Abstract: A process of producing a diffraction grating includes the steps of forming a coating layer on a first diffraction grating layer of a resin formed on a substrate without damaging the diffraction grating layer, removing a portion of the coating layer positioned on the first diffraction grating layer by etching to form a second diffraction grating layer of the coating layer having the reverse phase to that of the first diffraction grating layer, removing the first diffraction grating layer, and etching the substrate with a mask of the second diffraction grating layer, so that the diffraction grating having the reverse phase can be easily produced. When the first diffraction grating layer is left and both the first and second diffraction grating layers are used as a mask, the diffraction grating having a period half times as large as that of the first grating layer can be easily produced.

Abstract: A process of producing a diffraction grating comprises the steps of forming a coating layer on a first diffraction grating layer of a resin formed on a substrate without damaging the diffraction grating layer, removing a portion of the coating layer positioned on the first diffraction grating layer by etching to form a second diffraction grating layer of the coating layer having the reverse phase to that of the first diffraction grating layer, removing the first diffraction grating layer, and etching the substrate with a mask of the second diffraction grating layer, so that the diffraction grating having the reverse phase can be easily produced. When the first diffraction grating layer is left and both the first and second diffraction grating layers are used as a mask, the diffraction grating having a period half times as large as that of the first grating layer can be easily produced.

Abstract: An avalanche transistor has a heterojunction emitter-base junction. The avalanche transistor includes a spacer layer provided between an emitter layer and a base layer. The spacer layer has an energy band gap between that of the base layer and that of the emitter layer, a carrier concentration lower than that of the base layer, and a thickness so that the whole spacer layer becomes a depletion layer at thermal equillibrium so that a neutral region is produced in the spacer layer at a voltage lower than the threshold voltage of the emitter-base junction. Thus, the same element is both bistable with the base current as a parameter and has an S-shaped negative differential resistance with the base voltage as a parameter.