A STUDY OF GENERATION IN NONAXIAL DIRECTIONS ON NEODYMIUM GLASS SAMPLES OF CYLINDRICAL FORM,
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO
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Results are given of a systematic experimental investigation of laser emission in extra-axial directions. The specimens were cylindrical and square glass rods with semi-reflecting ends and highly polished lateral surfaces. Optically uniform neodymium glass was used. Emission on a wavelength of 1.06 microns was recorded both photoelectrically and photographically. Distribution of radiative energy on the end of the specimen takes the form of rings, with no emission in the axial modes at pumping energies slightly higher than the emission threshold value 20. Increasing the pumping energy leads to the appearance of more rings with a different emission threshold for each of them. Emission was observed at considerable angles to the axis of the speciments up to 70 deg.. When the lateral surfaces of the specimens were properly finished, no axial emission was observed even when the pumping energy exceeded the emission threshold by a factor of three. The actual path of the beam within the specimen was determined by studying the distribution of radiative energy in the near and far zones. It was found that the beam follows a closed three-dimensional path within the laser. The time relationship between various points in the far zone was also studied.
- Lasers and Masers