bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the split operator Fourier transform method to the solution of the nonlinear Schrodinger equation
Authors: DeVries Paul L.
Published: February 2023

The nonlinear Schrodinger equation arises naturally in a variety of physical processes; in particular, it is fundamentally important to nonlinear optics. Both the analytic and numerical solutions of this equation have been extensively investigated; a recent review by Taha and Ablowitz1 suggests that for soliton propagation problems the method of Hardin and Tapped2 is the superior numerical method. In this paper, the split operator Fourier transform (SOFT) method, originally due to Fleck et al.,3 is demonstrated to be applicable to the nonlinear Schrodinger equation. For the particular soliton problem studied,4 the results obtained with the SOFT method are found to be an order of magnitude more accurate than those obtained with the Hardin-Tappert method.
Intensity dependence of the polarization tensor in a quantum treatment
Authors: Chencinski N. , Weiszmann A.
Published: February 2023

Recently one of the authors published a paper concerning the exact quantum mechanical description of pressure-induced four-wave mixing in which the exact expression of the transition probability was found.1 In this approach, a formal solution for the problem of multifield interacting with a single multilevel atom is presented by treating the fields fully quantized and the states in a dressed atomic picture. If we think of the four-wave mixing experiments as a case where the ω
a
, ω
b
, and ω
c
waves are sent into the medium with the fourth wave at ω
p
generated by the mixing, the output amplitude should be proportional to the component of the polarization fluctuating at the frequency of ω
p
. Based on these results, we obtained an exact quantum mechanical expression for the polarization tensor. This paper intends to explore the photon number (intensity) dependence of the polarization tensor (susceptibility) and give a comparison of the line shapes for low and high intensity of the incoming three beams. Specifically, the corresponding terms for the 31st, 32nd and 33rd terms in the Bloembergen classical expression for the susceptibility tensor will be investigated in detail.2 For no dissipation we will plot and analyze the amplitude of the polarization component at ω
p
.
On ns' autoionizing Rydberg series lines of xenon
Authors: Ueda Kiyoshi
Published: February 2023

Complex quantum defects are used to compare theoretical studies which lead to a set of eigen quantum defects μ
α
and associated transformation matrix U
iα
with experimental studies which determine the resonance energies and the resonance widths of lines using the specific example of the ns'autoionizing Rydberg series of xenon. To calculate the resonance energies and the resonance widths, one first calculates a submatrix χ
cc
, the closed- closed part of a smooth scattering matrix
χ
, for each set offμ
α
and U
iα
values available from different theoretical studies1 Then χ
cc
, which has complex matrix elements, is diagonalized to obtain complex quantum defects as the diagonal elements. Finally, the resonance energies and the resonance widths are calculated from the real and imaginary parts, respectively, of the complex quantum defects. The results are compared with available experimental data2
Laser bandwidth effect on photoelectron angular distribution for resonant two-photon autoionization of H2
Authors: Ganguly Susmita , Dastidar K. Rai
Published: February 2023

In this two-photon process, the H2 molecule is excited from the ground vibrational level (v
g
= 0; j
g
= 0) of the x′Σ
g
state to different vibrational levels (v
i
= 0,1,2, j
i
= 1) of the B′Σ
u
state and thereafter either to the lowest autoionizing state of ′Σ
g
(1σu2) symmetry or directly to the ionization continuum (

H
2
+

:

x
2

Σ
g

; v
l
= 0,1, 2; j
l
= 0). Energy of the autoionizing state is −0.4632 a.u., which corresponds to the turning point R = 2.4 a.u. The wavelengths required for the above transitions are 1100 and 1500 Å, respectively. Resolvent operator technique has been used to obtain photoelectron (PE) angular distribution.1,2 The laser bandwidth (γ
L
) has been found to have different spectacular effects on PE angular distribution depending on laser intensities and also on the relative magnitude of the bandwidth compared to the spontaneous decay width (γ
a
) of the intermediate resonant state. Moreover γ
L
affects the PE angular distribution differently for transitions combining different intermediate (v
i
, j
i
) and final vibrational levels (v
l
, j
l
). Significant departure from the usual feature [≈1 + βP2(cosθ)] for PE angular distribution was noticed for larger bandwidths.
Inter-Rydberg spectroscopy of Kr2 5p3IIg
Authors: Abele C. C. , Eden J. G.
Published: February 2023

Recently, the

n

p
3

∏
g

←
5

s
3

Σ
u
+

Rydberg series of Kr2 was observed in absorption.1 Also, the higher members of the series were observed by dye laser excitation spectroscopy.2 Both approaches examine the rare gas dimer states near the equilibrium internuclear separation. This paper describes the study of the

5

p
3

∏
u

,
3

Σ
g
+

←
5

s
3

Σ
u
+

inter-Rydberg transitions by dye laser excitation spectroscopy. These experiments involve producing the

Kr

2

3

Σ
u
+

species by two-photon excitation of atomic Kr followed by three-body formation of

Kr

2
*

. A subsequent dye laser pulse populates vibrational levels of the

Kr

2

5

p
3

Σ
g
+

and 3Πg states. Production of a Rydberg state is detected by monitoring Kr 5p → 5s emission. The spectroscopy of the 5p3Π
g
and

