bluuebunny/crossref_metadata_2025 huggingface dataset:
Future of Global Optimization in Lens Design
Authors: Sturlesi Doron , O’Shea D. C.
Published: February 2023

With the incredible increase in the power of computers, lens designers can begin to contemplate strategies that would not have been possible before. More configurations can be tried; more rays can be traced; evaluation schemes can be more sophisticated. Still, there are the questions that nag every lens designer: Is that the best you can do? Isn’t there a better configuration with different glasses, curvatures, and thicknesses? The limited success of the conventional design methods in reaching the global minimum is mainly due to the fact that the solution is crucially dependent on the initial configuration. As a result, conventional design methods work satisfactorily and converge quickly to a good solution, only if a good choice of a starting point had been made. Most often, the routine ends up in an unfavorable configuration that does not satisfy the design requirements. It is not unusual for this to happen several times during the first design sessions.
MTF Optimization in Lens Design
Authors: Rimmer Matthew P. , Bruegge Thomas J. , Kuper Thomas G.
Published: February 2023

Optimization programs generally use a merit function which is related to mean square spot size or wave aberration. Direct MTF optimization has been tried, but with limited success. One problem, which makes it almost unusable in the early stages of the design, is the fact that MTF values are bounded between 0.0 and 1.0 and oscillate significantly as a function of the constructional parameters. Another is the long calculation time needed for MTF. Approximations to the MTF have generally been used. Wavefront variance and wavefront difference variance are two of the more common ones that avoid both problems but don't directly optimize MTF. The variance is closely related to MTF for systems near the diffraction limit but poorly related for RMS wavefront errors greater than about 0.2 waves. The wavefront difference variance is, likewise, applicable only over a restricted region.1
The Power of One Power
Authors: Shenker Martin
Published: February 2023

A One Power, erecting, distortion-corrected telescope is defined as a CONSTANT DEVIATION Device. When an optical instrument is called constant deviation it means that the apparent direction of any object seen through the device is constant independent of any angular rotation of the observing system relative to the object and relative to the observer.
Zoom Lens with Aspherical Lens for Camcorder
Authors: Yatsu Masahiko , Deguchi Masaharu , Maruyama Takesuke
Published: February 2023

Recent optical systems consist of spherical lens elements, because the spherical lens is suited for productin and the surface inspection. But now as the precision production and mass production technologies are developed, there are many lens systems with aspherical lens elements for still camera and projection TV.
All-Reflective Four-Element Zoom Telescope: Design and Analysis
Authors: Johnson R. Barry , Hadaway James B. , Burleson Tom , Watts Bob , Park Ernest D.
Published: February 2023

The use of all-reflective optical systems has exploded within the past decade largely due to the growth of the infrared community. With today’s design and manufacturing technology, non-traditional designs are more easily realized leading to higher quality collimators, resonators, and imagers. Nevertheless, in one area reflective technology has not kept pace - the area of zoom optical systems. This is due to several factors: difficulty of design, potentially low throughput, alignment problems, and the opto-mechanical challenge of accurately zooming relatively large reflective elements. These problems can, however, be overcome with appropriate application of today’s technology. The design process for such an all-reflective zoom telescope is presented. Fabrication, alignment, and evaluation of the system is described in a separate paper.
The Status of and Needs for Infrared Optical Property Information for Optical Designers
Authors: Wolfe William L.
Published: February 2023

Optical property data for a number of infrared materials have been reviewed, and both vendors and designers were consulted to ascertain their conception of both the needs of today and the status. Materials were reviewed in terms of their absorption, refractive index and scatter for the refractors, and for a variety of physical properties for the reflectors.
Athermalized FLIR Optics
Authors: Rogers Philip J.
Published: February 2023

All common infrared materials suffer from a relatively large change of refractive index with temperature (dn/dt); the most common material - germanium - also being the worst having a value more than two orders of magnitude higher than that for a typical optical glass. The effect of the resultant thermal change of optical power is that an all-germanium FLIR optic will rapidly defocus as temperature changes. The tolerable temperature range before this defocus results in unacceptable imagery (Strehl Ratio <0.8) can be calculated as being only approximately

±
3

1
2

°
C

for a typical all-Ge optic of 100 millimetre diameter : thus some form of athermalization is required for the successful operation of most FLIR optics.
A Nonlinear Model of the Optimal Tolerance Design for a Lens System
Authors: Zhuang Songlin , Qu Zhijin
Published: February 2023

Owing to negligence of the nonlinear property of an optimized lens system, the existing studies on the tolerance design are unable to solve the optimal tolerance design problem. For realizing this purpose, i.e. maximizing the tolerance of the lens system, we propose a nonlinear model, which can be considered as a mathematical programming problem with linear and quadratic constraints, to design the optimal tolerance of a lens system.
Optimization of the Seidel image errors by lens bending using a 4th degree merit function
Authors: Aurin Friedrich A. , Zeiss Carl
Published: February 2023

The procedure proposed works on the basis of a merit function of 4th degree and is used for the optimization of the Seidel image errors of a system composed of thin lenses by means of lens bendings. Between the thin lenses air spaces may exist. All solutions which lie within the permissible intervals of bending are taken into consideration when the sums and the corresponding surface contributions of the Seidel image errors are situated below a limit that may be selected at will.
The Exact Sine Condition in the Presence of Spherical Aberration
Authors: Shibuya Masato
Published: February 2023

