Jörg Heerlein

High-power IR laser in SMT package

Laser dies in an optical power range of 1-3 Watts are widely assembled in popular TO- packages. TO-packages suffer from high thermal resistance and limited output power. Bad thermal contact between circuit boards and TO-devices can cause overheating of laser chips, significantly reducing the operating life time. We developed a compact high heat-load SMT package for an optical power up to 7 Watts in CW operation with good life time results. The new package for high power laser chips combines highly efficient heat dissipation with Surface-mount technology. A Direct-Bonded-Copper (DBC) substrate acts as a base plate for the laser chip and heat sink. The attached frame is used for electrical contacting and acts as beam reflector where the laser light is reflected at a 45° mirror. In the application the DBC base plate of the SMT-Laser is directly soldered to a Metal-Core-PCB by reflow soldering. The overall thermal resistance from laser chip to the bottom of a MC-PCB was measured as low as 2.5 K/W. The device placement process can be operated by modern high-speed mounting equipment. The direct link between device and MC-PCB allows CW laser operation up to 6-7 watts at wavelengths of 808nm to 940nm without facing any overheating symptom like thermal roll over. The device is suitable for CW and QCW operation. In pulsed operation short rise and fall times of <2ns have been demonstrated. New application fields like infrared illumination for sensing purposes in the automotive industry and 3D imaging systems could be opened by this new technology.

Near-infrared power LED for emerging security and defence applications

High-power near-Infrared LED (IRED) are gaining more and more interest in a large variety of commercial, industrial and military applications. IRED are based on InAlGaAs semiconductor structures which cover a spectral range of 780 nm to 1100 nm. This wavelength range is supposed to be not visible to the human eye. But, depending on the radiant intensity and wavelength, a reddish glow is still evident. Therefore, in covert applications longer wavelength of 940 nm or even higher are preferred due to the much lower sensitivity of the human eye compared to 850 nm. On the other hand at around 850 nm the spectral sensitivity of CMOS or CCD cameras or other silicon based photo detectors is at its maximum. We present the latest developments in high power IRED in the quest for more than 1 W from a single 1mm2 die.