{'fraction_non_alphanumeric': 0.02169811320754717, 'fraction_numerical': 0.01509433962264151, 'mean_word_length': 5.1686046511627906, '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}}
Tunable diode laser based biphoton source for quantum spectroscopy

Photon pairs generated by spontaneous parametric down-conversion (SPDC) are essential for a number of quantum-optics experiments. By utilizing periodically poled (PP) waveguide structures high flux rates of biphotons in one transversal mode can be obtained. The biphoton source presented here is explicitly designed for quantum spectroscopic application and is based on a frequency doubled broad area external cavity diode laser (BA-ECDL) that pumps SPDC inside a PPLN waveguide crystal. The frequency doubled BA-ECDL delivers up to 18 mW of diffraction limited light, tunable around 488 nm [1]. Inside the waveguide crystal one of the 488 nm pump photons can disintegrate into two photons around 976 nm. The generated SPDC light is coupled into a fiber with an integrated 50:50 beam splitter that splits signal and idler into the two fiber branches with avalanche photodiodes (APD) as detectors. A time correlated single photon counting device has been used for the correlation measurements.