Ultra-low threshold photonic crystal quantum dot laser

Photonic crystal microcavities can provide small mode volumes on the order of one wavelength cubed. As a consequence, spontaneous emission coupling of the gain medium into spurious modes is highly suppressed and the threshold pump power for lasing activity can be very low [1]. We have fabricated 2D photonic crystal microcavities with embedded self-assembled InAs/GaAs quantum dots as active material. Single mode emission with quality factors up to 10000 has been found for various L3-type cavity geometries covering the wavelength region of 910-970 nm. Single mode lasing under optical excitation is characterized by line width narrowing and record low threshold pump powers down to 160 nW, corresponding to a high degree of spontaneous emission coupling efficiency. Together with active positioning schemes of the mode maximum with respect to the quantum dot location [2], this type of microcavity is highly attractive for reaching the regime of single quantum dot lasing. [1] G. Bjoerk, A. Karlsson, and Y. Yamamoto, Phys. Rev. A, \textbf{50}, 1675 (1994). [2] K. Hennessy et al., Photonics and Nanostructures -- Fundamentals and Applications 2 (2) 65-72 (2004).