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A resonant-tunnelling optical bistable laser is fabricated by monolithically integrating an InGaAs/InAlAs MQW laser diode and an InGaAs/AlAsSb resonant-tunnelling phototransistor. Inverter type light-input/light-output optical bistable operation is achieved with this bistable laser.

The first results of a field trial held in November 2000, of 1 Tbit/s unidirectional WDM transmission based on a 43 Gbit/s/channel optical transport network interface prototype, are presented. Error-free operation of 25 channels with 100 GHz spacing over a 91 km standard singlemode fibre with forward error correction is verified.

The authors propose a new method, based on the microdefocusing method, for trancutaneously measuring the velocity of leaky surface skimming compressional waves (LSSCWs) propagating on the surface of bone. The method is realised by an ultrasonic measurement system which is applicable to in vivo measurement using ultrasound of 1 MHz. The velocity of the LSSCW propagating on the surface of a Bakelite sample is successfully determined in a preliminary experiment, and the principle of the proposed method is confirmed.

A 20 GHz optical pulse train was generated by a sinusoidally-driven InGaAs/InAlAs multiquantum well intensity modulator operating at low voltages (from –2 to –3 V DC bias with a 3.2 V peak-to-peak RF signal). An approximately transform-limited optical pulse train width of 8ps and a spectral width of 40 GHz were obtained.

InAIAs/InGaAs heterojunction bipolar transistors with thin base and collector layers are fabricated. The maximum value of current gain cutoff frequency is as high as 96 GHz. It is shown that thinning of the base and collector is very effective not only for reducing the base and collector transit times but also for suppressing the space charge effect in the collector.

A new high-speed, waveguided InP-based AlGaInAs/AlInAs multiple quantum well pin photodiode, fabricated by molecular beam epitaxy, is reported. Detectors can be tuned over a range of wavelengths (over 160nm) using enhanced electroabsorption due to the quantum-confined Stark effect. A response rise time of 40ps is measured by the subpicosecond impulse response.

Quaternary AlGaInAs quantum-well optical modulators operating at 1.55 mu m are introduced and demonstrated for the first time. An electron-to-heavy-hole exciton absorption peak shift of over 600 AA is observed for a bias voltage of 6 V. An extinction ratio of 19 dB and high-speed operation over 4 GHz is obtained for this optical modulator. >