bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitive detection of optical-optical double resonance spectra of Na2 using a space-charge–limited diode ionization detector
Authors: Tsai C.-C. , Whang T.-J. , Bahns J. T. , Stwalley W. C.
Published: February 2023

Optical-optical double resonance spectroscopy of molecules with high fluorescence quantum yield (e.g., Na2) has usually been carried out by fluorescence detection. However, we have found that a space-charge-limited diode ionization detector provides a significant sensitivity enhancement for excited states of Na2 that can associatively ionize

(

Na

2

+
Na
→

Na

3
+

+

e
−

)

. These are excited states with electronic energies of ≥228,000 cm-1. For example, we recently studied the

4
1

Σ
g
+

“shelf”1 and the 12Π
g
states2 of Na2 by using fluorescent detection observing υ ≤ 127 and υ≤ 43, respectively. These levels correspond to 83% and 80% of the potential well depth and have outer RKR turning points of 13.4 and 6.5 Å, respectively. Using our new ionization detector, we have observed levels υ ≤ 177 and υ ≤ 79, respectively. These levels correspond to 99% and 99% of the potential well depth and have preliminary outer RKR turning points of 17.0 and 18.1 Å, respectively.
Self trapping of optical beams in photorefractive materials
Authors: Segev Mordechai , Crosignani Bruno , Di-Porto Paulo , Engin Doruk , Yariv Amnon
Published: February 2023

We explore the recently discovered spatial solitons in photorefractive materials,1 where the shape of a light beam modulates the refractive index via the photorefractive effect, and results in an exact compensation for the effects of diffraction, causing the light beam to be self trapped. We study the spectrum of the possible soliton solutions and their characteristics. We derive the material properties and the magnitude of the externally applied electric field, required for experimental demonstrations. Finally, we discuss the unique properties of these photorefractive solitons, such as their independence of the absolute light intensity and their ability to afford gain (or loss).
Holographic learning to classify optically preprocessed signals
Authors: Garvin C. , Wagner K.
Published: February 2023

Linear optical processors (such as optical spectrum analyzers, correlators, optical Wigner processors, and ambiguity function processors)1 can rapidly extract classification features from wide bandwidth signals. However, with dimension-increasing processing (such as the ambiguity function) the output information rate can massively exceed the input capacity of digital computers used for classification. An optical classifier, such as an adaptive optical neural network,2 however, can potentially provide a throughput rate to match the output of the optical feature extractor. As a demonstration of this concept, a broadband communications signal classfier was constructed by cascading an acousto-optic spectrum analyzer with an adaptive holographic pattern classifier using a photorefractive crystal of Fe:LiNbOr. Experimental results obtained by using this two-stage processor asa shift invariant classifier are included. This configuration requires an error-driven learning pathway for weight modification to implement an adaptive classifier. A multilayer system to classify radar returns from an isolated aircraft by using an adaptive neural network classifying the output of an optical ambiguity function processor is proposed.
Performance of grating holograms under large off-Bragg and wavelength mismatch conditions
Authors: Chatterjee M. R. , Min S.
Published: February 2023

Reconfigurability, efficiency, and angular and wavelength selectivities of optical grating holograms have been the subjects of several recent studies. Wu et al.1 have studied the properties of volume holograms vis-a-vis angular and wavelength selectivities and wavelength tunability for relatively small angular deviations from the Bragg angle. Their work emphasizes reconfiguration of an optical interconnection network for an array of photorefractive holograms. Recently, a general formalism was developed for Bragg-domain acousto-optic diffraction of arbitrary-profile optical beams using a straightforward inverse Fourier integral2 involving a so-called plane-wave transfer function for a particular scattered order of light. The formalism was applied to the case of a Gaussian-profile beam for which both numerical and asymptotic analytical solutions were obtained. It was, however, restricted to the typically small (a few milliradians) Bragg angles characteristic of acousto-optic interactions. Recently, the above work has been extended to include both arbitrary beam profiles and Bragg angles for holographic gratings, which may be tilted or untilted.3 This paper concentrates on a direct application of the above modified formalism to the study of the selectivity and tunability of grating holograms.
Improved photorefractive polymers
Authors: Jones Brian , Zhang Ying Bo , Athalye R. V. , Zhang Lie , Wang C. H. , Takacs J. M. , Ducharme Stephen
Published: February 2023

We report the performance of photorefractive polymers that have improved response time and phase stability. The polymers studied consist of a host polymer, an attached nonlinear optical moiety, plus a hole transport agent, similar to those previously reported.1 One such composition consists of the host polymer Bisphenol-A with the moiety 4′-amino-4′-nitrostilbene and the hole transport agent diethyl-aminobenzaldehyde-diphenyl hydrazone. Samples 145 μm thick exhibit a diffraction efficiency of 0.01% and an exponential response time constant of 0.1 s with an applied field of 90 kV/cm at a wavelength of 650 nm, 1.6 μm grating spacing, and an intensity of 0.3 W/cm2. These results represent a 1,000-fold improvement in sensitivity (at comparable absorbance) over the results reported in Ref. 1. There is no observable decrease in the photorefractive or photoconductive sensitivities of a sample stored 20 days at room temperature. This is also the first report, to our knowledge, of photorefractivity in a non-cross-linking electro-optic polymer. We also discuss the influence of the polymer composition, polymer processing, and experimental conditions on photorefractive performance and comparison with direct measurements of electro-optic and photorefractive response.
Quantum noise reduction in nondegenerate parametric amplification
Authors: Ou Z.Y. Jeff , Pereira Silvania F. , Kimble Harry Jeffrey
Published: February 2023

