{'fraction_non_alphanumeric': 0.032758620689655175, 'fraction_numerical': 0.020689655172413793, 'mean_word_length': 4.928571428571429, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Highly efficient second-harmonic generation of intense femtosecond pulses with a significant effect of cubic nonlinearity

A highly efficient (73%) second-harmonic generation of femtosecond pulses in a 1-mm-thick KDP crystal at a fundamentalharmonic peak intensity of 2 TW cm-2 has been demonstrated experimentally. In a 0.5-mm-thick KDP crystal, a 50% efficiency has been reached at a peak intensity of 3.5 TW cm-2. We examine the key factors that limit the conversion efficiency and present numerical simulation results on further temporal compression of second-harmonic pulses.