Frequency response of a Fabry-Perot interferometer used as a frequency discriminator

Abstmt-This paper concerns the dynamic response of optical interferometers to frequency modulated laser fields. It shows a filtering effect as weU as epnversion to amplitude modulation. The Fourier frequency responses of a Fpbry-Perot interferometer used as an optical frequency discriminator are theoretically derived and experimentally verified. These frequency responses differ when considering reflected or transmitted beams. They also depend greatly on the laser detuning from the fringe peak of the interferometer. I. INTRODUCTION N OPTICAL interferometer used as a frequency discqmiAn ator is the essential part of the electric feedback system developed to reduce the linewidth of semiconductor lasers [l], [2]. This setup is also used in optical frequency noise measurement systems [33. Fast optical discriminators have found applications in laser frequency stabilization [4] as well as in direct detection of frequency modulation [SI. The precise knowledge of the discrimination frequency response of the interferometer is thus essential to determine the limitations of these systems in terms of gain, flatness, and bandwidth of the frequency-to-intensity conversion. We find the discrimination frequency responses of a FabryPerot interferometer operated in reflection as well as in transmission. Experiments were done under various conditions confirming the predictions.