Enhancing type-II optical second-harmonic generation by the use of a laser beam with a rotating azimuth of polarization

Abstract

We propose a frequency converter which exploits laser pulses with changing state of polarization. The use of such pulses as a pump source for an extracavity doubling crystal is shown to result in the large conversion efficiency. These pulses can also provide a fairly good tool of monitoring the shape of the harmonic pulse. It is shown that temporal variations of the polarization direction experienced by the pump pulse in this system may cause considerable shortening of the harmonic pulse.

IR tunable narrow-band nanosecond converter with a microchip pump source and periodically-poled Lithium Niobate

“…Due to a hybrid Q-switching technique applied (active, which is due to the modulation of the laser diode current, and passive, given by the presence in the laser cavity of the Cr 4+ :YAG saturable absorber [18]), the MPL was forced to generate a CW train of stable in amplitude and width short pulses with adjustable repetition rate. The polarization sensitivity of losses in the Qswitching absorbing element allows generation of definite polarization mode [19], which is crucial for stable and effective non-linear wavelength conversion (notice that our approach to ensure stable output polarization seems to be an alternative to the existing methods of intra-cavity polarization control in Nd 3+ :YAG lasers (see e.g. [20] and references therein).…”