Abstract: In a method and apparatus for synchronizing the output of two passively modelocked pulsed lasers, the output of each laser is sampled and delivered to two photodiodes, one for each laser. The output of the each photodiode is converted to a train of digital pulses having the pulse repetition frequency of each laser. The digital pulses are processed in a digital phase detector that generates from the digital pulses a first analog voltage representative of the phase difference at the photodiodes between corresponding pulses in each train. This analog voltage is summed with a second analog voltage representative of a desired phase relationship of the laser pulses at a target location remote from the photodiodes. The sum of the analog voltages provides an error signal that commands a device to adjust the length of the resonator of one of the lasers. When the error signal is minimized, pulses from each laser have the same repetition frequency and have the desired phase relationship at the target.

Abstract: Two stage implantable microphone devices suitable for use in hearing systems are provided. An implantable microphone device may include a housing including a diaphragm with the housing and diaphragm enclosing a chamber; a microphone coupled to the housing; and a vent connecting the microphone to the chamber. Vibrations of the diaphragm are transmitted through the chamber as a first stage and through the vent as a second stage to the microphone. The relative dimensions of the chamber and vent may be utilized to tune the frequency response and sensitivity of the device.