A GaAs/AlAs coupled multilayer cavity structure was grown on a (001) GaAs substrate. The top cavity contains self-assembled InAs quantum dots (QDs) as optical gain materials for two-color emission of cavity-mode light. The bottom cavity layer was grown with lateral thickness variation in the wafer to investigate the effects of the thickness difference between the two cavity layers quantitatively. The frequency difference was minimum, and the intensity ratio of the two-color emission was unity when the optical thicknesses of the two cavity layers were the same. The emission intensity ratio was explained in terms of the electric fields at the top cavity region containing the QDs.

Two‐color lasing in a GaAs/AlAs coupled multilayer cavity has been studied for a novel type of terahertz emitting devices. In the structure, two cavity layers based on GaAs were connected by the intermediate GaAs/AlAs distributed Bragg reflector multilayer and three layers of self‐assembled InAs quantum dots (QDs) were inserted only in the top‐side cavity layer as optical gain materials. The broadened QD emissions around 1.25 µm are very useful to realize the optical gain because they could cover the wide range of the mode frequency difference. Two mode emissions with an optical frequency difference of 3.2 THz were successfully demonstrated under room temperature cw operation by optical pumping. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A GaAs/AlAs coupled multilayer cavity structure with InAs quantum dots (QDs) was fabricated by wafer-bonding of two cavity structures grown individually. The wafer-bonding technique is important to control the spatial distribution of nonlinear polarization for strong terahertz emission by the differential frequency generation of the two cavity modes of the coupled cavity. Three layers of self-assembled InAs QDs were inserted in a cavity grown on a (001) GaAs substrate as optical gain materials for two-color emission of the cavity mode lights. The other cavity with a GaAs cavity layer was grown on a (113)B GaAs substrate. Two-color emissions with a 3.8 THz frequency difference were successfully observed from the wafer-bonded coupled cavity by cw optical pumping at room temperature.

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