The Optimization Of Semiconductor Lasers Based On Equivalent Phase Shift Technique And Its Applications

With the development of the Internet and wireless communication, people have higher requirements of the volume of data traffic and the speed of the access to the Internet. As a result, the traditional optical communication networks composed of discrete devices have been under great pressure. At the same time, more communication facilities are being deployed and the datacenters are expanding rapidly, which have caused the problem of huge energy consumption. To solve the problems of reaching the bandwidth limitation of optical communication and the huge energy cost by optical networks, people believe that the most effective solution is to integrate the different kinds of optoelectronic devices onto a single chip. In recent years, photonic integrated circuits are always the hottest research topics in the area of optical communications, including the hot silicon photonics platform and the relatively mature InP platform, which are both promising for the development of future integrated optics.However, whether it is the silicon photonics platform or the InP platform, the semiconductor laser arrays are always the key devices needed. Among them, as the sources of the optical communication systems, the distributed feedback (DFB) semiconductor lasers are important devices focused on by researchers. With the development of the optical communication systems, the performance of single DFB semiconductor laser has been improved dramatically. However, it is still not easy to make the DFB laser arrays with precise wavelengths as well as high performance. DFB laser diodes usually use the Bragg gratings to ensure the stable single-longitudinal operations and the grating periods are usually around 200 nm. To make the DFB laser array with precisely controlled wavelengths, the precision of the change of the grating periods will be required as small as 0.1 nm. Even the electron-beam lithography (EBL) can hardly meet the strict requirements. What’s more, there are several drawbacks of EBL, like slow and complicated processes, low yields and high cost, which is not considered to be suitable for mass production. To solve these problems, a new technique called reconstruction equivalent chirp (REC) technique has been proposed to make low-cost DFB semiconductor laser arrays. The main research emphasis of this thesis is to make DFB laser arrays with low cost and high performance based on REC technique and make new integrated devices based on the laser array as well.The first chapter is the general introduction of this thesis, which introduces the research background of the DFB semiconductor laser and the development of photonic integrated circuits. What is more, we also introduce the principles of REC technique as well as the research achievements based on the REC technique.In chapter two, we first introduce one of the standard structures of the DFB semiconductor laser diode. Then, based on the structure, we derive the formulas to calculate the index coupling coefficient of the laser, which is one of the key parameters affecting the laser’s performance. What is more, we study how coating films can affect the laser’s performance, including two main kinds of coating films, the high-reflection film (HR) and anti-reflection film (AR). To improve the DFB laser’s performance, we propose a new way to make the DFB laser diode, using the asymmetric phase shift. We also use simulation software called ALDS to simulate the structure and have achieved good results.In chapter three, we report the experiment results of high-performance DFB semiconductor laser arrays. We use the buried heterostructure (BH) to make the laser arrays, which have the advantages of low threshold, high output power, low noise and narrow linewidth. Combined with the REC technique, we have successfully fabricated the DFB semiconductor laser array based on the BH structure in both of the 1550 nm and 1310 nm communication windows. The tested results have shown that the fabricated laser array have pretty good performance and have the potential for industrialization.In chapter four, we propose a new type of tunable laser based on the REC laser array. This tunable laser chip uses an eight-wavelength DFB laser array based on the REC technique, which have excellent single-longitudinal operations. By using a TEC controller to change the temperature, a large wavelength tuning range of 25 nm has been achieved with good performance. We tested the compact tunable laser chip and successfully make it into a module with small size.In chapter five, we make the summary and forecast about the research work in this thesis.