Koichiro Adachi

25-Gb/s Multichannel 1.3-

Two multichannel 1.3-μ m lens integrated surface-emitting laser arrays for massive data links were fabricated. The basic structure of the lasers consists of a short InGaAlAs multiple-quantum-well distributed-feedback (DFB) active-stripe array monolithically integrated with both a 45° total reflection mirror and an aspheric collimation lens. One of them, a four-channel laser array based on this structure, exhibited clear 25-Gb/s eye openings up to 50°C over all four channels and achieved a total output of 100 Gb/s. The other laser, a multiple-wavelength array for wavelength-division-multiplexing applications, produces multiple-wavelength emission thanks to precisely modified DFB gratings by electron beam lithography. It exhibited nine-wavelength stable single-mode operation (side-mode suppression ratio >; 40 dB) between 1260 and 1290 nm at 3.7-nm intervals, and a clear 25-Gb/s eye opening for each wavelength. These two surface-emitting laser arrays have demonstrated their suitability for next-generation multichannel data links (including 100-Gb Ethernet and optical interconnects).

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A high-speed large-capacity optical printed circuit board (OPCB) for next-generation high-capacity routers and servers was developed. This OPCB is composed of a multilayer polymer optical waveguide, a receiver optical input/output (I/O) module (with a lens-integrated photodiode and a SiGe transimpedance amplifier), and a low-power (7.1 mW/Gb/s) transmitter optical I/O module consisting of a lens-integrated surface-emitting laser and complementary metal-oxide-semiconductor (CMOS) driver IC. A 1-Tb/s (20 Gb/s/ch × 48 ch per transmitter or receiver) large-capacity OPCB prototype was fabricated and demonstrated 20-Gb/s/ch operation.

m Surface-Emitting Lens-Integrated DFB Laser Arrays

High-speed 1.3-μm directly modulated lasers (DMLs) have been developed to support sharply rising optical communications traffic. The most crucial requirement for these lasers is the ability to operate over a wide temperature range with no power-consuming electric cooler. Due to poor temperature characteristics resulting from its poor electron confinement in the multiquantum well, DMLs with InGaAsP material systems have been replaced by DMLs with InGaAlAs material systems, which have stronger electron confinement. In this paper, progress in uncooled 25-Gb/s 1.3-μm InGaAlAs DMLs is summarized. A 160-μm-long ridge-waveguide-type laser showed a lower threshold current Ith of 14.9 mA at high temperatures up to 95 °C, and a small signal-frequency-response bandwidth f3dB of 14 GHz was achieved at a bias current of 60 mA at 95 °C. Using this laser, clear 25-Gb/s operation was obtained at 95 °C. In addition, stable operation was achieved for up to 4000 h at 85 °C, indicating the basic applicability of the device to next-generation 25-Gb/s data communication systems. Furthermore, the developed technology was applied to a novel uncooled 25-Gb/s 1.3-μm surface-emitting laser for optical interconnects, in which a 45° mirror and a lens were integrated monolithically.

20-Gb/s/ch High-Speed Low-Power 1-Tb/s Multilayer Optical Printed Circuit Board With Lens-Integrated Optical Devices and CMOS IC

The uncooled 25-Gbit/s direct modulation of a 1.3-µm horizontal-cavity surface-emitting laser was demonstrated. A fabricated laser, which is directly mountable on a high-frequency coplanar line, exhibited 25-Gbit/s eye openings up to 100°C.

Wide Temperature Range Operation of 25-Gb/s 1.3-μm InGaAlAs Directly Modulated Lasers

A 25 Gb/s laser diode (LD) driver has been developed on the basis of standard 65 nm CMOS technology for optical interconnects. The LD driver consists of a main driver capable of providing an average current of 30 mA and a predriver providing a gain of 20 dB. The main driver uses mutually coupled inductors to adjust the inductive peaking to improve eye patterns under various packaging conditions. The predriver uses CMOS active feedback to achieve a wide bandwidth and high gain, despite its small size and low power consumption. The fabricated circuit achieves data rates of 25 Gb/s, consumes 156 mW (6.3 mW/Gb/s) and occupies an area of 0.011 mm2 .

100°C, 25 Gbit/s direct modulation of 1.3 µm surface emitting laser

A prototype transceiver composed of a 1.3-μm-range lens-integrated laser diode and photodiode as well as a complementary metal-oxide-semiconductor (CMOS) laser diode driver and a CMOS transimpedance amplifier for high-speed optical interconnections was developed. It demonstrated 25-Gb/s error-free 100-m multimode fiber transmission, with power dissipation of only 9 mW/Gb/s, for the first time.

A 25 Gb/s 65-nm CMOS Low-Power Laser Diode Driver With Mutually Coupled Peaking Inductors for Optical Interconnects

A compact 25-Gbps × 4-channel optical transceiver has been fabricated for optical backplane systems. Power consumption was as low as 20 mW/Gbps. A transmission experiment was successfully conducted at 25 Gbps.

25-Gb/s 100-m MMF Transmission Using a Prototype 1.3-

As a solution to provide small-footprint and low-cost light sources for silicon platforms, light sources using a lens-integrated surface-emitting laser (LISEL), and a grating coupler fabricated on a silicon-on-insulator substrate is proposed. Light emitted from the LISEL (based on an InP distributed feedback laser) has a narrow far-field pattern, so the LISEL can be directly mounted on the silicon platform with no additional external optical components. The alignment tolerance between the LISEL and grating coupler was experimentally measured. This measurement confirmed large alignment tolerance. The excess loss due to misalignment of ±5 μm is only 1.5 dB.

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Circular, narrow beam emission of a lens-integrated surface-emitting laser operated at 1.3-µm wavelength was demonstrated. The laser consists of a distributed feedback laser cavity monolithically integrated with an etched 45° total reflection mirror and an etched InP lens. The profile of the etched InP lens was estimated to be a highly symmetrical parabolic shape that is ideal for the collimation of a Gaussian beam. A fabricated lens-integrated surface-emitting laser exhibited a circular, narrow far-field pattern with full-width at half-maximums of 3.9° × 3.5°. A highly efficient direct coupling to a single-mode fiber with a coupling efficiency of − 2.7 dB was also confirmed.

-Range CMOS-Based Transceiver for Optical Interconnections

We describe an aspheric-microlens-integrated high-performance PIN photodiode, which exhibits high speed (35 GHz), high responsivity (0.8 A/W), and large alignment tolerance (26 µm) for direct coupling to a flat-ended standard single-mode fiber.