Integration of a high-efficiency Mach-Zehnder modulator with a DFB laser using membrane InP-based devices on a Si photonics platform

Abstract

We demonstrate a wafer-level integration of a distributed feedback laser diode (DFB LD) and high-efficiency Mach-Zehnder modulator (MZM) using InGaAsP phase shifters on Si waveguide circuits. The key to integrating materials with different bandgaps is to combine direct wafer bonding of a multiple quantum well layer for the DFB LD and regrowth of a bulk layer for the phase shifter. Buried regrowth of an InP layer is also employed to define the waveguide cores for the LD and phase shifters on a Si substrate. Both the LD and phase shifters have 230-nm-thick lateral diodes, whose thickness is less than the critical thickness of the III-V compound semiconductor layers on the Si substrate. The fabricated device has a 500-µm-long DFB LD and 500-µm-long carrier-depletion InGaAsP-bulk phase shifters, which provide a total footprint of only 1.9 × 0.31 mm2. Thanks to the low losses of the silica-based fiber couplers, InP/Si narrow tapers, and the phase shifters, the fiber-coupled output power of 3.2 mW is achieved with the LD current of 80 mA. The MZM has a VπL of around 0.4 Vcm, which overcomes the VπL limit of typical carrier-depletion Si MZMs. Thanks to the high modulation efficiency, the device shows an extinction ratio of 5 dB for 50-Gbit/s NRZ signal with a low peak-to-peak voltage of 2.5 V, despite the short phase shifters and single-arm driving.

Heterogeneously-Integrated Optical Phase Shifters for Next-Generation Modulators and Switches on a Silicon Photonics Platform: A Review

“…They recently reported a high-efficiency MZ modulator integrated with a DFB laser using membrane InP-based devices on an Si photonics platform. The latest work [63] shows a higher V π L of 0.4 Vcm compared to their previous work, but the measured 3-dB bandwidth is around 31 GHz which is much more practical for high-speed modulators. Finally, they demonstrated eye diagrams with a 50-Gbps NRZ signal using the integrated DFB laser diode and high-efficiency InGaAsP MZM.…”

“…One main drawback of SiGe is that free-carrier absorption is also increased by straininduced effective mass modulation with an increase in the plasma dispersion effect, which was also experimentally reported and shown in Figure 2b. In terms of that, III-V materials have the advantageous inherent property in which free-carrier absorption is reduced while the plasma dispersion effect is enhanced for electrons [60][61][62][63][64]. In 1990, B. R. Bennett et al investigated the carrier-induced change in the refractive index of III-V compound semiconductors, InP, GaAs, and InGaAsP [60].…”

“…This tradeoff relationship is determined by material properties; thus, material engineering is important to overcome this trade-off relationship. III-V compound semiconductors are a comparable candidate to achieve large phase modulation with a small optical loss [61][62][63][64]67]. The hybrid SIS structure with n-type III-V and p-type Si is especially efficient in reducing hole-induced loss of III-V materials; thus, relatively low crosstalk can be achieved [105].…”

50-GHz-Bandwidth Membrane InGaAsP Electro-Absorption Modulator on Si Platform

“…This is beneficial for integrating the EAM with an LD by using a regrowth process. In our previous work, a membrane DFB laser was integrated with an InGaAsP MZM on Si-waveguide circuits by combining direct bonding of a multiple-quantumwell (MQW) layer and epitaxial regrowth of an InGaAsP-bulk layer on Si [11]. Using the technology, in this work, we fabricated the membrane InP-based EAM on Si waveguide circuits.…”

Assessment of Highly Performance Secure Optical Communication Systems based on Chaotic Design

“…An externally modulated LASER that runs at a wavelength of 1550 nm is modulated using NRZ pulses. The Mach-Zehnder Modulator is interferometric intensity modulator[24]. It implements a continuous wave (CW) laser.…”