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DOE OSTI2025

Second harmonic generation in topological insulators under quantizing magnetic fields

We theoretically investigate the second harmonic generation (SHG) of topological insulator surface states in a perpendicular magnetic field. Our theory is based on the microscopic expression of the second-order magneto-optical conductivity developed from the density matrix formalism, taking into account hexagonal warping effects on the surface states' band structure. Using numerically exact Landau-level energies and wave functions including hexagonal warping, we calculate the spectrum of SHG conductivities under normal incidence for different values of magnetic field and chemical potential. The imaginary parts of the SHG conductivities show prominent resonant peaks corresponding to one-photon and two-photon inter-Landau-level transitions. Treating the hexagonal warping term perturbatively, these transitions are clarified analytically within a perturbation theory from which approximate selection rules for the allowable optical transitions for SHG are determined. Furthermore, our results show extremely high SHG susceptibility that is easily tunable by magnetic field and doping level for topological surface states in the far-infrared regime, exceeding that of many conventional nonlinear materials. This work highlights the key role of hexagonal warping effects in generating second-order optical responses and provides insights into the nonlinear magneto-optical properties of the topological insulators.

Landau levels↗

DOE OSTI2024

Unique optical excitations in topological insulators (Final Technical Report)

The overall objective of this research is to understand how light interacts with topological insulator (TI) films and layered structures. Unlike normal materials, the electrons in TI films are trapped at the top and bottom surfaces of the film. These electrons have unusual properties, including low mass and high velocity. Light shining on these trapped electrons will excite electron density waves, called plasmons, which inherit the unusual properties of the electrons. This project aims to understand how these plasmons interact with each other and how the plasmon properties change as the film dimensions change. By controlling the physical properties of the films, the optical response of the film can also be controlled. In addition to single TI films, the project will also investigate the properties of stacks of TI films layered with normal insulating films. Stacking these materials results in multiple layers of trapped electrons whose plasmons can interact in ever more complex ways. After these interactions are understood, we can begin to engineer complex TI structures to obtain designer optical phenomena in the far-infrared and THz, wavelength ranges of interest for environmental monitoring and chemical sensing. This research directly addresses DOE Grand Challenges, including understanding how properties of matter emerge from complex electronic correlations and learning how to control these properties as well as the mission of the Basic Energy Sciences program to understand and control matter at the electronic/atomic level.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Southern Hemisphere Polar Infrared Radiation Experiment (SHIRE) Field Campaign Report

An extended-range atmospheric emitted radiance interferometer (AERI) instrument to be deployed to Scott Base (78 S, 166 E) in McMurdo Sound, Antarctica for the purpose of synergizing with the National Aeronautics and Space Administration (NASA) Polar Radiant Energy in the Far-InfraRed Experiment (PREFIRE) satellite mission (https://prefire.ssec.wisc.edu/), examining the closure of atmospheric thermal emission, and providing validation for PREFIRE. The PREFIRE mission is the first satellite mission to map Earth’s spectrally resolved thermal emission, from 5 to 50 microns, over seasonal to annual timescales. These new observations represent the beginning of an intensive examination of the nature of thermal emission from Earth (emission from both the surface and atmosphere). A primary requirement of the PREFIRE mission is to provide validation of the retrieved variables. Numerous field sites in the Arctic (such as the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) North Slope of Alaska observatory and Summit Station, Greenland) have existing instrumentation to facilitate validation, leaving an observational gap in Antarctica. Through SHIRE, we propose to establish a temporary, intensive measurement site in Antarctica to ensure that both poles are suitably represented, and benefit from this state-of-the art science. This will also allow Arctic and Antarctic atmospheric radiative states to be compared and contrasted. For SHIRE specifically, we also propose further objectives to examine the spectrally resolved thermal radiative closure of the polar atmosphere and the historical changes in Antarctic radiative forcing, using previous Antarctic field campaigns, such as the ARM West Antarctic Radiation Experiment (AWARE).

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1972

Spectroscopy of dimers.

The method of Stogryn and Hirschfelder, which divides two-particle phase space into bound, metastable, and free particle parts, is applied to the statistical averages which determine the first three spectroscopic moments of 'collision-induced' far-infrared and Raman spectra. Numerical results are presented for a number of models of noble gas systems. It is shown that for some systems, but not all, dimers make important, although not necessarily well-separated, contributions to the spectrum.

