Yoshitaka Ohiso

Monolithically integrated photonic switching device using an MSM PD, MESFETs, and a VCSEL

We have fabricated a photonic switching device that monolithically integrates a metal-semiconductor-metal photodetector, metal-semiconductor field-effect transistors, and a vertical-cavity surface-emitting laser. This device can perform both NOR- and OR-types of operation with thresholding input-output characteristics. The contrast ratio is more than 30 dB with optical gain. The device also shows a 3-dB bandwidth of 220 MHz and switching energy of 700 fJ at a 100-MHz frequency.<<ETX>>

Flip-chip bonded 0.85-μm bottom-emitting vertical-cavity laser array on an AlGaAs substrate

We report high-performance 0.85-/spl mu/m bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) on an AlGaAs substrate with 2.1 mA threshold current density 4.2 mW maximum output power, 11.7% power conversion efficiency and a maximum operating temperature of 130/spl deg/C. We also demonstrate a flip-chip bonded 0.85-/spl mu/m bottom-emitting VCSEL array, and confirm all pixels across the 8/spl times/8 VCSEL array operate at a f/sub 3/ dB bandwidth of 2.6 GHz at only 4.2 mA.

Long-wavelength (1.55-/spl mu/m) vertical-cavity lasers with InGaAsP/InP-GaAs/AlAs DBR's by wafer fusion

We propose a novel design for a 1.55-/spl mu/m vertical-cavity surface-emitting laser (VCSEL) structure employing double InGaAsP/InP-GaAs/AlAs distributed Bragg reflectors. The fundamental features of InP/GaAs wafer fusion are examined as a function of load pressure. We demonstrate an exact 1.55-/spl mu/m emission wavelength in the CW mode with low threshold voltage (2.1 V) and low threshold current density (1.8 kA/cm/sup 2/).

Design approaches for VCSEL’s and VCSEL-based smart pixels toward parallel optoelectronic processing systems

The technical issues involved in applying vertical-cavitysurface-emitting lasers (VCSELs) to parallel opticalinterconnection systems are discussed from the viewpoint of theirapplication to asynchronous transfer mode switching and parallelcomputer systems. We also discuss approaches to designing a VCSELarray structure for high-speed modulation and the effect ofpixel-performance homogeneity on the transmission bandwidth and powerconsumption. We review monolithic and hybrid integrationtechnologies for VCSEL-based smart-pixel arrays, and we estimate themaximum pixel number and input-output throughput allowed in a chip, considering the power consumption and pixel homogeneity. We showthat a one-chip optoelectronic parallel processing system comprisingmore than 1000 processor elements is possible when smart-pixel arraysare fabricated under the 0.25-mum complementary metal-oxide semiconductor design rule.

A widely tunable optical filter using ladder-type structure

A novel widely tunable optical filter with a ladder-type structure is proposed. The device decreases the electrode area, compared with a tunable filter using an arrayed waveguide grating filter. It is fabricated using the InGaAsP-InP material system, and current injection is employed to change the refractive index of the waveguide. The device exhibits a tuning range of 58 nm and a switching time of less than 10 ns.

Polarization-independent tunable wavelength-selective filter using a liquid crystal

The authors demonstrate a polarization-independent liquid crystal Fabry-Perot interferometer. An input light beam was split into two orthogonal polarized beams by a polarization beam splitter and prism and the polarization of one beam was rotated 90 degrees by a half-wave plate. These two beams were filtered through different points of the filter and recombined. Two transmission peaks corresponding to these beams usually appeared. However, there were some regions where the two beams were superimposed. At these regions, the filter had a tuning range of over 50 nm with a band pass of 0.4-0.5 nm and a low fiber-to-fiber loss of 3 dB. At the regions where two peaks appeared, the two peaks could be superimposed by applying different voltages.<<ETX>>

Polarization-controlled 850-nm-wavelength vertical-cavity surface-emitting lasers grown on [311]B substrates by metal-organic chemical vapor deposition

We demonstrate the polarization stability of 850-nm-wavelength vertical cavity surface-emitting lasers (VCSELs) grown on [311]B substrates under continuous-wave (CW) and dynamic operation. To clearly verify the polarization stability of VCSELs on [311]B substrates due to the anisotropic optical gain, the characteristics of both VCSELs on [311]B and [100] substrates were compared experimentally. Under CW operation, very small difference in both orthogonal polarization suppression ratio and the distribution of polarization direction was observed between VCSELs on [311]B and [100] polyimide-buried structures. On the other hand, significantly larger orthogonal polarization suppression ratio was obtained for VCSELs on [311]B substrates than those on [100] substrates under zero-bias modulation. Time-dependent orthogonal polarization suppression ratio measurements also showed that the orthogonal polarization suppression ratios of the VCSEL on [311]B substrates were more stable than those on [100] substrates. The data transmission characteristics also indicate large differences in the dependence of the bit error rate on bias current and the power penalty between polarization resolved and unresolved systems between VCSELs on [311]B and [100] substrates. The beneficial effect of the polarization stability of VCSELs on [311]B substrates due to their anisotropic optical gain is clearly demonstrated.

Investigation of dynamic polarization stability of 850-nm GaAs-based vertical-cavity surface-emitting lasers grown on [311]B and [100] substrates

The polarization stability of 850-nm GaAs-based vertical-cavity surface-emitting lasers (VCSELs) under dynamic operation was investigated by comparing the characteristics of VCSELs grown on [311]B and [100] GaAs substrates. Significantly larger suppression ratios of the two orthogonal polarization modes was obtained for VCSELs on [311]B substrates than those on [100] substrates under zero-bias modulation. Time-dependent orthogonal polarization suppression ratio measurements also showed that the polarization direction was more stable in the VCSEL on [311]B substrates than that on [100] substrates. Error-free transmission was realized from VCSELs on [311]B substrates with and without a polarizer in both back-to-back and 100-m multimode fiber transmission.

0.85-μm vertical-cavity surface-emitting laser diode arrays grown on p-type GaAs substrate

We have fabricated the first room-temperature (RT) continuous-wave (CW) 0.85-/spl mu/m 8/spl times/8 bottom-emitting vertical-cavity surface-emitting AlGaAs-GaAs DBR QW laser diode (VCSEL) arrays on a p-type GaAs substrate, which are applicable to optical interconnection. The laser characteristics are slightly inferior to those of VCSEL arrays made on n-type GaAs substrate with the same reflectivity, but exhibit for better array uniformity of threshold current density than previously reported. Such devices are applicable to N-MOS integration.

Fast tunable optical filter using cascaded Mach-Zehnder Interferometers with apodized sampled gratings

We demonstrate a novel tunable optical filter using cascaded Mach-Zehnder interferometers with apodized sampled gratings (ASGs). The ASGs are fabricated using an InGaAsP-InP deep-ridge waveguide with vertical-groove surface grating to obtain a high extinction ratio by sidelobe suppression. The proposed filter exhibits the total free-spectral range of 16 nm, an extinction ratio of 20 dB, and a 3-dB transmission bandwidth of 32 GHz.