Investigation On High Power Conversion Efficiency Laser Diodes

The semiconductor laser diodes have many advantages,such as high efficiency,high reliability,compact sizes,which were widely used in many kinds of applications,such as in materials processing,medical industrial,aerospace,pumping solid-state lasers and fiber lasers.With the development of laser diodes,there is an increasing demand of high output power,high efficiency,high reliability and high brightness performance.Thus,it is necessary and meaningful to study and develop the high efficiency laser diodes chips independently.As a photoelectric device,the power conversion efficiency(PCE)is one of the most important parameters to assess the performance of laser diodes.High efficiency was proved to reduce the waste heating of the active region to achieve the excellent performances by many research institutes.Furthermore,High efficiency laser diodes had many advantages,such as high output power,high reliability,small and compact size.The PCE was closely related to the operating temperature of laser diodes.To obtain the high efficiency and find the factors restricting the further promotion of efficiency,the following research work has been done:(1)In this paper,efficiency analysis was demonstrated through study of the laser power,threshold current,slope efficiency,voltage and series resistance under different temperature from-40 ℃ to 25 ℃.(2)In order to improve the efficiency of 808 nm laser diodes,the following parameters must be considered,such as joule heating,carrier leakage,spontaneous radiation loss,interface voltage defect and internal absorption loss.The experimental and theoretical results indicate that the carrier leakage is the dominant factor to low PCE of the laser diodes,which means that it is necessary to optimize the epitaxial structure so as to reduce the carrier leakage at the room temperature.To obtain the high power and high efficiency,the epitaxial structure was optimized.We analyzed the effects of five kinds of loss path of the input power energy,which can provide guidance for further improving the performance of laser diodes.(3)According to the experimental results,we fabricated the 808 nm laser chips with a high PCE under the operating temperature of 25 ℃,the 70% PCE was observed for the laser bar.For the 976 nm laser bar,the maximum PCEs are 72% and 74% at the operating temperature of 25 ℃ and 15 ℃.