196,064 research outputs found
Laser pulse control of a Q-switched Nd:YVO<sub>4</sub> bounce geometry laser using a secondary cavity
No full textPulsed laser operation is desirable for a wide range of applications such as laser micromachining in industrial manufacturing and laser marking for product identification. In these cases it is beneficial to have flexibility in the parameters of the laser pulse to suit the specific application. This can include the ability to achieve a wide range of pulse repetition rates, with some applications requiring variation of laser pulse rate from high rate (multi-kHz) to low rate or even an off-state in a fast timescale. To generate ultrahigh pulse rates requires Q-switched lasers with ultrahigh gain, but problems can arise if the modulation element is insufficient to prevent laser action or hold-off lasing at low repetition rates. In these cases, lasing output can occur when it is not desired. In this work we present a novel method for pulse control in a high gain bounce amplifier Q-switched system by using a secondary cavity to clamp the gain and allow for clean single pulse operation from very high (800kHz) to very low (e.g.1kHz) repetition rates
Application of the three-valence model of photorefraction to rhodium-doped barium titanate
No full textSmall signal and light induced absorption data taken at 633 nm and 1.06 ?m for different samples of rhodium-doped barium titanate (Rh : BaTiO3) have been analysed. These data have been used in conjunction with the three-valence model theory of photorefraction to determine ND, the total amount of rhodium in each sample. It is shown that the values of ND calculated at the two wavelengths for individual samples are inconsistent with each other, although no evidence for other impurities in the samples has been observed. This indicates that a more complex theory than the three-valence model is necessary to explain the photorefractive processes in Rh : BaTiO3, and that an additional photorefractive centre may not be sufficient to account for the observed discrepancies in ND
Performance of a continuous-wave self-adaptive gain-grating laser
No full textExperimental and theoretical studies have shown that three-dimensional gain gratings, optically written in a saturable laser amplifier, can act as very efficient (>1000%) diffractive optical elements and, in a four-wave mixing (FWM) geometry, can produce extremely high phase-conjugate reflectivity. A further development in the use of gain gratings for phase conjugation has been the employment of loop schemes to obtain self-pumped phase conjugation (SPPC) with only one input beam required. In reality, these devices are actually a novel type of (holographic) laser where the feedback is provided by diffraction from an externally-written gain-grating hologram
Coherent beam combining of self-adaptive lasers
No full textThe novel technique of phase conjugate self-organised coherent beam combination is reported. It is demonstrated that due to the spectral mode freedom of a phase conjugate self-adaptive laser that efficient "all-passive" combination of many high quality lasers can be achieved. Efficient combination (>92%) of two modules has been experimentally demonstrated to >30W in continuous wave operation. Recent results demonstrating pulsed operation are also reported
Multi-watt continuous-wave adaptive laser resonator
No full textWe present, for what we believe is the first time, results of continuous-wave diode-pumping of a Nd:YVO4 laser with an adaptive gain-grating resonator. The system is shown to produce more than a 7W output in a TEM00 single longitudinal mode with a laser beam propagation parameter M2 of 1.3 and 1.1 in the x and y axes, respectively. We demonstrate the self-adaptive abilities of the resonator by spatial correction of an intracavity aberrator for both injected and self-starting versions of the cavity
Continuous wave adaptive laser resonators using degenerate four-wave mixing in a diode bar side-pumped Nd:YVO<sub>4</sub> amplifier
No full textSelf-adaptive laser resonators based on diffraction from a gain grating have shown considerable promise for correction of distortion in high-average-power solid-state laser systems, as well as for spectral and temporal control of the laser radiation [1-4]. In these systems, the gain grating is formed by spatial hole burning caused by interference of coherent beams in the laser amplifier and modulation of the population inversion. The gain grating formation can be used for phase conjugation by using the amplifier in a four-wave mixing geometry [2], for self-pumped phase conjugation by using an input beam in a self-intersecting loop geometry [3] and for formation of a self-starting adaptive oscillator by providing additional feedback from an output coupler and requiring no external optical input. Experimental demonstrations have been performed successfully in several laser systems including flashlamp-pumped and quasi-c.w. pumped neodymium-doped amplifiers [1,2], in laser-pumped titanium-doped sapphire [4] and CO2 lasers. We present for the first time, demonstration of a continuous-wave self-adaptive holographic laser resonator. The operation is based on the very high reflectivities (>100) of a gain grating formed in a diode-bar side-pumped Nd:YVO4 amplifier
Continuous wave holographic laser resonators using degenerate four-wave mixing in a diode bar side-pumped Nd:YVO<sub>4</sub> amplifier
No full textDegenerate four-wave mixing techniques used to produce self-adaptive laser resonators based on diffraction from a gain grating have shown considerable promise for correction of distortion in high-average-power solid-state laser systems, as well as for spectral and temporal control of the laser radiation [1-4]. In these systems, the gain grating is formed by spatial hole burning caused by interference of coherent beams in the laser amplifier and modulation of the population inversion. The gain grating formation can be used for phase conjugation by using the amplifier in a four-wave mixing geometry [2], for self-pumped phase conjugation by using an input beam in a self-intersecting loop geometry [3] and for formation of a self-starting adaptive oscillator by providing additional feedback from an output coupler and requiring no external optical input. Experimental demonstrations have been performed successfully in several laser systems including flashlamp-pumped and quasi-c.w. pumped neodymium-doped amplifiers [1,2], in laser-pumped titanium-doped sapphire [4] and CO2 lasers. We present for the first time, demonstration of a continuous-wave self-adaptive holographic laser resonator. The operation is based on the very high reflectivities (>800%) [5] and more recently (>10,000%) of a gain grating formed in a diode-bar side-pumped Nd:YVO4 amplifier. We have subsequently modelled the FWM interactions and have found good agreement with experimental results. This resonator has been shown to correct for severe phase distortions introduced inside the loop. An output of ~1 W has so far been achieved, future steps include an additional power amplifier incorporated into the resonator loop geometry to give an expected multi-watt operation with a midterm goal of 10 W
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
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