Research On The Novel Dispersion Compen-sation Mirror In Ultrafast Laser System

Dispersive mirrors (DMs) are indispensable devices in almost all femtosecond laser systems nowadays to control dispersion. With the fast development of femosecond laser, DMs have become a research focus in the filed of optical thin film.In this paper, we mainly focus on the research of double chirped mirror, chirped mirror pair and high third-order dispersion compensation mirror. According to different dispersion compensation requirements of the ultra-fast laser system, we designed and manufactured different types of dispersion compensation mirrors. We applied these mirrors in the ultra-fast laser systems and obtained good experiment results. The main contents are arranged as follows:1. Investigated and determined the technique parameters of the home-built ion beam sputtering (IBS) system. We fabricated a short-pass and a band-pass filter using our IBS and quartz crystal was used to control the thickness of the thin film during the depositing process. An excellent agreement between the measured and calculated transmittance of the filters is achieved, indicating our good control precision of the coating thickness.2. According to dispersion compensation requirements of the Ti:sapphire femtosecond laser system, a double-chirped mirror pair with a reflectivity more than 99.5% and an average group delay dispersion (GDD) of-40fs2 with residual ripples less than 20fs2 in the wavelength range of 600nm-1000nm is demonstrated and manufactured by IBS technology. The actual reflectivity and GDD of such a mirror pair were measured by a spectrophotometer and a home-made white light interferometer system. The measured results were well consistent with the designed ones. Use of these mirrors in the prism-less Ti:sapphire femtosecond laser system leads to 14.5fs pulses that were generated directly from the system.3. The dispersive mirrors with a third order dispersion (TOD) of about-10000fs3 at the wavelength of 1040nm and a compensation bandwidth of 20nm are designed and fabricated with IBS technique. A good agreement between the measured and calculated group delay dispersion (GDD) and TOD of the mirror is achieved. These mirrors are employed in a Yb-doped femtosecond nonlinear amplification fiber laser system to compensate the residual TOD in the system. We show that after TOD compensation, the system outputs 44fs laser pulses with little wing at 26.6W output average power and 531nJ pulse energy, corresponding to 10.8MW peak power. This simple and effective DM-based TOD compensator shows a promising potential in fiber optical amplification system.