bluuebunny/crossref_metadata_2025 huggingface dataset:
Soft X-ray Emission Excited by Electron Beams in a Superlattice
Authors: Kaplan A. E. , Datta S.
Published: February 2023

Fast moving electrons emit FM waves when passing through a spatially periodic medium (resonant transition radiation).1,2 The wavelength λ of the radiation emitted at an angle θ with respect to the electron trajectory is determined by the formula

n
¯

(
λ
)
cos
θ
=

β

−
1

−
r
λ
/
ℓ

, where β = v/c is dimensionless speed at the electron,

n
¯

(
λ
)

is averaged refractive index of the system, r is an integer, and ℓ is the period of spatial modulation. It is conventionally assumed that ultra-relativistic beams (e.g., up to 50 GeV3) are required to attain this kind of emission. We show4 that if the period ℓ is much shorter than a “mean” plasma wavelength of the medium λp, (which can be done by using solid-state superlattices with the spatial period 50–200Å), the critical kinetic energy required to get a radiation, turns out to be extremely low. One can show that when parameter Q = rλp/ℓ ≫ 1, this energy is (eU)cr ≃ mc2/2Q2, which is less than 10 KeV for all conventional materials if ℓ ≃ 100 Å. One can get a significant radiation in the range 10Å–300Å using non-relativistic beams with energies 70–300 KeV. The spontaneous radiation from the system has a conical structure with the emission wavelength changing with angle.
Electroluminescence due to allowed 5d-4f transition of Ce3 + in a ZnS thin film
Authors: Tanaka S. , Kobayashi H. , Shiiki M. , Kunou T. , Shanker V. , Sasakura H.
Published: February 2023

Mn2+ ions and rare-earth ions (Ln3+) such as Tb3 + ions are most commonly used as luminescent centers in ZnS thin film electroluminescence (EL) devices.1) Luminescence of Mn2+ and that of Ln3 + ions are due to parity-forbidden (d-d) and (f-f) transitions, respectively. We report here, a greenish-white EL due to parity-allowed 5d-4f transition of Ce3+ ions in a double insulated ZnS:CeF3 thin film device, for the first time.
Photoluminescent and Electroluminescent Properties of Cd0.95Mn0.05Se Electrodes
Authors: Burk A. A. , Ellis Arthur B. , Ridgley Dana , Wold Aaron
Published: February 2023

Single-crystal samples of n-type Cd0.95Mn0.05Se, grown a modified Bridgman method1, have been used as electrodes in photoelectrochemical cells (PEC’s) employing aqueous diselenide electrolyte. After etching with HCl/HNO3 (1:1 v/v), the samples exhibit photoluminescence (PL) when excited with ultraband gap excitation (Eg~1.75 eV2); the maximum of the PL band, ~690 nm, is near the band gap energy and blue shifts to ~680 nm at 77 K. In some samples, subband gap PL is also observed (uncorrected λmax~890 nm.) The radiative efficiency, ϕr, of the edge emission can be as large as ~10-4 at 295 K and ~10-2 at 77 K.
Nonlinearities in the Mn2+ System Saturating the Electroluminescence of ZnS Thin Film Devices
Authors: Mach R. , Müller G. O.
Published: February 2023

The very high brightness, very good contrast and high efficiency of Inoguchi /1/ type electroluminescence devices (ELD) have boosted the interest in the mostly used emitter system - Mn2+ in ZnS. The highest brightness levels achieved - some 5000 ftL - are below the ones expected from crude estimates and several investigators found saturation of brightness upon drive /2,3/.
Holeburning and Optically Detected Nuclear Magnetic Resonance in CaSO4:Eu3+
Authors: Manson Neil B. , Silversmith Ann J.
Published: February 2023

We have studied two Eu3+ sites in CaSO4 by selective excitation, emission, optical holeburning and optically detected nuclear magnetic resonance (ODNMR) techniques. Both centres (henceforth referred to as 1 and 2) have 7F0 → 5D0 excitation signals at ~578.7nm; the two absorptions are 34GHz apart. The emission and excitation spectra of the two centres are very similar, and indicate that low symmetry sites are involved.
Laser Excitation and Spin Coherence of Phosphorescent F 2 2 + Centers in CaO.
Authors: Glasbeek M. , Casalboni M. , Vreeker R.
Published: February 2023

In recent years, extensive spectroscopic studies concerning F-type point defects in additively colored alkaline earth oxides have been reported. In particular, oxygen vacancies containing two electrons are of interest because they can be photo-excited into phosphorescent triplet states. Several experimental techniques have been applied for studying such triplet states including optical-microwave double resonance and spin coherence techniques [1]. In this paper, we report on a spin coherence study of the phosphorescent triplet state of the

F
2

2
+

center in CaO, the triplet state being prepared by excitation with cw- and pulsed-dye laser light.
Hyperfine Spectroscopy and Spin Dynamics by Optical and Sublevel Coherence
Authors: Shelby R. M. , Macfarlane R. M.
Published: February 2023

It has been well established that for many metastable electronic levels of impurity ions in insulators, optical coherence times at liquid helium temperatures are limited by magnetic interactions with host nuclear spins.
1
To understand coherence loss in detail, one needs measurements of optical and spin dephasing, magnetic properties and hyperfine structure of impurity ions, and spin dynamics of host nuclei. To this end techniques such as spectral hole burning,
2
coherent transients (e.g. photon echo),
1,3
and optical-rf double resonance
4
have been used. All of these are limited directly or indirectly by optical T2, and have not directly probed the dynamics of host nuclei.
Investigation of Excited State Dynamics in Condensed Phases Using Picosecond Nonlinear Techniques
Authors: Fayer Michael D.
Published: February 2023

