Pulsed lasers are redefining the boundaries of how short and fast human-made creations can be. To fully exploit their potential, researchers needed to learn how to manipulate their parameters to tailor light pulses to specific needs. Such pulsed lasers can become frequency combs, when two of their parameters, the repetition frequency (frep) and the carrier-envelope offset frequency (fceo), are stabilized.
The spectrum of optical frequency combs is not continuous; instead, it consists of discrete lines spaced by the repetition frequency, with the first mode offset from zero by the carrier-envelope frequency. Unfortunately, both of these parameters can change during laser operation, leading to variations in the properties of the emitted pulses. To prevent this, stabilization is required.
In the article entitled „Direct electro-optic phase control for carrier-envelope offset frequency stabilization in solid-state lasers”, which has just been published in Optics Express we demonstrate a novel technique for fceo stabilization. For the first time we exploited the Pockels effect using an electro-optic modulator placed inside the laser cavity for adjusting fceo. This approach changes the refractive index of the crystal by applying a voltage to it, which in turn shifts the fceo. This method overcomes the limitations of pump modulation and increases the operational bandwidth, resulting in more stable pulse generation. We compared the novel approach with a standard fceo stabilization method based on pump modulation. We showed that using electro-optic phase control overcomes the limitations of pump modulation and increases the operational bandwidth, resulting in more stable pulse generation.