Yoshihiko Hanamaki

dBm average optical output power operation of small-chirp 40-gbps electroabsorption Modulator with tensile-strained asymmetric quantum-well absorption Layer

A small-chirp 40-Gbps electroabsorption modulator (EAM) with high optical output power capability has been developed for the first time. An optimized tensile-strained asymmetric quantum-well structure is employed as the absorption layer of the EAM so that small chirp and reduction of the lifetime of the photogenerated holes for high optical output power tolerance is obtained. Deteriorations of frequency response and chirp due to carrier pileup under high optical output power conditions were prevented by enhancing carrier sweepout, which was experimentally confirmed as a hole lifetime as short as 35 ps under high optical output power conditions. As a result, good frequency response (bandwidth > 30 GHz) and small chirp (/spl alpha/<1) were obtained under the condition of the zero bias voltage and +4.5 dBm continuous-wave (CW) optical output power (P/sub out,CW/). Clear eye opening and high dynamic extinction ratio under 40-Gbps non-return-to-zero modulation persisted to a high average output power (P/sub out,ave/) condition of P/sub out,ave/=+1.0 dBm.

1.3 /spl mu/m uncooled AlGaInAs-MQW DFB laser with /spl lambda//4-shifted grating

1.3 /spl mu/m uncooled AlGaInAs DFB-LDs with /spl lambda//4shifted grating have been successfully demonstrated. Relaxation oscillation frequency as high as 11.5 GHz has been obtained. Clear opening in the eye diagram under 10 Gbps direct modulation at 75/spl deg/C has been also confirmed. Preliminary life test over 5000 hours with no failure indicates its excellent reliability. The 1.3 /spl mu/m AlGaInAs DFB-LD with /spl lambda//4-shift grating is promising for the next generation high-speed data link systems such as 10 Gbps Ethernet.

1.3 /spl mu/m AlGaInAs ridge waveguide lasers with uncooled 10 Gb/s operation at 85/spl deg/C

We have realized 1.3 /spl mu/m MQW AlGaInAs lasers with 10 Gb/s operation even at high temperature of 85 C. This performance is well suitable for the uncooled high-speed transmission in optical communication systems, especially for gigabit ethernet application.

High-Power Tapered Unstable-Resonator Laser Diode With a Fiber-Bragg-Grating Reflector

We designed a tapered unstable-resonator laser diode consisting of a 3-mm-long tapered amplifier and a fiber-Bragg-grating reflector, both of which were coupled with a biconical microlens at the fiber end. The amplifier was composed of an InGaAs single quantum well inside a waveguide, which had an optical confinement factor of 1.2%, a tapered current constriction of 6deg in full angle, and an input width of 10 mum. The grating reflector was fabricated in a polarization-maintaining fiber with a reflectivity of 99% and a reflection bandwidth of 0.19 nm. A biconical microlens with vertical and horizontal radii of 3.5 and 11 mum, respectively, was fabricated at the fiber end to increase the coupling efficiency between the tapered amplifier and the grating reflector. An output power of 3.2 W was obtained at a wavelength of 1064 nm in multimode operation for the grating reflection bandwidth.

High-Power 1.06-

We designed a 1.06-mum single-quantum-well (SQW) InGaAs/AlGaAs planar tapered amplifier that was injected with seed light of a fiber Bragg grating stabilized laser diode through a fiber biconical microlens. To increase the amplifier output, the microlens with approximately 3- and 11-mum radii on vertical and horizontal axes, respectively, provides high coupling efficiency between the laser diode and the amplifier. The microlens also controls propagation in the tapered gain area to suppress the filament formation. In addition, the small radii of the microlens reduce near-end reflection at the amplifier input to prevent parasitic laser oscillation of the amplifier. We demonstrated near-diffraction-limited output of 5.5 W with the beam quality factor M2 of 1.5 by using a 3-mm-long amplifier having an optical confinement factor of 1.2%.

\mu{\hbox {m}}

A very low failure rate of a 0.98 /spl mu/m laser diode is reported. COD free characteristics is realized. The cumulative failure rate 0.4% for wear-out and 5.6% for sudden failure is estimated 25 years later at 25 C-250 mW.

Near-Diffraction-Limited Planar Tapered Amplifier Injected With Seed Light Through a Fiber Biconical Microlens

Wave-guide photodiodes with 50 GHz bandwidth at the low operation bias voltage of -1.5 V are realized, which have life time over 8/spl times/10/sup 7/ h at 25 /sup /spl deg//C by adopting buried structure with semiinsulating InP.

A very low failure rate of COD free high power 0.98 /spl mu/m laser diode with the window structure

We have realized highly reliable 1.3 μ m AlGaInAs FP lasers with low power penalty of 1.4dB at 10Gbps and 85°C. The MTTF was estimated over 1.5×105 hours and no deterioration of COD level was observed during the life test.

Highly reliable wave-guide photodiode with wide bandwidth of 50 GHz at the low operation voltage of -1.5 V

The well-balanced twin photodiodes with over 45 GHz bandwidth on one chip have been developed. It is realized by removing Si pile-up region due to contamination, which connects waveguide region and bonding pad electrically

Highly reliable 1.3 μm AlGaInAs FP lasers with low power penalty under uncooled 10Gbps operation at 85°C

We have investigated a real-time reflectance spectroscopy during AlGaInP growth by metalorganic vapor phase epitaxy. The analysis of Fabry-Perot oscillation gives the optical parameters of epitaxial layer such as refractive index (n) and extinction coefficient (k). By using the relationship between these optical parameters and the composition of AlGaInP, in-situ monitoring of growth rate (R/sub g/) and Al content x in (Al/sub x/Ga1-x)/sub 0.51/In/sub 0.49/P is realized without any dependence on the structure. R/sub g/ and Al content x estimated by using this in-situ monitoring method are in good agreement with those obtained by conventional measurement such as thickness, XRD and PL spectroscopy.