Misuzu Sagawa

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. >

Multistep formation and lateral variation in the In composition in InGaAs layers grown by metalorganic vapor phase epitaxy on (001) vicinal GaAs substrates

Abstract In this paper, we investigate the substrate misorientation effect on In 0.2 Ga 0.8 As/GaAs strained quantum wells grown on vicinal GaAs substrates by metalorganic vapor phase epitaxy (MOVPE). Using cross-sectional transmission electron microscopy (TEM), stepbunching in an InGaAs layer is observed. In addition, based on energy-dispersive X-ray (EDX) analysis, we report for the first time lateral variations in the In composition in an InGaAs layer grown on a vicinal substrate. It is found that this variation in In composition and variations in the thickness cause photoluminescence (PL) spectrum broadening. The dependence of PL properties on the growth conditions and on surface misorientation direction is also examined. Experimentals results are explained by discussing the diffusion length of Group III atoms and their tendency to attach to step sites. TEM analysis confirms that the critical layer thickness of an InGaAs layer decreases on a vicinal substrate due to the formation of stepbunches.

High-power and highly reliable operation of Al-Free InGaAs-InGaAsP 0.98-/spl mu/m lasers with a window structure fabricated by Si ion implantation

We have fabricated Al-free InGaAs-InGaAsP-GaAs strained quantum-well 0.98-/spl mu/m lasers with a window structure. The window structure was obtained by Si ion-implantation-induced QW intermixing. The photoluminescence and photocurrent measurements show that an implantation energy of 100 keV and a dose of 1E13 cm/sup -2/ are enough for the fabrication of the window structure in our laser structure. The threshold current of the fabricated 0.98-/spl mu/m lasers with a window structure is 20 mA and a stable lateral mode is obtained up to 300 mW, and these results suggest that there is no scattering loss or absorption due to the introduction of a window structure. The reliability of the lasers is greatly improved by the introduction of the window structure: they exhibited stable operation for more than 1000 h at 240-mW output power at 50/spl deg/C. And this results gives us an estimated lifetime of more than 200 000 h at 25/spl deg/C.

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.

Highly reliable operation of high-power 0.98-/spl mu/m InGaAs/InGaAsP lasers with a window structure fabricated by Si implantation

We have developed 0.98-/spl mu/m InGaAs-InGaAsP lasers with a window structure fabricated by Si implantation. During testing at 240 mW, lasers showed stable operation with an estimated lifetime of more than 200,000 hours at 25/spl deg/C.

Optical net gain measurement in n-type doped germanium waveguides under optical pumping for silicon monolithic laser

Silicon (Si) monolithic lasers are key devices in large-scale, high-density photonic integrated circuits. Germanium (Ge) is promising as an active layer due to the complementary metal-oxide semiconductor process compatibility with Si. A net optical gain from Ge is essential to demonstrate lasing operation. We fabricated Ge waveguides and investigated the n-type doping effect on the net optical gain. The estimated net gain of the n-Ge waveguide increased from -2200 to -500/cm, namely reducing loss, under optically pumped condition.

40-Gbit/s Operation of Ultracompact Photodetector-Integrated Dispersion Compensator Based on One-Dimensional Photonic Crystals

Utilizing large optical group-velocity dependence on wavelength without polarization-mode dependence, we have developed an ultracompact dispersion compensator based on multiple one-dimensional coupled-defect-type photonic crystals. The photonic crystal of the compensator, designed for a 1.55-µm optical communication system, consists of a multilayer thin-film structure and defect layers. The thin-film structure is substrate-free, which enables the compensator to be small, that is, a 1.4-mm-edge cube. To obtain a large group-velocity difference, 60 substrate-free films were stacked to form the compensator. The passband of the compensator is 2 nm, and the group-delay time difference within the band is more than 100 ps. A dispersion-compensator module integrated with a photodetector was fabricated. A 40-Gbit/s non-return-to-zero optical-transmission experiment was carried out with the compensator, demonstrating dispersion-compensation operation over a 10-km standard single-mode fiber, the dispersion of which corresponds to 170 ps/nm.

High-power high-temperature operation of 0.98-/spl mu/m S-SQW lasers with InGaAsP (Eg: 1.61 eV) barriers

In this paper, we systematically investigate the advantage of InGaAsP (Eg: 1.61 eV) barriers, which have the bandgap difference of 345 meV, against temperature characteristics, and compare them with conventional GaAs barriers. The excellent temperature characteristics of the laser with InGaAsP barriers results in high power operation at high temperatures.

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

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.

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.