bluuebunny/crossref_metadata_2025 huggingface dataset:
Snake-Light Translucent Phantoms Tomography
Authors: Ho P. P. , Liang X. , Wang L. , Alfano R.
Published: February 2023

Translucent phantoms hidden in thick Intralipid scattering solutions have been imaged as a function of phantom scattering coefficient and optical density using picosecond time and spatial gated Kerr-Fourier transillumination imaging system. Weakly-absorbing phantoms of 0.25-mm width black/white bars with the opacity difference of OD=0.14 can be distinguished through a 50-mm highly scattering Intralipid solution. For translucent scattering phantoms, such as droplets and phantom cell, less than 5% differential concentration of a 2-mm thick phantom cell can be distinguished from the background medium with the absolute signal difference of 10−10 of the incident illumination intensity.
Fluorescence and Phosphorescence Lifetime-Based Sensing in Tissues
Authors: Sevick-Muraca Eva M. , Burch Christina L.
Published: February 2023

The use of fluorescent and phosphorescent optical probes for non-invasive chemical-based sensing in tissues is investigated using finite element computations. The results show that when the lifetime of the probe is significantly longer than the time associated with photon migration, the origin of the re-emitted signal becomes located closest to the surface. In order to probe more deeply, optical probes with lifetimes on the order of photo migration times are required. In such cases, deconvolution of the photon migration times from probe lifetimes are necessary for lifetime-based biochemical sensing in tissues.
Time-Resolved Optoacoustic Imaging in Layered Biological Tissues
Authors: Oraevsky Alexander A. , Jacques Steven L. , Esenaliev Rinat O. , Tittel Frank K.
Published: February 2023

A new technique based on time-resolved detection of laser-induced stress transients is proposed to visualize distributions of absorbed laser fluence in turbid and layered biological tissues.
Snake Photon Imaging in Thick Tissues in Visible and Near Infrared Radiation Spectral Region
Authors: Das B. B. , Yoo K. M. , Alfano R. R.
Published: February 2023

Time-resolved transillumination techniques have been used to image opaque1-6 and partially absorbing7-10 objects hidden in various random media. When ultrashort laser pulses are incident on a slab of scattering medium the transmitted pulses consist of a ballistic (coherent) component11-12, a diffuse component and a snake component1. Using time-resolved detection techniques, the snake photons can be separated from the diffuse component and used to construct the image of an object hidden in a scattering medium with different optical properties. Recently, it has been shown that thick tissue imaging is possible using snake photons in the visible region10.
Waves in Highly Heterogeneous Media
Authors: Weaver Richard L.
Published: February 2023

Recent time-domain ultrasonic and numerical experiments on classical waves in two-dimensional Anderson localizing random media are reviewed. It is shown that the transport, albeit weak, occurs on a time scale comparable to a diffusive time scale, and is not exponentially slow. The time scales of the transport over distances of several localization lengths are found to scale with the ≈2.46 power of source/receiver distance. It is also shown that absorption has no effect on the localization of the eigenmodes, though it can make the observation of that localization more difficult, especially if those observations are by means of measurements of steady state transmission.
Wave Dynamics and Spectral Correlation in Random Media
Authors: Genack A. Z. , Polkosnik W. , Lisyansky A. A. , Garcia N. , Sebbah P.
Published: February 2023

We present measurements of the microwave field transmitted through an ensemble of random dielectric samples. We compare the field correlation function with frequency shift with the intensity correlation function and relate it to the dynamic measurement of the time of flight distribution. Finally, we present measurements of the total phase accumulated by the wave in passing through random samples.
Theory of Multiple-Light-Scattering Spectroscopy
Authors: John Sajeev
Published: February 2023

We present an algorithm for determining the dielectric autocorrelation function of a disordered medium from angle resolved multiple light scattering measurements. Photons propagating in a disordered, multiple scattering medium are classified as being either ballistic, “snake-like” or diffusive, depending on the nature of their trajectory between source and detector. Considerable information about the nature of the scattering medium is contained in the early arriving snake-like photons whereas this information is smeared in the late-arriving diffusive photons. We derive from first principle a formal mathematical description which encompasses all three regimes of transport and relates the experimentally observed light intensity correlation functions to the ensemble averaged autocorrelation function

B
˜

(

x
→

,

y
→

)
≡

〈

ε
*

(

x
→

)
ε
(

y
→

)

〉

ens

for a disordered medium with dielectric constant

ε
(

x
→

)

.
High Resolution Optical Coherence Tomography using Deconvolution
Authors: Kulkami Manish D. , Tobocman William , Izatt Joseph A.
Published: February 2023

Longitudinal resolution enhancement has been achieved in optical coherence tomography using digital deconvolution methods.
Imaging through biological tissues by use of optical low-coherence heterodyne detection technique
Authors: Chan Kin Pui , Yamada Makoto , Inaba Humio
Published: February 2023

A coherent detection imaging system has been modified to employ a super-luminescent diode as low-coherence optical source for optical imaging through strongly scattering media such as biological tissues. By appropriately fixing the coherence gating, the system is able to selectively detect the coherent components of transmitted light. Using this system we have demonstrated the feasibility of optical heterodyne detection method in discriminating against the diffuse photons. The unique applications of low-coherence heterodyne detection in transillumination imaging that may potentially yield useful diagnostic information on tissue structures are also presented.
Imaging of Physiological Functions by Laser Transillumination
Authors: Shimizu Koichi , Yamamoto Katsuyuki
Published: February 2023

