We report (theory, experimental check) an improved approach for generation of a tunable, subnanosecond pulse (0.1-0.4 ns), based on a single pulsation ("spike") separation from the transient oscillations in a dye laser with active mirror (AMIR). A pumping by 20-50 ns pulses from Q-switched Nd:YAG laser is considered. The separation is in original, two-spectral selective channels cavity, where the forced by AMIR quenched generation at one of the wavelength stops initially started spiking generation at the other wavelength after the first spike development. The AMIR quickly starts the quenching generation at a precisely controlled moment and with necessary intensity thus assuring the desired separation. An advantage is a high reproducibility of the separation for high (∼250%) pump power fluctuations combined with tuning in large range (∼20 nm). To obtain such an operation we form ∼1 ns leading front pump pulse by electrooptical temporal cutting of the input pump pulse and use an optical delay line. This increases also a few times the power in the separated spike (to be ∼100 kW). Our approach widens the combinations of lasers for effective applications of spike separation technique (dye lasers excited by Q-switched solid-state or Cu-vapor lasers).
We show via detailed experimental investigations that the single pulse from Nd:YAG and Nd:Glass lasers (wavelength 1.06 μm, free lasing operation) are suitable for efficient cleaning initial carious lesions (1 - 3 mm in diameter) on tooth enamel. The cleaning is in combination with tooth preparation for final healing procedures – formation of desired hole and antibacterial cleaning. The measured heating of the tooth chamber is in acceptable limits and crack formation is avoided. The investigation includes laser irradiation with single pulses of energy of ~2 to 5 J, energy density of ~50 to 130 J/cm2 and pulse duration of ~500 ns – 2 ms. In further development of the topic, as a second part of this article, we propose algorithm for application of the discussed cleaning.
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