= Continuous double heterostructure laser experiment
The experimental distinction is concrete. A 1962 <gallium arsenide> <p-n junction> <laser> used top and bottom contacts, parallel polished faces, and current pulses with the device in liquid nitrogen. An infrared image converter recorded the radiation pattern; a spectrometer measured narrowing above <laser threshold>. Comparing the same device below and above <laser threshold> supplied a control. Pulsed, cooled operation did not demonstrate continuous operation at room <temperature>.<Coherent Light Emission From GaAs Junctions by R. N. Hall and others>[pp. 366–367, Figs. 1–2]{ref}
<Zhores I. Alferov>'s 1970 team photolithographically patterned stripe <double heterostructure lasers> on silver-covered copper plates. He reports sustained <laser> emission at room <temperature>; Fig. 4 shows the device structure. Independently, <Izuo Hayashi>, <Morton B. Panish> and collaborators demonstrated continuous <double heterostructure laser> operation with diamond heat sinks.<Nobel Lecture: The double heterostructure concept and its applications in physics, electronics, and technology by Zhores Ivanovich Alferov>[§II, p. 770, Fig. 4]{ref}
The below-threshold comparison tests the onset of <stimulated emission>; continuous operation additionally requires sustained removal of waste <heat>. Neither observation alone measures the separate <band offsets>, optical overlap, or every loss mechanism. The schematic above therefore explains a design principle rather than reconstructing the historical apparatus.
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