Browsing by Subject "Integrated optics."

Now showing 1 - 5 of 5

Open Access
Computer aided analysis and simulation of complex passive integrated optical circuits
(1993) Önal, Gürkan
In this thesis, a method is developed for the analysis and simulation of arbitrary complex, single layer, rectilinear, passive optical interconnection circuits. The method considers dielectric waveguide type optical interconnections which can be beneficially employed at the chip-to-chip or backplane level of high performance computing circuits. In the method developed, a circuit is broken down into elementary blocks whose loss and coupling properties are known. Thus, the overall loss and noise for each connection can be calculated. A high speed algorithm based on this method has been imjjlemented. The high speed of the analysis system makes it suitable for incorporation in an iterative design system, which determines the minimum spacings I)etween the guides that result in acceptable crosstalk and noise levels.
Open Access
The Examination of the effect of polarization on the radiation losses of bent optical fibers
(1990) Tanyer, Süleyman Gökhun
It has long been recognized that the bending losses in weakly guiding optical fibers, is independent of the polarization for large bend radius. We showed this fact using the volume equivalent current method. The procedure is then applied to a helically bent fiber, and it is shown that the radiation from the helical fiber is also independent of the polarization as long as the fiber is weakly guiding.
Open Access
Grating loaded integrated optical cantilevers
(2010) Karademir, Ertuğrul
Cantilever beams are the most important parts of standard scanning probe microscopy. In this work, an integrated optical approach to sense the deflection of a cantilever beam is suggested and realized. A grating coupler loaded on the upper surface of the cantilever beam couples the incident light to the chip, which is then conveyed through a taper structure to a waveguide to be detected by a photodiode. Deflections of the cantilever beam change the optical path and hence the total transmitted intensity. Finally an optical signal is produced and this signal is measured. Resonance peak of 27.2 Q factor is obtained, which could be further enhanced by proper vibration isolation and employment of vacuum environment.
Open Access
Silicon based dielectrics : growth, characterization, and applications in integrated optics
(2005) Ay, Feridun
In recent years, growing attention has been paid to silicon based dielectrics, such as silicon oxynitrides, silicon nitrides, and semiconductor doped silicon oxides, all combined under the name silica on silicon technology. This attention has been motivated mainly due to their excellent optical properties such as well controlled refractive index and high transparency over a wide range of wavelength. In accordance with the main goal of this study that relied on the utilization of silicon based dielectrics and their optimization for applications in integrated optics, an emphasis was given to optimize the compositional and optical properties of these materials. A detailed quantitative compositional analysis using Fourier transform infrared spectroscopy resulted in identification of the germanosilicate dielectrics as the most promising candidates for use in integrated optics. The first reported systematic study of propagation losses for different-index planar waveguides by using prism coupling method was correlated with the compositional analysis. This study had an important outcome for planar waveguides fabricated with germanosilicate core layers resulting in the lowest propagation loss values reported so far for as deposited CVD-grown films at λ=1.55 µm, eliminating the need for costly and cumbersome annealing process. An improvement of the prism coupling technique led to a new approach for elasto-optic characterization of thin polymer films. This completely new method allows one to determine the optical anisotropy and out-of-plane mechanical properties and to correlate both in order to obtain the elasto-optical properties of thin polymer films, for the first time. Of interest as potential electro-optic material, we have concentrated on thermally poled germanosilicate films deposited on fused-silica substrates by PECVD. As a result of an optimization study, we demonstrated a record peak nonlinear coefficient of ∼1.6 pm/V, approximately twice as strong as the highest reliable value reported in a thermally poled fused silica glass. Finally, we have demonstrated several applications of this technology in the field of integrated optics. Since optical waveguides constitute the building blocks of many integrated optical devices, we had first concentrated on design and optimization of waveguides employing germanosilicates as the core layers. The final step of our work concentrated on design and implementation of microring resonator devices based on germanosilicate layers.
Open Access
Silicon-on-insulator optical waveguides and waveguide devices
(2000) Kiyat, İsa
Silicon-on-insulator(SOI) optical waveguides, directional couplers and some types of MMI couplers were designed, fabricated and characterized at a wavelength of 1.55 /im. Effective index method and the single mode condition for rib waveguide was used in design of optical waveguides. BPM simulations were extensively employed for all fabricated devices. Waveguides and the other devices were defined on SOI material by wet chemical etching in KOH solutions^ Fabricated devices were characterized on a standard fiber optic measurement setup with a DFB laser as its IR light source. In characterization of optical waveguides the single mode condition was verified and insertion loss was measured to be 12.2 dB for TE and 12.7 dB for TM polarized light as the best values. Furthermore, the propagation loss found to be 0.70 dB/cm for TE and 0.76 dB/cm for TM which is typical . Characterized directional couplers gave results completely consistent with their BPM simulations. 1x2, 2x2, 1x4 and 1x8 type MMI couplers were also found to gave expected behaviors. Splitting ratios as low as 0 dB and 0.55 dB was measured.