecules into the beam. The experimental results are in qualitative agreement with a simplified derivation of a relation governing the saturation intensity which includes molecular diffusion. This effect can result in a serious overestimate of the capabilities of a large beam laser system designed with saturation intensities obtained from small diameter probe beams.
IBM1
TL;DR: To obtain diffraction-limited radiation, a GaAs injection laser of 185 micro width was operated with an external resonator and resulted in a radiance increase of more than one magnitude.
Abstract: GaAs injection laser operated with external optical resonator for diffraction-limited radiation, considering peak power and quantum efficiency
Patent•
23 May 1969TL;DR: In this paper, a single amplifier stage is used to amplify low-intensity laser light by multiple passes through a lasing material in a single laser cavity, achieving energy levels near the damage limit of the optical components of the system.
Abstract: An apparatus for amplifying laser light by multiple passes through a lasing material in a single laser cavity. A single amplifier stage now achieves what has been previously accomplished by several stages. This is accomplished by a switching mechanism which directs a laser beam into and out of the cavity at selected time intervals, thereby enabling amplification of low intensity laser pulses having a time width anywhere in the range of picoseconds to nanoseconds, to energy levels near the damage limit of the optical components of the system.
TL;DR: In this paper, a single-frequency oscillation was obtained from an Ar laser of increased power level with the help of a three-mirror Smith reflector (power in the 4880-A line was 2 watts).
Abstract: Single-frequency oscillation has been obtained from an Ar laser of increased power level with the help of a three-mirror Smith reflector (power in the 4880-A line was 2 watts). Equations and plots that permit the choice of optimum parameters of the three-mirror reflector are given. It is shown that for effective frequency selection in a high-power laser of great length it is necessary to use beam splitter reflectivities exceeding 0.5. Single-frequency lasers of this type may be used in holography.
TL;DR: In this article, the power output of a water vapor laser operating in the region from 28 to 119 μ has been increased at least five times by the addition of helium, and the optimum mixture was 1.2-torr H 2 O and 4.6-tor r He.
Abstract: The power output of a water vapor laser operating in the region from 28 to 119 μ has been increased at least five times by the addition of helium. The optimum mixture was 1.2-torr H 2 O and 4.6-torr He.
TL;DR: In this paper, a very high gain amplifier was developed by arranging for many amplifying passes to be made through one system, which can replace several when amplification of low-energy pulses is required.
Abstract: A very high gain amplifier has been developed by arranging for many amplifying passes to be made through one system. Input pulses of millijoule energy have been amplified to the damage limit of the materials (∼10 J/cm2) by this method. One such system can replace several when amplification of low-energy pulses is required.
01 Feb 1969
TL;DR: In this paper, the optical and electrical problems in the design of a beam-sampling detector for laser power, energy and pulse duration measurements are discussed with a view to achieving an accuracy of 2% relative to a fundamental detector for pulses down to 3 nsec duration.
Abstract: The optical and electrical problems in the design of a beam-sampling detector for laser power, energy and pulse duration measurements are discussed with a view to achieving an accuracy of 2% relative to a fundamental detector for pulses down to 3 nsec duration. Experiments show that a beam sampler using an ITT F4000 biplanar vacuum cell mounted in a coaxial taper is capable of this accuracy, but that the silicon diodes (EG + G SD100, Mullard BPY13A) trap some of the photoelectric charge and then release it with a time constant of up to a few microseconds giving a pulse length-dependent sensitivity: they can be used for energy measurements, however. The Mullard 90CV vacuum photo-cell holds back about 6% of the photo-electric charge for about 1μsec and can also give erratic currents up to ten times the computed saturation current: effects probably due to residual gas in the cell. The limits set on performance by the rise time and maximum linear current of the various detectors are discussed. The design of a holder for the ITT F4000 photo-cell giving a rise time constant of 0.25 nsec is given.
TL;DR: In this paper, the frequency of one axial mode of a three-mode He/Ne laser can be tuned independently from the other modes if a third mirror is added to the usual two laser mirrors.
Abstract: The frequency of one axial mode of a three-mode He/Ne laser can be tuned independently from the other modes if a third mirror is added to the usual two laser mirrors. Provided the adjustment is correct, the frequency shift is proportional to a change of the optical path length between the third mirror and the neighboring laser mirror. By observing the beat frequency of the laser, measurements of optical path variations down to 10-5A are possible.
TL;DR: In this article, a gaseous absorption cell variable attenuator for 10.6-μ-wavelength radiation, which uses forced convection to eliminate thermal defocusing effects, is described.