Levine, H. B.↗

NASA NTRS1973

The 100-micron observations of galactic and extragalactic Southern Hemisphere objects

Far-infrared observations of the interstellar medium are reported by a balloon-borne telescope. With the 30-centimeter (12-in.) telescope operating at a wavelength of 100 microns, approximately forty new sources were observed in the galactic plane and in the large Magellanic Cloud. Patterns and some degree of understanding are beginning to emerge from the observations of objects in the far infrared.

Hoffmann, W. F.↗

NASA NTRS1972

A simple analytic approximation for dusty stromgren spheres.

We interpret recent far-infrared observations of H II regions in terms of true absorption by internal dust of a significant fraction of the Lyman-continuum photons. We present approximate analytic expressions describing the effects of internal dust on the ionization structure of H II regions, and outline a procedure for deducing the properties of this dust from optical and infrared observations.

Petrosian, V.↗

NASA NTRS1972

Balloon observations of galactic and extragalactic objects at 100 microns.

Recent far-infrared balloon-borne instruments have yielded observations of a number of bright sources at 100 microns. Many of these coincide with HII regions where molecular line emision has been detected. There is some indication of 100 micron emission which does not coincide with radio measurements.

Hoffmann, W. F.↗

NASA NTRS1972

Review of results in infrared space astronomy.

Some stars, in particular, T Tauri stars, have substantial IR excesses at 10 microns. It is now understood that the long wavelength radiation comes from a shell of dust which surrounds the star and absorbs the stellar radiation. Part of the mass which is lost from supergiants is condensed into solid particles which remain in the stellar environment and provide the excess IR radiation. The most intense far-infrared object outside the solar system is the galactic center. Diffuse galactic IR objects include extended regions of gas and dust surrounding very hot young stars and regions of gas and dust surrounding cooler stars. Other subjects considered include IR galaxies and cosmic radiation.

Hoffmann, W. F.↗

NASA NTRS1973

Further measurements of the submillimeter background at balloon altitude.

Results of measurements of the far-infrared background radiation made with a balloon-borne radiometer at an altitude of 44 km. Equivalent blackbody temperatures were obtained for the background radiation in three bandwidths: 1 to 11.5 per cm, 1 to 13.5 per cm, and 1 to 18.5 per cm. The total measured flux in the largest of these bandwidths is dominated by the atmospheric emission by ozone and water. The data obtained confirm the results of prior flights, in particular, that a substantial amount, and perhaps all, of the radiation above 13 per cm is due to the atmosphere.

Muehlner, D. J.↗

NASA NTRS1972

The Lunar and Planetary Laboratory and its telescopes.

The campus and observatory facilities of the Lunar and Planetary Laboratory at the University of Arizona are described, with particular reference to the Space Sciences Building and its Optical Shop. The Catalina Observatory (located on a peak of the Catalina Mountains, 36 miles from the University) and its facilities intended for planetary photography, near-infrared spectroscopy and interferometry, far-infrared broadband photometry and image scanning, and studies of asteroids, comets, and other stellar studies are discussed. The layout, facilities, and telescopes of the Mount Lemmon Observatory intended for infrared astronomical research are also covered.

Kuiper, G. P.↗

NASA NTRS1974

Dust grains in a hot gas. I - Basic physics. II - Astrophysical applications

The interaction of graphite grains with a hot gas is investigated. Detailed computations, based on experimental data and simple theoretical models are presented of the energy transfer by gas particle collisions and of the sputtering rates and grain lifetimes, as functions of gas temperature and grain radius. The electric charge on the grains is calculated, and the effect of electric forces on mechanical stability is discussed. The rate at which the gas cools by this mechanism is evaluated. The results of the work on gas-grain cooling and sputtering rates are applied to various astrophysical environments where dust and hot gas may coexist. The effect is studied of swept-up interstellar grains on the evolution of young supernova remnants, and the infrared luminosity is computed as a function of the age of the remnant. An interpretation is proposed of far-infrared sources embedded in compact H II regions or dense clouds, in terms of the supernova phenomenon, with specific application to eta Carinae. The question of the existence of dust in intergalactic matter in galaxy clusters is also reexamined.

