中国科学 : 信息科学 第 45 卷 第 4 期 图 1 (a) CTS 结构; (b) 传统 clock Mesh 结构 Figure 1 (a) CTS structure; (b) conventional clock Mesh structure Clock Mesh 则是通过短接在一起的时钟布线网格来实现时钟信号的接近零偏差的传播, 如图 1(b) 所示. 其将每一个 Mesh driver 的输出短接在一起, 使得时钟信号能够非常快的, 并且几乎同时到达每 个受驱动节点. 高性能微处理器一般采取这种方式. 但 clock Mesh 的时钟功耗较大 [5] , 占用的布线资 源较多, 且根据图 1(b), 在 Mesh 网格之后还存在一定级数的时钟驱动缓冲器, 同样难以做到真正的零 偏斜的传播时钟信号.

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Vertical cavity surface emitting lasers (VCSELs) offer the great advantages over conventional edge-emitting lasers, such as extremely low threshold current, single longitudinal mode, especially surface emission laser with very small beam divergence and simple fabrication in large two-dimensional (2D) arrays, which make VCSEL based smart components that integrated photonic devices and microelectronic circuits, very well suited for high density parallel optical interconnects and optical switching networks.We designed and fabricated the hybrid integrated CMOS-VCSEL multiple chip modules. The VCSEL operate at 85Onm wavelength. A typical VCSEL has a threshold current of 4 mA and quantum eficiency of 0.3 mWimA. Operating at 8 mA modulation current, the VCSEL 3 d B modulation bandwidth was measured more than 5 GHz. The VCSEL array chips used for module have 1x16 array structure and pitch of the VCSEL is 250pm. The circuits were designed using 0 . 3 5~ CMOS technology. Fig. 1 shows the circuit schematic of VCSEL array drivers. The supply voltage Vta is used to set the VCSEL bias for different threshold current. By raising the supply voltage Vd, the modulation curreht can be increase. It allows 0-161x4 rang for the different modulation currents and meets the need of driving different VCSELs. The circuits have been realized by TSMC in Taiwan, through the MOSIS program of USA. Fig. 2 shows micrograph of the 16-channel 0.35 pm CMOS circuit chip. The CMOS IC 3-dB modulation bandwidth was measured more than 2.2 GHz.We demonstrated the 16-channel laser simultaneous working in the hybrid integrated CMOS-VCSEL multiple chip modules as shown in Fig. 3. Die-&die wire bond was used to connect the VCSEL array devices and outputs of the CMOS IC chip. The CMOS-VCSEL multiple chip modules operated at 8 mA modulation current and 3.3V power supply. Fig. 4. shows the measured frequency performance of the CMOS-VCSEL module. The measurement of the 3-dB frequency bandwidth is more than 2 GHz. The CMOS-VCSEL modules could be used in free space optical interconnects (FSOI).Vertical cavity surface emitting lasers have unique features and are the capability of integrated with state-of-the-art electronic circuits. VCSEL based multiple chip modules have enabled developments of low cost Gbitls serial optical links and IO Gbit/s parallel optical links for high-speed interconnection at very short reach (VSR) network system.

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