Considering not only the physical meaning of pupil coordinates but also the ideal pupil curvatures, we had derived the sine condition in the presence of spherical aberration which coincides with that proposed by Marx[1,2]. The validity of this condition had been confirmed by numerical calculations of ray traces for the lens which image plane is almost flat [3].
Zoom lens design using GRIN materials
Authors: Tsuchida Hirofumi , Aoki Norihiko , Hyakumura Kazushi , Yamamoto Kimiaki
Published: February 2023

Use of the gradient-index lens (GRIN lens) in an optical system is a very useful means to reduce the number of lens elements or to improve optical performance. Several design examples using the GRIN lens have been reported so far.1),2) However, most of them are limited to lenses with fixed optical focal length.
The Calculation Method of the Strehl Definition for Decentral Optical Systems
Authors: Zhuang Songlin , Chen Huear
Published: February 2023

The Strehl Definition (S.D) is one of the commonly used criterion for evaluating the quality of an optical system, especially for the microscopic objectives.
Analysis on Image Performance of Moisture Absorbed Plastic Singlet for Optical Disk
Authors: Tanaka Y. , Miyamae H.
Published: February 2023

The plastic aspherical singlet for a compact disc was developed first by Konica Corporation in 1984.1) Since then we have supplied plastic lenses for various needs, e.g., video disks, write once disks (WORM) and erasable disks.
Tertiary Spectrum Manipulation In Apochromats
Authors: Maxwell J
Published: February 2023

The secondary spectrum curve of an achromatic lens system is U shaped such that at any two achromatised wavelengths the achromat will have a lower focal power than at the wavelength where the secondary spectrum curve has a turning point.
All Refractive Telescope for Next Generation Inter Satellite Communication
Authors: Heimbeck Hans-J.
Published: February 2023

At present optical inter satellite communication systems are under design and construction and are planned to be launched in 1993. They are based on 30mW laser diodes, the maximum available today for long lifetime single mode operation. This requires a 250 mm transmit / receive telescope, usually of reflecting type.
All-reflective Phased Array Imaging Telescopes
Authors: Stuhlinger Tilman W.
Published: February 2023

A requirement exists for a spaceborne optical telescope with a field of view of 0.25° and a resolution corresponding to an effective aperture size of ten meters or larger. One possible design is known as a phased array imaging telescope. This consists of a series of subtelescopes, with apertures substantially smaller than ten meters, and a beam combination telescope, which combines the subtelescope images into a single global image. The configuration is such that the optical path length, through any subtelescope to the global image surface, is the same for any point on a plane wavefront entering the phased array telescope. This optical phasing should occur simultaneously at all field points. Previous designs contain refractive optical components, and thus operate only over a narrow spectral range. In this paper, several all-reflective designs which meet or exceed the above imaging requirements will be presented.
Gas phase processes
Authors: Wittig Curt
Published: February 2023

In condensed media, chemical reactions can be initiated with a great deal of geometric specificity, since the forces holding the molecules in place ensure that the reactants are aligned and oriented relative to one another. Unfortunately, the surrounding medium is in constant interaction with the reactive site and no signature characteristic of the eigenstates of isolated product species can be obtained. On the other hand, binary encounters in the gas phase are especially well suited for detecting nascent excitations. However, with isotropic samples the initial conditions are unbiased so that all angles and impact parameters are present. To exploit the virtues of each of these environments, we use weakly bound van der Waals-type complexes as precursors for studying elementary processes. A prototypical example is CO2 HBr, where the potential is minimum with the nuclei along a straight line. These complexes are prepared at 2K by supersonic expansion, and photodissociation of the HBr constituent propels the H-atom toward the CO2 with initial alignment, etc., determined mainly by zero-point fluctuations of the complex. Nascent products (e.g., OH, CO) can be detected by standard spectroscopic methods before collisions become troublesome. The technique can be used to peruse the system’s ability to avoid low energy channels (e.g., with an SCOHX precursor, can OH + CS be favored over SH + CO?), as well as provide stringent tests for different kinds of calculation.
Application of a laser-induced breakdown ion time-of-flight technique as a flow velocity diagnostic in a free-jet expansion
Authors: Wantuck Paul J. , Hof Douglas E.
Published: February 2023

A time-of-flight velocity measurement technique, utilizing ions formed in a flowing gas by the process of laser-induced breakdown, is described. A highly resolved (spatially and temporally) packet of ions is produced by focusing a pulsed, high energy laser beam in the flow field of a free-jet expansion. The free-jet expansion is formed by exhausting gas through a converging nozzle into a vacuum. Such an expansion represents a flow which undergoes transition from being subsonic and continuum in nature upstream of the nozzle throat, to one that is supersonic and rapidly approaching a collision-free state downstream of the nozzle throat. The ions are produced near the nozzle exit, swept downstream along with the rest of the flow, and collected with a suitable probe. Flow velocities are deduced from measurements of the ion flight path distance and flight time. The apparatus employed for these measurements is described and actual jet-flow velocity measurements presented. In addition, velocity measurements made by the laser-induced breakdown ion time-of-flight technique are compared with similar measurements obtained by an electron beam ion time-of-flight method.
Calculations on nonadiabatic dynamics in photoassisted collisions
Authors: Julienne Paul S.
Published: February 2023

