Thulium Laser

Thulium-based lasers have traditionally faced challenges in regulating the transition of thulium ions to different energy levels, or manifolds, during lasing. Achieving population inversion, in which excited ions outnumber ground state ions, is crucial for lasing. In the case of thulium, ions often get trapped in the 3F4 manifold, making this population inversion difficult or sometimes impossible to achieve. Current approaches to controlling these transitions have not been completely successful, leading to inefficient lasing. The main problems lie in managing the volumetric concentration of thulium doping and the duration of energy pulses. Current methods do not fully prevent the formation of a transparent gain medium at the pump wavelength when sufficient thulium ions become trapped in the 3F4 manifold.

Technology Description

This invention discloses a method of lasing thulium, which results in light emission at approximately 820 nm. This process involves transitions between different energy states (manifolds) within the thulium, specifically from the 3H4 to the 3H6. However, excited thulium ions also transition to the 3F4 manifold, where they become trapped and cannot participate in the lasing transition. This action potentially disables population inversion, which is crucial for lasing. However, by selecting the right crystal host and thulium doping concentration, pumping the thulium with short pulses, cooling the gain medium to low temperatures, stimulating emission from the 3F4 manifold, upconversion pumping the thulium to the 3H4 manifold, or transferring energy to a co-dopant, this problem can be mitigated. These methods help maintain population inversion and prevent the gain medium from becoming transparent at the pumping wavelength.