3

Σ
g
+

states and their asymptotic structure are discussed. Also, the appearance of two-photon (sequential) absorption at high dye laser intensities is described.
Theory of an infrared irradiated adbond
Authors: Van Smaalen Sander , George Thomas F.
Published: February 2023

The dynamics of an adsorbed atom irradiated by an infrared laser in resonance with the vibrational levels of the adbond can be described by the reduced density matrix of the adbond. A nonperturbative approach for the laser-adbond interaction is presented. Relaxation against the substrate degrees of freedom is described by second-order perturbation theory. Both pulsed lasers and cw lasers are considered. Expressions for the transition probabilities are derived in the low-intensity and in the high-intensity limits. It appears that the time evolution of the occupation probabilities is coupled to those of the coherences, i.e., a master equation cannot be obtained. The time evolution of all the elements of the reduced density matrix has to be taken into account. These expressions act as a basis for the study of physical processes as resonant de sorption, resonant heating, and laser-induced thermal desorption. Resonant desorption is described by the addition of loss terms into the equations of motion of the occupation probabilities. Expressions for the rate of desorption as well as the rate of energy transfer to the substrate are given. In particular, a comparison is made for the effect of a cw laser vs a pulsed laser on the desorption and resonant heating.
Optical bistable interaction of laser radiation with micro-particles
Authors: Leung K. M.
Published: February 2023

Intrinsic optical bistability in the scattering and absorption of laser radiation from microparticles having an intensity-dependent refractive index is investigated.1 We work only with particles whose radius is small compared with the wavelength of the incident radiation. Our calculation is based on the assumption that the electric field inside the particle is in fact uniform (as is the case in the linear regime). For particles with fairly sharp surface piasmon resonances, optical bistability can occur if the frequency detuning is above a certain critical value. The threshold intensity is found to be reduced by several orders of magnitude compared with the non-resonant case. Optical switching can also occur at fixed intensity above the threshold by sweeping the frequency across the resonant frequency. Right at the critical detuning frequency, the particle can act as an optical transistor with a very sizable differential gain. Spherical1 as well as elongated microparticles2 are studied. In the latter case, optical tristability can also be achieved, and there are, in addition, interesting shape dependence and orientational effects.
Laser-induced surface chemical epitaxy: a novel thin film deposition technique
Authors: Stinespring Charter D. , Freedman A.
Published: February 2023

A new laser-induced epitaxial growth process is described, and key issues regarding the feasibility of the technique are discussed. Unlike conventional laser-induced processes which generally involve both surface and gas phase photochemistry, the present technique involves only photon-induced surface chemistry. Thus, it is termed laser-induced surface chemical epitaxy (LSCE). The results of x-ray photoelectron studies of thermal and photon-induced surface processes aimed at understanding the mechanisms of the technique are described. This includes meas­urements of reactant sticking coefficients, contaminant levels, and the identification of surface photodecomposition and reaction products. The impact of these results on the feasibility of the LSCE technique and the potential for depositing quantum well and related structures are also presented.
Near-resonant energy transfer theory applied to nonresonant processes: CO2, N2O, and their isotopic analogs
Authors: Godar Douglas E. , Mcnesby Kevin L. , Bates Richard D.
Published: February 2023

An expression for vibrational energy transfer cross sections has been derived, assuming an electromagnetic interaction, using the quantum first Born approximation. An exact solution has been obtained for the total cross section, which must then be averaged numerically over velocity and rotational state distributions. The formula is valid even when the energy defect becomes of the order of or larger than kT. The theory has been applied to energy transfer between two linear molecules, which occurs via long-range near-resonant processes involving the infrared transition moments of each molecule. The resulting thermally averaged cross sections agree with experiment to within a factor of 2. This represents an improvement of several orders of magnitude when ΔE ≥ kTover previous calculations based on the approximate solution to a semi-classical first Born approximation first obtained by Van Kranendonk1 and extended by Sharma and Brau and Cross and Gordon.2 This expression is applied to previous and new experimental measurements of energy flow in CO2 and N2O and their isotopically substituted analogs, providing an effective probe of rate processes of importance to molecular infrared lasers.
Multiphoton ionization and fragmentation study of acetone at XeCl excimer laser radiation
Authors: Liu H. X. , Li S.T. , Han J. C. , Zhu R. , Guan Y. F. , Wu C. K.
Published: February 2023

Multiphoton ionization and fragmentation of acetone are studied with a diffuse molecular beam and aXeCl excimer laser. The present experiment shows that no parent ion peak can be observed, only two ion peaks appear at m/e = 43 and 15 which are assigned to CH3CO+ and

CH

3
+

, respectively. The intensities of these ions are proportional to the 3rd and 3.6th power of laser intensity, respectively, and both are proportional to the 0.9th power of the acetone pressure. On the basis of our experimental results, a novel kinetic mechanism is presented, which takes account of the fact that acetone fails to be excited by the two-photon transition of

D
˜

←

X
˜

1

A
1

at 308 nm. Instead it undergoes single-photon dissociation into neutral fragments of methyl and acetyl, because the serious leakages from the intermediate state

