Quarter Wave Research Articles

Power oscillations induced by the relative Goos-Hänchen phase

By using an optical interferometer composed of a dielectric laser ellipsometer, to change the optical response of transverse electric and magnetic incident radiation, and two polarisers, to trigger the interference pattern induced by the relative Goos-Haenchen phase, we show under which conditions it is possible to optimize the laser power oscillations induced by the relative phase difference between orthogonal polarised states. The Goos-Haenchen interference can then be used to sense rotation, to test optical components, and to simulate quarter and half wave plates.

Rapid fabrication of Spiral Varying Retarder for Using in Simple Schemes of Generating Radial and Azimuthal Vector Optical Fields

In this paper, the simple, reliable and efficient fabrication technology of spiral varying retarder (SVR) on Iceland spar for generating radially and azimuthally polarized beams from linearly polarized Gaussian beam for λ = 632.8 nm is shown. The SVR which consists of 20 sectors was made by laser-induced microplasma processing on plate area of 10 × 10 mm2 in less than 7 minutes. When placing the SVR between two quarter wave plates with orthogonal fast axes the registration of typical images of intensity distribution in the far field in four analyzer positions (0°, 45°, 90°, 135°) confirmed the SVR's ability to generate radially polarized vector optical field. It was also shown that the placing of a half-wave plate, the fast axis of which is oriented at 45° relative to the direction of x axis, allows to create an azimuthally polarized vector optical field.

1.25 GHz – 3.3 GHz broadband solid state power amplifier for L and S bands applications

The research of a single stage broadband solid-state power amplifier based on ATF13876 transistor, which operates in the frequency ranging from 1.25 GHz ~3.3 GHz is presented in this paper. To achieve the broadband performance of the operating bandwidth, a multi-section quarter wave impedance transformer and an approximate transformation of previously synthesized lumped elements into transmission lines are adopted. With neatly design of broadband matching networks and biasing circuit, excellent matching performances and unconditionally stability are achieved over the whole operating bandwidth with a maximum gain of 17.2 dB. The large signal simulation shows that the proposed circuit reaches a saturated output power of 18.12 dBm with a maximum PAE of 27.55% and a 1-dB compression point at 5 dBm input power level. Considering the wide frequency coverage, the features of the proposed design compares favorably with the contemporary state-of-the-art.

Analytical solution of the string vibration model on Sasando musical instrument

This research constructs mathematic model for string vibration on Sasando that expressed as a second-order linear partial differential equation with u denote the vertical displacement experienced by the string at the point x at time t. Besides, the purpose of this research is to determine analytical solution using a method known as separation of variable. There are three analytical solutions from three cases based on constant coefficient values. Case 1 occurs when . Based on he simulation, the string produces a quarter wave within 3 seconds. This means the vibration wavelength 0.083 Hz. In this case the vertical displacement of the string is back to quiescent after vibrating to produce a quarter wave. Case 2 occurs when . The string produces 3.5 waves within 3 seconds, means the vibration wavelength is 1.67 Hz. In this case, the farthest vertical displacement (amplitude) become smaller drastically and back to quiescent. Case 3 occurs when . The vibration wavelength of the string is 2.83 Hz, with 7.5 waves within 3 seconds. The vertical displacement decreases periodically and back to quiescent at a certain time. Analysis of 2-dimensional graph for vertical displacement u(x,t) is done with n = 1,2,3,4,5 which is compared with profile of u(x,t) Gulla (2011). Based on results of the model were mentioned before, the mathematical model of string vibration on Sasando has the similar profile as Gulla (2011). For further, this research is suggested to perform a graph profile analysis of other cases that may arise with variation of parameter values.

Use of interference colours to distinguish between fast and slow axes of a quarter wave plate

A quarter wave plate is commonly used to generate circularly and elliptically polarized light owing to its birefringent property. The orientation of its fast and slow axes with respect to linearly polarized light decides the resultant polarization. Often, low-priced wave plates do not come with their fast and slow axes marked. Users are supposed to conduct a test based on colour changes as seen while tilting the quarter wave plate and assigning the respective axes. Although this procedure is routinely advised, the physics behind the typically observed colours is seldom discussed in the literature. The present article is structured as a tutorial to understand the origin of observed interference colours while a quarter wave plate is tilted about its fast or slow axes. The explanation is given on the basis of the Michel Levy interference colour chart. At the same time, the tutorial is intended to introduce new researchers from multidisciplinary fields like physics, geology, mineralogy and chemistry to basics pertaining to birefringence in a comprehensive way as they are not taught in disciplinary college/university curricula otherwise.

