Ulrich Steegmüller

Visible lasers for mobile projection

Visible laser sources are attracting considerable interest to enable ultra-small, embedded laser scanning projection devices. We report recent progress on the development of red, green and blue semiconductor based laser sources. Red and blue colours are achieved by edge-emitting laserdiodes, whereas green uses frequency doubled optically pumped semiconductor lasers. Green lasers turned-out to be on the critical path for the technical and commercial success of laser displays. Because all current approaches are based on frequency doubling, the green source is the major contributor of cost, size and power consumption. Important parameters like size, efficiency, output power, beam quality, and modulation bandwidth are discussed.

Experimental study of the output dynamics of intracavity frequency doubled optically pumped semiconductor disk lasers

The dynamic behavior of the continuous wave output of an intracavity frequency doubled optically pumped semiconductor disk laser is described. These lasers typically exhibit stable emission. The reasons are found to be the tendency to single-mode operation and the high gain coupling of different modes due to an extremely short gain medium and the resonant periodic gain structure. A dependence of the fluctuation amplitude on gain decoupling of different fundamental modes is demonstrated. With the presented laser setup, more than 80% of conversion efficiency with respect to the available fundamental power has been achieved.

52.4: High Speed Green Frequency Converted Semiconductor Laser for Projection Displays

Recent progress on compact green laser for projection applications based on frequency doubled semiconductor structures will be presented. Avoiding external acousto- or electro-optical modulation for scanning laser displays, the green laser prototypes can be directly modulated in the 20–40MHz range.

MgO-doped PPLN with cascaded structure for intracavity frequency doubling of optically pumped semiconductor disk lasers

A magnesium-oxide doped periodically poled lithium-niobate with segments of cascaded poling periods as a nonlinear crystal for intracavity frequency doubling of an optically pumped semiconductor disk-laser to the green spectral range is presented. Results show temperature-dependent second harmonic generation and a maximum output power of 62 mW at 525 nm corresponding to a 24% conversion efficiency.