Distributed feedback laser emitting at 1.3 µm for gigabit communication systems

A distributed feedback (DFB) laser emitting at 1.3 μm for gigabit lightwave communication systems has been developed. The distributed feedback structure has been introduced in a newly developed buried heterostructure and designs for stable single-mode operation, high speed modulation, and low noise have been done. Threshold current of 10-15 mA, differential efficiency of around 0.28 mW/mA, low noise, small signal modulation bandwidth of 13.9 GHz, and satisfactory modulation waveform at 5-Gbit/s NRZ modulation have been attained with high single-mode operation yield.     

Steam reforming of dimethyl ether promoted by surface protonics in an electric field

The catalytic steam reforming of dimethyl ether (DME) in an electric field was carried out and the effects of proton hopping induced by the electric field on a Pd-supported CeO₂ catalyst surface were investigated. The hydrolysis of DME was promoted even on Pd/CeO₂ catalyst by the application of the electric field at low temperatures (in the range of 423–623 K), while the direct decomposition of DME was suppressed. The apparent activation energy in this temperature range was much lower with (17.2 kJ mol^?1) than without (79.0 kJ mol^?1) the electric field. Kinetic analyses demonstrated that the effect of the reactant partial pressures was also markedly different with and without the electric field. The effect of the partial pressure of water and electrochemical impedance spectra strongly suggest that surface proton hopping promotes the steam reforming of DME in an electric field at low temperatures.     

Ultra-High speed InGaAsP/InP DFB lasers emitting at 1.3 µm wavelength

A bandwidth of 13 GHz has been attained in a 1.3 μm DFB laser at 25 °C. A mesa structure was introduced to reduce the parasitic capacitance and the lasing wavelength was detuned from the gain peak to increase the differential gain. This bandwidth is the widest so far reported in 1.3 μm DFB lasers.     

Single-longitudinal-mode operation of DFB lasers in gain-switchedoperating conditions

Single-longitudinal-mode operation under a gain-switched condition, generating 20 ps optical pulses, has been attained in DFB lasers emitting at 1.3 μm wavelength. It has been clarified that Δλ, which is the difference between the DFB wavelength and the gain peak wavelength, plays an important role in stable single-mode operation. The optimum range of Δλ wave found to be in the range from -15 nm to 0 nm     

Analysis of the parasitic effective capacitance of buried-heterostructure lasers

The impedance of a BH-type laser has been evaluated up to 4 GHz. The capacitance decreases drastically with increasing frequency, and hence the cutoff frequency is higher than that predicted by the capacitance measured at several megahertz.     

High-power, wide-bandwidth, 1.55 ?m-wavelength GaInAsP/InP distributed feedback laser

A high output power of 52 mW and wide bandwidth of 9.8 GHz have been achieved in a 1.55 ?m-wavelength distributed feedback laser with a flat-surface buried heterostructure by optimising the coupling coefficient and reducing the parasitic capacitance.