A simple method for measuring the linewidth enhancement factor alpha of a semiconductor laser by optical injection locking is described. Without knowledge of the absolute values of detuning and the optical injection level, the value of alpha is evaluated from only changes in optical power in the stable optical injection-locking state. The value of alpha of a 0.83-microm channeled substrate planar laser is evaluated to be 2.65 +/- 0.2. The measurement error of this method is also discussed.
A resonator method is used to demonstrate Landau-damping of surface waves along a plasma column. As a method of plasma diagnostics, an open plasma resonator utilizing longitudinal resonance of the surface wave has been proposed by one of us. This work presents an analysis of anomalous damping in terms of the Q factor observed in the open plasma resonator. In the analysis, the effect of energy absorption by the thermal electrons travelling across the side boundaries of the resonator is accounted for. A method of single-mode excitation which is convenient for experimental determination of the Q factor is also described. The results of Q measurements are compared with the computer solutions; the Landau-damping mechanism which is responsible for the anomalous damping in the Q factor is examined.
A method for determining electron density in cylindrical plasma columns uses surface wave resonances which occur when the length of plasma column is an integral multiple of the half-wavelength of the surface wave. One type of resonance is in an axially symmetric mode, the other in a dipolar mode. A theory is given for the relation of resonance frequency to electron plasma frequency. Experiments were carried out with both propagation modes excited simultaneously; the axially symmetric resonances are at much lower frequencies than the electron plasma.
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