Spectrally pure photons generated in a quasi-phase matched xenon-filled hollow-core photonic crystal fiber.

Spectrally pure photons heralded from unentangled photon pair sources are crucial for any quantum optical system reliant on the multiplexing of heralded photons from independent sources. Generation of unentangled photon pairs in gas-filled hollow-core photonic crystal fibers specifically remains an attractive architecture for integration into quantum-optical fiber networks. The dispersion design offered by selection of fiber microstructures and gas pressure allows considerable control over the group-velocity profile which dictates the wavelengths of photon pairs that can be generated without spectral entanglement.

Two-lens anisotropic image-inversion system for interferometric information processing.

Interferometric image processing systems based on image inversion normally use multiple paths with inversion mirrors. Since such systems must meet strict requirements of alignment and stability, a common-path implementation using polarization channels and six anisotropic optical elements was recently introduced. We demonstrate here the operation of a common-path polarization-based image-inversion interferometeric system using only two anisotropic lenses.

A common-path polarization-based image-inversion interferometer.

We present a collinear, common-path image-inversion interferometer using the polarization channels of a single optical beam. Each of the channels is an imaging system of unit magnification, one positive and the other negative (inverted). Image formation is realized by means of a set of anisotropic lenses, each offering refractive power in one polarization and none in the other.

Basis-neutral Hilbert-space analyzers.

Interferometry is one of the central organizing principles of optics. Key to interferometry is the concept of optical delay, which facilitates spectral analysis in terms of time-harmonics. In contrast, when analyzing a beam in a Hilbert space spanned by spatial modes - a critical task for spatial-mode multiplexing and quantum communication - basis-specific principles are invoked that are altogether distinct from that of 'delay'.

Octave-spanning coherent perfect absorption in a thin silicon film.

Although optical absorption is an intrinsic materials property, it can be manipulated through structural modification. Coherent perfect absorption increases absorption to 100% interferometrically but is typically realized only over narrow bandwidths using two laser beams with fixed phase relationship. We show that engineering a thin film's photonic environment severs the link between the effective absorption of the film and its intrinsic absorption while eliminating, in principle, bandwidth restrictions.