I. On the Application of a Laser to High Speed Photography. II. Torsional Magnetoelastic Waves in a Circular Cylinder

Citation

Fourney, Michael Eugene (1963) I. On the Application of a Laser to High Speed Photography. II. Torsional Magnetoelastic Waves in a Circular Cylinder. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/6M9E-V056. https://resolver.caltech.edu/CaltechETD:etd-12082005-131705

Abstract

The first part of this thesis deals with the application of a ruby laser to high speed photography. The light that is emitted from a ruby laser is monochromatic, collimated, coherent, linearly polarized, and highly intense. It has been demonstrated that these properties make the laser a very useful tool for research in areas involving photographic techniques. A method has been devised by which the output of the laser is controlled and is emitted in the form of a series of light pulses. The rate at which these pulses are generated can be controlled and repetition rates of over 1.6 Mc/sec have been achieved. The 30 nsec duration of an individual pulse represents the exposure time for a high speed laser camera which has been developed. Pictures have been taken at rates of over 1.2 million frames per second. This exposure time represents a reduction of an order of magnitude over that previously possible, with an increase of three orders of magnitude in intensity. In applications where a particular characteristic of the laser light is required, such as the monochromatic nature desired in photoelasticity, this improvement of four orders of magnitude is further increased. When a series of light pulses is generated in the manner described above it is found that the amplitude of the pulse train becomes stable above a certain critical frequency. This critical frequency is determined to be a function of the laser cavity length. The amplitude of the stabilized pulse train is a function of the repetition rate and the cavity length. The nature of this variation is established and a mechanistic explanation of the phenomena involved is presented.

Thesis Files