Ministry of Higher Education and Scientific Research University of Baghdad – College of Science Department of Physics FUNDAMENTALS OF PHOTONICS Dr. Abdullah m. suhail PH.D. postgraduate Qahtan G. Al-zaidi ﻗــــﺤﻄﺎن آﺎﻃــــــــﻊ اﻟﺰﻳــــــــﺪي دآﺘـــــــــــــﻮراﻩ ـــ ﻓﻴﺰﻳـــــــــﺎء January 29, 2008Fundamentals of Photonics Page 1 of 4 Wednesday, March 05, 2008 Baghdad University – College of Science – Department of Physics –Qahtan G. Al-zaidi, mobile: +009647702981421
Q1: In case of He‐Ne laser working in your laboratory, the red line of 632.8 is transmitted from the 3S2 to 2P4 state as shown in the spectrum figure. The pressure is 10 torr and the distance between the electrodes is 20 cm. Determine the following: 1. The operational voltage 2. The small signal gain coefficient 3. The required pumping rate For Helium – Neon laser, the following data can both be extracted from the energy – leveldiagram and the literature: The spontaneous lifetime . 0.7 The transition line width ∆ 1.5 The transition cross section 1 10 I. The operational voltage for laboratory He‐Ne laser is ℓ Where: 26.6 .Thus: 26.6 20 10 5320 5.32 II. The small signal gain coefficient . . 4 . . Here, . . Where: . ln ln 0.07615 ℓ . Therefore, the threshold population inversion would be: 0.07615 . 7.6148 10 1 10 The small signal gain coefficient . 4 . 1 10 4 7.6148 10 0.30459 .III. The required pumping rate . 0.07615 1.0878 10 · 0.7 10 1 10 Q2: For semiconductor laser the injected carrier concentration at balance between emission and absorption Δ 1.25 10 . For ∆ the injected carrier concentration near the operating point is equal to ∆ 1.4 ∆ and the absorption coefficient 600 . Find the peak gain coefficient of such laser. If the crystal length 350 , find the total gain. Fundamentals of Photonics Page 2 of 4 Wednesday, March 05, 2008 Baghdad University – College of Science – Department of Physics –Qahtan G. Al-zaidi, mobile: +009647702981421
Filename: Photonics FAQ final with colored logo Directory: E:Surface Plasmon Polaritonword documents Template: C:Documents and SettingsLana & JanetApplication DataMicrosoftTemplatesNormal.dotm Title: Subject: Author: Lana Keywords: Comments: Creation Date: 3/4/2008 11:23:00 PM Change Number: 4 Last Saved On: 3/5/2008 6:00:00 PM Last Saved By: lanajanet Total Editing Time: 5 Minutes Last Printed On: 3/5/2008 6:02:00 PM As of Last Complete Printing Number of Pages: 4 Number of Words: 915 approx. Number of Characters: 5,221 approx.