Quantum fluctuations in an optical amplifier are of fundamental as well as technological significance and lead to basic limitations on noise performance. It is well-known that the signal-to-noise ratio (SNR) of an injected signal is degraded in the amplification process due to added noise from thermal or (at best) vacuum fluctuations of the internal modes of the amplifier.[1] However, if the internal modes are coupled to a squeezed vacuum, the added noise in amplification can be reduced.[2] With this motivation, we have constructed a nondegenerate parametric amplifier whose idler mode is itself coupled to a squeezed vacuum, which is generated by a second parametric amplifier. Phase-sensitive noise amplification of a vacuum input to the signal mode is observed with the minimum amplified noise level 0.5dB below the usual phase-insensitive amplified noise level for the amplified signal of the same amplifier but with the idler mode coupled to a vacuum state. Prospects for improvement by increasing the squeezing that is coupled into the idler mode of the amplifier beyond the current level of 2dB as well as surprising results from our theoretical analysis which includes losses will be discussed.
Soliton shadows in optical fibers
Authors: Wang Q. , Wai P. K. A. , Chen C.-J. , Menyuk C. R.
Published: February 2023

Solitons in optical fibers have been proposed for use in alloptical switches. When solitons in opposite polarization eigenstates collide in linearly birefringent fibers, as has been proposed in switch designs,1 they emerge with shadows. In this work, shadows are studied. The shapes of the shadows can be described by an analytic formula based on the linearized equations. We show numerically that, given initial soliton amplitudes, the shadow amplitude decreases as the absolute value of the initial soliton separation increases. The shadow amplitude after a complete collision is about 10–15% of that after a half collision. For a given initial soliton separation, the shadow amplitude increases with the initial soliton amplitudes until the solitons become bounded, rather than passing through each other.
Amplitude-modulated joint transform correlator with noisy images
Authors: Alam M. S. , Karim M. A.
Published: February 2023

A joint transform correlator (JTC) is suitable for real-time matching and tracking operations without the fabrication of a complex filter. However, a classical JTC suffers from low correlation discrimination, large correlation sidelobes, and low diffraction efficiency. A binary JTC may overcome these problems by using nonlinearity in the Fourier plane to binarize the joint power spectrum (JPS). However, JPS binarization is a computation intensive process and may slow down the processing speed of the correlator. In filter based pattern recognition, an amplitude-modulated phase-only filter is found to yield significantly better correlation discrimination than a phase-only filter.1 Applying this technique in JTC, an amplitude-modulated JTC (AMJTC) is found to yield better correlation discrimination than a binary JTC for noise-free inputs.2 However, the main difficulty of this particular AMJTC is the selection of the threshold value used to calculate an amplitude-modulated filter corresponding to the reference. In this paper, we attempt to overcome this problem and study the performance of the AMJTC for noisy input images via computer simulation.
General grating functions for measuring Gaussian laser beam diameters
Authors: Awwal A. A. S. , Cherri A. K.
Published: February 2023

Among many Gaussian laser beam diameter measurement techniques, a relatively fast and inexpensive technique is provided by the use of ruling1, 2 where a Gaussian beams scans the ruling and a detector placed directly on the other side is used to detect the maximum and the minimum transmitted power through the ruling. The ratio P
min
/P
max
is found to be a function of the ratio r
O
/L (beam radius to ruling period).
k-dimensional Fourier transforms in n-dimensional first order systems
Authors: Kauderer Mark
Published: February 2023

Ordinarily, having an n-dimensional operator relation implies operator relations for all dimensions less than n as well. However, for Fourier transforms this is not so. Only the effect of one-dimensional Fourier transforms in two-dimensional first order systems has been solved previously.1 A partial Fourier transform applied to a nonsingular linear transformation produces a Ohio' transformation, i.e., a matrix pivot. This implies a new definition of the symplectic group SP(n, C) for n ≥ 4 as the group generated by n-dimensional nonsingular linear transformations and the n one-dimensional Fourier transforms. This also provides an alternative method for generalizing low-dimensional results to higher dimensions. Several apparently new determinantal identities generalizing Chio's theorem are immediate consequences.
Demonstration of error-free, ultra-long-distance soliton transmission at 10 Gbit/s and beyond
Authors: Lichtman E. , Mollenauer L.F. , Gordon J.P. , Evagelides S.G. , Harvey G.T. , Neubelt M.J.
Published: February 2023

By transmitting 213 bit pseudorandom word trains in a recirculating loop, we have demonstrated error-free (BER < 10-10) soliton transmission over more than 15,000 km in a single channel at 5 Gbit/s and over more than 12,000 km at 10 Gbit/s in a two channel WDM.1 These results were achieved with the use, in the loop, of a narrow-band, frequency guiding filter,2,3 which serves to reduce both jitter in soliton pulse arrival times and soliton amplitude jitter. We have also performed careful measurements of the timing jitter itself, i.e., measurements that allow the jitter to be separated completely from the effects of energy errors. We see firm evidence that the jitter is caused in part by an acoustic interaction,4 in addition to the better known Gordon-Haus effect.
Frequency-shifted heterodyne detection of dynamic light scattering revisited
Authors: Nachman Paul
Published: February 2023

