Quarter-wave Retarder Research Articles

Comparison of quarter-wave retarders over finite spectral and angular bandwidths for infrared polarimetric-imaging applications

We compare three technological approaches for quarter-wave retarders within the context of polarimetric-imaging applications in the long-wave infrared (LWIR) spectrum. Performance of a commercial cadmium sulfide (CdS) crystalline waveplate, a multilayer meanderline structure, and a silicon (Si) form-birefringent retarder are evaluated under conditions of 8-12 μm broadband radiation emerging from an F/1 focusing objective. Metrics used for this comparison are the spectrally dependent axial ratio, retardance, and polarization-averaged power transmittance, which are averaged over the angular range of interest. These parameters correspond to the characteristics that would be observed at the focal-plane array (FPA) detector of an LWIR imaging polarimeter.

Single cell-gap transflective liquid crystal device created by controlling the pretilt angle using a liquid crystalline reactive monomer

We present a single cell-gap transflective liquid crystal (LC) device using a homogeneous alignment polyimide (H-PI) mixed with a liquid crystalline reactive monomer that is able to vertically align the LC. We obtain two different pretilt angles in each pixel through the region by region control of the UV exposure time. The smaller pretilt angle is used to obtain a half-wave phase retardation for the transmissive part, whereas the larger pretilt angle is used to obtain a quarter-wave phase retardation for the reflective part.

A subwavelength slit as a quarter-wave retarder

We have experimentally studied the polarization-dependent transmission properties of a nanoslit in a gold film as a function of its width. The slit exhibits strong birefringence and dichroism. We find, surprisingly, that the transmission of the polarization parallel to the slit only disappears when the slit is much narrower than half a wavelength, while the transmission of the perpendicular component is reduced by the excitation of surface plasmons. We exploit the slit's dichroism and birefringence to realize a quarter-wave retarder.

4D profile of phase objects through the use of a simultaneous phase shifting quasi-commonpath interferometer

Modulation of polarization is commonly employed in optical interferometry through the useof polarizers and quarter-wave retarders. Phase shifts between interfering beams can beeasily controlled with such techniques. This communication describes some details ofmodulation of polarization which are useful in phase shifting interferometry appliedto the study of phase objects. As an application, the case of a two-beam phasegrating interferometer is discussed on the grounds of polarization analysis as anexample. The configuration presented does not require micro-polarizer arrays oradditional software to eliminate noise caused by vibration. This system does not use adouble window, and generates two beams, the separation of which can be variedaccording to the characteristics of the grid used. Experimental results are also given.

Achromatic terahertz quarter-wave retarder in reflection mode

A compact achromatic quarter-wave retarder (QWR) operating in reflection mode is designed for using in terahertz region. It is a composite device utilizing form birefringence and Fabry–Perot (FP) interference. Under illumination of plane waves with incidence angle of 45°, from 1.8 THz to 2.8 THz, the QWR achieved only ±2° variation around 90° phase retardation, enlarging the working bandwidth of ordinary QWR greatly. An analytical model combining transmission-line (TL) theory with effective medium theory (EMT) is presented and results agree well with the time-consuming numerical calculation. The 38 μm thick construction is simple and easy for fabrication by the existing lithographic technique and a promising application in terahertz or other frequency region is believed.

Linearly-polarized White-light-emitting OLEDs Using Photon Recycling

We herein report on the production of efficient polarized white electroluminescence (EL) from an organic light-emitting diode (OLED), which was fabricated using an achromatic quarter-wave retardation plate (QWP) film and a giant birefringent optical (GBO) photonic reflective polarizer. Luminous polarized white EL light of 14,600 cd/m, with a high peak efficiency (>18 cd/A), was produced from a polarized white OLED that was fabricated using this method. These values are almost double those achieved by using a similar white OLED with only a polarizer film. Furthermore, the ratio of linear polarization obtained was about 35:1 over the whole range of brightness of the white EL emission.

