The effect of parasitic elements of a laser on its modulation characteristic is investigated theoretically and experimentally. It is shown that this characteristic depends on the thickness d of the insulating dielectric film, differential resistance Rd, and length L of the laser resonator. For example, at d=0.15 μm, Rd = 9 Ω, and L = 300 μm, the upper modulation frequency at a level of —3 dB is 500 — 1500 MHz, and at d = 1.2 μm, Rd = 5 Ω, and L = 200 μm, it reaches 12 GHz.