scispace - formally typeset
Search or ask a question

Showing papers on "Extinction ratio published in 2000"


Journal ArticleDOI
TL;DR: In this article, a novel wavelength division multiplexing (WDM) source employing an uncooled and unisolated Fabry-Perot semiconductor laser diode (F-P SLD) was proposed.
Abstract: We propose and demonstrate a novel wavelength-division-multiplexing (WDM) source employing an uncooled and unisolated Fabry-Perot semiconductor laser diode (F-P SLD). The output wavelength of F-P SLD is locked to the externally injected narrow-band amplified spontaneous emission (ASE). The measured side-mode suppression ratio of the wavelength-locked F-P SLD is larger than 29 dB, when the extinction ratio of the directly modulated light output is above 13 dB. We achieved error-free transmission of 155-Mb/s data over 120 km of nondispersion-shifted fiber. We also propose a cost-effective WDM passive optical network architecture based on the proposed light sources.

391 citations


Journal ArticleDOI
TL;DR: In this paper, a waveguide optical isolator based on non-reciprocal interference was proposed, which exhibits a 19 dB extinction ratio at λ=1.54 μm.
Abstract: A waveguide optical isolator based on nonreciprocal interference is demonstrated. Ridge waveguides are fabricated in a Mach–Zehnder configuration on a single film of bismuth-, lutetium-, neodymium-iron garnet. With this design, no polarizers are required to achieve extinction in the backward propagation direction. This isolator exhibits a 19 dB extinction ratio at λ=1.54 μm. A flat wavelength dependence, to within 2 dB, has been observed in the range between 1.49 and 1.57 μm.

224 citations


Journal ArticleDOI
Zhaoning Yu1, Paru Deshpande1, Wei Wu1, Jian Wang1, Stephen Y. Chou1 
TL;DR: In this article, a reflective polarizer consisting of two layers of 190 nm period metal gratings was fabricated using nano-imprint lithography, and measurements with a He-Ne laser (wavelength=632.8 nm) showed that at normal incidence, this polarizer reflects light polarized perpendicular to the grating lines with a reflectance of 54%, but strongly absorbs parallel-polarized light (transverse electric polarization) with only 0.25%.
Abstract: A reflective polarizer consisting of two layers of 190 nm period metal gratings was fabricated using nanoimprint lithography. Measurements with a He–Ne laser (wavelength=632.8 nm) showed that at normal incidence, this polarizer reflects light polarized perpendicular to the grating lines (transverse magnetic polarization) with a reflectance of 54%, but strongly absorbs parallel-polarized light (transverse electric polarization) with a reflectance of only 0.25%. The enhanced polarization extinction ratio of over 200 at this wavelength is possibly related to the resonance between the two layers of metal gratings. This polarizer is thin, compact, and is suited for integrated optical systems.

158 citations


Journal ArticleDOI
TL;DR: In this article, a hybrid-integrated symmetric Mach-Zehnder all-optical switch was developed for demultiplexing of 168-Gb/s data pulses at a repetition rate of 10 GHz with this switch.
Abstract: We have developed a hybrid-integrated symmetric Mach-Zehnder all-optical switch and evaluated the demultiplexing of 168-Gb/s data pulses at a repetition rate of 10 GHz with this switch. A compact, stable device was realized by assembling semiconductor optical amplifiers as nonlinear waveguides on a planar lightwave circuit in a self-aligned manner. A 6.0-ps switching window needed for 168-Gb/s demultiplexing was provided by the push-pull operation of the symmetric Mach-Zehnder all-optical switch. Demultiplexed signal light showed a high extinction ratio of better than 18 dB. Error-free demultiplexing with a bit error rate of 10/sup -11/ was achieved.

133 citations


Journal ArticleDOI
TL;DR: In this paper, a low-power all-optical switching in a phase-shifted grating has been experimentally demonstrated at 1.55 /spl mu/m. The grating is written in a standard fiber for communication and the switching is based on the cross-phase modulation induced by an intense pump pulse on a low intensity probe.
Abstract: A low-power all-optical-switching in a phase-shifted grating has been experimentally demonstrated at 1.55 /spl mu/m. The grating is written in a standard fiber for communication and the switching is based on the cross-phase modulation induced by an intense pump pulse on a low intensity probe. An extinction ratio of more than 6 dB has been achieved for 1 kW pulse peak power. The strong enhancement of the nonlinear effect due to the group velocity reduction and the switching polarization dependence have been theoretically investigated and experimentally confirmed.

