bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrinsic and Induced Anisotropy of the Nonlinear Absorption in Strained [110]-Oriented Multiple Quantum Wells.
Authors: Huang X.R. , McCallum D.S. , Smirl Arthur L. , Sun D. , Towe E.
Published: February 2023

Recent theoretical studies1,2 and experimental measurements3,4,5 have shown that there is a large inherent anisotropy in the absorption coefficient of excitons in biaxially strained quantum wells (QWs) grown on (110) surfaces. Due to the symmetry properties of the excitonic wavefunctions, there is no such anisotropy in the absorption spectra of unstrained or biaxially strained QWs grown on (100) or (111) surfaces. Such an anisotropy in the absorption coefficient can be exploited to construct optical switches or modulators. For example, a contrast ratio of 330:1 between on and off states has been achieved in uniaxially strained [100]-oriented QW structures using 100 wells.6 In this work, we present the first measurements of optically-induced and intrinsic anisotropies in the nonlinear absorption of a biaxially strained, [110]-oriented MQW structure using picosecond pump-probe and differential transmission spectroscopy. We also demonstrate how the polarization rotation associated with these anisotropies can be used to construct an all optical on/off switch or modulator with a contrast ratio of 25:1 using only 50 wells.
Enhanced intersubband χ3 in coupled InGaAs/AlGaAs multiple quantum wells
Authors: Rabinovich W. S. , Beadie G. , Katzer D. S.
Published: February 2023

Intersubband transitions in quantum wells have been actively studied in the past several years both as “testbed” systems for quantum mechanics and for their practical applications. The ability to tailor the structure of these materials to produce systems with desired properties, as well as the very large dipole moments exhibited in the mid and near infrared, leads to a great versatility for such applications as detectors[1], lasers[2] and nonlinear optical materials[3].
Microcavity Semiconductor Lasers: Parameter Evaluation and Performances
Authors: Bava G. P. , Debernardi P.
Published: February 2023

Microcavity lasers have been shown to be promising devices owing to their characteristics such as very low threshold current, large modulation bandwidth, noise properties, etc. [1, 2, 3].
Symmetry Breaking in Vertical-Cavity Semiconductor Lasers
Authors: Woerdman J.P. , van Doorn A.K. Jansen , van Exter M.P.
Published: February 2023

It seems fair to say that the polarization behavior of semiconductor Vertical-Cavity Surface-Emitting Lasers (VCSELs) is not understood on a fundamental level. In spite of the nominal anisotropy of a VCSEL the polarization is usually reported as being linear, but not very stable. Most authors associate this behavior with native anisotropies due to imperfect device fabrication although also intrinsic nonlinearities of the gain medium have been put forward for explaining the linear polarization. We are involved in a detailed study [1-4] of the various anisotropies of a VCSEL, their interplay, their manipulation and the consequences thereof for the VCSEL polarization. We have found experimentally that the polarization of a practical VCSEL can be largely explained as a consequence of linear anisotropies; nonlinearities play at most a minor role.
Size Reduction of Microdisk Injection Lasers for Spontaneous Emission Control
Authors: Baba T. , Kihara M. , Watanabe R.
Published: February 2023

Spontaneous emission control1) is of great interest since it provides novel high performance in laser diodes, e.g., thresholdless operation and high speed modulation without relaxation oscillation. It is realized in a microcavity whose volume V satisfies single mode condition
V≦λ4/(4πn3Δλ), where n is the effective refractive index of cavity and Δλ is the spectral width of atomic radiation. It is easier in microdisk lasers2) than in VCSELs to realize this condition since vertical cavity size of microdisk lasers is easily reduced by the strong optical confinement into thin disk layer. In this study, we demonstrate injection devices of 3 – 10 μm in diameter and 0.2 μm in disk thickness, which are close to the single mode condition. We compare the diameter dependence of lasing characteristics between experiment and theory, and discuss the potential of this kind of device for spontaneous emission control.
Cavity-Polariton Formation and Relaxation Dynamics in Semiconductor Microcavities
Authors: Berger J.D. , Hallstein S. , Rühle W.W. , Lyngnes O. , Khitrova G. , Gibbs H.M. , Kira M. , Jahnke F. , Koch S.W.
Published: February 2023

Semiconductor microcavities are of inherent physical importance for their ability to dramatically alter the emission properties of solid states. Of particular interest is the strong coupling regime, characterized by a cavity-exciton coupling which dominates over irreversible decay mechanisms. This regime has been the focus of abundant activity since the first observation of the normal mode splitting in a semiconductor microcavity.1 Recent work has elucidated cavity polariton emission properties in both the linear2 and nonlinear3,4,5 regimes.
Fluorescence lifetimes of Oriented Molecules in Microdroplets
Authors: Barnes M. D. , Lermer N. , Whitten W. B. , Ramsey J. M. , Arnold S.
Published: February 2023

