The bubble-assisted Liquid Hole Multiplier (LHM) is a novel concept for the combined detection of ionization electrons and scintillation photons in noble-liquid time projection chambers. It consists of a perforated electrode immersed in the noble liquid, with heating wires generating a stable bubble underneath. Radiation-inducted ionization electrons in the liquid drift into the electrodes holes and cross the liquid-vapor interface into the bubble where they induce electroluminescence (EL). The top surface of the electrode is optionally coated with a CsI photocathode; radiation-induced UV-scintillation photons extract photoelectrons that induce EL in a similar way. EL-photons recorded with an array of photosensors, e.g. SiPMs, provide event localization. We present the basic principles of the LHM and summarize the results obtained in LXe and LAr.
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