By laser-induced backside wet etching (LIBWE), we can fabricate microfluidic channels on silica glasses. These channels have
smooth bottom surfaces that can be combined with various optical detection techniques. Antiresonant guided optical wave (ARGOW)
is a concept for guiding light in the system composed of a low refractive index medium surrounded by a medium with higher
refractive index. The ARGOW was examined by using the wide channels (length: 17 mm, width: 1 mm, depth: 45 μm) prepared by
LIBWE, whose bottom surface showed root-mean-square (RMS) roughness less than 100 nm. The LIBWE can fabricate deep
trenches with high aspect ratio (~57 (length: 1mm, width: 10 μm, depth: 566 μm)). By using such deep channels, ARGOW system
within a plane parallel to the top surface of glass can be fabricated. In this work, surface roughness of the sidewall of deep trenches
prepared with LIBWE was evaluated, and the possibility of utilization for guiding light is discussed.
The waveguiding properties of SC-450 photoresist films are presented. The basic waveguiding properties such as refractive index, propagation losses, thickness, and birefringence of photoresist film are optimized. The effect of dye doping and UV exposure on photoresist film is also observed. The film shows excellent transmission (above 90%) in the wavelength range of 500 to 1500 nm. The present results suggest that photoresist films may be the good option to be used as an optical component.
Polyvinyl alcohol (PVA)-based thin film optical waveguides are fabricated and characterized. Various waveguide parameters, namely, refractive index, propagation losses and depth, birefringence, and polarization conversion properties of dip-coated thin film optical waveguides are evaluated. The effective refractive index of PVA film is found to be between 1.506 and 1.531 for various concentrations. The propagation losses are 2.35 to 0.30 dB/cm for various thicknesses. The propagation loss reduces when the thickness of the film is increased. The low propagation losses, birefringence insensitivity, high transmission in the aged and annealed waveguides, control over film refractive index, the good adhesiveness of the film and good compatibility with substrate show that PVA-based waveguides are promising candidates for the optoelectronic field.
Negative photoresist films (HNR-80 and HNR-120) are fabricated and characterized for waveguiding purpose. Various waveguiding parameters, namely, refractive index, thickness, propagation losses, and birefringence of the photoresist films are evaluated. Propagation losses are optimized to the value of 0.29 dB/cm for both materials. These photoresist materials show excellent transmission with almost no absorption in the wavelength range of 400 to 900 nm. The waveguides are polarization insensitive for various temperatures. Considering these properties, these materials offer a good option to use as waveguiding materials in integrated optics.
When sufficient intense laser pulse interacts with semi-conductors, permanent damage results due to formation of scattering centers in the semi-conductor surface. Reflectance of the damaged surface is reduced as compared to the smooth surface. Generally, damage threshold is defined as a value for which the reflectance is decreased by more than 10%. It is interesting that reflectance change can be seen below the damage threshold value. In the present work it has been shown that these changes occur at the rate of 0.5% per pulse. These changes are not due to any type of irreversible process in the material and slow but continuous decrease can be seen in the reflectance if the number of pulses is increased. Although when the fluence is increased, remarkable change can be seen in the reflectance decrease for the first pulse (in some cases, for 2-3 pulses), but if the number of incident pulses are further increased, the slow and continuous decrease is shown in reflectance value.
The present experiments were performed in the CdZnTe <111> single crystal surface exposed to Nd:YAG laser (pulse duration: 20ns, prs:1pps, wavelength: 1.064µm) in the ambient air.
In this paper homogeneous model for surface roughness in identical layer system has been presented. It has been shown that reflectance change in non-absorbing layer is directly proportional to the square of total thickness of the layers. The reflectance in the visible range of the wavelength changes (decreases) substantially when the roughness factor or the number of layers are increases. In the present model the reflectance of the double layer system can be explained with the help of only one parameter that is roughness factor σ.
Polymeric Optical Waveguides have attracted a lot of attention with a view to their flexibility for fabrication and their cost effectiveness. In the search for new materials recently the study of Styrene Acrylonitrile (SAN) thin film optical waveguides has been reported. SAN exhibits a considerable transmission (80-90%) in the visible and infrared regions, which is important for integrated optical devices. But the propagation loss is a major drawback of SAN based waveguides. Here we report 4-layer waveguides with Glass plus SAN plus Polystyrene plus air, structure. With the help of this multilayer structure we were able to reduce propagation loss by 30% in comparison to single layer SAN based waveguides. We also present the other basic properties like index profile, guide thickness, birefringence.
Pits formation during the laser induced damage with GaAs surface either for picosecond or for femtosecond laser pulses, shows that defects always play an important role in damage morphology of GaAs surface, as previously these pits formation have also been seen for micro and nanosecond laser pulses. The nature of these pits gives an important information about the morphological features of damaged GaAs surface in picosecond and femtosecond regime. In this paper we report a comparative study of laser induced damage morphology of GaAs surface based on the nature of these pits formation.
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