Use of a PVDF pyroelettric sensor for beam mapping and profiling of a mid-infrared diode laser

A four-quadrant PVDF position sensor, originally designed for the alignment of mid-IR laser diodes beams, was also used for mapping and profiling the beam of a diode laser emitting few ?W at 5.8 ?m, by masking one quadrant with a 1 mm diameter pinhole or a 100 ?m width slit. This diagnostic system was used to optimize the laser collimating optics, determining a significant improvement in the spatial quality of the output beam, evaluated by means of the M2 propagation factor. Since the laser diode modulation waveform required to optimize the pyroelectric detector responsivity is a fixed frequency square wave, quite different from that used in the normal spectroscopic application of the IR diodes, care was taken to have the same single-mode emission in the wavelength range of interest. The system was intended as a diagnostic and optimization tool for spectroscopic systems applied to environmental monitoring, but it may be used as a low cost device for the characterization of low power laser beams