In-line broadband 270 degrees (3 lambda/4) chevron four-reflection wave retarders

The net differential phase shift Δt introduced between the orthogonal p and s linear polarizations after four successive total internal reflections inside an in-line chevron dual-Fresnel-rhomb retarder is a function of the first internal angle of incidence φ and prism refractive index n. Retardance of 3λ/4 (i.e., Δt=270°) is achieved with minimum angular sensitivity when φ=45° and n=1.900822. Several optical glasses with this refractive index are identified. For Schott glass SF66 the deviation of Δt from 270° is ≤4° over a wavelength range of 0.55≤λ≤1.1 μm in the visible and near-IR spectrum. For a SiC prism, whose totally reflecting surfaces are coated with an optically thick MgF2 film, Δt=270° at two wavelengths: λ1=0.707 μm and λ2=4.129 μm. This coated prism has a maximum retardance error of ≈5°over\u3ethree octaves (0.5 to 4.5μm) in the visible, near-, and mid-IR spectral range. Another mid-IR 3λ/4 retarder uses a Si prism, which is coated by an optically thick silicon oxynitride film of the proper composition, to achieve retardance that differs from 270° by \u3c0.5° over the 3-5 μm spectral range

Polarization properties of retroreflecting right-angle prisms

The cumulative retardance Δt introduced between the p and the s orthogonal linear polarizations after two successive total internal reflections (TIRs) inside a right-angle prism at complementary angles Φ and 90°−Φ is calculated as a function of Φ and prism refractive index n. Quarter-wave retardation (QWR) is obtained on retroreflection with minimum angular sensitivity when n=(√2+1)1/2=1.55377 and Φ=45°. A QWR prism made of N-BAK4 Schott glass (n=1.55377 at λ=1303.5 nm) has good spectral response (\u3c5° retardance error) over the 0.5-2 μm visible and near-IR spectral range. A ZnS-coated right-angle Si prism achieves QWR with an error of \u3c±2.5° in the 9-11 μm (CO2 laser) IR spectral range. This device functions as a linear-to-circular polarization transformer and can be tuned to exact QWR at any desired wavelength (within a given range) by tilting the prism by a small angle around Φ=45°. A PbTe right-angle prism introduces near-half-wave retardation (near-HWR) with a ≤2% error over a broad (4≤λ≤12.5 μm) IR spectral range. This device also has a wide field of view and its interesting polarization properties are discussed. A compact (aspect ratio of 2), in-line, HWR is described that uses a chevron dual Fresnel rhomb with four TIRs at the same angle Φ=45°. Finally, a useful algorithm is presented that transforms a three-term Sellmeier dispersion relation of a transparent optical material to an equivalent cubic equation that can be solved for the wavelengths at which the refractive index assumes any desired value

Broadband IR polarizing beam splitter using a subwavelength-structured one-dimensional photonic-crystal layer embedded in a high-index prism

An iterative procedure for the design of a polarizing beam splitter (PBS) that uses a form-birefringent, subwavelength-structured, one-dimensional photonic-crystal layer (SWS 1-D PCL) embedded in a high-index cubical prism is presented. The PBS is based on index matching and total transmission for the p polarization and total internal reflection for the s polarization at the prism-PCL interface at 45 degrees angle of incidence. A high extinction ratio in reflection (\u3e50 dB) over the 4-12 mu m IR spectral range is achieved using a SWS 1-D PCL of ZnTe embedded in a ZnS cube within an external field of view of +/- 6.6 degrees and in the presence of grating filling factor errors of up to +/- 10%. Comparable results, but with wider field of view, are also obtained with a Ge PCL embedded in a Si prism

In-line broadband 270 degrees (3 lambda/4) chevron four-reflection wave retarders

The net differential phase shift Δt introduced between the orthogonal p and s linear polarizations after four successive total internal reflections inside an in-line chevron dual-Fresnel-rhomb retarder is a function of the first internal angle of incidence φ and prism refractive index n. Retardance of 3λ/4 (i.e., Δt=270°) is achieved with minimum angular sensitivity when φ=45° and n=1.900822. Several optical glasses with this refractive index are identified. For Schott glass SF66 the deviation of Δt from 270° is ≤4° over a wavelength range of 0.55≤λ≤1.1 μm in the visible and near-IR spectrum. For a SiC prism, whose totally reflecting surfaces are coated with an optically thick MgF2 film, Δt=270° at two wavelengths: λ1=0.707 μm and λ2=4.129 μm. This coated prism has a maximum retardance error of ≈5°over\u3ethree octaves (0.5 to 4.5μm) in the visible, near-, and mid-IR spectral range. Another mid-IR 3λ/4 retarder uses a Si prism, which is coated by an optically thick silicon oxynitride film of the proper composition, to achieve retardance that differs from 270° by \u3c0.5° over the 3-5 μm spectral range

