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Buried-heterostructure injection lasers which have the filamentary GaAs active regions completely surrounded by Ga1−xAlxAs are proposed and have been successfully fabricated by using two-step liquid-phase-epitaxial techniques. The active regions of these lasers can be made extremely small and do not have dimensional unbalances encountered in conventional injection lasers. The threshold current has been reduced to a value as low as 15 mA by applying current-confining geometry to this laser. A study of optical characteristics has revealed such improvements over ordinary lasers as Gaussian beam profile, fundamental mode (TE00) operation, mode reproducibility, and mode stability. Due to the superior thermal properties of these lasers cw operation was easily obtained.
T. Tsukada (Fri,) studied this question.