Why do other manufactures quote lower life times on their diode bars?

Diode bars (AKA as monolithic laser diode arrays) full of multiple emitters arranged in parallel in one crystal. Because of the high heat density in the junction area and strong thermal crosstalk between the emitters comprising the bars diode arrays must mounte on copper with soft solder (Indium) and water-coolling. High-speed and high pressure water flow through tiny gold coated channels in the copper (called micro-channel coolers) provides aggressive cooling.

However the water in the system must keep extremely clean and PH neutral as these channels are prone to failure due to cavitation and erosion in a relatively short period of time. Keeping water quality to the specification is extremely challenging task in any, especially in industrial, environment. Copper heatsink and diode bar semiconductor are very dissimilar materials, including coefficient of thermal expansion. Under real world operating conditions, frequent on-off cycles. The performance of bars tends to deteriorate much faster than under constant driving current which bar manufacturers use mostly to characterize their devices.

Why do other manufactures quote lower life times on their diode bars?

The other source of frequent bars’ failure is in the semiconductor diode bar itself; lifetime of the bar is usually determine by the reliability of its “weakest” emitter. In order to improve performance and boost heatsinking bars are often get attache to micro-channel coolers with high heat conductive soft solder indium.  Under high driving current operation indium know to migrate through bar metallization into semiconductor material thus causing its sudden instantaneous failure.

Many manufacturers of diode bars pro rate the warranty based on hours used. IPG have always used single emitter diode laser pumps manufactured entirely in-house. These mounte on a heat sink with the same coefficient of thermal expansion as the diode chip. IPG uses telecom-qualified hard solder which is free of electro-migration defects. Depending upon the size of the fiber laser, IPG diodes are either air-coolling. With high speed fans or are water-coolling through stainless steel pipes beneath the heat sink.

So there is no direct contact with water coolant.  And the diode light delivery via fiber and delivery directly to the active medium and spliced thus eliminating. An air to active medium interface that can be a source of contamination. The life of the single emitter diodes directly relate to the current they are operating at. All industrial IPG fiber laser diodes are run at a current level where the predicted end of life (MTBF) is > 100,000 hours of operation. IPG Photonics diodes are not pro-rated and are covered for the complete warranty period of the fiber laser or amplifier.