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The development of laser industry and the increase in the intensity of laser radiation make the problem of protecting the vision organs and photosensitive sensors from high-intensity laser radiation more relevant. This paper presents the results for optical characteristics of phthalocyanine J-type dimeric complexes of Mg (phtMg) dissolved in dimethylformamide (DMF). Coherent Chameleon Ultra laser system was used as a source of laser radiation. The pulse duration was 140 fs, the pulse repetition rate was 80 MHz, and the wavelength was 810 nm. The studied solution didn’t exhibit nonlinear absorption properties (in contrast to the case of exposure by nanosecond radiation); the sample transmission remained unchanged with the increase in the intensity of the incident radiation. However, with the increase in the radiation power above 20 mW, an expansion of the beam was observed with the formation of a diffraction rings pattern due to spatial self-phase modulation induced by nonlinear refraction. The expansion of the laser beam allows the intensity of the laser radiation to be reduced by increasing the beam radius. Moreover, the addition of a diaphragm to the optical scheme, which "cuts off" a part of the incident radiation with an increase in the beam radius, makes it possible to reduce the radiation power getting in the sensor. This makes phthalocyanine complexes of Mg dissolved in DMF a promising material for use not only as a limiter of femtosecond pulsed radiation, but also as a nonlinear optical switcher for signal control in optical communication systems.