  A resonant photoacoustic cell intended for laser-spectroscopy gas sensing is
represented. This cell is a miniature imitation of a macro-scale banana-shaped
cell developed previously. The parameters, which specify the cavity shape, are
chosen so as not only to provide optimal cell operation at a selected acoustic
resonance but also to reduce substantially the cell sizes. A miniaturized
prototype cell (the volume of acoustic cavity of ~ 5 mm^3) adapted to the
narrow diffraction-limited beam of near-infrared laser is produced and examined
experimentally. The noise-associated measurement error and laser-initiated
signals are studied as functions of modulation frequency. The background signal
and the useful response to light absorption by the gas are analyzed in
measurements of absorption for ammonia in nitrogen flow with the help of a
pigtailed DFB laser diode oscillated near a wavelength of 1.53 um. The
performance of prototype operation at the second longitudinal acoustic
resonance (the resonance frequency of ~ 32.9 kHz, Q-factor of ~ 16.3) is
estimated. The noise-limited minimal detectable absorption normalized to
laser-beam power and detection bandwidth is ~ 8.07*10^(-8) cm^(-1) W Hz^(-1/2).
The amplitude of the background signal is equivalent to an absorption
coefficient of ~ 2.5*10^(-5) cm^(-1). Advantages and drawbacks of the cell
prototype are discussed. Despite low absorption-sensing performance, the
produced miniaturized cell prototype shows a good capability of gas-leak
detection.
