Yoshiki Kuhara

Reliability of InGaAs/InP long-wavelength p-i-n photodiodes passivated with polyimide thin film

The long-term reliability of InGaAs/InP p-i-n photodiodes passivated with polyimide thin film was studied through a room temperature life test and through thermally accelerated life tests. No degradation in dark current was observed in a room temperature life test at a reverse bias of -15 V after aging for 7000 h. However, the dark current increased gradually in the accelerated life tests at 110°C, 130°C, and 150°C. It was confirmed that the activation energy of degradation in dark current was 0.85 eV and the average lifetime was estimated to be 107h at room temperature. The dark current recovered in high temperature storage tests. The phenomenon of degradation and recovery was qualitatively explained by a model of accumulation and diffusion of mobile ions at a junction perimeter.

Liquid-phase epitaxial growth of bismuth silicon oxide single-crystal film: a new optically activated optical switch.

A single-crystalline double-layered structure of a pure (80-microm)/doped (39-microm)/pure Bi(12)SiO(20) (BSO) substrate was grown for the first time by a new liquid-phase epitaxial growth to form an optical waveguide. The waveguide layer is BSO doped with CaCO(3) (0.1 wt. %) and Ga(2)O(3) (0.197 wt. %) and has a refractive index 0.07% higher than the substrate. The optical absorption coefficients were decreased by more than 1 order of magnitude by doping with the elements Ca and Ga. The high-sensitive photoconductivity of pure BSO was also reduced. Using these unique properties, we have constructed a new type of optically controlled planar optical switch.

Characterization and theoretical analysis of second-order intermodulation distortion of InGaAs/InP p-i-n photodiode modules for fiber-optic CATV

InGaAs/InP p-i-n photodiode (PD) modules for fiber-optic analog CATV have been developed. The optical configuration was optimized by making use of a spherical lens aberration. Responsivity and second-order intermodulation distortion (IMD2) were 0.95 A/W and -85 dBc at V/sub r/=12 V, P/sub in/=0 dBm, and m=40%, respectively. The improvement of IMD2 by defocusing was explained by the decrease of incident optical power density calculated by ray tracing. IMD2 was quantitatively explained through the reverse voltage dependence of responsivity which originates from the variation of the p/sup +/-InGaAs depletion layer thickness.

A coaxial-type 1.3/1.55 /spl mu/m WDM-PD module for optical access networks

A new 1.3/1.55 /spl mu/m WDM/photodiode(PD) module has been designed and fabricated for use in optical access networks. A 1.3 /spl mu/m-PD and a 1.55 /spl mu/m-PD were arranged in series along the optical axis in a coaxial package. The 1.3 /spl mu/m-PD with an In/sub 0.66/Ga/sub 0.34/As/sub 0.76/P/sub 0.24/ photosensitive layer (/spl lambda//sub g/=1.42 /spl mu/m) absorbs 1.3 /spl mu/m digital optical signals and it is transparent to 1.55 /spl mu/m wavelength. The 1.55 /spl mu/m-PD with an In/sub 0.53/Ga/sub 0.47/As photosensitive layer absorbs 1.55 /spl mu/m analog optical signals. Responsivity of the module is 0.82 A/W at 1.31 /spl mu/m wavelength and 0.75 A/W at 1.55 /spl mu/m wavelength, respectively. IMD2 of the 1.55 /spl mu/m-PD measured by two-tone method was -76.1 dBc at Pf(1.55 /spl mu/m) of -6 dBm. Bit error rate (BER) of the 1.3 /spl mu/m-PD was measured at 28.8 Mb/s by using an amplifier with bandwidth of 200 MHz and was found to be less than 10/sup -8/ at Pf(1.3 /spl mu/m) of -30 dBm.

A compact coaxial-type optical transceiver module using a half-transmittance photodiode for TCM optical access networks

A compact coaxial-type optical transceiver module has been developed without using a conventional 3 dB optical coupler. This transceiver is composed of a newly designed half-transmittance photodiode (HT-PD) and a 1.3-/spl mu/m-MQW-LD. An HT-PD is used both as a photodetector and as a window for LD light. Fiber output power of 1.15 mW at the drive current of 26 mA and responsivity of 0.48 A/W at the reverse-voltage of 5 V were obtained. Temperature dependence of responsivity is also reported.

1.25 Gbps single fiber transceivers using low cost polymer straight waveguide for 1.3/1.55 /spl mu/m data-links

1.25 Gbps single fiber transceivers have been successfully obtained by introducing a low cost polymer straight waveguide and 1.3 /spl mu/m-PD/1.55 /spl mu/m-PD, for the first time. Minimum sensitivity of -23.3 dBm was confirmed at BER=10/sup -12/ under 1.25 Gbps full-duplex operation with fiber output power of -10.5 dBm.

A DIL-type miniature optical transceiver module using an InGaAsP half-transmittance photodiode for TCM optical access networks

A compact DIL-type miniature optical transceiver module has been developed without using a conventional 3 dB optical coupler. This transceiver is composed of a newly designed InGaAsP half-transmittance photodiode (HT-PD) and a 1.3-/spl mu/m multiquantum-well laser diode (MQW-LD). An HT-PD is used both as a photodetector and as a window for laser diode (LD) light. Fiber output power of 0 dBm at the drive current of 33.8 mA and responsivity of 0.58 A/W at the reverse-voltage of 2 V were obtained. The fundamental characteristics of the HT-PD are studied and discussed.

Optical WDM transceiver module using wavelength-selective coupler and WDM-PD for optical access networks

We have proposed a new WDM-transceiver module using a wavelength-selective coupler and a 1.3 /spl mu/m InGaAs WDM p-i-n photodiode and InGaAsP MQW laser diode in order to reduce component number and module size. In this report, we confirmed the fundamental operation of this module assembled with pigtailed components. Evaluation results imply that this WDM transceiver module is promising for application to an optical WDM transceiver/receiver.

3.5-mm-square InGaAs p-i-n photodiodes and their application to optical-axis arrangement between 1.3-/spl mu/m laser diodes and a SMF

InGaAs p-i-n photodiodes (PD) with 3.5-mm/spl times/3.5-mm-large photosensitive area have been fabricated using chlorine-vapor-phase-epitaxial (C-VPE) growth. They showed high responsivity of 0.95 A/W (/spl lambda/=1.3 /spl mu/m) and 1.2 A/W (/spl lambda/=1.55 /spl mu/m) and good homogeneity in the whole area. Long-term reliability was confirmed through high-temperature aging tests at 150/spl deg/C up to 5200 hours. A PD with two pairs of parallel electrodes (PE-PD) was applied to optical-axis arrangement between 1.3-/spl mu/m laser diodes (LDs) and a single mode fibre (SMF). The beam position of a LD was detected in error within /spl plusmn/20 /spl mu/m using PE-PD prior to coupling of a LD beam into a SMF. Total inspection time was reduced to one third the original time.

Miniaturized 300Mb/s optical transmitter/receiver modules using 1.31µm LED and PIN-photodiode

Employing a well-designed 1.3µm source-detector pair of InGaAsP surface emitting LED and InGaAs PIN-photodiode, we have developed a miniaturized optical data link for 300Mb/s transmission. The transmitter and receiver were packaged compactly by the use of hybrid IC technology and newly developed Si integrated circuits. In order to make the most of fiber bandwidth, the peak emission wavelength of LED was designed to be around 1310nm, and 300Mb/s transmission experiment was achieved over 5km with a margin of 6dB.