Source: http://aoot.osa.org/oe/abstract.cfm?uri=oe-27-6-8011
Timestamp: 2019-04-21 18:49:41+00:00

Document:
We experimentally demonstrate speckle noise reduction and beam wander mitigation by using a rotating diamond/KBr pellet and a multimode fiber (MMF). As the diamond/KBr diffuser is rotated, the reflected speckle images that are captured by an infrared camera are temporally averaged. We demonstrate 78% speckle noise reduction by averaging 25 frames, which is within 80% of the theoretical contrast reduction. Large beam position fluctuations are also significantly suppressed by adding the MMF. This combination of beam wander mitigation and speckle reduction offers significant benefits for emerging optical technologies that use quantum cascade lasers as illumination sources.
C. A. Kendziora, R. Furstenberg, M. Papantonakis, V. Nguyen, J. Byers, and R. Andrew McGill, “Infrared photothermal imaging spectroscopy for detection of trace explosives on surfaces,” Appl. Opt. 54(31), F129–F138 (2015).
R. Furstenberg, C. A. Kendziora, J. Stepnowski, S. V. Stepnowski, M. Rake, M. R. Papantonakis, V. Nguyen, G. K. Hubler, and R. A. McGill, “Stand-off detection of trace explosives via resonant infrared photothermal imaging,” Appl. Phys. Lett. 93(22), 224103 (2008).
F. Fuchs, B. Hinkov, S. Hugger, J. M. Kaster, R. Aidam, W. Bronner, K. Köhler, Q. Yang, S. Rademacher, K. Degreif, F. Schnürer, and W. Schweikert, “Imaging stand-off detection of explosives using tunable MIR quantum cascade lasers,” in Quantum Sensing and Nanophotonic Devices VII (Vol. 7608, p. 760809) (2010).
M. F. Witinski, R. Blanchard, C. Pfluegl, L. Diehl, B. Li, K. Krishnamurthy, B. C. Pein, M. Azimi, P. Chen, G. Ulu, G. Vander Rhodes, C. R. Howle, L. Lee, R. J. Clewes, B. Williams, and D. Vakhshoori, “Portable standoff spectrometer for hazard identification using integrated quantum cascade laser arrays from 6.5 to 11 µm,” Opt. Express 26(9), 12159–12168 (2018).
R. Furstenberg, C. A. Kendziora, M. R. Papantonakis, V. Nguyen, and R. A. McGill, “Chemical imaging using infrared photothermal microspectroscopy,” Proc. SPIE 8374, 837411 (2012).
A. Hasenkampf, N. Kröger, A. Schönhals, W. Petrich, and A. Pucci, “Surface-enhanced mid-infrared spectroscopy using a quantum cascade laser,” Opt. Express 23(5), 5670–5680 (2015).
T. Tschudi, “Speckle reduction in laser projections with ultrasonic waves,” Opt. Eng. 39(6), 1659–1664 (2000).
G. Ouyang, Z. Tong, M. N. Akram, K. Wang, V. Kartashov, X. Yan, and X. Chen, “Speckle reduction using a motionless diffractive optical element,” Opt. Lett. 35(17), 2852–2854 (2010).
W. F. Hsu and C. F. Yeh, “Speckle suppression in holographic projection displays using temporal integration of speckle images from diffractive optical elements,” Appl. Opt. 50(34), H50–H55 (2011).
C. Magnain, H. Wang, S. Sakadžić, B. Fischl, and D. A. Boas, “En face speckle reduction in optical coherence microscopy by frequency compounding,” Opt. Lett. 41(9), 1925–1928 (2016).
G. E. Trahey, J. W. Allison, S. W. Smith, and O. T. von Ramm, “A quantitative Approach to Speckle Reduction via Frequency Compounding,” Ultrason. Imaging 8(3), 151–164 (1986).
D. S. Mehta, D. N. Naik, R. K. Singh, and M. Takeda, “Laser speckle reduction by multimode optical fiber bundle with combined temporal, spatial, and angular diversity,” Appl. Opt. 51(12), 1894–1904 (2012).
A. Efimov, “Coherence and speckle contrast at the output of a stationary multimode optical fiber,” Opt. Lett. 43(19), 4767–4770 (2018).
B. Redding, G. Allen, E. R. Dufresne, and H. Cao, “Low-loss high-speed speckle reduction using a colloidal dispersion,” Appl. Opt. 52(6), 1168–1172 (2013).
R. Furstenberg, C. A. Kendziora, C. J. Breshike, V. Nguyen, and R. A. McGill, “Laser speckle reduction techniques for mid-infrared microscopy and stand-off spectroscopy. in Next-Generation Spectroscopic Technologies X (Vol. 10210, p. 1021004) (2017).
