High gain fiber-solid hybrid double-passing end-pumped Nd:YVO₄ picosecond amplifier with high beam quality*

Abstract

We propose a fiber-solid hybrid system which consists of a semiconductor saturable absorber mirror (SESAM) mode-locked fiber seed with a pulse width of 10.2 ps and a repetition rate of 18.9 MHz, a two-level fiber pre-amplifier and a double-passing end-pumped Nd:YVO4 amplifier. In the solid-state amplifier, to enhance the gain and the extraction efficiency, a specially designed structure in which the seed light passes through the gain medium four times and makes full use of population inversion is used as the double-passing amplifier. Besides, the beam filling factor (the ratio of the seed light diameter to the pump light diameter) and the thermal lens effect of the double-passing amplifier are considered and its optical-to-optical conversion efficiency is further improved. To preserve the beam quality of the double-passing amplifier, a new method of spherical-aberration self-compensation based on the principles of geometrical optics is used and discussed. Our system achieves a maximum average power of 9.5 W at the pump power of 28 W, corresponding to an optical-to-optical efficiency of 27%. And the beam quality factor M 2 reaches 1.3 at the maximum output power.

Compact 15 mJ Fiber–Solid Hybrid Hundred-Picosecond Laser Source for Laser Ablation on Copper

“…However, the lower single-pass gain and complex multi-pass structure significantly increase the technical complexity and operation maintenance cost of the amplification system. By contrast, the slab amplifier is quite advantageous in terms of technical complexity [20,21]. Nevertheless, the slab amplifier has a special pumping structure, which requires a large number of coupling and shaping systems.…”

“…Additionally, it is difficult to grow large-sized slab crystal; hence, it is much less powerful than rod or bulk laser amplifiers in terms of output energy. The rod or bulk laser amplifier still has good development prospects because of its advantages of simple structure, mature pump module technology, and absence of complex shaping system [22][23][24]. The Nd:YAG crystal is the most common gain medium in picosecond rod or bulk amplifiers.…”

High Stability Industrial-Grade Nd: YVO4 Picosecond Laser Amplifier With High Average Output Power

“…al. [24] demonstrated a two-stage amplification system to amplify the output from a seed laser with a pulse width of 10.2 ps and a repetition rate of 18.9 MHz. One of the most appealing advantages of the traveling wave amplification technique is that it can be used in a multi-pass and/or cascaded manner in order to make up for its shortcomings of low single-pass and double-pass amplification.…”