The close-coupled theory of scattering in a radiation field can be successfully used to predict excited atomic alignment (orientation) and fine structure branching when linearly (circularly) polarized laser light is absorbed by the transient quasi-molecule formed during a strong atomic collision. Specific calculations based on ab initio molecular potentials have been carried out for Sr + Ar and Na + He and Ar. Generally good agreement is found between calculated and measured branching fractions as a function of detuning up to several hundred cm-1 from the atomic resonant transition frequency. An analysis of the scattering wave function shows how the transition amplitudes can be factored into separate parts representing Franck-Condon excitation and half-collision dynamics, as for photodissociation phenomena. A simple recoil limit applies when the atoms separate in a time short compared to the time scale of angular momentum recoupling. Departures from the recoil limit can be explained in terms of axis rotation dynamics and the crossing of molecular Born-Oppenheimer potential curves.
Applications of intense subpicosecond excimer lasers for atomic and molecular studies
Authors: Jara H. , Johann U. , Luk T.S. , McIntyre I. A. , McPherson A. , Schwarzenbach A. P. , Boyer K. , Rhodes C. K.
Published: February 2023

The availability of extraordinarily bright femtosecond ultraviolet sources is enabling the study of a wide range of new nonlinear phenomena. These include the possibility or ordered driven motions in atoms, molecules, and plasmas as well as processes involving collisions, even those of relativistic electrons such as electron-positron pair production. Certain aspects of these processes are discussed.
Experimental techniques for generation of arbitrarily shaped and phased nanosecond and picosecond pulse trains
Authors: Haner M. , Spano F. , Warren Warren S.
Published: February 2023

We have shown, in a series of recent papers, that generation of laser pulse sequences with completely controlled delays, pulse shapes, and relative phases permits selective vibrational inversion, enhances velocity resolution in gases, and differentiates between relaxation mechanisms in condensed phases. We present new results with two fundamentally different technologies developed in our laboratory to produce such pulse sequences. Nanosecond pulse shaping and phase shifting is accomplished by acoustooptic modulation of a continuous ring laser.1 We have now experimentally demonstrated pulse envelopes as complicated as
Laser spectroscopy of matrix-isolated metal clusters
Authors: Moskovits Martin , Limm W. , Haslett T. , Kirkwood A.
Published: February 2023

The use of matrix isolation spectroscopy in studying the properties of small metal clusters will be illustrated. High temperature species such as Nb2, Sc3, and Cr3 will be discussed, as well as Jahn-Teller dynamical species such as Cu3, Ll3, and Ll4.
Laser spectroscopy of core-excited levels of neutral rubidium
Authors: Harris S. E. , Spong J. K. , Kmetec J. D. , Pedrotti K. D. , Wallace S. C. , Young J. F.
Published: February 2023

We describe first experimental results on a new technique for obtaining level positions, autoionizing linewidths, and oscillator strengths of core-excited levels.
Dissipative quantum and classical dynamics: driven molecular vibration
Authors: Yuan Jian-Min , Tung Mingwhei
Published: February 2023

We study quantum mechanical behavior of a Morse oscillator coupled to a bath of harmonic oscillators and driven by an infrared laser. The purpose is to compare quantum behavior of such a system with the classical and semiclassical solutions of a driven damped Morse oscillator. The general picture coming out of classical and semiclassical studies is that the total energy of the Morse oscillator in steady states or steady oscillations show jump and hysteretic behavior, as expected in a cusp catastrophe, when laser intensity or frequency is varied. Along with the bistable behavior we have also found period-doubling bifurcations leading to chaos on one or both branches. In the quantum treatment a generalized master equation is derived from the Liouville equation, in which the Hamiltonian of the Morse oscillator is expressed in terms of generators of an SU(2) algebra. This algebra and the Markoffian approximation allows us to derive the equation of motion of the reduced density matrix, which is solved numerically. Bistable behavior does not exist in this quantum treatment, but solutions do show jump behavior and bifurcation phenomenon. Experimental implications of these studies are also discussed.
Optical studies of high temperature surface reactions in ultrahigh vacuum
Authors: Anderson R. J. , Hamilton J. C.
Published: February 2023

Optical diagnostics, including spontaneous Raman scattering and second harmonic generation (SHG), allow real time in situ measurements of surface reactions at elevated temperatures. We report measurements of oxidation and other reactions on single-crystal stainless steel surfaces in ultrahigh vacuum. Raman spectroscopy provides identification of surface chemical and isotopic composition during high temperature oxidation. By combining Raman spectroscopy with ion sputtering removal of previously grown oxides, depth profiles of chemical and isotopic composition are obtained, allowing identification of diffusion mechanisms operative during oxide film growth. Through use of gated detection and pulsed laser excitation, data can be obtained, even from weak scatterers, at temperatures exceeding 1000°C. Optical second harmonic generation primarily probes the contribution due to surface layers at the interface between two centrosymmetric media. It has demonstrated sensitivity to submonolayer coverages of adsorbates on these single-crystal surfaces. We report the use of SHG to study surface segregation and other phenomena on these surfaces. These optical techniques allow information concerning surface composition and structure to be obtained at elevated temperature and at atmospheric pressure. Potential applications include the study of catalytic reactions and corrosion in realistic exposure conditions.
Resonance light scattering from a suspension of microspheres
Authors: Lettieri Thomas R. , Marx Egon
Published: February 2023

