LECTURE 25 Optical devices

LECTURE 25 Optical devices - SUMMARY FROM LAST CLASS...

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Dr. P. Lucas U of A MSE 110 Optical devices SUMMARY FROM LAST CLASS A light ray proceeding from one medium to another medium of different refractive index diverge, change direction. This phenomenon is called refraction. The angle of the incident beam and the refracted beam are related to the refractive index of the two mediums according to: A beam proceeding from a high to a low n medium with an incident angle larger than the critical angle will be reflected back into the incident medium. This is known as total internal reflection. Light is confined in a fiber core of index n 1 larger than the cladding n 2 by total internal reflection. The index is modified by changing the chemical composition of the core and cladding glass. The core is made of high purity SiO 2 to minimize the attenuation due to impurities such as water and metals absorption. The attenuation of SiO 2 fibers is minimum at the telecom wavelength 1.3 μ m and 1.55 μ m. 2 1 2 1 sin sin θθ n n = 2 1 sin n n c = θ
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Dr. P. Lucas U of A MSE 110 LASER OPTICAL DEVICES Light Amplification Emission Stimulated by Radiation of
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U of A MSE 110 Stimulated emission OPTICAL DEVICES When a photon reaches an atom in its fundamental state, it is absorbed to promote an electron into a higher energy level. If an atom is already in an excited state, an incident photon can stimulate a transition back to the fundamental electronic state. The incident photon is not absorbed and the transition produces a
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LECTURE 25 Optical devices - SUMMARY FROM LAST CLASS...

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