{'fraction_non_alphanumeric': 0.020353982300884955, 'fraction_numerical': 0.007964601769911504, 'mean_word_length': 4.741116751269035, '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}}
Characteristics of Alexandrite Lasers In Q-Switched And Tuned Operations

Alexandrite is a laser crystal which is unique in that it is broadly tunable, is four-level, and has a long storage time making Q-switched operation possible. In addition the crystal is surpassed only by ruby in desirable strength and thermal properties of all practical laser crystals. A simple four-level model that describes the laser operation in alexandrite is presented. The terminal laser level in this model is a set of vibrational states well above the ground state. The initial laser level is a level 800 cm-1 above a long-lived storage level and in thermal equilibrium with it. Experimental results of Q-switched operation and tuned long pulse operation are presented, both as a function of temperature. In Q-switched operation, pulsewidths from 70 ns to 300 ns have been measured and laser efficiency increases with temperature. In tuned operation, the increase in gain with temperature is accompanied by a shift of the tuning curve to the red. Both observations are consistent with the simple model. Some laser design parameters are discussed.