Excitation transport and excited state dynamics are investigated in ordered and disordered systems using picosecond nonlinear techniques and detailed statistical mechanical treatments. Transient holographic grating measurements on anthracene single crystals provide the first direct measurements of singlet exciton transport (1). The initial results measure the rate of transport and suggest transport is quasicoherent.
Exciton Migration and Capture in a Linear Chain Manganese Salt
Authors: McPherson Gary L. , Auerbach Roy A. , Kwawer Gary N. , Talluto Katherine F.
Published: February 2023

Like a number of AMX3 salts, CsMnBr3 adopts the lexagonal CsNiCl3 structure which consists of infinite linear chains of MX64- octahedra sharing opposite faces. The physical properties of many of the linear chain AMX3 salts have attracted considerable attention because of the one-dimensional character of the structure. Yamamoto, McClure, Marzzacco and Walderman observed that the luminescence of (CH3)4NMnCl3 is quenched by the presence of transition metal impurities. (Yamamoto et al., 1977). The temperature and concentration dependence of the luminescence quenching indicated that the exciton migration is thermally activated and restricted to the linear chains (one-dimensional). Subsequently it was shown that trivalent rare-earth ions such as Nd3+, Er3+ and Tm3+ could be introduced into crystals of CsMnBr3 and that these ions behaved as radiative traps for the manganese excitons. (McPherson and Francis, 1978, McPherson et al., 1979).
The Oscillator Strength of Interstitial Fe4+ in α-Quartz
Authors: Cohen Alvin J.
Published: February 2023

While α-quartz is trigonal, optically (+), the biaxial spectra of interstitial Fe4+ appears to have orthorhombic symmetry with oscillator strength, f, equal 0.011 for E in π and σ and for normal light in a wafer cut in

(

1

1
¯

00

)

. In a wafer cut in (0001), f is 0.011 with E║ a and 0.0065 with E ⊥ a. In normal light in the a-plane f is 0.0084 (while the vectorial average is 0.0087). Evidence is presented that Fe4+ can only be interstitial and only appear in major rhombohedral, r, growth in α-quartz, as the mechanism of its production requires the presence of potential trapped-hole centers which are quenched by the electron donor role of interstitial Fe3+.
Spectral band assignments for Cu+ and Ag+ in alkali halides via two-photon spectroscopy
Authors: McClure Donald S. , Pedrini Christian
Published: February 2023

The absorption spectra of Cu+ and Ag+ in alkali halide crystals have been studied for some time by way of ordinary absorption and emission spectroscopy.1 It has been established that the near ultraviolet transitions are due to 3d10→3d94s for Cu+ and 4d10→4d95s for Ag+, and that these occur at considerably higher energies (1-2 eV) in the crystal than in the free ion. A detailed understanding of the band shapes and their assignment to specified transitions had not been achieved, however.
Study on the Energy Transfer Process of Tb3+, Ce3+ Ions Doped Phosphate Glasses
Authors: Changhong Qi , Fuxi Gan
Published: February 2023

We have systematically studied the spectral properties of Ce3+, Tb3+ ions in different glass hosts[1]. In this paper the concentration effect and energy transfer process between Tb3+ and Ce3+ ions were reported. A series of glasses with the following doping concentration were prepared. (1) Tb3+ — 2, 4, 8, 12, 16 wt%. (2) Ce3+ — 1, 3, 5 wt%, 17 mol%. (3) 8 wt% Tb, Ce3+ — 1, 3, 5 wt% The emission and excitation spectra of these glasses were obtained using Hitachi Model 650-60 fluorescence spectrophotometer. Decay times of the 5D4 - 7F5 transition (542nm, 548nm) at the different Tb3+ concentrations were measured using an KrF excimer laser with pulse duration 10ns as the exciting light source.
Pressure Effects of Fluorescent R-Lines of Chrysoberyl BeAl2O4:Cr3+
Authors: Jia W. , Shang Y. , Tang R. , Yao Zh.
Published: February 2023

The behavior of fluorescent R-lines of chrysoberyl BeAl2O4:Cr3+(0.1%atm) has been investigated under hydrostatic pressures upto 68 kbar at room temperature. It was found that R1 and R2 lines were linearly shifted to the red, in contrast to the ruby system, with different rates of 0.62 and 0.71 cm–1/kbar respectively, as a result, R1 and R2 lines gradually approach to each other with pressure. The line width s of R1 and R2 were narrowed, and the lifetimes were lengthened from 0.5 ms (R1, R2) at normal pressure to 3.5 ms (R1) and 3.0 ms (R2) at 68 kbar. Time resolution spectra of the fluorescent band have been measured. It was found that the background of fluorescent phonon band was blue shifted and was suppressed with pressure.
Optical Properties of LiGa5O8:Mn
Authors: Abritta T. , De Souza Barros F. , Vugman N.V. , Melamed N. T.
Published: February 2023

