Oscillators in the GHz frequency range are key building blocks for telecommunication and positioning applications. Operating directly in the GHz while keeping high frequency stability and compactness, is still an up-to-date challenge. Recently, optomechanical crystals have demonstrated GHz frequency modes, thus gathering prerequisite features for using them as oscillators. Here we report on the demonstration, in ambient atmospheric conditions, of an optomechanical oscillator designed with an original concept based on bichromaticity. This oscillator is made of InGaP, a low loss and TPA-free piezoelectric material which makes it valuable for optomechanics. Self-sustained oscillations directly at 3 GHz are routinely achieved with a low optical power threshold of 40 µW and short-term linewidth narrowed down to 100 Hz in agreement with phase noise measurements (-110 dBc/Hz at 1 MHz from the carrier) for free running optomechanical oscillators.

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