Early experiments to study Brownian motion of particle-fluid suspensions by laser light scattering used electronic spectrum analyzers for detection of the resulting spectral broadening. Inclusion of a local oscillator (LO) beam in such experiments improved signal strengths via the “heterodyne advantage.” However, the difficulty of wave-front matching in the heterodyne technique was emphasized from the start. In recent years, these techniques have largely been supplanted by photon correlation spectroscopy (PCS). We describe a new configuration of heterodyne/spectrum analyzer spectroscopy for the study of small ceramic particles as they form in seeded flames. In our setup, the waists of the LO and scattering beams overlap within the scattering volume, largely eliminating problems of wave-front matching. Our photodiode detector has shot-noise-limited performance for LO beams at the 50-μW level, permitting most of the laser power to be employed in the scattering beam. We discuss the relative advantages of PCS and of this heterodyne technique based on a side-by-side experimental comparison.
Stability and instability of correlated emission lasers
Authors: Strozewski Ann Cavin , Englund John C.
Published: February 2023

The idea of using correlated emission to reduce spontaneous-emission noise in an active interferometer1 has recently been successfully implemented in a He–Ne Zeeman laser,2 an advance of particular significance for the development of high-sensitivity probes of metric gravity.1 Because the sensitivity of such probes is expected to increase with increasing laser power, we have begun assessing the degree to which instability imposes limitations on the operating levels of correlated-emission-laser (CEL) devices. In particular, we have found that the model of Bergou et al.3 of a homogeneously broadened, three-level CEL exhibits transitions to chaos that are very similar to the well-known Haken–Lorenz instability, and at quantitatively similar threshold powers. A CEL model more appropriate to Ref. 2 is also considered.
Gray scale effect on photorefractive dynamics
Authors: Sasaki Hironari , Fainman Yeshaiahu , Lee Sing H.
Published: February 2023

Dynamic photorefractive memories are promising for digital optical computing and optical neural networks because of their large storage capacities and fast memory access.1 Scheduled recording and incremental recording schemes have been introduced to obtain uniformly multiplexed gratings. Recently, the dynamics of a selective erasure process was studied and applied for fast update of memory. However, all these schemes assume simple plane wave recording and neglect the effect of gray scale images on the recording dynamics. Recording gray scale images is common in many practical situations, e.g., gray scale data and Fourier transform of binary data. We analyzed the effect of gray scale images on the dynamics of scheduled and incremental recording as well as the selective erasure processes, assuming that the material response time is inversely proportional to the writing intensity. We found that multiplexing using scheduled recording failed to provide uniform recording of gray scale images. In contrast, incremental recording allows recording of gray scale images, but the required number of iteration cycles varies depending on the gray scale. Selective erasure time is also gray scale dependent, and the darkest region requires twice the time of the brightest region. We will also present the experimental results and compare them with the analysis.
Observation of light amplification in sodium driven by a coherent field
Authors: Gao Jin-Yue , Zhang Han-Zhuang , Guo Xiu-Zhen , Jin Guang-Xu , Wang Qing-Wen , Jiang Yun , Wang De-Zhong , Li Jin-Song
Published: February 2023

There has been much interest in lasing without inversion in three- and four-level systems.1-4
Robust feature-extracted, amplitude-modulated, phase-only-filter-based character-recognition system
Authors: Iftekharuddin K. M. , Awwal A. A. S. , Karim M. A.
Published: February 2023

Among the correlators, conventional Vander Lugt type complex matched filter (CMF) exhibits high signal-to-noise ratio.
Spectroscopic study of the radiation of a discharge in contact with an electrolytic solution
Authors: Cristescu C. P. , Popescu I. M , Preda A. M.
Published: February 2023

The radiation emitted by a plasma generated in restricted volumes, e.g., in high voltage capillary discharges, has interesting features. In a previous work1 we demonstrated that a remarkably long discharge can be obtained with a moderate voltage (10 kV) in contact with the surface of a liquid electrolytical solution. The discharge can have fractal appearance.
Transverse magneto-optical compression of a frequency-chirping, slowed cesium atomic beam
Authors: Yu J. , Djemaa J. , Nosbaum P. , Pillet P.
Published: February 2023

We have transversally compressed a monokinetic cesium atomic beam in a 2D MOT1,2 on the F=4→F′=5 transition of the cesium IX, line. The longitudinal cooling was obtained by frequency-chirped diode lasers.3 Preliminary results have been obtained showing a final diameter of about 50pm and a density of 108at./cm3. We have studied the specificities of a multi-V system as the transition F=4→F′=5 in the cesium atom. Originally proposed for a three-level V-type atomic system4, the process can be easily generalized to F→F+1 (F>=1) transitions. In this case, the atom is assumed to be polarized into the Zeeman sub-level Mf=-F with respect to the local magnetic field inside of the trap. For a non-polarized statistic mixture, two effects modify the compression process. The first one is due to the large variation in the Clebsch-Gordan coefficients.3 The second one comes from the difference between the Larmor frequencies associated to the lower and the upper levels. The both effects lead to a mF-dependent restoring force. Efficient compression can be obtained by preparing the atomic population in the “good” Zeeman sub-levels, |MF|=F. Two methods have been explored in our experiments to polarize the atomic beam. The first one used an additional blue-detuned laser beam to increase the atomic population in the |MF|=f Zeeman sub-levels by optical pumping. In the second one, the σ-polarized cooling laser beam orientated the atomic population in the axial direction during the slowing process. This orientation was adiabatically transformed into transversal ones by entering in the trap. Further experiments are in progress.
Radiometric aspects of the conjunction-integrating sphere—an absolute optical detector
Authors: Feru Valentin M.
Published: February 2023