A
˜

3

A
2

makes it impossible for acetone to climb the second step of the multiphoton transition ladder, resulting in the absence of the parent ion at 308 nm. Ch3CO+ is formed by direct two-photon resonant ionization of acetyl radical, and

CH

3
+

is produced by simultaneous two-photon absorption of methyl radical to

C
˜

state followed by one-photon absorption into the ionization continuum.
Fe(CO)5 multiphoton fragmentation and ionization dynamics by XeCl excimer laser
Authors: Li S. T. , Han J. C. , Liu Z. A. , Liu H. X. , Wu C. K. , Shi J. L. , Li F. L.
Published: February 2023

This paper reports that FE(CO)5 muitiphoton ionization mass spectroscopy induced by a XeCl excimer laser was investigated, with a diffuse molecular beam and a modified quadrupole mass spectrometer. Various fragment ions, such as Fe+, CO+, FeC+,

Fe

2

(
CO
)

4
+

, and

Fe

(
CO
)

n
+

(
n
=
1
,
2
,
…
5
)

were observed. The Fe+ signal is much larger than other ion signals, and the Fe(CO)+ signal is weakest among

Fe

(
CO
)

n
+

(
n
=
1
,
2
,
…
5
)

. The dependence of the ion signals on pressure and laser intensity was measured. For

Fe

(
CO
)

n
+

(
n
=
1
,
2
,
…
5
)

, the pressure-dependent signals show a double index first and become linear as the pressure increases; the power indices of laser-intensity-dependent signals vary between 2 and 4, closing to that of the Fe+ signal; the power indices decrease and become saturated with increasing laser intensity.
Near-field phase measurements of diode laser arrays
Authors: Dente Greg , Depatie Dave , Wilson Kim , Querns John
Published: February 2023

We have developed a self-referencing interferometer that will allow phase measurements of the near field of diode arrays. The method uses a double-slit aperture that is scanned across a magnified image of the diode near field. The far-field double-slit fringe locations then give a direct measurement of the phase difference between the two slits. We can then reconstruct the phase using the sampled difference data. The method has several advantages over other interferometric techniques including (1) the wavefront is interfered with itself, so that a separate reference wavefront is not needed; (2) the method is insensitive to array near-field intensity variations so that fringe maps need not be deconvolved from intensity variations; (3) the method works well in the presence of broadband radiation. The source needs very little coherence length which is quite an important consideration for diode lasers. Data from several commercially available devices are presented. (Poster paper)
Supercapacity information storage by no-phonon photochemical hole-burning
Authors: Huang Yong-Kai
Published: February 2023

No-phonon spectral hole-burning produced by condensed organic impurity large molecules under laser irradiation is not only narrow in width, high in sensitivity, but lasts a long time. It therefore has a bright application future.
Picosecond cage recombination measurements of polyatomic free radical pairs
Authors: Scott T. W. , Liu S. N.
Published: February 2023

Geminate free radical recombination is an important testing ground for current theories of chemical reaction dynamics in liquids. The work described here deals with the recombination of phenyl thiyl radicals in liquid hydrocarbons. Photolysis of diphenyl disulfides using near-ultraviolet light generates thiyl radicals which are detected by picosecond transient absorption spectroscopy. We find that the rate and extent of cage recombination is controlled by solvent viscosity and by the dipole-dipole reorientation energy of a polar radical pair. In moderately viscous liquids such as decalin, for example, cage recombination occurs with a 50% yield and with a half-life of ~150 ps. The influence of both temperature and solvent composition on recombination can be explained by a simple hydrodynamic model of diffusion controlled reactions, using a radiation boundary condition that mimics the reorientation barrier. In polar liquids, cage escape is enhanced by solvation of the radical pair. Based on the interpretation of these experiments it appears that the use of chemical substituents to alter the dipole movement of the radical can be used to study the recombination dynamics in more detail.
Applications of ultraviolet resonance Raman spectroscopy to protein structure
Authors: Mayne Leland C. , Harhay Gregory P. , Hudson Bruce
Published: February 2023

Resonance Raman spectroscopy of heme proteins and the visual pigments has provided valuable insights into the mechanism of action of these proteins. The performance of Raman experiments with ultraviolet radiation permits resonance with nonchromophoric components of proteins including the peptide bond itself.1,2 Fluorescence from the aromatic residues of proteins does not obscure the Raman signal because the fluorescence occurs at longer wavelengths. The peptide bond gives rise to new Raman active bands with ultraviolet excitation.2 The imino linkage of X-proline sequences results in absorption in the 220–240-nm range where normal amino linkages are transparent. This permits the selective excitation of this group relative to the predominant amino peptide bonds. This is of particular interest with respect to the involvement of isomerization of the X-proline linkage in protein folding. Recent results using radiation in the 150–200-nm region are presented.
Diffraction, dispersion, propagation, and coherent transient effects in unidirectional nonlinear ring cavity optical bistability
Authors: Mattar F. P. , Claude Y.
Published: February 2023

