Gas-filled Hollow Core Photonic Cristal Fibres (HCPCF) or Photonic MicroCell (PMC)  has proven to offer an outstanding gas-cell for laser metrology and spectroscopy applications. Sub-Doppler spectral features, generated via electromagnetically induced transparency (EIT) or saturated absorption (SA), have been generated in molecular gases despite the weak strength of their optical transitions [1-4], and an optical frequency reference with excellent accuracy has been demonstrated . So far, the reported stand-alone PMCs are either made by hermetically splicing the HCPCF tips to an all-solid optical fibre [1,2] or by encapsulating them to a glass cell . All these techniques show limitations. For example, the splicing based all-fibre PMC technique is not adapted to all fibres as it requires matching the outer-diameter and/or mode-field-diameters of the two fibres. Also the use of fibre tapering to reduce this mismatch  remains too cumbersome for the obtained splice-loss figures, which are >2 dB and exhibit asymmetric loss.
© 2019 IEEEPDF Article