Laser diffraction experiment discussion1/15/2024 The diffraction patterns were captured with an inexpensive digital camera and processed with a simple digital spatial Fourier filter. We observed diffraction patterns whose topology and geometry may be correlated with the spatial physicochemical characteristics of a liquid. Here, we report on the observation of diffraction patterns when a secondary hydrogen-bonded liquid was exited with a femtosecond laser emitting at 1040 nm, and it was probed with multiple wavelengths, more specifically, with supercontinuum visible light, i.e. Thus, an approach or technique that is less sensitive to different experimental factors and that can provide a specific signature about the sample is highly desirable to expand the use of the photothermal lens phenomenon. This means, the photothermal lens technique cannot provide any data or information with which a sample or molecules can be identified. However, intensity changes are relative and do not depend exclusively on how much light was absorbed by a sample they can also be affected by external factors or by the experimental conditions. From the time- or amplitude-dependent signals, the aforementioned physical and thermo-optic properties of a sample can be obtained. In the vast majority of works reported in the literature, the intensity of the pump or probe beam is monitored as a function of time 7, 10, 11, position 17, or concentration 19. For these reasons, the photothermal effect has multiple practical uses ranging from material characterization 16 to applications in biomedicine 17, in analytical chemistry 8, as well in lab-on-a-chip 14, 18, in microscopy 19 and in thermoplasmonics 6, 20. Such properties include absorbance, density, thermo-optic coefficient, heat capacity, thermal conductivity, etc. The use of two different lasers entails critical alignment and increases the bulkiness of the setup, which may limit its practical applications 9, 12.įrom the intensity changes caused by the thermal lens, the optical and thermophysical properties of samples can be indirectly obtained 4, 5, 13. In this case, the thermal lens gives rise to intensity changes of the probe beam that are easily monitored with a photodetector. The thermal lens can also be analyzed with two laser beams with two different wavelengths one is used as the excitation or pump beam and the other as the probe one 9, 10, 11. The disadvantages in this case are the large dimensions and instability of the measuring setup. The thermal lens in pure liquids can deflect the same light beam that causes it such deflection can be detected as intensity changes with a pinhole detector placed a few meters away from the sample 7, 8. In liquids with a negative thermo-optic coefficient, the laser-exposed region can act as a negative lens that alters or deflects the optical path of a light beam that crosses such a region 6. Hence, a laser-liquid interaction gives rise to a local inhomogeneous alteration of the sample´s refractive index 4, 5. The laser-liquid interaction can cause temperature changes in the zone of the sample that interacts with the excitation laser beam. The interaction of laser light with known properties with polar or non-polar liquids has opened the door to investigate the linear and nonlinear thermal properties of liquids as well as stationary and time transient effects in them 1, 2, 3. Thus, it may be useful for the development of compact thermal lens spectroscopic instruments for a number of practical applications. The technique proposed here is noninvasive and simple to implement with commercially available supercontinuum sources and digital cameras. The specific diffraction patterns may be considered as the optical signatures or fingerprints of the liquids studied. The latter alters the wavefront of a white-light probe beam, giving rise to unique diffraction patterns that can be observed in the far field. Such interaction induces a local change in the sample’s index of refraction. Here, we report on the interaction of tightly focused femtosecond infrared light into secondary hydrogen-bonded liquids like water, organic compounds, and binary mixtures. However, from just temperature changes, a sample cannot be identified. The interaction of a laser with a liquid can cause temperature changes in the liquid from which some properties of the latter can be indirectly obtained.
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