A broadband terahertz quarter wave plate based on asymmetric cross slots

In this paper, a transmissive terahertz (THz) quarter wave plate (QWP) has been proposed to realize the linear-to-circular polarization conversion in terahertz range. This quarter wave plate is composed of two dielectric layers and one metallic layer with asymmetric cross slots. In the range of 0.894–1.378 THz, the axis ratio of proposed device is less than 3 dB, and its polarization conversion efficiency is more than 45%. The distributions of surface currents and electromagnetic field density had been proposed to understand the physical mechanism of proposed device. The linear-to-circular polarization conversion can be attributed to the asymmetric transmission along slots. Finally, the simulation results are validated by experiments in terahertz region. The proposed device has simple geometry and good performance, which can be used as a key component in applications of terahertz communications, terahertz imaging and terahertz sensing.

Direct laser writing of a phase-shifted Bragg grating waveguide for ultrasound detection.

We demonstrate a phase-shifted Bragg grating waveguide (PS-BGW) fabricated by a direct laser writing technique via two-photon polymerization as a high-frequency ultrasonic sensor. The PS-BGW device has a cross-sectional area of 1.5 μm×2 μm, and the grating length is about 100μm. The optical resonant spectrum is investigated numerically and experimentally. The result shows that the fabricated device with a grating depth of 250nm and a quarter wave phase lead to a 20-nm stopband and a 0.085-nm full-linewidth of the transmission notch, making it suitable for photonic sensing applications. Here, the PS-BGW device is demonstrated for the detection of acoustic waves, which can cause strain or deformation of the device and lead to a shift in the resonance wavelength. The sensitivity and the limitations of the device for ultrasound detection are also investigated.

Improvement of accelerating gradients in niobium quarter wave resonators

Systematic studies have been performed on the effect of the surface processing techniques for improving accelerating gradients in superconducting niobium quarter wave resonators (QWR). These include high pressure rinsing (HPR), high temperature heat treatment of cavities and helium pulse processing. Tests done after HPR have not only shown a reduction in field emission in the cavities at high accelerating gradients but also an improvement in the low field quality factor (Q). The effect of the high temperature (650 °C) heat treatment of jacketed QWRs (QWR with the outer helium vessel) on the cavity gradients has also been investigated. This was performed for two different QWR designs and a substantial improvement in performance has been observed in both the cases. The increase in gradients is beyond that due to hydrogen degassing alone. Helium pulse processing during 4 K tests has been tried out on several cavities and its effect on the quality factor at both high and low gradients has been observed. This technique has been found to be useful for those resonators which have a high Q at lower fields but are limited due to the field emission at higher gradients. They have exhibited a marked improvement in the high field Q-slope over and above that obtained with conventional pulse processing under high vacuum. A comprehensive overview of all these developments carried out over the past few years has been reported.

Contributions of hydrodynamic features of a swirling flow to thermoacoustic instabilities in a lean premixed swirl stabilized combustor

A comprehensive study on influences of hydrodynamic features of a swirling flow on thermoacoustic instabilities in a swirl stabilized combustor is performed by using large eddy simulations along with the dynamically thickened flame combustion model. The governing equations in full compressible form are solved by an in-house developed high-order numerical solver. The combustor is simulated in six different equivalence ratios to assess effects of equivalence ratio on the contributions of hydrodynamic features in inducing thermoacoustic instabilities. The obtained results show that the combustor suffers from combustion instabilities at equivalence ratios of 0.55, 0.6, 0.75, and 0.8, while it is stable at the midrange equivalence ratios (0.65 and 0.7). The results indicate that the instabilities are the result of the lock-in mechanism between heat release fluctuations induced by hydrodynamic features and the mixed first tangential and quarter wave longitudinal mode of the combustor. Investigations are carried out to evaluate contributions of central and side recirculation zones, precessing vortex core, and coherent structures in heat release fluctuations. The results show that contributions of hydrodynamic features highly depend on the combustor operating condition. At low equivalence ratios (0.55 and 0.6), coherent structures and side and central recirculation zones are the key features to induce heat release fluctuations in phase with the acoustic perturbations, while at equivalence ratios of 0.75 and 0.8, coherent structures and precessing vortex core play the main role in inducing combustion instabilities.

