Second-harmonic imaging in the scanning optical microscope

A reaction chamber having a bottom which is a wafer mount and dome member; a plurality of gas inlet pipes positioned at the lower part of the reaction chamber for introducing gas into the reaction chamber so as to cause streams of gas therein to whirl along the inner wall of said chamber; an exhaust for expelling waste gas from the lower part of the vortex center of whirling gas in the reaction chamber; and heating means provided outside of the reaction chamber for its heating. The reaction chamber preferably contains a reaction gas inlet pipe having its opening positioned upwardly facing the upper central part of the inner wall of said done member.