光电子学课件Lesson_3PPT课件

2020/10/13
Q.J. Zhang
3
Examples (Cont’d)
3. A 632.8nm He-Ne laser has a half-symmetric cavity. One mirror is flat and the other (output) mirror has a radius of curvature of 1m. The spacing between two mirrors is 0.25m. Determine the waist size, Rayleigh range and the divergence angle.
2. Determine whether or not the following mirror arrangements lead to stability:
1. (a) two mirrors with radii of curvature of 1.8m, separated by a distance of 2m.
2020/10/13
Q.J. Zhang
2
Examples (Cont’d)
2. An Argon laser cavity is constructed with a pair of mirrors having a 2 m radius of curvature, separated by a distance of 1.8m. Determine if the cavity is stable. If a 0.2 m focal length thin lens is mounted directly in front of the laser output mirror, where will it focus and what will be the focal spot size? The laser is operating at 514.5nm.
4. (d) two mirrors with radius of curvature of 0.5m, separated by a distance of 0.5m.
3. A Gaussian beam of wavelength 800nm is measured to have a wavefront curvature of 3m and is known to have a beam waist somewhere of 0.75mm. At that location, how far is the beam from its minimum?
2020/10/13
Q.J. Zhang
4
Examples (Cont’d)
4. Calculate the approximate length of a He-Ne laser that will oscillate in one longitudinal mode when the cavity resonance happens to coincide with the wavelength of maximum gain, but will oscillate in two modes when the cavity resonance is far from that wavelength. The fluorescence linewidth is 1500MHz. Calculate the maximum length of a temperature-stabilized laser that is designed to oscillate in only one longitudinal mode at precisely the center of the gain curve of the laser.
2. (b) one mirror with radius of curvature of 2m and the other with radius 3m, separated by a distance of 2.3m.
3. (c) one mirror with radius of curvature of 5m and the other with radius 3m, separated by a distance of 4m.
Review of Last Lesson
▪ Optical Amplification
• Stimulated Emission Transition Cross Section • Creation of Population Inversion • Laser Rate Equations
▪ Example: Ruby Laser ▪ Optical Resonator and Gaussian Beam
wenku.baidu.com
2020/10/13
Q.J. Zhang
1
Examples
1. Consider the propagation of a Gaussian beam in free space. Assume that the beam has a planar wavefront at z1=0. Determine the waist transformation formula for such a propagation to a location z that originated at z=z1=0.
2020/10/13
Q.J. Zhang
5
Homework
3/4/2004
1. Determine the ABCD matrix for a beam translated a distance d1, focused through a thin lens of focal length f1, and then translated a distance d2.