Hanoi University of Science and Technology School of Mechanical Engineering KỸ THUẬT LASER Vũ Thanh Tùng 1 Chapter 1: Introduction 2 Chapter 1: Introduction 3 Chapter 1: Introduction 4 Chapter 1: Introduction 5 Chapter 1: Introduction 6 Chapter 2: Light Source 7 Chapter 2: Light Source Fig 2.1:phân loại laser theo độ nguy hiểm 8 Chapter 2: Light Source Fig2.2 9 Chapter 2: Light Source 10 Chapter 2: Light Source 11 Chapter 2: Light Source 12 Chapter 2: Light Source Fig 2.3 13 Chapter 2: Light Source HeNe 0/0 Ar++ Rubi Nd 1 0,8 Pho truyen qua cua mat 0,6 0,4 Pho hap thu cua vong mac 0,2 Buoc song  500 1000 1500 nm Đồ thị 2.1 phổ hấp thụ và truyền qua của laser 14 Chapter 2: Light Source do phan xa 1 A 0,8 0,6 0,4 B 0,2 Buoc song  500 1000 1500 nm Fig 2.2 : độ phản xạ phụ thuộc vào bước sóng 15 Chapter 2: Light Source 2.1 Wavelength Fig 2.1.1 Dải phổ 16 Chapter 2: Light Source 2.1 Wavelength Fig 2.1.2 17 Chapter 2: Light Source 2.1 Wavelength Laser Wavelength Tuning Fig 2.1.3 Laser tuning using the wavelength dispersive behavior of a diffraction grating or a prism (left). Use ò a birefringent filter as a wavelength-selective element (right) 18 Chapter 2: Light Source 2.1 Wavelength Laser Wavelength Tuning When a weak optical field interacts with a material, it creates a polarization in the material made up of many electric dipoles. The strength of this polarization is linearly proportional to the magnitude of the optical field and the dipoles re-radiate light with the same frequency of the optical field. This is the regime of linear optics. When an intense optical field encounters a material, the polarization no longer responds linearly to the applied field. Instead, it becomes quadratically-dependent (or even higher order) on the field. This nonlinear dependence on the optical field is why intense light sources are required for nonlinear optics and why experimental observation of NLO ph