Spectral and temporal properties of optical signals with multiple sinusoidal phase modulations

Abstract

Optical signals generated by multiple sinusoidal temporal phase modulations (multi-FMs) applied to a monochromatic field are studied from the viewpoint of their optical spectrum and temporal modulations arising from spectral impairments. Statistical analysis based on the central limit theorem shows that the signals' optical spectrum converges to a normal distribution as the number of modulations increases, allowing one to predict the frequency range containing a given fraction of the total energy with the associated cumulative density function. The conversion of frequency modulation to amplitude modulation is analyzed and simulated for arbitrary multi-FM signals. These developments are of theoretical and practical importance for high-energy laser systems, where optical pulses are phase modulated in the front end to smooth out the on-target beam profile and prevent potentially catastrophic damage to optical components.

Rapid Growth of the Gradient Deuterium Deuterated Potassium Dihydrogen Phosphate Crystal

“…But fusion power stations are still a distant dream. , One of the most challenging issues in ICF facilities is laser-plasma instability (LPI). , With the further upgrading of laser energy, it is necessary to significantly improve the coupling efficiency between laser and plasma. The mainstream approach retains the original high-coherence laser drivers and relies on improved beam control (beam smoothing techniques) to reduce the negative impact of coherence . However, the coupling efficiency between laser energy and target fuel can be improved effectively by using broad-band lasers with low temporal coherence.…”

High-efficiency second-harmonic generation of low-temporal-coherent light pulse

“…The key to solving this problem is decoherence of high coherent diver laser to reduce instabilities caused by nonlinear processes [4,5], such as self-focusing, stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS) and crossed-beam energy transfer (CBET) [6][7][8]. At present, beam smoothing techniques, which reduce the temporal coherence (such as SSD, PS) [9][10][11][12] and spatial coherence (such as RPP, CPP, ISI, LA) [13][14][15][16] of laser, are the main solution and have been widely used in laser-fusion facilities around the world [17][18][19][20]. In general, the bandwidth of laser for ICF imposed by modulator is about 100 GHz, loosely speaking, an instantaneous frequency that varies periodically in tim [21].…”