S. Kubota and J. W. Goodman, “Very efficient speckle contrast reduction realized by moving diffuser device,” Appl. Opt. 49(23), 4385–4391 (2010).
G. Li, Y. Qiu, and H. Li, “Coherence theory of a laser beam passing through a moving diffuser,” Opt. Express 21(11), 13032–13039 (2013).
J. Lehtolahti, M. Kuittinen, J. Turunen, and J. Tervo, “Coherence modulation by deterministic rotating diffusers,” Opt. Express 23(8), 10453–10466 (2015).
B. Hinkov, F. Fuchs, J. M. Kaster, Q. Yang, W. Bronner, R. Aidam, and K. Köhler, “Broad band tunable quantum cascade lasers for stand-off detection of explosives,” in J. C. Carrano and C. J. Collins, eds. (International Society for Optics and Photonics), Vol. 7484, p. 748406 (2009).
T.-K.-T. Tran, S. Subramaniam, C.-P. Le, S. Kaur, S. Kalicinski, M. Ekwinska, E. Halvorsen, and M. N. Akram, “Design, Modeling, and Characterization of a Microelectromechanical Diffuser Device for Laser Speckle Reduction,” J. Microelectromech. Syst. 23(1), 117–127 (2014).
C. J. Breshike, C. A. Kendziora, R. Furstenberg, V. Nguyen, and R. A. McGill, ” “Stabilizing infrared quantum cascade laser beams for standoff detection applications.” in Quantum Sensing and Nano Electronics and Photonics XIV, vol. 10111, p. 101110B. (2017).
R. Müller, C. A. Kendziora, and R. Furstenberg, “Feedback stabilization of quantum cascade laser beams for stand-off applications,” in In Micro-and Nanotechnology Sensors. Systems, and Applications IX 10194, 101942U (2017).
R. Furstenberg, C. A. Kendziora, M. R. Papantonakis, V. Nguyen, and R. A. McGill, “Characterization and control of tunable quantum cascade laser beam parameters for stand-off spectroscopy,” in Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XVII (Vol. 9824, p. 98240L) (2016).
J. W. Goodman, Speckle Phenomena in Optics: Theory and Applications (Roberts & Company, 2007).
Fig. 1 Optical images of diamond/KBr pellets (a) 1% (wt) diamond (20 − 30 μm) / 99% (wt) KBr pellet and (b) 2% (wt) diamond (20 − 30 μm)/98% (wt) KBr pellet. (c) FTIR transmittance spectra for KBr pellet and 6 different diamond/KBr pellets with 1-3% (wt) loading level of diamond of two diamond size (20 − 30 μm, 4 − 6 μm) powders.
Fig. 2 Schematics of the (a) free beam path and (b) de-speckle measurement setup. A tunable QCL (Daylight Solutions “MIRcat-QT”) is employed as the active illumination source. The laser light transmitted through either free beam path or de-speckle unit (multimode fiber and diamond/KBr diffuser) illuminates an Infragold disk, and the diffusely reflected light is collected by an IR camera for the characterization of speckle noise.
Fig. 3 Captured images with (a) no diffuser, (b) a stationary diffuser and (c) a rotating diffuser (1% mass loading level of 20 − 30 μm diamond). (g) Line profiles extracted from the dashed lines in the images show speckle intensity fluctuation. The intensities of the line profiles marked “No diffuser” are normalized for comparison. (d – f) 2D fast Fourier transform (FFT) filtered images of the raw captured images. (h) Line profiles extracted from the dashed lines in the 2D FFT filtered images show reduced signal noise levels. All scale bars in the captured images are 2 mm. The laser wavelength is 9 μm. The average power of the laser is 400 mW.
Fig. 4 The reduction of speckle contrast C extracted from speckle images as a function of the number of averaged frames with no diffuser, with a stationary, and three rotating diamond/KBr diffusers of different diamond mass loading levels (1 to 3%). The orange line represents the theoretical reduction of speckle contrast. The reduction of speckle contrast C extracted from speckle images with 2D FFT filtering (red star) as a function of the number of averaged frames using a rotating diamond/KBr diffuser (1% of 20 − 30 μm). The speckle contrast values extracted from 2D FFT filtered images are in better agreement with the theoretical reduction of speckle contrast (orange line).
Fig. 5 (a) Beam centroid (X and Y), (b) Beam widths (X and Y). (c) Ratio (R) of beam centroid to beam width.

References: V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V.