Tham khảo tài liệu 'frontiers in guided wave optics and optoelectronics part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Advances in Femtosecond Micromachining and Inscription of Micro and Nano Photonic Devices 305 will not be covered here but may be found in references T. Sudmeyer 2008 S. Backus 1998 however differences in terms of the output pulses will be discussed. The wavelength ranges of the types of laser are determined by a number of factors. There are two main bands covered by the fibre lasers at 1030-1045nm and around 1550-1560nm. The two bands correspond to the dopant used in the lasers cavities. The conventional C-band erbium window is at 1530-1565nm and ytterbium sources operate at around 1030-1050nm S. B. Poole 1985 . There is a third much smaller group of fibre lasers operating at around 800nm. Bulk amplifiers and oscillators are also governed by the amplification material chosen. They typically use Ti Sapphire and ytterbium and as such commonly operate at wavelengths around 800nm and 1030-1050nm. The energy per pulse is a parameter to be considered in a similar way to the peak power. The pulse energy required will depend on both the material and the chosen application. Machining of a crystal for instance will typically require a much greater energy per pulse for example energies up to and above 80 Jcm-2 T. V. Kononenko et al. 2008 for natural diamond while for index change in PMMA energies above Jcm-2 A. Baum et al. 2007 cause permanent change. The energy per pulse of the types of laser are detailed in table 1. The oscillators typically have energies in the range of 1-100s nJ per pulse whereas the fibre lasers offer energies in the ụJ range and amplifier pulse energies typically fall in the mJ range. The choice of pulse energy for a given application is critical as most materials have a small window of energies between the desired effect say index change and damage. The other consideration is that to control the energy and other parameters incident on a sample is significantly easier when not having to operate at the extreme limits of attenuators or with .