Luminescence and EPR measurements were done on single crystals of LiGa5O8 having nominal Mn concentrations of 0.4, 1.0, and 10wt%. These crystals were grown by the flux method and supplied by Deltronic Crystals Industries, Inc.‡ The dominant fluorescent signal is due to the B-site Mn4+ ions. At 10K the emission is characterized by a sharp zero-phonon line at 721.6nm due to the 2E(G)→4A2(F) transition. This fluorescence has a decay time of 450µs, and its lower-energy side bands have a very rich structure. For the more concentrated Mn samples the intensity behaviour of some of these side bands indicates the presence of pair lines. The comparison between the observed luminescence properties of Mn4+ with those of its isoelectronic Cr3+ in the same compound(1) shows that the Mn4+ zero-phonon line and its vibronics are shifted to lower energies, and that the 4T2 excitation bands are shifted to higher energies, giving rise to a Dq value of 2000cm-1. These trends are due to the fact that both covalence and crystal field parameters must have larger values with the increase of central ionic charge. The 4T1 excitation band of Mn4+ is hidden at the tail of a charge transfer band shifted towards longer wavelengths. Assuming the relation C=4B for these Racah parameters one has for Mn4+ a B value of 660cm-1 and a C value of about 2640cm-1. Similar results for Mn4+ and Cr3+ emissions were obtained in the isomorphous compound LiAl5O8(2).
Renewing Investigation of Luminescence Spectrum of Manganese Ion Doped in Cadmium Chloride
Authors: Shang-ta Hsia , Shao-jiang Chen
Published: February 2023

We have made a new assignment of spectrum of CdCl2:Mn++ which had been published by B.Ghosh et.al.(1). The main points which are different from theirs are as following: 1). There have been some evidences of 1)3d distortion in this spectrum. 2). The six peaks between 26660 cm-1 and 27390 cm-1 have been assigned as phonon sideband which is based on the D3d and spin-orbit splitting of 4T1 (D). Because of Cd++ and Cl- have no magnetic momentums and the concentration of Mn++ is very low. They should not look as exciton-magneton-phonon sideband. 3). The sharp peaks at 23670 cm-1 and 23360 cm-1 have been regard as a result of No-phonon magnetic transition 6A1→4E(G) and 6A1→4A1 (G) (4E-4A1 degeneration is removed by HD3d). Because of the diagonal martrix elements of HSL in 4E(G) equal zero, the previous assignment in which both of them have been due to 4E(G) is unlike to us. Moreover, the peak at 23980 cm-1 has been indentified as One-phonon sideband of the transition 6A1→6A1 (G)(2). 4) . The electrical dipole transition ought to be assisted by phonons for the parity conservation. In oar fitting computation the phonon spectra of CdCl2 and MnCl2 have been consulted (3)(4) and included.
Thermal Zero-phonon Line Widths of Impurities in Crystals: Theory and Experiment
Authors: Hsu D. , Skinner J. L.
Published: February 2023

We examine the problem of the absorption zero-phonon line shape for dilute impurities in crystals. We consider the usual two-level electronic model, where both the ground and excited state Born-Oppenheimer surfaces are harmonic in the phonon coordinates. The difference between the two surfaces (the electron-phonon interaction) has terms which are both linear and quadratic in the phonon coordinates. In contrast to the usual perturbative theories,1 we calculate the zero-phonon line width to all orders in the electron-phonon interaction. We find that only the quadratic term is responsible for line broadening, and that at T=0°K this contribution vanishes. Our results are presented as integrals, which can be performed analytically or numerically, involving the weighted phonon density of states. We also show that within the model, the zero-phonon lines in the absorption and fluorescence spectra coincide exactly for all temperatures. Our results resolve the theoretical controversy produced by the two previous attempts to solve the line shape problem for strongly coupled electron-phonon systems. The work by Osad'ko2 is shown to be correct.
Optical Dephasing of Impurities in Amorphous Organic Solids down to 0.3 K.
Authors: Völker Silvia , Thijssen H.P.H. , van den Berg R.
Published: February 2023

Photochemical hole-burning has been used to measure the temperature dependence (between 0.3 and 20 K) of homogeneous linewidths (Γhom) of 0-0 S1 ← s
0
transitions of a variety of organic molecules in alcoholic glasses and polymers [1]. It was found that Γhom obeys a T1.3±0.1 law independent of the system studied. The results suggest that the guest only acts as a sensor to probe low-temperature relaxation processes in the amorphous state. Furthermore, it was observed for the first time that some of the organic glassy systems reach the lifetime-limited value of a few MHz at T ⩾ 0.3 K, which implies a very weak coupling between impurity and amorphous host. In all systems Γhom extrapolates to the T1- limited value for T → 0. In addition, a cross-over from a T1.3 to a linear power-law occurs in systems where Γhom ≲ 60 MHz, at a temperature which depends on the structure of the glass. This structure also determines the magnitude of Γhom: stiff alcoholic networks with a high degree of hydrogen bonding or linear polymer chains with no side chain groups (and, presumably, a high degree of short range order) yield very narrow linewidths of the same magnitude as in crystalline solids. This is in contrast to previous results in organic and inorganic glasses where differences of two to three orders of magnitude have been reported between amorphous and crystalline solids. From these results it appears that hole-burning can be used as a sensitive technique to study slow motions of polymer side chain groups at low temperatures.
Scattering and trapping of photo-excited triplet excitons in one-dimensional molecular crystals.
Authors: Schmidt J.
Published: February 2023

In the last few years it has been possible to obtain detailed information about scattering and trapping of photo-excited triplet excitons in the molecular crystal of 1, 2, 4, 5 - tetrachlorobenzene (TCB). The attraction of TCB is that the intermolecular interaction in good approximation is one-dimensional which makes it a prototype for investigating the properties of tightly bound excitons [1].
Nonlinear Optical Properties of Fluorescein in Glass
Authors: Kramer M. A. , Krasinski J. , Boyd R. W.
Published: February 2023