101 citations


Patent
06 Mar 2000
TL;DR: In this article, a planar Mach-Zehnder optical device with a piezoelectric rib disposed on one or both of the waveguide structures is proposed to reduce birefringence.
Abstract: A piezoelectric optical switch includes a planar Mach-Zehnder optical device having a piezoelectric rib disposed on one or both of the waveguide structures. The piezoelectric rib deforms the waveguide structure creating a strain vector that alters the optical path of the waveguide. The piezoelectric rib is offset from the propagation path in the waveguide. This yields several important advantages. By positioning the piezoelectric rib away from the waveguide, the strain components in the propagation path of the waveguide in the directions perpendicular to the direction of propagation, e.g., in the x-direction and the y-direction, are negligible. Since strains in these directions create birefringence, elimination of these strains will minimize the birefringence. The elimination or reduction of birefringence is greatly desired because birefringence degrades the extinction ratio at the outputs of the Mach-Zehnder device. Thus, the piezoelectric switch of the present invention provides a high extinction ratio and a low power consumption and small switching time expected of piezoelectric devices.

93 citations


Journal ArticleDOI
TL;DR: In this paper, a 10-μm-thick single-crystal LiNbO3 films obtained by crystal ion slicing were used for electro-optic modulation.
Abstract: Electro-optic modulation is demonstrated in 10-μm-thick single-crystal LiNbO3 films obtained by crystal ion slicing. This technique uses ion implantation of single-crystal bulk samples followed by selective etching. The measured electro-optic response of these films is comparable, within experimental error, to that of single-crystal bulk LiNbO3 and is superior to previously reported values for epitaxial polycrystalline thin films. The product of half-wave voltage and modulator length, VπL, is 8 V cm. Post lift-off annealing is shown to be of key importance in improving the modulator extinction ratio.

78 citations


Journal ArticleDOI
TL;DR: In this paper, the performance of a time-division-multiplexed (TDM) fiber Bragg grating (FBG) sensor array using a tunable laser source is investigated.
Abstract: The results of an investigation of the performance of a time-division-multiplexed (TDM) fiber Bragg grating (FBG) sensor array using a tunable laser source are reported. The system performance is found limited by the extinction ratio of the optical pulse modulator used for pulse amplitude modulation. Formulas that relate the crosstalk to the extinction ratio of the optical pulse modulator, the modulation parameters of the tunable laser, and the optical path differences among sensing channels are derived. Computer simulation shows that an array of 20 FBG sensors with 3 /spl mu//spl epsi/ resolution can be realized with a commercially available single Mach-Zehnder type optical pulse modulator of -35-dB extinction ratio.

58 citations


Patent
25 Jul 2000
TL;DR: In this article, the extinction ratio between orthogonally polarized beams propagating through a plane polarized system is improved by using polarization beam splitting coating arrangements and/or birefringent materials.
Abstract: Interferometers (510) utilizing polarization-preserving optical systems (511, 512) by plane polarized beams are deviated through preselected angles without changing their linear state of polarization. The interferometers (510) utilizing such optical systems have a variety of applications and are particularly suitable for use in the field of distance measuring interferometry to enhance measurement accuracy by reducing undesirable polarization effects that can introduce errors associated with an otherwise present undesirable polarization rotation found in classical retroreflectors. Prismatic optical elements are preferably used to construct assemblies (511, 512) which can include polarization beam splitting coating arrangements and/or birefringent materials to enhance the extinction ratio between orthogonally polarized beams propagating through such systems.

53 citations


Journal ArticleDOI
TL;DR: In this article, all-optical wavelength conversion and signal regeneration based on cross-absorption modulation in an InGaAsP quantum well electroabsorption modulator (EAM) is studied at different bit rates.
Abstract: All-optical wavelength conversion and signal regeneration based on cross-absorption modulation in an InGaAsP quantum well electroabsorption modulator (EAM) is studied at different bit rates. We present theoretical results showing wavelength conversion efficiency in agreement with existing experimental results, and the signal regeneration capability of the device is investigated. In particular, we demonstrate the dependence of the extinction ratio of both the converted signal and the control signal on the device length and on the power level of the control signal. We also show how the sweep-out dynamics influences the results.

