## 1 Introduction  
High-power, diode-pumped, solid-state lasers have been utilized as practical industrial tools for a wide variety of cutting, drilling and welding applications due to their long diode bar lifetime, high output power, and high laser beam quality. Over the past few years, as diode bars have become more powerful and lower in cost, diode-pumped lasers have been used more commonly to replace flash-lamp pumped systems. Recent progress in the development of diode stacks has offered significant power enhancement for diode-pumped, solid-state lasers [1]. Diode-pumped, active Q-switched lasers, which show good beam quality and high output peak power, are commonly utilized in material processing and nonlinear frequency conversion applications [2; 3; 4; 5; 6]. The Nd:YAG crystal has a long upper-state lifetime (230 \(\upmu\)s)and superior thermal-mechanical and optical properties that allow it to easily generate high peak power and high energy Q-switched laser pulses [7].  
The use of the side-pumped Nd:YAG gain medium configuration readily assists high power 1064 nm lasers, and laser diode (LD) end-pumped, Q-switched lasers can easily be used to fabricate TEM\({}_{00}\)-mode lasers with an output power of several tens of watts. However, LD end-pumped lasers have the disadvantages of complex pump optics and severe thermal problems when reaching a high output power with good beam quality [8]. LD side-pumped lasers do provide an alternative to end-pumped lasers [9,10], but the optical-to-optical efficiency in TEM\({}_{00}\)-mode operation is relatively low, typically between 10% and 15% [4,9,11,12]. In a 2007 study, researchers successfully obtained a 50 mJ output energy at 1064 nm with a 10 ns pulse duration, a 5 W average output power, and a 5 MW peak power with a 420 W quasi-CW laser-diode-array pumping at 808 nm and a modulating repetition rate of 100 Hz [13]. In 2009, [PERSON] _et al_. successfully demonstrated a 140 mJ 1064 nm laser with a pulse duration of 10 ns and a pulse repetition of 20 Hz; the beam divergence angle was less than 3 mrad, and the optical-to-optical conversion efficiency reached 11.7% [14]. In 2013, [PERSON] _et al_. reported a maximum output energy of 210 mJ using an Nd:YAG laser with a pulse repetition rate of 30 Hz [15].  
In this study, a high-power, diode-side-pumped, Q-switched Nd:YAG solid-state laser was tested under 808 nm side-pumping without a water cooler. At a pump diode current of 80 A and a pump pulse duration of 200 \(\upmu\)s, a 350 mJ pulse laser was obtained with the following characteristics: a 10 ns pulse duration, a 10 Hz repetition rate, a 5% relative stability of output energy, and a 15% optical-to-optical conversion efficiency. The conversion efficiency of the entire laser system (electrical to 1064 nm optical radiation) was approximately 7.5%--which was much higher than that of a flash-lamp pumped laser system. The diameter of the beam was measured at 6.73 mm, with a divergence angle of less than 0.8 mrad and a beam quality of \(M^{2}<4\). To the best of our knowledge, this demonstration represents the highest output power of a diode-pumped, Q-switched Nd:YAG solid-state laser with a TEC and with very good output energy relative stability.