Attempts were made to visualize the functional change inside a living biological body using a transillumination technique. With a near-infrared light, the transillumination images of a mouse abdomen and a rat brain were obtained. To examine the feasibility of functional imaging, a localized hypoxia was made in each of above body parts. They were visualized using transillumination images of multiple wavelengths of light. It was found that the changes in the brain blood volume and in the oxygenation state of tissues could be detected noninvasively. In this way, the spatial distribution of these changes could be visualized in the transillumination images of a living body. Through this study, the feasibility of optical trans-body imaging of physiological functions was verified.
CT Imaging of Biological Body with CW Laser Light
Authors: Kitama Masataka , Shimizu Koichi , Yamamoto Katsuyuki
Published: February 2023

The feasibility of an optical CT with a CW light was investigated. A technique called “a scattering angle differential technique” has been newly developed to suppress the effect of scattering in the imaging through diffuse media. The effectiveness of this technique was demonstrated in the CT imaging of a model phantom. However, it was found in experiments that this technique alone was not effective with a living mouse. The problem was found to be the reflection and the refraction at the air-tissue interface. Another technique called “a contact technique” was newly developed to overcome this problem. A measurement system was developed to use both techniques simultaneously. Using this system, the CT imaging of a mouse abdomen was attempted. Though the spatial resolution was poor, the existence of a liver and kidneys were recognized in the CT image of a living mouse.
Mammography
Authors: Whitman Gary J. , Kopans Daniel B.
Published: February 2023

This paper is a review of normal breast anatomy, breast pathology, and mammography. The principles of mammography are presented from a radiologist's perspective.
Coregistration of Images From Diffusive Wave with Other Imaging Modalities to Enhance Optical Specificity
Authors: Ntziachristos V. , O'Leary M. A. , Chance B. , Yodh A. G.
Published: February 2023

We propose an algorithm that combines the spatial resolution available from other imaging modalities, such as MRI, X-ray CT or ultrasound, with the specificity of optical tomography. The algorithm reduces the complexity of the inverse problem, and thus the number of measurements necessary for an accurate reconstruction. We describe the underlying theory and present simulation and experimental results.
Small Body Approximation and Efficient Algorithm for Solving Inverse Problem
Authors: Katsevich Alexander , George John , Ramm Alexander
Published: February 2023

An efficient algorithm is proposed for locating an inhomogeneity D in a turbid medium and estimating its cumulant anomalous diffusion and absorption coefficients δk
D
and

δ

μ
a
D

. Here δk
D
= ∫
D
δk(y)dy and

δ

μ
a
D

=

∫
D

δ

μ
a

(
y
)
d
y

. Results of preliminary testing of the algorithm are presented.
Origins of Tissue Optical Properties in the UVA, Visible, and NIR Regions
Authors: Jacques Steven L.
Published: February 2023

This paper describes the relationship between the ultrastructure of biological tissues and the observed macroscopic optical scattering properties. A summary of the tissue absorption spectrum is also presented. The scattering of soft tissues (liver, prostate, etc.) and fibrous tissues such as dermis are considered. The scattering of soft tissues is attribued to membranous structures and modeled as Mie scattering from spheres in the 0.2-2-μm diameter range, where membrane lipids occupy about 1-20% of the cellular volume and the refractive index mismatch is 1.46/1.35. The scattering of dermis is modeled as scattering from collagen fiber bundles in the 2.8-μm diameter range occupying 21% of the dermal volume and the refractive index mismatch is 1.38/1.35. The effects of a component of small-scale particle scattering in the Rayleigh limit is also considered. The models are compared with tissue values from the literature for the reduced scattering coefficient, μs(1-g), and the anisotropy, g. The models roughly match the absolute value and wavelength dependence of scattering in the 300-1100 nm wavelength range.
In vivo Measurement of Reduced Scattering and Absorption Coefficients of Living Tissue using Time-Resolved Spectroscopy
Authors: Yamashita Y. , Oda M. , Naruse H. , Tamura M.
Published: February 2023

Reduced scattering and absorption coefficients of piglet head were measured in-vivo by analyzing the observed temporal responses based on the diffusion theory. The reduced scattering and absorption coefficients in normoxic condition were around 1.3 and 0.013 [mm-1], respectively, at the wavelength of 760nm. When hypoxia was induced, the absorption coefficient was increasing, while the scattering coefficient was constant. It was suggested that in-vivo measurement of the optical parameters in piglet head was possible based on the photon diffusion theory.
Analytic Solution to the Inverse Problem in Diffusion Tomography
Authors: Schotland John C.
Published: February 2023

We consider the problem of imaging the optical properties of a highly-scattering medium probed by diffusive light. An analytic solution to the tomographic image reconstruction problem is presented.
Comparison of Finite Difference Transport and Diffusion Calculations for Photon Migration in Homogenous and Heterogeneous Tissues
Authors: Hielscher Andreas H. , Alcouffe Raymond E. , Hanson Kenneth M. , George John S.
Published: February 2023

The limits of the diffusion approximation to the time-independent of radiative transfer are analyzed for homogeneous and heterogeneous biological media by comparing diffusion theory calculations to accurate finite difference transport calculations.
Convolution Backprojection Reconstruction from Photon Density Waves
Authors: Eckman Peter M. , Faris Gregory W.
Published: February 2023

We describe the application of the convolution backprojection algorithm to reconstruction of a simple object viewed with photon density waves.
Ultrafast Upconversion Time-Gating in Rare-Earth Doped Glasses for Optical Imaging Through Highly Scattering Media.
Authors: Voevodkin George , van Doom Tim
Published: February 2023

