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A simple method for the fabrication of Fabry–Perot mirrors of InGaAsP/GaAs lasers is presented. The vertical and smooth wall etching is done for active layers only (not for both active and cladding layers), by an H2SO4:H2O2:H2O=3:1:1 etchant for 2–5 s. Since the active layers are much thinner than the cladding layers, the etching becomes much easier. The threshold current density of the etched mirror laser is ∼4.4 kA/cm2, about 1.1 times that of the cleaved laser, and the mirror reflectivity is evaluated as 29.4% (cleaved 31.4%).

Bis(9-triptycyl) sulfides were prepared by pyrolytic extrusion of sulfur dioxide from the corresponding thiosulfonates. A pair of torsional motions about the CS bonds in these sulfides are in strict gearing and require a barrier of 29.3 ± 0.3 kcal/mol for gear slippage.

The internal loss α and gain factor β of InGaAsP/GaAs double-heterostructure lasers were examined by immersing laser chips into various liquids and changing the reflectivities of a Fabry-Perot mirror. Only a small scatter was found; we evaluated α and β as 20.6 cm-1 and 0.0129 cm·A-1, respectively. The value of α was compared with the loss of AlGaAs/GaAs lasers.