The coherent random laser (CRL) from dye-doped polydimethylsiloxane (PDMS) has been investigated in both nanoparticle-doped (NP-doped) thin films and pure dye thin films. Compared with the literature, the pump threshold is only 1.5 mJ/cm in the pure dye thin film with a low dye concentration. The spontaneously formed micro-/nanocrystals of Pyrromethene 597 (PM597) dye support both gain and random feedback in the bulk of the PDMS during the sample preparation. When the SiO NPs were doped, the pump threshold was reduced to 0.75 mJ/cm. The threshold increased after the film was peeled off from glass, which indicates that the photon localization effect of the leaky-waveguide structure plays an important role in the reduction of the CRL threshold. By a change in the pump stripe length or the thickness of the film, the peak wavelength red-shifts 6.7 or 5.93 nm, respectively. The PM597 dye molecule solubility changes, and they spontaneously aggregate in the process of toluene volatilization; the PDMS cures, which is the reason for the formation of PM597 micro-/nanocrystals. This thin film random laser with a low dye concentration can be used in integrated optoelectronics and display imaging.

Random lasers from dye-doped nematic liquid crystal (DDNLC) cells with different rubbing methods were observed due to different random ring cavities that were formed. Through constructing cells with different rubbing methods on the forward and backward surfaces of light-emitting sides, we can get two random laser beams with different polarization directions from one DDNLC cell at the same time, and the polarization direction is along the rubbing direction of the light-emitting sides. Additionally, the influence of external electric field on the polarization degree of random lasers was also studied.

A high average power 1342 nm passively CW mode-locked picoseconds (ps) composite Nd:YVO4 laser was demonstrated with a semiconductor saturable absorber mirror (SESAM). The oscillator cavity was carefully designed to optimize the laser beam radii in the crystal and on the SESAM. The combination of composite bonded laser crystal, direct pumping, and dual end-pumped configuration was adopted to reduce the thermal effect and produce high output power with high beam quality. A maximum average output power of 7.63 W was obtained with a repetition rate of 77 MHz and a pulse duration of 24.2 ps under an absorbed pump power of 38.6 W, corresponding to an optical-optical efficiency of 19.7% and a slope efficiency of 25.9%, respectively. The beam quality factor M(2) was measured to be 1.49.

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We have proposed a novel approach to realize a high-energy ultrafast optical parametric oscillator (OPO) by intracavity pumping in a regenerative amplifier. In this way, we have experimentally demonstrated an unprecedented pulse energy of 30.5 μJ from a 1.5-μm singly resonant synchronously pumped OPO at a pulse repetition rate of 10 kHz with a pulse width of 7.0 ps. To the best of our knowledge, this is the highest pulse energy from an ultrafast laser OPO.

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A unidirectional coherent random laser is constructed by a sandwich structure consisting of two polydimethylsiloxane plates and a highly transparent ultra-thin liquid active layer embedded with silica nanoparticles (NPs). The optical feedback of the random laser is provided by both strong waveguide confinement and the SiO2 NPs’ multiple scattering. Compared with random laser in a quartz cuvette, the pump threshold is only 700 µJ cm−2. The lowest threshold is obtained in an optimum concentration of silica NPs. The change of peak positions in the liquid waveguide structure is larger than that in the quartz cuvette for different solvents. The peak-shift of the emission wavelength is more sensitive in the liquid waveguide structure, which is a promising platform for bio-chemical and bio-sensing applications.

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