52 citations


Journal ArticleDOI
TL;DR: In this paper, a client-configurable optical add/drop multiplexer (OADM) is demonstrated using a micromachined 8/spl times/6 matrix switch, which can be configured to add or drop any of the eight input channels from/to any of six add/off ports.
Abstract: A client-configurable optical add/drop multiplexer (OADM) is demonstrated using a micromachined 8/spl times/6 matrix switch. The matrix switch can be configured to add/drop any of the eight input channels from/to any of the six add/drop ports. For the switching fabric, the insertion loss is 2/spl sim/3 dB for the dropped channels and 8/spl sim/9 dB for the added channels by using the backsides of the micromirror switches. The switching extinction ratio is over 40 dB, the crosstalk between channels is less than -40 dB, and they are equipment-limited in this experiment.

Journal ArticleDOI
TL;DR: In this article, a polymeric electro-optic modulator based on a 1×2 Y-fed directional waveguide coupler was demonstrated, achieving a low switching voltage of 3.6 V and a high extinction ratio of 26 dB with a wavelength of 1.34 μm.
Abstract: We have demonstrated a polymeric electro-optic modulator based on a 1×2 Y-fed directional waveguide coupler. The symmetric geometry of the 1×2 Y-fed directional coupler provided the modulator unique characteristics of intrinsic 3 dB operating point and two complementary output ends. A low switching voltage of 3.6 V and a high extinction ratio of 26 dB were obtained with the modulator operating at a wavelength of 1.34 μm. The modulator was fabricated with a novel electro-optic polymer that was synthesized from polyurethane cross-linking with a chromophore.

Journal ArticleDOI
TL;DR: In this article, a single-frequency erbium-doped fiber ring laser demonstrates frequency locking to the 50 GHz ITU frequency grid with an accuracy of /spl plusmn/03 GHz and stability of O(spl +mn/005 GHz over a 50-nm tuning range.
Abstract: A discretely tunable, single-frequency erbium-doped fiber ring laser demonstrates frequency locking to the 50-GHz ITU frequency grid with an accuracy of /spl plusmn/03 GHz and stability of /spl plusmn/005 GHz over a 50-nm tuning range An output power of 7 mW and an extinction ratio of 45 dB make this single-frequency laser useful for a variety of DWDM applications

Patent
Toru Hosoi1
22 Nov 2000
TL;DR: In this paper, an optical modulator is provided that not only can realize a suitable initial operating point without using dc voltage for control, but that has little optical loss and can obtain an excellent extinction ratio.
Abstract: An optical modulator is provided that not only can realize a suitable initial operating point without using dc voltage for control, but that has little optical loss and can obtain an excellent extinction ratio. The optical modulator comprises: a substrate having an electro-optical effect, first and second branch optical waveguides formed in a first major surface of the substrate; an optical branching structure for splitting input optical signal and supplying the split signals to the branch optical waveguides; and a 3-dB directional coupler that couples the outputs of the first and second branch optical waveguides. The ratio of nonuniformity, which is represented by the difference in propagation constants of the two optical waveguides in 3-dB directional coupler, to the coupling coefficient of the 3-dB directional coupler is 1 to at least 5, preferably 1 to at least 15, and still more preferably, 1 to at least 20.

Journal ArticleDOI
TL;DR: In this paper, all-optical Boolean OR functionality is demonstrated in an all-active Michelson interferometer allowing simple, stable and efficient operation with a high extinction ratio of /spl sim/12.5 dB.
Abstract: All-optical Boolean OR functionality is demonstrated in an all-active Michelson interferometer allowing simple, stable and efficient operation. This is the first time, to the authors' knowledge, that the OR functionality is demonstrated in an integrated device. Good performance at 10 Gbit/s is obtained with a high extinction ratio of /spl sim/12.5 dB.

Journal ArticleDOI
TL;DR: The results indicate that the aperture dimension significantly impacts the polarizer transmission behavior and that the extinction of the unwanted polarization is often limited by depolarizing scattering that is due to the finite aperture size.
Abstract: The transmission characteristics of wire grid polarizers fabricated in finite apertures are investigated by using a three-dimensional finite-difference time-domain formulation Specifically, the optical transmissivity and extinction ratio are characterized for a wide variety of geometrical parameters including aperture size in both dimensions, conducting wire fill factor, and polarizer thickness A dispersive material model is used to investigate the performance of polarizers fabricated by using realistic metals at infrared wavelengths The results indicate that the aperture dimension significantly impacts the polarizer transmission behavior and that the extinction of the unwanted polarization is often limited by depolarizing scattering that is due to the finite aperture size

