Synchronous Amplitude Modulation of a Multimode Ring Laser
Department of Electrical Engineering, Stanford University., 1968 - Amplitude modulation - 104 pages
The work is concerned with theoretical and experimental properties of a He-Ne ring laser which has internal amplitude modulation. The modulation causes the light waves to travel as two oppositely directed pulses. This scheme was conceived in order to improve the lower limit of rotation rate sensing of the ring laser by reducing the interaction between counter-rotating waves. The expected improvement would occur because the two pulses would overlap only over limited portions of the ring perimeter, and hence interactions would occur only in the neighborhood of these pulse crossing positions. To obtain counter-rotating pulses, the ring laser is operated so that numerous axial modes oscillate simultaneously, one set corresponding to each direction, and the modulator frequency is chosen to be near the axial mode interval or a multiple thereof. Certain gain and refractive effects associated with the saturation of the active medium were observed when the ring laser was operated in this manner. Explanations of these effects were obtained using a simple model of the time variation of the population inversion of the active medium. A model accounting for the presence of internal reflections was also included. The experimentally observed behavior of the system was compared to the predictions of these models. (Author).
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2c/L system active atoms active medium amplitude modulation amplitudes and phases approximately asymmetry atoms with velocity axial mode interval Bahr equations beat frequency locking beat frequency offset bidirectional operation Brewster's angle calculate cavity Chapter coefficients corresponding coupled mode cross saturation double pulses dynamic inversion model electric field experimentally frequency and depth Fresnel drag gain profile gain vs frequency Harris and McDuff He-Ne homogeneous linewidth internal reflections inversion density isotope line center linear laser magnetic fields mode amplitudes mode locking mode ring laser mode spacing modulator depth modulator located multimode ring laser n+p n natural crossing obtained occur oppositely directed pulses oppositely directed waves optical optical cavity optical resonator optical spectrum parameter population inversion power dependent pulse crossing position pulse passes quantities reflection effects reflector relative amplitudes ring laser operating ring perimeter rotation beat frequencies saturation terms single mode ring single pass loss single pulses symmetry point