We report the transient nonadiabatic generalization of Bonifacio-Lugiato1 cw nonlinear ring cavity optical bistability (NRCOB) with mirrors that ensure the necessary feedback. A semiclassical formalism is adopted, consisting of a paraxial wave equation coupled to the two-level sharp-line density matrix which includes detuning and relaxation times in conjunction with boundary conditions at the mirrors. The existing super-fluorescence finite difference code2 with radial variations of the Beer length has been modified to simulate the NRCOB with the free space propagation between the mirror treated with a finite Hankel series.3
Generation of solitons in transient stimulated Raman scattering by optical phase shifts
Authors: MacPherson D. C. , Carlsten J. L.
Published: February 2023

At the present time several groups are studying the use of optical phase shifts to initiate soliton formation in transient stimulated Raman scattering.1 Our experiments use a generator-amplifier Raman laser which is pumped by a frequency-doubled Nd:YAG laser at 532 nm. The Raman medium is hydrogen at 1-100 atm. We are studying the use of an electrooptic crystal to place a π phase shift in the Stokes beam between the generator and the amplifier. This shift momentarily causes energy transfer from the Stokes to the pump beam. Surprisingly, numerical calculations indicate that in one configuration the speed of the electrooptical switch need not be faster than the coherence time of the medium to generate a soliton pulse considerably shorter than the coherence time. Thus it appears that this technique can be used to generate pulses considerably shorter than those produced using standard electro-optical switching techniques. Numerical calculations and experimental results are presented.
Measurement of the ruby luminescence spectrum under shock compression
Authors: Horn Paul D. , Gupta Y. M.
Published: February 2023

The wavelength shift of the ruby luminescence R-lines is commonly used for pressure calibration in static high-pressure studies. In addition to this, there is considerable interest in the application of spectroscopic techniques to shock wave experiments in condensed matter. A technique has been developed to record the ruby R-line spectrum continuously during shock loading (typically for a duration of 1μs) with a time resolution of ~40 ns. Experiments to longitudinal stresses of 40-99 kbar have demonstrated the feasibility of this technique. The use of optical fiber to transmit laser light to and luminescence from the ruby target is a key factor in the apparatus design; therefore, the transmission spectrum of shocked optical fibers was also examined. Recent improvements in the experimental design and assembly have yielded quantitative information about the wavelength shift under shock loading.
Coherent radiative control of product yields and quantum state populations in photodissociation
Authors: Brumer Paul
Published: February 2023

A method for controlling branching unimolecular reactions, developed in collaboration with M. Shapiro of the Weizmann Institute, which uses the coherence of weak lasers, is presented. It is shown that preselected chemical products may be obtained, in preference to others, by utilizing the interference between naturally occurring processes. Our specific application then entails the dissociation of a bound superposition state with control attained by manipulating the relative intensities and phases of coherent laser beams. Enhanced yields of chemical products of interest are shown to result. Similar control is attainable for the populations of individual product quantum states. Computational results on the I*II branching ratios in the photodissociation of CH3, I and FI are presented as examples. Proposals for experiments which demonstrate coherent control present a challenge to the laser community which is well worth accepting.
Coherent pulse sequence induced control of selectivity of reactions
Authors: Rice Stuart A.
Published: February 2023

We present a novel approach, suggested by Tannor and Rice, to the control of selectivity of photochemical reaction products. The central idea is that in a two-photo or multiphoton process that is resonant with an excited electronic state, the resonant excited state potential energy surface can be used to assist chemistry on the ground state potential energy surface. By controlling the delay between a pair of ultrashort (femtosecond) laser pulses, it is possible to control the propagation time on the excited state potential energy surface. Different propagation times, in turn, can be used to generate different photochemical products. There are many cases for which selectivity of product formation should be possible using this scheme. Our examples show a variety of behaviors ranging from virtually 100% selectivity to poor selectivity, depending on the nature of the excited state potential energy surface. Branching ratios obtained using a swarm of classical trajectories are in good qualitative agreement with full quantum mechanical calculations.
Fluorescence of molecules near small metal particles
Authors: Harris T. D.
Published: February 2023

Small particles and rough surfaces of certain metals are known to give anomalously high electric fields when illuminated with radiation resonant with the plasmon oscillation of these structures. The most widely publicized manifestation of the high field is the surface enhanced Raman effect. Equally dramatic but less well known is the large change in radiative and nonradiative rates for molecules near these structures. A reduction of fluorescence life time of 104 with no loss in quantum efficiency has been reported. This fast radiative rate has been used to give recovery in quantum yield of 103 for heavily quenched fluorophor. We present further studies on the extent to which radiative and non-radiative rates can be controlled using metal particle substrates. Self-quenching, surface treatment, scattering, and the difficult engineering associated with this method are discussed. Prospects for large scale production of substrates and application of the effect to quantitative fluorescence analysis is assessed. The direction of future study required to realize in practice the large demonstrated effects is presented.
Laser-based circular dichroism detection of molecules in flowing liquid systems using high-frequency polarization modulation
Authors: Synovec Robert E. , Yeung Edward S.
Published: February 2023