A new subpicosecond time-gating technique based on two step upconversion absorption of signal and reference pulses at two different wavelengths by rare-earth ions (Pr3+) is presented.
Time-resolved Polarization Shadowgrams in Turbid Media
Authors: Liang X. , Wang L. , Ho P.P. , Alfano R.R.
Published: February 2023

Time-resolved polarized and depolarized 2D images of test bars hidden inside a diluted 5-cm thick Intralipid solution have been measured using a picosecond Kerr-Fourier imaging system.
Experimental results from the second generation adaptive optics system on the Starfire Optical Range 1.5 meter telescope
Authors: Fugate Robert Q.
Published: February 2023

The Starfire Optical Range 1.5 meter telescope is equipped with a 208 subaperture, 241 actuator adaptive optics system operating at visible wavelengths. The adaptive optics are located in a coudé room. A copper vapor laser beam is injected into the coudé feed with a polarizing beam splitter aperture sharing element and is focused at 10 km or greater range in the atmosphere to generate a Rayleigh laser guide star. The wavefront distortion on the returned light is sensed with a Shack-Hartmann sensor. Full aperture tilt of a nearby natural guide star is sensed by computation of the image centroid using a 14×14 CCD array and corrected by control of a fast two axis tip-tilt mirror. The optics are arranged such that either light from a natural star or light returned from a laser guide star can be used for wavefront distortion measurements.
MicroThermal Instrumentation for Haleakala Site Survey Development and Implementation
Authors: Sheinis A. , Cowie L. , McKenna D.
Published: February 2023

The University of Hawaii (UH) Institute for Astronomy (IFA) has undergone a microthermal characterization exercise of the summit of Mt. Haleakala, Maui Hawaii. Instrumentation specific to this characterization has been developed jointly by the UH School for Ocean and Earth Science (SOEST) and the UH IFA. This paper details the instrumentation (development and characterization), discusses the specific data acquisition and reduction techniques, and gives the preliminary results of the survey.
Atmospheric Phase Structure Function Measurements With A Shack-Hartmann Wavefront Sensor
Authors: Dayton David , Gonglewski John , Venet Boris
Published: February 2023

A Shack-Hartmann wavefront sensor placed at a pupil of an optical system can be used to measure atmospherically-induced wavefront aberrations across the pupil. This infromation can be used to reconstruct the phase of the wavefront and from that calculate a phase structure function. Of particular interest are measurements of the slope of the log of the structure function and the outer scale of the sutructure function.
Compensated Speckle Imaging: Theory and Experimental Results
Authors: Roggemann Michael C. , Caudill Eugene L. , Tyler David W. , Bilmont Marsha F. , Von Bokern Mark
Published: February 2023

In this paper we report the results of compensated speckle imaging experiments conducted at a compensated telescope operated by the US Air Force. The power spectrum signal-to-noise ratio (SNR) is used as the metric for evaluating the performance. Comparing the compensated and uncompensated results shows that the compensated power spectrum SNR is significantly higher than the uncompensated power spectrum SNR at low spatial frequencies. A previously derived expression which expressed the power spectrum signal-to-noise ratio in terms of the compensated optical transfer function statistics and object parameters is verified using experimental data.
On The Implementation Of Adaptive Optics For Improving Broadband Spectral Response In Michelson Interferometry
Authors: Loos G. C.
Published: February 2023

Beginning with the experiments by Michelson in the 1920's and continuing with more recent research activities around the world Michelson interferometry has evolved into a powerful tool for measuring the diameters of giant stars and separations and orbits of multiple star systems. This paper offers calculations of the wavelength dependent limiting sensitivity achievable using a two aperture interferometer, without or with partial adaptive optics corrections, based upon realistic assumptions in regard to system noise sources. Results are presented for the case of observing resolved stars characterized as spectral type G2V, the spectral classification of the sun.
Low Order Adaptive Optics: A computer Simulation.
Authors: Northcott M.J.
Published: February 2023

We discuss a computer simulation of the University of Hawaii low order adaptive optics system. We compare simulation predictions, to behaviour of the real system.
Analysis of Multiconjugate Adaptive Optics
Authors: Johnston Dustin C. , Welsh Byron M.
Published: February 2023

Adaptive optics has been used to obtain spectacular images of binary stars with nearly diffraction limited resolution [1]. To date, however, we have not seen similar pictures of, for example, the planet Jupiter, because of the small size of the corrected field. Theoretical analysis of adaptive optical telescopes has shown that the low levels of residual phase error required to achieve such high resolution is only obtained over a field which is a few arcseconds in diameter [2]. The reason for this limitation is that as the reference source used for wavefront sensor (WFS) measurements is increasingly separated from the object points to be compensated, the reference and object wavefronts are increasingly decorrelated. When the angular separation between object and wavefront is greater than approximately the isoplanatic angle, the WFS measurements are no longer useful for image compensation.
Compensated imaging using hybrid techniques: experiment and results
Authors: Bilmont Marsha F. , Von Bokern Mark A. , Voelz David G. , Roggemann Michael C. , Albetski John P.
Published: February 2023

We describe an experimental system that incorporates a low-noise, short exposure time camera with the deformable mirror system on the 1.6m telescope at AMOS. Binary and single star image results are presented for a variety of system parameters and operating conditions.
PAMELA: Fabrication and test of a telescope with a 36 segment adaptive primary mirror
Authors: Ulich Bobby , Gleckler Anthony , Ames Gregory , Markason David , Radau Skip
Published: February 2023

