Measuring photodarkening from single-mode ytterbium doped silica fibers

Abstract

Photodarkening is recognized as a potentially important limiting factor on the lifetime and reliability of many Yb-doped fiber lasers and amplifiers. In particular, a photodarkening process attributed to the formation of photoinduced structural transformations can induce excess loss in the doped glass core of the fiber, resulting in reduced output power efficiency. Yet, quantifiable measurement techniques of this phenomenon have been scarce in the literature to date. Here we present a fast, simple and repeatable method to measure and compare the photodarkening rate caused by the formation of photoinduced structural transformations from Yb-doped single-mode fibers. The method relies on quantifying observations of transmission changes at visible wavelengths as an indicative measure of photodarkening at the signal wavelengths. Preliminary measurement results are presented supporting the utility of the technique for benchmarking the photodarkening behavior of different Yb-doped fibers.

Yb Fiber Amplifier at 972.5 nm with Frequency Quadrupling to 243.1 nm

“…To mitigate these effects, we angle polish the ends of the gain fiber and use bandpass filters (FWHM=4 nm) to remove ASE originating from both the fiber amplifier and the TA [20]. The high inversion in the fiber can also lead to photodarkening -a poorly understood decrease in the optical transmission of gain fibers which degrades performance [22]. Mitigation of this effect is possible by codoping the gain fiber with phosphorous or cerium [23,24].…”

Measurement of photodarkening in Yb-doped aluminosilicate fibres at elevated temperature

“…The induced loss is proportional to the inversion level of the Yb 3+ ions, [3] and also depends on host material [4][5][6]. Measurement of photodarkening, in most cases, relies on monitoring transmitted power of a visible probe beam located far away from the Yb-absorption band during pump irradiation [1,6]. A loss in Yb band can be scaled from the loss at the probe wavelength due to similar spectral shape of the induced loss in a wide range of Yb fibers [1].…”

“…Measurement of photodarkening, in most cases, relies on monitoring transmitted power of a visible probe beam located far away from the Yb-absorption band during pump irradiation [1,6]. A loss in Yb band can be scaled from the loss at the probe wavelength due to similar spectral shape of the induced loss in a wide range of Yb fibers [1]. However, thermal treatment sometimes results in distortion in the loss spectrum, which invalidates this assumption [7].…”

Triple and Double Photons Absorption Process and Down-Conversion Laser Emitting Investigation of Er-Ion Doped Microsphere

“…the temporal confinement of light) [8][9][10], but also the light is spatially confined, exhibiting small mode volume and high energy density of the optical mode .The small mode volume and long photon storage time can be used for a variety of studies ranging from fundamental physics such as cavity Quantum Electrodynamics [11] to more applied areas nonlinear optical studies [9,10], high-sensitivity transducers for biochemical sensing [12], low threshold light emission and narrow line-width lasers [8], as strong resonant buildup of energy in micro-scale volumes significantly reduces the threshold for light emission to occur. Silica is good host for some rare earth ions including Er (erbium), Yb (ytterbium), Tm (thulium), Ho (holmium) [7,13,14] etc. When silica microspheres are doped with certain number of rare-earth ions, light can be emitted by coupling pump light source with a tapered fiber [15,16].…”