A highly sensitive and selective laser-based circular dichroism detector for flowing liquid systems, specifically liquid chromatography (LC), is presented. This detector is quite useful for the analysis of biologically related molecules, since optical activity is detected for low nanogram (ng) quantities of samples. Both transmission detected (TDCD) and fluorescence detected circular dichroism (FDCD) were developed for LC. For LC-TDCD, an argon ion laser is operated at 488 nm and 20 mW, with high-frequency polarization modulation employed to reduce laser amplitude noise to1 part in 106, i.e., a signal-to-noise ratio of 106. This is in contrast to a signal-to-noise ratio of 102 for an argon-ion laser before any effort is made to stabilize the power fluctuations. Also, detection selectivity is demonstrated since optically inactive, yet absorbing, molecules do not produce an appreciable detector response. Presently, the optimum modulation frequency range is from 500 to 700 kHz for our system. Similarly, for LC-FDCD, a He-Cd laser is operated at 325 nm, with ~8-mW power, at 150 kHz. Specifically, riboflavin is detected in LC-FDCD at subnanogram levels with optical activity information.
Fluorescence line narrowing and high resolution analysis of DNA and globin damage from carcinogens
Authors: Cooper S. , Jankowiak R. , Small G. J.
Published: February 2023

Approximately 70% of cancers are believed to be initiated by genotoxic agents. As enzymatic repair of damaged DNA is very body specific, body burden and fundamental studies of chemical carcinogenesis require the development of new bioanalytical techniques which can directly determine damage of intact DNA from carcinogenic matabolites. Assessment of damage at a level of ~1:109 base pairs is required for ~10-100 μg of DNA. To be most useful the technique should possess the selectivity to distinguish between structurally very similar DNA-metabolite adducts. In both regards, laser-excited fluorescence line narrowing (FLN) has recently been shown to be promising.1-3 Attention has focused on metabolites of PAH (polycyclic aromatic hydrocarbons) and the adducts they form with DNA. Data are presented which demonstrate that adducts from chrysene, 5-methyl-chrysene, benzo[a]pyrene, and ben[a]anthracene can be distinguished. The detection limits for FLN are discussed.
Statistical fluctuations in multimode laser transients
Authors: Yu A. W. , Zhu S. , Roy R. , Scalora M. , Haus J. W.
Published: February 2023

A newly developed method has been used to characterize the fluctuations in a unidirectional ring laser with a small number of modes. The technique of first passage time (FPT) distributions has been used earlier to study quantum (additive) and pump (multiplicative) noise in single-mode dye ring lasers.1 When applied to a two-mode laser, the FPT distributions may be double-peaked.
High power CO2 and its applications
Authors: Hertzberg Abraham
Published: February 2023

The invention and development by Ali Javan and his colleagues of the helium neon gaseous laser stimulated many physicsts and engineers to study other possible gaseous laser systems. The discovery by Kumar Patel of the N2–CO2 system then set the stage for the development of the first high power cw system. It should be pointed out that, even prior to the introduction of the nitrogen-CO2 system, engineers and scientists were already examining the implication of flow on the performance and power capabilities of potential gaseous laser systems, in the 1960s, N2–CO2 systems were rapidly upgraded from watts to near-megawatts of continuous power through the synergy of fluid mechanics and gas physics. The work was particularly appealing and benefited from the prior work of physicists and engineers who were already invovled in the study of reacting flow systems via their interest in combustion and/or reentry physics. The availability of efficient conversion of electrical or thermal energy to coherent radiation energy immediately stimulated a search for applications such as directed energy weapons, beam power, and the application of laser technology as a new tool for materials processing.
Excimer lasers
Authors: Benedict Rettig
Published: February 2023

From their first lasing demonstration in the mid-1970s, excimer lasers have rapidly evolved and now have excellent potential for a wide variety of military and civilian applications. They are the most efficient ultraviolet lasers to date and recent technology advancements have shown they are scalable to large pulse energies and possibly high average powers. Furthermore, at moderate average powers, very long operating lifetimes have been demonstrated with discharge pumped excimers. Pulse energy scaling for electron-beam pumped excimers has been highly successful with multikilojoule energies obtained in both XeF at 353 nm and KrF at 248 nm. Discharge scaling has also been successful to tens of joules. Substantial progress has been made in large area cathodes with very uniform current densities. Optical coatings at this short wavelength are extremely challenging, and although progress has been good, developments are needed to enable long life at modest fluences in thecorrosive halogen environments. Average power technologies are being pursued by many groups and progress will be highlighted.
Evolution and prospects of laser Raman techniques
Authors: Delhaye Michel , Bridoux Michel
Published: February 2023

The development of linear and nonlinear Raman methods widely exemplifies the advantages and capabilities of lasers. This paper summarizes and illustrates the evolution and the progress of Raman techniques during the past decades in the light of various areas of applications.
Photoconducting antennas
Authors: Auston D. H. , Nuss M. C. , Smith P. R.
Published: February 2023

Photoconductors have proved to be extremely effective sources of very short electrical pulses.1 When illuminated by ultrafast optical pulses they have been used to generate electrical transients as fast as 0.5 ps. The frequency spectrum of these pulses extends from dc up to terahertz frequencies, making them potentially useful sources of microwave, millimeter-wave and far-infrared radiation.
High-speed GalnAsSb/GaSb PIN photodetectors for wavelengths to 2.3 μm
Authors: Zyskind J. L. , Bowers J. E. , Srivastava A. K. , Burrus C. A. , DeWinter J. C. , Pollack M. A.
Published: February 2023