Abstract: A gaseous absorption cell variable attenuator for 10.6-μ-wavelength radiation, which uses forced convection to eliminate thermal defocusing effects, is described. The device is capable of attenuating high-intensity CO 2 laser radiation with negligible distortion, and results are shown for an experimental model used at an intensity level of 100 W/cm2.
Patent•
16 Jun 1969TL;DR: In this paper, a resonator of three-dimensional polygonal shape having Bragg angle reflections at the apices of the polygon is used for operation in the X-ray region.
Abstract: A laser device for operation in the X-ray region comprises a resonator of three-dimensional polygonal shape having Bragg angle reflections at the apices of the polygon. The laser is pumped by removing electrons from the innermost shelfs of atoms of the active medium in synchronism with generation of X-rays traveling in the active medium. Pumping energy is achieved by collisions of relativistic particles and laser beams or by laser beam impingement on X-ray-emitting material.
TL;DR: In this paper, LiIO 3 inside the cavity of a giant-pulse YAG laser was used to convert LiIO to SH and the green output remained stable in the 10 MW/cm 2 intensity range.
TL;DR: In this paper, a two-stage glass Baser was used to obtain 1.1 GW in an experiment with a SeOCl2-Nd3+ liquid laser.
Abstract: The laser parameters such as an inversion density, a stimulated transition cross section and a loss factor in the glass laser amplifier medium were experimentally determined. Using these values, the rate equations of Baser amplifier were solved with various input pulse forms. To get extremely high output power, it is necessary to send a very steep input pulse into an amplifier. An experiment of two-stage amplifier was performed and the maximum output power obtained was 1.1 GW, which well agreed with calculations. The various problems in amplification were considered. To get larger power, the mode locked laser was prepared. The SeOCl2-Nd3+ liquid laser seems to be more durable against a damage of laser rod. An experiment of laser amplifier consisting of glass and SeOCl2 lasers was performed. The sufficient gain could be obtained even if the center spectrum of the SeOCl2 laser was about 50 A shorter than that of the glass Baser.
TL;DR: The first observation of the central tuning dip (Lamb dip) on individual rotation-vibration transitions of the N 2 O-N 2 molecular laser was reported in this article.
Abstract: We report here the first observation of the central tuning dip (Lamb dip) on individual rotation-vibration transitions of the N 2 O-N 2 molecular laser as well as observation of the effect in the CO 2 -N 2 laser. We also demonstrate that a frequency discriminator can be generated from the tuning dip that is much sharper than one obtained from a similar laser operating at higher pressure.
Patent•
18 Jul 1969
TL;DR: In this article, a thin film of laser material is supported in the path of excitation energy capable of raising the laser material to lasing action, and at least one of the reflective coatings has a free surface which is adaptable to be displaced relative to the other reflective coating.
Abstract: A thin film of laser material is supported in the path of excitation energy capable of raising the laser material to lasing action First and second reflective coatings are disposed on either side of the thin film of laser material and at least one of the coatings has a free surface which is adaptable to be displaced relative to the other reflective coating A means is provided for displacing one of the reflective coatings, thereby changing the optical path length of the laser cavity which is formed by the laser material and the reflective coatings and producing a commensurate change in the wavelength of emitted laser energy; thus, the laser assembly is selectively tunable over a relatively narrow band of wavelengths
TL;DR: In this paper, the effect of electrical discharge on the molecular composition of a flowing carbon dioxide gas laser was examined, and the amount of dissociation depending on the pressure, discharge current, gas flow rate and the addition of nitrogen and helium was found to reach 85%.
Abstract: The effect of the electrical discharge on the molecular composition of a flowing carbon dioxide gas laser is examined. The carbon dioxide dissociates, the amount of dissociation depending on the pressure, discharge current, gas flow rate and the addition of nitrogen and helium; the degree of dissociation may reach 85%. Such dissociation reduces the laser power output, but can be controlled by the addition of about 02 torr water vapour.
TL;DR: The calculations and the experiments show that the laser intensity is critically dependent on the separation of the two coupled resonators.
Abstract: The interaction of a scanning Fabry-Perot on the laser source is investigated. The system of the modematched laser resonator and the scanning interferometer is treated analytically as amulti-mirror resonator. The changes of the laser intensity and the oscillating frequency are numerically calculated for a special case of weak coupling. The calculations and the experiments show that the laser intensity is critically dependent on the separation of the two coupled resonators.