Operation of a Smith-Purcell free-electron laser at submillimeter wavelengths
Abstract
Experimental results demonstrating Planar Orotron operation in the submillimeter wavelength regime of 1 cm to 400 microns are presented. This device belongs to the class of Smith-Purcell free-electron lasers that utilize periodic metal grating structures to support electromagnetic waves with phase velocities slower than the speed of light. The J(vector) * E(vector) interaction between this slow wave and a mildly relativistic electron beam (15-130 keV) produces coherent radiation. Dispersion, electronic tuning, single particle gain, and start oscillation current expressions are developed for unique grating geometries that are seen to possess superior high frequency and tuning capabilities. Experimental data taken over a wide spectral range is extensively compared to the theoretical developments and excellent agreement is seen. Comparing the experimentally measured power of the device to a generic power model has resulted in valuable insights into designing device parameters that will optimize short wavelength operation. The experimental observation of multiple modes of laser operation has led to the development of several new models of how the device works, including one that links the TM dispersion formalism with the viewpoint of Smith and Purcell. This viewpoint is significant in that it allows for a statement on the ultimate short wavelength limits of the device to be made.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1991
- Bibcode:
- 1991PhDT........33P
- Keywords:
-
- Beam Interactions;
- Coherent Radiation;
- Free Electron Lasers;
- Laser Beams;
- Microwave Tubes;
- Relativistic Electron Beams;
- Submillimeter Waves;
- Electromagnetic Radiation;
- Phase Velocity;
- Tuning;
- Lasers and Masers