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The wave nature of light has been widely demonstrated in a double-slit experiment, which has played a special role in physics teaching. When monochromatic light passes through the double-slit sheet, the diffraction and interference fringes can be observed in the far-field regime. The interference of light causes the beams passing through the two slits to interact with each other, but each slit still retains the diffraction characteristics of a single slit, so the result is a combination of diffraction and interference patterns.

Polarization-resolved second harmonic generation (P-SHG) microscopy is commonly used to analyze the second-order susceptibility, χ(2), tensor, which enables the calculation of the molecular structure of harmonophores. However, despite extensive research on type I collagen, the measured χ(2) ratios vary considerably among published values, which raises the question of whether P-SHG imaging is universally applicable to all tissues containing harmonophores. In this work, we propose that the deviation of χ(2) ratios is primarily due to ignoring the molecular tilt angle and chirality in image analysis. To confirm our hypothesis, we present an analytical model based on C6 symmetry that takes into account these two factors. We also introduce an imaging scheme that splits SHG into X- and Y-polarized image components for χ(2) tensor analysis. Our approach effectively improves the precision of determining χ(2) ratios, depending on how much the two factors affect the P-SHG signals. [ABSTRACT FROM AUTHOR]

A novel dual-wavelength actively Q-switched laser by a cascaded electrooptic periodically poled lithium niobate (PPLN) Bragg modulator has been developed. Two PPLN Bragg modulators with grating period \Lambda1 = 20.3 (EPBM1) and \Lambda2 = 25.7\ \mu\m (EPBM2) are integrated monolithically and used to separately Q-switch the transitions between ^4F3/2 \rightarrow ^4I11/2 and ^4F3/2 \rightarrow ^4I13/2 at the same Bragg angle. When applying 20-W diode power and 1-kHz Q-switching rate, the output wavelength can be selected between 1063 and 1342 nm with the peak power values of 27.6 and 1.6 kW, respectively. Utilizing two LBO crystals and an intracavity frequency doubling configuration, the green and red lasers can be selectively generated with the peak power values of 19 and 0.183 kW, respectively. The coupling effect between two PPLN Bragg modulators can be further reduced by adopting a longer EPBM1 and enhancing the performance of ^4F3/2 \rightarrow ^4I13/2 at the high pump power region. [ABSTRACT FROM PUBLISHER]

A diode-pumped mode-locked Nd:YVO 4 laser via positive cascaded second-order Kerr lens using periodically poled MgO:LN at 1064 nm was reported. Mode-locking performances including output power, bandwidth, pulse duration, and time-bandwidth product were studied under different phase-mismatched conditions. The induced nonlinear phase combined with soft aperture effect yield a stable mode-locked operation in a wide phase-mismatched range (-8π < ∆kL < -π). Additionally, the mode-locking bandwidth was broadened by self-phase modulation and the time-bandwidth product was increased to be more than twice the ideal product for a sech 2 pulse shape. Under 11 W diode pump power, the measured average power, pulse repetition rate and pulse duration are 1.3 W, 186 MHz and 2.8 ps, respectively.

We experimentally demonstrate polarization bistability in a dual-wavelength Nd:YVO4 laser at 1064 nm (4F3/2→4I11/2) and 1342 nm (4F3/2→4I13/2) by using an intra-cavity electro-optic periodically poled lithium niobate (PPLN) Bragg modulator to control the loss at 1064 nm. An inverse hysteresis switch was observed between 1064 nm and 1342 nm lasers with orthogonal polarizations by increasing and reducing the loss induced by the PPLN. The size of the hysteresis increased with increasing pump power. This paper provides an explanation based on cross-gain saturation for this bistable behavior of polarization.