Sagnac interferometer

Cooling effects Resistive, capacitive, and inductive effects effects Interferometers Sagnac effect Doppler effect... 

In the case of a space separation of the laser beams (i.e. if the atomic velocity is perpendicular to the direction of the laser beams), the interferometer is in a Mach-Zehnder configuration. Then, the interferometer is also sensitive to rotations, as in the Sagnac geometry (Sagnac, 1913) for light interferometers. For a Sagnac loop enclosing area A, a rotation Q, produces a phase shift ... 

Figure 2. Diagram of the atomic Sagnac interferometer at Yale (Gustavson et al., 2000). Individual signals from the outputs of the two interferometers (gray lines), and difference of the two signals corresponding to a pure rotation signal (black line) versus rotation rate.

The high sensitivity of atomic Sagnac interferometers to rotation rates will enable HYPER to measure the modulation of the precession due to the Lense-Thirring effect while the satellite orbits around the Earth. In a Sun-synchronous, circular orbit at 700 km altitude, HYPER will detect how the direction of the Earth s drag varies over the course of the near-polar orbit as a function of the latitudinal position 9 ... 

In a rotating interferometer, fringe shifts have been observed between light beams that propagate parallel and antiparallel with the direction of rotation [4]. This Sagnac effect requires an unconventional explanation. 

If we attempt the same exercise in U(l) electrodynamics, the closed loop gives the Maxwell-Heaviside equations in the vacuum, which are invariant under T and that therefore cannot describe the Sagnac effect [44] because one loop of the Sagnac interferometer is obtained from the other loop by T symmetry. The U(l) phase factor is oof kZ + a, where a is arbitrary [44], and this phase factor is also "/ -invariant. The Maxwell-Heaviside equations in the vacuum are... 

Figure 3. Arrangement of Sagnac the experiment. Here, LASER represents the source of light, the first mirror is a beamsplitter, M1-M3 are mirrors on the end of arms, and I represents the interferometer.

Figure 9.17. Common path (Sagnac) interferometer used for multichannel FT-Raman a and b indicate two paths followed by light leaving the beamsplitter (BS). CdTe acts as a long pass filter. (Adapted from Reference 22 with permission.)...

Detailed investigation on the optical characteristics, including the electro-optic phase modulation, electric hysteresis property, and thermo-optic coefficient, of transparent PMN-PT electro-optic ceramics have been conducted [229]. A polarization independent PMNT electro-optic switch by using s -shifted fiber Sagnac interferometer stmcture was constracted and analyzed experimentally. Some switch performances, including thermal characteristic and different switching frequency response, were also realized. 

Loop mirror All-fiber Sagnac interferometer which functions as a mirror. 

The loop mirror is a nonresonant Sagnac interferometer, i.e., waves propagating around the loop in opposite directions usually see the same optical path length. Rotation of the loop, or the acquisition of a nonreciprocal phase shift (e.g., due to loop asymmetry and SPM), unbalances the phase shift seen by counterpropagating waves and causes a change in reflectivity. The latter effect is used in nonlinear loop mirrors, described next. 

Such a device with three orthogonal Sagnac interferometers can be used as a navigation system, because the Earth s rotation causes a Sagnac effect that depends on the angle between the surface normal n and the Earth s axis of rotation > i.e., on the geographical latitude. 

F. Riehle, Th. Kisteers, A. White, J. Helmecke, Ch.J. Borde Optical Ramsey spectroscopy in a rotating frame Sagnac effect in a matter-wave interferometer. Phys. Rev. Lett. 67, 177 (1991)... 

Multiple-coupled ring resonators offer further possibilities. Recent developments succeeded in demonstrating compact optical delay elements [74, 75] and optical gyroscopes based on the principle of a Sagnac interferometer [76]. Additional interesting effects can be expected from future research. 

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