MOPA - Implementation of a hybrid diode laser micro-optical system with high output power and excellent beam quality

Diode lasers - compared to other laser devices - are characterised by their compact size, their excellent conversion efficiency, and by a prospective low cost production. In general, however, diode lasers presuppose a trade-off between possible beam quality

and achievable output power. Though, realising a hybrid MOPA (Master Oscillator Power Amplifier) device, a narrow spectral bandwidth diode laser system with high output power and excellent beam quality can be obtained.

The hybrid MOPA consists of two diode lasers, coupled through optical components. The master oscillator is a DFB oder DBR diode laser with near diffraction-limited beam profile und narrow-band emission. Under these premises, the master oscillator's output power is limited to less than one watt. To make higher output ranges accessible, the light is coupled into an optical amplifier, which retains the beam quality virtually unchanged. Merely about 100 mW output power of the master oscillator coupled into the power amplifier is sufficient to achieve a total output power of the MOPA system of several watts. In this power range, the MOPA system features wavelength and mode stability.

Within the scope of a ZEMI cooperation (FBH, BESSY) a prototype has been developed, where all components, that is laser diodes and coupling optics, are integrated on a micro-optical bench. Fine adjustment of the coupling lens, requiring tolerances of about one µm, is realised applying deformable lens holders made with LIGA technology. The prototype has three watt output power at 1060 nm (two watt in single mode operation).

The hybrid MOPA system figured here has the potential to combine high output power with excellent beam quality and narrow spectral bandwidth. The innovative concept using deformable lens holder and mounting on a micro-optical bench has promisimg advantages compared to other laser types - mainly compact und cost-efficient realisation. Such MOPA systems can be used in several fields, e.g. in spectroscopy, medical applications, communication sytems, or display technology.

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