Intensity-vs-wavelength spectra of light scattered elastically from suspensions of monodisperse, dielectric microspheres were measured for both parallel and perpendicular polarizations. Whereas previous experimenters have observed sharp resonances in the spectra of single microspheres, the broad peaks observed in the present experiment are a summation of sharp resonances over the range of sizes present in the illuminated region of the suspension. Peak locations in these resonance light scattering (RLS) spectra were then compared with those computed from Mie theory to obtain a precise value for the mean diameter of the microspheres. The RLS-determined mean diameter of 9.90μm agreed to within 0.01 μm with the values measured by optical array sizing and scanning electron microscopy, both high-accuracy techniques. However, the shapes of the RLS spectra calculated for different size-distribution widths gave a standard deviation of 0.035 μm, less than half of the value obtained by array sizing and transmission electron microscopy. Mie scattering calculations for a range of mean diameters and distribution widths showed that the RLS method is useful for microsphere diameters from ~5μm to ~ 25μm, depending on the distribution width. Experimental procedures, computer analysis of the RLS spectra, sources of error, and limitations on the technique for high-accuracy microsphere sizing are discussed.
Measurement of nonlinear refractive indices of optical crystals and glasses by three-wave mixing at 1.06 µm
Authors: Chase L. L. , Payne Stephen A. , Adair Robert
Published: February 2023

We have developed a three-wave mixing apparatus for rapid and accurate measurements of the third-order nonlinear susceptibility of transparent optical materials by comparison with standard samples. The 1.06-µm fundamental of a Nd:YAG laser is mixed with a tunable beam generated from a 560-nm dye laser which is shifted to the 1.06-µm region by second order Stokes Raman scattering from hydrogen. A small frequency difference (70 cm−1) between the two beams allows the determination of the joint contributions of the electronic hyperpolarizability and the atomic displacements to the nonlinear susceptibility. Discrimination between the incident beams and the three-wave mixing signal is accomplished with a combination of filtering and a double-grating monochromator. Separate sample and reference arms allow for the suppression of noise and errors caused by long- and short-term fluctuations in laser output. The method is easily extended to higher harmonics of the Nd:YAG laser, although absolute measurements must be performed on at least one material at each harmonic in order to provide a reference sample. Measurements have been made on a number of fluoride and oxide crystals, wide band gap semiconductors, and glasses. Experimental trends regarding the composition and structure dependence of the nonlinear index and its anisotropy are discussed.
High power He–Cd+ white light laser
Authors: Fuke Akira , Masuda Katsuhiko , Tokita Yasuhiro
Published: February 2023

A new hollow cathode He–Cd+ laser—an improvement of the flute type—was investigated experimentally. Using wideband mirrors, the 194-mW simultaneous oscillation power output was obtained within the visible light range; red lines (635.5,636.0 nm), green lines (533.7,537.8 nm), and a blue line (441.6 nm), at 2-A anode current. Conversion efficiency of 0.032% was obtained. The laser tube is provided with 20 anodes on the upper side at 3-cm intervals and a cathode having an effective activated length of 61 cm. The diameter of the bore is 4 mm. Cadmium reservoirs are provided in the middle of each anode on the lower opposite side. The cathode is made of pure iron. By virtue of close contact between the cathode and the Pyrex glass envelope, the glow is condensed within the cathode bore, resulting in high efficiency. With this construction, sputtered material in the bore may quickly be exhausted out of the bore, keeping the inside of the bore clean; moreover the uniform arrangement of cadmium reservoirs over the whole length of the cathode contributes to high efficiency and stability.
Phase conjugation of 2.91-μm HF laser radiation via stimulated Brillouin scattering
Authors: Whitney W. T. , Feldman B. J. , Duignan Michael T.
Published: February 2023

We report the results of experiments demonstrating stimulated Brillouin scattering (SBS) and phase conjugation of a single-line HF laser. The 2.91 μm was selected by an intracavity grating yielding up to 3J in a 1.5-μS pulse. The flat-flat optical cavity was carefully aligned to maximize far-field intensity and the resulting spot diameter was found to be near the diffraction limit. The magnified far-field intensity profiles were imaged with film burns and with a linear pyroelectric array. This high spatial quality beam was intentionally distorted by passing it through a roughened NaCl window and the distortion was verified by examining the far-field intensity profile. This distorted beam was then focused into a cell containing xenon at 45 atm. The resulting SBS reflection passed back through the NaCl aberrator and the diffraction-limited far-field intensity profile of this reflected beam was found to be restored. This demonstration of random phase aberration and reconstruction of the laser beam provides evidence that the SBS reflection is the phase conjugate of the input beam. (12min)
Study of multiphoton resonances in Kr and Ar under an intense laser field
Authors: Tiee Joe J. , Ferris M. J.
Published: February 2023

