Electrically tunable, ultranarrowband, circular-polarization rejection filters with electro-optic structurally chiral materials

The transmittance spectrum of a slab of an electro--optic structurally chiral material (SCM) that is helicoidally nonhomogeneous in the thickness direction and is endowed with a central 90$^\circ$--twist defect, shows evidence of an ultranarrowband spectral hole when a sufficiently high dc electric field is applied between the entry and the exit planes and the incident light is circularly polarized in opposition to the structural handedness of the SCM. This spectral hole migrates on the wavelength axis as the applied dc electric field is altered in magnitude, thereby suggesting the possible use of a centrally defective, electro-optic SCM slab as an electrically tunable, circular-polarization rejection filter with ultranarrow bandwidth

Theoretical investigation of amplified spontaneous emission in an active structure by extended (3x3) transfer matrix formalism: the case of a non-uniform longitudinal distribution of emitters

We use an extended (3x3) Transfer Matrix Formalism (TMF) to investigate the properties of Amplified Spontaneous Emission (ASE) in an active structure that exhibits a non-uniform spatial distribution of emitters along its longitudinal axis. The spectral density of power of the internal and emitted fields, both filtered into the transfer function of the structure, are expressed analytically in structural dimensionless parameters. We show that a periodically modulated distribution of emitters inside a cavity, in spite of their being spatially non-coherent, are responsible for a cross-interference product that can lead to an unexpected resonant enhancement of the spectral selectivity

Highly dispersive photonic band-gap-edge optofluidic biosensors

Highly dispersive photonic band-gap-edge optofluidic biosensors are studied theoretically. We demonstrate that these structures are strongly sensitive to the refractive index of the liquid, which is used to tune dispersion of the photonic crystal. The upper frequency band-gap edge shifts about 1.8~nm for $\delta n=0.002$, which is quite sensitive. Results from transmission spectra agree well with those obtained from the band structure theory

Compact supercontinuum source for the visible using gain-switched Ti:Sapphire laser as pump

We demonstrate the use of a miniature gain-switched Ti:Sapphire laser for efficient generation of visible supercontinuum light in a highly nonlinear microstructured optical fiber. This allows for a compact setup that puts out nanosecond pulses of light that cover the spectral range from 410 to 1300 nm. It offers a low-cost alternative to the mode-locked-laser-pumped systems as a source of visible supercontinuum light

Joint probability distributions for optical parametric down-conversion

We derive multi mode joint generating functions, photon-number distributions, integrated-intensity distributions and related quantities for spontaneous and stimulated parametric down-conversion in relation to experiments