Over the last several years there has been considerable interest in the properties of atomic resonance fluorescence in an optical cavity with a primary dimension comparable to the relevant transition wavelength.1 In particular, there has been great interest in the realization of strong atom-cavity coupling2 and the suppression of spontaneous emission into "free-space" modes. However, an important but poorly understood issue relevant to low- or zero-threshold condensed phase optical devices is the nonradiative coupling of the emitting species to a thermal bath. Unlike experiments involving dilute atomic beams where the transition is well defined and broadening is negligible, coupling to a thermal bath induces spectral broadening which is usually much larger than the cavity resonance width and may often exceed the cavity mode spacing. Interesting examples of such systems are solvated dyes whose condensed phase dynamics are well known and characterized. To date, several studies have been made on fluorescence properties of solvated dyes in microcavities,3,4,5 however additional complexities such as spatial and orientational averaging have obscured to some extent the connection between radiative and nonradiative processes in such systems. We discuss the observation of spontaneous emission rate modification (both enhancement and apparent suppression) for molecular species in a microcavity where both the molecular position and transition moment orientation are well defined.6 These experiments serve as an interesting test case of molecule-cavity systems in which the emitting species is nonradiatively coupled to a thermal bath.
Wavelength Stabilization and Trimming Technologies for Vertical Cavity Surface Emitting Lasers
Authors: Koyama F. , Iga K.
Published: February 2023

Multi-wavelength integrated light sources are key devices for future large scale wavelength division multiplexing (WDM) systems. One of important issues is precise control of lasing wavelength of each element. Large temperature sensitivity of lasing wavelength is also a remaining problem. Recently, wavelength stabilization of semiconductor lasers using strain was demonstrated [1]. Also, wavelength trimming technique was proposed for post-process precise control of wavelength [2].
Multiple Quantum Well Passive Modelocking of NaCl Color Center Laser
Authors: Islam M.N. , Sunderman E.R. , Bar-Joseph I.
Published: February 2023

We passively modelocked a NaCI color center laser (CCL) by using multiple quantum well (MQW) saturable absorbers to produce pulses around 260fsec. The laser is an all solid-state source lasing around 1.6-1.7μm and formed in a single cavity. Silberberg, et al. [1], first modelocked a semiconductor diode laser using MQW’s, and Haus and Silberberg [2] theorized that the fast saturable absorber component plays a major role in the formation of their ~ 1.5psec pulses. This fast absorber component results from MQW absorption bleaching by short-lived excitons formed near the band gap of the MQW. The excitonic lifetime of 200±30fsec measured in our MQW’s [3] is comparable to our pulse widths. Consequently, the fast saturable component dominates the pulse shaping and may limit the pulse width in our experiments.
Interlayer Transport of Photoexcited Electrons in Type II Gallium-Arsenide/Aluminum-Arsenide Multi-Quantum Well Structures
Authors: Saeta P. , Fischer R.J. , Greene B.I. , Spitzer R.C. , Wilson B.A.
Published: February 2023

Optical pump-probe experiments on bulk GaAs and conventional type I GaAs/GaAlAs multi­quantum well structures (MQWS) have determined the time scales on which photoexcited carriers (1) attain thermal equilibrium among themselves, (2) scatter out of the zone-center Γ-valley to accessible X- or L-valleys, (3) relax their excess energy to the lattice, and (4) recombine.(1-3) In most cases, carrier thermalization (via carrier-carrier collisions) and intervalley scattering occur in less than 100 fs, lattice heating in picoseconds, and recombination in nanoseconds to microseconds and longer. In these direct gap systems, photoexcited electrons and holes remain in the same layer or region of the crystal. In type II structures, the highest valence band occurs in one layer and the lowest conduction band in the other; excited carriers spatially segregate, one carrier remaining in the narrower bandgap material, the other transferring to the lower energy states occurring in the adjacent layer. We have determined that in a type II GaAs/AIAs MQWS having 8 monolayers of GaAs alternating with 25 monolayers of AlAs photoexcited electrons transfer from the Γ-valley of the GaAs layers to the X-valley of adjacent AlAs layers within 100 fs.
Temperature Dependence of Emission Wavelength in 1.3 μm GaInAsP/InP GRIN-SCH MQW Laser Diodes Grown by MOCVD
Authors: Kasukawa A. , Matsumoto N. , Murgatroyd I. J. , Fukushima T. , Kashiwa S. , Okamoto H.
Published: February 2023

Quantum well (QW) lasers operating in the long wavelength range (λ=1.3 to 1.55 μm) have been demonstrated or are expected to be superior to the conventional distributed feedback (DFB) lasers, in such aspects as (i) threshold current density (Jth)(1)(2), (ii) temperature dependence of Jth (the characteristic temperature, T0)(1), (iii) stability in polarization (TE polarization or TM polarization)(3), (iv) static and dynamic single mode oscillation, (v) spectral width under cw operation and under high speed modulation (4)(5), and (vi) upper frequency limit for direct modulation(6). Furthermore, the fabrication process for QW lasers is simpler since it does not involve the corrugation formation process necessary for DFB lasers. The aspects remaining for future study with respect to this comparison are the lifetime of the devices(10) and the temperature stability of the oscillation wavelength λ. As for the temperature dependence of λ, dλ/dT, DFB lasers exhibit a small value of dλ/dT = 0.8~1.0 Å/degree, which is determined by the temperature dependence of the refractive index of the semiconductor materials. On the other hand, little work has been done on the dλ/dT of QW lasers since the first report(7) on the multiple quantum well (MQW) laser made from GaAs-AlGaAs material described that the dλ/dT of this laser was equal to 4 Å/degree, which is determined by the temperature dependence of the bandgap energy Eg of the material.
Excitonic Optical Nonlinearity in Semiconductor Quantum Spheres
Authors: Hiroshima Tohya , Hanamura Eiichi
Published: February 2023