With a predictable quantum efficiency detector1 and based on the integrating sphere theory2, an absolute measurement method and an absolute optical laser powermeter were described previously.
Gain-guiding in a focused-gain Raman amplifier
Authors: Wessel J. G. , Battle P. R. , Carlsten John
Published: February 2023

A theory that incorporates focused gain and quantum initiation in a Raman amplifier is presented. The spatial structure of the amplified field is conveniently described by a set of nonorthogonal modes.
Femtosecond chemistry of O2/Pd(111): phonon-assisted electronic effects
Authors: Misewich J. A. , Heinz T. F. , Kalamarides A. , Loy M. M. T.
Published: February 2023

Ultrafast laser pulses can produce high transient electronic temperatures (thousands of degrees) in a metal with only a modest rise in the lattice temperature. Recent studies of the desorption of NO molecules from a Pd(111) surface under such conditions revealed a novel desorption mechanism1 associated with this high electronic temperature.
Photoexcited charge transfer to adsorbates at metal surfaces
Authors: Schmuttenmaer C. A. , Cao J. , Aeschlimann M.A. , Elsayed-Ali H. E. , Gao Y. , Miller R. J. D. , Mantell D. A.
Published: February 2023

There are a number of competing models to explain the photochemistry of molecules at metal surfaces induced by short laser pulses. In order to distinguish between these models more needs to be known about the dynamics of excited carriers and how they interact with adsorbed molecules.
Reducing wrap-around error in Lohmann-type holograms
Authors: Eschbach Reiner , Easton Roger L. , Nagarajan Ramesh
Published: February 2023

The Lohmann algorithm for computer-generated holography is well known and easy to implement.1 It maps the complex transmittance (amplitude and phase) of the Fourier transform to the vertical length and horizontal position of a rectangular aperture within a binary cell.
Bayesian neural networks and their applications to the classification of stochastic images in stochastic backgrounds
Authors: Elbaum Marek , Syrkin Mark
Published: February 2023

We consider neural network classifiers which can estimate Bayesian a posteriori probabilities1 as Ideal Observers (IO) for classification of stochastic image patterns for which the Human Observer (HO) is known to be less reliable. Such situations arise across different imaging modalities of interest: medical X- and gamma rays and ultrasound; and passive and active imaging in the visible and the infrared.
The effect of spatial sampling on the visibility of letters and gratings
Authors: Alexander Kenneth R. , Xie Wei , Szlyk Janet P. , Fishman Gerald A.
Published: February 2023

Spatial sampling of visual targets results in a reduction in effective stimulus contrast and a loss of information.1 To determine the contribution of these two factors to grating resolution and to letter identification, we measured visual acuity and contrast thresholds for spatially sampled gratings and letters.
Effect of spatial beam overlap on parametric-downconversion experiments
Authors: Grayson T. P. , Barbosa G.
Published: February 2023

The spatial profile of spontaneous parametric down-conversion has been measured and shown to affect both one photon and two photon counting rates in interference experiments.
Optimal tolerancing procedures for single mode laser-to-fiber coupling schemes
Authors: Szapiel Stanislaw
Published: February 2023

The coupling between light sources like laser diodes and single-mode fibers is of great practical importance.1
Squeezing-induced transparency in a two-level atom
Authors: Ficek Z. , Dalton B. J.
Published: February 2023

The weak probe-beam absorption spectrum of a two-level atom embedded in a squeezed vacuum and driven by a resonance coherent field is known to have absorption and emission components with subnatural linewidths.1,2
Atomic interferometry using crystal diffraction
Authors: Franson J. D. , Jacobs B. C.
Published: February 2023

Atomic interferometers implemented to date have employed mechanical gratings or laser beams as the equivalent of an optical beam splitter. An alternative approach1 using diffraction from cleaved crystal surfaces is currently under investigation. The advantages of using crystal diffraction include a large (over 20 deg.) angular separation of the two beams and a simple, stable apparatus. Some design considerations and preliminary results, including diffraction measurements, from an apparatus under construction will be discussed.
Quantum-noise limits to matter-wave interferometry
Authors: Dowling Jonathan P. , Scully Marian O.
Published: February 2023

The field of atom interferometry1 is interesting since the potential sensitivity of matter-wave interferometers far exceeds that of their light-wave antecedents.2 As was emphasized at the recent Solvay conference on quantum optics, there is at present no paradigm available for calculating the quantum noise limits to matter-wave interferometers.3 We show that the phase uncertainty is inversely proportional to the square root of the total number, rather than the mean number, of atoms in the interferometert.4 We find that a matter-wave interferometer used as a gyroscope can be expected to be more sensitive to rotation by some four orders of magnitude than present laser gyro devices.
Four-level closed-loop model for calculation of thresholdless Raman gain without inversion in alkali-metal vapors
Authors: Donoghue J. , Hemmer P. R. , Shahriar M. S. , Cronin-Golomb M.
Published: February 2023

