A Novel Strategy in Quartz‑Enhanced Spectroscopic Sensing Based on a Double‑Ended Quartz Tuning Fork.

To overcome the limitations of the standard single‑ended quartz tuning fork (QTF) in quartz‑enhanced laser spectroscopy, this work introduces a novel double-ended QTF (DE-QTF) design as a new sensing strategy. It offers three key advantages: (1) confined acoustic interaction minimizes energy loss while concentrated stress increases piezoelectric charge; (2) wide central clearance and extended mid-section acoustic coverage enable multibeam excitation and integration of acoustic microresonators (AmRs), enhancing quartz-enhanced photoacoustic spectroscopy (QEPAS) sensitivity; and (3) strengthened mechanical constraints on thermal expansion convert more laser energy into useful stress, boosting the light-induced thermoelastic spectroscopy (LITES) signal. Experimentally, in QEPAS and DE-QTF achieved a 3.1-fold higher signal compared to a standard QTF. The multipass and AmRs configurations amplified signals over 429 times compared to the single-excited DE-QTF, yielding a 12.58 ppb minimum detection limit (MDL) for acetylene. In LITES, it provided a 6.9-fold signal improvement. This work provides a new pathway to break the sensitivity bottleneck in trace gas detection via QTF structural innovation.