Chenhui Peng

A high power light emitting diode module for projection display application

Light emitting diode (LED) has numerous advantages such as long lifetime, large color gamut, small size and the absence of mercury vapor. In recent years, there has been recognition that LED could be an alternative light source for projection display application. In this work, dielectric compound parabolic concentrators (CPCs) were designed and optimized for multiple-LED array packaging structure for projection display application. The performance of rectangular CPC was studied and compared to theoretical simulations. Rectangular CPC was fabricated as the collector and collimator. A high power green LED module combined with rectangular CPC was fabricated and its performance was characterized. More than 90% light emitted by multiple-LED array can be collected by the CPC and transmit within the designed angle. A high power of 2.09W and a high luminous flux of 800 lm were obtained.

RGB High Brightness LED Modules for Projection Display Application

Light-emitting diodes (LEDs) have numerous advantages, such as long lifetime, large color gamut, small size, and absence of mercury vapor. In recent years, there has been recognition that high brightness LED could be an alternative light source for projection display application. In this work, dielectric compound parabolic concentrators (CPCs) were designed and optimized for multiple-LED array package for projection display application. The performance of rectangular CPC was studied and compared to theoretical simulations. More than 85% light, emitted by multiple-LED arrays, can be collected by the CPC and transmitted within the designed angle. A rectangular CPC was fabricated as the collector and collimator. The CPC was integrated with multiple-LED array package, and RGB high brightness LED modules with rectangular CPCs were fabricated and their performances were characterized.

A new package structure for high power single emitter semiconductor lasers

High power semiconductor lasers have found increased applications in pumping solid state or fiber laser systems for industrial, military and medical applications as well as direct material processing applications. The reliability requirement for high power semiconductor lasers has been increased in recent years and it has been proven that indium-free packaging is one of the most effective ways in improving lifetime. The performance including reliability of high power semiconductor lasers is highly depended on the package structure. We have designed a new package structure for high power single emitter semiconductor lasers which is called F-mount. In contrast to traditional single emitter package structures, the F-mount offers indium-free packaging while improving or at least not sacrificing the thermal management. The heat sink of this new structure is insulated and easy for system integration. Finite element numerical analysis was used to compare the thermal resistance between F-mount structure and traditional structure. It was found that F-mount has high power and high electrical-to-output efficiency than the traditional structure. Lifetime testing was conducted on the F-mount devices and it was found that there was no obvious degradation in power over 7000 hours.

Packaging of high power semiconductor laser arrays using a novel macro-channel cooler

High power semiconductor laser arrays have been widely used in many fields, such as pumping solid state laser aerospace, industry, medicine and display. For many applications, high power semiconductor lasers operating quasi-continuous wave (QCW) mode are demanded. For QCW laser, the output peak power is higher and average power is low. Therefore, the transient thermal density is very high. The most common method of removing the large amounts of waste heat in a semiconductor laser package is by using commercially-available copper micro-channel coolers (MCC). However, due to the coefficient of thermal expansion (CTE) mismatching between copper and laser chip, hard-solder cannot be directly used. On the other hand, indium solder has the problem of electro-thermal migration when the temperature grads were high in QCW mode. Furthermore, copper material is susceptible to erosion and corrosion. To overcome these hurdles in many applications, a novel macro channel cooler (MaCC) was presented in this work. The thermal behavior of MaCC-packaged high power semiconductor laser arrays in QCW mode was studied using finite element analysis (FEA). A high power of >250W QCW semiconductor laser array/bar using hard solder was fabricated. The performances of laser arrays, including output power, slope efficiency, threshold, conversion efficiency, spectral width, near field, lifetime etc. were characterized. The measured results indicated that the output power of a MaCC- packaged high power semiconductor laser array was very close to that of copper micro-channel cooler. Based on MaCC-packaged single laser array/bar, multiple-bar stack and two dimension area array lasers with output powers of several kilowatts and several tens of kilowatts were fabricated.

A new continuous wave 2500W semiconductor laser vertical stack

With the increasing applications of high power semiconductor lasers in industrial, advanced manufacturing, military, aerospace, medical systems, display, entertainment. etc., semiconductor lasers with high power and high performances are required. The performance of semiconductor lasers is greatly affected by packaging structure, packaging process and beam shaping. In this work, a high power semiconductor laser vertical stack was successfully fabricated. A series of techniques such as spectrum control and beam control were used to achieve marrow spectrum and high beam quality. The performances of the semiconductor laser vertical stack were characterized. A high power of 2500 W, a narrow spectrum of 3.11 nm and an excellent rectangular beam shape were obtained. The lifetime of the vertical stack laser was tested as well.

Light collection systems for multiple LED arrays

Light emitting diode (LED) has numerous advantages such as long lifetime, large color gamut, small size and the absence of mercury vapor and thus there has been recognition that LED could be an alternative light source for projection display application. Due to its compact size, LED is a very attractive RGB light source for portable projectors. To improve the brightness of the projector, it is very critical to improve the light collection efficiency of the RGB LED light sources. In this work, traditional compound parabolic concentrator (CPC) was designed and its performance was studied. The CPC has a high collection efficiency, but its size is too bulky to be used in the portable projectors. Hence, a freeform collection system was designed and optimized to gain a compact size which can be used in the portable projectors. After optimization, it has a collection efficiency of 85%, slightly lower than that of the traditional CPC. But its diameter of the output aperture is 13.4 mm, 36% smaller than that of the traditional CPC and its length is 25 mm, 58% shorter than that of the traditional CPC. Meanwhile, the divergence angle of the freeform collection system is ± 10 ° which is smaller than that of the designed traditional CPC. Hence, the freeform collection system may be used as the collimator in the portable projection display application.