Showing papers by "Amnon Yariv published in 1970"

Observation of propagation cutoff and its control in thin optical waveguides

Abstract: The first observation of optical cutoff in thin‐film waveguides is reported. The waveguides consist of thin (∼10μ) epitaxial layers of high‐resistivity GaAs deposited on lower‐resistivity GaAs substrates. The optical cutoff is controlled through the electro‐optic effect by applying an electric field across the epitaxial layer.

Final review report.

Abstract: : Research under the Contract generally covered the following areas: Plasma wave resonances in spatially non-uniform plasmas; Cyclotron and upper hybrid echo phenomena in plasmas; Plasma wave echoes; Cyclotron harmonic waves in plasmas; Resonance cones in anisotropic plasmas; Recombination radiation from forward biased p-n junctions; Electro-optic effect; Infrared absorption in gallium arsenide; and Modes in optical resonators with gain. The report contains a summary of research. (Author)

Electrical and optical characteristics of InAs junction lasers

Abstract: Electrical and light emission characteristics of pulsed InAs p-n junction lasers, prepared by diffusing Zn into Sn-doped n-type crystals with a substrate concentration of 1018cm-3, were studied at 4.2, 20.4, and 77°K. Data of variation of capacitance with bias showed these to be abrupt junctions. At injection currents below threshold, the temperature independence of the slopes of the I-V characteristics and the observed variation of the integrated light intensity with current suggest the injection mechanism be photon-assisted tunneling. The peak of the spontaneous radiation shifts with the applied voltage in the expected manner. The time-resolved laser spectra are seen to shift to longer wavelengths during pulsed operation of the laser. The line shift results from joule heating of the junction, and follows the variation of bandgap with temperature. From a plot of threshold current density as a function of reciprocal length gain and loss factors have been calculated. An independent value of the gain factor was obtained from the observed variation with current of the superradiantly narrowed linewidth from a nonlasing structure. Mode-confinement studies indicate that the mode confinement is due to the optical gain in the junction region.

A Theoretical Study of Optical Wave Propagation Through Random Atmospheric Turbulence

Abstract: A new method for obtaining exact analytical expressions for some statistical functions of an optical wave propagating through a randomly turbulent medium is reported. A power-series solution of the wave equation (∇2 + k2n2(x))u(x) = 0 is derived for a homogeneous random-refractive-index field n(x). Exact analytical expressions are obtained for the average wave function 〈u(x)〉 and the two-point correlation function 〈u(L, r1)u*(L, r2)〉, with the added assumption that n(x) is a Gaussian random process always close to unity. The intensity correlation function 〈I(L, r1)I(L,r2)〉 is investigated, and recent experimental results regarding the behavior of the intensity fluctuations are discussed.

Research in Nonlinear Optics.

Abstract: : The report is on elucidating the properties of ultrashort pulses emitted by mode-locked neodymium and ruby lasers. The point of departure is to measure properties of individual ultrashort pulses rather than as an average of many pulses. An experimental approach to obtain the pulse width and energy is outlined including approximate results. More accurate measurements is awaiting more accurate computer solutions of associated partial differential equations. As a side, these experiments lend themselves to complementary studies of the chemical dynamics of Q-switch dyes such as the decay times on a time scale comparable to ultrashort pulse durations. (Author)