There is much interest in materials displaying a small saturation intensity for use in four-wave mixing and optical bistability. In this paper we report on one such material comprised of fluorescein dye molecules imbedded in a matrix of boric acid glass. This material shows a luminescence decay time of about 2 sec and hence an extremely small saturation intensity which we have measured to be about 10 mW/cm2. We have found that four-wave mixing can easily be observed at intensities of 10 mW/cm2.
The Optically Detected Stimulated Spin Echo as a Probe of Triplet Energy Migration in Mixed Molecular Crystals
Authors: Brenner Henry C. , Janes Stephen M.
Published: February 2023

We report the first application of optically detected stimulated echoes to the measurement of trap to trap migration rates in mixed molecular crystals. The stimulated echo (1) can be thought of as a 2-pulse echo in which the 180° refocussing pulse is split into two 90° pulses. This has the effect of storing local field information along the longitudinal or population difference axis in the rotating frame. This information is then "read-out" in the form of an echo by the third 90° pulse. Since the ability to recall or "stimulate" the echo at the later time depends on how well the local field alignment is preserved during the long waiting time T, the stimulated echo intensity reflects changes in local fields and can be used to probe trap to trap energy migration.
Spectral Narrowing of Excitation Spectra in N-Photons Up-Conversion Processes by Energy Transfers
Authors: Auzel F.
Published: February 2023

By using a CW tunable F-center laser emitting between 1.4 and 1.6μ, room temperature excitations for 1 to 5 photons APTE effect (Addition de photon par transfert d'énergie [1]) are obtained for Er3+ doped vitroceramics. Theses materials, higly doped with R.E (1 to 15 %), have been shown to be very efficient medium for such up-conversion process because though in a glassy form they behave as doped microcrystals [2].
Optical Generation and Detection of Near-Zone-Boundary Phonons in Ruby
Authors: Goossens R.J.G. , Dijkhuis J.I. , de Wijn H.W.
Published: February 2023

Optically pumped luminescent centers are now widely used as generators and detectors of high-frequency phonons in crystals. Monochromatic phonon generation and detection with such centers have for the first time been demonstrated in ruby by observing the R1 and R2 fluorescent intensities as a function of the pumping power and a magnetic field.1 The optical techniques have made high-frequency phonons accessible to experiment, thus allowing important new information to be obtained. Here we present a new scheme of optical phonon spectroscopy which is inherently selective for near-zone-boundary phonons. As for the detection, the scheme employs, instead of a direct phonon-associated transition, second-order Raman transitions connecting two luminescent states. As an example we consider the case of ruby.
Nonlinear Dynamics for a Semiconductor Laser with Optical Feedback
Authors: Olesen H. , Osmundsen J.H. , Tromborg B.
Published: February 2023

The optical feedback from an external cavity may force a semiconductor laser to oscillate in a single mode with very narrow linewidth. However, above a certain critical level of feedback the laser may switch to a seemingly chaotic state in which the linewidth is increased by several orders of magnitude. We report on a theoretical study of this transition by computer simulation of the coupled rate equations for the complex electric field β(t) exp(jωot) and the carrier density N(t).
The Role of Transiency in the Formation of Solitons in Stimulated Raman Scattering
Authors: Carlsten J.L. , MacPherson D.C.
Published: February 2023

Recently there has been considerable interest in the formation of solitons in three level systems,1 such as in Raman scattering.2-5 Solitons in stimulated Raman scattering were first predicted by Chu and Scott,6 but their experimental realization seemed remote because of the apparent necessity for particular pulse shapes for the polarization and fields. It is now clear that solitons do indeed form7 in SRS and that transiency plays a major role in their formation.
Solitons in Four-Wave Mixing
Authors: Ackerhalt Jay R.
Published: February 2023

We have extended the work of Kai Druhl, Bob Wenzel and John Carlsten1 on solitons in stimulated Raman scattering to include four-wave mixing phenomena. We have studied coherent anti-Stokes Raman scattering (CARS) and second Stokes generation (SSG). We have found that CARS exhibits a soliton-like structure, whereas SSG exhibits a real soliton. Analytic solitons have been used to verify our interpretation of the numerical results.
Instabilities and Chaos in Multimode Homogeneously Broadened Lasers
Authors: Milonni P.W. , Shih Mei-Li
Published: February 2023

The experiments of Hillman, et al. [1] with a ring dye laser indicate that single-mode homogeneously broadened oscillation is intrinsically unstable at high pumping levels. Motivated by this work, we have considered various formulations of the general multimode problem. We find that certain aspects of these experiments, such as the transition from single to multimode oscillation with increased pumping, can be understood within the thin-sheet gain model in which spatial hole burning is completely ignored. (We hope by the time of our presentation to be more precise about the comparison of theory and experiment.) Following the bifurcation of the single-mode steady state and the onset of two modes symmetrically displaced about line center, there is a period-doubling route to chaos which is not evident in the experiments thus far. The familiar "gain clamping" assumption of single-mode oscillation in a homogeneously broadened laser is incorrect at high pumping levels, even in the absence of spatial hole burning. Our results appear to be consistent with the arguments advanced by Hillman, et al. on the basis of a model in which the atoms are driven by the field but do not react back on it.
Nonlinear Mixing and Multi photon Processes in the Field of Two Pumps
Authors: Agarwal G.S. , Nayak N.
Published: February 2023

