Laser diode bars break 400W barrier
Jenoptik Laserdiode, the German manufacturer of semiconductor lasers, has fabricated a laser diode bar that emits a record breaking 454 W of continuous wave (cw) infrared (940 nm) light. The result is around 100 W higher than the previous records of 364 W and 320 W that were reported by nLight Photonics and Bookham respectively last year.
Jenoptik's result was achieved with a 1cm-long, 2mm-high bar that was made at its new semiconductor fab, Jenoptik Diode Lab, in Berlin.
"It was just a plain vanilla semiconductor bar that we use in production, nothing special," explained Detlev Wolff from Jenoptik Laserdiode. "Compared to the regular diode product we simply changed the packaging to carry the larger current."
The water-cooled device emitted the record-breaking power when driven at a current of 580A. According to Wolff, the result is important because it shows that Jenoptik's semiconductor material is capable of being driven at high output powers without suffering catastrophic optical damage (COD) to its facets.
"The question for us is what is the weak point of a diode laser. This result shows that it is not the facet," said Wolff. "What we see is the device is thermally limited rather than suffering from COD. This means that it is not the semiconductor bar that is limiting the next level in performance but it's the packaging and heat-sinking."
The new result means that there is now an even larger gap between the performance of laboratory demonstrations and commercial devices. The highest power bars on the market currently deliver around 100-120 W CW and Wolff says this figure is unlikely to rise for sometime while manufacturers concentrate on improving the lifetime of devices rather than output power.
"What we see right now is a race towards a new commonly accepted power level. I think that this will be probably 120 W and will stay for the next few years," Wolff told Optics.org. "The reason is that our industrial customers ideally want to have a 7-year lifetime [equivalent to 40,000 h] and we think that this is possible at 120 W."
Author
Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.
