A time-domain traveling wave algorithm is extended to investigate high-order quantum dot based laterally-coupled distributed feedback semiconductor lasers. The effect of radiation modes in laser performance is included via Streifer’s terms. We calculate the optical gain spectra based on a coupled set of rate equations and taking into account both inhomogeneous broadening due to dot size fluctuation and homogeneous broadening due to polarization dephasing. It was found that, for third-order quantum dot based laterally-coupled distributed feedback lasers; a stable single mode operation with high SMSR can be achieved by means of fine tuning of the grating duty cycle
There has been much interest in developing low-cost laser sources for applications such as photonics integrated circuits
and advanced coherent optical communications. The ultimate objectives in this development include wide wavelength
tunability, a narrow linewidth, and an ease of integration with other devices. For this purpose, semiconductor surface
grating distributed feedback (SG-DFB) lasers have been introduced. SG-DFB manufacturing consists of a unique
sequence of planar epitaxial growth resulting in a major simplification to the fabrication process. SG-DFB lasers are
highly monolithically integrate-able with other devices due to their small footprint.
The segmentation of the built-in top electrode helps to alleviate the adverse spatial-hole burning effects encountered in
single-electrode devices and brings hence significant enhancements to the laser performance. For the first time, we report
here on the design, fabrication, and characterization of InGaAsP/InP multiple-quantum-well (MQW) SG-DFB lasers
with uniform third-order surface grating etched by means of stepper lithography and inductively-coupled reactive-ion.
The uncoated device reported here is 750 μm-long SG-DFB laser whose central and lateral top electrodes are 244 μmlongs
each, separated by two 9 μm-long grooves. The experimental characterization shows stable single mode operation
at room temperature under uniform and non-uniform injection. High side mode suppression ratios (SMSRs) (50-55dB)
under a wide range of injection current have been discerned as well. A relatively broad wavelength tuning (<4nm) has
also been observed. Moreover, a narrow linewidth (<300 kHz) has been recorded for different injection currents.
In this work, we numerically study the effect of high-orderλ /4 phase-shift grating in laterally-coupled distributed
feedback (LC-DFB) lasers performance. It is well known that single-mode operation is improved by introducing λ/4
phase-shift grating in conventional DFB lasers. However, introducing λ/4 phase-shift region increases the optical
intensity around this region and results in strong longitudinal spatial-hole burning (LSHB). To flatten the longitudinal
carrier density distribution, we have numerically studied the effect of the radiation modes on high-order LC-DFB lasers
using a modified time-domain travelling-wave algorithm. It is shown that, the degree of LSHB can be effectively
reduced when considering high-order LC-DFB lasers with grating duty-cycle tailored to optimal values. LC-DFB laser
cavity with high-order grating shows a strong non-uniformity of the carrier density distribution. However, as we finely
engineer grating features, LSHB is highly reduced and high single mode suppression ration can be achieved.