Novel development platform, integrating laser diodes with drivers and control electronics

We have qualified a new laser mount at FBH, which allows to mount laser diodes together with integrated drive and control circuitry onto one compact platform. The laser mount consists of a 1 to 3 mm thick copper plate with a printed circuit board on top. Laser diodes are bonded directly to the copper plate by removing a small part of the Printed Circuit Board (PCB) material in the center of the mount. We call the area where the PCB material is removed down to copper plate “chip pocket”. It combines the advantage of bonding the laser diode directly to the copper heat sink for efficient spreading and removing the heat with design flexibility of the circuit layout – thus suited for various applications – on the top side of the PCB.

The laser diodes are bonded inside the chip pocket using a low-melting solder (<200 °C) or an electrically conductive adhesive. They are subsequently contacted to the PCB by wire bonding. Flexible designs can be implemented in cooperation with the PCB manufacturer, allowing variable sizes and positions of the chip pocket on the PCB. The high degree of design flexibility can also be used to integrate optical components such as micro lenses for beam shaping in order to merge them to optical microbanks.

Devices such as drivers with GaN transistors to control short laser pulses, voltage divider circuits for multi-segment laser diodes as well as conducting paths for sensors and Peltier elements are implemented on top of the PCB. For applications that require short-pulse lasers it is important that the inductance of the bond connections can be strongly reduced by an optimal design of the chip pocket combined with an adapted circuit layout.

Several types of driver circuits for LiDAR applications with pulse lengths from 1 ns and peak currents of max. I = 400 A have been realized so far. And laser diodes were bonded in p-down as well as in p-up configuration.

The geometry of the laser mount can be modified according to the respective application and matching the circuit layout. It therefore provides an ideal low-cost development platform for complex laser sources, suited for short pulse lasers (LiDAR) and multi-segment laser diodes.

The development of the laser mounts was partly funded by the Federal Ministry for Economic Affairs and Energy (BMWi) within the miniLIDAR project under grant number 50RA1924 and the German Federal Ministry for Education and Research (BMBF) under grant number 13N14023,26 within the funding initiative EffiLAS/PLUS.