Yuki Wakayama

Direct Modulation at 56 and 50 Gb/s of 1.3-

Direct modulation at 56 and 50 Gb/s of 1.3-μm InGaAlAs ridge-shaped-buried heterostructure (RS-BH) asymmetric corrugation-pitch-modulation (ACPM) distributed feedback lasers is experimentally demonstrated. The fabricated lasers have a low threshold current (5.6 mA at 85°C), high temperature characteristics (71 K), high slope relaxation frequency (3.2 GHz/mA1/2 at 85°C), and wide bandwidth (22.1 GHz at 85°C). These superior properties enable the lasers to run at 56 Gb/s and 55°C and 50 Gb/s at up to 80°C for backto-back operation with clear eye openings. This is achieved by the combination of a low-leakage RS-BH and an ACPM grating. Moreover, successful transmission of 56and 50-Gb/s modulated signals over a 10-km standard single-mode fiber is achieved. These results confirm the suitability of this type of laser for use as a cost-effective light source in 400 GbE and OTU5 applications.

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The use of InP-based IQ modulator for ultra-high speed precise 28-GBaud 64QAM signal generation (336 Gbit/s with polarization multiplexing) is experimentally demonstrated using digital modulator non-linearity compensation techniques, for the first time to our knowledge.

m InGaAlAs Ridge-Shaped-BH DFB Lasers

Low-cost optical assemblies for optical interconnections using lens-integrated surface-emitting laser are proposed. High coupling efficiency with single-mode-fibers of over -1.9dB and RIN below -140dB/Hz with large back reflection and 85°C/85% storage test are demonstrated.

High-speed optical 64QAM signal generation using InP-based semiconductor IQ modulator

Direct modulation at 50 Gb/s of 1.3-μm InGaAlAs DFB lasers operating at up to 80°C was experimentally demonstrated by using a ridge-shaped buried heterostructure.

Capability of high optical-feedback tolerance and non-hermetic-packaging for low-cost interconnections using lens-integrated surface-emitting laser

For a multi mode fiber optical link, a high speed silicon photonics receiver based on a highly alignment tolerant vertically illuminated germanium photodiode was developed. The germanium photodiode has 20 GHz bandwidth and responsivity of 0.5 A/W with highly alignment tolerance for passive optical assembly. The receiver achieves 25 Gbps error free operation after 100 m multi mode fiber transmission.

80°C, 50-Gb/s Directly Modulated InGaAlAs BH-DFB Lasers

Germanium (Ge) (111) fins of 320 nm in height were successfully fabricated using a combination of flattening sidewalls of a silicon (Si) fin structure by anisotropic wet etching with tetramethylammonium hydroxide, formation of thin Ge fins by selective Si oxidation in SiGe layers, and enlargement of Ge fins by Ge homogeneous epitaxial growth. The excellent electrical characteristics of Ge(111) fin light-emitting diodes, such as an ideality factor of 1.1 and low dark current density of 7.1 × 10−5 A cm−2 at reverse bias of −2 V, indicate their good crystalline quality. A tensile strain of 0.2% in the Ge fins, which originated from the mismatch of the thermal expansion coefficients between Ge and the covering SiO2 layers, was expected from the room-temperature photoluminescence spectra, and room-temperature electroluminescence corresponding to the direct band-gap transition was observed from the Ge fins.

25 Gbps silicon photonics multi-mode fiber link with highly alignment tolerant vertically illuminated germanium photodiode

We demonstrated 1310-nm 25-Gbps error-free transmission over both 2-km single-mode fibre and 100-m OM3 multi-mode fiber using the same silicon photonics transmitter and a high-sensitivity CMOS receiver with a lens-integrated photodiode.