Modeling and simulation of polarization errors in reflective fiber optic current sensor

Several key optical components in a reflective fiber optic current sensor (R-FOCS) show error characteristics, which induces linearly polarized light wave in polarization maintaining (PM) fiber and circularly polarized light wave in sensing fiber to be an elliptically polarized light wave. Therefore, nonreciprocal phase shift induced by magnetic field of the current is interrupted by the wrong polarization state. Focused on optical polarization error in R-FOCS, we analyze the characteristics of polarization errors associated with optical components in R-FOCS theoretically, and demonstrate the methods to build optical polarization error models by using Poincaré sphere and Jones matrix, respectively. Then, based on a model of polarization states in R-FOCS, we theoretically investigate the effect of several main error factors on optical polarization characteristics, including polarizing performance of polarizer, phase delay in quarter-wave retarder, splice angular between quarter-wave retarder and PM fiber, birefringence in sensing head and mirror reflection phase shift error. Finally, we quantify a nonreciprocal phase shift to be detected in R-FOCS with optical polarization error respectively, and propose measures.

Broadband circularly-polarized infrared emission from multilayer metamaterials

Development of a 2D metamaterial that preferentially emits broadband circularly-polarized (CP) infrared radiation is hindered by the fact that orthogonal electric-field components are uncorrelated at the surface of the thermal emitter, a consequence of the fluctuation-dissipation theorem. We achieve broadband CP thermal emission by fabricating a meanderline quarter-wave retarder on a transparent thermal-isolation layer. Behind this isolation layer, in thermal contact with the emitter, is a wire-grid polarizer. Along with an unavoidable linear polarized radiation characteristic from the meanderline, we measured a degree of circular polarization (DOCP) of 28%, averaged over the 8- to 12 μm band.

Retardation Free In-plane Switching Liquid Crystal Display with High Speed and Wide-view Angle

In this paper, we propose an in-plane switching (IPS) mode for liquid crystal displays (LCDs) that, in principle, is free of retardation of the LC cell. Basically, the optical configuration of the LC cell consists of an A-plate and an LC layer for switching between the dark and bright states. We could achieve a fast response time compared with the conventional in-plane LC cell because the free retardation condition of the proposed LC cell enables us to reduce the cell gap even by quarter-wave retardation without any change of the optimized LC material in the transmissive mode. Experiments for verification of the proposed in-plane switching LC cells have shown a significant reduction of the rising time and falling time simultaneously due to the small cell gap. Furthermore, we also proposed an optical configuration for wide viewing property of the retardation free IPS LCD by applying the optical films. We proved the wide-view property of the retardation free IPS LCD by comparing its optical luminance with the calculated optical property of the conventional IPS LCD.

8.1: Quarter Wave Retardation Film for Improving Viewing Angle Properties in Time‐Sequential Stereoscopic 3D Liquid Crystal Displays

AbstractWe investigated how to achieve desired optical properties of quarter wave retardation films QWFs that increase the viewing angle of time‐sequential stereoscopic 3D liquid crystal displays LCDs, such as high luminance, low crosstalk, low color change, and low head‐tilt‐angle dependency. These display properties were strongly affected by the out‐of plane retardation Rth of the QWF. We developed QWFs whose in‐plane and out‐of‐plane retardation are independently controllable by adjustment of a polymerized discotic material layer and a triacetate cellulose film, and 3D‐LCDs with high viewing angle properties were realized using these QWFs whose Rth was nearly zero.

8.4: Contrast‐Enhanced High‐Speed Polarization Modulator for Active‐Retarder 3D Displays

AbstractA contrast‐enhanced, high‐speed polarization modulator for active‐retarder 3D displays is proposed. By using a double‐cell structure together with a dedicated driving scheme and an external quarter‐wave retarder, a high‐performance modulator can be realized, resulting in minimized brightness loss and low crosstalk levels in fast‐refresh, time‐multiplexed 3D displays.

