We present a laboratory demonstration of the Kramers-Kronig relation between the resonant absorption and refractive index in rubidium gas. Our experiment uses a rubidium vapor cell in one arm of a simple Mach-Zehnder interferometer. As the laser frequency is scanned over an atomic resonance, the interferometer output is affected by variations of both the absorption and refractive index of the g...

Laser frequency noise is a significant noise source which couples into the main science measurement of the Laser Interferometer Space Antenna via the mismatch between the interferometer arm lengths. In this paper we discuss the application of an unequal pathlength heterodyne Mach–Zehnder interferometer to measure and actively stablize the master laser frequency as used in LISA Pathfinder. In co...

In this Letter we report on fabricating and analyzing a temperature insensitive refractometer based on two concatenated dual-resonance long-period gratings (LPGs) with an appropriate inter-grating space (IGS) in between. The IGS provides a temperature-dependent extra phase difference between the core and cladding modes, making the refractometer similar to a Mach-Zehnder interferometer with its ...