A very large number of physical phenomena in the resonant interaction of atomic-molecular systems with the radiation fields can be studied by treating the atomic system as a two level system and by examining its response to the applied fields. Various perturbative results are well known. A number of recent experimental works require the knowledge of the nonperturbative response functions, when both the applied fields are strong. These include a variety of experiments on instabilities(1) in lasers involving the switching from a single mode to for example two mode operation. Similarly recent nonlinear mixing experiments, where not only four wave mixing but also higher mixing in saturating fields has been studied. Pump probe experiments have also been repeated with probes whose intensity could be large. The purpose of this paper is to formulate the general theory and use it to understand the experiments. The formulation we present is also well suited for studying the effect of collisions. Details of various collisional induced coherences in fourwave and six wave mixing etc. can be studied.
Unstable modes of an inhomogeneously broadened multimode ring laser
Authors: Mandel Paul
Published: February 2023

We study the domain of unstable modes α for a unidirectional multimode ring laser. The inhomogeneous broadening is characterized by a Lorentz distribution of width u (expressed in units of the homogeneous width). A linear stability analysis of the single mode solution yields the following results.
Statistical Behavior of Mode Amplitude and Phases in Multimode Dye Lasers
Authors: Raymer Michael G. , Westling L. A.
Published: February 2023

In order to characterize the statistical properties of multimode dye laser light, we have made two types of measurements: 1) mode intensity cross-correlation measurements, and 2) total intensity autocorrelation measurements. The two measurements contain different information. The cross-correlation measurements, made on a pulsed dye laser are detailed in Ref. 1. Briefly, the conclusion of these measurements was that certain pairs of modes are likely to lase simultaneously (coexist) because they don’t strongly compete for gain in the same spatial regions of the dye medium. The cross-correlation measurements gave information only about the amplitudes (intensities) of the modes, and not their phases.
Instabilities Associated with Hopf Bifurcations in Semiconductor Lasers
Authors: Shore K.A. , Rozzi T.E.
Published: February 2023

The stabilility properties of oscillations arising at Hopf bifurcations in semiconductor lasers have been analysed. Numerical examples utilising typical GaAs laser parameters show that both unstable and stable oscillations may occur.
Quantum Theory of Double Sidemode Instabilities
Authors: Holm David A. , Sargent Murray
Published: February 2023

In a recent paper1, a quantum theory of multiwave interactions with a two-level medium is presented. In this paper we apply this theory to sidemode instabilities pertinent to cavity con figurations in optical bistability and ring lasers. We assume the cavity to oscillate on a single mode, and we evaluate the gain and spontaneous emission at other frequencies. Because of the saturating presence of the strong, laser mode, two symmetrically situated sidemodes can grow together, inducing populations pulsations that influence the other sidemode. The instability must therefore be treated as a double sidemode problem.
Bistable Two-Mode Lasers and Most Probable Tunneling Paths.
Authors: Wang X.W. , Lin D.L. , Hioe F.T.
Published: February 2023

Bistability is a problem of considerable interest in many fields of physics.1 The problem generally involves mode competition through nonlinear dynamics, quantum and classical fluctuations, and probability of "tunneling" from one metastable state to another.2-4 When the modemode coupling is an adjustable parameter as in the case of recent experiments involving a free running broad band, standing-wave cw dye laser,5 the transition from a many-mode to a two-mode operation has the characteristic of a thermodynamic phase transition at a certain critical point.4
Dynamic Correlations in Optical Systems with Parametric Noise
Authors: Miguel M. San , Hernández-Machado A.
Published: February 2023

It has been suggested that anomalous fluctuation phenomena found experimentally in dye lasers(1) can be due to fluctuations of the pump parameter. The schochastic dynamical model proposed is In appropriate units I is the intensity of the laser field and ∝ is the mean value of the pump parameter. The stochastic force ξ (t) models fluctuations of ∝. Away from the immediate vecinity of the instability point, ξ (t) can not be modeled by a white noise. We take for ξ (t) and Ornstein-Uhlenbeck noise with correlation <ξ (t) ξ (t')> = z-1 exp (-|t-t'|/z). We present here a calculation of the short time behavior of the normalized steady state correlation function

λ

 

s

 
=
 

<

I

 

s

 

I

 

o

>

s
t

−
<

I

>

st

2

 
/
 
<

I

>

st

2
Single and Multimode Instabilities in Lasers
Authors: Risken H.
Published: February 2023

The nonlinear laser equations [1-3] lead to various types of instabilities. The type of the instability mainly changes with the change of the pump parameter.
Experimental Developments in Single- and Multi-Mode Laser Instabilities
Authors: Abraham Neal B.
Published: February 2023

Pulsations have been observed since the earliest days of maser and laser systems. General classifications will be described which provide a framework for understanding previous experimental results and recent studies. A good set of references following this classification scheme can be found in the introduction to the recent special issue of the Journal of the Optical Society of America B in January 1985 on Instabilities in Active Optical Media1.
Recent Progress in Modelling Single Model Laser Instabilities
Authors: Casperson Lee W.
Published: February 2023

