Laser processing systems ,
Homodyne laser interferometry ,
Linear momentum of light in a medium ,
Laser ultrasound ,
Optodynamics ,
Abraham-Minkowski controversy
We treat the light-matter interaction due to radiation pressure in one dimension using the fundamental, nonrelativistic conservation principles of energy and momentum. Additionally, we assume that the center of mass-energy maintains the same uniform motion if the interaction takes place or not. Since we handle solids as elastic objects, the results are consistent with the principle of causality and agree with recent experimental observations. We analyze the problem of reflection of a light pulse from a fully-reflective mirror and show that its reflection gives rise to an elastic wave with a measurable amplitude and a correct Doppler shift of the reflected pulse. We also analyze the problem of light pulse transmission into an anti-reflection coated, non-dispersive and lossless dielectric, where an elastic wave may as well be accompanied by a mechanical wave escorting the light pulse. We show that the Balazs rigid box thought experiment can be also realized in elastic dielectrics where some of the energy of the incident light is transferred to the wave motion. It follows from our approach that the electromagnetic momentum of the light pulse in the dielectric acquires Abraham’s form only when a single type of the mechanical waves accompanies the interaction.
Optodynamics treats optical manipulation as a superposition of time-developing wave motion induced by a light-matter interaction. When an opaque solid object is manipulated by a pulse of light, various types of mechanical waves are launched from the illuminated surface: ablation-induced waves (AIWs) resulting from material recoil, thermoelastic waves (TEWs), and the light-pressure-induced waves (LIWs) emanating exclusively due to radiation pressure. The manipulated object’s boundaries experience staircase-like displacements with discrete steps caused either by AIWs or LIWs each time these waves are reflected from the interfaces. On the contrary, TEWs cannot translate the center of mass of the manipulated object, but their presence can be inferred from the transient, bi-polar displacements around the equilibrium position.
The goal of this research is to use the information contained in the mechanisms occurring during laser tattoo removal
process. We employed a fast laser beam deflection probe (BDP) to measure the cracking sound that originates from the
dye explosions in the process known as selective photothermolysis. The experiments were performed in vitro (skin
phantoms), ex vivo (marking tattoos on pig skin) and in vivo (professional and amateur decorative tattoos on several
patients). The signal includes the information about the energy released during the interaction, specific for different skin
and tattoo conditions.
This contribution investigates the influence of phase shift on the measured displacement error in interferometers based on
quadrature detection. This error was experimentally investigated using a two-detector homodyne quadrature laser
interferometer (HQLI) with two orthogonally polarized signals. Here, the phase shift can be continuously varied by
rotating a wave plate. However, the rotation of the wave plate also produces unequal signal amplitudes and different zero
offsets, both of which can be corrected with an appropriate signal processing. The measured phase-shift error perfectly
agrees with the theoretically determined phase-shift error region. This error is systematic, periodic and severely
asymmetrical around the nominal displacement value. For the robust realization of a HQLI, a slight deviation from the
aligned angle of the wave plate should not shift the phase significantly from the ideal 90°. This may pose a problem if an
additional phase shift originates from the polarization-sensitive light reflections, such as the reflection at the nonpolarizing
beam splitter.
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