Toshihito Suzuki

Reliability study of 1060nm 25Gbps VCSEL in terms of high speed modulation

Furukawas 1060nm VCSELs with double-intra-cavity structure and Al-free InGaAs/GaAs QWs enable us to realize low power consumption, high speed operation and high reliability simultaneously. The power dissipation was as low as 140fJ/bit. Clear eye opening up to 20Gbps was achieved. Random failure rate and wear-out lifetime were evaluated as 30FIT/channel and 300 years. For higher speed operation, thickness of oxidation layer was increased for lower parasitic capacitance of device. Preliminary reliability test was performed on those devices. In high speed operation faster than 10Gbps, conventional lifetime definition as 2dB down of output power is not sufficient due to smaller margin of modulation characteristics. We suggest threshold current as a barometer for degradation of modulation characteristics. The threshold currents of our VCSELs degrade small enough during accelerated aging test. We also observed no remarkable change in 25Gbps eye diagram after aging test. The definition of life time for high speed VCSEL is discussed from the change in threshold current and so on in addition to the conventional power degradation during aging. It is experimentally verified that our VCSELs are promising candidate for highly reliable light source including long term stable high speed operation.

VCSEL-based parallel-optical modules for >100 Gb/s applications

We introduce solder reflow-capable high-density parallel-optical modules for >100 Gb/s optical interconnects. Polymer-waveguide-coupled parallel-optical modules are also introduced with a unique mounting technology. 1060-nm 28-Gb/s InGaAs/GaAs VCSEL realizes a good signal quality at high temperature and error free for MMF transmission beyond 500m.

Enabling VCSEL technology for “Green” optical interconnect in HPC and Data Centers

State of the art VCSEL technology will be reviewed in terms of power consumption and reliability in order to realize the energy efficient HPC and Data Centers. Longer wavelength VCSEL seems promising candidate for the upcoming higher performance computes with energy saving.

1060nm 28-Gbps VCSEL developed at Furukawa

This paper presents recent development results of our 28-Gbps VCSELs featured with double intra-cavity structure and a lasing wavelength of 1060 nm. The double intra-cavity realizes very low cavity loss due to undoped semiconductor bottom DBR and dielectric top DBR layers. Compressively strained InGaAs MQW provides high differential gain that contributes to low power consumption and high reliability. Based on our 10-Gbps VCSEL structure, we carefully optimized MQW, selective oxide structure, cavity length, and doping profile in order to achieve high speed operation while maintaining high reliability and other laser performances. The developed VCSELs exhibit modulation 3 dB-bandwidth exceeding 20 GHz and D-factor of 10 GHz/(mA)1/2. Typical threshold current and slope efficiency are 0.5 mA and 0.5 W/A, respectively. The paper also discusses static and dynamic characteristics of VCSELs with various oxide aperture sizes simultaneously fabricated on the same wafer. For a longer transmission distance and better optical coupling to a multimode fiber, optical lateral confinement is precisely controlled to reduce spectral width as well as far-field pattern. Clearly opened eye diagrams are obtained at a bit rate of 28 Gbps. Bit error rate tests are also performed and 28 Gbps error free transmission has been confirmed over 300 meters of multimode-fiber optimized for 1060 nm with a PRBS pattern length of 231-1.

1060nm VCSEL development at Furukawa for parallel optical interconnect

This paper reviews research and development of 1060nm VCSELs at Furukawa Electric. We pursue the simultaneous realization of three strong demands for low power consumption, high reliability, and high speed. For this purpose, we have chosen compressively strained InGaAs/GaAs active layers emitting in a 1060 nm wavelength range because of their advantages of lower threshold voltage, smaller defect propagation velocity, and larger material differential gain, compared to those of GaAs/AlGaAs active layers widely used in 850 nm VCSELs. Oxide-confined and double intracavity structures provide low and stable electrical resistance as well as low optical loss. The developed VCSELs exhibited low threshold currents of 0.31 mA at 25 °C and 0.56 mA at 90 °C, together with highly uniform slope efficiency distributions throughout a wafer. We also demonstrated 10 Gbps error free transmission at a very low bias current of 1.4 mA, yielding low power dissipation operation of 0.14 mW/Gbps. Clear eye openings up to 20 Gbps were confirmed at a low bias current of 3mA. A series of endurance tests and accelerated aging tests on nearly 5000 VCSELs have proved Telcordia qualified high reliability and a very low failure rate of 30 FIT/channel at an operating temperature of 40 °C and a bias current of 6mA, with a 90% confidential level.