Tunable 3–6 THz Polariton Laser Exceeding 0.1 mW Average Output Power Based on Crystalline RbTiOPO 4

We report a diode-pumped, intracavity THz laser source based on stimulated polariton scattering in crystalline RbTiOPO4 using a surface-emitting configuration. The system was continuously tunable in four regions, from 3.05 to 3.16 THz, from 3.50 to 4.25 THz, from 4.57 to 4.75 THz, and from 5.40 to 5.98 THz. The laser delivered 124.7 μW average output power at 4.10 THz for only 6.0 W diode pump power at 808 nm, corresponding to a diode-to-THz conversion efficiency of 2.1 × 10
^-5
. The horizontal and vertical beam quality parameters were M
_H
²
<;1.6 and M
_V
²
<;1.1 and the linewidth of the terahertz field was 28 GHz at 4.10 THz. The results demonstrate that the surface-emitting configuration is a very efficient technique to produce high-power THz laser sources with frequency-tunable output suitable for real-world applications.