It is numerically confirmed that the third-order optical susceptibility χ(3)(ω;–ω,ω,–ω) is enhanced by the mesoscopically enhanced transition dipole moment of excitons in CuCl quantum spheres (QS's) but it is not in GaAs QS's and it is marginal for CdS QS's.
Compositional Dependence of the Quantum Confined Stark Effect in Quaternary Quantum Wells
Authors: Bar-Joseph I. , Zucker J. E. , Miller B. I. , Koren U. , Chemla D. S.
Published: February 2023

Quantum well modulators require strict control over the wavelength of the exciton transition in order to minimize insertion loss and maximize voltage sensitivity at the desired wavelength of operation. Within the quaternary material system In
x
Ga1−
x
As
y
P1−
y
, there are two parameters which can be varied in order to tune the bandgap: the thickness of the quantum well layer and its composition. Tuning the bandgap by means of well size alone is of limited usefulness since the rate at which the exciton energy shifts with field drastically decreases as well width decreases 1. In this paper, we demonstrate for the first time that the compositional flexibility of quaternary quantum wells can be used to obtain field-induced shifts larger than those obtainable in InGaAs quantum wells, yielding enhanced electroabsorption and electrorefraction. We show that quaternary devices can fill a serious need for quantum well optical modulators in the wavelength range 1.3 µm to 1.55 µm for optical communications.
Analysis of the quantum confined stark effect in GaSb/AlGaSb multiple quantum wells
Authors: Carr Elizabeth C. , Wood Thomas H. , Burrus Charles A. , Chiu T. H.
Published: February 2023

There has been much interest recently in the electric field dependence of the optical absorption in multiple quantum wells (MQWs). This phenomenon, known as the Quantum Confined Stark Effect (QCSE),[1] has many device applications, one of which is high-speed optical intensity modulators for fiber optic systems. Modulators were first demonstrated in the 0.8 µm wavelength region using GaAs/AlGaAs,[2] but more recently attention has shifted to InGaAs/InAlAs,[3] InGaAs/InP[4] [5] and GaSb/AlGaSb[6] material systems which operate near the optical fiber loss minimum at 1.55 µm. To understand these devices, Miller et al. developed a theory for the QCSE[1] that was in good agreement with their experimental data for GaAs/AlGaAs MQWs. The theory was also successfully applied to InGaAs/InP MQWs.[7] In this paper we extend that theory to GaSb/AlGaSb and compare it with our experimental data. Because of the sizable lattice mismatch of 0.65% between GaSb and AlSb, strain effects can become very important in GaSb/AlSb MQWs. We show that the use of AlGaSb barriers significantly reduces these effects.
Applications of Quantum Well Structures for Surface Emitting Lasers and Optical Switching Devices
Authors: Kyuma Kazuo , Kojima Keisuke , Nakayama Takashi
Published: February 2023

There has been increasing interest in optical computing for ultrafast information processing. To realize optical computing systems, there are several key devices, such as surface-emitting lasers and optical switching devices.
Γ-X Transfer in Tunneling through Single AlAs Barriers
Authors: Landheer D. , Liu H.C. , Buchanan M. , Stoner R.
Published: February 2023

When electrons tunnel through a single barrier of AlAs between GaAs contact layers there is a possibility of transfer from the Γ-conduction band to the X-band.1,2,3 The basic mechanism for Γ-X transfer based on the model of Liu 3 is shown in Fig. 1 along with Γ (solid lines) and X (dashed lines) conduction-band profiles for a 5.2 nm AlAs barrier. A Γ-electron can (1) tunnel through the entire structure without transfer, it can (2) transfer to the X-minimum at the first interface and propagate through the AlAs layer before transferring back to the Γ-minimum, or it can (3) transfer to the X-minimum at the first interface and propagate through the whole structure. The transfer at the interfaces is described by an interaction vertex VΓX or a coupling parameter α as described in Ref. 3. The process (2) is relatively unimportant at low applied potentials but becomes dominant above about 0.3 V where the Fermi energy has crossed the X-band in the AlAs.
Refractive Index Modulation in Selectively Contacted GaAs N-I-P-I Structures
Authors: Hsu T. Y. , Wu W. Y. , Efron U. , Schulman J. N. , Hasnain G.
Published: February 2023

A GaAs Nipi with selective contacts was used for refractive modulation characterization; this Nipi device has the alternative n- and p-doped thin layers at a total thickness of ≅ 0.68 μm and a doping concentration of n ≅ p ≅ 4×1018 cm-3. The selective contactings were grown in situ with the n-i-p-i structure by MBE technology. The distance between two contact electrodes is ≅ 0.7 mm and each electrode is measured at ≅ 1 mm in length. The active area of this device is, therefore, approximately 0.7 mm × 1 mm. The I-V measurement of this n-i-p-i device shows good diode characteristics. The refractive changes at various current levels were determined by using a Mach-Zehnder interferometer. An Ar+-laser pumped ring dye laser, which has a useful wavelength range from 8000 to 9000 Å, was used as a light source. The refractive index change was determined by the fringe shift of the interference pattern generated by the signal beam (which passes through the n-i-p-i device) and the reference beam. A train of current pulses at a few hertz was used to drive the n-i-p-i modulator and also eliminate the slow fringe drift due to environmental noises of the interferometric system. A positive refractive index change of Δn > 1.5 was recorded at an injection current level I < 50 mA at λ = 9000 Å, as shown in Figure 1. The above result of refractive index modulation is more than two orders of magnitude larger than the prediction from our theoretical calculation.1 This refractive index change is observed in the wavelength range from 8900 Å to 9050 Å. The measurement wavelength range was limited by the strong interband absorption at λ < 8900 Å, and by the cutoff lasing wavelength of the sty-9 dye used in our ring dye laser beyond λ > 9050 Å.
Photoreflectance Spectroscopy of InGaAs/GaAs Strained Superlattice Waveguides
Authors: Sonek G.J. , Dawson L.R.
Published: February 2023

