Annealing dependent far field of GaAs-(Ga,Al)As LEDs

The far field intensity distribution of spontaneously light-emitting diodes with FABRY-PEROT structure and its dependence on different annealing processes during the diode preparation is studied. The electromagnetic field distribution in the far field is considered for a four-layer-stepdiscontinuity of the dielectric constant in a GaAs-(Ga,Al)As heterostructure diode. Even for a symmetrical dielectric constant profile the maximum luminescence intensity is not emitted necessarily in a plane normal to the light emitting surface of the diode. This cross-eyedness can be influenced by annealing. The changed far-field pattern can be evaluated if one knows the doping profile in the vicinity of the p-n junction and its changes during the annealing. Theoretical statements are in qualitative agreement with experimental results.The authors are grateful to Dr. K.Unger for valuable discussions and to Miss B.Russ for assistance with the measurements. The radioanalytical Zn determination by Mrs. G.Hänold from the VEB Halbleiterkombinat Frankfurt/Oder, Werk Stahnsdorf is gratefully acknowledged. This paper incorporates work carried out in the Arbeitsgemeinschaft AIII-BV-Halbleiter.     

Neighborly combinatorial 3-manifolds with 9 vertices

A complete classification is given for neighborly combinatorial 3-manifolds with 9 vertices. It is found that there are 51 types, only one of which is not a sphere.     

E2 nuclear resonance effects in pionic and kaonic atoms

The attenuation due to the E2 nuclear resonance effect has been measured in hadronic atoms using pions with ¹¹¹Cd and ¹¹²Cd, and for kaons with ¹²²Sn. Energies of the relevant X-ray and γ-ray transitions and of the X-ray cascade intensities have also been measured so as to give a self-consistent set of information. The results are found to be in very good agreement with theoretical calculations.     

Ionization equilibrium and radiative energy loss rates for C,N, and O ions in low-density plasmas

The results of calculations of the ionization equilibrium and radiative energy loss rates for C, N and O ions in low-density plasmas are presented for electron temperatures in the range 10⁴–10⁷ °K (～1–10³ eV). The ionization structure is determined using the steady-state corona model, in which electron impact ionization from the ground states is balanced by direct radiative and dielectronic recombination. Using an improved theory, detailed calculations are carried out for the dielectronic recombination rates in which account is taken of all radiative and autoionization processes involving a single-electron electricdipole transition of the recombining ion. The radiative energy loss processes considered are electron-impact excitation of resonance line emission, direct radiative recombination, dielectronic recombination, and electron-ion bremsstrahlung. For all three elements, resonance line emission resulting from 2s?2p transitions produces a broad maximum in the energy loss rate near 10⁵°K(～ 10 eV).     

Demonstration of high efficiency third harmonic conversion of high power Nd-glass laser radiation

We report on efficient conversion from 1.054 μm to 0.35 μm by third harmonic generation in two Type II KDP crystals. Energy conversion efficiencies of up to 80% have been measured under conditions applicable to large glass laser systems. A new tripling scheme used for these experiments requires a minimum of optical components and is insensitive to exact crystal alignment and laser beam divergence. A convenient scaling law allows tripling optimization for many different laser conditions.