Investigation on the performance of high power long pulse laser diode arrays for hair removal and illumination

Abstract

By designing a lightweight and compact stacked bar package, we can achieve high-power, high-brightness, and high-stability pulse laser output. The laser diode package consists of eight 1cm high power laser bars, which are bonded between two copper-tungsten heat sinks with AuSn hard solder like a sandwich. These sandwiches are bonded in a second soldering step on a backplane macro-channel cooler. The package structure is very compact and lightweight. We can achieve different frequency, pulse width, duty cycle combinations, which easily allows to adapt to different applications. In this paper, the performance of 808nm and 940nm laser bars is verified under different conditions: The pulse width is varied from 5 to 300ms, and the frequency range is between 1Hz to 10Hz. Resulting duty cycles range from 10% to 40%. In addition this structure can combine two or more wavelengths (808nm and 940nm, 760 and 1060 optional). We achieve 1788W under the condition of 5ms, 10%DC, 200A. This compact and powerful 2D diode laser array with mixed wavelengths is very suitable for laser hair removal. It can not only fully act on the melanin of the hair follicle, but also coagulate the micro vessels around the hair follicle to cut off the blood supply of the hair follicle. With the right combination of wavelength, the penetration depth and absorbtion characteristics can be tailored to the different skin types from white to dark skin, avoiding skin irritation and pain. For pulsed pumping applications or far field illumination, FAC lenses can be applied to allow for best beam brightness. The package can be designed from single bar to 12 bars, depending of the power demand for the individual applications. Dense packaging of more than one stack in one laser unit allows high application power of multiple kW in a compact handpiece design for hair removal.