Environment-noise-free optical heterodyne retardation measurement using a double-pass acousto-optic frequency shifter.

We demonstrate an environment-noise-free optical heterodyne interferometer (OHI) based on a double-pass acousto-optic frequency shifter (AOFS) for phase retardation measurements. The OHI generates intermediate-frequency (IF) heterodyne beat signals for each orthogonal linear polarization mode of a birefringence sample. The phase differences of the IF signals are compared by using a wide-bandwidth lock-in amplifier.

Generation of azimuthally and radially polarized off-axis beams with an intracavity large-apex-angle axicon.

Depending on cavity configuration, a c-cut Nd:YVO4 laser by using a large-apex-angle axicon can execute azimuthally and radially polarized operations. A large-apex-angle axicon dominates and stabilizes the generation of the pattern, and expands the difference between the ordinary and extraordinary rays to generate off-axis cylindrical vector beams. When the cavity length is properly adjusted, the polarization of off-axis laser beams can exhibit a transition from azimuthal to radial polarization.

Iodine stabilization of a diode laser in the optical communication band.

The iodine molecule has frequently been used as a frequency reference from the green to the near-infrared wavelength region (500-900 nm). We describe the frequency locking of the second-harmonic signal of a 197.2-THz (1520.