In addition to quantum confinement [1], the effects of strain, resulting from the growth of lattice-mismatched materials, provide another means of tailoring the properties and performance of optoelectronic devices [2-6]. New properties for device applications, including birefringence and piezoelectric effects [7], are expected.
A New Wavelength Selective FIR Detector with High Gain and Low Dark Currents
Authors: Döhler G.H.
Published: February 2023

Some time ago a new FIR detector has been demonstrated by Levine, Choi, Bethea, Walker and Malik, which used the wavelength selective intersubband absorption and subsequent emission of electrons in a multiple quantum well (MQW) structure with an electric field applied in the direction normal to the layers /1/. A major drawback of this detector is the fact, that it is a majority carrier device. The photon-assisted field emission of electrons from the individual QW's causes positive space charge in the structure. In order to avoid a time- and optical-power dependent space charge, resulting in undesirable effects similar to those of space charge limited currents, rather high dark currents are required in order to maintain macroscopic neutrality in the system.
Optical Detection of Resonant Tunneling of Electrons in Quantum Wells
Authors: Livescu C. , Fox A.M. , Sizer T. , Knox W.H. , Miller D.A.B.
Published: February 2023

The investigation of vertical transport in superlattices (SL’s) and multiple quantum wells (MQW’s) has recently attracted much attention. Intense research was focused on basic quantum effects such as Bloch transport of electrons and holes in minibands,1 coherent and incoherent, resonant, sequential and Zener tunneling2 in double barriers,3,4 SL’s and MQW’s of GaAs/AlAs,5,6 GaAs/AlGaAs,7 and InGaAs/InP.2,8 In addition to the academic interest, the understanding of the mechanisms of escape from and travel through quantum wells is vital for the recently developed and constantly growing family of electro-optical devices using semiconductor quantum wells. Most of them are based on the quantum-confined Stark effect (QCSE), and they include bistable self­electro-optic effect devices (SEED’s), tunable detectors, electro-absorption modulators and optical logic elements.9 The basic unit of all of these is an epitaxially grown p-i-n diode, with the quantum well layers in the intrinsic region. By reverse biasing the diode, an electrical field is applied on the quantum wells, controlling its optical absorption spectrum. Since operating wavelengths are close to the excitonic absorption peaks, photoexcited charge is created in the quantum wells and is transported to the electrodes. The mechanisms by which this transport occurs are ultimately responsible for the intrinsic maximum speed or operating intensity of these devices.
Optical Evidence of Charge Accumulation in Double Barrier Diodes
Authors: Vodjdani N. , Costard E. , Chevoir F. , Thomas D. , Bois P. , Delaitre S.
Published: February 2023

Tunneling is one of the basic quantum mechanical phenomena which plays a key role in many ultra thin semiconductor devices. Besides their potential for applications, double barrier hetero­structures are also interesting for the understanding of tunneling-based transport processes (1) and their dynamics. Time-resolved photoluminescence (PL) has been used to determine the tunneling escape rate of electrons from a single quantum well through a thin barrier into a continuum (2) and to determine the electric field dependance of this tunneling rate (3).The charge accumulation in the quantum well can be estimated using magnetotunneling (4) or as recently demonstrated steady-state photoluminescence (5).
Output Coupler Effect on a Diode-Pumped Nd: Cr: GSGG Laser
Authors: Zhou Jie , Hwang In H.
Published: February 2023

Chromium and neodymium codoped gadolinium scandium gallium garnet (Cr: Nd: GSGG) rods were used for the continuous wave (CW) laser experiment with a diode laser as pumping source. TEM00 laser output up to 100 mW was obtained at 1.06 mm with 550 mW pumping. The rod lengths were 10 mm and 18 mm. The diameter of the rods was 3 mm. The slope efficiency of 29 % was obtained with 95 % output mirror. No thermally induced lensing and birefringence were observed at this power level.
Temperature Dependent Laser Performance of Tm, Ho Doped Crystal: Theory
Authors: Hwang In Heon
Published: February 2023

A model for a longitudinally end-pumped co-doped solid-state laser is developed and applied to Tm, Ho codoped laser to identify the temperature dependent laser performance. The simplified calculation shows that the slope efficiency of the Tm, Ho doped lasers does not depend on temperature. Also the threshold pump power dependence on the temperature is very weak.
High Resolution Spectroscopy
Authors: Jalufka Nelson W.
Published: February 2023

Water vapor is an important species in the earths atmosphere. It plays a major role in many atmospheric processes including weather, climate and atmospheric photochemistry. The distribution of water vapor in the atmosphere is highly variable and if we are to relate its variability to atmospheric effects, its spatial and temporal variability must be understood.

