A passive method to compensate nonlinearity 
in a homodyne interferometer

Abstract

This study presents an analysis of the nonlinearity resulting from polarization crosstalk at a polarizing beam splitter (PBS) and a wave plate (WP) in a homodyne interferometer. From a theoretical approach, a new compensation method involving a realignment of the axes of WPs to some specific angles according to the characteristics of the PBS is introduced. This method suppresses the nonlinearity in a homodyne interferometer to 0.36 nm, which would be 3.75 nm with conventional alignment methods of WPs.

Polarization phase-shifting Newton interferometer without errors caused by polarization crosstalk

“…: +886 227712171; fax: +886 287733216. To reduce the errors due to polarization crosstalk, several methods [15][16][17] have been proposed, where the noise due to the crosstalk was eliminated by adjusting the gains of quadrature detector systems. These methods, however, require complicated calibration processes.…”

High-precision positioning stage using optical zooming laser interferometer for linear encoder calibration

“…[3][4][5][6] To remove the cyclic error in laser interferometers, several special techniques are proposed. [7][8][9] The laser-frequencybased technology using a Fabry-Perot cavity is a distinguished technique because it has no cyclic error in principle. [10][11][12] However, it has the disadvantage that the dynamic range is small because of the limit of the laser frequency change.…”

“…Since this modelocked fiber laser did not have a temperature nor frequency stabilizing system, the mode beat frequency, f rep , and the absolute frequency of each modes were not stabilized. The stability of f rep was 9 10 − at 100 seconds. The maximum variation of absolute frequency of each modes was estimated to be The frequency of ECDL1 was phase-locked to one mode of the optical comb generated by the fs-comb laser.…”

“…The center wavelength of ECDL2 was phase-locked to the other mode in the same fs-comb so that the beat frequency, f b2 , was stabilized to constant value. Since the mode beat frequency in the fs-comb, f rep , had a high stability of 9 10 − even if it did not have the stabilization system, the beat frequency between the center frequencies of the two ECDLs, f p , was stabilized well. Figure 3 shows the optical alignment of the frequency stabilizing system of ECDLs to two different modes of an fs-comb.…”

“…The frequency difference between two modes, to which two ECDLs were locked, was about 0.5 THz. Since the stability of repetition rate of the fs-comb was 9 10 , − the frequency difference between the two modes was stabilized to 9 10 .…”