High-power lasers are useful instruments suitable for applications in various fields; the most common industrial
applications include cutting and welding. We propose a new application of high-power laser diodes as in-bulk heating
source for food industry. Current heating processes use surface heating with different approaches to make the heat
distribution more uniform and the process more efficient. High-power lasers can in theory provide in-bulk heating which
can sufficiently increase the uniformity of heat distribution thus making the process more efficient. We chose two media
(vegetable fat and glucose) for feasibility experiments. First, we checked if the media have necessary absorption
coefficients on the wavelengths of commercially available laser diodes (940-980 nm). This was done using
spectrophotometer at 700-1100 nm which provided the dependences of transmission from the wavelength. The results
indicate that vegetable fat has noticeable transmission dip around 925 nm and glucose has sufficient dip at 990 nm. Then,
after the feasibility check, we did numerical simulation of the heat distribution in bulk using finite elements method.
Based on the results, optimal laser wavelength and illuminator configuration were selected. Finally, we carried out
several pilot experiments with high-power diodes heating the chosen media.
Laser speckle analysis is a very powerful method with various existing applications, including biomedical diagnostics. The majority of the speckle applications are based on analysis of dependence of scattered light intensity distribution from sizes of the scattereres. We propose a numerical model of speckle formation in reflected light in one-dimension which shows that properties of the scattered light are strongly dependent on the form of the scatterers. In particular, the dependence of number of speckles from the size of the scatterers was investigated for the light reflected from the surface with varying roughness; the single roughness on the surface was assumed to have the form of one-dimensional ‘pyramid’ with the sides having either linear or parabolic descent from the top of the ‘pyramid’ to the bottom. It was found that for the linear roughness, number of speckles decreased with increase of the roughness size, whereas for the parabolic roughness the number of speckles increased. Results of numerical simulation were compared with experiment investigations of roughness samples (0.5-2.5 μm) made of glass and copper. Due to different production processes, the glass samples are likely to have the parabolic roughness and copper samples are likely to have the linear roughness. Experiments show that the dependences of number of speckles also have different slopes, the same as in numerical simulation. These findings can lead to new analytical methods capable of determining not only the size distribution of roughness (or scatterers) but also the shape.