| 1. |
- Andersson, Dan, 1966, et al.
(författare)
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Wave-breaking-free pulses in nonlinear-optical fibers
- 1993
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 10:7, s. 1185-1190
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Tidskriftsartikel (refereegranskat)abstract
- A qualitative as well as quantitative investigation is made of the conditions for avoiding wave breaking during pulse propagation in optical fibers. In particular, it is shown that pulses having a parabolic intensity variation are approximate wave-breaking-free solutions of the nonlinear Schrodinger equation in the high-intensity limit. A simple expression for the compression factor of a fiber-grating compressor based on parabolic pulses is also derived.
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| 2. |
- Karlsson, Magnus, 1967, et al.
(författare)
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Super-Gaussian approximation of the fundamental radial mode in nonlinear parabolic-index optical fibers
- 1992
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 9:9, s. 1558-1562
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Tidskriftsartikel (refereegranskat)abstract
- Using a direct variational technique involving super-Gaussian trial functions, we find approximate solutions for the fundamental radial mode of an optical wave propagating in a nonlinear parabolic-index fiber. A detailed examination is made of the amplitude, width, radial profile, and longitudinal phase shift of the stationary solutions that represent a two-dimensional balance among diffraction, nonlinear self-focusing, and linear wave guiding. For pulse powers below the self-focusing power, the stationary solutions are stabilized by the parabolic index variation.
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| 3. |
- Berg, R, et al.
(författare)
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Medical Transillumination Imaging Using Short-pulse Diode-lasers
- 1993
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 32:4, s. 574-579
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Tidskriftsartikel (refereegranskat)abstract
- The recently introduced time-resolved technique for enhanced medical transillumination imaging has been demonstrated for the important case of a diode laser transmitter. This type of gated-viewing technique utilizes early received light only to reject multiply scattered, delayed light, normally blurring the image. Human breast-cancer detection is demonstrated in vitro, and the observations are explained by using theoretical modeling and tissue phantom experiments.
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| 4. |
- Edner, H, et al.
(författare)
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Differential Optical-absorption Spectroscopy (doas) System For Urban Atmospheric-pollution Monitoring
- 1993
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 32:3, s. 327-333
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Tidskriftsartikel (refereegranskat)abstract
- We describe a fully computer-controlled differential optical absorption spectroscopy system for atmospheric air pollution monitoring. A receiving optical telescope can sequentially tune in to light beams from a number of distant high-pressure Xe lamp light sources to cover the area of a medium-sized city. A beam-finding servosystem and automatic gain control permit unattended long-time monitoring. Using an astronomical code, we can also search and track celestial sources. Selected wavelength regions are rapidly and repetitively swept by a monochromator to sensitively record the atmospheric absorption spectrum while avoiding the detrimental effects of atmospheric turbulence. By computer fitting to stored laboratory spectra, we can evaluate the path-averaged concentration of a number of important pollutants such as NO2, SO2, and O3. A measurement of NH3 and NO close to the UV limit is also demonstrated.
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| 5. |
- Edner, H, et al.
(författare)
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Fluorescence Lidar Multicolor Imaging of Vegetation
- 1994
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 33:13, s. 2471-2479
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Tidskriftsartikel (refereegranskat)abstract
- Multicolor imaging of vegetation fluorescence following laser excitation is reported for distances of 50 m. A mobile laser-radar system equipped with a Nd:YAG laser transmitter and a 40-cm-diameter telescope was utilized. The laser light was Raman shifted to 397 nm with pulse energies of approximately 30 mJ. An image-intensified CCD camera with a specially designed split-mirror Cassegrainian telescope was utilized for the simultaneous recording of fluorescence images of leaves and branches in four different spectral bands. Additionally, fluorescence spectra at selected points within the detection area were measured with an image-intensified diode array system. Image processing permits extraction of information related to the physiological status of the vegetation and might prove useful in forest decline research.
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| 6. |
- Faldon, M. E, et al.
(författare)
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Studies of time-resolved harmonic generation in intense laser fields in xenon
- 1992
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 9:11, s. 2094-2099
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Tidskriftsartikel (refereegranskat)abstract
- We report preliminary experimental and computational studies of the temporal evolution of the harmonics, generated in xenon, by 50-ps pulses from a Nd: YLF laser, amplified in Nd: glass amplifiers, and focused to produce intensities in the range 1013--5 {\texttimes} 1013 W cm{\textminus}2. Measurements were made of the temporal profiles of the seventh- and ninth-order harmonics using a specially modified VUV streak camera with better than 7-ps temporal resolution. These results were compared with predictions of a numerical model that included the effects of neutral atom depletion and photoelectron dispersion in the calculation of the harmonic output as a function of time.
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| 7. |
- Kröll, Stefan, et al.
(författare)
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Recording Density Limit of Photon-echo Optical Storage With High-speed Writing and Reading
- 1993
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 32:35, s. 7233-7242
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Tidskriftsartikel (refereegranskat)abstract
- The first analysis to our knowledge of the optical data storage density of photon-echo storage is presented. Mainly considering signal-to-noise ratio performance, we calculate the obtainable storage density for data storage and processing using photon echoes to be approximately 100 times the theoretical limit for conventional optical data storage. This limit is similar to that theoretically calculated for data storage by use of persistent spectral hole burning. For storage times longer than the upper-state lifetime the highest densities can, however, be obtained only if all the excited atoms decay, or are transferred, to a different state than that from which they were originally excited. The analysis is restricted to samples with low optical density, and it also assumes that for every data sequence, writing is performed only once. It is therefore not directly applicable to accumulated photon echoes. A significant feature of photon-echo storage and processing is its speed; e.g., addressing 1 kbyte/(spatial point) permits terahertz read and write speeds for transitions with transition probabilities as low as 1000 s-1.
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| 8. |
- Lundin, Richard
(författare)
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Dispersion flattening in a W fiber
- 1994
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 33:6, s. 14-1011
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Tidskriftsartikel (refereegranskat)abstract
- An exhaustive and simple method for dispersion flattening in double-clad single-mode fibers is presented. The idea is to generate all such fibers with a certain cutoff wavelength and then find, by one-dimensional minimization and direct inspection, fibers yielding minimum dispersion. As examples, the root mean square chromatic dispersion over the wavelength range (1.25, 1.60 mum) is minimized for a W fiber and also for a triangular-index fiber with a depressed inner cladding. The material dispersion is included through a Sellmeier refractive-index formula. The full vector solution of Maxwell's equations is used. It is found, as is well known, that the W fiber is capable of dispersion flattening. The validity of the numerical results presented depends on the validity of the approximate refractive-index model used.
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| 9. |
- Lundin, Richard
(författare)
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Minimization of the chromatic dispersion over a broad wavelength range in a single-mode optical fiber
- 1993
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 32:18, s. 45-3241
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Tidskriftsartikel (refereegranskat)abstract
- The effective refractive index as a function of vacuum wavelength is approximated by Lagrange interpolation polynomials. The rms value of the chromatic dispersion is then calculated analytically. It is demonstrated that use of fourth-degree polynomials is far more efficient than the use of second-degree polynomials. The rms value of the chromatic dispersion over the wavelength range (1.25 mum, 1.60 mum) is calculated and minimized for step-index fibers, triangular index fibers, and alpha-power fibers. The full vector solution of Maxwell's equations is used. The error induced by the approximate refractive-index model is found to be negligible at the point of minimum dispersion.
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