Cairo University

MTPR Journal

 

STORAGE of FEMTOSECOND LASER PULSES in AN OPTICAL TRAP

2016-12-17
Abdullah Shehata1, Mohamed Yassien1, Mona Ali1, Tarek Mohamed1, Reinhold Schuch2
1Physics Department, Faculty of Science, Beni-Suef University, BeniSuef 62511, Egypt
2Physics Department, Stockholm University, AlbaNova, 10691 Stockholm, Sweden

Vol./Issue: 16 , id: 195

An optical trap for storing femtosecond laser pulses was investigated theoretically to enhance the interaction efficiency with optically thin targets. The optical trap consists of an electro-optical switch, high reflective mirrors and a focusing system. The efficiency of the optical trap is strongly depends on the optical losses from the optical elements of the trap [1]. To compensate the optical losses, Ti: Sapphire crystal as an amplifying medium was implemented in the optical trap. It has high saturation fluence ≈ 0.9 Jcm-2, and upper state lifetime of 3.2 μs. These parameters do not cause a quick extraction of the stored energy from the amplifying medium and keep the intensity of stored laser pulse constant over 3.2 μs [2]. In the theoretical investigations, we had studied the trapping of femtosecond laser pulses of wavelength 800 nm, 1mJ energy per pulse, 10 Hz repetition rate and with different pulse duration times. Due to the propagation of these laser pulses through the optical trap both of phase self modulation and group velocity dispersion, introduce large broadening for the laser pulses that have the initial duration time <500 fs. To compensate this broadening, chirped mirror with suitable properties can be used. Power consideration showed an increase in the average power of the laser system when the optical trap that includes a Ti: Sapphire by a factor of 165 times compared to single passage of the laser pulse. Also the laser pulse could be stored in the optical trap for 4 μs. Comparison between the available experimental data and our theoretical data showed a good agreement.