Abstract We use InGaAlAs and InGaAsP as materials of 1.55mm multi-quantum-well spot-size converter ridge waveguide lasers. On lateral conversion, we fabricate a taper ridge waveguide. On vertical conversion, we add guard layers on each side of active layer. For InGaAlAs ridge waveguide lasers, simulation results show a far field 16o ¡Ñ 27o¡]lateral ¡Ñ vertical¡^at guard layer width S = 0.1 mm with 300-150-50 mm narrow-tapered waveguide structure. Due to large Zn background contamination in the MOCVD growth chamber, we did not fabricate the InGaAlAs lasers successfully. For the InGaAsP ridge waveguide lasers, we measure a far field 18o ¡Ñ 28o and a threshold current 23 mA for the 200-250-50 mm narrow-tapered waveguide structure; a far field 20o ¡Ñ 26o and a threshold current 22 mA for the 200-250-50 mm wide-tapered waveguide structure.

Semiconductor corrugated ridge waveguide (CRW) distributed feedback (DFB) lasers offer compelling advantages over standard DFB lasers. Indeed, the use of surface gratings etched on the ridge waveguide sidewalls in CRW-DFB devices avoids any epitaxial overgrowth. This provides a considerable simplification in the fabrication process, reducing cost and time of manufacturing, and ultimately increasing yield. It offers also the potential for monolithic integration with other devices, paving the way towards low-cost and mass-production of photonics integrated circuits. In recent years, the re-consideration of growth-free DFB lasers has drawn considerable attention, particularly with the current state-of-the-art photolithography machines. In this work, we present an experimental investigation on two generations of InGaAsP/InP multiple-quantum-well (MQW) CRW-DFB lasers that have been fabricated using stepper lithography. An early developed 1310 nm CRW-DFB laser showed stable single mode with high side-mode suppression ratios (SMSR) (>50 dB), albeit with thresholds higher than anticipated. A subsequent single-mode 1550 nm CRW-DFB laser showed stable operation with SMSR (>50 dB) and narrow spectral linewidths (≤250 kHz), observed for a wide range of current injection. Besides, novel multi-electrode CRW-DFB lasers have been tested. The experimental investigation showed that narrower linewidth (<150 kHz) and wide wavelength tunability (>3 nm) have been recorded using different multi-electrode current injection configurations. The application of a time-domain modeling approach for semiconductor CRW-DFB lasers is then described for the first time. We numerically studied the effect of the radiation modes on CRW-DFB laser properties by using time-domain coupled wave equations. High-order corrugated gratings with λ/4 phase-shit were analyzed, where the degree of longitudinal spatial hole burning (LSHB) can be effectively reduced by means of fine tuning of the grating duty cycle. Additionally, we showed how the side-mode suppression ratio can be predicted depending on the device geometry.

With a rapid increase in information capacity of Internet access, high-speed, highly-efficiency, and cost-effectiveness laser source for optical fiber communication is required. High-speed 25Gb/s directly modulated laser is essential of this communication range, because of its simple structure, direct-modulation characteristics, low cost, and integration capability for wavelength division multiplexing (WDM) system, and moreover, it can achieved 100Gb/s data transmission by four channel module system. In this work, data modulation speed of 25Gb/s direct modulation DFB laser has been achieved. By employing high-speed coplanar waveguide structure with semi-insulating substrate, high-speed with f3dB > 20GHz has been demonstrated. By the electrical reflection measurement, it confirmed that the high-speed direction modulation can be realized through reduction of electrical parasitics. The laser chips is measured under continuous-wave mode at room temperature. In 1300nm and 1550nm wavelength device, slope efficiency obtained by taper fiber coupled of 0.045 and 0.07mW/mA respectively, output power up to 2.73 and 3.96mW/facet at 60mA. The Side Mode Suppression Ratio was greater than 35dB. 3dB bandwidth of greater than 16GHz and 20.5GHz, relaxation oscillation frequency of 12GHz and 16.6GHz. Finally, clearly back-to-back 25Gb/s eye diagram and error-floor-free performance were obtained.

A transmission line format is presented which takes the form of a Multilayer Ridged Substrate Integrated Waveguide, for which signal energy is transmitted within standard PCB substrates, within a wave-guiding structure formed from conducting tracks in the horizontal plane and arrays of through-plated vias in the vertical plane. The Substrate Integrated Waveguide (SIW) is a recent development into which research is so far concentrated on single-layer rectangular variants which, like traditional rectangular waveguide, are amenable to analytic computation of the cutoff eigenvalues. Recent publications have offered empirically-derived relationships with which a Substrate Integrated Waveguide can be analysed by equivalence of the horizontal dimensions with a conventional waveguide, allowing such structures to be designed with minimal effort. We propose a ridged form of this structure, in which multiple PCB layers are stacked to obtain the desired height and the published equivalent width is used to obtain the horizontal dimensions. The proposed structure combines the increased bandwidth of ridged waveguide with SIW’s greatly reduced cost of manufacture and integration, relative to conventional waveguide, and improved power handling capacity and loss susceptibility relative to microstrip. Ridged variants have not yet been studied in the literature, however, in part because the eigenspectrum can not be obtained analytically. We thus present a semi-analytical software model with which to synthesise and analyse the cutoff spectrum in ridged Substrate Integrated Waveguide, verified by comparison with analytical solutions, where they exist, simulation in finite-element software and a physical prototype. Agreement with simulated and measured results is within 1 % in certain subsets of the parameter space and 11 % generally, and individual results are returned in times of the order of seconds. We use the model to analyse the relationship between geometry and frequency response, constructing an approximating function for the early modes which is significantly faster, such that think it can be used for first-pass optimisation. A range of optimal parameters are presented which maximise bandwidth within anticipated planar geometric constraints, and typical design scenarios are explored.

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