Terahertz Quarter Wave-Plate Metasurface Polarizer Based on Arrays of Graphene Ribbons

We propose a novel graphene-dielectric-based metasurface for manipulating the polarization of the incident light in the terahertz regime. The proposed structure comprised two orthogonally oriented periodic array of graphene ribbons (PAGRs) which are separated by a dielectric spacer and deposited on an Au-backed dielectric substrate. Based on the transmission line theory, an equivalent model with excellent accuracy is suggested for the proposed structure. By leveraging the simplicity of the model, we design a three-state quarter wave plate that is able to dynamically switch the polarization of the reflected wave to linear, right-, and left-hand polarizations while keeping the reflected amplitude remarkably high. Thanks to the simplicity of the model, the proposed structure can be easily used for designing other metasurfaces for light propagation control applications in imaging, sensing, and telecommunication.

Development of an infrared polarized microscope for evaluation of high gradient stress with a small distribution area on a silicon chip.

In this paper, a special microscope to evaluate stress in a silicon chip was developed based on the principle of photoelasticity. To facilitate stress measurements and to improve their precision, two methods were adopted. First, a six-step phase shifting technique was realized with the aid of two motorized rotation stages. During the implementation of this phase shifting technique, six digital images were captured at different rotation angles of the two stages and employed to automatically calculate the birefringence. Second, an algorithm was developed to correct deviations in the position of the specimen in the six images caused by mechanical vibration; thus, the most significant source of error was addressed. The precision of the system in terms of measuring the stress-birefringence phase difference was verified with a standard quarter wave plate; the results demonstrate that the system is precise to within at least 2°. With the developed system, we evaluated the stress distribution and its variations with thermal cycling around through-silicon vias on a silicon chip at room temperature; we found that stress initially increased with the number of thermal cycles before decreasing with further thermal cycles.

60‐3: Study on the Efficiency Improvement of OLED TVs with High Transmittance Technology of the Polarizer

We have studied the efficiency improvement of OLED TVs using high transmittance technology and reversed quarter wave plate (r‐QWP) of the improved polarizer. It helped that the efficiency of OLED went up, so that power consumption and life time of OLED panels have been improved. In this paper, study on the efficiency improvement of OLED TV using new high transmittance polarizer will be presented.

A dual‐band branch line coupler for LTE 0.7 GHz and LTE 2.6 GHz frequencies

In this paper, a dual-band branch line coupler (BLC) for Long Term Evolution (LTE) 0.7 GHz and LTE 2.6 GHz frequencies is designed and developed. A dual-band quarter wave transmission line (DBQWTL) capable to perform dual band operation for frequency ratio >3 is also proposed. The dual band BLC is designed by replacing the quarter wave transmission line of the conventional single band BLC with the proposed DBQWTL. By means of even and odd mode analysis, the closed form design equations of the proposed DBQWTL are obtained. Considering the implementation viewpoint of the proposed BLC, the circuit parameter analysis is carried out. The proposed BLC performs dual band operation with maximum amplitude imbalance of 0.26 dB and phase deviation of 3.07°. It is found in the comparative analysis that the proposed BLC has novelty in terms of its operating frequency ratio range.

Frequency dependent multi-functional polarization convertor based on metasurface

Controlling the polarization state of light is an important research region in optics due to its enormous potential. Conventional polarization converters inevitably express huge size and low efficiency, which run counter to the requirement of modern optics. Herein, a frequency-dependent multi-functional metasurface is proposed and researched to design a broad-band and high-efficiency reflective-type polarization converter at near-infrared band. Based on the simulation results, 90° polarization convertor and quarter wave plate can be realized at different wavelengths. The broad-band 90° polarization convertor will transform gradually to a broad-band quarter wave plate by increasing the ”coupling gap” at the long wavelength region, and the functionalities of 90° polarization convertor and quarter wave plate can always be kept at the short wavelength region. Our results can provide a guide to design the ultrathin optical polarization converters.

Non-Contact Roughness Measurement in Sub-Micron Range by Considering Depolarization Effects.

The characteristics of a surface, particularly the roughness, play an important role in different fields of the industry and have to be considered to ensure quality standards. Currently, there are numerous sophisticated methods for measuring surface roughness but plenty of them cause long-term damage because they are in contact with the sample. This article presents a non-contact method to accurately determine small surface roughnesses resulting from the consideration of the depolarization effects caused by the rough surface. This technique can be applied as an extension in various roughness measurements and improves the approach of Chandley’s technique, which does not take into account the depolarization of the light scattered by the sample. The experimental setup and the measurements are easy to perform. The essential component is a quarter wave plate, which is incorporated into a Michelson interferometer. With the resulting two different contrasts and the recorded intensities of the sample and the reference mirror, the surface roughness can be estimated straightforwardly. This article details the theoretical approach, followed by the experimental results and the corresponding uncertainties. The experimental results are compared with Chandley’s method. In order to have reference roughness values of the samples, measurements with a stylus profilometer and with a confocal microscope are performed and compared.

