Three samples of vertical-cavity surface-emitting laser diodes (VCSEL) designed by Vixar Inc. are studied. The central wavelength of the lasers is about 894.6 nm (D
line of cesium). The threshold currents of laser generation are measured. The laser injection current is modulated at microwave frequency about 4.596 GHz that is a half of Cs ground- state hyperfine splitting frequency. Dependence of phase modulation index of laser radiation on microwave power is determined. The observed deviations of laser properties from sample to sample are compared to other works. A particular attention is paid to observation of additional optical frequencies (ghost modes) in the laser spectra, having the same polarization as the main spectral sidebands. This effect can harm metrological characteristics of various quantum devices where VSCELs are nowadays used. The optimal regimes of laser performance to avoid generation of the ghost modes are found. Also, asymmetry of the spectra caused by a residual amplitude modulation is measured. The results can be important for creation of various VCSEL-based quantum devices (atomic clocks, magnetometers).