Journal ArticleDOI
TL;DR: In this article, the extinction ratio of a standard phase-shape binary transmission (PSBT) signal is increased in order to obtain a high tolerance to both chromatic dispersion and signal-to-noise ratio degradation.
Abstract: A theoretical assessment of the performance of a new modulation format which is of interest for both submarine and terrestrial optical transmission is presented. It consist in increasing the extinction ratio of a standard phase-shape binary transmission (PSBT) signal in order to obtain a high tolerance to both chromatic dispersion and signal-to-noise ratio degradation. This enables the optical power to be reduced and also therefore nonlinear effects, or the amplifier spacing to be increased. Furthermore, this modulation format yields a high spectral efficiency for wavelength division multiplexing application.

Journal ArticleDOI
TL;DR: In this article, integrated tandem traveling-wave electroabsorption modulators are demonstrated as high-speed optical short pulse generators and demultiplexers for >100 Gbit/s optical time-division-multiplexed systems.
Abstract: Integrated tandem traveling-wave electroabsorption modulators are demonstrated as high-speed optical short pulse generators and demultiplexers for >100 Gbit/s optical time-division-multiplexed systems. The tandem significantly increases the extinction ratio and further compresses the optical pulses in comparison to a single modulator. An extinction ratio of /spl sim/50 dB is achieved while optical pulses of 4-6 ps width at 30-40 GHz are generated.

Proceedings ArticleDOI
31 Aug 2000
TL;DR: The results of an investigation of the performance of a time-division-multiplexed fiber Bragg grating (FBG) sensor array using a tunable laser source are reported in this article.
Abstract: The results of an investigation of the performance of a time-division-multiplexed fiber Bragg grating (FBG) sensor array using a tunable laser source are reported The system performance is found to be limited by the extinction ratio of the optical pulse modulator used for pulse amplitude modulation Formulas that relate the crosstalk to the extinction ratio of the optical pulse modulator, the modulation parameters of the tunable laser, and the optical path differences among sensing channels are derived Computer simulation shows that an array of 20 FBG sensors with 3 (mu) (epsilon) resolution can be realized with a commercially available single Mach-Zehnder type optical pulse modulator of -35 dB extinction ratio

Patent
Henry A. Hill1
25 Jul 2000
TL;DR: Polarization preserving optical systems as discussed by the authors can be used in the field of distance measuring interferometry (DMI) to enhance measurement accuracy by reducing undesirable polarization effects that can introduce errors associated with an otherwise present undesirable polarization rotation found in classical retroreflectors.
Abstract: Polarization preserving optical systems for use in deviating plane polarized beams (371, 372) through preselected angles without changing their linear state of polarization. A plurality of reflecting surfaces are arranged such that the light incident thereon is always P-polarized or S-polarized. Prismatic optical elements (310, 320, 330, 340) are preferably used to construct assemblies including mirrored surfaces and/or total internal reflection (TIR) surfaces. The assemblies can also include polarization beam splitting coating arrangements and/or birefringent materials to enhance the extinction ratio between orthogonally polarized beams propagating through such systems. The optical systems have a variety of applications and are particularly suitable for use in the field of distance measuring interferometry (DMI) to enhance measurement accuracy by reducing undesirable polarization effects that can introduce errors associated with an otherwise present undesirable polarization rotation found in classical retroreflectors. Non-retroreflecting embodiments are also presented.

Journal ArticleDOI
01 Feb 2000
TL;DR: In this paper, a detailed theoretical study on wavelength conversion using cross-gain modulation in SOAs, employing counter-propagation of the input and the probe signals, is presented and the theoretical results on the performance of the converter, in terms of extinction ratio, crosstalk and conversion bandwidth, are discussed.
Abstract: A detailed theoretical study is presented on wavelength conversion using cross-gain modulation in SOAs, employing counter-propagation of the input and the probe signals. The Fabry-Perot resonances caused by the residual facet reflectivities of the device are considered. Theoretical and experimental results on the performance of the converter, in terms of extinction ratio, crosstalk and conversion bandwidth, are presented and discussed. Good agreement between theoretical and experimental results has been observed. The concatenation performance of a simple WDM optical cross-connect architecture employing this type of wavelength converter is experimentally investigated using a re-circulating loop. Penalty-free concatenation of 25 such nodes has been demonstrated.