Remote measurements of water vapor distribution in the atmosphere frequently relies on differential absorption lidar (DIAL) techniques. These techniques require accurate spectroscopic data for the species of interest. These data include line position (wavelength) , absorption coefficients, pressure broadening parameters and pressure shift parameters. Temperature effects on these parameters is also important as it is more convenient to work with spectral lines which are relatively insensitive to temperature variations.

DIAL measurements must be made in a spectral region where the absorption cross sections have appropriate values for the density and measurement range of interest Optimum measurements are made in the range where the optical depth (one way) has a value near unity. To extend Dial measurements of water vapor into the stratosphere, where water vapor is less dense than in the troposphere, the water vapor band in the region of 940 nm is appropriate due to its stronger absorption.
Experimentally Determined Relationships Between Extinction at 3.4 μm and Liquid Water Content
Authors: Yee Young Paul , Bruce Charles W. , Pinnick R. G.
Published: February 2023

At wavelengths between 9 and 11 micrometers, a unique relationship (within relatively narrow bounds) has been predicted1 and verified experimentally2 for water droplet distributions having, effectively, a large particle radius cut off of less than 16 micrometers. This appears to be applicable to (at least) radiation fogs and is conveniently within a major atmospheric propagation "window" wavelength region. At. shorter wavelengths there is generally no single number representing the ratio of extinction coefficient to liquid water content for fogs. In this study, involving another IR propagation window, a 3.4 micrometer (HeNe, 1/2 mW) laser has been used as a probe source to investigate a possible extinction - liquid content relationship in this shorter wavelength atmospheric window region.
Remote Sensing of Atmospheric Turbulence by Utilizing Speckle-Turbulence Interaction and Optical Spatial Filtering
Authors: Holmes J. Fred , Lee Myung Hun , Sun Li Bo
Published: February 2023

Speckle-turbulence interaction has the potential for allowing single ended remote sensing of the path averaged strength of turbulence (structure constant,
Cn2) along the line of sight to a target. If a laser transmitter is used to illuminate a diffuse object in the atmosphere, the resultant speckle field generated by the object is randomly perturbed by the atmospheric turbulence as it propagates back to the location of the transmitter-receiver. Consequently, the variance of the received intensity contains information about the strength of atmospheric turbulence. Unfortunately, the fluctuations due to speckle and those due to the turbulence cannot be separated; and therefore the variance of the received intensity cannot be used very effectively to remotely sense the strength of turbulence. However, by optically spatial filtering the received field, the strength of turbulence can be determined over three or more orders of magnitude. This will allow remote sensing of
Cn2 over both horizonal and vertical paths with a relatively simple apparatus and has exciting implications with regard to global remote sensing of
Cn2 from aircraft or space.
Optical Measurements of Water Vapor Over The Gulf Stream
Authors: Goroch Andreas K. , Browell Edward , Marksen Ralph , Wilkerson Thomas
Published: February 2023

Optical propagation conditions in the mid-infrared wave lengths (3-5 micrometers) are determined by water vapor and aerosol concentrations, primarily by the former. In regions of varying surface conditions, water vapor can vary in a complex manner making analysis and forecasting of optical propagation difficult. The purpose of this experiment is to a) describe the variation of water vapor in a marine region characterized by varying surface conditions, viz, the north wall of the Gulf Stream and b) to demonstrate the utility of a differential absorption LIDAR (DIAL) system for remote sensing of water vapor variations.
Infrared Heterodyne and Diode Laser Absorption Spectrometers for Airborne Measurements of Stratospheric Species
Authors: Menzies Robert T.
Published: February 2023

Numerous atomic, molecular, and free radical species play important roles in the photochemistry of the stratosphere, affecting the stratospheric ozone layer, the temperature profile, and as a consequence modifying the transfer of radiation to and from the surface. Nearly all of these molecular and free radical species possess active infrared absorption bands which can be used for identification and measurement, at wavelengths which can penetrate long stratospheric paths without being absorbed by the major stratospheric constituents, such as ozone. Since it is not uncommon for these species to exist at mixing ratios of parts-per-billion, high sensitivity, long path absorption techniques are employed. Due to the low ambient pressure environment, the absorption lines of these species in the mid- and far-infrared are narrow, with halfwidths ranging from about 10−3 cm−1 to 10−2 cm−1. The ability of high resolution infrared laser techniques to resolve these lines provides the possibility of increased sensitivity and accuracy, which justifies the investment in high resolution IR spectroscopy and in new instrument development.
Spectral Pattern Recognition in IR Remote Sensing
Authors: Zachor Alexander S.
Published: February 2023

Spectral pattern recognition in IR remote sensing is the process of identifying an "event," usually the presence of a particular substance, from a spectrum produced or in some way influenced by the event. Ideally, the process will correctly classify all events of interest and reject all background, interference and noise events associated with the sensing process. It is a statistical problem, since the classes and/or their associated spectra are not unique. For example, a gas of interest may have a well-defined absorption coefficient signature, but can be present in varying amounts; its influence in an observed spectrum may also depend on concentration/temperature distributions along the line-of-sight.
Very High Sensitivity Spectroscopy using Tunable Diode Lasers
Authors: Reid John , Garside Brian K.
Published: February 2023