The Phased Array Mirror, Extendible Large Aperture (PAMELA™) technology has been developed to answer the need for large aperture active and adaptive optical reflector systems1,2. The PAMELA system consists of a large reflector made up of smaller, hexagonal segments which utilize piston sensors on each of the segments. These are non-contacting, inductively-coupled edge-sensors which measure the relative piston displacement between adjacent segments. A wavefront sensor provides the tilt information for each segment.
Edge-matched segmented secondary mirrors for IR adaptive optics
Authors: Gleckler Anthony D. , Angel Roger , McCarthy Don
Published: February 2023

Use of adaptive secondary mirrors for astronomical telescopes can have advantages over the typical adaptive optics system which use an adaptive element at a pupil relay position. The adaptive secondary replaces an optical element that already exists; therefore no additional pupil relay optics, which reduce system throughput, have to be inserted in the beam. Only one additional optic is needed between the imaging system and the primary mirror: a dichroic beamsplitter which sends the visible light to the wavefront sensor and the IR radiation to the imaging system. The ramifications of placing the adaptive element at the secondary are discussed. Also, existing telescopes can be easily retrofitted with a new secondary mirror, making installation simple.
A Compact, Solid-State Laser for Generation of A Mesospheric Sodium Guide Star*
Authors: Jeys T. H. , Wall K. F.
Published: February 2023

A diode-pumped Nd:YAG laser source of long pulse length, sodium-resonance radiation is being developed for the purpose of generating a guide star in the earth's mesospheric sodium layer for astronomical adaptive optics. This laser will be similar to the two other laser sources of sodium resonance radiation previously developed at Lincoln Laboratory, one which produced as much as 0.6 J of sodium resonance radiation at a 10-Hz repetition rate and another which produced as much as 24 mJ at a 840-Hz repetition rate.1 As in the previous laser sources, the sodium resonance radiation will be generated by sum-frequency mixing the output of a 1.064-μm Nd:YAG laser with the output of a 1.319-μim Nd:YAG laser (Figure 1). By operating the Nd:YAG lasers at wavelengths very close to the peak of their tuning curves as shown by the arrows in Figure 2, it is possible to match the wavelength of the sum-frequency radiation to that of the sodium D2 absorption wavelength.2 The laser system presently being developed will use diode lasers (rather than flashlamps) to pump the Nd:YAG (Figure 3). Diode laser pumping offers several advantages over flashlamp pumping including lower thermal loading of the Nd:YAG which results in improved beam quality, greater control over the temporal pulse shapes for improved sum-frequency mixing efficiency, and of particular importance for astronomical sites, greater electrical to optical efficiency, less heat generation, and less electrical noise generation.
The last generation of the SAM products, the SAM 241
Authors: Gaffard Jean-Paul , Jagourel Pascal , Peysson Jacques
Published: February 2023

The last generation of the SAM products is carrying out. The SAM 241 is planned to have a better optical surface and to be able to be repared.
Adaptive optics for high resolution imagery: optimization of corrections
Authors: Gaffard Jean Paul , Gosselin Patrick , Ledanois Guy
Published: February 2023

The poster defines the concept of optimized modal correction for adaptive optics systems. The objective beeing to achieve the best image quality versus the disturbances to be corrected and the level of light coming from the observed object.
Stacked array mirror technology improvements in laserdot
Authors: Peysson Jacques , Jagourel Pascal
Published: February 2023

The first mirror involving this stacked array technology was the 52 actuator adaptive mirror1 dedicated to the "COME ON PLUS" project2. It was built in 1990 and was an experimental achievement; our aims were: - to get about 50 actuators on a 70 mm aperture and it was not possible with the previous technology used for the 19 actuator mirror of the "COME ON" project3, - to get a cheaper technology, - to be able to extrapolate this technology to a few hundred actuator mirrors.
Miniature sources of subnanosecond 1.4 - 4.3-μm pulses with high peak power
Authors: Zayhowski J. J. , Wilson A. L.
Published: February 2023

Microchip-laser-pumped optical parametric generators have been packaged in 10-cm-long × 2.5-cm-diameter stainless-steel cans. These devices convert the 1.064-μm output of the laser into radiation at preselected wavelengths between 1.4 and 4.3 μm with quantum efficiencies >40%, resulting in mid-ir pulses of <200-ps duration with peak signal powers >140 kW. The optical head includes a heater that can be used to temperature tune the devices over several 10s to 100s of nm.
Scaling Procedures for Specifying Color Appearance
Authors: Gordon James , Abramov Israel
Published: February 2023

The world around us is often brightly colored. For various reasons it may be necessary to specify these colors precisely. One way is to describe each color in terms of the mixture of three primaries needed to match it. But this tells us only about equivalences and not about appearance. Furthermore, colorimetric matches remain stable even though appearances can change drastically with viewing conditions (1;2). We propose that hue and saturation scaling can be used to specify appearance precisely and reliably. The general techniques have been described earlier (3-5). We have examined several methodological variants to find one that is easily and reliably used, obtained "standard" functions from large groups of subjects under a variety of viewing conditions, and have tested the applicability of the technique with untrained observers. We have also used multidimensional scaling (MDS) (6;7) to derive uniform appearance diagrams (UAD) from the scaling data; from these spaces we have derived discrimination functions.
Color Appearance: The Roles of Chromatic Adaptation and Contrast
Authors: Shevell Steven K.
Published: February 2023