Patent
14 Jul 2000
TL;DR: In this article, a 1×2 wavelength selective Mach-Zehnder interferometer switch is used to encode the input broadband light source and decode the transmitted spectrally encoded signals.
Abstract: The encoder/decoder design for spectrum-encoded optical CDMA systems uses waveguide circuits monolithically integrated on one chip to fulfill essential encoding and decoding functions. The integrated device functions as a 1×2 wavelength selective Mach-Zehnder interferometer switch to encode the input broadband light source and to decode the transmitted spectrally encoded signals. The device comprises a frontal 3-dB coupler, a double-ended arrayed-waveguide grating (AWG), and arrays of thermooptic phase shifters and attenuators, together with their symmetric images reflected from the high-reflection coated facet, to realize all required functionality. The thermooptic phase shifters and attenuators are programmable through electronic interface to realize programmable encoding and decoding capabilities. The attenuators are used to equalize the powers and to increase the ON/OFF extinction ratio of all spectral chips.

Journal ArticleDOI
TL;DR: In this article, the combined use of self-phase modulation (SPM) and joint optimization of the bias and modulation voltages to increase the dispersion limited transmission distance is considered for multiple quantum well Mach-Zehnder modulators.
Abstract: For 10-Gb/s transmission over nondispersion shifted fiber, the combined use of self-phase modulation (SPM) and joint optimization of the bias and modulation voltages to increase the dispersion limited transmission distance is considered for multiple quantum well Mach-Zehnder modulators. For the dual drive (push-pull) modulation format, the dependence of the receiver sensitivity on fiber length and average transmitted optical power is determined for both conventional and /spl pi/ phase-shift modulators with either symmetric or asymmetric Y-branch waveguides. When SPM is negligible and the optical extinction ratio is maximized, the modulator design must he considered carefully in order to increase the transmission distance. By combining SPM and optimum modulation conditions, the dependence of the system performance on the modulator design is reduced substantially. For an average transmitted optical power of 12.5 dBm, the receiver sensitivity for transmission over 140 km of fiber varies by only 0.3 dB for the different modulator designs. This compares with a variation of 3.1 dB for maximum extinction ratio modulation.

Proceedings ArticleDOI
07 May 2000
TL;DR: A new method for accurately measuring ER using the properties of average power limited (APL) amplifiers that does not require high-speed detection equipment is described.
Abstract: Summary form only given. As global communication systems rapidly expand and high-speed optical TDM and WDM networks continue to mature, the performance of optical modulators becomes increasingly important. Accurate methods of characterizing and optimizing key parameters, such as the extinction ratio, to levels exceeding 40 dB become necessary. The modulator extinction ratio (ER), defined as the power off-to-on ratio, impacts on communication performance in many ways. It determines the initial distance between logical zero and one power levels. Incomplete ER degrades sensitivity in optically preamplified links and leads to multiple interferometric cross talk, which adversely impacts both TDM and WDM systems. Furthermore, the ER limits the dynamic range of data-rates for variable duty-cycle (VDC) multi-rate optical communications. The author describes a new method for accurately measuring ER using the properties of average power limited (APL) amplifiers that does not require high-speed detection equipment.

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the performance of p-i-n diode intensity modulated spectrally sliced (SS) broadband sources using the saddlepoint approximation.
Abstract: The use of a spectrally sliced (SS) broad-band source provides a cost effective alternative to laser diode sources for wavelength-division multiplexing (WDM). In this paper the performance of direct detection p-i-n diode intensity modulated SS systems is analyzed using the saddlepoint approximation. Using this approach, based on moment generating functions, the effects of pulse distortion, intersymbol interference (ISI) and nonideal modulator extinction ratios have been included in the analysis of SS systems for the first time. The presence of ISI error floors as the product of optical bandwidth and bit time decreases is demonstrated using a model that agrees with previous work in the case of low bit rate, widely spaced channels. In addition, comparisons with recent experimental results from the literature are made with good agreement. Subsequently, the use of an integrate and dump filter where the integration time starts after the beginning of a bit is investigated and shown to produce significant enhancements to bit-error rate performance. Furthermore, it is shown that a modulator extinction ratio of 20 dB will suffice for 10/sup -9/ bit-error rate (BER) in most cases, with 30 dB offering a performance close to that possible with an ideal modulator. Finally, the likely system power for an SS system is presented.

