Takuma Aihara

Ultrahigh efficiency III-V on Si MOS capacitor optical modulator

A high-efficiency and low-loss Mach-Zehnder modulator on a Si platform is a key component for meeting the demand for high-capacity, low-cost and low-power optical transceivers in future optical fiber links. We report a III-V/Si MOS capacitor Mach-Zehnder modulator with an ultrahigh-efficiency phase shifter, which consists of n-type InGaAsP and ptype Si. The main advantage of this structure is a large electron-induced refractive index change and low free-carrier absorption loss of the n-type InGaAsP. The heterogeneously integrated InGaAsP/Si MOS capacitor structure is fabricated by using the oxygen plasma assisted bonding method. The fabricated device shows VπL of 0.09 Vcm, a value over three-times smaller than that of the conventional Si MOS capacitor Mach-Zehnder modulator, without an increase in the insertion loss. This clearly indicates that the proposed III-V/Si MOS capacitor Mach-Zehnder modulator overcomes the performance limit of the Si Mach-Zehnder modulator.

Ultra-high efficiency III-V on Si MOS capacitor Mach-Zehnder modulator

High-capacity optical transmitters with reduced size, cost, and power consumption are required to meet growing bandwidth requirements of network systems. A high-modulation-efficiency Mach-Zehnder modulator (MZM) on an Si platform is a key piece of equipment for these transmitters. Si-MZMs have been widely reported; however their performance is limited by the material properties of Si. To overcome the performance limitations of Si MZMs, we have integrated III-V materials on Si substrate and developed a heterogeneously integrated III-V/Si metal oxide semiconductor (MOS) capacitor phase shifter for constructing ultra-high efficient MZM, in which the n-InGaAsP, p-Si, and SiO2 film are used for constructing the MOS capacitor. The fabricated MZM with the MOS capacitor exhibited a VπL of 0.09 Vcm and insertion loss of ~2 dB. 32-Gbps modulation of the MZM was also demonstrated.

Deuterated SiN/SiON Waveguides on Si Platform and Their Application to C-Band WDM Filters

We describe low-loss SiN/SiON waveguides for wavelength-division-multiplexing filters on a Si platform. The key technology is a low-temperature deposition of refractive-index-controllable SiN/SiON films by using a hydrogen-free gas source (SiD4), which avoids the strong optical absorption due to N-H bond. Using this technology, we demonstrate a low-loss ring resonator with a SiN waveguide, whose loss is 0.47 dB/cm at 1550 nm. It shows excess loss of 2.7 dB, a 3-dB bandwidth of 0.13 nm, and an extinction ratio of 27 dB in the entire C band. In addition, we also demonstrate a polarization-insensitive arrayed-waveguide grating with a SiON waveguide, whose loss is 0.29 dB/cm at 1550 nm. It shows insertion loss of 5.3 dB, crosstalk of less than −27 dB, and polarization insensitivity in the entire C band.