The color appearance of a particular light is very difficult to specify. The perceptual attributes of color vision — hue, saturation and brightness — are determined by both the light itself and the characteristics of other lights nearby. This has been known for nearly 150 years (Chevreul, 1839) but remains a fundamental problem in color vision. A related observation is that lights perceived as distinctly different colors when viewed in isolation can appear the same color when presented in a complex stimulus field. Thus by varying adaptation and contrast, (1) a single light can appear many different colors and (2) a single color percept can be achieved with various lights that appear different from each other when seen alone.
Color Naming of Near-Threshold Monochromatic Increments on a White Background
Authors: Drum Bruce
Published: February 2023

Most conventional models of suprathreshold color vision1,2 specify that, for neutral adaptation conditions, short-wavelength (S) cones signal blueness and short-wavelength redness, middle-wavelength (M) cones signal greenness and yellowness, and long-wavelength (L) cones signal long-wavelength redness and yellowness. A notable exception is Ingling and Tsou’s model3, in which M cones assist S cones with the blueness signal.
Calculation of Metameric Reflectances
Authors: Worthey James A.
Published: February 2023

Object-color metamerism becomes visually apparent if two objects match under one light, but not under a second. In the present paper, a method is derived by which metameric object colors can be calculated, given the light under which they are to match, and the light under which they are to mismatch. The method is presented primarily as a practical guide to creating or avoiding metamerism, but may have theoretical implications related to color constancy.
Color Appearance Problems in Motion Pictures and Television
Authors: DeMarsh LeRoy
Published: February 2023

In the context of motion picture and television applications, the term color appearance refers to how the picture looks, as opposed to it's measured or predicted physical characteristics. Most published studies of color reproduction problems concentrate on these physical factors. Indeed, many engineers seem to feel that color reproduction is a trivial problem-- just read a standard text on colorimetry and one has it all. Television is often cited as an example of one of the more successful applications of colorimetry. The author feels, that while application of colorimetric methods certainly played an important role in the development of television, the system works despite rather than because of "colorimetric theory".
80% Nonlinear Conversion Efficiency: When?
Authors: Byer Robert L.
Published: February 2023

Improvements in the efficiency of cw second harmonic generation (SHG) and cw optical parametric oscillation depend on the ratio of the nonlinearity to the loss in the nonlinear medium. External resonant SHG in monolithic lithium niobate crystals has now reached 69% conversion efficiency. Progress for SHG to the ultraviolet in barium borate and for cw OPO operation will be reviewed.
Air-Cooled Noble Gas Ion Lasers Operating Properties, Construction Techniques and Applications
Authors: Jarrett S.M.
Published: February 2023

In the early 1970's, a U.S. laser manufacture introduced a low power, air-cooled scientific argon ion laser. This laser was applied in the reprographics industry to color separators by manufacturers overseas within the next few years. Later, the same type laser was applied to high speed computer printers. By today's standards, these were primitive lasers. Their lifetime was not long, their power low and they required periodic maintenance. The lasers were fragile as well. Despite these drawbacks, these air­cooled lasers had some very desirable properties. As opposed to other ion lasers, they required no water cooling. Their power requirements were modest and the lasers and associated power supplies where small. They also operated in the blue-green with the superb optical properties and noise performance of low power gas lasers such as He-Ne.
Second harmonic generation from diode lasers in KTP waveguides1
Authors: Roelofs M. G. , Laurell F. , Bierlein J. D.
Published: February 2023

Segmented optical waveguides in KTiOPO4 were coupled to single mode diode lasers for blue light generation using QPM. The KTP waveguide consists of an ~4 μ periodic domain-inverted array of Rb/Ba diffused and non-diffused areas. This grating produces a narrow Bragg peak in reflected light at a specific wavelength. The reflected light was used to lock the diode laser, forcing it to remain narrow-band even in the presence of reflected light from the end faces of the waveguide. Temperature tuning of the KTP brought the SHG peak into coincidence with the Bragg-locked laser, with 5 °C bandwidth. The blue power obtained at 422 nm was 0.3 mW for a 5 mm long waveguide, using 113 mW IR at the focusing objective, and with 39 mW IR emerging from the waveguide. This technique eliminates the need for an optical isolator between diode and waveguide.
Perspective of GaN/GaAIN based ultra-violet/blue lasers
Authors: Amano H. , Akasaki I. , Itoh K. , Murakami H.
Published: February 2023

In order to realize compact and high density optical and electro-optical storage system, the demand for the fabrication of compact short wavelength light emitting devices such as light emitting diode(LED) or laser diode(LD), especially compact ultra-vioIet(UV)-LD or blue-LD is increasing.
Periodically-poled Lithium Niobate Crystals for Efficient Frequency-Doubling
Authors: Jundt D. H. , Fejer M. M. , Byer R. L.
Published: February 2023

In periodically poled LiNbO3, first order quasi-phase-matching (QPM) allows nonlinear interactions between waves polarized along the z-axis, for which the largest nonlinear coefficient d
eff
= 2d
33
/ π = 20.9 pm / V can be used, leading to 15 times larger conversion SHG efficiency per unit length compared to birefringent phase-matched interactions. The periodicity of the inverted ferroelectric domains must equal twice the coherence length of the nonlinear interaction. Fig. 1 shows the required period vs wavelength for SHG using d33.
Narrow Band Iso-Index Filters for Blue-Green Laser Communications
Authors: Belt Roger F. , Randles Mark , Creamer John , Stafsudd Oscar M.
Published: February 2023

