Umbrales de ablación láser en metales a diferentes longitudes de onda
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Date
2023
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Universidad Nacional de Trujillo
Abstract
En este trabajo de tesis se determinaron los umbrales de ablación láser de los metales cobre, oro y plata para dos diferentes longitudes de onda (532 nm y 1064 nm), utilizando un láser pulsado Nd:YAG con una duración de pulso del orden de los nanosegundos. Se empleó la técnica fotoacústica pulsada para registrar las señales fotoacústicas producidas debido a la interacción de la muestra metálica con los pulsos láser. Dichas señales se analizaron mediante correlación estándar y los cambios en la amplitud fotoacústica conforme aumentó la fluencia láser. Los resultados indican que las señales fotoacústicas son muy sensibles a cambios físicos que experimenta una muestra sólida debido a la interacción con pulsos láser, pudiendo diferenciarse claramente el cambio del régimen termoelástico al de ablación y por consiguiente el umbral de ablación. Los valores experimentales obtenidos para la fluencia del umbral de ablación láser (𝐹𝑢) fueron los siguientes: muestra de cobre, para 𝜆=1064 𝑛𝑚, 𝐹𝑢= (1,71±0,08) J/cm2 y para 𝜆=532 𝑛𝑚, 𝐹𝑢= (0,91 ± 0,11) J/cm2; muestra de plata, para 𝜆=1064 𝑛𝑚, 𝐹𝑢=(1,15±0,05) J/cm2y para 𝜆=532 𝑛𝑚, 𝐹𝑢= (0,66 ± 0,06) J/cm2; muestra de oro, para 𝜆=1064 𝑛𝑚, 𝐹𝑢= (1,66±0.09) J/cm2 y para 𝜆=532 𝑛𝑚, 𝐹𝑢= (0,13±0,03) J/cm2. Se demostró que la fotoacústica pulsada es muy apropiada para la determinación de umbrales de ablación láser de metales con las ventajas que la muestra no requiere tratamiento especial, ni debe ser de una forma determinada, y la sensibilidad es comparable o superior a otras técnicas convencionales utilizadas; el proceso se monitorea en tiempo real, y no se requiere amplificación ya que las señales fotoacústicas tienen amplitudes del orden de voltios y una buena relación señal/ruido.
In this thesis work, the laser ablation thresholds of the copper, gold and silver metals were determined for two different wavelengths (532 nm and 1064 nm), using a pulsed Nd:YAG laser with pulse duration of the order of nanoseconds. The pulsed photoacoustic technique was used to record the photoacoustic signals produced due to the interaction of the metallic sample with the laser pulses. These signals were analyzed using standard correlation and changes in photoacoustic amplitude as laser fluence increased. The results indicate that the photoacoustic signals are very sensitive to physical changes experienced by a solid sample due to the interaction with laser pulses, being able to clearly differentiate the change from the thermoelastic regime to the ablation regime and consequently the ablation threshold. The experimental values obtained for the fluence of the laser ablation threshold (𝐹𝑢) were the following: copper sample, for λ = 1064 nm, 𝐹𝑢 = (1.71 ± 0.08) J/cm2 and for λ = 532 nm, 𝐹𝑢= (0.91 ± 0.11) J/cm2; silver sample, for λ = 1064 nm, 𝐹𝑢 = (1.15 ± 0.05) J/cm2 and for λ = 532 nm, 𝐹𝑢 = (0.66 ± 0.06) J/cm2; gold sample, for λ = 1064 nm, 𝐹𝑢 = (1.66 ± 0.09) J/cm2 and for λ = 532 nm, 𝐹𝑢 = (0.13 ± 0.03) J/cm2. It was shown that pulsed photoacoustic is very appropriate for the determination of metal laser ablation thresholds with the advantages that the sample does not require special treatment, nor does it have to be in a certain way, and the sensitivity is comparable or superior to other conventional techniques used. ; the process is monitored in real time, and amplification is not required as the photoacoustic signals have amplitudes on the order of volts and a good signal to noise ratio.
In this thesis work, the laser ablation thresholds of the copper, gold and silver metals were determined for two different wavelengths (532 nm and 1064 nm), using a pulsed Nd:YAG laser with pulse duration of the order of nanoseconds. The pulsed photoacoustic technique was used to record the photoacoustic signals produced due to the interaction of the metallic sample with the laser pulses. These signals were analyzed using standard correlation and changes in photoacoustic amplitude as laser fluence increased. The results indicate that the photoacoustic signals are very sensitive to physical changes experienced by a solid sample due to the interaction with laser pulses, being able to clearly differentiate the change from the thermoelastic regime to the ablation regime and consequently the ablation threshold. The experimental values obtained for the fluence of the laser ablation threshold (𝐹𝑢) were the following: copper sample, for λ = 1064 nm, 𝐹𝑢 = (1.71 ± 0.08) J/cm2 and for λ = 532 nm, 𝐹𝑢= (0.91 ± 0.11) J/cm2; silver sample, for λ = 1064 nm, 𝐹𝑢 = (1.15 ± 0.05) J/cm2 and for λ = 532 nm, 𝐹𝑢 = (0.66 ± 0.06) J/cm2; gold sample, for λ = 1064 nm, 𝐹𝑢 = (1.66 ± 0.09) J/cm2 and for λ = 532 nm, 𝐹𝑢 = (0.13 ± 0.03) J/cm2. It was shown that pulsed photoacoustic is very appropriate for the determination of metal laser ablation thresholds with the advantages that the sample does not require special treatment, nor does it have to be in a certain way, and the sensitivity is comparable or superior to other conventional techniques used. ; the process is monitored in real time, and amplification is not required as the photoacoustic signals have amplitudes on the order of volts and a good signal to noise ratio.
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Keywords
Fluencia láser, Fotoacústica pulsada, Umbral de ablación