Features of PbSe chalcogenide films modified by irradiating with nanosecond laser pulses in various modes of treatment in an oxygen-free environment are studied. Changes in optical properties of the films after laser irradiation and modification of their structure in a nitrogen atmosphere were examined. It is shown that the presence of a nitrogen medium does not significantly affect the optical characteristics of the films obtained as a result of laser modification with an incident radiation wavelength of 1064 nm. These results indicate that the use of an oxygen-free medium in the modifying sensitive detectors is not needed. The obtained experimental data are the basis for expanding the knowledge on laser modification of the structure of semiconductor chalcogenide films and revealing the relationship between the optical characteristics of the material before and after laser exposure. The results of the study can be used in applied problems related to the manufacture of photodetectors in devices for gas and bioanalysis, photovoltaics, and optoelectronics.