Patent
20 Dec 2000
TL;DR: In this article, an integrated optical chip (IGS) includes an optical waveguide network (11) formed on a surface (106) of a substrate (72) formed of an electrooptically active material.
Abstract: An integrated optics chip (70) includes an optical waveguide network (11) formed on a surface (106) of a substrate (72) formed of an electrooptically active material. The optical waveguide network (11) has an input facet (86) where an optical signal may be input to the optical waveguide network (11) and an output facet (88) where optical signals may be output from the optical waveguide network (11). A trench (74) is formed in the bottom surface (80) of the substrate and arranged to extend into the substrate toward the optical waveguide network (11). The trench (74) prevents light rays incident thereon from inside the substrate (72) from propagating to the output facet (88). In particular, the trench (74) prevents light scattered at the input facet (86) or from scattering centers in the optical waveguide network (11) from reflecting from the bottom surface (80) of the substrate (72) to the output facet (88). A cover (78) may be mounted to the top surface (106) of the substrate (72) to provide structural strength to the integrated optics chip (70). One or more side grooves (143, 144) may be formed in the sides of the substrate (72) and cover (78). A light absorbing material may be placed in the trench (74) and grooves (143, 144). A plurality of electrodes (150) may be formed on the substrate (72) adjacent the optical waveguide network (11), and a plurality of access electrodes (158, 160) may be formed on sides of the substrate (72) and cover (78) to provide electrical signals to the electrodes (150).

Journal ArticleDOI
TL;DR: In this paper, the design and performance of a mechanical shutter for laser light based on low voltage piezoelectric transducers is described, focusing the beam through a pair of piezo-mounted slits, a transmission of 80%, a switching time of 10 μs, and an extinction ratio of 300:1 are obtained.
Abstract: The design and performance of a mechanical shutter for laser light based on low voltage piezoelectric transducers is described. By focusing the beam through a pair of piezo-mounted slits, a transmission of 80%, a switching time of 10 μs, and an extinction ratio of 300:1 are obtained.

Journal ArticleDOI
H.K. Kim1, S. Chandrasekhar
TL;DR: In this article, the in-band crosstalk penalty induced at a different signal quality (optical signal to noise ratio [OSNR], extinction ratio) was investigated.
Abstract: The in-band crosstalk penalty induced at a different signal quality (optical signal to noise ratio [OSNR], extinction ratio) is investigated. When the OSNR changes from >40 dB to 29 dB, the power penalty at the 25 dB in-band crosstalk increases from 1.5 to 5.5 dB. By choosing an optimal value for the decision level of the receiver, the performance becomes quite tolerant to the varied signal quality as the power penalty induced at a signal having 25 dB of OSNR mixed with 20 dB of crosstalk is less than 2.7 dB.

Journal ArticleDOI
TL;DR: In this article, a simple, compact, integrative, flexible, power-efficient, and all-optical switch is proposed based on self-induced gain modulation leading to nonlinear transmittance with a threshold level dependent on input powers of the data and control signals counter propagating in cascaded semiconductor optical amplifiers.
Abstract: We propose a simple, compact, integrative, flexible, power-efficient, and all-optical switch. The operation is based on self-induced gain modulation leading to nonlinear transmittance with a threshold level dependent on input powers of the data and control signals counterpropagating in cascaded semiconductor optical amplifiers. We demonstrate numerically the all-optical switch with small-signal modulation, low-power consumption, high-output power, and high-output extinction ratio.

Journal ArticleDOI
TL;DR: In this paper, the authors theoretically analyzed the performance of optical thin-metal-clad waveguide polarizers with emphasis on the effect of dielectric-cover-layer (i.e., superstrate) thickness.
Abstract: We theoretically analyze the performance of optical thin-metal-clad waveguide polarizers with emphasis on the effect of dielectric-cover-layer (i.e., superstrate) thickness. We show that the polarization extinction ratio can be theoretically made infinite by selection of metal film thickness and polarizer length for a given dielectric-cover-layer thickness. It is shown that the required metal film thickness and polarizer length should be changed for reaching an infinite extinction ratio as different cover layer thicknesses are to be used. However, an infinite extinction ratio is not possible as the dielectric cover layer is thinner than some value. For fixed metal film and buffer layer thicknesses, a certain discrete cover layer thicknesses are required for reaching infinite extinction ratios.