Double Tungstate Lasers: From Bulk Toward On-Chip Integrated Waveguide Devices

Abstract

It has been recognized that the monoclinic double tungstates KY(WO 4) 2 , KGd(WO 4) 2 , and KLu(WO 4) 2 possess a high potential as rare-earth-ion-doped solid-state laser materials, partly due to the high absorption and emission cross sections of rare-earth ions when doped into these materials. Besides, their high refractive indexes make these materials potentially suitable for applications that require optical gain and high power in integrated optics, with rather high integration density. We review the recent advances in the field of bulk lasers in these materials and present our work toward the demonstration of waveguide lasers and their integration with other optical structures on a chip.

Continuous-wave and Q-switched Tm-doped KY(WO_4)_2 planar waveguide laser at 184 µm

“…Waveguide lasers with their simple monolithic structure are attractive for integrated optical devices with the potential for on-chip integration [15]. The inherent advantage of waveguide lasers over conventional bulk lasers is the good overlap between the pump light and the laser mode, because both are constrained to propagate together in the narrow waveguide, leading to high intensities for relatively low power.…”

Continuous-wave and Q-switched operation of a compact, diode-pumped Yb^3+:KY(WO_4)_2 planar waveguide laser

“…Apart from the highly efficient and low threshold operation achievable with waveguide configurations, such laser devices are characterized by a simple monolithic laser structure that can be incorporated into practical integrated devices. Additionally, the double tungstates are particularly attractive for such applications due to their high refractive indices of ~2 [15]. A well-developed technique for producing high-quality crystalline planar waveguides with low propagation losses is liquid-phase epitaxy (LPE) [16].…”

Ultrafast laser inscribed Yb:KGd(WO_4)_2 and Yb:KY(WO_4)_2 channel waveguide lasers

“…Amongst them, the Yb-doped monoclinic potassium double tungstates, notably Yb:KGd(WO 4 ) 2 (Yb:KGdW) and Yb:KY(WO 4 ) 2 (Yb:KYW) [12,13] show particular promise for use as compact diode-pumped ultrashort pulse lasers [14]. The main disadvantage of these materials, as with any quasi-three-level laser system, is that the lower lasing level is thermally populated and thus high pump intensities with a good overlap between pump and lasing modes are required for low-threshold and efficient operation.…”