| dc.description.abstract |
The modes are divided into two types: Longitudinal mode and Transverse mode. Longitudinal mode: its characteristics for the time axis changes, affecting its temporal coherence; transverse mode: its characteristics for the changes in the spatial axis, affecting its spatial coherence. In order to make the laser has a good spatial coherence, facilitates the transmission and focus of light, the vast majority of the laser will be set to the transverse mode as TEM00 fundamental mode, To produce a single longitudinal mode is the main research direction of the experimental study.
Single-mode lasers with high intensity, very narrow spectral width, high collimation and other characteristics, are widely used in spectroscopy, space telemetry, optical fiber communication systems. In this study, the Volume Bragg Grating (VBG) is used as the second output coupling mirror to replace the dielectric output coupling mirror, which narrows the signal optical bandwidth of the optical parametric oscillator, then we use Electro-Optic Polarization Mode Converter ( EO PMC) to modulate polarization as two polarization rotators on both ends of optical parametric gain medium (OPGM), so that the light waves in the cavity will not produce standing wave but in the form of traveling wave transmission in the cavity , which inhibits the homogeneity broadening that caused by the special-hole burning phenomenon produced transverse mode.
In this study, the comparison of the optical spectrum and the mode of the optical parametric oscillator in the standing wave operation and the electro-optical polarization modulator is carried out under the condition of the traveling wave. Compared with the standing wave, the half-height width has a narrowing effect, and the spectrum half-width is from 0.1 nanometer under standing wave operation narrowed to 0.01 nanometers below (our optical spectrometer resolution limit) under traveling wave operation. | en_US |