Time averaging of multimode optical fiber output for a magneto-optical trap

Povilus, A.; Olson, Spencer E.; Mhaskar, Rahul; Teo, Boon-Keng; Guest, Jeffrey R.; Raithel, Georg

doi:10.1364/josab.22.000311

Cited by 7 publications

(7 citation statements)

References 6 publications

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“…By winding the fiber with a sinusoidal driving signal, bending effect and phase modulation occur simultaneously and speckle patterns can be time-averaged. To obtain effective time-averaged smoothing of the multiple spatial modes in the fiber, the phase of each mode should be varied by more than 2π on time scales faster than the response time of the measurement system [9].…”

Section: Resultsmentioning

confidence: 99%

Speckle Reduction in Near-field Image of Multimode Fiber with a Piezoelectric Transducer

Ha¹,

Lee²,

Oh³

et al. 2008

Journal of the Optical Society of Korea

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We propose and experimentally demonstrate an effective method to reduce near-field speckle noise at the output of a 50 μm graded index multimode fiber using a short cylindrical piezoelectric transducer (PZT) vibrating in the radial direction. The fiber was coiled as tightly as possible around the mandrel of the PZT and a periodic stretching effect was caused by the radial oscillations of the actuator. The output of the optical fiber using the He-Ne laser source was intensively observed by a CCD camera. By counting all the pixels corresponding to relative intensity graded into 256 levels in the selected area and by calculating standard deviation and mean value of the intensity, we could measure the speckle contrast and vibration effect quantitatively with reduction ratio of pixels and line profile of the illuminated region. It was clearly observed that the characteristics of the speckle pattern in the vibration-on state were significantly improved over that of the vibration-off state due to time-averaged smoothing.

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Section: Resultsmentioning

confidence: 99%

Speckle Reduction in Near-field Image of Multimode Fiber with a Piezoelectric Transducer

Ha¹,

Lee²,

Oh³

et al. 2008

Journal of the Optical Society of Korea

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“…Various analyses have been performed for phase modulation [1,4,8], and the main conclusion for effective smoothing of the spatial modes was that the relative carrier phase should be varied by more than 2π radian on a time scale faster than the response time of the detecting system.…”

Section: Theorymentioning

confidence: 99%

“…The acousto-optic modulation technique based on a piezoelectric transducer (PZT) could provide a common solution platform for MMF laser delivery applications. Recently, Povilus et al briefly reported a speckle-modulation technique using a cylindrical PZT to stabilize magneto-optical atom trapping [8]. Although the technique enabled time-averaged smoothing within a short time without post-processing, speckle control in MMFs has not been fully studied.…”

Section: Introductionmentioning

confidence: 99%

Acousto-optic control of speckle contrast in multimode fibers with a cylindrical piezoelectric transducer oscillating in the radial direction

Ha¹,

Lee²,

Jung³

et al. 2009

Opt. Express

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Abstract:We report efficient acousto-optic control of speckle contrast at the output of multimode fibers (MMFs) using a cylindrical piezoelectric transducer (PZT) vibrating in the radial direction. With appropriate packaging of an MMF around the PZT, periodic stretching and subsequent intensity modulation were achieved over the wound fiber to result in timeaveraged smoothing of the output within a short time. It was experimentally confirmed that light passed through the vibrating PZT-fiber assembly maintains the virtually partial coherence irrespective of the guide length and power splitting. Real-time vibration-off/on movies were presented, and their single-frame excerpts were analyzed. Electron. Lett. 15(23), 755-756 (1979). 13. E. G. Rawson, J. W. Goodman, and R. E. Norton, "Analysis and measurement of the modal-noise probability distribution for a step-index optical fiber," Opt. Lett. 5(8), 357-358 (1980). 14. D. U. Kim, S. C. Bae, J. Kim, T.-Y. Kim, C.-S. Park, and K. Oh, "Hard polymer cladding fiber (HPCF) links for high-speed short reach 1×4 passive optical network (PON) based on all-HPCF compatible fused taper power splitter," IEEE Photon. ©2009 Optical Society of America

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“…We examined the speckle reduction ratio by adjusting different driving frequency of the modulation actuator. The proposed technique can be utilized in high frequency modulation up to several MHz of the actuator so that the speckle patterns can be averaged over time 18 .…”

Section: Theory and Previous Workmentioning

confidence: 99%

Speckle reduction in multimode fiber with a piezoelectric transducer in radial vibration for fiber laser marking and display applications

Lee

Jung³

et al. 2008

Fiber Lasers V: Technology, Systems, and Applications

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We propose and experimentally demonstrate an effective method to reduce far-field speckle noise in multimode fiber with a short cylindrical piezoelectric transducer (PZT) vibrating in radial direction. In this study, the fiber was coiled as tightly as possible around the mandrel of the PZT and periodic stretching effect was caused by the radial oscillations of the actuator. This technique can be adapted at a high modulation frequency, so the speckle patterns can be timeaveraged. The output of the optical fiber was intensively observed by a CCD camera. By counting all the pixels corresponding to relative intensity graded 256 levels in selected area and by calculating the mean value and standard deviation of the intensity, we can measure the speckle contrast and vibration effect in quantitative measurands. It was clearly observed that the characteristics of the speckle pattern in vibration-ON-state were significantly reduced than that of vibration-OFF-state by comparing the proposed measurands as well as direct CCD images. We expect that the proposed speckle reduction technology would find viable applications in realization of fiber laser, laser marking, optical trapping and projection display systems.

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Time averaging of multimode optical fiber output for a magneto-optical trap

Cited by 7 publications

References 6 publications

Speckle Reduction in Near-field Image of Multimode Fiber with a Piezoelectric Transducer

Speckle Reduction in Near-field Image of Multimode Fiber with a Piezoelectric Transducer

Acousto-optic control of speckle contrast in multimode fibers with a cylindrical piezoelectric transducer oscillating in the radial direction

Speckle reduction in multimode fiber with a piezoelectric transducer in radial vibration for fiber laser marking and display applications

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