München 2004 – scientific programme

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Q: Quantenoptik und Photonik

Q 19: Poster Festkörper- und Halbleiterlaser

Q 19.5: Poster

Tuesday, March 23, 2004, 14:00–16:00, Schellingstr. 3

Scaling the single mode output power of tapered amplifier lasers by coherent addition — •Rudolf Neuhaus, Marvin Kurz, Frank Lison, and Wilhelm Kaenders — TOPTICA Photonics AG, Fraunhoferstr. 14, 82152 Martinsried/München

We describe a laser system in which the output of two tapered amplifier systems is coherently added. The tapered amplifiers are seeded by a common grating stabilized external cavity diode laser, generating two beams with identical properties (single mode, narrow linewidth, low noise) and similar beam profile. Their coherent addition requires the measurement of and control over the relative phase between them. The coherent addition is realized using two orthogonal [1] as well as two identical polarizations and both approaches are compared. Control over the relative phase can be attained with a piezo mounted beam combiner as well as frequency and/or current modulation of the master or one of the two amplifiers.

The coherent addition of two orthogonally polarized beams proved to be the most practical and efficient method resulting in a combined beam that holds up to 1.9 times the power of a single beam. Behind a single mode fiber even more than twice the power of a single fiber coupled tapered amplifier system is achieved. A very high degree of coherence is maintained (γ=0.969).

Using the latest generation of tapered amplifier chips, an output power of more than 2 W can be reached by maintaining a high beam quality (M² ≤ 1.3). Being scalable, this approach enables higher power laser sources with the same favourable properties.

[1] Singer et al., Opt. Comm. 218, 371-377 (2003)