Communications through the 440-470nm water transmission window requires a laser, a narrow band high field of view filter, and an appropriate detector. Polarization interference filters offer very narrow transmission bands, wide angular field of view, and tuning capability. The Lyot-Ohman, Solc, various hybrids, and recent designs are powerful examples of technologies employing common single crystals of quartz, calcite, or ADP. The superior iso-index filter (no = ne at a particular λ) is potentially the most useful. Materials for iso-index filters are not common since they must be stable single crystals, high quality, and usually involve mixed ions in an isomorphous structure. The research group at UCLA has shown that β"-Al2O3 fulfills these conditions within the Na-Ag system . However, β"-Al2O3 does not melt congruently and large single crystals are not attainable readily. An alternate superionic conductor, β-Al203, behaves similarly and can be grown as sizeable (1 × 6 inch) boules.
Investigation of the Compact S2 Vapor Blue-Green Laser
Authors: Jun-hua Yu , hua Zhang Zhong , hua Zhang , wei Zhu Zhong , guang Ma Zu
Published: February 2023

The properties of diatomic sulfur and the characteristics of S2 potential curves

B
3

Σ
u
−

−

X
3

Σ
g
−

make it possible to lase in S2 vapor by laser pumping or electric discharge pumping[1]. The S2 laser is efficient, of low pumping threshold and near continuously tunable over a wide spectral range.
Characteristics of ZnSe Light Emitting Diodes as a Function of Temperature
Authors: Guan Y. , Calhoun L. , Park R. M. , Zory P. S.
Published: February 2023

Blue light emitting devices are of special value in optical recording, information processing, display and undersea applications. Recently, ZnSe has been shown to be a promising material for making such devices with reports of pulsed ZnSe based diode lasers at low temperature [1] and light emitting diodes (LEDs) at room temperature (RT) [2][3]. However, efficient and reliable operation of these device types at RT has yet to be demonstrated. In this work, we study the temperature dependence of the output spectral features and current-voltage (I-V) relations of ZnSe LEDs. The results may prove useful for developing efficient/reliable blue LEDs and lasers.
Second Harmonic Generation and Degradation in Critically Phase Matched KnbO3 Using Diode Pumped, Q-Switched ND:Lasers
Authors: Seelert W. , Kortz P. , Rytz D. , Zysset B. , Ellgehausen D. , Mizell G.
Published: February 2023

Efficient requency doubling of low power diode pumped Q-switched Nd lasers requires frequency doubling crystals with high nonlinear coefficients, such as KTiOPO4 (KTP) (1), MgO:LiNbO3 (2,3), and KNbO3 (4,5).
A Novel Thermal Poling Technique for Fabricating QPM SHG Structures in X-cut Lithium Tantalate
Authors: Rubino R.A. , Bossi D.E. , Farina J.D.
Published: February 2023

We report a novel laser–assisted thermal poling technique for producing quasi–phase–matched (QPM) structures in planar x–cut Lithium Tantalate. As a proof of concept, low loss annealed proton exchanged (APE) waveguides were subsequently fabricated in these structures in order to demonstrate efficient second–harmonic generation (SHG) of blue light. Though others [1,2], have demonstrated higher QPM SHG conversion efficiencies in z–cut LiNbO3 and LiTaO3, we believe this process for x–cut material shows great promise for achieving higher SHG efficiencies. Furthermore, this process is compatible with the preferred crystallographic orientation for on-chip integration of IO (integrated–optic) devices such as high quality intensity modulators.
Simultaneous Blue and Green Second Harmonic Generation in Quasi-Phase Matched LiNbO3 Waveguide
Authors: Cao Xiaofan , Srivastava Ramakant , Ramaswamy Ramu V.
Published: February 2023

We report the first simultaneous quasi-phase matched (QPM) generation of blue (433 nm) and green (532nm) light by second harmonic generation in LiNbO3 channel waveguides.
Compact Raman Shifter
Authors: Gakhovich D. E. , Grabchikov A. S. , Orlovich V. A. , Dvornikov S. S.
Published: February 2023

An opportunity to concentrate the energy of scattered light in the one Stokes component of the stimulated Raman scattering (SRS) exists both for the forward and backward scattering [1,2]. The regime of backward SRS CBSRS5 has an advantage over the forward one due to the phase conjugation of the backward wave [3].
Compact blue-green lasers for future optical disk systems
Authors: Kubota Shigeo , Oka Michio , Masuda Hisashi
Published: February 2023

Diode-pumped, intracavity-doubled Nd:YAG, Nd:YVO4 green lasers, KTiOPO4 (KTP) sum frequency mixing, KNbO3 resonant ring doubler, periodically-poled KTP and LiNbO3 waveguide blue lasers, and IIVI blue laser diodes are promising sources for future 4 to 5 time pit density optical disks. Although the blue diode (460nm) is expected to reduce the intersymbol interference in read out signal from higher density optical disks, considering its probable beam aspect ratio, astigmatism, and the spectral sensitivity of a Si PIN photodetector, at least 5mW room temperature cw output will be required for its future application. Efficient blue harmonic generation of Ti:Sapphire lasers in a periodically-poled LiNbO3 waveguide and in a Cerenkov-radiation mode Ta2O5/KTP waveguide were also demonstrated. Their efficient stable coupling with a diode will be next key issue. Only applications of bulk nonlinear frequency conversion to actual optical disk systems have been demonstrated so far.
Imaging and Analysis of Semiconductor Surfaces with a Blue-Green Laser Scanning System
Authors: Worster Bruce
Published: February 2023