The topic of laser instabilities is one of the oldest subjects in laser research. Even before the first laser had been built, it had been demonstrated in 1958 that a simple semiclassical maser model could possess an intrinsic instability.1 A surge of interest in laser instability modelling followed the discovery that ruby lasers routinely produce their outputs in the form of infinite trains of short pulsations or "spikes".2 Since those earliest experiments, a wealth of data has been accumulated on ruby and the dozens of other laser systems that sometimes, for no apparent reason, emit infinite pulse trains. There has also been much effort expended on developing theoretical models which might account for the experimental observations, and in recent years such modelling efforts have been increasingly successful. The purpose of this presentation is to provide an overview of laser instability modelling with an emphasis on recent developments. At the outset, the various possible approaches to this subject will be briefly surveyed.
Single-mode Laser Instability Induced by Phase Perturbations
Authors: Englund John C.
Published: February 2023

I have recently discovered that phase perturbations may destabilize the steady-state operation of gas lasers described by a single, standing- wave mode in resonance with a tuned cavity. The threshold of this instability may lie above or below that arising from amplitude perturbations1,2; furthermore, it coincides with a bifurcation of the steady-state field intensity ℐ and frequency ν. Neither the instability nor the bifurcation is experienced by running-wave modes.
Routes to Chaos in Passive All Optical Resonators Containing Molecular Gases
Authors: Harrison R.G. , Firth W.J. , Al-Saidi I.A. , Cummins E.
Published: February 2023

There has been considerable interest over the last few years in transitions to chaos in passive optically bistable systems. Ikeda1 showed in 1979 that an optically bistable ring resonator containing the simplest of nonlinear systems, a two-level media, can show a period doubling route to chaos. This was demonstrated by us2 using NH3 gas near resonantly pumped by pulsed CO2 laser radiation. More generally we identified and demonstrated the unique advantages of molecular gases in this field, providing in particular a vast range of laser-molecular coincidences together with control of response time, and therefore switching time and modulation frequency, by varying gas pressure. Subsequent extension of this work to all optical Fabry-Perot resonators revealed huge oscillatory effects3 leading to chaos in the transmitted laser signal. Under other parameter conditions for both NH3 and SF6 a rich variety of optically bistable effects were observed obtained in systems as small as 1 mm for SF64,5.
Instabilities in Quanium Optical Systems with a Modulated Feedback
Authors: Tredicce J. , Delfino G. , Meucci R.
Published: February 2023

During the last years, different hybrid bistable systems have been proposed (1,2) and have been used as a test bench for chaotic approach problems (3,4,5). In such systems the necessary condition in order to reach a turbolent behaviour is that the delay time (τ) in the feedback is greater than the response time of the system itself (tR).
Approximation of Time-Delay Differential Equations by Ordinary Ones
Authors: Bel L.
Published: February 2023

Let us consider a time-delay differential equation of the following type:

where G is a tuning constant, and where

x
^

i

are p time-delayed values of the variable x, the ri being functionals of x(t).
Theory of a Laser with an Inhomogeneously Broadened Saturable Absorber*
Authors: Roy Rajarshi , Singh Surendra
Published: February 2023

Many quantum optical systems exhibit first-order phase transition analogy.1 Fluctuations of the optical field in such systems are due to spontaneous emission noise. The nature of these fluctuations for various systems has been discussed using various approaches. Fully quantum mechanical and Langevin equation treatments have been given for the dye laser2,3 and the laser with a saturable absorber (LSA) with homogeneously broadened media.2,4 For inhomogeneously broadened media, such treatments are either valid for low intensities or do not fully take into account the effect of quantum noise.5 In this contribution we present a fully quantum mechanical treatment for the LSA with an inhomogeneously broadened absorber using the Foch state representation of the density matrix.2,6
CW AlGaAs Injection Heterostructure Laser with Second-Order Distributed Bragg Reflectors
Authors: Alferov Zh. I. , Gurevich S.A. , Mizerov M.N. , Portnoy E.L. , Ioffe A.F.
Published: February 2023

Room-temperature generation in injection heterostructure lasers with distributed Bragg reflectors (DBR) was achieved in some laboratories about two years ago [1-3]. The minimum threshold current was observed in lasers of a complicated structure with an active layer taper coupled to a more wide-gap layer with a Bragg reflector [1]. However, the threshold current remained too high for obtaining CW operation. Simplier structures of DBR heterolasers [2-4], in which the passive waveguide layer with Bragg reflectors is directly connected with the active layer, showed much worse characteristics. Recently in this DBR laser construction we have reduced the room-temperature threshold current density down to about 3 kA/cm2 [5], which makes the obtaining of CW operation much easier. These results are determined by a broadening of the optical cavity and, therefore, by a decrease in the passive region absorption*. The present talk concerns our method of preparation and certain characteristics of CW DBR heterolasers.
Electrooptic Phased-Array Light Beam Deflector with Application to Analog-to-Digital Conversion*
Authors: Saunier P. , Tsai C.S. , Yao I.W. , Nguyen Le T.
Published: February 2023

An optical phased-array structure can be created by depositing an array of interdigital finger electrodes having a linear variation in apodization on the top of an electrooptically-active planar waveguide (Fig. 1).(1) As a result of the linear electrooptic effect and the apodized-electrode array structure, a differential optical phase delay is induced between the adjacent light beams (defined by the adjacent electrodes) when a voltage is applied across the two terminal electrodes. Since the apodization varies linearly across the aperture of the light beam, a linear phase slope is induced across the aperture of the light beam at the output port. Thus, by varying the applied voltage one can vary this induced phase slope to deflect/switch and modulate the light beam in the plane of the waveguide. A model calculation for such an electrooptic phased-array (EOPA) structure in a Y-cut LiNbO3 waveguide has predicted(1) a small drive voltage per resolvable beam position. For example, with a preliminary device using He-Ne laser light and an array with L = 1 cm and d/2 = 5μ the drive voltage per resolvable beam position was measured to be 6 volts.(1)
Curved Junction Stabilized Filament (CJSF) Double-Heterostructure Injection Laser
Authors: Figueroa Luis , Wang Shyh
Published: February 2023

