Circular polarization filters made of chiral sculptured thin films: experimental and simulation results

Sculptured thin films: accomplishments and emerging uses

“…Normally incident, circularly polarized light of one handedness can be reflected almost completely, while that of the other handedness is substantially transmitted, if absorption is small enough and the film is sufficiently thick, in the Bragg regime. This was demonstrated by Wu et al [25] with chiral STFs fabricated using the serial bideposition technique. As of now, the Bragg regime can be positioned at virtually any λ 0 ∈ [450, 1700] nm.…”

Exhibition of circular Bragg phenomenon by hyperbolic, dielectric, structurally chiral materials

“…The hyperbolicity was found to significantly alter-but not eliminate-the exhibition of the circular Bragg phenomenon, which has long been known to be the distinctive signature of nonhyperbolic SCMs such as cholesteric liquid crystals 9 and chiral sculptured thin films. 6 Although practical realization of hyperbolic SCMs has yet to occur, physical vapor deposition offers suitable techniques to fabricate these materials. Significantly wider circular-polarizationsensitive stopbands may be exhibited by hyperbolic SCMs in comparison to their nonhyperbolic analogs.…”

“…The stopband is best seen when the thickness of the SCM exceeds a certain number of helical pitches. 6,[9][10][11] When dissipation is small enough to be ignored, ̳ ε r ðzÞ is positive definite, and the variations of ε a;b;c with respect to the free-space wavelength λ 0 are also small enough to be ignored, the circular-polarization-sensitive stopband can be delineated as 4…”

“…For SCMs of this kind, the adequacy of the continuum constitutive equations (1) at sufficiently large free-space wavelengths has been established experimentally. 6,7 A nanoscopic-to-continuum model based on the Bruggeman homogenization formalism has also been developed. 8 The optical signature of an SCM is a circular-polarization-sensitive stopband.…”

Tuning of sculptured-thin-film spectral-hole filters by postdeposition etching

“…[1][2][3] These films are grown by directing the vapor flux from either one source or many sources of bulk matter in an evacuated chamber toward a substrate whose position and orientation are dynamically controlled to grow columns of different shapes. The concurrent control of porosity makes STFs very attractive as optical filters and sensors [4][5][6] and even as laboratories for testing technoscientific concepts at the nanoscale. 7 A prominent class of STFs contain helical columns and are called chiral STFs because of their structural handedness.…”