Narrowing spectral linewidth in passively mode-locked solid-state lasers.

A novel scheme to realize a mode-locked laser with a narrow spectral linewidth is demonstrated by exploiting a reflected Fabry-Perot (FP) cavity to introduce an intense FP effect. Stable continuous-wave mode-locked operation is achieved with the repetition rate of 48 MHz and the maximum average output power of 2.6 W under an incident pump power of 11.9 W. The mode-locked pulse width is systematically investigated by varying the optical thickness of the reflected FP cavity. The pulse duration is experimentally found to be in a range of 0.8 to 2.6 ns. The experimental results reveal that the reflected FP cavity is the key factor leading to the pulse generation in the nanosecond regime. This Letter is believed to provide a promising method for generating optical pulses with narrow spectral linewidths.

Compact coupling scheme to achieve the synchronously dual self-mode-locked operation with a 35.2 THz optical beating.

A synchronously dual self-mode-locked (SML) operation at 946 and 1064 nm is experimentally accomplished by using a compact coupling scheme to obtain the optical beating frequency up to 35.2 THz. The SML emissions at 946 and 1064 nm are established by a monolithic Nd:YAG cavity and a Nd:YVO4 crystal in a flat-flat cavity, respectively. Two gain media are butt adjoined to be longitudinally pumped by a single laser diode. The monolithic Nd:YAG crystal is used not only as the 946 nm laser cavity, but also as the output coupler of the Nd:YVO4 1064 nm laser. More importantly, the output surface of the monolithic Nd:YAG laser is coated to generate the optical feedback for the synchronization of the dual SML operation. At a pump power of 10.7 W, the output powers at 1064 and 946 nm can simultaneously reach 1.5 W by controlling the focal position of the pump waist.

Transition-metal-free carbofluorination of TBS-protected nitrogen-containing cyclic enynols: synthesis of fluorinated azabicycles.

The synthesis of fluorinated azabicycles from tert-butyldimethylsilyl-protected N-containing cyclic enynols using inexpensive BF3·OEt2 is described. In this reaction, BF3 reacts as both the Lewis acid and the fluoride source for cyclization/fluorination of the TBS-protected cyclic N-containing enynols. The method provides an easy access to fluorinated azabicycles where a new C(sp(2))-F bond and a new bicyclic skeleton are generated at ambient temperature within 1-13 min under metal-free reaction conditions.