Abstract: An electromagnetic wave generator encompasses a first pump beam emitter (2) configured to emit a first pump beam (hv1) having a wavelength larger than one micrometer; a second pump beam emitter (25) configured to emit a wavelength-tunable second pump beam (hv2) having a wavelength larger than one micrometer, the wavelength of which is different from the wavelength of the first pump beam (hv1); a nonlinear optical crystal (19) configured to generate an electromagnetic wave (hv3) of a difference frequency between the first pump beam (hv1) and second pump beam (hv2); and an optical system (M1, M2, 18) configured to irradiate the first pump beam (hv1) and second pump beam (hv2) to the nonlinear optical crystal (19), by adjusting an external intersection angle between the first pump beam (hv1) and second pump beam (hv2) within 0.5° at the difference frequency of 1 THz.

Abstract: An electromagnetic wave generator encompasses a first pump beam emitter (2) configured to emit a first pump beam (hv1) having a wavelength larger than one micrometer; a second pump beam emitter (25) configured to emit a wavelength-tunable second pump beam (hv2) having a wavelength larger than one micrometer, the wavelength of which is different from the wavelength of the first pump beam (hv1); a nonlinear optical crystal (19) configured to generate an electromagnetic wave (hv3) of a difference frequency between the first pump beam (hv1) and second pump beam (hv2); and an optical system (M1, M2, 18) configured to irradiate the first pump beam (hv1) and second pump beam (hv2) to the nonlinear optical crystal (19), by adjusting an external intersection angle between the first pump beam (hv1) and second pump beam (hv2) within 0.5° at the difference frequency of 1 THz.

Abstract: A far-infrared electromagnetic wave generator comprises a semiconductor containing at least one impurity which has an energy difference, close to a quantum energy of optical phonon, between its transition levels; a resonator having two reflectors for effecting positive feedback of an electromagnetic wave corresponding to the quantum energy; and means for applying an electric current across the semiconductor. The semiconductor may have p-i, n-i, p-i-n, p-n, or n-p.sup.- junction. One of the reflectors of the resonator may have a diffraction grating so that the wavelength of the electromagnetic wave to be generated can be varied by adjusting an angle of the diffraction grating.

Abstract: A single crystal of gallium phosphide including 0.5 atomic ratio or less of indium is grown from a melt consisting of indium, gallium and phosphorous with an atomic ratio of gallium to phosphorous equal to at least 2.0.