Optical Radiation Sources Research Articles

Cylindrical Talbot cavity

A cylindrical Talbot cavity is proposed for phase-locked operation of a circular laser array. This array could act as a 'bulk' source of coherent optical radiation emitted by an angular aperture of up to 2π in width.

Eclipse mapping of the accreting magnetic white dwarf in DP Leonis with HST

We present time-resolved ultraviolet spectrophotometry of the AM Her system DP Leo (E1114+182), obtained with the Faint Object Spectrograph on the Hubble Space Telescope (HST) in 1991 October. During this period, the binary was in a low-activity state. Complementary optical spectrophotometry and spectopolarimetry were obtained in 1991 October and December, as well as in 1992 April when the object had entered a high-accretion state. The HST spectrophotometry reveals two UV-emitting components-a hot 'spot' (T approximately 50,000 K, very approximately) near the magnetic pole into which most material is accreted, and the white dwarf photosphere (T approximately 16,000 K), which dominates when the spot is not in view. Both components appear as rapid and gradual components in the ingress and egress of secondary eclipse, the latter indicating a normal white dwarf radius of 0.8 x 10(exp 9) cm. The fractional area of the spot (f approximately 0.006) implied by the eclipse data is consistent with the observed UV flux and a minimum distance of 380 pc is similar to those found in other AM Her systems. The nearly identical eclipse light curves from the HST and earlier optical observations imply that the UV-emitting reprocessing area is not more extended than the cyclotron source of optical radiation in the accretion funnel. The timing of the onset of the bright phase indicated that the spot leads the secondary in orbital azimuth by approximately 3 deg.

Highly stable, monochromatic and tunable optical radiation source and its application to high accuracy spectrophotometry

An optical radiation source has been developed by coupling a dye laser to a small integrating sphere with an optical fiber. The radiant power from this source, which is monochromatic and spectrally tunable, has been stabilized to +/-0.02%. Nonuniformities in the emitted optical radiation field caused by speckle have been overcome by vibrating the fiber at ultrasonic frequencies. The source has been successfully used in a spectrophotometer to measure the transmittance of a large lens with an uncertainty of +/-0.01%, and the spectral responsivity of a filter radiometer with an uncertainty of +/-0.04%.

Collinear interaction of the optical waveguide modes and surface magnetostatic waves in a Lu2.14Bi0.86Fe4.94Mg0.06O12 film

This paper reports the maximum diffraction efficiency per unit microwave power achieved so far in experiments on the interaction of optical waveguide modes with magnetostatic waves (MSW) in ferrimagnetic films. To obtain high efficiency of the interaction a film of Lu2 .14Bi0.86Fe4.94Mg0.06O12 grown on a gadolinium gallium garnet substrate, and collinear propagation of the surface MSW and guided light were used. Measurements of the spectrum of optical modes in the film have shown extremely high values of the birefringence between a TE and a TM mode, induced by the mismatch of the lattice parameters of the film and the substrate (Δnbi = 4.5 × 10−3). A He-Ne laser (λ=1.152 μm) was used as the source of optical radiation. The measurements of the efficiency of the interaction were carried out for two geometries: (i) parallel propagation of the light and MSW, and (ii) antiparallel propagation of the light and MSW. As predicted by theory, the efficiency of the parallel interaction was higher than that of the antiparallel interaction. The efficiency for the case of the parallel interaction was of the order of 0.8% per 1 mW of the MSW microwave power.

The measurement and hazard assessment of sources of incoherent optical radiation

Measurement requirements for the purpose of hazard assessment of optical radiation from non-laser sources are presented. Established criteria to limit overexposure to optical radiation in occupational environments are summarised as a function of the spectral ranges defining important photobiological effects. An example of the method of hazard assessment across the relevant spectral ranges is presented.

A method and instrument for spectral distribution measurement of the optical radiation and erythemal UV-irradiance and dose by photometer with a spherical receiver

A method and an optical device have been developed for the spectral distribution measurement of optical radiation (OR), the measurement of the erythemal UV-irradiance and dose, and of the spherical erythemal irradiance and dose using only one instrument with a spherical photodetector. In this case the spectral sensitivity of the instrument is unchanged for the two measurements. The device for the measurement of the spectral distribution of OR is produced as a disc with six built-in interference filters with their maxima of transmission in the range of 280–400 nm. Data processing and histogram restoration of the OR spectral distribution is done according to a method developed and based on the solution of a seven-degree polynom. The device for measurement of irradiance and the dose on-plane is made of opaque material and is in the form of an overturned cylindrical cup with a circular opening in the bottom. The photometer-dosimeter has a spectral sensitivity near to the spectrum of erythem action of OR. A special vacuum photoelement is used with a spherical photocathode and an optical correcting filter system (OCFS) shaped as an irregular dodecahedron. The measurement of the erythemal irradiance and dose from natural and artificial sources of OR is in the range 280–400 nm, in efficiency units (mer/m 2), with an error of no more than ±10%.

