The method of chirped pulse amplification(CPA) has made possible a high-peak power laser over 1 terawatt(TW) in a university lab. The CPA Nd:glass laser system is composed of a additive pulse mode-locked Nd:YLF laser, a four-pass grating stretcher, a ring regenerative Nd:glass amplifier and two Nd:phosphate glass rod amplifiers and a compressor with two gratings. The Nd:YLF laser oscillator generates mode-locked pulse of 2 ps. The pulse from Nd:YLF laser is stretched to almost 230 ps by a four-pass grating stretcher. The output pulse from a stretcher was amplified in a ring regenerative amplifier, two Nd:glass amplifiers of diameter's 8 mm and 20 mm. In a single pass scheme, the maximum energy from the 20 mm Nd:glass amplifier was 1.2 J at 4.5 kJ pumping energy and the maximum energy in a double pass scheme was 2.5 J at 2.8 kJ pumping energy. The measured energy in a double pass scheme was larger than that in a single pass scheme, but spatial beam profile in a single pass scheme was more uniform than that in a double pass scheme.
The spectral and temporal profiles of an amplified pulse were measured. The central wavelength of an Nd:YLF laser oscillator (1053nm) is not identical with that of an Nd:phosphate glass amplifier(1054nm). As a result, the measured spectral profile of the amplified pulse was different from that of an Nd:YLF laser oscillator. The spectrum of an oscillator pulse became broader and the central position of the spectrum shifted to the 1054nm during amplification.
The pulse compressor consists of two 1200gr/mm gratings and is double-parallel with a distance of 13.8m. The duration of compressed pulse is measured by a single-shot autocorrelator. The single-shot autocorrelator utilizes KTP as a second-harmonic generation element and a charge-coupled device as a detector. The measured pulse duration was shorter than that of the Nd:YLF oscillator. A further optimization of the CPA Nd:glass laser system will be pursued to achieve an output over 1 TW.