Previously1 we used a weak probe Mollow sideband calculation in a three-level system to calculate thresholdless Raman gain without inversion for comparison with experimental observations. However the complexity of the result makes it difficult to extend this analysis to compute nonlinear wavemixing or phase conjugate reflectivities in the three-level Λ-system. We now show that under conditions of experimental interest, it is possible to model the three-level system by a four-level four laser field closed loop system2 which results in a simple closed form expression for the gain. The advantage to this simple gain expression is that it permits straightforward computation of wavemixing and phase conjugate reflectivity. Detailed analysis of the four level system approach will be presented to clearly identify the regions where it is valid to model a three-level system by a four-level system. In particular, in the limit of low intensity or large detunings, the four level calculation is in good quantitative agreement with three level Mollow sideband gain calculations which in turn agreed qualitatively with experimental results.3-4 We will also show preliminary results of wavemixing calculations for sodium vapor using the simple gain expression produced by this model.
Dynamics of hole tunneling by means of strain effects in asymmetry-coupled quantum wells
Authors: Chen Po-An , Chang Chun-Yen , Juang Cheng
Published: February 2023

Hole coherent tunneling in the valence band for strained AlInAs/InGaAs asymmetry coupled quantum well (ACQW) structures are investigated theoretically An ACQW system of a 41Å narrow well (unstrained well) and a 61Å wide well (strained well) separated by a 25Å barrier is taken into consideration. Dynamics of interwell coherent oscillations are described by a numerical implementation using the time-dependent Schrödinger equation 1 with the Luttinger-Kohn Hamiltonian as well as the Pikus-Bir Hamiltonian 2 Tunneling processes are demonstrated at different internal strains (lattice matched case biaxial compression, and biaxial tension) and external electric fields. The resonance oscillations of ground states wavepackets in adjacent wells occur at higher electric field (more negative) under biaxial compressive strain, and take place at lower electric field (close to zero) for biaxial tensile strained ACQWs. Moreover with a nonzero in plane wave vector (k//≠0) a strong resonance tunneling between the heavy and the light hole levels occurs at some electric field due to mixing effects, which are greatly enhanced by internal strains. This oscillation frequency is faster than the heavy-heavy holes spatial tunneling Both the tunneling probabilities and the oscillation frequencies are functions of mixing effects, electric field effects, and strain effects.
Programmable femtosecond pulse shaping
Authors: Wefers Marc M. , Nelson K. A.
Published: February 2023

We will describe the latest developments in computer controlled femtosecond pulse-shaping. The use of shaped ultrashort waveforms has already yielded new experimental results.1 Application of programmable femtosecond waveforms for optical control of molecular behaviour has been treated theoretically.2 The technique involves linear filtering of the spatially dispersed frequency components of an ultrashort pulse. Recollimation of the dispersed beam yields a waveform ‘shaped’ in the time domain. The present results expand on the pioneering works by Weiner, Heritage, and coworkers at Bellcore3,4 who first demonstrated femtosecond pulse-shaping using these methods.
Wide-bandwidth terahertz system based on a GaAs-on-silicon receiver
Authors: Pedersen J. Engholm , Keidling S. Rud , Sørensen C. B. , Lindelof P. E.
Published: February 2023

Freely propagating, subpicosecond electromagnetic pulses with a bandwidth extending well into the far-infrared can be generated and detected using photoconducting switches. Several applications in spectroscopy have already been reported. However, all systems used have suffered from bandwidth limitations imposed by the receiver. The most common receiver substrate material is silicon-on-sapphire. One bandwidth limiting factor then arises from absorption of the high frequency components of the pulse in the sapphire.1 In this work we demonstrate that GaAs-on-silicon is an attractive, alternative detector substrate material. A 1.5 μm layer of GaAs was grown at 460°C by MBE on a high-resistivity silicon wafer. High-resistivity silicon has negligible absorption and overcome. X-ray diffraction measurements indicate the formation of micro crystallites in the GaAs layer due to the lattice mismatch between GaAs and silicon. These material characteristics are similar to those observed in low temperature growth GaAs 2, and they demonstrate the potential of GaAs-on-silicon in high speed photoconductor applications. Our measurements indicated a bandwidth of at least 5 terahertz for this receiver.
Quasi-isotropic and quasi-homogeneous forward scattering of light in the ocean
Authors: Gozani Joseph
Published: February 2023

Ignoring large-scale anisotropy and intermittency produces difficulties when experimental and theoretical results are compared. A new theory that incorporates anisotropy and intermittency into the propagation of light in a forward scattering media, such as the ocean, is presented. First, we extend the narrow angle approximation1 of the radiative transfer equation to account for scattering by a cluster of anisotropic particles. Second, effects of large scale deterministic and random currents are included in the theory. Third, a uniform approximate solution by the multiple-scale embedding technique2 provides a new analytic approximation for the problem. Fourth, intermittent effects by turbulence and internal waves are discussed in the framework of wave propagation through intermittent media.3 The importance of using correct scales relevant to the particular experiment’s parameters is discussed. Future developments of this problem will also be suggested.
Design and fabrication of a binary phase grating for a selective-order-missing spot array
Authors: Suh Ho Hyung , Kwak Chong Hoon , Jeong Jong Sool
Published: February 2023

