The Dynamics and Coherent Properties of Electron - Pumped Semiconductor Lasers.
In this work the dynamics and coherence properties of electron beam pumped visible semiconductor lasers have been studied over a wide range of operating conditions. Experiments were conducted on a specially designed and built demountable cathode-ray tube (CRT) system, enabling quick processing of samples, efficient excitation and simultaneous acquisition of optical and electrical data. The problem of achieving adequate e-beam density and spotsize necessary to attain lasing threshold is solved by means of an electron gun analysis and design procedure. Both theoretical and numerical methods are employed, resulting in high-density electron guns capable of lasing all of the II-VI compounds studied. Cathodoluminescence and lasing properties of ZnCdSe were studied over a wide range of temperatures and excitation conditions using the demountable CRT. Lasing was observed to occur in the range of wavelengths from yellow to red. Based on the results of the experiments, gain and absorption spectra under different conditions are calculated. The dependence of bandgap energy on excitation density is studied and provides an explanation for the observed dependencies of laser threshold on penetration depth at different temperatures. The influence of the external and internal resonator parameters on the laser emission spectral and spatial characteristics is investigated. Single longitudinal mode operation of an electron beam pumped visible semiconductor laser with an external resonator was observed. A single-mode peak power of 0.8 watts and a beam divergence of less than 3 degrees was achieved. Linear and non-linear theories of amplified spontaneous emission in longitudinally-pumped semiconductor lasers were developed. Experiments were performed to investigate the dependence of lasing threshold and differential efficiency on excited region diameter. The results of the threshold measurements are in good agreement with calculations based on the linear theory, while the differential efficiency measurements required the development of a non-linear theory for agreement with experiment. Steady-state and transient behavior of a longitudinally pumped semiconductor laser are theoretically investigated using a rate equation model with distributed gain and photon density. The results offer an explanation for the observed non-linear behavior of electron beam pumped lasers. (Abstract shortened with permission of author.).
- Pub Date:
- November 1987
- Physics: Optics