Multi-channel Hybrid Integrated Light Source for Ultra-high-bandwidth Optical Interconnections and Its Structural Optimization for Low Power Consumption by Considering Thermal Interference between LD Arrays

Abstract

The overall interchip bandwidth in central processing units (CPUs) used for high-end servers is expected to reach the 10-Tbit/s level by the late 2010s. Multi-core CPUs, 3D-memories, and 3D solid state drives are expected to be integrated on a silicon optical interposer that will support high-bandwidth optical interconnects among the components in an on-chip server targeted for development in the 2020s.[1] Optical interconnection using silicon photonics is a promising solution to the problem of bandwidth bottleneck among LSI chips because of the intrinsic properties of optical signals and the compatibility with complementary metal oxide semiconductor process technology. We previously proposed a photonics-electronics convergence system in which a continuous wave (CW) light source, optical modulators, and photodetectors are linked by silicon optical waveguides on a silicon interposer and LSI chips are mounted and electrically connected to the optical modulators and photodetectors.[2-4] In this system, the integrated CW light source must be multi-channel, and have high density and high power. An over-1,000-channel light source is required to reach a bandwidth of around 10-Tbit/s, if 10 Gbit/s per channel is assumed. We previously developed a hybrid integrated light source with a laser diode array on a silicon optical waveguide platform,[5] demonstrated a light source with over 100 output ports in which the number of output ports is increased by using a waveguide splitter and multichip bonding[6] and estimated the power uniformity of the output ports.[7] More recently, we demonstrated a hybrid integrated light source with over 1,000 channels.[8, 9] In this paper, we present a multi-channel hybrid integrated light source for ultra-high-bandwidth optical interconnections. In section 2, we describe its hybrid integration structure and fabrication technology. In section 3, we describe its optimization to reduce power consumption based on consideration of the thermal interference between the channels in a laser diode (LD) array and also

Fingertip-Size Optical Module, “Optical I/O Core”, and Its Application in FPGA

“…The LD is bonded with the AuSn solder bump on the circuit. Our LD bonding machine creates horizontal misalignment of ±0.5 μm between the LD and the silicon photonics integrated circuit by using infrared camera [8]. The vertical positioning is determined by the Si pedestals fabrication process.…”

Optical Characteristics of a Multichannel Hybrid Integrated Light Source for Ultra-High-Bandwidth Optical Interconnections

“…We fabricated a light source with 1000 output ports [8] in which the silicon optical waveguides were split into eight waveguides by using cascaded 1 × 4 and 1 × 2 multimode interferometer (MMI) splitters and in which five LD array chips with 25 channels were mounted on a silicon waveguide platform by multichip bonding [4] (Figure 1). The size of the light source was 9700 m × 1250 m.…”

“…The pitch of the output ports was set to 9 m in order to include 1000 ports in 1 cm, corresponding to the stepper shot size. The main structure of the light source is shown in Figure 2 [8]. Each LD in the array is a Fabry-Perot (FP) LD with a spot-size converter (SSC) including an inverse taper at the waveguide facet side and has a structure consisting of an InGaAsP base strained multiple-quantum-well buried heterostructure at a lasing wavelength of about 1.55m.…”

“…The power uniformity of the relative intensity is improved by thermal control. Since the LD mounting area on the platform was formed by removal of the BOX layer, the thermal impedance is relatively low, and the heat dissipation through the silicon substrate is effectively performed [8,9]. Figure 4 shows a relative intensity of the 1000 waveguide output ports in the light source at the silicon substrate backside temperature of 20 °C.…”

“…We previously developed a hybrid integrated light source with a laser diode (LD) array on a silicon optical waveguide platform [3] and demonstrated a light source with over 100 output ports in which the number of output ports was increased by using a waveguide splitter and multichip bonding [4,5]. Moreover, we demonstrated a hybrid integrated light source with over 1000 channels by showing the near field patterns of the output ports [6] and their structural optimization for low power consumption by considering the thermal interference between LD arrays [7,8].…”