Simple expression of laser diode multimode rate equations including band filling effects
By introducing semiconductor gain into common laser diode multimode rate equations, we have found that the differential gain coefficient and the carrier density at transparency have a linear dependence with wavelength. Based on this fact, we have derived a simple expression for the laser diode gain including band filling effects.
Suppression of Side Fringes in Low-Coherence Interferometric Measurements Using Gain- or Loss-Modulated Multimode Laser Diodes
We examined three commercially available Fabry–Perot laser diodes with different oscillation wavelengths (660, 800, and 1550 nm) to suppress side fringes appearing under gain- or loss-modulation operation in low-coherence interferometric fringe measurements. For the shorter-wavelength laser diodes (660 and 800 nm), the amplitude of the maximum side fringe was effectively suppressed to 4% of the main fringe amplitude by utilizing the linewidth broadening effect of gain-switched laser diodes due to the generation of frequency chirping, and also by superimposing a multimode spectrum from another laser diode of the same kind. For the 1550 nm laser diode, however, the above approaches were less effective because noticeable gain saturation in the laser diode disturbed the transition of the spectral shape from a characteristic multimode spectrum to a continuum.
Geomagnetic micropulsations due to the motion of ocean waves
When sea waves move in the magnetic field of the earth, electric currents are generated in the water volume. These currents give rise to a small magnetic field which perturbs the earth's field. For plane trochoidal waves, this perturbing field decays exponentially with altitude and lies in a vertical plane which is oriented in the direction of wave propagation. The magnitude of the perturbing field also depends upon the magnitude and dip angle of the earth's field, and upon the height, wavelength, and propagation direction of the sea waves. For north-south waves, sea state 5, and an altitude of 100 feet, the perturbation is of the order of 0.1 gamma.