A system to provide 3-D images of submicron surface structure, composition, and defects on semiconductor wafer surfaces using a multiwavelength blue-green laser is described.
Short Wavelength Gas Lasers — Future and Applications
Authors: Silfvast William T.
Published: February 2023

An overview of short wavelength gas lasers will be presented including a summary of their characteristics, new developments in the field, and existing and potential future applications.
Pairwise Visible to UV Up-Conversion in Ho3+ and Tm3+ Doped CsMgCl3
Authors: Gharavi Ali , McPherson Gary L.
Published: February 2023

Up-Conversion is observed at 11 K when 1G4(D) state of Tm3+ and 5F5(D), 5F4(E), 5F3(F), 5F2(G) and 3K8(H) states of Ho3+ are pumped. These states absorb between 655 and 450 nm. The dynamics and pathways are studied which reveal a pairwise energy transfer between distinct pairs of Ho3+ or Tm3+ in crystals.
Non-uniformity of the Phase Matching Angle in Flux Grown KTP Crystal
Authors: Sasaki Takatomo , Miyamoto Akio , Nakai Sadao , Yokotani Atsushi
Published: February 2023

We grew KTP crystals of which size is over 8.5 cm in the c-axis from flux, and measured distribution of refractive indices which affects on the phase matching angle in the grown crystal. As a result, we have found that the phase matching angle in the crystal changed considerably corresponding to the change in the refractive indices. As the refractive indices of KTP crystal grown by flux change due to the growth condition, it seems to be difficult to determine the phase matching angle precisely.
Self-Frequency-Doubling laser crystal Nd:ß-BaB2O4
Authors: Ebihara T. , Matsuoka Y. , Toratani H. , Lin Liu
Published: February 2023

A self-frequency-doubling crystal, Nd1-xYxA13(BO3)4 (NYAB) and Nd:MgO:LiNbO3, is a crystal which combines laser properties and nonlinear optical properties. We report a new self-frequency-doubling crystal Nd:ß-BaB2O4.
Upconversion Fiber Lasers
Authors: Grubb Stephen G.
Published: February 2023

Over the past two years, the uniform, high-intensity pumping advantages of the single-mode fiber geometry have been realized in demonstrating several new visible upconversion laser transitions. To date 11 different CW, room-temperature visible upconversion laser/pumping combinations have been demonstrated with visible laser powers of up to 200 mW. Perhaps the most dramatic demonstration of an upconversion laser to date was the CW, room-temperature operation of a Pr3+-doped ZBLAN fiber at 5 visible wavelengths1. An additional advantage of the fiber geometry for upconversion lasers is that the fiber laser is the only laser geometry where the pump spot size and resonator length are decoupled. This extra degree of freedom is extremely important in the upconversion process where the ground-state absorption (GSA) and one or more excited-state absorptions (ESA) must be balanced in order to efficiently populate the upper laser level. For example, the three-photon pumped Tm3+ upconversion laser discussed in this paper would not be possible in a Tm3+-doped crystal due to the extremely weak GSA. The long resonator lengths possible in fiber lasers also allow the minimization of concentration quenching effects while distributing the absorption to facilitate heat removal.
Fifty-Megabit Per Second Random Modulation of 15-mW Blue Coherent Radiation Using Sum Frequency Generation from KTiOPO4
Authors: Oka Michio , Minoya Yasushi , Kubota Shigeo
Published: February 2023

Fifty-mega bit/s random modulation of 15-mW blue output from KTiOPO4 was obtained through sum frequency generation between a diode-pumped Nd:YAG laser and a diode.
Waveguide QPM-SHG-Modulator
Authors: Tatsuno K. , Ito K. , Helmfrid S. , Makio S.
Published: February 2023

A Novel intensity modulator for second harmonic waveguide laser is demonstrated. Noise caused by spectrum broadening in a diode-laser direct-modulation schem is avoided by using the electro-optic effect to modulate the phase mismatch in the frequency-doubling process.
Waveguides Fabrication in KTP by Ion-Exchange from Metal-Organic Tl Compositions
Authors: Beklemishev V. B. , Buritskii K. S. , Dianov E. M. , Maslov V. A. , Chernykh V. A. , Shcherbakov E. A.
Published: February 2023

Since its invention by Bierlein and coworkers, application of the waveguides in a KTP (KTiOPO4) crystal for the SHG in the blue-green spectral range is very promising [1,2].
Second harmonic generation in field poled, quasi-phase-matched, bulk LiNbO3
Authors: Burns W. K. , McElhanon W. , Goldberg L.
Published: February 2023

Quasi-phase matched (QPM) second harmonic generation (SHG) and other nonlinear processes have recently been obtained in LiNbO3, LiTaO3, and KTP by achieving periodic domain reversal by a variety of techniques.
Semiconductor Lasers for Frequency Conversion
Authors: Waarts Robert G.
Published: February 2023

Laser diode sources are presently used in many applications because of their advantages of high efficiency up to 60 %, compact size, reliability and cost.
Frequency Doubled and Q-switched Nd:YVO4 Laser
Authors: TAIRA Takunori , KOBAYASHI Takao
Published: February 2023