In recent years there has been significant improvement in the properties of the GaAs injection laser. The most significant problems encountered have been the non-linear power-current behavior and the anamolous relaxation oscillations[1]. The essential mechanism in eliminating these characteristics is the control of the lateral modes of the laser. Here we report our work on a new structure with a curved active region which effectively controls the lateral modes of the laser and thus eliminates the problems associated with mode instability. With this laser we have been able to achieve under pulsed operation.
Stripe Guides of LiNbxTa1–xO3: Physical and Optical Characterization for Accurate Mode Control
Authors: Hammer J. M. , Phillips W. , Neil C. C.
Published: February 2023

One of the most interesting and useful features of metal-diffused waveguides is the relative ease with which three-dimensional waveguide structures can be fabricated by forming patterns on the metal before diffusion. A number of uses for these types of guides has been described in the literature (1,2,3). In this paper we will describe the fabrication and the physical properties of diffused LNT stripe guides, describe the propagation of light in these guides, and show the relationship between the observed light propagation characteristics and the physical properties. An important result of this study is that we now understand the relation between the physical and optical parameters and can use this understanding to fabricate stripe guides with any desired number of modes.
A New Technique for Waveguide Formation in LiNbO3
Authors: Chen Bor-Uei
Published: February 2023

The fabrication of active optical waveguides is one of the most important subjects for integrated optics. LiNbO3 and LiTaO3 are among the best available waveguide media for this application because of their excellent properties in electro-, acousto-optic interactions. Optical waveguides in LiNbO3 and LiTaO3 have been proposed and demonstrated using various techniques. The first LiNbO3 waveguide was formed by out-diffusion of Li2O so that the extraordinary index of refraction increased at the surface.1 Later, optical waveguides were also formed in LiNbO3 and/or LiTaO3 crystals by in-diffusion of transition metal ions,2 epitaxial growth by melting3 or by sputtering.4 The most promising and widely used method is the diffusion of Ti metal which provides single mode, low-loss (⪝1 dB/cm) waveguides. In addition, the photolithographic technology can be utilized to form sophisticated optical circuits. However, a major problem in waveguide formation by metal in-diffusion is that at high diffusion temperatures, Li2O escaped from the surface through the out-diffusion process. As a result, there is an unwanted planar waveguide in addition to the waveguides formed by metal in-diffusion. This paper reports a new technique of using organo-metallic solutions as diffusion sources to form single mode waveguides in LiNbO3. The preliminary experimental results showed that no Li2O out-diffusion waveguide was formed with this new diffusion process. The technique is expected to work equally well for LiTaO3 crystals.
Noise in Semiconductor Lasers
Authors: Melchior H.
Published: February 2023

Overview and implications of fluctuation phenomena in semiconductor lasers including quantum limits, extraneous sources and outside influences as well as flicker and as yet unexplained current noise.
Convolution of Picosecond Optical Pulses
Authors: Normandin R. , Stegeman G.I.
Published: February 2023

Various signal processing functions have been demonstrated in the past decade by the nonlinear mixing1 of oppositely propagating surface acoustic waves in piezoelectric media. One of the output signals occurs as bulk acoustic waves2 generated normal to the surface. Here we report the optical analog of this nonlinear acoustic interaction which utilizes nonlinear, planar integrated optics.
Overshoot Switching in Bistable Optical Devices
Authors: Goldstone J.A. , Garmire E. , Ho P.-T.
Published: February 2023

In this paper we show that it is possible for BOD's to switch at incident light levels considerably smaller than the critical incident signals predicted by steady state theory. This effect may be large when the device has two time constants of roughly equal value. The discovery of overshoot switching may have significant impact on BOD's as their speed increases and the feedback time constants become comparable to their internal time constants.
Semiconductor Injection Lasers for Long Wavelength Optical Communications
Authors: Nakamura Michiharu
Published: February 2023

The intense interest in fiber optic communications has been encouraging the development of long wavelength semiconductor lasers emitting at 1.1-1.6 μm1-3), where silica fibers have minimum loss and dispersion. In this paper, we describe the recent efforts on long wavelength lasers, which include the realization of various laser structures using the InGaAsP/InP system, reliability study, and modulation experiments.
Low Threshold Current Transverse-Junction Lasers on Semi-Insulating Substrates by Molecular Beam Epitaxy (MBE)
Authors: Lee T. P. , Burrus C. A. , Cho A. Y.
Published: February 2023

The first demonstration of the growth of GaAs-AlxGa1-xAs transverse-junction stripe (TJS) lasers on semi-insulating substrates was reported by Lee, Margalit and Yariv.(1,2) Lasers of this type are characterized by low thresholds and stable single-mode operation up to 110°C.(3) Recently, long life CW operation of TJS lasers has been demonstrated by Susaki et al.(4) These previous results were achieved using liquid phase epitaxy (LPE), with thresholds falling in the range of 30 to 40 mA. Molecular beam epitaxy (MBE) is a relatively new crystal growth technique which not only offers precise dimensional controls in the film growth direction, but also can achieve selective two-dimensional structures on the wafer surface. For example, monolithic integration of a laser and a waveguide with a tapered coupler has been demonstrated with MBE.(9) We report here the first preparation by MBE of low threshold, single mode TJS lasers grown on semi-insulating substrates. In conjunction with the two-dimensional selective growth capability of MBE, the results may have potential applications in the field of integrated optics.
Crystallographic and Electrooptic Properties of Cleaved LiNbO3
Authors: Kaminow I. P. , Turner E. H. , Barns R. L. , Bernstein J. L.
Published: February 2023

