Takashi Toyonaka

High-power highly-reliable operation of 0.98-/spl mu/m InGaAs-InGaP strain-compensated single-quantum-well lasers with tensile-strained InGaAsP barriers

We compared 0.98-/spl mu/m lasers with a strain-compensated active layer consisting of a compressive InGaAs well and tensile-strained InGaAsP barriers with identical lasers that have a conventional active layer with GaAs barriers. It was shown that the lasers with InGaAsP barriers have better temperature characteristics due to the larger energy gap difference between a well and barriers. Because of the high characteristic temperature, 200-mW operation was obtained with the InGaAsP-barrier laser even at 90/spl deg/C without any significant deterioration. We also showed that the operation of the lasers with a strain-compensated active layer was highly reliable. The degradation rate of these lasers was four times smaller than that of the lasers with GaAs barriers due to the better crystal quality in their active laser. The estimated lifetime at 25/spl deg/C for the lasers with a strain-compensated active layer was more than 170000 hours. >

Highly reliable and stable-lateral-mode operation of high-power 0.98-/spl mu/m InGaAs-InGaAsP lasers with an exponential-shaped flared stripe

A 0.98-/spl mu/m InGaAs-InGaAsP-GaAs strained quantum-well (QW) laser with an exponential-shaped flared stripe is proposed for high-power, highly reliable operation. The stripe width is wider at the front facet to reduce the optical density by widening the spot size. The stripe width is narrower at the rear facet for stable lateral-mode operation. The stripe width in the transient region is varied exponentially along the cavity for smooth mode transformation. We showed that this structure expands the spot size effectively without any deterioration in stable lateral-mode operation. The kink-occurrence output power is determined only by the stripe width at the rear facet, and the spot size at the front facet is a function only of the stripe width at the front facet. The maximum output power is 40-60% higher than that of ordinary straight-stripe lasers for the same kink-occurrence output power. Testing at 150 mW showed stable operation with an estimated lifetime of more than 200000 h at 25/spl deg/C.

10 Gbit/s avalanche photodiodes applicable to nonhermetic receiver modules

Highly reliable InAlAs-APDs have been developed for highly sensitive 10 Gbit/s receivers. Estimated lifetime is as long as 1,000,000 hours at 75/spl deg/C, and a stable operation in a dump-heat ambient (138/spl deg/C, 85%RH) was also demonstrated.

Strain-Compensation Effect on the Reduction of Lattice Distortion in InGaAs/(In)GaAs(P) Strained Quantum-well Structures on GaAs Substrates

InGaAs/InGaAsP strained quantum-well (QW) structures grown by metal-organic vapor phase epitaxy on (001) GaAs substrates were investigated using photoluminescence measurement and transmission electron microscopy. The lattice distortion in and near the QW structures caused by compressive strain in the InGaAs wells was reduced far below that of ordinary InGaAs/GaAs QW structures and the maximum number of QWs without cross-hatched patterns on the samples can be increased when tensile-strain InGaAsP barriers were introduced.

Demonstration of world-first 103 Gbit/s transmission over 40 km single mode fiber by 1310 nm LAN-WDM optical transceiver for 100GbE

4 ch × 25.8 Gbit/s WDM transmission over 40 km single mode fiber was demonstrated. Minimum receiver sensitivity each lane after 40 km transmission was less than −26.0 dBm, proving the transceiver will meet IEEE 100GBASE-ER4 specifications.

Enhanced optical crystal quality of strain-compensated InGaAs/InGaAsP quantum-well structures on GaAs substrates by the introduction of intermediate-strain layers

To improve the crystal quality of heterointerfaces in InGaAs/InGaAsP strain-compensated quantum-well structures on [001] GaAs substrates, we added layers with intermediate levels of strain between the well and barriers. Photoluminescence measurements confirmed that the crystal quality of the heterointerfaces was improved by adding these intermediate layers. The greatest improvement was attained with an intermediate layer thickness of 4 monolayers and a strain at about the midpoint between that of QWs and barriers. The mean time to failure of fabricated 0.98-/spl mu/m laser diodes (LDs) with such intermediate-strain layers was found to be about five times longer than that of LDs without the intermediate-strain layer.

1.3-μm InP-based n-type modulation-doped strained multiquantum well lasers for high-density parallel optical interconnections

The superior performance of n-type modulation doping in 1.3- micrometer InP-based strained multi quantum-well (MQW) lasers is demonstrated. Experimental results, which is in good agreement with theoretical results, confirm that the threshold current density, carrier lifetime, and internal loss in n-type modulation-doped (MD) MQW lasers is lower than those in conventional undoped MQW lasers at room and high temperatures. In addition, 2.5-Gb/s modulation under zero-bias current is achieved with the modified n-type MD-MQW laser at 85 degrees Celsius. These results confirm the suitability of this type of laser as a light source for high-density parallel optical interconnections.

Polarization-independent semiconductor optical amplifier module using twin graded-index rod lenses

Recent reductions in polarization sensitivity have again made semiconductor optical amplifiers (SOA’s) attractive for fiber-optic communications.1–3 Another key issue of SOA’s is packaging with highly efficient and stable optical coupling to single-mode fibers. There are several reports on packaged SOA modules.4,5 However, these modules showed high polarization sensitivity owing to chip characteristics. Optical coupling efficiency differ between polarization-insensitive and -sensitive devices, because the waveguide parameters are different. In this paper, we demonstrate a SOA module with polarization sensitivity as low as 1 dB at a 17-dB fiber-to-fiber gain.