Hiroshi Hatakeyama

Demultiplexing of 168-Gb/s data pulses with a hybrid-integrated symmetric Mach-Zehnder all-optical switch

We have developed a hybrid-integrated symmetric Mach-Zehnder all-optical switch and evaluated the demultiplexing of 168-Gb/s data pulses at a repetition rate of 10 GHz with this switch. A compact, stable device was realized by assembling semiconductor optical amplifiers as nonlinear waveguides on a planar lightwave circuit in a self-aligned manner. A 6.0-ps switching window needed for 168-Gb/s demultiplexing was provided by the push-pull operation of the symmetric Mach-Zehnder all-optical switch. Demultiplexed signal light showed a high extinction ratio of better than 18 dB. Error-free demultiplexing with a bit error rate of 10/sup -11/ was achieved.

Multiple-chip precise self-aligned assembly for hybrid integrated optical modules using Au-Sn solder bumps

We have developed a novel three-dimensional high precision self-aligned assembly using stripe-type Au-Sn solder bumps and a micro-press solder bump formation method. This produces a high bonding precision of 1 /spl mu/m for optical device assembly in both lateral and vertical directions without the need for time-consuming optical axes alignment. Furthermore, we tested a hybrid integrated 4/spl times/4 optical matrix switch, in which multiple SSC-SOAG arrays were simultaneously positioned and optical fibers were passively positioned on a silica based PLC platform using this technology. Four optical chips and seven wiring chips are assembled on a planar lightwave circuit (PLC) platform. The insertion loss for each of these paths at an injection current of 40 mA was within a range of 9/spl plusmn/4 dB. The average extinction ratio was 40 dB. This self-aligned assembly technology was shown to be useful for building hybrid-integrated multichannel optical network components.

High-speed 1.1-μm-range InGaAs VCSELs

We have developed 1.1-μm-range high-speed VCSELs based on InGaAs-QWs for high-speed and highly reliable optical interconnections. 3-dB bandwidth up to 20 GHz and error-free 30-Gbps 100 m operations were demonstrated with oxide confined VCSELs. We also developed buried tunnel junction VCSELs to further improve the relaxation oscillation frequency limit. 3-dB bandwidth up to 24 GHz and error-free 40-Gbps operations were demonstrated with these VCSELs.

Wavelength-selectable microarray light sources for S-, C-, and L-band WDM systems

We report on the first demonstrated near-complete coverage of the S-, C-, and L-bands using six different ranges of wavelength-selectable microarray light sources (WSLs) based on a distributed-feedback (DFB) laser diode (LD) array. The six devices were fabricated on only two wafers. Each device has a tuning range of more than 15 nm, a sidemode suppression ratio of over 40 dB, and a fiber-coupled power greater than around 10 mW.

Highly Reliable High-Speed 1.1-

In this paper, we describe high-speed 1.1-μm-range oxide-confined vertical-cavity surface-emitting lasers (VCSELs) for large-scale optical interconnection applications. For achieving high data rates up to 25 Gbit/s under high temperature, we applied InGaAs/GaAsP strain-compensated multiple quantum wells (SC-MQWs) as the active layer. The developed device showed 25 Gbit/s error-free operation at 100°C. We also examined reliability of the VCSELs through accelerated life tests. The result showed an extremely long lifetime of about 10 thousand hours in MTTF under an ambient temperature of 150°C and a current density of about 19 kA/cm2. The level of reliability either equaled or surpassed that of conventional 0.85-μm VCSELs. Moreover, we revealed a typical failure mode of the device, which was caused by ≪110≫ dark line defects (DLDs) generated in the n-DBR layers under the current aperture area.

\mu

The extinction ratio of an optical gate with a spot-size-converter-integrated semiconductor optical amplifier (SSC-SOA) is deteriorated following the direct coupling of unguided light between the input and output fibers. In this letter, an S-bend waveguide structure is introduced into an active waveguide to suppress such direct coupling. Angled facet structures are also introduced for obtaining low facet reflectivity. The fabricated SSC-SOA operating at 1.55-/spl mu/m wavelength achieves an extinction ratio up to 70 dB and a fiber-to-fiber gain of 20 dB.

m-Range VCSELs With InGaAs/GaAsP-MQWs

In this work, 1.1-mum-range VCSELs based on InGaAs/GaAs quantum wells with high modulation bandwidth up to 20 GHz were developed. Error-free 25-Gbps operations were achieved for the first time using directly modulated multimode VCSELs

Angled-facet S-bend semiconductor optical amplifiers for high-gain and large-extinction ratio

We have developed vertical-cavity surface-emitting lasers for optical interconnections operating at 1.07 mum. The active layers of the devices are InGaAs-GaAs multiple quantum-wells, which are suitable for high-speed operation and high reliability. The devices exhibit -3-dB modulation bandwidths up to 19 GHz and no degradation under 70degC, 1000-h automatic power control tests. Error-free 20-Gb/s operations were also achieved

25-Gbps operation of 1.1-/spl mu/m-range InGaAs VCSELs for high-speed optical interconnections

We propose tunnel junctions with type-II heterostructures to reduce the electrical resistance of vertical-cavity surface-emitting lasers. We fabricated the type-II tunnel junctions on GaAs substrates, which consist of highly C-doped GaAsSb on the p side and highly Si-doped InGaAs on the n side. We achieved an extremely low specific resistance of 4×10−6Ωcm2, which corresponded to a resistance of 20Ω for an aperture 5μm in diameter. The specific resistance of the type-II tunnel junction was about 40% smaller than that of the type-I tunnel junction.

1.1-/spl mu/m-range InGaAs VCSELs for high-speed optical interconnections

A wide-band wavelength-selectable light source module having an integrated multiwavelength locker has been developed. An eight-distributed-feedback (DFB) arrayed monolithic light source was designed to have 40-nm tunable range in the L-band by covering 5 nm per DFB laser diode. A uniquely designed etalon-based wavelength locker achieved very stable operation and uniform locking performance for all channels. Wavelength variation in the short term at room temperature was much less than 1 pm and the locked wavelength stayed within +/-5 pm when the case temperature of the module was varied from -20/spl deg/C to 65/spl deg/C.