The behavior of mode locking has been introduced in detail with respect to gaseous and solid lasers. There are two types of mode-locked lasers, which are classified as AM (Amplitude modulation) type and FM (frequency modulation) type. The former, which is realized by virtue of the internal loss modulation or the nonlinearity of laser medium, emits a train of ultra-high speed light pulse, whereas the latter, which is realized by the internal phase modulation only, emits a frequency-modulated light wave. The mode-locked laser of AM type with m light pulses bouncing back and forth between both the end mirrors oscillates ordinarily at mƒp mode interval (ƒp is the fundamental axial mode interval) and exceptionally at 1ƒp mode interval. The condition of these lockings is discussed concerning mirror separation as well as oscillation intensity and proved to concern closely the decay constants, etc., of laser medium. Some special considerations on the realization of mode locking are also given. Such mode-locked lasers will be applied to ultrahigh speed PCM communication, ultra-high speed photograph, generation of single-frequency light, and so on.
Thin films of iron oxides (Fe3O4 and γ-Fe2O3) were prepared by flash evaporation onto glass plates maintained at 100°C in vacuum of 2×10-5mmHg. Their thickness ranged from 600Å to 3500Å. Their crystal structure was examined by electron diffraction and their magnetic property by ferromagnetic resonance (FMR) in the course of heat treatment at various atmospheric pressures. Flash evaporation is effective in preparing a γ-Fe2O3 film but is not effective in preparing a Fe3O4 film: FMR in the former film shows a single peak of γ-Fe2O3, but in the latter film peaks of Fe3O4 and / or Fe as well as γ-Fe2O3 were observed. When the latter film is annealed at 300°C in vacuum of 5×10-3mmHg, it can grow into a pure Fe3O4 film. Spin wave resonance failed to be observed in both γ-Fe2O3 and Fe3O4 films.
A 2 MeV electron linear accelerator or π/2 mode travelling wave type has been designed and built. The accelerating microwave frequency is 8976 Mc/s. The RF structure of the S-band MARK-IV accelerator at Stanford University (2856 Mc/s) is scaled down to X-band. In order to comply with the decrease of the electric field strength, several additional cavities are interposed in the buncher section. The RF power of 200 kW is supplied by a frequency-tunable magnetron, The injection energy of electrons is 185 keV. The RF phase velocity increases from 0.6556c to 0.9400c in the buncher, and stays at 0.96c in the regular section. The electron energy obtained is 1.8 MeV with output current of 10 mA, pulse length 2μsec, and pulse repetition rate 50, 100, 200 pps.