Principal angles and principal azimuths of frustrated total internal reflection and optical tunneling by an embedded low-index thin film

The condition for obtaining a differential (or ellipsometric) quarter-wave retardation when p- and s-polarized light of wavelength λ experience frustrated total internal reflection (FTIR) and optical tunneling at angles of incidence ϕ ≥ the critical angle by a transparent thin film (medium 1) of low refractive index n1 and uniform thickness d, which is embedded in a transparent bulk medium 0 of high refractive index n0 takes the simple form: -tanh2 x = tan δp tan δs, in which x = 2πn1(d/λ)(N2sin2ϕ - 1)(1/2), N = n0/n1, and δp, δs are 01 interface Fresnel reflection phase shifts for the p and s polarizations. From this condition, the ranges of the principal angle and normalized film thickness d/λ are obtained explicitly. At a given principal angle, the associated principal azimuths ψr, ψt in reflection and transmission are determined by tan2ψr = -sin 2δs/sin 2δp and tan2ψt = -tan δp/tan δs, respectively. At a unique principal angle ϕe given by sin2ϕe = 2/(N2 + 1), ψr = ψt = 45° and linear-to-circular polarization conversion is achieved upon FTIR and optical tunneling simultaneously. The intensity transmittances of p- and s-polarized light at any principal angle are given by τp = tan δp/tan (δp - δs) and τs = -tan δs/tan (δp - δs), respectively. The efficiency of linear-to-circular polarization conversion in optical tunneling is maximum at ϕe.

Reconfigurable achromatic half-wave and quarter-wave retarder in near infrared using crystalline quartz plates

Birefringent wave plates, often referred to as retarders, generally exhibit a strong wavelength dependence. However, there is a real need for achromatic retarders that exhibit identical characteristics over a broad wavelength range. In this paper, we have studied the design and characteristics of a cascaded system of birefringent plates in the near infrared region. Here we have studied a cascaded system of three birefringent plates using matrix analysis and designed a system which, by suitable reorientation of one of the plates, may perform both as an achromatic quarter-wave plate and half-wave plate, over the wavelength range of 1000 to 1800 nm. An inexpensive design for such an achromatic combination using crystalline quartz is described. The new arrangement of three birefringent plates proposed has the promise of producing achromatic combinations with fairly good accuracy.

Achromatic athermalized retarder fabrication

A method for fabricating an achromatic, athermalized quarter-wave retarder is presented that involves monitoring retardance during polishing. A design specified by thicknesses alone is unlikely to meet specification due to uncertainties in birefringence. This method facilitates successful fabrication to a retardance specification despite these uncertainties. A retarder made from sapphire, MgF(2), and quartz was designed, fabricated, and its performance validated for the 0.470 to 0.865 μm wavelength region. Its specifications are as follows: at wavebands centered at 0.470, 0.660, and 0.865 μm, the band-averaged retardance should be 90°±10° for all fields and retardance should change less than 0.1° for a 1° change in temperature. Retarder fabrication accommodated birefringence and thickness uncertainties via the following steps. The first plate was polished to a target thickness. The retardance spectrum of the first plate was then measured and used to determine a retardance target for the second plate. The retardance spectrum of the combined first and second plates was then used to specify a retardance target for the third plate. The retardance spectrum of the three plates in combination was then used to determine when the final thickness of the third plate was reached.

STUDY OF LINEAL AND NON-LINEAL TRANSMISSION OF AN OPTICAL FIBER SAGNAC INTERFEROMETER AS A BIDIRECTIONAL DEVICE

The optical fiber Sagnac interferometer is a versatile system that has been investigated for a variety of applications such as optical switchers, filters, demultiplexers and passive mode-locked laser. In many cases, this arrangement is designed using a symmetrical coupler with two of their ports connected making a loop and generally the analysis have been focused in the transmission of the signal propagated in only one direction. Therefore in the present work a complementary study of the system considering the analysis for the lineal and non-lineal transmission as a bidirectional device has been performed. The experimental setup consists of different optical fiber lengths inside the cavity loop (between 100 and 500 m) with highly twisted singlemode fiber, a quarter wave retarder placed asymmetrically in one arm and a 50/50 coupler. The results have shown that for low optical powers, it is possible to adjust the system transmission in both propagation directions with the rotation of the retarder wave. On the other hand, in high optical power levels, this arrangement showed that the transmission increases slowly for the case when both the input and the output beams have the same polarization. This behavior can be used for pedestal suppression in a light pulse. Furthermore, for the case when the output signal polarization is orthogonal respect to the input one, the transmission changes quite fast. This effect can be used for applications such as the passive mode-locking.

