Compact, diode-side-pumped Nd^3+:YLiF_4 laser at 1053 nm with 45% efficiency and diffraction- limited quality by mode controlling

Abstract

We demonstrate what we believe to be the highest efficiency obtained to date in a transversely diode-pumped Nd3+:YLiF4 slab laser operating at 1053 nm. The compact 11-cm-long laser cavity configuration is based on total internal reflection of the intracavity beam at the pump facet of the gain crystal to improve the overlap with the pump radiation. Multimode operation with 9.5 W of output power and an efficiency of 45% is obtained for 21 W of pump power in a single-pass configuration. Using a second pass through the crystal and a new mode-controlling technique, the beam quality is improved to the diffraction limit with 6.9 W of output power and 33% of optical-to-optical efficiency.

Compact, diode-side-pumped and Q-switched Nd:YLiF4 laser cavity operating at 1053 nm with diffraction limited beam quality

“…In CW operation fundamental mode was maintained up to a maximum pump power of 21 W at 792 nm, whereas in the Q-switched and QCW regime, we achieved still fundamental mode with 34 W at 797 nm [11]. This behavior is due to the higher absorption cross-section of Nd:YLF along the pi-polarization at 797 nm with respect to 792 nm, as shown in Fig.…”

“…The separation between both beams inside the crystal for which pure TEM 00 mode as well as the highest power are obtained is not critical and ranges approximately from 1.6 mm to 2.0 mm, depending on pump power. For smaller or larger sepa- In this work, we show experimentally, that TEM 00 mode can be maintained in this novel cavity for much higher pump power than in the CW case [11]. We used a 34 W, TM-polarized and fast-axis collimated diode operating at 797 nm that was focused into the crystal by a f = 2.5 cm spherical lens, resulting in a spot size of approximately 4 mm × 0.1 mm in the horizontal (z) and vertical directions (y) in Fig.…”

“…Open circles are for operation of TEM 10 and TEM 00 together; triangles for additional operation of the TEM 20 mode not change significantly the onset of higher order modes. This is quite different in bounce lasers as has been shown in [11]. The explanation is as follows: At the location on the pump facet where total internal reflection occurs, the center of the TEM 00 mode (and therefore peak intensity) is exposed.…”

“…4, when pumping the lower absorption cross-section at 792 nm, a higher order mode starts oscillating already at 21 W of pump power, whereas for 797 nm pumping a much higher pump power of 36 W may be supplied without onset of higher order modes. For the simulation, we used additional parameters given in [7,11].…”

Power scaling of a side-pumped Nd:YLF laser based on DBMC technology

“…1). The controlled gain competition between the two near-parallel beams inside the slab guarantees stable TEM 00 mode operation at high pump powers, without inserting additional losses [15,16]. No cylindrical intracavity optics is needed to create the highly elliptical beams necessary with other techniques [14].…”