Broadband IR polarizing beam splitter using a subwavelength-structured one-dimensional photonic-crystal layer embedded in a high-index prism

An iterative procedure for the design of a polarizing beam splitter (PBS) that uses a form-birefringent, subwavelength-structured, one-dimensional photonic-crystal layer (SWS 1-D PCL) embedded in a high-index cubical prism is presented. The PBS is based on index matching and total transmission for the p polarization and total internal reflection for the s polarization at the prism-PCL interface at 45 degrees angle of incidence. A high extinction ratio in reflection (\u3e50 dB) over the 4-12 mu m IR spectral range is achieved using a SWS 1-D PCL of ZnTe embedded in a ZnS cube within an external field of view of +/- 6.6 degrees and in the presence of grating filling factor errors of up to +/- 10%. Comparable results, but with wider field of view, are also obtained with a Ge PCL embedded in a Si prism

Polarization properties of retroreflecting right-angle prisms

The cumulative retardance Δt introduced between the p and the s orthogonal linear polarizations after two successive total internal reflections (TIRs) inside a right-angle prism at complementary angles Φ and 90°−Φ is calculated as a function of Φ and prism refractive index n. Quarter-wave retardation (QWR) is obtained on retroreflection with minimum angular sensitivity when n=(√2+1)1/2=1.55377 and Φ=45°. A QWR prism made of N-BAK4 Schott glass (n=1.55377 at λ=1303.5 nm) has good spectral response (\u3c5° retardance error) over the 0.5-2 μm visible and near-IR spectral range. A ZnS-coated right-angle Si prism achieves QWR with an error of \u3c±2.5° in the 9-11 μm (CO2 laser) IR spectral range. This device functions as a linear-to-circular polarization transformer and can be tuned to exact QWR at any desired wavelength (within a given range) by tilting the prism by a small angle around Φ=45°. A PbTe right-angle prism introduces near-half-wave retardation (near-HWR) with a ≤2% error over a broad (4≤λ≤12.5 μm) IR spectral range. This device also has a wide field of view and its interesting polarization properties are discussed. A compact (aspect ratio of 2), in-line, HWR is described that uses a chevron dual Fresnel rhomb with four TIRs at the same angle Φ=45°. Finally, a useful algorithm is presented that transforms a three-term Sellmeier dispersion relation of a transparent optical material to an equivalent cubic equation that can be solved for the wavelengths at which the refractive index assumes any desired value

Ruthenium(II) complexes with tetradentate pyridylthioazoimine [N,S,N,N] ligands: Synthesis, crystal structure and spectroscopy

The Ru(II) complexes cis-[Ru(L)Cl2] (C1-C3) of novel tetradentate NSNN ligands (L) {where L is C5H4N-CH 2-S-C6H4N=C(COCH3)-N=N-C 6H4X, and X is H (L1), CH3 (L2) and Br (L3)}, were synthesized and characterized by spectroscopy (IR, UV/vis and NMR), cyclic voltammetry and crystallography. The tetradentate ligands were isolated as the amidrazones H2L {where H2L is C5H 4N-CH2-S-C6H4NH-C(COCH 3)+N-NH-C6H4X and X is H (H2L1), CH3 (H2L2) and Br (H2L3)} as shown by crystallography of H2L1, but oxidize to azoimines during the formation of the Ru(II) complexes. A crystallographic analysis of C1 showed that the Ru(II) centre is in a distorted octahedral coordination sphere in which the tetradentate ligand occupies three equatorial sites and one axial site (two azoimine nitrogens and a thio sulfur in the equatorial plane and an axial pyridine nitrogen) and two chlorides occupying axial and equatorial coordination sites. The Ru(II) oxidation state is greatly stabilized by the novel tetradentate ligand, showing Ru(III/II) couples ranging from 1.43 to 1.51 V. The absorption spectrum of C1 in acetonitrile was modelled by time-dependent density functional theory