Diode-pumped doubled Nd:YAG laser generates 49 mW of 473-nm light
Researchers at the Optoelectronics Research Centre (ORC, Southampton, England) have demonstrated a quasi-phase-matched, frequency-doubled diode-pumped Nd:YAG laser that produces 49 mW of blue (473-nm) light. Frequency doubling is achieved using periodically poled lithium niobate. The Nd:YAG laser is longitudinally pumped by a beam-shaped 20-W CW diode bar and produces a polarized output u¥to 1.5 W at 946 nm. According to David Hanna, deputy director of the ORC, the center`s beam-shaping technique produces the tightly focused beam necessary to effectively end-pum¥the Nd:YAG crystal for operation at the 946-nm transition. The second-harmonic output power of 49 mW was generated with an input power of 1.07 W, representing a conversion efficiency of about 4.6%, reportedly the highest value achieved for blue-light generation in bulk periodically poled materials. Use of a quasi-phase-matched nonlinear material to frequency double the Nd:YAG laser output allows noncritical phase-matching as well as enabling access to higher nonlinear coefficients as compared to the more commonly used birefringent phase-matching. Hanna believes there are good prospects for further increasing the CW blue output power by fabricating linear gratings and by scaling u¥the output power of the 946-nm Nd:YAG laser; intracavity frequency doubling also offers a prospective route to increased conversion efficiency.
