We describe a polarization Sagnac interferometer with an in-loop half-wave plate that allows signal detection at the reciprocal port of the beam splitter while maintaining the ability to detect the signal at a dark fringe. Postmodulation and balanced heterodyne detection are used to recover the signal. This topology is simple to control because of its common-path characteristics and its colline...

We propose a new method to detect ultrasmall nonreciprocal phase shifts in solids based on the Sagnac interferometer combined with internal optical modulation of the absorption. The Sagnac interferometer with heterodyne balanced detection is expected to enable shot-noise-limited detection of phase shift as a result of its insensitivity to frequency and amplitude fluctuations of the laser. The l...

Articles you may be interested in Improved common-path fast-scanning heterodyne interferometer system as potential dense-plasma diagnostics Rev. Power spectral densities: A multiple technique study of different Si wafer surfaces A prototype imaging second harmonic interferometer Rev. We describe the design of a common-path heterodyne laser interferometer for the surface profiling of micron-size...

Milliwatt average power terahertz quantum cascade lasers (THz-QCLs, 2 THz to 5 THz) have been developed for spectroscopy and as local oscillators for heterodyne receivers. Novel DFB THz-QCLs have been fabricated and show single-mode operation. The narrow line widths of <10 MHz and stark shift tuning of of 6 GHz, allows for wavelength modulation spectroscopy of low pressure gasses in the unexplo...

We are close to completing our development of single-mode photodetection—in both its semiclassical and quantum forms—with the principal remaining task being the treatment of optical heterodyne detection. Heterodyne detection is the physical realization of the â positive operator-valued measurement. Moreover, its analysis will connect with the notion that POVMs that are not observables can be re...