In recent years, tunable diode lasers have become widely used in the study of laboratory infrared spectra. The high resolution provided by the diode lasers is employed to obtain accurate line positions, and to a lesser extent lineshapes and linestrengths. While this type of research is now undertaken in many laboratories, few researchers are currently exploiting the potential of the diode lasers to provide very high sensitivity measurements in the infrared. In this paper, we describe diode modulation techniques which enable one to detect absorption coefficients as small as 10-9 cm-1. This sensitivity, combined with the tunability and resolution of the diode laser, allow one to perform a wide range of experiments relevant to atmospheric spectroscopy. In the laboratory one can detect very weak absorption lines in stable molecules [1], or investigate the spectra of unstable molecules such as free radicals [2]. The instrumentation is port able, and we have used it to make in situ field measurements on a wide range of gases and pollutants in an urban atmosphere [3]. Similar instruments have been flown in aircraft to monitor tropospheric CO concentrations, and balloon flights are planned to simultaneously determine stratospheric NO2 and NO concentrations [4].
Photofragmentation - Laser Induced Fluorescence Detection of NO2
Authors: Rodgers M.O. , Bradshaw J.D. , Davis D.D.
Published: February 2023

This paper presents the first results from a newly designed system for the purpose of detecting NO2 using the method of photofragmentation - laser induced fluorescence (PF-LIF). This method was proposed by Davis, et al. (1979) and by Rodgers, et al. (1979,80) for the detection of several fluorescing and non-fluorescing compounds. In this technique, the species to be detected is made to decompose into one or more vibrationally excited fluorescent species. One of these vibrationally excited photofragments is then optically pumped into an electronically excited state. A fraction of this resulting fluorescence, occurring at shorter wavelengths than the laser pump, is then sampled using appropriate long wavelength blocking filters. This allows for major discrimination against the white fluorescence background from aerosols, gas phase impurities, and the scatter chamber walls. In conventional laser induced fluorescence, this white fluorescence background can never be entirely eliminated as some of it must always fall within the bandpass of the detection system. In the PF-LIF approach, the white fluorescence noise can be reduced, at least in principle, to the level of the PMT dark count by the extensive application of long wavelength blocking filters.
Pressure Induced Broadening of 35C10 and 16O2 Millimeter-Wavelength Rotational Transitions By N2
Authors: Brinza D. E. , Pickett H. M. , Cohen E. A.
Published: February 2023

The importance of C10 as a catalytic species in stratospheric ozone depletion is of current interest. A product of the fast reaction of atomic chlorine and ozone, C10 distribution in the upper atmosphere has been modeled by Logan et al. [1]. Measurement of volume mixing ratios of stratospheric C10 is now performed by means of aircraft-based microwave emission spectrometers. The profiles obtained by analysis of the J=9/2-7/2, J = 13/2-11/2 and J = 15/2-13/2 transitions at 167 GHz, 241 GHz, and 278 GHz respectively are sensitive to the value of the pressure broadening parameter γ used in the collisional line shape function. Waters et al. [2] estimated γ = 3.8 MHz/mbar for C10 (μ = 1.24D) by linear interpolation of values for HF (γ = 4.5 MHz/mbar, μ = 1.8D) and CO (γ = 2.4 MHz/mbar, μ = 0.11D). This summary describes the determination of γ for C10 between 207K and 370K by N2 line broadening of the J=9/2-11/2 and J=13/2-15/2 transitions of v = 0 2Π3/2 35C10.
Comparison of Synthetic Nitric Acid Spectra with Laboratory and Atmospheric Measurements in the 11.3 Micron Region
Authors: Young C. , Evans W.F.J.
Published: February 2023

Theoretical absorption spectra for nitric acid in the 11.3 micron spectral region were generated by line by line integration. Only the v5 and 2v9 bands were considered. The rotational line positions and intensities were calculated using Dana's constants for the v5 band; for the 2v9 band the rotational constants were based on the results given by Chevillard and Giraudet2 in conjunction with an ab initio calculation using the vibrational constants of McGraw et al3. A Lorentzian line shape was used with a self broadened semi-­half width of 0.75 cm-1 at 300K and 1 atm. The semi-half width was assumed constant and at this stage of the work the varia­tion with rotational quantum number was ignored. Fig. 1 shows a comparison between a calculated spectra and an experimental spectrum of Goldman et al4. The differences between the calcu­lations and the experimental results could be due to the following; (a) neglect of a large number of the weaker lines, it was necessary to eliminate a number of weaker lines for computational purposes; (b) neglect of possible hot bands, as will be noted below there could be hot bands in the vicinity of 885 cm−1 and 910 cm−1; (c) the possibility that the wings of the lines are super Lorentzian.
Water Vapor Absorption Parameters For Selected Lines, 715-732nm And 932-961nm(1)
Authors: Schwemmer G.K. , Gentry B.M. , Wilkerson T.D. , Giver L.P.
Published: February 2023

Absolute absorption measurements were made on 172 selected lines in the near IR spectrum of H2O. Line strengths and N2 pressure broadening coefficients were determined with standard deviations in the range 1-5% for a majority of the lines. Self-broadening coefficients and pressure shifts were also measured for several lines. The line selection criteria were based on the requirements for remotely measuring atmospheric humidity profiles with narrow-band, tunable, pulsed lasers by means of light detection and ranging (lidar).
Ultra-Precision Grinding of Optical Materials to Produce Smooth Optical Components
Authors: Namba Yoshiharu
Published: February 2023

Optical glasses of brittle in nature have been machined into optical components by using grinding, lapping and polishing processes in industries. Recently, ductile regime grinding has been developped under the stimulus of the success of single point diamond turning in metal mirrors of soft metals.
Ductile Grinding Study of Glass Using an Ultra-Precision Surface Grinder and Different Grinding Wheels
Authors: Bennett Jean M. , Namba Yoshiharu
Published: February 2023

