Neodymium-doped waveguide amplifiers and lasers for integrated optical applications

Abstract: In this thesis neodymium-doped polymer and amorphous aluminum oxide waveguide amplifiers and lasers for integrated optical applications have been realized. Nd3+-complex-doped, photo-defined polymer channel waveguides were realized on thermally oxidized silicon wafers with a simple and reproducible fabrication procedure by dividing the functionalities of photo-definition and active doping over two different polymers. Waveguides had very low loss in the visible and near-infrared wavelength range below 1.1 µm. A high internal net gain of 5.7 dB/cm has been demonstrated at 1064 nm. In the wavelength range between 865 and 930 nm, internal net optical gain with up to 2.8 dB gain was obtained at 873 nm by optimization of the Nd3+ concentration and channel waveguide length. Laser experiments of polymer channel waveguides have resulted in lasers operating at the four-level as well as the quasi-three-level transition near 1060.2 nm and 878 nm, respectively. These lasers exhibit remarkable lifetime stability, as they can withstand at least two hours of uninterrupted operation when pumping with up to 150 mW. The maximum output power of the polymer laser was ~1 mW. This is the first demonstration of a rare-earth-ion-doped polymer waveguide laser as well as a CW solid polymer laser. The thermally more stable amorphous aluminum oxide was investigated as a host material. Al2O3:Nd3+ films were deposited on thermally oxidized silicon wafers using reactive co-sputtering, and reactive-ion-etch was applied to realize low-loss waveguide structures in the films. High-gain waveguide amplifiers have been demonstrated. At the investigated signal wavelengths of 880 nm, 1064 nm, and 1330 nm small-signal gain of 1.57 dB/cm, 6.30 dB/cm, and 1.93 dB/cm, respectively, has been measured for individually optimized Nd3+ concentrations. The feasibility of using Al2O3:Nd3+ channel waveguides as amplifiers between polymer waveguides in optical backplanes has been investigated. Al2O3:Nd3+ channel waveguides with a PECVD SiO2 layer as an upper cladding were placed in between polymer waveguide samples to achieve optical amplification in optical waveguides on backplanes. A maximum of 0.42 dB internal net gain has been demonstrated in a polymer waveguide coupled to an Al2O3:Nd3+ waveguide. Therefore, a solution for compensating optical loss in optical interconnects has been provided