1. All-fiber coherent beam combining utilizing tapered fiber bundles with active phase stabilization.
Roey Zuitlin[1,2], Yariv Shamir, Benayahu Urbach, Danny Levy, Eyal Shekel, Yoav Sintov and Mark Shtaif
The fabrication and performance of highly efficient brightness-preserving tapered fiber bundles (TFBs) have proven to work reliably at high power levels when incoherent side-by-side addition of fiber lasers is performed [1-3]. While simplicity and ruggedness are the main advantages of the method, beam quality (BQ) is yet bounded by brightness conservation . Coherent beam combining (CBC), on the other hand, enables brightness enhancement along with power scaling. This method, however, is significantly more restrictive, as it requires the use of highly coherent sources in addition to phase and polarization control schemes . Recently, we have presented the potential of TFBs to coherently combine fiber lasers, when a laser source was split using a 50-50 coupler and coherently combined with the use of a TFB combiner . The advantage of using TFBs instead of NxN fused couplers as the combining device is twofold, since they are more efficient and suitable at higher power levels. Without active phase stabilization, the M2 fluctuated over time between the values 1.17 and 2.3, consistent with expected results of an in-phase and anti-phase CBC, respectively. In this work, we present our latest progress following the addition of an active phase stabilization scheme. Within our talk, we will present the BQ and power efficiency results and also discuss the possibility of splicing the TFB's output facet to a delivery fiber, as was previously reported in the case of incoherent beam combining .
2. Optical quality improvement of rare-earth doped silica layers by CO2 laser
Gil Atar, David Eger, Ariel Bruner, Bruno Sfez, Menachem Nathan
We investigate different types of structural defects in 20–30 lm thick Yb/Al-codoped fused silica layers on a pure fused silica substrate, and show that all types of structural defects can be treated in a single laser heat treatment. Laser-induced processes of defect elimination include diffusion of micro-voids amorphization of crystallites and roughness reduction via surface-tension-driven mass flow. The physical mechanisms for defect elimination are analyzed in terms of onset temperature and typical time of elimination. Results of such treatment include complete amorphization, reduction of surface roughness by an order of magnitude to about 15 nm, and a remarkable improvement of more than an order of magnitude in optical cross-transmittance. The treatment thus provides a possible route for producing lasers and high-power integrated optics components using silica-on-silica technology.
Optical Materials 34 (2012) 838–844
3. A robust All-fiber Q-Switched 1micron Yb3+ Fiber laser
Yoav Sintov, Sharone Goldring, Shaul Pearl, Eyal Lebiush, Bruno Sfez, Dror Malka, Zeev Zalevsky
An all fiber active Q-switched Yb doped fiber laser at 1µm is presented. The laser is composed of a ring resonator with an embedded all-fiber q-switch element, based on a null coupler with an attached Piezoelectric Transducer (PZT). The PZT is used as an acoustic actuator, for inducing longitudinal acoustic disturbance along the null coupler and causing light coupling between the null coupler's ports. A stable operation is achieved with an overall average output power of up to 270mWatt at a various pulse repetition rate (PRR), ranging from 10kHz to 35kHz and typical pulse energy of 30µJoule. In addition, a self-monitoring method is implemented by an embedded microcontroller, in order to maintain the Q-switch performance, in changing environmental conditions.