Photodetectors are needed for future communications systems utilizing novel mid-infrared fiber materials with extremely low predicted losses in the 2–4-μm wavelength range. We report improved performance of front-illuminated GalnAsSb/GaSb PIN homojunction photodiodes1 that operate with high speed and high quantum efficiency at room temperature. The photodiodes consist of a Zn-diffused homojunction 0.3 μm below the surface of a 3-μm thick layer of n-type Ga0.82ln0.18As0.17Sb0.83. This layer was grown by liquid-phase epitaxy on a GaSb substrate and doped with Sn to a level of n = 2.5 × 1015cm−3. A partial metallization of the 100-μm diam mesa surface allows for front illumination of the chips, which are packaged as described in Ref. 2. The external quantum efficiency without antireflection coating is constant at 55–65% for wavelengths up to 2.2 μm. At 1.06 μm the impulse response of the detector has a FWHM of 110 ps. At 1.3 μm it responds to pseudorandom modulation at bit rates up to 4 Gbit/s.
Autodetachment spectroscopy of negative ions
Authors: Neumark Dan
Published: February 2023

No summary was available at press time.
Infrared spectra of the isotopes of H3+
Authors: Foster S. C. , McKellar A. R. W. , Watson J. K. G.
Published: February 2023

H3+ is the simplest polyatomic molecule, and its existence, physical stability, and equilateral triangular structure have been known for many years. However, precise experimental information was lacking until 1980, when infrared spectra were reported for H3+ by Oka and for D3+ by Shy, Farley, Lamb, and Wing. Since that time there have been considerable advances in the spectroscopy of H3+. We have measured extensive spectra of all four isotopes (H3+, H2D+, D2H+, D3+) in the 1800–2500-cm−1 region using tunable infrared diode laser sources, a cooled hollow-cathode absorption cell, and a discharge-modulation detection scheme. These data have permitted us to make detailed analyses of the degenerate v2 bands of H3+ and D3+, as well as of the Coriolis-coupled v2 and v3 bands of the mixed isotopes H2D+ and D2H+. The results are summarized and compared, and an extension of the H3+ spectrum to higher values of J is discussed.
Infrared laser-induced desorption of NO and CO from alumina substrates
Authors: Weber W. H. , Poindexter B. D.
Published: February 2023

We present results of laser-induced desorption experiments on layers of CO and NO physisorbed at low temperatures (5–40 K) on fire-polished alumina substrates. The radiation source is a linetunable CO laser capable of operating on over 400 lines in the 1500–1900-cm−1 region with a cw output power on the strong lines of 0.3–0.5 W. The experiments are carried out in a bakable UHV chamber with coverages of about a monolayer. The desorbed molecules are detected with a quadrupole mass analyzer operating in a time-of-flight mode. The desorption yields from both molecules show a broad, nonresonant (wavelength-independent) behavior. Additionally, NO shows a strongly resonant peak at 1843 cm−1 that we attribute to the direct excitation of the NO stretch mode. Effective temperatures for the desorbed molecules are obtained by fitting the time-of-flight data to a Boltzmann distribution. These vary from approximately the substrate temperature to 10–20 K higher, depending on the laser fluence and the substrate temperature.
Nonlinear Doppler-free spectroscopy of atoms near a surface
Authors: Simoneau P. , Le Boiteux S. , De Araujo C. , Bloch D. , Ducloy M.
Published: February 2023

Up to now, Doppler-free nonlinear spectroscopy has been applied to atoms inside a gas medium (volume spectroscopy). We have extended these methods to atoms in the vicinity of a surface. The basic principle consists of monitoring reflectivity changes produced when a laser beam, incident on a glass–vapor interface, is brought into resonance with an atomic transition. For Doppler-free spectroscopy, two counterpropagating beams are used to operate velocity selection. If these two beams are under normal incidence in the glass—velocity selection perpendicular to the surface—one observes saturated dispersion (selective reflection sensitive to the real index). For incidence angles in the glass (prism) larger than the critical angle (total internal reflection), a standing evanescent wave is produced in the gas (velocity selection along the surface), and saturated absorption is detected. Experimental demonstration was performed on the Na resonance line; high sensitivity (10−4 relative reflectivity change) and spectral resolution as good as 20 MHz were obtained. The main limitation to better resolution comes from the short atomic transit time in the evanescent wave (typical extension ~λ). Relevant applications of these techniques should also concern the diagnostics of optically thick media, as analysis of interaction between gas-phase atoms and the surface, notably atom–wall collisions, and modification of the spontaneous emission characteristics.
Second harmonic and sum frequency generation on dye-coated surfaces using collinear and noncollinear excitation geometries
Authors: Muenchausen Ross E. , Nyugen Dinh C. , Keller Richard A. , Nogar Nicholas S.
Published: February 2023

