Mode-locked Erbium-Ytterbium Doped Fiber Laser - Revision history

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Aplstudent: /* Additive-pulse Mode Locking */

2015-07-17T18:18:00Z

‎Additive-pulse Mode Locking

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 [[File:Pulse6.jpg|500px]]
 [[File:Sinsoidal_vs._Bandwidth_Limited.png|500px]]
-[[File:OSA_Images.png|500px]]
+Using an an Advantest Q8381A Optical Spectrum Analyzer, the optical spectrum was characterized. The top spectrum shown below reveals a stable stretched pulse for passive length 5.219 m and active: 3.095 m. Adding 0.49 m of passive fiber between the output coupler and the fiber bench, introduced side peaks on either side of the central peak. These side peaks appeared stable and may indicate the onset of a soliton pulse regime. It is also possible that they appear due to amplified competing ring modes. The FWHM for these pulses ranged from 0.5nm to 2 nm. The larger plateau that the pulses sit on is likely due to amplified spontaneous emission.

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 Simulated Q-switching of mode-locked pulse train:
-[[File:Q-Switching.png|400px]]
+[[File:Q-Switching.png|300px]]
 == Data ==
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 [[File:Pulse6.jpg|500px]]

← Older revision		Revision as of 21:26, 6 September 2015
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	Simulated Q-switching of mode-locked pulse train:		Simulated Q-switching of mode-locked pulse train:

		+	[[File:Q-Switching.png\|400px]]
	== Data ==		== Data ==

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 necessary to reduce the length of active fiber to ensure that all
 dopants are sufficiently pumped. By reducing the length by 18%,
-.91m, the giant pulsing was eliminated for full pump power
+.91m, the giant pulsing was eliminated for full pump power.
 == Data ==

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 [[File:Soliton.png|500px|Soliton Pulse Regime]]
 [[File:Stretched.png|500px|Stretched Pulse Regime]]
 == Data ==
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 == Other References ==
 . R. Paschotta, “Passive Fiber Optics,” RP Photonics Consulting GmbH (2015).
 . E. Garmire and A. Yariv, “Correction to "Laser mode-locking with saturable absorbers",” IEEE Journal of Quantum Electronics 3, 377–377 (1967).
 . B. Collings, K. Bergman, S. Cundiff, S. Tsuda, J. Kutz, J. Cunningham, W. Jan, M. Koch, and W. Knox, “Short cavity erbium/ytterbium fiber lasers mode-locked with a saturable Bragg reflector,” IEEE Journal of Selected Topics in Quantum Electronics 3, 1065–1075 (1997).
 . H. Zhang, D. Tang, M. Tlidi, L. Zhao, and X. Wu, “Dispersion-managed dark solitons in erbium-doped fiber lasers,” p. 18 (2010).
 . K. Tamura, C. R. Doerr, L. E. Nelson, H. A. Haus, and E. P. Ippen,“Technique for obtaining high-energy ultrashort pulses from an additive pulse mode-locked erbium-doped fiber ring laser,” Optics Letters 19,
 (1994).
 . K. Tamura, E. P. Ippen, H. A. Haus, and L. E. Nelson, “77-fs pulse generation from a stretched-pulse mode-locked all-fiber ring laser, Optics Letters 18, 1080 (1993).
 . G. Agrawal, Nonlinear Fiber Optics (Academic Press, 2001), 3rd ed.
 . B. Saleh and M. Teich, Fundamentals of Photonics (John Wiley & Sons, Inc., Hoboken, NJ, 2007), 2nd ed.
 . K. Tamura, L. E. Nelson, H. A. Haus, and E. P. Ippen, “Soliton versus
 nonsoliton operation of fiber ring lasers,” Applied Physics Letters 64,149 (1994).
 . J. L. Wagener, P. F. Wysocki, M. J. F. Digonnet, H. J. Shaw, and D. J. DiGiovanni, “Effects of concentration and clusters in erbium-doped fiber lasers,” Optics Letters 18, 2014 (1993).

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 GVD for our co-doped multi-mode active fiber.
-[[File:Soliton.png]]
+[[File:Soliton.png|500px|Soliton Pulse Regime]]
 == Data ==

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 where n_0 is the material index of a medium, and n_2 is the nonlinear index coefficient and I is the pulse intensity [7]. With the pulse traveling with elliptical polarization through the cavity, this effect causes the vertical and horizontal polarization components to experience different phase shifts. This effect functions like material birefringence which causes a similar differential group delay, resulting in polarization mode dispersion and a rotation of the elliptical polarization which increases linearly with the length of the fiber [8]. As such, the half-wave plate is appropriately rotated to align the rotated ellipse to the polarizing element that functionally trims the pulse. The Kerr nonlinearity additionally causes self-phase modulation (SPM), which causes spectral broadening in anomalous fibers and balances spectral compression due to negative GVD. In normal dispersion fibers, like the co-doped active fiber used in our cavity, SPM functions independently of GVD [3]. The magnitude of SPM increases with length of propagation, and left unbalanced it can cause spectral oscillations and instability.
 When ratio of passive to active fiber in cavity yields net zero or negative dispersion, a soliton pulse will form. Solitons are self stabilizing and maintain their spectral and temporal shape
 throughout the entire cavity due to the balance of GVD and

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 - Peak of the circulating pulse is enhanced, whereas the wings are attenuated.
-== The Kerr effect ==
+== Kerr Mode Locking ==
 [http://www.rp-photonics.com/kerr_effect.html Kerr Effect]
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 Nonlinear polarization is generated in the medium, which modifies the propagation properties of the light.
 - half wave plate rotates polarization so that the fast axis (highest intensity)is in line with the polarizer;
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 [[File:OpticalBench.jpg|500px]]
 == Data ==
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 [[File:Pulse6.jpg|500px]]

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 The principle used in our fiber laser mode locking are:
-- Nonlinear phase shifts in a single-mode fiber.
+- Nonlinear phase shifts in a single-mode fiber proportional to the intensity of the signal.
 - Pulses returning from the fiber resonator into the main laser resonator interfere with those pulses which already are in the main resonator.