研究目的
Investigating the nonlinear laser-mater interaction in silicon and Nd:Y3Al5O12 (Nd:YAG) crystals using unidirectional pulse propagation equation (UPPE) modeling and experimental validation.
研究成果
An extensive UPPE simulation was performed to analyze the evolution of pulse energy, fluence, plasma generation, and beam waist along the propagation direction inside silicon and Nd:YAG. The modeling shows that, with increasing input pulse energy, the peak fluence increases and shifts towards the direction from which the beam is coming. Furthermore, the focal volume broadens along the pulse propagation direction. These observations are in good agreement with already reported experimental results in silicon and our experimental observations for Nd:YAG. A minimum (mean) propagation loss of 0.21 ± 0.06 dB/cm is achieved for waveguide configuration written at a scanning speed of 10 μm/s, pulse energy of 3 μJ, and track spacing of 30 μm.
研究不足
The study is limited to the use of a specific wavelength (515 nm) for waveguide writing in Nd:YAG crystals, and the effects of other wavelengths are not explored. Additionally, the study does not investigate the impact of varying the repetition rate of the laser pulses on the waveguide properties.
1：Experimental Design and Method Selection:
UPPE-based numerical modeling is used to predict the spot size and peak fluence evolution of a single pulse in both longitudinal and transverse directions, using different laser parameters and focusing conditions.
2：Sample Selection and Data Sources:
Nd:YAG crystals (
3：5 mm × 5 mm × 10 mm), cut along the crystal axes, are used for waveguide fabrication. List of Experimental Equipment and Materials:
A 300 fs, 515 nm ytterbium fiber laser (Satsuma HP3, Amplitude Systèmes) with a repetition rate of 1 kHz is used. The laser beam is focused into the sample by a 20× microscope objective (Nikon) with an NA of
4：Experimental Procedures and Operational Workflow:
Type II waveguides were written with various configurations. During the writing process, the sample was moved at a given velocity along the X direction by a motorized translation stage. Different pairs of tracks with separation varying from 20 μm to 30 μm were inscribed with pulse energies ranging from 2 μJ to 4 μJ.
5：Data Analysis Methods:
The propagation loss (LP) is obtained by subtracting coupling loss (LC) and Fresnel reflection loss (LR) from the measured insertion loss (LI). The coupling loss between the input beam and the waveguide is determined by the mode field overlap integral.
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