A competition between resonant multiphoton ionization (MPI) and third harmonic generation (THG) involving three-photon resonances was first reported by Miller et al.1 Recently, a similar competing process involving four-photon resonances was observed in the multiphoton ionization of Hg2. In this paper we report a similar observation in the three- and four-photon excitation spectra of Kr and Ar. Both the multiphoton ionization and the VUV radiation generated in the focal volume are measured over a broad range of gas pressures (0.01-100 Torr) and laser fluences. The 5s, 5f, and 6p′ levels of Kr and the 4s, 4p′, and 7p levels of Ar are investigated. The spectral lines are observed to broaden and to shift from line center as a function of increasing gas pressure and laser intensity. The effect observed in three-photon resonant lines is explained by the occurrence of a competition between MPI and THG.1 A similar effect observed in the four-photon resonances is interpreted as the result of THG enhanced by the four-photon levels—a five-photon process. However, it is not clear why the four-photon spectral line-width becomes narrower when the gas pressure is further increased; this is discussed.
Transformation of coherent states of the electromagnetic field to quasi-Fock states
Authors: Zakharov V. I.
Published: February 2023

The possibility of a practically total reduction of quantum photon fluctuations in cw laser radiation is discussed. This effect appears as a result of two-photon radiation absorption using a resonance transition in atoms excited from the ground state to the upper level, relaxing to the other states. For this case the possibility of induced two-photon emission is excluded, that is, the source of additional photon number fluctuations in a field mode.1 In this process the Fock states with the photon number n ≥ 2 are continuously reduced from the coherent state of the excited field. For the large time values of interaction the Fock states |n = 0 > and |n = 1> remain in the field. The effect of spin orientations of photons of the excited field on the quantum noise reduction process for the two-photon absorption by atoms on the transitions between the S → S and S → D terms is analyzed. The possibility of transformation of coherent and thermal fields (λ ≃ 6022 Å and λ = 5787 Å) into quasi-Fock states, as a result of its two-photon resonance absorption by Na homogeneous vapor, is considered.
Excited state absorption spectrum of Zn2 in the visible and ultraviolet
Authors: Rodriguez G. , Killeen K. P. , Eden J. G.
Published: February 2023

Although the group IIB metal dimers (Zn2, Cd2, Hg2) have received considerable attention as potential bound → free (excimer) lasers, little is known of the electron ic excited states above the lowest-lying level (3Π
g
). This paper describes experiments in which the absorption spectrum of Zn2(4p3Π
g
) in the visible and ultraviolet has been observed. A quartz cell containing several milligrams of zinc was evacuated to < 10-7 Torr, sealed and heated to ~800°C. Excited Zn atoms were produced by pumping the atomic 4p3P1 ← 4s21S0 transition at 307.6 nm with an untuned XeCI laser. Diatomic molecules are subsequently formed in three-body collisions of a 4p3P1 atom with two background 1S0 species. A pulsed Xe lamp (~300-nm FWHM) provided the probe continuum. Collimated and spatially filtered, the beam from the lamp propagated through the XeCI laser-produced excited region and was detected by a 0.25-m spectrograph/diode array combination. The UV and visible are dominated by absorption bands centered at 290,390, and 420 nm. Weaker but significant bands in the 450-460-nm region are also observed. Spectroscopic identification of these bands is discussed.
Polycrystal formation during Czochralski growth of alexandrite crystals: investigation of the melt aging mechanism
Authors: Guo Xingan , Chen Meiling , Li Nairen , Chen Xinghi , Jiang Botao , Li Xiangting
Published: February 2023

There are some anomalies in Czochralski growth of alexandrite crystals, that is, as the melt becomes older it is hard to grow a clear crystal even when a good seed is used. Topographic observation and microscopic component BeAl2O4:Cr3+ crystals (three samples) grown in our laboratory was carried out by EPMA. The result shows that these three samples are not single crystals but poly­crystals in which there are grain boundaries, bubbles, and a large amount of inclusion gatherings. These cause scattering and absorption of light and spoil the transparency of the crystal. In fact, the so-called melt aging is poly-crystal formation. Analyzing the phenomena from many growth experiments and making technical experiments on how to avoid melt aging, we believe that in our technical conditions melt aging is caused mainly by unsuitable growth technology. However, the possibility that a solid solution range may exist around the BeAl2O4 stoichiometry should not be ruled out and further study is necessary. (Poster paper)
Detection of transient fluorine atoms
Authors: Nereson Norris , Fry Herbert A. , Loge Gary W.
Published: February 2023

A KrF excimer laser with a fluence of 50 mJ/cm2 was used to photolyze either uranium hexafluoride or molecular fluorine, yielding a transient number density of fluorine atoms. The rise and decay of the atomic fluorine density was observed by transient absorption of a 404-cm−1 Pb-salt diode laser, which corresponds to the 2P3/2 → 2P1/2 spin-orbital transition in atomic fluorine. To prevent the diode laser wavelength from drifting out of resonance with the atomic fluorine line, part of the beam was split off and sent through a microwave discharge fluorine atom cell. This allowed a wavelength modulation-feedback technique to be used to lock the diode laser wavelength onto the atomic line. The remaining diode laser beam was made collinear with the excimer laser beam using a LiF window with a 45° angle of incidence to reflect the infrared beam while transmitting most of the UV beam. Using this setup along with a transient digitizer to average between 100 and 200 transient absorption profiles, fluorine atom number densities of the order of 1014/cm−3 in a 3-m path length were detected. The signals observed were about a factor of 5 less than expected from known photolysis cross sections.
Properties of an optical cavity for a high-power CO2 laser
Authors: Rabczuk G.
Published: February 2023