The predominant cleavage plane in LiNbO3 is known to be of the general (01.2) type.1 However, neither the absolute orientation of the plane with respect to the standard crystal x, y, z axes nor with respect to the lattice structure has been determined. Recent interest in the use of x-cut plates with cleaved end-faces for use in electrooptic devices2-4 has prompted us to establish the absolute orientation of the cleavage plane.
Losses in Diffused LiNbO3 Waveguides Caused by Directional Changes
Authors: Hutcheson L.D. , White Ian A. , Burke James J.
Published: February 2023

Many integrated optical circuits require directional changes of the optical waveguides to accommodate the design parameters of their individual elements. Bending losses of various configurations have been studied both experimentally1 and theoretically2,3. Results for two types of bends are presented in this paper; the first type is corner bends where two straight waveguides are joined together at some angle and the second type is smooth, curved bends having a constant radius of curvature. Experimental results on the optical transmission in titanium diffused LiNbO3 channel waveguides for both types of bends are presented and compared to new theoretical predictions, whose foundations will be reported elsewhere5.
Low Loss Zinc Oxide Optical Waveguides on Amorphous Substrates
Authors: Hickernell Fred S.
Published: February 2023

Zinc oxide is a most promising thin film material for use in integrated optical devices because of its high index of refraction, low optical loss, strong acousto-optical, electro-optical and nonlinear optical coefficients and its large piezoelectric constants. Optical losses less than 1 dB/cm have been reported for films grown by CVD on sapphire (1). Strong acousto-optic interactions have been observed (2) and electro-optic modulator and switching action demonstrated (3). To obtain a high optical quality zinc oxide it has been necessary to deposit the films on crystalline substrates such as sapphire. The low optical losses measured on crystalline substrates have now been achieved on amorphous substrates with ZnO films sputter deposited on oxidized silicon substrates. The optical waveguide propagation properties of these films are the subject of this paper. Films of this type have been used for SAW device development and possess piezoelectric and acoustic properties approaching single crystal zinc oxide (4).
Monolithic Integration of Optical and Electronic Devices on Semi-Insulating GaAs Substrates
Authors: Margalit S. , Bar-Chaim N. , Ury I. , Wilt D. , Yust M. , Yariv A.
Published: February 2023

The potential advantages of semiconductor-based integrated optics have been recognized for some time.1 This is because, in a semiconductor such as GaAs for example, one can fabricate both optical devices such as detectors, LEDs, lasers, and modulators, and electronic devices such as transistors and transferred electron devices. Being made from a common material permits these devices to be monolithically integrated into optoelectronic circuits which take advantage of the techniques of integrated optics and integrated electronics. This paper will review our progress in the development of monolithically integrated optoelectronic circuits on semi-insulating (SI) GaAs, including a description of a monolithically integrated optical repeater. In addition, results for several new laser structures on SI GaAs will be presented.
A New Approach to Efficient, Wideband Acousto-Optic Guided Wave Devices
Authors: Stewart C. , Stewart W.J. , Brambley D.
Published: February 2023

We have recently reported on surface wave acousto-optic Bragg
interactions at microwave frequencies in titanium-diffused lithium
niobate (Ti:LiNbO3) optical waveguides (1,2). Acousto-optic
Bragg bandwidths up to 530 MHz using a single wideband beam steering
SAW transducer with an upper frequency limit above 2 GHz have been
achieved (2). However, although these devices are sufficiently useful
to allow the practical implementation of a spectrum analyser function,
they suffer from relatively poor efficiency at such high frequencies.
This is partly due to the beam steering configuration used where
adjacent elements are driven in anti-phase and stepped by an integral
number of half wavelengths (3). The resulting bus bar connecting
pattern introduces stray capacitance and losses. The problem is
compounded when multiple tilted beam steering devices are employed
whether these are separately driven via a power divider or connected
together on the substrate. In this paper we propose a new transducer
configuration which should allow greater efficiency together with
wideband operation. We call this device a Continuous Finger Staircase
Array transducer (COFSA).
4-bit 275-MS/s Electrooptic A/D Converter*
Authors: Leonberger F. J. , Woodward C. E. , Becker R. A.
Published: February 2023

The design, development and initial demonstration of a 4-bit 275-MS/s electrooptic A/D converter is reported. The device consists of a mode-locked Nd:YAG laser, an array of Ti-diffused LiNbO3 interferometric modulators, a Ge avalanche photodiode and a special high-speed Si integrated circuit. This converter is of a type originally proposed by Taylor.1 It depends on the periodic variation of the output of a guided-wave interferometric modulator with both voltage and electrode length to perform the conversion and the availability of short optical pulses from mode-locked lasers to perform the analog sampling. The Si integrated circuit acts as a comparator and serial-to-parallel converter. Two detailed studies of the design considerations for this converter have been reported.2,3 There have been a number of reports of fundamental experiments4-6 and devices have been reported7-8 which operated at higher drive powers and at either lower speed or bit number than the device reported here.