Engineering topics
Publications and source records attributed to Evans, G..
A wavelength-locked, AlGaAs channeled-substrate-planar distributed feedback laser has been made that operates to 40 mW pulsed. The Bragg grating is situated at the shoulders of the layers of AlGaAs and GaAs. Overall power efficiencies of 15 percent have been measured at 40 mW of output power.
Optimum threshold conditions are derived for oscillations of transversely bounded distributed-feedback lasers in the cases of fiber and diffused waveguides, and it is shown that these structures are feasible with available active materials. The results of calculations show that a fiber laser has an optimum operating region which requires the least gain for self-sustained oscillation, while optimum operation occurs at the highest frequency possible in a diffused waveguide. It is noted that these gains can be achieved with dye in the case of a fiber waveguide and with dye or semiconductors in the case of a diffusion guide.
Bounded distributed-feedback (DFB) lasers are studied in detail. Threshold gain and field distribution for a number of configurations are derived and analyzed. More specifically, the thin-film guide, fiber, diffusion guide, and hollow channel with inhomogeneous-cladding DFB lasers are considered. Optimum points exist and must be used in DFB laser design. Different-modes feedback and the effects of the transverse boundaries are included. A number of applications are also discussed.
The use of zeolite crystals in distributed feedback crystal cavities for X-ray emissions is proposed. The zeolite crystals can guide the emitted X rays and can also generate the feedback necessary for self-sustained oscillation. A table lists the parameters of some typical zeolite crystals.
Diffused optical waveguides are studied using the modal and the ray tracing approach, with an emphasis on the case of a hollow waveguide with diffuse cladding. The properties of the guided modes are investigated in detail. The applications of these structures to optical circuits, integrated optics lasers and capillary gas lasers are discussed.