Properties of a positive-branch nonconfocal unstable resonator in a one- and two-pass (folded) configuration, designed for a CO2-N2-He transverse flow laser excited by a high-power glow discharge1 have been studied numerically. Calculations were carried out with the help of a computer code2 that takes into account an idealized, saturable, homogeneously broadened gain medium model. The near- and far-field behavior of both configurations, as well as the theoretical dependence of the output power (P) on the small signal-gain (g0), saturation intensity (Is), mirror reflectivity (R
i
), and the discharge length (L
a
) are discussed. For g0 = 0.4/m (the average value of g0 found experimentally), l
s
= 0.5 kW/cm2, R
j
, = 0.88, and L
a
= 0.86m, our calculations predict for the one-pass cavity P = 1.6 kW and for the two-pass cavity P = 4.2 kW; measured values of P were ~1.7 and ~4.4 kW, respectively. The calculations also predict the rather poor quality of the output beam. In both cases ~90% of the output power is focused within a circle of angular width 2θ = 1.06 mrad, but only a small fraction of the beam energy (~40%) is contained in the centermost beam lobe (2θ = 0.3 mrad). According to the mirror tilt analysis there is no significant difference in the tolerances of both cavities to angular misalignment. With increasing mirror tilt noticeable distortions in the far- and near-field distributions are observed. (Poster paper)
Multibeam Borrmann effect in crystalline gamma-ray lasers
Authors: Hutton J. T. , Trammell G. T. , Hannon J. P.
Published: February 2023

The effects of crystallinity are of crucial importance in considerations regarding gamma-ray lasers, bringing in new elements of laser theory which could well prove decisive in determining whether lasing can or cannot be achieved. Certain multibeam Borrmann eigenmodes of the radiation field within a perfect crystal containing resonant Mossbauer nuclei exhibit much less photoabsorption and much stronger coupling to the nuclei (provided the nuclear transition is of multipolarity M1 or higher) than do the single plane wave channels of an amorphous system (or equivalently, off-Bragg in the crystal). These modes offer the possibility of achieving lasing with orders of magnitude less population inversion density than would otherwise be the case, provided a nondestructive means is found to achieve a population inversion. The radiation in these modes would emerge from the crystal in a number of well-defined beams, each collimated by Bragg diffraction to an angular divergence of from 10-5to 10-4 rad. The properties of these multibeam modes as they relate to gamma-ray lasers, as well as the effects of crystallinity on the optics of systems which decay by superradiant rather than stimulate demission, are discussed.
Nuclear interlevel transfer driven by collective outer shell electron oscillation
Authors: Biedenharn L. , Rinker G. , Solem J.
Published: February 2023

We discuss the possibility of exploiting the dynamic electron-nucleus interaction in order to form a nuclear population inversion in a short-lifetime excited state. We first review the situation in terms of dynamic hyperfine mixing between the nucleus and electron single-particle states. Then we treat the subject of nonlinear collective electron motion. We present results for the calculation of electron photoabsorption cross sections by the time-dependent Thomas-Fermi-Dirac-Weizsacker method1 as well as for the coupling of the resulting electron excitations to the nucleus. We also discuss the problem of premature ionization of the atoms involved.
Laser spectroscopy of jet-cooled chlorinated aromatic hydrocarbons
Authors: Rohlfing E. A. , Chandler D. W.
Published: February 2023

The ultrasensitive and isomerically selective detection of chlorinated aromatic hydrocarbons is currently a problem of particular concern due to the toxic and/or carcinogenic nature of these species and their widespread presence in the environment. In this work laser-induced fluorescence and resonantly enhanced multi photon ionization (REMPI) are applied to a series of mono- and dichloronaphthalenes that are rotationally cooled in a free jet expansion. Both techniques provide isomeric selectivity in the S1-S0 spectral region; however 1 + 2 REMPI is more sensitive. In the REMPI spectra of the dichloronapthalenes (DCNs) the S1-S0 origins of different positional isomers are separated by as much as 424 cm-1. Low resolution time-of-flight (TOF) mass spectra of the DCNs show the REMPI ion fragmentation pattern to be isomer dependent. The additional selectivity that isomer-dependent frag mentation provides is demonstrated by the different relative intensities observed in the parent and fragment ion REMPI spectra of a three-component DCN mixture. Possible extensions of the REMPI technique, including two-color, 1 + 1 REMPI for enhanced sensitivity and high-resolution TOF mass spectrometry for enhanced isomeric selectivy, are discussed.
Photothermal deflection velocimetry in laminar and turbulent ethylene flows using a transient grating
Authors: Dasch Cameron J. , Sell Jeffrey A.
Published: February 2023