The binary phase gratings (BPGs) for generating multispot array1 (called Dammann grating) are promising optical fan-out elements for applications including fiber-optic star couplers, free-space optical interconnections, and multiple image arrays. The conventional BPGs, however, have been so far mainly developed for odd numbered spot array generation because of its simplicity of design algorithm.2 We present a novel method of designing the BPGs for generating selective order missing (SOM) spot arrays including odd numbered, even numbered3, and irregularly spaced spot array. Gradient descent rule with variable target values in the merit function is introduced as a nonlinear optimization algorithm. The uniformity of the SOM array is very high such that the standard deviation of the beam array intensity is less than 10−6. It is also found that when the structure of the grating is symmetric in a period, it should be anti-symmetric in each half period in order to get an even numbered spot array, and vice versa. The designed BPGs are also experimentally demonstrated using the conventional e-beam lithographic technique on a quartz substrate. The SOM spot array may be applicable to the digital optical processing systems using S-SEED and smart pixel devices.
Pressure-tuned spectroscopy of II–VI semiconducting nanocrystals
Authors: Silvestri Markus R. , Persans Peter D. , Schroeder John
Published: February 2023

Here CdSxSe1-x nanocrystals were studied and characterized by resonant Raman scattering, low frequency inelastic scattering, pressure tuned Raman scattering and photoluminescence. Ordinary Raman scattering and low frequency inelastic scattering were used for composition and size characterization. In the photoluminescence spectra we found that the deep defects where symbatic for compositions in the range close to CdS. For intermediate compositions down to CdSe no marked change in the defect peak positions were observed. This behavior is similar to the bulk case.1 Also the pressure coefficients in our measurements reflected this peculiarity. Resonant Raman scattering at different pressures was applied to examine the electron phonon interaction in the framework of the one dimensional configuration model. We found that the coupling strength (Huang-Rhys parameter) is larger than expected from theory and might indicate an extrinsic effect such as a point defect.2 The pressure dependence of the coupling was also compared with bulk CdS calculated from phonon replicas of the green defect line 3 and we found the same tendency of weakening with pressure. In the case of nanocrystals we were able to observe this beyond the phase transition point of bulk due to their higher stability or superpressure effects.
Properties of dark-gap solitons
Authors: de Sterke C. Martijn
Published: February 2023

It is well known that nonlinear periodic media support gap solitons. These solutions for the electric field, which vanish asymptotically, can exist because at high intensities the nonlinearity shifts the position of the photonic band gap. Frequencies which are inside the photonic band gap at low intensities, and thus are evanescent, may fall outside the gap at high intensities, and thus are propagating.
Tunable diode lasers and spectroscopy
Authors: Akulshin A. M. , Celikov A. A. , Napartovich M. A. , Senkov N. V. , Vasiliev V. V. , Velichansky V. L. , Yarovitsky A. V. , Zibrov A. S.
Published: February 2023

The two techniques of the LD linewidth narrowing are used in spectroscopy: strong coupling to a low-Q external cavity1, and weak coupling to a multi-pass interferometer2. Both techniques have advantages3. The introduction is focused on the possibilities of realizing the stable single mode operation of a LD strongly coupled to high-Q cavity.
RNB (RbNbB206) and its isomorphs—a new family of nonlinear-optical materials
Authors: Nicholls J.F.H. , Chai B.H.T. , Hagan D.J , Henderson B.
Published: February 2023

The new crystal RNB (RbNbB206) has been investigated and the XYB2O6 family of isomorphs (where X=Cs, Rb, K, Y=Nb or Ta) has been identified as a potential structure for χ(2) type nonlinear optical applications.
New measurements with laser-cooled metastable xenon
Authors: Walhout M. , Witte A. , Rolston S.L.
Published: February 2023

Laser-cooled metastable xenon has been identified as a promising candidate for a new atomic clock based on an optical frequency.
Minimally invasive therapy of solid tumors using image-guided interstitial laser photocoagulation
Authors: Wilson Brian C. , Wyman Douglas R.
Published: February 2023

The use of infrared lasers and interstitially placed optical fibers for in situ thermal destruction of tissue through induction of coagulative necrosis (50-80% temperature range, without ablation) is being investigated for a number of potential clinical applications: e.g. inoperable malignant tumors such as in the brain, liver and g.i. tract, benign prostate hypertrophy.
Subrecoil laser cooling: recent developments in velocity-selective coherent population trapping
Authors: Bardou F. , Emile O. , Saubamea B. , Shimizu K. , Westbrook C. , Aspect A. , Cohen-Tannoudji C.
Published: February 2023

Velocity-selective coherent population trapping (VSCPT) is the first demonstrated sub-recoil laser cooling scheme.1
Measurements of 1/f frequency-noise reduction in semiconductor lasers by using optical feedback with dispersive loss
Authors: Kitching J. , Shevy Y. , Iannelli J. , Yariv A.
Published: February 2023

A single-mode semiconductor laser is subjected to weak optical feedback from an external cavity containing a cell filled with Cs vapor.
Dark spatial solitons in absorbing or saturating nonlinear media
Authors: Luther-Davies Barry , Yang Xiaoping , Krolikowski Weislaw , Akmediev Nail , Andersen David Roger
Published: February 2023