Single reflection quarter-wave device design

If a monochromatic linearly polarized plane wave is incident on an isotropic-uniaxial or isotropic-biaxial interface and if the incidence plane coincides with a crystal principal plane then circularly polarized light can be obtained by means of a single reflection. This result can be achieved using materials of refractive indices which are not as high as those required in isotropic devices. As is well known, in isotropic-anisotropic interfaces, there are two different incidence angles that yield circularly polarized reflected light. These angles depend on characteristics of both media (refractive indices and angle between the optical axis and the interface) and also on wavelength. In this paper a single reflection retarder is designed. Additionally, its efficiency as quarter wave retarder for non collimated or polychromatic beams is analyzed studying how the amplitudes and phases of both orthogonal components of the reflected electric field vary when the incidence angle and/or the wavelength varies.

Analysis of systematic errors in Mueller matrix ellipsometry as a function of the retardance of the dual rotating compensators

A dual rotating compensator ellipsometer based on the optical PC1SC2A configuration described by Collins [1, chap. 7.3] has been developed. The systematic errors for this configuration if the compensators are quarter-wave plates have been already studied [2, 3, 4]. Smith [5] has demonstrated that the optimum retardance of a dual-rotating-retarder (DRR) instrument must be equal to 127° compared to the quarter-wave (90°) retarders generally used. In this condition random errors are optimized. The aim of this work is to used such retarders and verify if the systematic errors due to uncertainties of the optical elements (i.e. analyzer, polarizer, first and second compensators) are improved too. For each optical element in different configurations like single or 4-zone average measurements, the systematic errors are given and compared according to the compensators. It is demonstrated that using a 127° instead of quarter-wave retarders coupled with 4-zone averaging measurement is the best configuration for this instrument. These results were confirmed by a statistical study.

Patterned color liquid crystal polymer polarizers

We demonstrate patterned polarizers for visible wavelengths using dichroic dye in a liquid crystal polymer (LCP) host. Contact lithography is used to pattern a thin alignment layer, which subsequently transfers the pattern to the LCP. A gray dichroic dye mixture for the visible spectrum is optimized and implemented along with LCP to fabricate this polarizer. A peak extinction ratio of 41 was measured at a 633 nm wavelength, while simultaneously showing patterns as small as 3 μm. Finally, multi layer films are demonstrated by fabricating a two layer patterned circular polarizer consisting of a quarter-wave retarder and a color polarizer. Our process has applications in three-dimensional displays, interferometry, optical storage, and polarimeters.

Polarization Gratings: A Novel Polarimetric Component for Astronomical Instruments

Polarization gratings (PGs) have been recently been developed for ultraefficient liquid crystal displays, nonmechanical optical beam steering, and telecommunication devices at optical and near-infrared wavelengths (0.4–2.0 µm). A PG simultaneously acts as both a spectroscopic and polarimetric disperser for circularly polarized light. With the use of a quarter-wave retarder (or analog) to convert linearly to circularly polarized light, these devices can be used as linear polarimetric analyzers. PGs offer high throughput and high levels of birefringence and can currently be constructed inexpensively to diameters of 150 mm, and development projects are in progress to double that size. In this article we report on the characterization of a PG sample at mid-infrared wavelengths (2–40 µm), including the birefringence, throughput, spectral response, and cold cycling survivability. We discuss these devices in the context of astronomical polarimetry, especially as the polarimetric components for a conceptual study of a SOFIA-based polarimeter.

Polarized electroluminescence from organic light-emitting devices using photon recycling

We present results that show highly polarized electroluminescence (EL) from an organic light-emitting device (OLED) by using a quarter-wave (λ/4) retardation plate (QWP) film and a giant birefringent optical (GBO) photonic reflective polarizer. Polarized EL light of 13,400 cd/m(2) with high peak efficiencies (greater than 10 cd/A and 3.5 lm/W) was obtained from an OLED in this way. These values are almost double those of a polarized OLED that only uses a polarizer. The direction of polarization of the emitted EL light from the polarized OLED corresponded to the passing axis of the GBO reflective polarizer. Furthermore, the degree of linear polarization obtained, i.e. the ratio between the brightness of two linearly polarized EL emissions parallel and perpendicular to the passing axis, is greater than 40 over the whole range of emitted luminance.