50

nanotimes News in Brief

12-03 :: March/April 2012

Scanning electron microscope image of the silicon-based micro-loop mirror. Light entering the waveguide from the left is guided around the loop and redirected back into the laser structure. The inset shows the laser spot photo- graphed with an infrared camera. ©

Yunan Zheng, Doris Keh-Ting Ng, Yongqiang Wei, Wang Yadong, Yingyan Huang, Yongming Tu, Chee-Wei Lee, Boyang Liu, and Seng-Tiong Ho: Electrically pumped he- terogeneously integrated Si/III-V evanescent lasers with micro-loop mirror reflector, In: Applied Physics Letters, Volume 99(2012), Issue 1, Article 011103[3 pages], DOI:10.1063/1.3607309: http://dx.doi.org/10.1063/1.3607309

cation techniques, and device performances can suffer as a result. Furthermore, any laser requires mirrors to maintain lasing action. Typically, such designs rely on the interface between air and the semiconductor, that is, the facets of the chip. These mirrors are not perfect and further reduce operation efficiency.

To improve on the latter aspect, the researchers have now come up with a unique mirror design, known as a micro-loop mirror (MLM). Light emit- ted from one end of the laser is guided along the waveguide, around a narrow bend and is then di- rected back into the device (see image). The mirror at the other end of the device is still formed by the interface with air, so that laser radiation can exit the device. The MLM achieves a remarkable 98% reflection efficiency of light. Such low losses mean that the MLM laser is comparatively efficient.

Scientists from the University of Florida (US) have developed a promising new technique for creating graphene patterns on top of silicon carbide (SiC). The Florida team’s technique allowed the resear- chers to confine the growth of graphene to a de- fined pattern as small as 20nm. The team found that implanting silicon or gold ions in SiC lowered the temperature at which graphene formed by appro- ximately 100° Celsius (212° F). The team implan- ted ions only where graphene layers were desired, and then heated the SiC to 1,200° Celcius (2,192° F). At this temperature the pure SiC did not form graphene, but the implanted areas did. Using this technique, the team successfully created graphene nanoribbons. © AIP

S. Tongay, M. Lemaitre, J. Fridmann, A. F. Hebard, B. P. Gila, and B. R. Appleton: Drawing graphene nano- ribbons on SiC by ion implantation, In: Applied Phy- sics Letters, Vol. 100(2012), Issue 7, Article 073501, DOI:10.1063/1.3682479 [3 pages]: http://dx.doi.org/10.1063/1.3682479