## 1 Introduction  
High-power single-frequency laser systems have become increasingly attractive thanks to their high spatial and temporal coherence, which has enabled technological advances in many applications such as high-resolution spectroscopy, remote sensing, non-linear frequency conversion, and holography. In particular, remote Raman spectroscopy [1, 2] is witnessing increasing use, especially in military and defense applications, to detect and identify chemical, biological, radiological, nuclear, or explosive materials [3]. The Raman signal strength (intensity) is directly proportional to the power of the laser used to excite the sample, and inversely proportional to the laser wavelength [4]. In this regard, diode-pumped solid-state lasers are desirable laser sources, as they offer low noise, good power stability, and good beam pointing stability. Power scaling of single-frequency laser sources at 532 nm is, therefore, very attractive. It can be achieved by power scaling the signal at 1064 nm and/or increasing the efficiency of second-harmonic generation. The former solution raises significant challenges that worsen with increasing compactness. The reason is that the combination of high power, small fiber core, and narrow spectral linewidth usually results in the onset of stimulated Brillouin scattering (SBS) [5] and, to a smaller extent, other undesirable power-scaling limitation effects occurring in the fiber, such as high thermal loading [6] and photodarkening [7]. SBS is generated by the non-linear interaction of the laser signal and the Stokes fields through an acoustic wave generated in the fiber through electrostriction [8, 9]. When the optical power exceeds a certain power threshold \(\mathrm{P_{crSBS}}\), a strong frequency-shifted, backward-propagating wave is generated in the fiber, causing power instability. The SBS threshold power is proportional to the fiber core area and inversely proportional to the fiber length. Therefore, to power scale the signal at 1064 nm, we have chosen to use highly Yb-doped fibers, which contributes to both suppressing SBS and maintaining compactness [7]. On the other end, the generation of high single-frequency powers in the visible range in a simple and compact format is possible by using periodically-poled nonlinear crystals in a single-pass configuration. This solution is particularly important for single-frequencylasers, because it can provide high conversion efficiencies even at limited fundamental powers (see Table 1). Even though periodically poled Mg-doped lithium niobate (MgO:PPLN) has a higher effective nonlinear optical coefficient (d\({}_{\text{eff}}\approx\) 16 pm/V) [10] than PPKTP (d\({}_{\text{eff}}\approx\) 10 pm/V) and PPLT (d\({}_{\text{eff}}\approx\) 9 pm/V) [11], its lower thermal conductivity (4.4 W/(mK) [12] makes it less beneficial at high optical power. Nevetheless, a conversion efficiency of 34% and an output power 3 W at 532 nm were demonstrated by [PERSON] et al. [13] using a single-pass configuration. [PERSON] et al. [14] reported 30% and 7.5 W in the same configuration. A higher conversion efficiency of 66% was demonstrated by [PERSON] et al., who reported an output power of 5 W using a multi-pass scheme instead [15]. These three reports all used a crystal length of 25 mm and CW excitation. In most reports of green generation in the CW mode using PPLN crystals and both a fundamental power higher than 7 W and an output power higher than 2.5 W at 532 nm [10; 16; 17; 18], gives rise to green-induced infrared absorption (GRIIRA). This effect causes damage to the material [19] and other thermal limitations such as thermal dephasing and thermal lensing, resulting in constraints of the conversion efficiency and deterioration of the generated beam quality. One way to overcome the thermal limitations is to operate the laser in a pulsed mode. Second-harmonic generation benefits significantly from this approach, in two ways.