Experience with laser safety in the USA-a review

Following several research programs in the 1960's aimed at studying the adverse biological effects of lasers and other optical radiation sources, laser occupational exposure limits were set and general safety standards were developed. Today, the experience from laser accidents and the development of new lasers and new applications have altered the format of the exposure limits and the safety procedures. It is critically important to distinguish between different biological injury mechanisms. The biological effects of ultraviolet radiation upon the skin and eye are additive over a period of at least one workday, and require different safety procedures. The scattered UV irradiance from excimer lasers may be quite hazardous, depending upon wavelength and action spectra. Since laser technology is young, the exposure of an individual in natural sunlight must be studied to evaluate the potential for chronic effects. The safety measures necessary in the use of lasers depend upon a hazard evaluation. The appropriate control measures and alternate means of enclosure, baffling, and operational control measures are presented. Present laser safety standards are explained briefly. Eye protective techniques and eyewear are considered for a variety of sources. The optical properties of enclosure materials are also discussed.

Diode Laser—Pumped Solid-State Lasers

Diode laser-pumped solid-state lasers are efficient, compact, all solid-state sources of coherent optical radiation. Major advances in solid-state laser technology have historically been preceded by advances in pumping technology. The helical flash lamps used to pump early ruby lasers were superseded by the linear flash lamp and arc lamp now used to pump neodymium-doped yttrium-aluminum-garnet lasers. The latest advance in pumping technology is the diode laser. Diode laser-pumped neodymium lasers have operated at greater than 10 percent electrical to optical efficiency in a single spatial mode and with linewidths of less than 10 kilohertz. The high spectral power brightness of these lasers has allowed frequency extension by harmonic generation in nonlinear crystals, which has led to green and blue sources of coherent radiation. Diode laser pumping has also been used with ions other than neodymium to produce wavelengths from 946 to 2010 nanometers. In addition, Q-switched operation with kilowatt peak powers and mode-locked operation with 10-picosecond pulse widths have been demonstrated. Progress in diode lasers and diode laser arrays promises all solid-state lasers in which the flash lamp is replaced by diode lasers for average power levels in excess of tens of watts and at a price that is competitive with flash lamp-pumped laser systems. Power levels exceeding 1 kilowatt appear possible within the next 5 years. Potential applications of diode laser-pumped solid-state lasers include coherent radar, global sensing from satellites, medical uses, micromachining, and miniature visible sources for digital optical storage.

医療分野に使用されている光源

医療分野に使用されている光源

Detached nuclear-like activity in the radio galaxy PKS 2152–69

The effects of nuclear activity in galaxies are known to extend well beyond the immediate nuclear environment. This is particularly true in some quasars and the active ellipticals or radio galaxies where the influence of the central engine can be apparent on scales of up to several megaparsecs. In addition to the large-scale regions of non-thermal radio emission there are sometimes sources of optical, both line and continuum, emission which appear to be associated in some way with the transport of energy from the nucleus to the larger structures. This letter reports the discovery of a bright cloud of gas at a projected distance of 8 kpc (H0 = 50 km s-1 Mpc-1 used throughout) and approximately along the radio axis of the radio galaxy PKS 2152–69. It is shown to radiate a nebular spectrum including lines from the highly ionized species He+, Ca4+, Fe6+ and Fe9+. A compact source of optical continuum radiation within the cloud has an energy distribution which is considerably bluer than the residual light from the underlying galaxy.

The characterization of a black light device: a hazard evaluation process.

The results of an occupational hazard evaluation process to assess the potential ultraviolet radiation exposure from broad-band sources of optical radiation are compared with the American Conference of Governmental Industrial Hygienists (ACGIH) guidelines for occupational exposure to ultraviolet radiation. A black light fluorescent lamp device, evaluated according to these criteria, exceeded the ACGIH-TLV for UVA and UVB. Design modifications resulted in acceptable occupational exposure levels without compromising the performance of the device.

The Characterization of a Black Light Device: A Hazard Evaluation Process

The results of an occupational hazard evaluation process to assess the potential ultraviolet radiation exposure from broad-band sources of optical radiation are compared with the American Conference of Governmental Industrial Hygienists (ACGIH) guidelines for occupational exposure to ultraviolet radiation. A black light fluorescent lamp device, evaluated according to these criteria, exceeded the ACGIH-TLV® for UVA and UVB. Design modifications resulted in acceptable occupational exposure levels without compromising the performance of the device.

