Effect of sample sizes in terahertz emission from intrinsic Josephson junctions in cuprate HTSC

Effect of sample sizes in electromagnetic wave emission from intrinsic Josephson junctions is investigated numerically. By using material parameters of Bi2Sr2CaCu2O8Bi2Sr2CaCu2O8, emission frequency becomes as large as 1 THz for a few dozens of layers. Frequencies at intensity peaks can be described well as the in-phase cavity resonance of transverse plasma. As the sample width increases, peak intensity gradually increases and then saturates. When the width exceeds a critical size, intensity peak becomes almost flat and such plateau region broadens as the width further increases. These behaviors can be explained by the mixing of two nearby cavity modes.