A novel new design for an 8-pass multipass Titanium doped sapphire femtosecond amplifier (MPA) is studied. Ultrafast amplifiers based on the chirped pulse amplification (CPA) technique have been widely used to amplify the output pulses of Kerr lens mode locked (KLM) Ti:sapphire lasers from the nanojoule to the microjoule level. The system presented here also takes advantage of CPA to reduce the peak power and thus the potential damage to optical components from self-focusing. The amplifier scheme is based on a single curved mirror and a Brewster cut Ti:sapphire laser rod. Optical excitation of the Ti:sapphire gain medium is achieved by pumping with a Q-switched and frequency doubled Nd:YLF laser at 527 nm. The rear face of the gain crystal is coated to form a high reflector for both the pumping wavelength (490-550 nm) and the amplified seed pulse (740-860 nm). In this configuration the gain crystal itself acts as a second mirror, reducing the size of the amplifier and allowing for the most effective use of the pumping energy. By employing a Brewster cut lasing crystal the amount of active gain material can be adjusted for maximum gain. The advantages of this approach, compared to traditional two curved mirror MPA designs, are the reduced foot print and the ability to easily adjust the amount of gain material. At the same time the system retains the low amplified spontaneous emission (ASE) and temporally clean output pulse characteristic of MPA systems.
Spectral Interferometry for Direct Electric Field Reconstruction (SPIDER) is one of several methods for characterizing ultrashort optical pulses. SPIDER allows for the measure of the pulse duration, but also allows the extraction of the spectral phase from a femtosecond pulse. Advances in femtosecond laser development in recent years has led to commercially available femtosecond pulsed laser systems with pulse lengths of less than 10~fs. New lasing materials and advances in fiber laser technology has allowed manufacturers to produce femtosecond pulsed lasers that operate at wavelengths outside the traditional 800~nm range of Ti:sapphire. The need for commercially available pulse characterization instruments is clear. SPIDER based spectral phase measurement systems have been adapted to facilitate the advances in femtosecond laser technology.