Dark spatial solitons can be used to write reconfigurable optical waveguides into defocussing non-linear materials.
Optoelectronic neural-network module with digital holographic memory
Authors: Sasaki Hironori , Ma Jian , Mauduit Nicolas , Fainman Yeshaiahu , Lee Sing H.
Published: February 2023

Large scale neural networks are required by numerous applications.
Determination of an optical window for myocardial tissue
Authors: Shukes S. , Splinter R. , Raja M. Y. A. , Svenson R. H. , Tuntelder J. R. , Dezern K. R. , Thompson M. , Tatsis G. P.
Published: February 2023

Absorption and scattering coefficients of turbid tissue have a substantial effect on beam propagation.
Third-order dispersion in femtosecond fiber lasers
Authors: Dennis Michael L , Duling Irl N.
Published: February 2023

Femtosecond pulses have been obtained in a variety of passively mode-locked all-fiber laser systems with Er gain, with pulse lengths as short as 160 fs reported.
Automated deposition of multilayer coatings based on wideband optical monitoring techniques
Authors: Sullivan Brian T.
Published: February 2023

Complex optical multilayer coatings can now be reliably manufactured using a fully automated real time process control with an in-situ wideband optical monitor.
Resonant upconversion and cross-relaxation through nonradiative, coupled-ion energy transfer between Er3+ ions in Er3+-doped lithium niobate (Er:LiNbO3)
Authors: Gill D. M. , Wright J. C. , McCaughan L.
Published: February 2023

LiNbO3 is an active host medium for guided wave electro-optics and has been the basis for the largest, most sophisticated integrated optic structures to date.
Analytic approach to cavity design for Kerrlens mode locking
Authors: Lin Kuei-Huei , Hsieh Wen-Feng
Published: February 2023

Recently, the optical Kerr effect has been used for mode locking (KLM) solid state lasers and ultra-short laser pulses has been obtained.
Correction of thermal aberrations by non-linear lensing in self-mode-locked lasers
Authors: Cormier Jean-François , Piché Michel , Salin François
Published: February 2023

Solid-state lasers are known1 to undergo a transition to a regime of self-modelocking where trains of ultrashort laser pulses are generated reliably.
Novel unstable-resonator for generation of scanable-radius rings of light
Authors: Wang Xiao , Littman Michael G. , Rabitz Herschel , McManus Barry
Published: February 2023

We report an unstable-resonator cavity design that has a ring output mode.
Sub-shot-noise microscopy with squeezed light
Authors: Kolobov Mikhail I. , Kumar Prem
Published: February 2023

Quantum limit of sensitivity in optical imaging with coherent light is set by the shot noise of photodetection.
Applications of photon-scanning tunneling microscopy
Authors: Tsai D. P. , Moskovits M.
Published: February 2023

Photon-scanning tunneling microscopy (PSTM)1,2 is a novel technique for probing the evanescent field with subwavelength spatial resolution at surfaces.
Autler-Townes absorption spectrum of a two-level atom irradiated by an intense bichromatic laser field
Authors: Van Leeuwen Michael F. , Papademetriou Stephanos , Stroud Carlos R.
Published: February 2023

The dressed-atom formalism has been used to provide an appealingly transparent interpretation of the dynamics of a two-level atom coupled to a monochromatic field,1 and has recently been applied to the case of a 100% amplitude modulated field.
Spontaneous-emission factors of microring and microdisk lasers
Authors: Chu Daniel Y. , Chin Mee Koy , Ho Seng-Tiong
Published: February 2023

Recently, McCall et al. have demonstrated a 2-D strongly guided microdisk structure1 to achieve low-threshold lasing.
Microdisk-laser linewidths near threshold
Authors: Mohideen U. , Slusher R. E. , McCall S. L. , Jahnke F. , Koch S. W.
Published: February 2023

Semiconductor microdisks form high Q, low volume microcavities with diameters between 2 and 5μm and thicknesses near 0.1 μm.
Design of a perfectly conducting binary-grating lens for near-field operation
Authors: Kok Yon-Lin
Published: February 2023

In contrast to conventional Fresnel lenses operating in the far field, a perfectly conducting binary grating lens is synthesized to focus light intensity at a prescribed near field location.
Passive and active computer-generated waveguide holograms
Authors: Najafi S. Iraj , Honkanen Seppo , Saarinen Jyrki , Zhang Guangwen , Huttunen Juhani
Published: February 2023

We have recently reported demonstration of ion-exchanged computer generated waveguide holograms.1 Double potassium and silver ion exchange process was employed to make Dammann grating in a slab waveguide.
248-nm emission from discharge-excited KrF2
Authors: Kurnit N. A. , McCown A. W. , Thomas S. J. , Tiee J. J.
Published: February 2023

Photolysis of KrF2 has long been known as a method to populate KrF excimer molecules and has been utilized1 in measurements of fluorescent lifetimes and quenching rates of KrF(B).
Depolarization of optical pulses from an optical fiber used in a pulse compressor
Authors: Tang Xiaodong , Yan Li
Published: February 2023

