Reduced wavelength-dependent quarter-wave plate fabricated by a multilayered subwavelength structure

Yu, Wanji; Mizutani, Akio; Kikuta, Hisao; Konishi, Tsuyoshi

doi:10.1364/ao.45.002601

Cited by 29 publications

(12 citation statements)

References 11 publications

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“…In addition, I TE and I TM represent the intensities for conditions of α = β = 0°and α = β = 90°, respectively. The phase retardations of the fabricated elements were evaluated using the following formula: 12) cos ' ¼…”

Section: Optical Evaluationmentioning

confidence: 99%

Reflective waveplate with subwavelength grating structure

Yamada¹,

Ishihara²,

Yanagisawa³

2015

Jpn. J. Appl. Phys.

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A reflective waveplate with subwavelength grating structure of the photoresist was fabricated using two-beam interference technology. From the optical measurement, it is found that the phase retardation of the fabricated reflective element (period: 400 nm, fill factor: 0.5, depth: 280 nm) was almost the same as that of the transmission waveplate with the around twice deeper grating depth (period: 400 nm, fill factor: 0.5, depth: 450 nm). This is because the optical length of the reflective element was twice of the transmissive one by using reflection. By changing the period and depth to 285 nm and to 300 nm, respectively, it is also confirmed from the experimental result that the phase retardation of the reflective waveplate exceeded 150°for 450 nm wavelength at the incident angle of 45°.

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Section: Optical Evaluationmentioning

confidence: 99%

Reflective waveplate with subwavelength grating structure

Yamada¹,

Ishihara²,

Yanagisawa³

2015

Jpn. J. Appl. Phys.

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“…At optical frequencies, birefringent devices are usually manufactured from crystalline materials while at lower terahertz frequencies, materials such as wood and paper were shown to possess moderate birefringence. Alternatively, birefringence can be derived from periodic structures in the form of reflectarrays, multilayered materials, or gratings …”

Section: Introductionmentioning

confidence: 99%

Broadband Terahertz Circular‐Polarization Beam Splitter

Lee

Nirantar

Headland

et al. 2017

Advanced Optical Materials

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to each other. However, drawbacks of these conventional polarization-sensitive devices include narrow operation bandwidth, high cost, low efficiency, and bulkiness. In the terahertz region, an additional issue is related to material availability, since few natural materials exhibit strong birefringence with low loss. [4,5] Circularly polarized terahertz waves are important for studying chiral structures as many molecules in biology and chemistry are chiral and respond differently to left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) waves. [13] In addition, circular polarization can increase channel capacity in wireless communications. As an alternative, metasurfaces can provide designable birefringence at desirable frequencies, among other properties not commonly found in nature. [14] For example, dielectric chiral structures made of silicon [15] and titanium dioxide nanofin gratings [16] capable of circular-polarization beam splitting have been demonstrated at optical frequencies. Aside from that, metal nanoantennas [17] at the mid-infrared range and rotated microstrip patches [18] at microwave frequencies have also been demonstrated with a similar concept. Likewise, dual-image holograms can be generated because of different responses to LHCP and RHCP waves. [19][20][21] However, many of these existing designs are either inherently lossy, complicated, and/or narrowband. At terahertz frequencies, there are, to date, no existing metasurface designs capable of circular-polarization beam splitting.In this paper, we experimentally demonstrate an ultrathin broadband and efficient reflective beam splitter for circular polarization operating at the terahertz band. Relying on the concepts of birefringent metamaterials and localized phase control, the structure employs metallic planar coaxial disk-ring resonators over a ground plane as phase-shifting elements. Each element offers three neighboring resonances that altogether provide a half-wave-mirror response over a large bandwidth. A proper relative orientation between the cells results in a linear phase ramp with a positive or negative phase trend depending on the handedness of circular polarization. Effectively, this metasurface operates to deflect incident LHCP or RHCP waves into opposite sides with predetermined angles away from specular reflection. The design is characterized using a conventional terahertz time-domain spectroscopy (THz-TDS) system.

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“…As mentioned above, our application is the study of the chemical stability of quantum dot sensitized solar cells based on zinc stannate (zinc-tin-oxide, ZTO, Zn 2 SnO 4 ) substrates [13]. Because ZTO has a high refractive index (the refractive index of ZTO has been reported as 2.03 at 633 nm [14]), it is well suited to OWLS in the form of a thin layer on a waveguide surface (see next section). Likewise, the quantum dots have size and refractive index characteristics similar to that of proteins more commonly studied using OWLS.…”

Section: Introductionmentioning

confidence: 99%

Optical Waveguide Lightmode Spectroscopy (OWLS) as a Sensor for Thin Film and Quantum Dot Corrosion

Eggleston

Chen

et al. 2012

Sensors

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Optical waveguide lightmode spectroscopy (OWLS) is usually applied as a biosensor system to the sorption-desorption of proteins to waveguide surfaces. Here, we show that OWLS can be used to monitor the quality of oxide thin film materials and of coatings of pulsed laser deposition synthesized CdSe quantum dots (QDs) intended for solar energy applications. In addition to changes in data treatment and experimental procedure, oxide- or QD-coated waveguide sensors must be synthesized. We synthesized zinc stannate (Zn2SnO4) coated (Si,Ti)O2 waveguide sensors, and used OWLS to monitor the relative mass of the film over time. Films lost mass over time, though at different rates due to variation in fluid flow and its physical effect on removal of film material. The Pulsed Laser Deposition (PLD) technique was used to deposit CdSe QD coatings on waveguides. Sensors exposed to pH 2 solution lost mass over time in an expected, roughly exponential manner. Sensors at pH 10, in contrast, were stable over time. Results were confirmed with atomic force microscopy imaging. Limiting factors in the use of OWLS in this manner include limitations on the annealing temperature that maybe used to synthesize the oxide film, and limitations on the thickness of the film to be studied. Nevertheless, the technique overcomes a number of difficulties in monitoring the quality of thin films in-situ in liquid environments.

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Reduced wavelength-dependent quarter-wave plate fabricated by a multilayered subwavelength structure

Cited by 29 publications

References 11 publications

Reflective waveplate with subwavelength grating structure

Reflective waveplate with subwavelength grating structure

Broadband Terahertz Circular‐Polarization Beam Splitter

Optical Waveguide Lightmode Spectroscopy (OWLS) as a Sensor for Thin Film and Quantum Dot Corrosion

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