This paper describes a highly efficient and compact Nd:YVO4 laser. In CW operation, a single-mode output of 95 mW and a multimode output of 435 mW were obtained with a 1W laser-diode pump. Using a KTP crystal in the laser cavity, 105 mW of green light was generated. A Q-switched pulse with a peak power of 230 W and pulse width of 8 ns was obtained with the intracavity KTP crystal used as both the Q-switch and the frequency doubler.
Flash lamp pumped Cr,Nd:LSB laser with 6,3% efficiency
Authors: Kutovoi S. A. , Ageyev A. Yu. , Khait V. L. , Kuzmin O. V. , Mikhailov V. A. , Hinz A. , Pfeifer E.
Published: February 2023

This paper reports the results of laser experiments with active elements manufactured of a Cr3+, Nd3+:LaSc3(BO3)4 (Cr,Nd: LSB) crystal with high Nd concentration 1.3 × 1021 cm-3 and sensitized by 0.5 × 1020 cm-3 Cr ions.
On the accuracy of rectangular-pulse deconvolution of long-pulse lidar profiles
Authors: Gurdev L. L. , Dreischuh T. N. , Stoyanov D. V.
Published: February 2023

If a lidar system emits long rectangular sensing pulses, the lidar return signal F(t) at the moment t after the pulse emission will have low resolution and will be described by the equation where c is the speed of light, Φ(z) is the maximum-resolved (δ-pulse) lidar profile, and t is the rectangular-pulse duration; the height of the rectangular-pulse shape is assumed to be equal to unity. In order to improve the lidar resolution, we have developed earlier1,2 a simple recurrence algorithm to invert Eq. 1 with respect to Φ(z), namely where Φ(z) is supposed to be known in some cτ/2-long initial spatial interval and F′(t) is the first derivative of F(t). Be sides simplicity, another feature of this algorithm is that it is not so sensitive to noise as compared to some other deconvolution algorithms we have developed.2 In this work we estimate the error caused by rectangular-pulse approximation of various sensing laser pulses in order to outline the conditions under which this approximation is acceptable, and, consequently, useful because of its advantages.
Low threshold current strained InAlGaAs/AlGaAs quantum well lasers grown by metalorganic vapour phase epitaxy
Authors: Vermeire G. , Vermaerke F. , Van Daele P. , Demeester P.
Published: February 2023

The impact of strain on the characteristics of III/V semiconductor laser diodes has already been demonstrated several times. InGaAs/GaAs strained quantum well (QW) lasers exhibit low threshold cur rents, high quantum efficiencies, high modulation bandwidths, and show improved reliabilities.1 Since 1991 InAlGaAs has been introduced as a new quaternary compound to realise strained QW lasers for a wavelength range between 750 and 900 nm.2,3 This wavelength domain related to GaAs/AlGaAs lasers offers several applications such as solid-state pumping, Cd lasers, etc. Compared to AlGaAs/AlGaAs QWs, the introduction of indium into the QW should result in lower threshold current densities (due to a strongly modified energy bandstructure) and improved reliabilities (due to lattice hardening).
Soliton self-frequency shift for pulses with a duration less than the period of molecular oscillations
Authors: Herrmann J. , Nazarkin A.
Published: February 2023

Since the observation of the soliton self-frequency shift,1,2it has been known that the Raman effect has a profound impact on soliton propagation for solitons with durations less than a picosecond. According to the theory developed by Gordon,2under the condition that the soliton duration τpis much longer than the period of molecular oscillations

T
R

=
2
π

Ω
R

−
1

a soliton experiences a self-frequency shift, which is proportional to

τ
p

−
4

. On the other hand, recently, in a number of experiments on soliton transmission and amplification in doped fibers,3solitons with durations as short as 20 fs were observed. Since the characteristic period of molecular oscillations in silica glass is about Tr≃ 80 fs (corresponding to the Stokes frequency shift of ΩR≃ 440 cm-1), in these experiments the condition τp< TRis fulfilled. This implies a qualitatively new regime of stimulated Raman scattering (SRS) in which the spectrum of the initial pulse contains already both Stokes and anti-Stokes spectral components.4In this situation, the conditions for the validity of the theoretical model developed in Ref. 2are not fulfilled, and an adequate analysis is required.
Transformation of linear chirp through cascaded optical second-order processes
Authors: Danielius R. , Dubietis A. , Piskarskas A. , Tamošauskas G.
Published: February 2023

Ultrashort pulse self-modulation originating from cascaded second-order processes has been considered in a number of recent studies.1,2 Two beam interaction resulting in self-diffraction has been shown to take place as well.3,4
Phase matched gratings for enhanced forward degenerate four wave mixing
Authors: Giorgetti E. , Lambkin P. , Li Qu , Sottini S. , Grando D. , Blau W.
Published: February 2023

The coupling between electromagnetic waves propagating in a nonlinear medium gives rise to a number of interesting phenomena. Specifically, the transfer of energy between two interfering laser beams and the accompanied generation of new beams (four wave mixing)1 has been demonstrated in a wide class of materials. When two coherent pump waves intersect at a narrow angle in a Kerr medium, the resulting interference pattern perturbs the local refractive index and induces a grating. The writing beams scatter from the grating and can generate new diffracted beams. This process is known as forward degenerate four wave mixing (FDFWM). The first-order diffracted beam from each pump appears in the path of the other. The strongest spatially distinguishable order is the second. The second-order diffracted beams are not phase matched over significant propagation distances and so the energy associated with these orders is small. However, by introducing linear spacer layers into the nonlinear medium a grating of gratings can be formed as shown in Fig. 1. This permits phase matching, thus enhancing the diffracted side lobes.