High Power Laser Science and Engineering, Volume. 9, Issue 2, 02000e12(2021)
Multi-octave-spanning supercontinuum generation through high-energy laser filaments in YAG and ZnSe pumped by a 2.4 μm femtosecond Cr:ZnSe laser
Fig. 1. Schematic diagram of experimental setups. (a) Femtosecond Cr:ZnSe CPA laser, composed of mode-locked Cr:ZnS laser oscillator, Cr:ZnSe regenerative amplifier, and stretcher/compressor unit. The dotted lines indicate the pump beam while solid lines, 2.4 μm beams. (b) Setup for laser filamentation in a solid. The arrows for spatial characterization indicate the far-field (left) and near-field (right) images of the laser filament, respectively. The spectral characterization is performed using multiple spectrometers. ND, neutral density filter; L1,
Fig. 2. Dispersion curves of YAG and ZnSe versus wavelength. The dotted line shows the pump wavelength of 2.4 μm.
Fig. 3. Laser filamentation and SCG in YAG: (a) a laser filament in a 6-mm-long YAG sample; (b) the visible spectrum (linear scale), where the inset is the corresponding far-field beam profile in red and green (true color); and (c) SC spectrum (solid) at 15 μJ, 2.4 μm input (dotted) in logarithmic scale.
Fig. 4. Laser filamentation and SCG in ZnSe: (a) a laser filament in a 6-mm-long polycrystalline ZnSe sample; (b) the visible spectrum (linear scale) showing FHG without SCG, where the inset is the corresponding far-field beam profile in yellow; (c) SC spectrum (solid) at 15 μJ, 2.4 μm input (dashed) in logarithmic scale. The absorption peak at ~4.3 μm is from atmospheric CO2. The well-defined SHG peak is observed at ~1.2 μm.
Fig. 5. Spectral broadening of incident wavelength of 2.4 μm in a 6-mm-long (a) YAG and (b) ZnSe versus energy and its near-field image. The input pulse energies are 10, 25, 50, and 100 μJ. The logarithmic scale of intensity spectra is used to highlight the fine spectral features. Near-field intensity distributions with the magnification of ~2 at the output surface of the YAG (right column in (a)) and ZnSe (right column in (b)), as measured in the single and multiple filamentation regimes with the variation of input energy. The white scale bars correspond to 0.4 mm in length.
Fig. 6. UPPE numerical simulations of SCG in YAG. (a) Simulated on-axis (
Fig. 7. Numerical simulations of SCG in ZnSe. (a) Simulated on-axis (
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Sang-Hoon Nam, Garima C. Nagar, Dennis Dempsey, Ondřej Novák, Bonggu Shim, Kyung-Han Hong. Multi-octave-spanning supercontinuum generation through high-energy laser filaments in YAG and ZnSe pumped by a 2.4 μm femtosecond Cr:ZnSe laser[J]. High Power Laser Science and Engineering, 2021, 9(2): 02000e12
Category: Research Articles
Received: Oct. 23, 2020
Accepted: Jan. 5, 2021
Published Online: Apr. 2, 2021
The Author Email: Kyung-Han Hong (kyunghan@mit.edu)