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Development of broadband Er-doped fibersource PHYS 492 Senior Project by Hasan Esat KONDAKÇI Department of Physics, Bilkent University, Bilkent, Ankara Outline Introduction Basics and concepts Amplifier Gain Power Source Gain Saturation Experiment Experimental Setup Meanwavelength temperature dependence Pump power efficiency Conclusion Brief Summary Introduction A coherent optical amplifier is a device that increase the amplitude of an optical field while maintaining its phase. COP’s are important for various apllications; amplification of weak optical pulses such as those that travel through long a long length if optical fiber Basics and Concepts There are three types of photon- atom interactions Absorption of photons Stimulated emission Spontaneous emission Amplifier Gain Underlying principle for achieving the coherent amplification of light is light amplification by the stimulated emission of radiation in the process we get clone photon with same frequency, direction and polarization two photons can serve to stimulate the emission two additional photons and so on result is coherent light amplification Amplifier Gain (Cont’d) Coherent light amplification is due to when photon energy is nearly equal to the atomic transition energy level Essential is the presence of a greater number of atoms in the upper energy level Achieving such a population inversion requires a source of power to excite (pump) the atoms into the higher energy level Amplifier Power Source Laser amplifiers require an external source of power to provide energy The pump must provide a population inversion on the transition of interest Pumping may be achieved optically, electrically, chemically even by nuclear expansion Required conditions determined by rate equations which depends laser gain medium Amplifier Power Source (Cont’d) Rare-earth-doped silica fibers cab serve as useful amplifying media. Erbium doped fibre amplifier is the most deployed fibre amplifier Pumping is achieved by transmitting laser light Gain Saturation Ideal amplifiers have linear system that increases the amplitude of the input signal by a fixed factor, called amplifier gain Real coherent amplifiers deliver a gain frequency dependent For sufficiently high input amplitude real amplifiers may exhibit saturation Fails to increase in proportion to input amplitude Experiment ASE source experimental setup Forward Port Spectrum Backward Port Spectrum Forward Port Temperature Dependence Pump diode current = 75mA Pump diode current = 100mA m= -5.34+/-1.11 ppm/C m= -0.813+/-0.609 ppm/C Backward Port Temperature Dependence Pump diode current = 75mA Pump diode current = 100mA m= 6.30+/-1.91 ppm/C m= 2.90+/-0.37 ppm/C Output power vs pump power Forward port m=0.057 Efficiency=%5.7 Backward Port m=0.094 Efficiency=%9.4 Total eff=%15.1 Labview Interface Labview Block Diagram Conclusion Linear temperature dependence Without saturation pumping in the range 0-500 mW for 175 cm Er doped fiber silica References; http://www.sp.phy.cam.ac.uk/~SiGe/Stimulated%20Emission. html Bahaa E. A. Saleh, Malvin Carl Teich "Fundamentals of Photonics” Frank L. Pedrotti, Leno S. Pedrotti, Leno M. Pedrotti “Introduction to Optics“ E. Desurvire "Rare-Earth Doped Fiber Lasers and Amplifiers" Thank you for your attention Questions ??? ?? ?
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