We have presented an innovative laser-assisted reduction surgery (LARS) based on plasma-induced ablation and photodisruption effects. In addition, we developed a laser operation system. Fetuses of mice from the Institute for Cancer Research that were immersed in physiological saline were irradiated by convergent-pulsed laser with a wavelength of 1064 nm, pulse width of 6 ns, and pulse energy of 50 mJ. The hearts of the postirradiated fetuses were significantly damaged, which resulted in rapid fetal death. We also substantiated the safety of LARS by analyzing the heat distribution of the induced laser pulse with thermal distribution equations. The results demonstrate that this innovative method for pregnancy reduction is feasible.
We present here a stimulated emission based fluorescence lifetime imaging (FLIM) scheme using a pair of synchronized diode lasers operating at gain switched pulse mode. The two semiconductor lasers, with wavelengths at 635 nm and 700 nm,
serve as the excitation and the stimulation light sources for the ATTO647N labeled sample, respectively. FLIM is readily
achieved with their relative time delay controlled electronically. The coherent nature of the stimulated emission signal also allows FLIM at long working distance. In this way, a high performance all-semiconductor FLIM module is realized in a flexible, compact, and cost effective configuration.
Tapered fiber phase-conjugating mirrors (PCMs) have been experimentally investigated in a master-oscillator power amplifier system. The dependence of PCM properties such as threshold and reflectivity on the geometry of the fiber is discussed. The beam quality factor M2 of the output beam was 1.2, and the peak power reached 1.1 MW. In operation with 100-Hz repetition rates, the fluctuation of the output energy was 8%. A depolarization ratio of 3% and phase conjugation fidelity above 90% were also demonstrated.
A study of the gain-switching process and output characteristics in a Nd:YVO4 microchip laser end-pumped by a fiber-coupled laser diode (LD) is reported here. The gain-switched laser pulses with controllable repetition-rate from 1Hz to 4kHz and pulse width of 16 ns are obtained. To analyze the gain-switching dynamics of the LD end-pumped Nd:YVO4 microchip laser, a theoretical model has been developed. The model is based on the rate equations of four-level systems and some practical physics conditions. Numerical simulations using the model illustrate the dependence of buildup time, pulse width and peak power of the gain-switched laser pulse on the pumping parameters. The experimental results coincide well with the theoretical analysis.
A broad area laser diode (BAL) external cavity is experimentally investigated and analyzed using ray transfer matrices. In the experiment, a grating that is placed at the image plane of the output facet of the BAL is used as an external cavity mirror for the slow axis and as a wavelength selective component for the fast axis at the same time. By tilting the grating with respect to the slow and the fast axis direction, respectively, the number of transverse modes oscillating in the cavity can be limited and the spectral line width of the laser diode can be reduced. With this setup, a laser beam with an improved beam quality, an output power of 230 mW and a spectral line width of 0.6 nm (300 GHz) is obtained when operating the BAL at 2.7 times the threshold drive current. We have also investigated a different cavity configuration to achieve alignment insensitivity and stable operation in which the grating was replaced by a flat HR mirror. With a similar beam quality, at the same operation current of the BAL a laser beam with a power of 320 mW and a spectral line width of 1.5 nm (750 GHz) is obtained with this setup.
Using the combined crystal Cr4+:YAG -Nd3+:YAG pumped by LD, the selfQ-switched laser pulses are obtained. The combined crystal with 8mm long and 1mm diameter is doped with 0.2% Cr4+ in one side and 1.1% Nd3+ in the other side. As the gain medium and the saturable absorber simultaneously in one material, this laser possesses a compact structure and high efficiency. Using the Laser diode CW pumping Cr4+:YAG -Nd3+:YAG single crystal micro-cylinder, the self Q-switched laser pulses with the pulse width of iOns and the pulse repetition rate of 10KHz are obtained. The average output power is I 8mW. From the rate equations considering the saturable absorption the pulse width and repetition rate vs. pump power are theoretically calculated. From this theory the pulse duration and output power of single pulse are independent of the pumping power, but the repetition rate almost linear increased with the pumping power. These results agree with the experimental measurements.
Using a LD as the pumping source in the CW mode and pulsed mode, we have got the self Q-switched laser in the co-doped Cr4+:Nd3+:YAG laser microchip with 2 mm thickness. When the LD operated in cw mode, the output laser is self Q-switched due to the saturable absorption of the Cr4+ center. Using the cw pumping laser of 3.3 W, the output laser of 3.86 mW operated in the quasi-CW mode with the repetition rate of 13 KHz and the pulse width of 40 ns was obtained. Using the pulsed pumping with 100 Hz repetition rate and 5 ms pulse width, the laser pulse series with several sub-pulses is obtained.
The laser properties of the Rhodamine B and Rhodamine 6G doped xerogels as the solid dye tunable laser active materials are studied. The second harmonic wave 532 nm of Q- switched Nd:YAG laser with 22 ns pulse width was used as the pumping laser. With 0.2 mJ - 0.7 mJ pulse energy of pumping laser we obtained the output laser pulse with some (mu) J. The measured center wavelength for Rhodamine B is 594 nm, the spectral range is 585 nm - 604 nm, the energy conversion efficiency is 25%. For Rhodamine 6G the center wavelength is 566 nm, the spectral range is 556 nm - 575 nm, the energy conversion efficiency is 35%.