A diode-pumped mode-locked Nd:YVO₄ 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 sech² 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.

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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.

We present an EO Q-switched Tm:YAP laser constructed with a periodically poled Mg-doped congruent lithium niobate (PPMgCLN) Bragg modulator. A 2-mm-thick PPMgCLN modulator was adopted, and the internal stress generated in the electric poling process was released by annealing. The peak stress-induced refractive index variance for e-wave was deduced to be 2.29 10^-5 at 1064 nm. When the absorbed pump power and repetition rate were 13.4 W and 1 kHz, respectively, the laser had a Q-switched pulse energy of 2 mJ, a pulse duration of 60 ns, and a peak power of 33.3 kW. By varying the reflection of the output coupler, output wavelengths of between approximately 1985 and approximately 1940 nm can be selected, making this laser a potential tool for pumping mid-IR sources and biomedical applications.

A diode-pumped Q-switched mode-locked Nd:YVO₄ laser via a positive cascaded second-order Kerr lens using periodically poled MgO:SLT at 1064 nm was reported. Q-switched mode-locking performances, including pulse duration, output power, and bandwidth, were studied under different pump conditions. Under 28 W quasi-CW (QCW) diode pump peak power, the measured mode-locked pulse train, Q-switched repetition rate, and Q-switched pulse duration were 18 ps, 300 kHz, and 50 ns, respectively. The highest peak power of a single pulse near the maximum of the Q-switched envelope was greater than 150 kW.

We report an experimental observation of radiation-induced optical absorption in undoped congruent lithium niobate (LiNbO₃) crystals between the 190 nm and 3200 nm wavelength range. It was found that high-dose (up to 288 Gy) gamma rays did not significantly affect the optical absorption of LiNbO₃ during that wavelength range. However, upon the order of 10¹⁶ cm⁻² neutron irradiation, the change in the absorption coefficient was up to 0.6 cm⁻¹ at a wavelength of 532 nm and remained after 13 days in the dark at room temperature. The nonlinear optical performance was characterized by conducting third-order quasi-phase-matched second harmonic generation in neutron-irradiated periodically-poled LiNbO₃, showing that the phase-matching condition was altered, and the conversion efficiency was still comparable with a non-irradiated one.