In this paper an optically pumped tunable ring-laser system based on low-loss integrated optic titanium doped sapphirelike waveguides on silicon is presented including simulation results and a characterisation of the realised system.
The Al2O3 thin film layers are doped in situ with titanium in a PECVD deposition from metal-organic precursors. The waveguides are patterned by reactive ion etching (RIE) to obtain high quality, low-loss waveguides. Afterwards the wafer is annealed by RTP (Rapid Thermal Processing). Thereby the layers change to a sapphire-like morphology and the titanium becomes optically activated without the formation of larger crystallites so that higher losses due to scattering are prevented.
For tuning the laser, two solutions are presented. The first is a ZnO based electro-optically tunable etalon which is integrated in the active ring; the second is an also ZnO based coupled ring resonator which can be tuned either by the electro-optical effect or elasto-optically by placing it on a membrane.
The required directional element that ensures the propagation in only one direction of the ring is realised by a new "ratch-reel structure" which acts as an optical diode. As the optical field is shifted to the outer periphery of the ring, it is possible to realise a structure that scatters the optical field in one propagation direction, whereas in the other direction it propagates with low loss.
The system is pumped by a frequency doubled Nd-YAG-laser at 532 nm which is coupled to the ring via a SiON waveguide. The output power is coupled to a tangential waveguide where the coupling coefficient is determined by distance and refractive indices.
In this paper a tunable optic system is presented for use in various optical systems. In contrast to most of the tunable optical components which are composed of a waveguide, an electro-optical layer, and electrodes of different materials. The new system consists of a TiO2 waveguide with ZnO as a functional layer on top. The TiO2 layer acts as a high index waveguide, the ZnO system consists of a ZnO:Al/ZnO/ZnO:Al sandwich structure. The ZnO film is used as an electro-optical cladding for the TiO2 waveguide while the two ZnO:Al films act as transparent electrodes. Applying a voltage results in a shift of the effective refractive index of the waveguide because of the electro-optical effect of the ZnO. The TiO2 film is deposited on SiO2 by a PECVD-process from a metal organic precursor CpTiCh (cyclopentadienyl-cycloheptatrienyl-titanium). ZnO and ZnO:Al are rf-sputtered from a Zn target and ZnO:Al target, respectively. While both ZnO layers are c-oriented polycrystals, the TiO2 grows in a nanocrystalline formation without any texture. The configuration of the high index material TiO2 in combination with the transparent and electro-optical ZnO layer allows the use in integrated optical subsystems such as active couplers or active micro ring resonators. The system is designed for a wavelength of 1550 nm.
We present a method for analyzing the homogeneity of the (chi) (2) distribution in poled nonlinear optical polymer films. The second order nonlinear coefficient in these polymers is commonly induced by electric field poling methods which can lead to a (chi) (2) distribution with poor spatial homogeneity. In this paper, we analyze the (chi) (2) distribution using scanning Kelvin microscopy. This allows us to detect the height and the direction of the induced polarization through the probing of the counter charges that are present on the polymer surface. We compare the response to that obtained from the scanning second harmonic microscopy (SSHM) method, in which the direction of the orientation, and thus the phase of (chi) (2), can not be seen. We also propose a method to measure the (chi) $_(2)) distribution in 3D by analyzing the SSHM images obtained at various wavelengths.
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