Koji Hiraiwa

Recorded low power dissipation of 0.14 mW/Gbps in 1060 nm VCSELs for “Green” optical interconnection

Extremely low power dissipation of 0.14 mW/Gbps at 10 Gbps operation with as small as 75 mVp-p of modulation amplitude has been achieved in carefully designed InGaAs/GaAs-MQW 1060 nm VCSELs employed double intra-cavity structure.

Experimental demonstration of low jitter performance and high reliable 1060nm VCSEL arrays for 10Gbpsx12ch optical interconnection

No systematic studies on 1060nm high speed VCSELs have been reported in terms with reliability so far to our best knowledge. In this work, a systematic and intensive study on reliability has been performed for our 1060nm VCSELs consist of double intra-cavity and oxide confined structure with >70ps eye opening margin in Ib=3mA. Estimated power dissipation per bit rate of >5Gbps/mW at Ib=2mA was obtained from low series resistance and low drive voltage characteristics due to effective current injection in our double intra-cavity structure. Aging tests for 3,467pcs discrete non-hermetic VCSELs were performed under 6mA, 70°C to 120°C and up to 5,736 hours, which is equivalent to over 10million device hours in normal operating condition of 40°C and Ib=5mA. We found one degraded device due to the disconnection of the metal interconnecting layer, resulting in 81Fits (C.L.=90%) under Ea=0.35eV and no current accelerated factor. Also, their degradation of threshold current after 1,000 hours operation was less than 0.1mA under high stress condition of >40kA/cm2 and 120°C, which corresponds to more than hundreds year operation. No eye diagram degradation was observed as far as no large threshold current increase under the high stress condition up to 40kA/cm2. It is experimentally proven that inherent potentiality of the VCSELs with 1060nm InGaAs-QW and double intra-cavity structure would be applicable to the future large green data traffic system.

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.

Low dark current AlGaInAsInP waveguide photodiodes using hybrid MBE and MOCVD growth

Abstract Dark current of 7pA with one cleaved facet and 20pA with an anti-reflection coating at the reverse bias voltage of 3 V was obtained for AlGaInAs InP pin waveguide photodiodes, in which an AlGaInAs absorption layer and optical confinement layers were grown by optimized molecular beam epitaxy and an upper InP cladding layer was grown by metal-organic chemical vapor deposition. This is the lowest known dark current reported for long-wavelength pin waveguide photodiodes to date.

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.

High performance “Green” VCSELs for data centers

VCSEL performance will be reviewed. A careful design of cavity structure, as well as precise control in the epitaxial growth enables us to achieve a record power conversion efficiency of 62% in the 1060nm VCSELs.

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.

Low power consumption and highly reliable 1060 nm VCSELs for parallel optical interconnection

1060nm VCSELs with InGaAs/GaAs strained quantum wells have been reviewed in terms of power consumption and reliability. Clear eye opening was confirmed at 10Gbps with bias current of as low as 1.4mA.

High efficiency 1060nm VCSELS for low power consumption

High efficiency VCSELs will be reviewed in terms of power conversion efficiency. Other lasing parameters will be also discussed.

High Uniform Waveguide Photodiodes Fabricated on a 2-inch InP Wafer with Low Darkcurrent and High Responsivity

We have fabricated waveguide photodiodes with high uniform characteristics on a 2-inch InP wafer introducing a novel process. The 2-inch wafer fabrication procedure was carried out successfully by utilizing SiNx deposition on the back of the wafer in order to compensate wafer warp. Almost all the measured waveguide photodiodes exhibited low darkcurrent (average 419 pA, σ= 49 pA at 10 V reverse bias voltage) throughout the 2-inch wafer, and high responsivity of 0.987 A/W (σ=0.011 A/W) was obtained in a consecutive 60-channel array at the input wavelength of 1.3 µm. In addition, uniformity of frequency response was also confirmed.