Hydrocarbon-free resonance transition 795 nm rubidium laser
Resonance transition rubidium laser operating on the 52P 1/2→52S1/2 transition with a hydrocarbon-free buffer gas is described. An extensive conceptual and numerical modeling study of the hydrocarbon-free rubidium laser is conducted. Prior demonstrations of alkali resonance transition lasers have used ethane as either the buffer gas or a buffer gas component to promote rapid fine-structure mixing. Evidence suggests that the alkali vapor reacts with the ethane producing carbon as one of the reaction products. This degrades long term laser reliability. Our experimental results with a "clean" helium-only buffer gas system pumped by a Ti:sapphire laser demonstrate all the advantages of the alkali laser, but without the reliability issues associated with the use of ethane. We further report a demonstration of a rubidium laser using a buffer gas consisting of pure 3He. Using isotopically enriched 3He gas yields enhanced mixing of the Rb fine-structure levels. This enables efficient lasing at reduced He buffer gas pressure, improved thermal management in high average power Rb lasers and enhanced power scaling potential of such systems. A diode-pumped alkali laser with output power of 150 W is demonstrated using commercial diode pump arrays with linewidths of ~0.5 nm, a regime requiring only modest linewidth control. We anticipate that this approach presents a new pathway to high average power lasers with good beam quality and high efficiency. Furthermore, collisional energy transfer leading to the ionization of active atoms is observed in an optically pumped Rb laser. Using a chopped Ti:sapphire laser as a pump source, their effects on the Rb laser are studied. A simple model is presented with numerical parameters gathered from published literature to explain our observations. Although these parasitic processes can strongly affect laser output, they do not appear to significantly impact the overall laser efficiency in the regime examined in this study.