Then he moved to medical imaging and received the Doctorat es-Sciences degree from Paris University in the area of ultrasonic focusing for real-time medical imaging under the direction of Pierre Alais (1978).

In 1990 and founded the "Waves and Acoustics Laboratory" at ESPCI whose director he was and which became the Institut Langevin in 2009.

Fink pioneered the development of time-reversal mirrors[4] and Time Reversal Signal Processing.

He developed many applications of this concept from ultrasound therapy, medical imaging, non-destructive testing, underwater acoustics, seismic imaging, tactile objects, to electromagnetic telecommunications.

Six companies with close to 400 employees have been created from his research: Echosens,[5] Sensitive Object,[6] Supersonic Imagine,[7] Time Reversal Communications, Cardiawave,[8] and GreenerWave.