Compact laser-spectroscopy gas detectors capable of analyzing the traces of chemical compounds in gas samples of small volume are in strong demand of applications, which need reliable substance-selective high-sensitivity analysis of gas media. Such gas detectors can be used as leak detectors for localizing explosive, toxic or narcotic substances in public accommodations. The detectors may be applicable in Life Sciences for analysis of weak gas flows emitted by small-scale biological samples: small animals and plants, their organs, tissue pieces or microscopic objects down to individual cells.The demand can be met by making of a gas detector based on a widely-tunable mid-infrared semiconductor laser and a novel miniaturized resonant photoacoustic cell. The design of this cell is optimized so as to reduce essentially the cell sizes and, simultaneously, to provide the high-performance cell operation at a selected acoustic resonance. For the properly optimized resonant cell, the window background (a signal arisen in the cell due to absorption and reflection of light beam by the cell windows) is absent at any modulation regime. Such a background-free cell is applicable to detection of any infrared-active compound whatever the spectral features of the compound. This cell design can be easily adapted to any laser-beam diameter and modulation frequency. Despite the essentially reduced sizes, the miniaturized cell is comparable to the well-developed macro-scale cells in the performance.The project goal is to integrate this novel miniaturized cell with a mid-infrared external-cavity quantum cascade laser into a compact photoacoustic gas detector and demonstrate the detector capabilities in experiments. Several detector prototypes, which answer to diverse applications, will be created and tested. All principal components (laser chip, laser-cavity design, photoacoustic cell, etc) of the prototypes will be fitted to each other for providing the best gas-detection performance.