Gongyuan Zhao

Design and simulation of two-section DFB lasers with short active-section lengths.

Distributed feedback lasers comprised of a reflection section and an active section have been proposed for high direct-modulation bandwidth. The reflection section has the same core layer as the active section so butt-joint re-growth is avoided. Without current injection the reflection section will be pumped to near transparency by the emission from the laser itself so high reflection (> 0.75) can still be achieved as confirmed by the simulation. Therefore a short (150 µm) active section can be used, which enables a low threshold current (~5 mA) and a high direct modulation bandwidth (>30 GHz) as demonstrated by the simulation.

Demonstration of Multi-Channel Interference Widely Tunable Semiconductor Laser

In this letter, we report the first experimental demonstration of the multi-channel interference (MCI) widely tunable semiconductor laser. Mode selection of the MCI laser is achieved by the constructive interference of eight arms with unequal length difference. Compared with conventional widely tunable semiconductor lasers based on distributed Bragg reflectors, fabrication of the MCI laser is simpler with large fabrication tolerances. A quasi-continuous tuning range of about 52.3 nm (1538.96-1591.26 nm) has been demonstrated at a temperature of 23 °C with side-mode suppression-ratios greater than 44 dB across the whole tuning range (typically greater than 48 dB).

High-speed directly modulated lasers based on high-order slotted surface gratings

Directly modulated semiconductor lasers (DMLs) are important components as sources for short distance communication. In this paper, we present 1.3μm directly modulated lasers with high modulation bandwidth based on high-order slotted surface gratings. Such lasers are regrowth free, thus have the advantages of low cost and high reliability compared to the typical distributed feedback Bragg (DFB) lasers with buried gratings. The two dimensional (2D) scattering matrix method (SMM) combined with the time-domain travelling-wave model (TDTW) is employed for the analysis of the designed laser. By optimization of the grating parameters and cavity length, the slope efficiency about 0.35mW/mA and 3-dB-down frequency bandwidth higher than 41GHz have been achieved for a 250μm long high-order slotted surface grating laser.

High SMSR monolithic widely tunable semiconductor lasers based on multi-channel interference

Monolithic widely tunable semiconductor lasers based on multi-channel interference (MCI) have been demonstrated with tuning range more than 53.6 nm and SMSR up to 52 dB being achieved.