Optical Radiation Sources for Medical and Health-care Uses

Optical Radiation Sources for Medical and Health-care Uses

Fiber-optic ring interferometer with a multimode waveguide

The nature of propagation of electromagnetic oscillations in a multimode waveguide is considered and it is shown in principle that such a waveguide can be used in a fiber-optic ring interferometer in combination with an optical radiation source characterized by a short coherence length. A description is given of the apparatus and the results of an experimental investigation of such an interferometer are reported. Ways of improving further the sensitivity of this interferometer are discussed.

Spectral tuning and linewidth narrowing of shallow-junction surface emitting GaAs LED́s through γ-ray irradiation

Alterations of device characteristics as a result of γ-ray irradiation of shallow-junction surface emitting devices are different from those of deep-junction devices with respect to LED emission intensity reduction, I-V curve, line shape, and spectral shift. In particular, much larger spectral shifts in the opposite direction-toward longer wavelengths-are reported here than those found in the literature for deep-junction devices. A qualitative model based upon photochemical doping and changes in surface band bending is proposed to explain these phenomena. Changes in surface emitting shallow-junction optical radiation source device characteristics brought about by γ-ray irradiation are desirable ones for utilization in most optical fiber communication systems. These changes include linewidth narrowing, decreased time response, and decreased material dispersion because of the emission wavelength change.

Optical Radiation Measurements and Instrumentation

Accurate measurement of optical radiation is required when sources of optical radiation are used in biological research. Such measurement of broad-band noncoherent optical radiations usually must be performed by a highly trained specialist using sophisticated, complex, and expensive instruments. Presentation of the results of such measurement requires correct use of quantities and units with which many biological researchers are unfamiliar. The measurement process, quantities, units, measurement systems and instruments, and uncertainties associated with optical radiation measurements are reviewed in this paper. A conventional technique for evaluating the potential hazards associated with broad-band sources of optical radiation and a spectroradiometer developed to measure spectral quantities is described. A new prototype ultraviolet radiation hazard monitor which has recently been developed is also presented. This new instrument utilizes a spectrograph and a spectral weighting mechanical mask and provides a direct reading of the effective irradiance for wavelengths less than 315 nm.

Useful book on later physics (L. V. Tarasov,Physics of Processes in Coherent Optical Radiation Sources, Radio i Svyaz', Moscow, 1981,440 pp.)

Useful book on later physics (L. V. Tarasov,<i>Physics of Processes in Coherent Optical Radiation Sources</i>, Radio i Svyaz', Moscow, 1981,440 pp.)

An Electrooptics and Microwave Optics Program in Electrical Engineering

The Moore School of Electrical Engineering offers a program in electrooptics, with a microwave optics component, intended for graduate and advanced senior undergraduate electrical engineering students. The courses offered cover topics in classical and modern optics, such as matrix treatment of optical systems; physical, Fourier, and electron optics; coherence, radiometry, and photometry; sources of optical radiation; and modulation and detection. In addition, optical computing, optical and nonoptical holography, and synthetic aperture systems are included. Course material is introduced by taking advantage of the strong background our electrical engineering students have in electromagnetics, Fourier analysis, linear systems, matrix methods, and communications and information theory. Outlines and source material for the various courses in the program are presented here, together with a description of laboratory facilities that allow students to become familiar with the practical aspects of electrooptics and microwave optics in a research-oriented environment rather than a structured laboratory course environment. Supervised involvement of the student in the ongoing research activity serves as a vehicle for learning experimental techniques.

Optical clues to the nature of Hercules X-1/HZ Herculis

The 1d/sub ./7 optical light curve of Her X-1/HZ Her varies in a highly systematic fashion over the 35 day X-ray on-off cycle. These variations can be reproduced in some detail by a relatively simple model based on a tilted, precessing accretion disk which serves three functions: a source of optical radiation, a shadowing body for X-ray emission, and an occulting body for the reemitted optical radiation from the heated face of HZ Her. A minimum variance relaxation of this model onto the available photometric data suggests that the disk is well represented by a precessing, steady-state configuration of accreting matter, that the disk essentially fills the critical Roche lobe of the collapsed companion, and that the disk is tilted out of the orbital plane by an angle which exceeds the complement of the orbital inclination. (AIP)

Reading of holograms with an optoelectronic memory element made of a homogeneous material

A theoretical and experimental study was made of the time and optical characteristics of the reading of holograms with an integrated optoelectronic memory element. A semiconductor laser operating at room temperature was used as an optical radiation source.