{'fraction_non_alphanumeric': 0.027522935779816515, 'fraction_numerical': 0.013344453711426188, 'mean_word_length': 4.555555555555555, '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}}
Micro-air cavity incorporated tapered-tip photonic crystal fiber based compact refractometer

We report a compact and robust micro air cavity (MAC) incorporated tip tapered photonic crystal fiber (PCF) based interferometer point probe for refractive index (RI) sensing. Two sections of PCF are spliced and tapered and the tapered collapsed section is cleaved to form a tip tapered PCF. One end of the PCF is spliced with a single mode fiber while the tapered tip of PCF is subjected to laser micromachining which results in the formation of a micro-groove at the tip. The laser micromachining enables the formation of micro-groove even on a roughly cleaved tapered section. The micro-groove is post processed using a fusion splicer in order to form a MAC at the tip which appears like a ‘ball-pen’. The presence of MAC helps in the formation of sharp interference pattern that can be used for precise monitoring of RI. Using this procedure, three probes are fabricated with varying parameters. The maximum RI sensitivity is found to be 158.41 nm RIU−1 with resolution being 6.31 × 10−5 RIU. Further, the sensitivity of the probe to variation in environmental temperature is found to be 29.14 pm/ ∘C.