The first velocity measurements in a turbulent flow using photothermal deflection spectroscopy have been made using a new enhanced-precision high-signal method. A transient refractive-index grating is formed by the interference of two pulsed pump-laser beams in an absorbing gas. The motion of the grating is detected by the oscillatory deflection of a crossed probe beam which has a diameter smaller than the fringe spacing. This two-beam pump improves on previous PDV methods using single-beam pumps because there are more markers for the velocity determination, and the increased thermal gradients increase the probe deflection. The method is illustrated by velocity maps in a dilute ethylenejet.
Light fluctuations in the laser
Authors: Mandel Leonard
Published: February 2023

When the working point of a laser is taken through its threshold of oscillation, the optical field undergoes an order-disorder type of phase transition, which is manifest in the statistics of the emitted light photons, and has been studied experimentally by photoelectric counting and correlation measurements. In a single-mode laser the phase transition is usually of the second order and continuous, but it can become discontinuous in the presence of pumping fluctuations and in multimode lasers, which also can exhibit deterministic chaos. Some lasers, like the two-mode dye ring laser, exhibit metabistability and mode switching under the influence of quantum fluctuations. These phenomena will be reviewed.
High resolution spectroscopic studies of the negative molecular ion NH− using a color-center laser
Authors: Al-Za’Al Mohammad , Miller Harold C. , Farley John W.
Published: February 2023

We have performed high-resolution spectroscopic measurements on the negative molecular ion NH−. The infrared beam of a Burleigh FCL-20 color-center laser overlaps a parallel mass-selected 3-keV ion beam and induces vibrational-rotational transitions. The laser-excited ionic state autodetaches, yielding a fast (keV) collinear neutral NH, which is detected by secondary electron emission. Resonances are observed by scanning the ion velocity with fixed laser frequency. Our results more than quadruple the number of high-precision measurements in this system. Our results include the important Q and P branches for the first time. We have observed transitions in the isotopically substituted species 15H−. Analysis of the combined isotopic data yields the anharmonicity of the vibrational potential well. Because of a kinetic velocity compression effect, this is one of the few one-photon Doppler-free spectroscopic techniques. The 3-MHz (30-ppb) resolution is equivalent to a temperature of 0.04 K. We can measure autodetachment lifetimes and resolve lambda-doubling and hyperfine structure arising from the interaction of the nuclear magnetic moments with the electronic magnetic fields. This is the first observation of hyperfine structure in this molecular system, and only the second observation of hyperfine structure in any negative molecularion.
Studies of surface dynamics using optical second-harmonic generation
Authors: Tom H. W. K.
Published: February 2023

Optical second-harmonic generation (SHG) is a surface sensitive probe from which adsorbate coverage, bonding site, and orientation have been deduced.1 Surface symmetry may also be probed with SHG.2 Here we discuss the use of SHG to study the time evolution of dynamic processes on surfaces. At typical gas-surface reaction time scales of 1 s we have been able to follow the room temperature chemisorption of oxygen on Si(111)–7X7. We find that the dangling bonds and 3m arrangement of the Si backbonds are depleted at a rate of (3.5 × 10−6Torrs)−1 while full oxidation of the Si backbonds proceeds at a slower rate of (35 × 10−6 Torrs)−1. A far more unique use of SHG, however, is to use SHG to study the surface dynamics induced by an intense laser pump pulse. Such measurements have time resolution limited only by the laser pulse width. We report recent work on laser-induced disorder/melting of Si (111) and Cu(111) single crystals with 100-fs time resolution.
Cooling cesium atoms using diode lasers
Authors: Wieman C. E. , Watts R. N.
Published: February 2023

We have cooled and stopped a beam of cesium atoms using frequency chirped diode lasers. In this technique, a moving atom absorbs and reemits many photons from a counter propagating laser that is frequency swept to keep it in resonance with an atomic transition. The resulting momentum transfer slows the atom. The basic approach is identical to that developed by Hall and co-workers, however, the use of diode lasers allows us to obtain the necessary frequency modulation simply by sweeping the laser injection current. We use two diode lasers tuned to each of the 6s hyperfine ground state levels to drive the 6s—6p3/2 transitions. Each laser is simultaneously swept over the Doppler profile of the 100°C thermal cesium beam to bring a substantial number to a stop. Using additional fast frequency modulation, the same lasers are used to probe the resulting velocity distribution. This technique allows us to bring ~106 atoms/cm3 to a temperature of 1 K. This method is an extremely simple and inexpensive way to produce cold atoms.
Nonlinear optics—25 years later
Authors: Terhune R. W.
Published: February 2023

A personalized view of the early developments and the continuing major advances in nonlinear optics will be presented.
Theoretical studies of resonant self-focusing
Authors: Ma Jing-Xiu , Xu Zhi-Zhan
Published: February 2023

Resonant self-focusing, which occurs in beat-wave excitation of electron plasma waves, is crucial both for multiline laser fusion and for beat-wave accelerators. In this paper, the resonant self-focusing effect of a dual-frequency laser beam or two laser beams with frequency difference equal to the plasma oscillation frequency in a homogeneous plasma has been studied theoretically, for the first time, by using optical mixing and the self-focusing theory. The nonlinear dielectric constant and the threshold power for resonant self-focusing have been derived analytically. The scaling laws of the threshold power with respect to laser-plasma parameters have been discussed and compared with that of usual ponderomotive self-focusing. Otherwise, the effect of the deviation from the frequency matching condition on the threshold power has also been studied. For typical underdense laser-plasma parameters, our estimation shows that the threshold power of resonant self-focusing is usually ~2 orders of magnitude less than that of normal ponderomotive self-focusing. In addition, it is also shown that a small deviation from resonance will result in a large increase in the threshold power.
Applications of shaped laser pulses to state-selective excitation and measurement of gas phase collisional dynamics
Authors: Banash M. A. , Bates J. , Lin C. P. , Warren Warren S.
Published: February 2023