Fine grinding or ductile grinding is a way of putting a shiny surface on certain types of glass. As such, it is an alternative to conventional polishing, and offers the possibility of mass production of aspheric or other hard-to-produce shapes on lenses and mirrors. However, the parameters of ductile grinding are only imperfectly understood. A key factor is the stability of the machine used for the ductile grinding. Recently an ultra-precision surface grinder has been built1 that contains a low expansion Zerodur glass ceramic spindle to eliminate the changes in length (and hence depth of cut) that result from temperature changes during machining. Studies have been made with this machine to determine the optimum conditions for operating the diamond-impregnated grinding wheels to obtain the smoothest surface finish.2 These conditions are: a surface rotation speed of the wheel ~1200 meter/min, rotation speed of the workpiece ~0.01 meter/min, and depth of cut ~0.2 μm, making a repeating groove pattern of 3.6 μm, much like a diamond-turned surface.
Using Instrumented Indentation For Subsurface Damage Measurements
Authors: Polvani R. S. , Evans C.J.
Published: February 2023

Even unusual care in polishing, leads to optics with somewhat damaged faces. The question is to what degree? We will show instrumented indentation is a versatile, quick way to give an answer. Limited power, detail size, or durability are accepted hazards of subsurface damage. Its form varies: ductile materials damage by hardening, and brittle ones have fractured surfaces.
The Application of Scanning Microscopies to Optical Materials
Authors: Vorburger T.V. , Fu J. , Young R.D.
Published: February 2023

The paper has two parts: 1) an overview of various techniques of scanning microscopy and their relevance to optics; and 2) a discussion of an instrument under development for measuring the finish of optical surfaces with a range of 200 × 200 μm and a lateral resolution of ~ 1 nm.
Spectral Diffusion in Dye-Doped Deuterated Polymers
Authors: Sakoda Kazuaki , Maeda Masayuki
Published: February 2023

The spectral diffusion In dye-doped organic glasses has been one of the most attracting subjects in the field of persistent hole burning spectroscopy. However, the microscopic detail of the mechanism is usually unknown. In this study, we try to clarify it by means of the comparison between deuterated and protonated hydrogen bonding polymers.
Continuous Signal Processing Using Optical Coherent Transients
Authors: Babbitt W. R. , Bell J. A.
Published: February 2023

Modern communication, radar, and object recognition systems often rely on performing real- time convolutions of uninterrupted signal waveforms with fixed-pattern waveforms. Current systems are limited by low time-bandwidth product, low bandwidth, or programming difficulties. In this paper, we discuss a continuous signal processing technique employing optical coherent transient technology which largely overcomes these limitations.
On Some Problems of Time Domain Data Storage by Spectral Hole Burning
Authors: Kaarli Rein
Published: February 2023

Time-and-space-domain holography [1,2] by stimulated
photon echoes [3] provides a means of storing temporal
and spatial properties of an ultrafast-varying light signal and
recalling its authentic replica at any later moment. The possibility
of recording complex time shapes of light pulses, which also means
time-domain optical data storage, is based on the ability of
frequency-selective absorbers to store with high accuracy the temporal
Fourier components of the incident light [1-3]. The
time-domain frequency-selective optical storage of binary or analog
data is an alternative approach to the concept of frequency-selective
high-density data storage that provides a parallel ultrafast data
storage and processing in the frequency domain. The shortest detail of
the signal to be stored is limited by the reverse inhomogeneous
bandwidth of the storing media which reaches 10-100 fs for
frequency-selective materials while the duration of the signal is
limited by phase relaxation time T2 (usually
10-3-10-6s).
Material Considerations for Time-Domain Optical Storage
Authors: Kröll Stefan , Tidlund Per
Published: February 2023

Optical frequency-domain data storage using persistent spectral hole burning has been considered for more than ten years by now and the material parameter space required has been investigated and discussed [1,2]. An alternative approach to spectral storage, by utilizing the time-domain has been proposed by Mossberg [3]. This approach using coherent transient techniques (photon echoes) has gained increasing attention during the last years. However, to our knowledge an analysis of the required material parameter space for this approach still has not been published. In this conference paper some preliminary material considerations pertaining to time-domain storage and processing in inorganic crystals are presented.
Spectral Diffusion in Various Time and Temperature Domains
Authors: Haarer D. , Jahn S. , Kharlamov B.
Published: February 2023

It was recognized many years ago that temperature cycles increase the width of photochemical holes irreversibly /1/. There was no doubt, that this phenomenon was due to some non-equilibrated degrees of freedom of the considered amorphous organic matrix.
Hole-Burning Mechanisms and Crystal-Field Effects in Rare-Earth Doped Glasses
Authors: Schmidt Th. , van der Zaag P. J. , Schokker B. C. , Völker S.
Published: February 2023

Rare-earth ions doped in glasses or crystals have extremely narrow homogeneous optical linewidths at low temperature and are, therefore, excellent probes for studying small spectral splittings [1]. They are further potential candidates for data storage applications.
Two-Color Sensitization Mechanism of Photon-Gated Photochemical Hole Burninig in Photoreactive Polymers
Authors: Machida Shinjiro , Kyono Osamu , Horie Kazuyuki , Yamashita Takashi
Published: February 2023

