Gain and noise characteristics of a 1.5 mu m near-travelling-wave semiconductor laser amplifier

The spectral dependence of the gain and noise characteristics of a gas source molecular beam epitaxy (GSMBE)-grown BH-GaInAsP near-travelling-wave semiconductor laser amplifier are presented, from which an indication of nonresonant internal losses is given. An intrinsic noise figure of 6 dB at an internal gain of 28 dB is obtained.<>     

Cancellation of inherent AM in semiconductor optical amplifier phase modulators

Pure optical phase modulation with a two-electrode semiconductor optical amplifier is demonstrated experimentally. The inherent amplitude modulation has been suppressed more than 50 times by modulating the two electrodes out of phase, whereas the overall phase response was reduced by only 7.5%. It has, furthermore, been found that the tolerances on the operating condition are not excessively stringent.<>     

Multi-quantum-well lasers emitting at 1.55 mu m grown by GSMBE

GaInAs/GaInAsP multi-quantum-well structures emitting at 1.55 mu m have been realised by gas source molecular beam epitaxy (GSMBE) over a large range of growth temperature. Threshold current densities as low as 0.81 kA/cm/sup 2/ have been obtained. The first BH lasers fabricated by GSMBE from these heterostructures exhibit low threshold current (18 mA) and linear DC light-current characteristics up to 20 mW.<>     

Highly sensitive 565 Mb/s DPSK heterodyne transmission experiment using direct current modulation of a DFB laser transmitter

A comparison between external phase modulation and phase modulation obtained through direct current modulation of a multiquantum-well distributed feedback (DFB) transmitter is reported for a sensitive 565 Mb/s differential-phase-shift-keying (DPSK) heterodyne transmission experiment. A limited sensitivity penalty for direct phase modulation is expected from the driving current pulse shape, the transmitter FM response and the receiver characteristics. The experimentally observed 0.5 dB penalty is in agreement with theory and highlights the potential of direct DPSK modulation as compared to both standard DPSK and continuous-phase frequency shift keying (CPFSK) schemes.<>     

Multi‐model Arlequin method for transient structural dynamics with explicit time integration

This paper addresses the explicit time integration for solving multi‐model structural dynamics by the Arlequin method. Our study focuses on the stability of the central difference scheme in the Arlequin framework. Although the Arlequin coupling matrices can introduce a weak instability, the time integrator remains stable as long as the initial kinematic conditions of both models agree on the coupling zone. After showing that the Arlequin weights have an adverse impact on the critical time step, we present two approaches to circumvent this issue. Computational tests confirm that the two approaches effectively preserve a feasible critical time step and show the efficiency of the Arlequin method for structural explicit dynamic simulations. Copyright © 2017 John Wiley & Sons, Ltd.     

Low-threshold 1.5 mu m DFB laser grown by GSMBE

GaInAsP 1.5 mu m DFB lasers with a low threshold current (17 mA) have been grown by gas source molecular beam epitaxy (GSMBE) in a two-step epitaxial process. The lasers exhibit single-mode emission for emitted power in excess of 10 mW with side mode suppression ratio of 40 dB and spectral linewidth of 15 MHz. In addition the dispersion of the lasing wavelength has been found to be as low as 1.7 nm.<>     

Two-section semiconductor optical amplifier used as an efficientchannel dropping node

High responsivity in a two-section semiconductor optical amplifier/detector, serving as a channel dropping mode is described. A simple receiver constructed using a 50 Ω amplifier with a sensitivity of -30.2 dBm at 140 Mb/s is demonstrated     

Gain, polarisation sensitivity and saturation power of 1.5 ?m near-travelling-wave semiconductor laser amplifier

Gain, saturation and polarisation characteristics of a near-travelling-wave 1.5,?m BH semiconductor laser amplifier are reported. An internal cavity peak TE gain of 26.8 ± 0.5 dB with a gain ripple of 2.9 ± 0.1 dB, and TE saturation output power of 3.5±1.5dB at 22.2±0.5dB small-signal gain have been achieved.     

Design and realisation of high-gain 1.5 ?m semiconductor TW optical amplifiers

The influence of the waveguide parameters, leakage current, electrical and thermal resistances on the maximum linear gain and the corresponding tuning wavelength of buried-heterostructure (BH) semiconductor travelling-wave optical amplifiers (TWAs) operating around 1.5 ?m is theoretically analysed. A 26 dB gain TWA has been designed and fabricated from a 400 ?m-long BH laser with a 0.2 ?m-thick active layer by using low-reflectivity SiO (R ? 6 × 10?4) coatings.     

Simple determination of coupling coefficient in DFB waveguidestructures

A simple method allowing the determination of the coupling coefficient K_q of DFB waveguide structures of arbitrary type, number of layers and grating profile is proposed. The method relies on effective index determination and the fast Fourier transform of the actual grating profile. The method has been validated by comparison with the measured stopband width of liquid phase epitaxy (LPE) and gas source molecular beam epitaxy (GSMBE) grown 1.5 μm DFB lasers