The Best Paper Award
High-Temperature Operation of Photonic-Crystal Lasers for On-Chip Optical Interconnection
Koji Takeda ，Tomonari Sato ，Takaaki Kakitsuka ，Akihiko Shinya ，Kengo Nozaki ，
Chin-Hui Chen ，Hideaki Taniyama ，Masaya Notomi ，Shinji Matsuo
（英文論文誌C　平成24年7月号掲載）
Koji Takeda Tomonari Sato Takaaki Kakitsuka Akihiko Shinya Kengo Nozaki  
Chin-Hui Chen Hideaki Taniyama Masaya Notomi Shinji Matsuo    
　The size of Si CMOS devices is continually being reduced to increase their speed, based on the scaling law. Interconnections in CMOS chips now account for more than half of the total power consumption. To reduce the power consumption in interconnections, on-chip optical interconnections have been widely studied. There are certain requirements for on-chip light sources for use in on-chip optical interconnections. The energy consumption should be smaller than 10 fJ to generate a single-bit signal. Also high temperature operation up to 80oC is necessary, which is the approximate CMOS operating temperature. In addition, a total bandwidth of 1 Tb/s is desired.
　To meet, in particular, the energy requirement, nanocavity lasers, which have small cavities and small active regions, have attracted great interest. Of the several types of nanocavity lasers, photonic-crystal (PhC) lasers are being actively studied, since their mode volumes are smaller than those of vertical-cavity surface-emitting lasers (VCSELs), and their output powers are larger than those of metallic nanocavity lasers. This paper reports results of PhC lasers developed by the authors. The authors embedded an ultra-small 3-quantum-well InGaAsP active region, which had a volume of 0.23 ?m3, in a line-defect PhC waveguide consisting of a 200-nm-thick InP membrane. Continuous-wave operation was achieved at up to 89.8oC, and the maximum output power was 100 ?W at room temperature. Small-signal measurements revealed that the PhC lasers had a 3-dB bandwidth of 11.6 and 7.0 GHz at room temperature and 66.2oC, respectively. PhC lasers with various lattice constants were fabricated simultaneously, and the lasing wavelength was experimentally controlled with an accuracy of ±1 nm. The availability of wavelength-division multiplexing is discussed in the context of wavelength accuracy and the temperature dependence of the lasing wavelength. The authors have demonstrated, for the first time, high-temperature operation of PhC lasers.
　As stated above, the results described in this paper are highly original, based on the authors' PhC lasers with embedded active regions. The high-temperature operation of PhC lasers is an important advance in implementing them on CMOS chips.

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