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Laser emission was observed in photonic semiconductor dots with a discretized optical mode spectrum. The photonic dots with lateral sizes between 1 and 5 μm provide a three-dimensional optical confinement by using in the vertical direction AlAs/GaAs Bragg mirrors and in the lateral directions the refractive index discontinuity at the etched surfaces. In the optically pumped structures, the laser emission takes place on the fundamental mode of the microcavities. External threshold excitation densities of 200 W/cm2, which correspond to a very low internal optical excitation power of 0.15 μW per microcavity post, were measured for microcavity structures with a lateral size of 2.7 μm.

Optically pumped three-dimensionally confined microcavity lasers were fabricated by electron beam exposure and dry chemical etching with lateral sizes between 1 -5 p. These photonic quantum dot lasers exhibit a well pronounced optical mode spectrum below threshold with a large mode splitting. Abve threshold lasing takes place in the fundamental mode with fourier transform limited line widths. Due to the enhancement of the coupling of the spontaneous emission into the lasing mode a significant reduction of the threshold density was observed by reducing the lateral size in comparison to planar vertical cavity emitting structures.

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