Recently, a new type of photon-gated photochemical hole burning (PHB) system was provided1. The material consists of a zinc 9,18,27,36-tetra(4-tolyl)-tetrabenzoporphine (ZnTTBP) as the guest molecule, and a glycidylazide polymer (GAP) cross-linked with trimethylolpropane or ethylene glycol and isophorone diisocyanate as the photoreactive matrix polymer. The hole formation mechanism of this ZnTTBP/GAP system by two-color irradiation is concluded to be the sensitized decomposition reaction of excited azide groups via triplettriplet energy transfer.
Spectral Hole Burning in Chlorosomes of Green Photosynthetic Bacteria Chlorobium limicola
Authors: Pšenčík J. , Vácha M. , Adamec F. , Ambrož M. , Dian J. , Boček J. , Hála J.
Published: February 2023

Chlorobium limicola is a green sulfur photosynthetic bacteria. Its light harvesting system consists of huge extra-membrane ellipsoidal structures (100-150 nm long and 30-40 nm in diameter) called chlorosomes. Each chlorosome contains several thousands of bacteriochlorophyll-c (BChl-c) molecules (organized in long rod-like pigment-protein complexes) together with a significant amount of carotenoids. The whole chlorosome is enveloped with a BChl-a containing layer and attached to the cytoplasmic membrane through a water soluble BChl-a polypeptide link complex. Light energy absorbed in BChl-c is transfered via BChl-a in the envelope and via BChl-a in the link polypeptide complex to the BChl-a containing core antenna which surrounds the reaction center and is located within the cytoplasmic membrane. In the last few years, the dynamics of the excited energy transport (EET) in the whole light harvesting system of Chlorobium limicola and related species have been extensively studied. Fast EET from BChl-c to BChl-a was studied by means of ps absorption [1] and ps fluorescence decay [2]. Both methods yield similar values of the shortest decay components which characterize the EET: 21 ps and 26 ps, respectively. Detailed hole burning study of the BChl-a containing link antenna of Prosthecochloris aestuarii revealed excitonic structure of the antenna subunits and provided the decay times (on the order of 100 fs) of upper excitonic levels [3].
Light-induced broadening in hole-burning systems: Reversible and irreversible contributions
Authors: Richter W. , Barth K.
Published: February 2023

The profile of a persistent spectral hole can be used to very sensitively detect induced broadening processes that are caused by infrared radiation absorbed in the host matrix /1,2/. Both, the hole area and the hole width are affected to an extent which depends on the frequency of the irradiated IR-light. The excitation of specific vibrations in the host matrix leads to the observed broadening and filling phenomena of a hole spectrum which are highly selective with respect to different vibrational modes.
Spectral distribution of octaethylporphin photoproducts in polystyrene
Authors: Débarre A. , Le Gouët J.-L. , Lorgere I. , Tchenio P.
Published: February 2023

It is well-known that Persistent spectral Hole Burning (PHB) can occur in electronic transitions of porphines or related molecules embedded in amorphous matrices. Through PHB in those molecules, the temperature dependence of homogeneous line width in glasses and spectral diffusion have been extensively studied. Surprisingly, little attention has been paid to the spectral distribution of photoproducts which result from the PHB although it could enlighten the hole-burning mechanism in amorphous materials [1]. Here, we report on this problem for octaethylporphin/polystyrene as solute/host couple.
Proteins and Pressure: Compressibilities and Volume Fluctuations as measured by Spectral Hole Burning
Authors: Friedrich J. , Zollfrank J. , Gafert J. , Fidy J. , Vanderkooi J. , Parak F.
Published: February 2023

Spectral Holes are extremely sensitive to external pressure changes Ap [1], They shift and broaden already at pressure changes as low as 0.1 MPa. In this paper we focus on the frequency shift s of the holes. The frequency shift can be interpreted in a simple way on the basis of two system parameters. These are the isothermal compressibility n and the solvent shift v, of the burnt molecules: The conditions under which eq. 1 holds follow from the more general Laird-Skinner model [2].
Theory of Impurity Lineshapes in Crystals, Glasses, and Liquids
Authors: Skinner J. L.
Published: February 2023

Spectral lineshapes of impurities in condensed phases provide useful information about structure and dynamics. Understanding the origin of line broadening may facilitate the design of novel experimental techniques that could have useful technological applications. In this talk I will outline our recent theoretical work on inhomogeneous lineshapes of impurities in crystals and glasses, and on the crossover from inhomogeneous to homogeneous broadening in liquids.
Holeburning Holography in Eu3+:Y2SiO5 crystal
Authors: Sasaki H. , Karaki K. , Mitsunaga M. , Uesugi N.
Published: February 2023

Holeburning holography is an ultrahigh density image storage technique. Since the memory capacity is governed by the ratio of the inhomogeneous-to-homogeneous linewidths, 103~106 images can be recorded in a single sample spot. An extensive study on holebuming holography has been carried out by Wild et.al for organic dye-doped polymer samples1-4. On the other hand, holeburning holography has not been carried out for crystal samples, because there are few crystals exhibiting persistent holes. We have performed holeburning holography to record images for Eu3+:Y2SiO5 crystal which has been known for exhibiting persistent holes. Moreover, Eu3+:Y2SiO5 has other unique features5,6 such as narrow holewidth and high holeburning quantum efficiency. By using this crystal, we have also succeeded in real-time recording of a moving object.