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Method for predicting junction temperature distribution in a high-power LD bar

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High power laser diodes (LDs) have emerged as the most promising pumping sources for solid state lasers and fiber lasers, and they have been widely used in communication applications, cosmetic and medical applications, material surface treatment, joining technologies, cutting technologies, and defense applications.  The junction temperature is one of the most important parameters in achieving optimal performance of a high power LD bar, determining the center wavelength, spectrum distribution, wall-plug efficiency, and reliability.  Thus, experimental and analytical determination of the junction temperature is critical for the proper operation of the diode as well as the development of the packaging design.

As higher optical power is demanded for advanced applications, more closely-spaced emitters with higher forward current are used in LD bars.  As a result, the junction temperature from the center to the edge emitters may have large variations, which makes the center wavelength and wall-plug efficiency of each emitter different from each other.

Several junction temperature measurement methods for low power LDs or light emitting diodes (LEDs) have been proposed, including techniques based on measurement of the thermal resistance, wavelength-shift, optical power output, and forward-voltage.  These methods are applicable only when the junction temperature is uniform.  Micro-Raman spectroscopy can be used to measure the junction temperature distribution by measuring multiple local temperatures.  In practice, it requires a complicated experimental setup and has limited accuracy.

A hybrid experimental/numerical method to predict the junction temperature distribution of a high power LD bar was proposed.

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