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17 Jun 2002
German researchers have created the first conventional diode lasers to emit at 560 nm.
Courtesy of Opto & Laser Europe (OLE) magazine
Developed by Matthias Klude and colleagues at Bremen University, the diode lasers' wavelength of 560 nm corresponds to the attenuation minimum of polymethyl methacrylate.
This means these novel sources could be ideal for illuminating future datacoms networks based on plastic optical fiber. Until now, no diodes had lased between the shortest GaP-based sources at 614 nm and the longest ZnSe-based devices at 535 nm.
Klude and colleagues had previously made a quantum-dot device emitting at the same wavelength in the yellow-green spectral region. However, this laser diode is the first to operate at room temperature with continuous-wave emission using the conventional ZnSe-on-GaAs structure. Klude says that the team has recently measured 1 W of output from a pulsed version of the device.
Although the laser's lifetime is currently only 1 min, Klude is confident that this, along with the threshold current and operating voltage, can be improved.
"These devices were made in the most rudimentary way. To be honest, we were surprised to see them operating. Improvements would result from facet coating, top-down mounting and ridge waveguide processing, but for a university-based research project this is rather difficult. A collaboration with industry would certainly help," he said.
Klude adds that the fabrication of both quantum-dot and quantum-well lasers gives the group a unique opportunity to compare the two devices under identical conditions. So far, the group has found that the characteristics of the quantum-well laser are an order of magnitude better than that of the quantum-dot device.
As well as the obvious application in datacoms, green-yellow diodes could find other uses in displays technology.
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