Previous studies of second-order nonlinear phenomena at surfaces employed second harmonic generation (SHG) with acollinear excitation geometry. The surface specificity of SHG has been clearly demonstrated by many workers. Since the nonlinear generation occurs over distances corresponding to a few monolayers, phase matching is inherently satisfied. Sum frequency generation (SFG) should also be observable for both collinear and noncollinear excitation geometries, although the phase matching requirement will be more stringent for the latter case due to angular variations of the linear Fresnel factors. We have demonstrated that doubly resonant SFG is enhanced by more than 2 orders of magnitude relative to resonant SHG for submonolayer coverages of rhodamine 6G, in good agreement with theory. A pulsed dye laser probed the S1←S0 transition of rhodamine 6G (~525 nm) in combination with the Nd:YAG fundamental (1064 nm) such that the sum frequency output was also resonant with the S1←S0 transition. In addition, results for the noncollinear excitation of second harmonic and sum frequency generation from rhodamine 6G coated substrates demonstrate phase matching is easily met for crossing angles < 15°. The output beam coherence can be exploited to achieve spatial separation from the incident beams.
Multimode and fluctuation effects in stimulated Raman scattering
Authors: Raymer Michael G.
Published: February 2023

Experimental and theoretical studies of stimulated Raman scattering (SRS) involving temporal and/or spatial incoherence are reviewed. In the case of a transform-limited (in space and time) pump pulse, SRS may be generated either coherently or incoherently, depending on the geometry of the interaction volume and on the rate of collisional dephasing. Spatial coherence is governed by the Fresnel number of the volume, while temporal coherence is governed by the average number of collisions occurring within the Stokes pulse duration. These coherences manifest themselves in the pulse-energy probability distribution of Stokes pulses.1 In the case of a pump pulse that is diffraction-limited but is multimode in frequency, the generated Stokes pulse has intensity modulations that are correlated to those of the pump pulse. The degree of correlation depends on the average number of collisions occurring during a single intensity fluctuation (i.e., ratio of Raman linewidth to laser bandwidth).2
Single atomic particle at rest in free space
Authors: Dehmelt Hans
Published: February 2023

Zero-point level confinement1 in a trap is the quantum-mechanical equivalent of the classical single particle at rest in free space. Such confinement has been demonstrated—by the continuous Stern-Gerlach effect—only for the 150-GHz cyclotron motion in geonium, a single electron permanently confined in a cold Penning trap. Localizing the electron to ≈ 60 μm in the node of a standing wave in the trap cavity approximated free space, but decreased spontaneous emission tenfold. Driving the 60-MHz axial motion on a sideband higher by the ≈ 12-kHz magnetron frequency forced the magnetron motion to absorb the excess photon energy, shrinking its radius to ~ 15μm. Analogous laser cooling has reduced the oscillation amplitude of a Ba+ ion in a Paul rf trap to < 120 nm. As in nuclear magnetic resonance, confinement is now much smaller than the wavelength and sidebands disappear. Quantum jumps to and from an electronic metastable level of Ba+ have been demonstrated. Using In+ or a similar ion, this may make a monoion oscillator optical frequency standard with a 1000-day reproducibility of 10-18 possible.
Angular dependence of the vibrational Raman linewidths in H2
Authors: Herring G. C. , Dyer Mark J. , Bischel William K.
Published: February 2023

Raman beam clean-up and aperture combining, currently a topic of intense research, improves the spatial mode of coherent light sources by using stimulated Raman scattering to amplify a high quality Stokes beam. Energy is transferred from several high intensity pump beams to the Stokes seed beam by crossing the pump beams at small angles to the Stokes beam. Thus the angular dependence of the Raman gain needs to be characterized before this beam clean-up process can be accurately modeled. For pump and Stokes beams that are collinearly polarized, the angular dependence of the gain originates from the angular dependence of the linewidth. We have measured the linewidth of the Q(1) H2 Raman line for angles of 0-165° and densities of 1-25 amagats by fitting the profiles to Lorentzians, which provide good fits for these data. These measured linewidths are compared to empirical models; the most accurate model predicts linewidths to within 5% of our measurements for all angles and densities. We plan to make measurements with improved signal/noise to fit to Galatry profiles1 to directly extract the collisional narrowing contribution.
Dipole laser trap for neutral atoms
Authors: Gould P. L. , Migdall A. L. , Metcalf H. J. , Phillips W. D.
Published: February 2023

We describe a relatively large volume dipole laser trap for the confinement of sodium atoms. Two counterpropagating beams, tuned below resonance, with foci separated by approximately one con focal parameter, provide radial confinement via the dipole force and axial confinement by balancing the radiation pressures of the two beams.1 Identical circular polarization for both beams prevents optical pumping and serves to maintain a two-state system. Alternation of the two beams2 is necessary to avoid the effects of standing-wave heating. Additionally, the trapping cycle is alternated with a Doppler cooling cycle2 to achieve low temperatures and long confinement times. Trapping beams of 100 mW focused to 50-μm spot radii and detuned ~2 GHz below the F = 2 to F′= 3 transition of the D2 line provide a well depth of 50 mK and a confinement volume of 10-4 cm3. Analysis of atomic motion and escape mechanisms as well as progress toward the experimental realization of this trap is presented.
Radiative trapping effects in ruby: 77 K to 300 K
Authors: Birnbaum Milton , Fincher Curtis L. , Machan Jason , Bass Michael
Published: February 2023