We discuss experimental applications of specific phase and amplitude modulated laser pulse shapes. Electronic transitions in real molecules generally do not have a well-defined Rabi frequency because of the distribution of the orientation of the transition dipole, and because the density of states for all but the very simplest molecules causes many Doppler broadened transitions (including hyperfine components) to overlap. Crafted pulse shapes generate complete population inversions regardless of Rabi frequency, as well as provide a uniform inversion over the pulse bandwidth.1 These experiments directly observe population transfer between frequency ranges by giving two different frequency π pulses at different times—the use of crafted pulses increases signal to noise by now inverting the entire Rabi distribution. Experimental modifications which select a single velocity range in an arbitrarily complex molecule while retaining the other advantages of pulse shaping are presented, and the velocity dependence of fluorescence and coherence lifetimes in molecular gases is analyzed.2 Applications to monitoring velocity-changing collisional dynamics and generating large vibrational population inversions in l2 are presented, as will experimental methods to extend these sequences to more complex molecules, where velocity selection and frequency resolution are not equivalent.
Measurements of subpicosecond laser-produced plasmas
Authors: Milchberg H. , Freeman R. R. , Bucksbaum P. H. , Darack S. , Davey S.C.
Published: February 2023

We describe the design of a high power subpicosecond UV laser and report its use in a study of the characteristics of short-lived laser-induced plasmas. The laser consists of a mode-locked dye laser, synchronously pumped by a mode-locked argon-ion laser. The dye laser operates at 616.0 nm and is cavity-dumped, with the output pulses sent to a fiber-grating compressor. The resulting pulses are <500 fs in duration. These pulses are amplified in a series of Nd:YAG-pumped dye amplifiers, doubled in KD*P, and sent through two XeCl excimer amplifiers. Typical output pulses exceed several millijoules with <1-ps FWHM duration, yielding focused intensities of 1015W/cm2 on various targets. Plasma diagnostics include a grazing incidence monochromator, an x-ray streak camera, and particle detector. Additionally, we describe several novel methods for measuring subpicosecond plasma emissions in the x-ray and visible/IR spectral regions.
XUV laser Stark spectroscopy of Xe autoionizing Rydberg states
Authors: Ernst W. E. , Softley T. P. , Tashiro L. , Zare R. N.
Published: February 2023

Tunable coherent radiation between 90 and 110 nm is generated by frequency tripling the output of a pulsed frequency-doubled dye laser in a free jet of rare gas atoms.1 The XUV beam is crossed by an atomic Xe beam to observe single-photon transitions from the ground state of Xe to the autoionizing Rydberg series in the vicinity of the second ionization limit. A Stark field is applied in the interaction region. At moderate field strengths (>100 V/cm) wave functions with different / mix and transitions to the 5p5(2P1/2) np series are observed in addition to the ns and nd series. The line intensities and shifts have been investigated for 0 < E < 2 kV/cm. As the third harmonic XUV beam is collinear with the high power fundamental UV laser radiation, the spectroscopy of many other species is obscured by UV multiphoton absorption processes. We have studied schemes for separating XUV and UV and will discuss the application of a dichroic beam splitter.2
Interactions of line-focused laser light with plasmas
Authors: Xu Zhi-Zhan , Lee P. H. Y. , Lin L. H. , Zhang W. Q. , Zhang Y.Z. , Jiang Z. M.
Published: February 2023

Plasmas have been experimentally diagnosed produced by line-focused laser light (1064 nm, 1-20 J, 250 ps; and 0.1 x 3.5-mm focal line) irradiated planar and thin cylindrical targets. In the experiments the principal plasma diagnostics included microphotographic diagnoses of fundamental and harmonic emissions, picosecond interferometry, and shadow photography using a stimulated Raman backscattering probe beam, Faraday cups, space-resolved and space-integrated x-ray crystal spectrometers, and x-ray pinhole cameras, etc. The experimental results indicate that the space anisotropy of the ion emission from line-focused laser-produced plasma is more noticeable than that from generally spot-focused laser-produced plasma. The ion peak due to the ions accelerated by the resonantly driven electrostatic field also is more obvious. For high Z (such as Au) targets, we have observed for the first time line-focused laser beam filamentation in plasmas. The plasma jetlike structures have also been seen using optical probing techniques. In addition, the x-ray line spectra emitted from line-focused laser plasmas also display the characteristics of the spectral lines being remarkably broadened due to the large source size.
Apressurized Lenses
Authors: Dietzsch Eberhard
Published: February 2023

The influence of air pressure on the image quality, especially on the focal point position, is mostly neglected. This effect, however, may be of significance for lenses used in different environments. Apart from external focus compensations it is shown that the effect of a different air pressure may also be compensated internally. The mathematical approach is analogously to the chromatic aberrations and leads to a supplement of the well-known fundamental Calculated examples of so called 'apressurized lenses' are given.