Speckles and their dynamics for structured target illumination: optical spatial filtering velocimetry

Jakobsen, Michael Linde; Yura, H. T.; Hanson, Steen Grüner

doi:10.1088/1464-4258/11/5/054001

Cited by 2 publications

(2 citation statements)

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“…In the present setup, the sample rate is determined by the update rate of the camera. However, if the camera is replaced/combined with spatial filtering velocimetry [11], a substantial increase in response time will be possible. This might reduce the sensitivity of the SW.…”

Section: Discussionmentioning

confidence: 99%

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Speckle-displacement-based wavemeter for mode-hop and side-mode detection

et al. 2022

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A speckle-displacement-based wavemeter is combined with a spatial-fundamentalmode-pass filter to eliminate the influence of multi-mode operation on the directionality of the resulting output from a Distributed Bragg Reflector tapered Laser (DBR laser). The proposed setup is characterized theoretically and experimentally, and detections of modehops and side-mode suppression ratio in the optical output are demonstrated. The laser illuminates a rough surface at an oblique angle, and a camera observes the corresponding speckle pattern from an almost identical back-scattering direction. As the wavelength of the laser shifts, the speckle pattern responds with a corresponding displacement, which is approximately linear with respect to the shift within the detection area. The wavemeter tracks continuously the shifts of the speckles pattern by tracking the peak of the covariance function of sequentially acquired images. In this way, the speckle-displacement-based wavemeter achieves a spectral resolution of 10.4 MHz. Mode-hops in the laser do not cause any impeding decorrelation of the speckle patterns. Interestingly, the actual side-mode suppression ratio is related to the peak height and width of the absolute covariance function. A wavemeter, which is capable of measuring wavelength, mode-hops and side-mode suppression ratio, is highly useful for spectroscopy, quantum optics, nonlinear frequency conversion and other applications requiring stable single-frequency laser light, especially when using diode lasers.

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Section: Discussionmentioning

confidence: 99%

“…However, the setup was simple, as it only involved a scattering surface, here a sandblasted aluminum plate, and a CMOS array. A way in which wavelength changes can be followed on a fast time scale is by shearing the speckle pattern [11] across a grating-like structure [12]. No intermediate optical components were required.…”

Section: Introductionmentioning

confidence: 99%