We studied the depolarization of the output pulses from a 9 m single mode optical fiber that was used in compression of pulses from a CW mode-locked Nd:YLF laser. The input pulses were linearly polarized. The degree of polarization of the output pulses was found to be asymmetric: greater than 0.98 for the input polarization oriented along one principal axis of the fiber, but less than 0.40 when the input polarization was along the orthogonal principal axis of the fiber.
Strain measurement and photoelastic effect in InGaAsP diode lasers
Authors: Yang Jian , Cassidy Daniel T.
Published: February 2023

Polarization-resolved electroluminescence1 and photoluminescence have been demonstrated to be sensitive techniques for measurement of strain in semiconducting luminescent material.2,3 In this paper, strain in the active region of InGaAsP diode lasers has been imaged using spatially resolved and polarization-resolved electroluminescence. Lasers of three different structures were studied: gain guided, ridge waveguide (RWG) and planar buried heterostructure. Experimental results show that the distributions of strain in the plane of the active region are structure dependent. The source of the strain is discussed. A modified theoretical model4 of the strain of RWG laser is examined and compared with experimental results. Finally, the photoelastic effect based on the measured strain distribution is studied. The refractive index distribution owing to the measured strain distribution is calculated. Results show that strain-induced refractive index change for a TE polarized mode is smaller than that for a TM polarized mode. For a TM mode, a strain-induced refractive index change that is antiwaveguiding of up to -3x10-3 is predicted. It is also predicted that the gain for the TM mode is enhanced by the strain. The combination of these effects may explain the polarization state of RWG lasers.
Modeling nonlinear optics in microdroplets
Authors: Hill Steven C.
Published: February 2023

Nonlinear mixing processes such as coherent anti-Stokes Raman scattering (CARS),1 and third-order sum-frequency generation (TSFG)2 have been modeled in microdroplets. The radiation from the third-order nonlinear polarization is modified by the spherical cavity. When the input waves are Gaussian beams tightly-focused near the center of the droplet, the morphology-dependent resonances (MDRs) are not excited, and the phase matching analysis is similar to that in bulk materials (the bending of the beams at the droplet surface must be considered). CARS generated by such focused beams may be useful for probing the spatially-dependent internal species concentrations. When the generating waves are focused at the edge of the droplet, or when the generating waves have been generated inside the droplet by a nonlinear process (e.g., stimulated Raman scattering in the case of TSFG), then the output intensity is very sensitive to droplet size, and to the spatial and frequency overlaps between the MDRs. Intensity-dependent shifts in MDR frequencies, and effects of two-photon on time-dependent scattering have also been modeled.3
Optoelectronic broadband signal processor
Authors: Lam D. , MacDonald R. I.
Published: February 2023

Because of its low loss (<0.2 dB/km) and low dispersion (<17ps/nm/km), optical fiber has been widely recognized for its potential in delay line signal processing applications [3, 4, 5]. However, the high insertion loss of optical switches and the high cost of optical amplifiers restrict the implementation of a reconfigurable optical fiber delay line signal processor. Optoelectronic implementation of a switched delay line processor may be simpler and more practical. An optoelectronic ring resonator using a photoconductor receiver has been demonstrated [6], and a 16 tap transversal filter based on MSM photodetector array has been exhibited with programmable bandwidth of 500 MHz [7].
Decay of quantum states by conditional measurements
Authors: Buzek Vladimir , Kurizki Gershon
Published: February 2023

We consider a single-mode cavity field that is resonant with two-level atoms crossing the cavity in a sequence whose duration is much shorter than the cavity ring-down time (negligible dissipation). Conditional measurements selecting those sequences wherein each atom is “elastically scattered” (emerges in its initial state), can reduce an arbitrary initial field state to a Fock state, controllable by the field-atom interaction time.1
Discretized wavevectors in bulk magneto-optics
Authors: Nelson Seth , Guney Durdu O. , Davis James , Levy Miguel
Published: February 2023

We introduce a wavevector discretization formulation for bulk magneto-optics. The natural discretization described herewith results in a nonlocal complex amplitude superposition of polarization states. Our analysis reveals the emergence of a multiplicity of discretized modes within elliptical and linear polarization pairs. This mode multiplicity is not due to confinement or resonance effects. Rather, it arises from the variance in refractive index for different beam-propagation directions in magneto-optic materials. Theoretical and numerical solutions leading to this result are presented herewith, together with computational verification of the theory applied to bismuth-substituted iron garnets. These results may lead to applications to quantum phenomena with single photons while maintaining a simpler classical architecture.
Full-field quantitative X-ray phase nanotomography via space-domain Kramers–Kronig relations
Authors: Lee KyeoReh , Lim Jun , Park YongKeun
Published: February 2023

Given the low absorption contrast of X-rays, phase shift has been
playing an important role as an alternative source of contrast in
X-ray nanoimaging. Numerous phase-measuring techniques have been
proposed, most of which, however, are based on significant assumptions
or sample translations. In this study, we propose the application of
Kramers–Kronig (KK) relations in the spatial domain as a solution to
allow the X-ray quantitative phase image to be directly calculated
from the measured intensity image without any additional requirements.
Based on this straightforward principle, we have presented KK
nanotomography by introducing a spatial-frequency cutoff filter into a
conventional tomographic setup. The robustness and versatility of the
proposed method were experimentally verified based on
various sample tomograms. We expect KK nanotomography
to be widely adopted as a powerful and easy-to-adapt phase
quantification solution for X-ray microscopes.