The Brit Awards
London UK
Company: Coherent
A new technology from Coherent Inc., Optically Pumped Semiconductor Laser (OPSL) technology, promises to deliver unique wavelengths and power scaling to provide the entertainment industries with a compact, robust, all solid-state platform. Coherent Inc., has recently released two high-power OPSL’s delivering 5W of green at 532nm and 3W of yellow at 577nm. Furthermore, they have demonstrated high-power output at 460nm and will soon release a 2W OPSL at 460nm.
Optically Pumped Semiconductor Lasers belong to a class of lasers known as Vertical Cavity Surface-Emitting Lasers or VCSEL’s. In a VCSEL, the light is emitted perpendicular to the junction and out the face of the diode chip. Electrically pumping a VCSEL, as with standard laser diodes, unfortunately does not yield high-output because there’s no way to flood the large area with charge carriers without using extended electrodes that would introduce too much loss. However, this problem can be avoided by optically pumping the device to create the charge carriers. This is the basis of the Coherent OPSL technology.
The main elements of an OPSL: Pump light from a direct coupled single emitter or fiber-coupled laser diode array is re-imaged into the front surface of the OPSL chip. This monolithic III-V semiconductor chip contains layers of tertiary quantum wells (InGaAs) alternated between binary (GaAs) layers. These binary layers are optimized to efficiently absorb pump radiation, resulting in a high population of charge carriers. This leads to population inversion and recombination in the quantum wells, which emit at a wavelength determined by the stoichiometry and physical dimensions of the quantum well structures. Behind these absorption/emission layers are several alternating high index and low index layers that act as a low-loss DBR (Distributed Bragg Reflector) mirror optimized for the specific OPSL output wavelength. The OPSL cavity is completed by the addition of external optics, a birefringent filter, BRF, for wavelength stability and frequency doubling to convert the fundamental IR laser radiation to visible light.
OPSL’s can operate over a very broad pump wavelength range. All that is required is that the pump diode wavelength exceed the bandgap for the OPSL absorption layers. Another significant OPS advantage is its longitudinal mode characteristics, which results in low noise in the frequency-doubled output. The most important benefit of OPSL technology is the ability to readily customize it over a wide range of output wavelengths. This uniquely enables OPSL’s to be designed to fit the application instead of vice versa.
Coherent Inc., has released the Taipan series of high-power OPSL’s, as part of the Venom family of all solid state laser products for Entertainment. The Taipan series of lasers includes Taipan-530-5 (5W at 532nm), and Taipan-577-3 (3W at 577nm).
