Ho:YAG laser intracavity pumped by a diode-pumped Tm:YLF laser

Abstract

We report a compact Ho:YAG laser that is intracavity pumped by a diode-pumped Tm:YLF laser. Both lasers exhibit pulse mode behavior. Operating both crystals at room temperature (25 degrees C), we obtained 1.6 W of average output at 2.09 microm from the Ho:YAG laser for 15.4 W of diode power incident upon the Tm:YLF rod and a slope efficiency of 21%.

Intra-cavity side-pumped Ho:YAG laser

“…Such a strong absorption, even when partially saturated, should dominate any other losses in the thulium cavity and hence allow efficient pumping of the Ho:YAG slab. Previous reports of intracavity pumping have shown that the thulium wavelength can shift to avoid the strong holmium absorption, and in the only other previous report of Tm:YLF intracavity pumping Ho:YAG, [17], the Tm:YLF laser shifted to ~1.95µm, see figure 3. In order to control this effect, and attempt to push operation to the stronger holmium absorption minimum around 1.92µm, we employed high-pass edge mirrors to form the thulium laser cavity.…”

“…Although pumping of a holmium laser by placing it inside the cavity of a thulium laser has been demonstrated by several authors, [8,16,17], if the crystals share a common cavity, [8,16], the thermal lensing in both crystals can seriously affect the beam quality of the Ho:YAG output. To tackle this problem, Schellhorn et al, [17], introduced a novel configuration whereby the Ho:YAG laser cavity was partly decoupled from the Tm:YLF cavity by polarization. In our design the two cavities are fully decoupled through the use of side-pumping, which has the further advantage of much less stringent requirements on the beam quality for the thulium pump laser.…”

2-μm high-power multiple-frequency single-mode Q-switched Ho:YLF laser for DIAL application

“…However, the efficiency of these systems is usually limited because of the deleterious effect of upconversion losses at high pump level and reverse transfer between the Tm and Ho ions [11] which produce a large thermal load of the crystal and practically prevent an operation at PRF larger than few tens of Hertz. Further work has then focussed on direct in-band pumping of the Ho 5 I 7 manifold by Tm:YLF solid-state laser [12,13] or more recently by suitable laser diodes at 1.9 lm [14] or via a diode-pumped secondary laser source, e.g., a thulium (Tm) fiber laser [15]. Even if the Tm-fiber lasers are diode-pumped in the 790 nm band leading to an a priori large quantum defect, the electrical to optical efficiency (EOE) can be significantly enhanced by the crossrelaxation process where one photon can excite two Tm ions in the 3 H 4 level [11,16].…”

High repetition rate, tunable, Q-switched diode pumped Tm:YLF laser

“…Ability to tune the output wavelength is another advantage, which let ones to pump other lasers such as Cr:ZnSe [34][35][36][37] or holmium−doped crystalline lasers [38][39][40][41][42][43] etc.…”