A thin walled microtube is formed by providing a continuous elongated member having an outer surface. The first azo compound is preferably an azo compound wherein the azo group is bonded to an ortho-position of a hydroxyl group of an aminonaphthol skeleton. The pulse generators described herein utilize an adaptive threshold signal generator configured as a voltage divider and having resistive components having differing effective temperature coefficients of resistivity. The first polarizer is disposed at an outer side of the first substrate. Additionally, light-emitting efficiency can be improved since the conventional opaque substrate, such as a GaAs substrate.