Burke, J. R.↗

NASA NTRS1974

Instrumentation optimization in Fourier spectroscopy. I - Far infrared beam splitters

Computations of the reflectivity, transmissivity, and efficiency properties for TE, TM, and T45 deg waves of far-infrared beam splitters and of the polarizations induced at both reflection and transmission are described. Effects of variations in the state of polarization, orientation, pointing accuracy, and wavelength of the incident light, as well as variations in refractive index and thickness of the beam splitters, are discussed. These results apply directly to Fourier interferometer-spectrometers. They can be used for optimizing the performance of these instruments. They indicate, in particular, that some advantages may be gained by the use of incident polarized light (angle of polarization smaller than about 45 deg or negative elliptical polarization) or light of large incidence angle (larger than approximately 60 deg) or both.

Deuze, J. L.↗

NASA NTRS1974

Balloon-borne infrared coronagraph

The use of balloon vehicles to observe the solar corona with an infrared coronagraph is reviewed. The scientific results and the instruments employed are discussed. A parallel is drawn between the required functions of a coronagraph and of a far-infrared cold telescope.

Strong, J.↗

NASA NTRS1974

Low-background air-infrared telescope for balloon-borne infrared astronomy

The design and performance of a far-infrared telescope are discussed. The instrument is twenty centimeters in diameter and has excellent operating characteristics at 100 microns. The principal features of the telescope are summarized. A diagram of the system is provided. The telescope completed two sucessful balloon flights in which the planets Mars and Saturn were used as calibration sources. Observations were made of the H2 regions W 3, Orion A, NGC 2024, and the bright infrared galaxy M 82.

Low, F. J.↗

NASA NTRS1974

Stabilization, pointing and command control of a balloon-borne 1-meter telescope

A 1-meter balloon-borne telescope has been constructed and flown to observe far-infrared radiation from celestial sources. The attitude control systems must perform to the diffraction limit of the telescope for stabilization and have positioning capability for source acquisition. These and associated systems are discussed in detail, as is the command control of the payload as a whole.

Hazen, N. L.↗

NASA NTRS1975

Design and analysis of optically pumped submillimeter waveguide maser amplifiers and oscillators

The design and experimental measurements are described of an optically pumped far-infrared (FIR) waveguide maser; preliminary measurements on a FIR waveguide amplifier are presented. The FIR maser was found to operate satisfactorily in a chopped CW mode using either methanol (CH3OH) or acetonitrile (CH3CN) as the active molecule. Two other gases, difluoroethane and difluoroethylene, produced an unstable output with high threshold and low output power when operated in the chopped CW mode. Experimental measurements include FIR output versus cavity length, output beam pattern, output power versus pressure, and input power. The FIR output was the input to an amplifier which was constructed similar to the oscillator. An increase of 10% in output power was noted on the 118.8 microns line of methanol.

Galantowicz, T. A.↗

NASA NTRS1974

Synchronous Earth Observatory Satellite /SEOS/

NASA/GSFC is currently studying the applications and technical requirements for a Synchronous Earth Observations Satellite (SEOS). Such a satellite would combine the relatively high resolution and multi-spectral capability of the Earth Resources Technology Satellite (ERTS) with the on-station continuous monitoring of the Synchronous Meteorological Satellite (SMS). SEOS capability is geared to perform disaster warning of tornadoes and floods as well as to monitor transient phenomena affecting earth resources (e.g., green waves and algae blooms). The heart of the system is a Large Earth Survey Telescope (LEST) which has a designed 1.5 meter diameter. Spectral bands in the visible, near- and far-infrared have been selected to optimize SEOS utility. A microwave sounder will be used in conjunction with the LEST for meteorological applications.

Walter, L. S.↗

NASA NTRS1975

Jupiter - Interpretation of the Pioneer 10 infrared radiometer and S-band occultation observations

On the basis of recently calculated models of the Jovian atmosphere, a value of 5.0 was derived for the H2/He mixing ratio from the Pioneer 10 infrared radiometer data. A far-infrared spectrum corresponding to the thermal profile obtained in the Pioneer S-band occultation experiment was also computed. The spectrum strongly suggests a misinterpretation of the data obtained in that experiment.

Hogan, J. S.↗