We show two of our work on multi-mode nonlinear optical process. In a Ta2O5 waveguide of 100 nm in thickness, 8 μm in width and 4.3 mm in length, all-optical signal switching and power limiting operation were demonstrated by nonlinear multi-mode interference while the modes were properly excited by a near infrared pulse at the wavelength of 1064 nm, peak power of 100 W and the pulse duration of 1 ps. In supercontinuum process, a waveguide of 760 nm in thickness and 1.1 μm in width was designed where different guided modes were anomalously dispersive at different wavelengths. Supercontinuum spectrum spanning over an octave with high degree of spectral flatness was excited by a 100-fs laser pulse at the wavelength of 1030 nm. Spectral synthesis with a diffraction gratings mapped the spectral components attributed to specific waveguide modes. It inferred the possibility to engineer supercontinuum generation through waveguide-mode arrangement.
In this paper, we investigate the application of the EMD to automatically reduce speckles on the fringe pattern. It is
found that the number of the removed intrinsic mode functions (IMFs) is sensitive to the period of the fringe pattern, but
not sensitive to the speckle size and the speckle amplitude. Thus, a database system based on statistic simulations for
finding the optimization of removing speckles is built. With this database, more than 80% speckles on the fringe pattern
can be robotically reduced.
In this paper, we present an approach to enhance the image resolution by reassembling a couple of low-resolution
images. Image registration was performed by the fringe projection technique. Experimental results have shown that
accuracy better than sub-pixel of the low resolution camera can be achieved.
We present a database system based on the empirical mode decomposition (EMD) to automatically reduce the speckle in
a fringe pattern. With reference to the database, speckles on the fringe pattern can be efficiently and robotically reduced.
Percentage of the removed speckles can be predicted as well.
The 2nd-order fractional Talbot effect is employed to multiply the 10-GHz optical pulse-train injection for 2nd-order
ration-harmonic-mode-locking of a SOA fiber laser at 40-GHz. With improved modulation-depth by enlarging
pulse-extinction-ratio from 0.55 to 2.3, the SOAFL generates 8 ps pulsewidth and 170 fs timing jitter when injectionpulse
with 2-GHz peak-to-peak chirp.
A database system based on the empirical mode decomposition (EMD) to automatically reduce the subjective speckles in
a fringe pattern is presented. To accurately evaluate the performance of speckle-reduction by the EMD, a method to
design a computer generated signal is proposed as well. The simulation showed that the number to removed IMFs is
changed when the period of the computer generated signal or the signal-to-noise ratio varies. Thus, we built up a
database to identify the required number of removed IMFs. With reference to the database, speckles on the fringe pattern
can be efficiently and robotically reduced.
Phase-extraction from fringe patterns is an inevitable procedure in many applications, such as interferometry, Moiré
analysis, and profilometry using structured light illumination. Errors to phase-extraction always occur when the signal-to-
noise ratio is weak. In this paper, we use the empirical mode decomposition (EMD) with a generalized analysis model
to reduce the white noise from a fringe pattern. It is found that phases can be extracted with high accuracy once noise-reduction
is performed with this model.
Most 3-D shape measurements for a dynamic object always require that the obtained images not be blurred by motion. We show that it is not necessary to avoid the blurred image when projected fringe profilometry is employed. For objects that move within one period of the projected fringes, 3-D surfaces can be retrieved directly from the blurred fringes. Consequently, the presented method intensively reduces the cost of the detection system.
The speckle that is formed in coherent illumination confuses efforts to record an object's fine details. The confusion is
particularly severe in optical metrology and microscopy. In this paper, a scheme using the empirical mode
decomposition (EMD) to remove speckles is proposed. This makes it possible to accurately evaluate phases from a
fringe pattern illuminated by a coherent light source.
A method to reconstruct a 3D profile using a projected fringe profilometry from a 2D image blurred by uniform linear
motion is proposed. The proposed method offers following major advantages: (1) very low computation cost for the 3D
reconstruction, (2) only one phase measurement needed for operation, and (3) robust performance to analyze dynamic
objects.
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