A light concentrator includes a luminescent concentrator and a gain medium. The luminescent concentrator includes a semiconductor material and the semiconductor material absorbs first photons. The first photons have energy greater than or equal to a threshold energy, and the semiconductor material emits second photons through a spontaneous emission process where the second photons have less energy than the first photons. The gain medium is optically coupled to the luminescent concentrator to receive the second photons. The gain medium absorbs the second photons, and in response to absorbing the second photons, the gain medium emits third photons through a stimulated emission process. The third photons have less energy than the second photons.

The system and method for reducing Yb to Er bottlenecking in a single frequency Er:Yb-doped fiber laser amplifier. The system is pumped off peak at about 935-955 nm. The off-peak pumping reduces bottlenecking and increases the optical and slope efficiency of the system by about 10% as compared to an EYDFA system pumped on-peak.

An optical resonator for a medical laser system is provided. The optical resonator comprises a lasing medium, an optical pump, and a high-reflective (HR) and an optical coupling (OC) reflector. The HR and OC reflectors are disposed symmetrically relative to the lasing medium and the HR mirror, the OC mirror, or both the HR mirror and the OC mirror are flat mirrors. The optical resonator also includes a doped insert in which the lasing medium is disposed.

A power amplifier module (PAM) includes an input that receives a first beam at a signal wavelength (.sub.s) from a seeder laser source (SLS) which includes previous stages of a multi-stage fiber-based optical amplifier chain. The PAM includes an optical pump laser (OPL) that generates an optical pump beam at a pump wavelength (.sub.p). The PAM includes a fiber-optic output configured to fusion splice to a large-core rare-earth doped power amplifier fiber (PAF). The PAM includes a wavelength-division-multiplexer (WDM) configured to spectrally combine the first beam with the optical pump beam into a single combined beam that the WDM outputs into a core of the PAF via the fiber-optic output. The .sub.p is an in-band wavelength at which the optical pump beam emitted by the OPL optically pumps the core such that the PAF, in response to receiving the combined beam, emits an output beam at wavelength>2 m.