Toshi Makino

Enhanced wavelength tuning range in two-section complex-coupled DFB lasers by alternating gain and loss coupling

A novel tunable two-section complex-coupled distributed feedback (DFB) lasers were demonstrated which exhibited an enhanced wavelength tuning range beyond 7 nm by current injection only. By a simple master-and-slave type of injection current control, either in-phase gain-coupling or antiphase loss-coupling mechanism can be activated, in such a way that one of the two Bragg modes around DFB stopband will become the lasing mode, and its wavelength can be simply and independently tuned by corresponding injection current. More then 45 dB side-mode suppression ratio (SMSR) over entire tuning range were obtained. Good system performance for 375 km transmission with butt-coupled III-V Mach-Zehnder (MZ) modulator at 2.5 Gb/s over nondispersion-shifted fiber was also demonstrated.

Plasma and thermal effects on the performance of high power floating grating DFB laser

Two dimensional finite element analysis of the carrier transport in a 1.55 micrometer floating grating (FG) high power DFB to be used in conjunction with an external modulator as a high bit rate source, has shown that carrier accumulation and crowding for the etch-through grating layers resulted in current being diverted from narrow bandgap sections into the wider band gap sections of the grating. This augments undesirable heating and thermal degradation in laser L-I. To decrease this effect, three changes to the device parameters have been examined. Heavy doping and the use of wider bandgap FG region have been shown to reduce the thermal effects. Thinning the FG layer has little effect. A transfer matrix method (TMM) thermal model has been used to evaluate the performance of the improved structure. The results compared well with measured data and the analysis shows that efficiencies of 0.38 mW/mA and maximum power 100 mW for AR-cleaved are obtainable with the improved FG design.

Spectral domain modeling of distributed feedback lasers

In this paper a.d.c. spectral model of the DFB laser is described. The description is based on the coupled wave theory for corrugated optical waveguides. The analysis is carried out in the spectral domain for a continuum of wavelengths. As such, the model is inherently capable of capturing the effects of all the longitudinal lasing and non-lasing modes.

Mirror effects on dynamic response of surface-emitting lasers

The effects of longitudinal wave distribution and mirror structures on the small-signal response of surface-emitting lasers are analyzed for the first time. The analysis is based on an improved dynamic model implemented in the transfer-matrix representation. It is shown that for two structures with the same threshold gain and the same internal structure, high contrast mirrors give rise to a higher relaxation oscillation and modulation bandwidth for the same injection level.<<ETX>>

10-Gbit/s 80-km fiber transmission using 1.3-/spl mu/m partly gain-coupled DFB lasers

Summary form only given. We have demonstrated l0-Gbit/s 80-km transmission with a receiver sensitivity better than -24.5 dBm at BER of 10/sup -9/ for the long PRBS 2/sup 23/-1 pattern by using our gain coupled (GC) DFB QW lasers, which have been shown to exhibit a high dynamic single-mode yield, large intrinsic modulation bandwidth, and excellent long term reliability.

Small-signal microwave performance of gain-coupled DFB laser array elements at 1.3 μm

The small-signal microwave performance of 1.3 micrometer gain-coupled DFB lasers has been measured as a function of device parameters such as current and ridge width by treating the laser as a two port device. The s-parameters were measured over a frequency range from 0.5 GHz to 8 GHz. The simulation software LIBRA was used with S11 return loss measurements to extract equivalent circuit parameters according to Kan and Laus laser model. Results demonstrate that the parameters describing the input impedance of the laser undergo a discontinuity at the lasing threshold current, Ith. The measured optical intensity modulation (IM) response, (S21), was used to study the behavior of the relaxation oscillation frequency fr as a function of laser bias current. It has been demonstrated that at high laser bias current Ilaser, fr is independent of laser bias current (Ilaser). We have also used the equivalent circuit parameters obtained from the S11 data to predict values for fr based on equations derived. These were then compared to the fr values obtained from S21 measurements.