A backside-emission packaging architecture for multibeam laser Doppler vibrometer PICs (Invited Paper)

Laser Doppler vibrometers (LDVs) measure surface vibrations using the Doppler shift of reflected light and can be integrated into photonic integrated circuits (PICs). Multibeam LDV PICs enable simultaneous sensing at many points, but scaling to high channel counts is limited by the large number of electrical pads required. These pads consume chip area, complicate routing, and increase cost. We introduce a flip chip packaging approach to overcome this challenge. The LDV beams exit from the polished backside of the PIC, while the topside uses a ball grid array for electrical connections. A glass interposer redistributes the dense pads to larger external interfaces. This design improves integration density and manufacturability. We demonstrate a device with 16 beams and 60 pads, enabling low crosstalk, multi point vibration measurements.