ULTIMATE LOW THRESHOLD AND LARGE SCALE INTEGRATION OF SEMICONDUCTOR MICRODISK LASERS

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In this study, we investigated the size reduction, threshold reduction, and the realization of the spontaneous emission control such as Purcell effect in microdisk semiconductor lasers, and their high integration and the formation for photonic molecule. First, we achieved the room temperature continuous wave operation of GaInAsP device by photopumping. The smallest diameter of the device was 1.7 microns, which is the same as the smallest record of this device. In addition, the lowest threshold was as low as 19 microns, which is the lowest record for GaInAsP lasers. We also integrated the metal electrode and observed the current injection lasing. In this experiment, an athermal effect in the polyimide cladding layer was discovered, which stabilizes the lasing wavelength. Then, we proposed a microgear cavity having a rotationally symmetric grating along the periphery of the microdisk. We theoretically found that the gear shape essentially improves the cavity Q factor. Actually, we successfully reduced the threshold to 14 microwatts. The spontaneous emission factor of these devices were evaluated to be over 0.1, which is close to the large Purcell factor of 6.7 was 0.1 micros to form a photonic molecule. A unique mode splitting, anti-crossing characteristics, miniband formation and bistable characteristics were observed for the photonic molecule, which are promising for future functional photonic circuits and photonic memories.