Compact tunable 80 MHz repetition rate vacuum ultraviolet light source up to 10 eV: intracavity high harmonic generation by nonlinear reflection on a AlN nanofilm in a mode locked Ti:sapphire oscillator

The 532 nm solid-state laser, generated by means of second-harmonic generation (SHG) technology, has become one of the most extensively used lasers in various applications today. In the tradition scheme, the most prevalent SHG crystal of the 532 nm solid-state is lithium borate (LBO), continues to exhibit insufficient angle robustness and SHG efficiency. In an attempt to overcome these limitations and achieve a SHG crystal with better angle robustness, the research commences with a comprehensive theoretical analysis of angle robustness. On this basis, it proceeds to design the structure of a chirped periodically poled lithium niobate (CPPLN) crystal, taking into account the desired properties for improved performance. The study then implements theoretical simulations and experimental tests to validate the effectiveness of the designed crystal. The simulation results corroborate the superior angle robustness of the CPPLN crystal. Within the range of -3° to +3°, the designed CPPLN crystal exhibits a maximum SHG efficiency of 0.80% and a minimum of 0.51%, which indicates that the SHG efficiency of this crystal in this range can be maintained at 60% of the maximum efficiency. The experimental results show that the SHG efficiency can be more than 11 times that of LBO crystal. Moreover, the study reveals that the half-width of the actual SHG efficiency about the incident angle of the designed CPPLN crystal can exceed 6°, indicating its exceptional tolerance to variations in the incident angle. Furthermore, the output spot of the SHG light generated by the designed CPPLN crystal exhibits a standard Gaussian profile, which remains virtually unaffected by the incident angle. In conclusion, the findings of this research highlight the CPPLN crystal as a promising alternative to LBO, boasting a markedly higher SHG efficiency and better angle robustness. These superior characteristics make the CPPLN crystal a highly attractive candidate for use in a wide array of laser applications.

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Design and angular robustness test of chirped periodically poled lithium niobate crystal for 1064 nm second-harmonic generation experiment

Liu,

Su,

Liu

et al. 2024

Acta Phys. Sin.

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Ultrasonic phase changes carry critical information regarding tissue structures, and phase weighting can enhance the sharpness of ultrasonic images. Addressed here are challenges, such as the faint scattering echoes from folds, substantial noise interference, and the lengthy processing time involved with time-domain corrected imaging. This paper proposes a frequency-domain coherent imaging method based on the coherence factor of the phase imaginary part. Firstly, the phase information in the wavefield signal is extracted, and then the phase imaginary part matrix is extracted using Circular Statistics. Subsequent construction of the Phase Imaginary Coherence Factor (PICF) involves multiplying this matrix with the original frequency-domain matrix used in Phase Shift Migration (PSM) imaging. By incorporating the PICF into phase migration imaging and adjusting the PICF of the migrating wavefield at each layer, fibre texture information can be efficiently recovered by frequency domain signal multiplication. This paper applied the technique to carbon-glass fiber composite boards with an 18mm thickness. The experimental outcomes reveal that without PICF weighting, phase migration imaging loses the fiber layout information beyond a 10mm depth and fails to detect deeper region defects. PICF-weighted PSM imaging identifies three fibre folds with depths of 11 mm, 15 mm and 16 mm, respectively. This approach improves the imaging clarity and textural detail of the fold defects and maintains the detection error of the fold angles to about 10%. The imaging time is only 1.5 seconds, which is at least 8.67 times more computationally efficient than time-domain TFM imaging.

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Compact tunable 80 MHz repetition rate vacuum ultraviolet light source up to 10 eV: intracavity high harmonic generation by nonlinear reflection on a AlN nanofilm in a mode locked Ti:sapphire oscillator

Cited by 3 publications

References 61 publications

High Harmonic Generation - an encyclopedia article

High Harmonic Generation - an encyclopedia article

Design and angle robustness test of chirped periodically poled lithium niobate crystal for 1064nm SHG experiment

Design and angular robustness test of chirped periodically poled lithium niobate crystal for 1064 nm second-harmonic generation experiment

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