Improved Sampled Grating DBR Widely-Tunable 1.55 micrometer-Lasers

Abstract

Over the last three years, a number of improvements have been made in the design of SGDBR lasers with integrated componentry. Device design has improved the output power and tuning range due to an increase in the number of quantum wells in the active region from four to six. Devices with up to 8 mW of output power with integrated amplifiers and buried heterostructure devices with 72 nm tuning ranges were realized. Current laser results indicate that leakage current in buried heterostructure lasers is a major factor in limiting the device performance. To eliminate the parasitic leakage paths we have begun to investigate Fe doped blocking junctions for the device. Work on the wavelength monitor has focused on an external approach, which uses a wavelength dependent coupler in conjunction with a pair of photodetectors. Initial results show better than 1 nm sensitivity over a 30 nm range. The most recent work on the laser has focussed on integrating additional components for increased functionality. We have developed a curved waveguide semiconductor optical amplifier that can be integrated with the laser to increase the output power to greater than 6 mW.We have also investigated SGDBR lasers with integrated electro-absorption modulators. Using a 300 urn long bulk EA modulator we have demonstrated error free data transmission at 2.5 GBit/s with a 2 3I -1 pattern length at received powers of-32.5 dBm. Subject termsSemiconductor lasers, photonic integrated circuits, wavelength monitors, WDM devices, semiconductor optical amplifiers, electro-absorption modulators IntroductionThe goal of this program was to develop a widely tunable semiconductor laser diode with an integrated wavelength monitor. The widely tunable laser is a four section device with a pair of sampled grating distributed Bragg reflector mirrors as shown in figure 1. These devices use a Vernier effect tuning mechanism to provide widely tunable wavelength ranges. Because of the simple offset waveguide design, SGDBR lasers are easily integrated with other optoelectronic devices such as wavelength monitors, optical amplifiers, and modulators to form photonic integrated circuits. They employ periodically sampled grating mirrors which have multiple reflection peaks spaced approximately 5-7 nm apart. The duty cycle and sampling periods have been optimized for the desired wavelength coverage. A phase control section is included to enable alignment of the cavity mode with the mirror reflection peaks. Devices were fabricated using both ridge and buried ridge waveguide processes with passive regions formed by a combination of etching and MOCVD regrowth.This work is discussed in detail in Dr. T.G.B Mason's dissertation -which is included as Appendix I. Supplementary material outlining work on semiconductor optical amplifiers (SOAs) and Electro-absorption modulators (EAM) is also included in the report. Thesis summaryFirst we will briefly summarize the key results from Dr. Mason's dissertation. In appendix I, Dr. Mason discusses the design and development of ph...