{'fraction_non_alphanumeric': 0.03398058252427184, 'fraction_numerical': 0.03398058252427184, 'mean_word_length': 4.427631578947368, '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}}
Ring solid-state Raman laser at 1538 nm

A ring KG(WO4)2 (KGW) Raman laser converting the multimode radiation of a Q-switched Nd:KGW pump laser oscillating on the 4F3/2 → 4I13/2 transition into the first Stokes at 1538 nm has been demonstrated for the first time as far as we know. With a 22-mm crystal in each section of a three-mirror ring cavity, the Raman laser generates eye-safe radiation of energy ∼ 7 mJ and duration ∼ 15 ns. The beam divergence does not exceed 4.7 mrad. The conversion efficiency reaches ∼ 20%, and the slope efficiency is ∼ 42%. Upon elimination of the parasitic Stokes radiation induced by the Fresnel reflection from the AR-coated crystal ends in the opposite direction along the path of the pump beam the Raman laser provides unidirectional oscillation without using auxiliary optical elements.