The fluorescent decay of the 2
E
level of the Cr3+ over the range of 77 K to 300 K has been studied in experimental arrangements pro viding strong trapping of the O-phonon lines. At 300 K, rubies as large as 2.5 cm diameter by 28 cm length were used, packed in highly reflective BaSO4 powder to provide adequate trapping of the O-phonon fluorescence. The measurements resulted in the explicit determination of the lifetime vibronic transitions and the O-phonon decay rate.
Spectroscopy of solid hydrogen using optoacoustic techniques
Authors: Patel C. K. N.
Published: February 2023

Optoacoustic spectroscopy has many advantages in the study of weakly absorbing gases, liquids, and solids. However, to date this capability has not been exploited for obtaining new spectroscopic information on interesting liquids and solids. In this paper I shall review the application of optoacoustic spectroscopy to cryogenic liquids and solids. Among the cryogenic liquid studies, overtone absorption spectra of liquid methane and ethane and those of solid hydrogens (H2, D2, and HD) are described in detail because of their importance to scientific understanding as well as to understanding of optical astronomical data of outer giant planets such as Jupiter, Uranus, and Neptune. In solid parahydrogen, I report the first observation of the fourth vibrational overtone (Δv = 5) in the 19,000-cm-1 region. Further, I describe the measurements of lifetimes of vibrational levels of solid hydrogen. These lifetimes are anomalously short for homonuclear diatomic molecules and provide a risk data for theoretical physics. I conclude by providing a view into the other profitable areas that can be explored through the study of weak absorption spectra.
Characteristics of the gain in higher harmonic operation of a tree-electron laser
Authors: Fu Ensheng
Published: February 2023

In a storage ring free-electron laser we find that using higher harmonic operation, we can not only obtain a shorter wavelength, but also get more gain than when using fundamental harmonic operation at the same wavelength, when the wiggler parameter k ≥ 2. We also find that the experimental condition of the higher harmonic operationcan be easily realized.
Design of an All-Spherical, Three-Mirror, Off-Axis Telescope Objective
Authors: Cotton C. T.
Published: February 2023

Presented is the design of an all-spherical, unobstructed, reflective telescope for use as an end-of-chain alignment sensor package.
Compact Unobscured Four-Mirror Optical System
Authors: Rodgers J. Michael
Published: February 2023

This paper describes a four-mirror optical configuration with focal and afocal embodiments, folded into a compact envelope appropriate for pod-mounted and zoom applications.
Analog of Third-Order Methods in the Design of Asymmetric Systems
Authors: Stone Bryan D.
Published: February 2023

The consideration of third-order properties forms the foundation of methods for designing symmetric systems. An analog is discussed in the context of asymmetric systems.
Thermal Soak Analysis Based on a Single Element Method
Authors: Finkler Rami , Weiser Ronny
Published: February 2023

A simplified 2-D mesh provides the basis for analysis of thermal soak effects on optical systems. This principle is illustrated using a single lens system.
Symbolic Algebra and Eikonal Theory
Authors: Walther A.
Published: February 2023

Using symbolic algebra software to deal with the complexities of eikonal aberration theory provides simple straightforward solutions to previously intractable problems.
New Principles of Synthesis and Optimization of Optical Systems Using a Computer
Authors: Bezdidko Sergey Nikolaevich
Published: February 2023

The progress of optical system design using a computer has been developed basically in the direction of increasing the possibilities of the software for ray tracing through various types of optical surfaces and elements which form multi-configuration optical systems. Such software helped to fulfil calculation of geometric and diffraction characteristics of the image quality, to develop optimization methods used for reducing aberrations of separate rays and different characteristics of optical systems to the desired values. They permitted to expand service functions for graphic representation of the results of calculation and for interaction of a designer with a computer. No doubt the available software for optical system design is a great achievement of applied optics. The software gives a designer an instrument of the highest capacity for designing complex optical systems. This notwithstanding a subjective role of a designer shouldn't be eliminated by any means. The design of optical systems still remains in many respects a kind of “an art” depending on a designer, and it isn't “an applied science” which strictly and unambiguously algorythmizes the process of designing. As we know from the original sources there's no formalized approach to the synthesis of an initial optical system in the majority of software. On the base of specification requirements such synthesis makes possible to found the constructive parameters of the initial optical system suitable for further optimization and analysis. It's assumed that the said initial optical system is already existing or a designer is somehow creating it independently. On the other hand the optimization programs possess the substantial local limitedness caused by multi-extremeness of the minimized merit function, and in the majority of cases optimization doesn't bring to the acceptable solution. This fact substantially reduces efficiency of using such programs. In accordance with the foregoing the author’s researches were directed to the more complete formalization of the process of optical system design, to the decrease of subjective, heuristic stages and to transformation of “the art” of design into “the science” of design. In the present paper I'll briefly expound theoretical approaches of an initial optical system synthesis and pseudo-global optimization. The suggested methods are founded on the base of development of analytical theory of aberrations of the third order, expansion of aberration functions in terms of the orthogonal Zernike's polynomials and on the base of using the specifically determined physical criteria of rationality of optical system construction.
Designing with Gaussian Beams
Authors: Noethen Mark
Published: February 2023

Using macro-based optimization capabilities of commercially available lens design software, one can optimize directly on laser beam waist parameters. This, along with multiconfiguration capability, allows multiple sources and anamorphic systems in a single lens file even though the Gaussian beam ray trace uses paraxial rays in only the YZ plane.