Effect of Atomization Quality on Lean Blow-Out Limits and Acoustic Oscillations in a Swirl Stabilized Burner

ABSTRACT The present experimental work highlights the influence of atomization quality on lean blow-out (LBO) limits and acoustic oscillations in a swirl stabilized burner with simplex atomizer. With decrease in the initial spray droplet diameter, the LBO limit shifts toward lower equivalence ratios. Reduction in droplet size also strongly influences the mode of LBO from diffusion flame to premixed lifted flame. Correlations have been developed for the LBO limit, involving mainly the time scales for evaporation, reaction and residence times for the fuel drops, as well as the gas flow. Delay in evaporation causes vapor accumulation before combustion and hence it influences both acoustic oscillations and LBO limit. The frequency of acoustic oscillations locks-in with the quarter wave frequency of the combustor duct for all initial droplet diameters considered. The amplitude of acoustic oscillations decreases with decrease in the initial droplet size.

Laser-induced damage threshold study on TiO2/SiO2 multilayer reflective coatings

Laser-induced damage threshold (LIDT) is a key parameter in high power laser systems. Highly reflective mirrors are made by the combination of high index and low index dielectric thin films of materials, usually oxides, having high damage threshold. The aim of the present investigation was to study the effect of multilayers on LIDT for a combination of high and low index material films with the increase in the number of layers. Firstly, we chose a combination of relatively high damage threshold high index (H) and low index (L) oxide materials, like TiO2 and SiO2. Then, we chose five reflective samples with increasing the number of layers starting with a TiO2 single quarter wave optical thick (QWOT) layer, three-QWOT layer (HL)1H, five-QWOT layer (HL)2H, seven-all QWOT layer (HL)3H and seven-layer (HL)2H 1.6L0.4H with upper two non-quarter layers for sample preparation using electron beam deposition. It has been found that LIDT measured at 1064 nm for single layer is large (2.09 J/cm2), decreases for three layers and remains nearly constant (1.51 J/cm2) as the number of multilayers increases further. When LIDT is measured at 532 nm, LIDT of the single layer and multilayers remains almost the same. However, in case of top two layers made of non-QWOT in seven-layer design the LIDT of the samples in both the cases improved.

SCL3 cryogenic plant process design for RAON

RAON, Rare isotope Accelerator complex for ON-line experiments, is a facility for rare isotope beams in S. Korea. It has three superconducting linear accelerators, SCL1, SCL2, and SCL3. They could serve a broad power range of stable and unstable ion beams. The third superconducting linac, SCL3, which could accelerate rare isotope beams made by an ISOL (Isotope Separation On-Line) facility, consists of three types of cryomodules with two kinds of SC cavities, QWR (Quarter Wave Resonator, 81.25 MHz) and HWR (Half Wave Resonator, 162.5 MHz). A cryogenic plant for SCL3 will cover three cryogenic circuits, bath cooling for QWR at 4.5 K, bath cooling for HWR at 2.05 K, and forced cooling for thermal shields of all cryomodules at 35 – 55 K. ALAT who was a winner in this bidding and has studied our requirements and process designs will supply the cryogenic plant with a helium management system. This paper shows results of the process designs and current status including final heat loads from SCL3, specifications of equipment, a layout, and exergy efficiencies at operating modes.

Fabrication of Al2O3/SiO2 multilayer reflective filters with excellent uniformity for demanding optical interference filters

In this work, we report the fabrication of a high reflective filter with excellent uniformity for demanding optical interference filters. To achieve this, films were deposited in different batches at three different angular positions using electron beam deposition technique. The coatings were carried out using indigenously designed flat jig holder without shapers. Fourteen alternating layers of high and low refractive index films were deposited on BK7 substrates of dimensions 186 × 150 mm by using aluminum dioxide (Al2O3) and silicon dioxide (SiO2) evaporation grade granuals. Individual layers in the stack were deposited at quarter wave optical thickness at a wavelength of 550 nm. To examine the optical properties of multilayer optical films, Gonio-spectrophotometer was used. Roughness and thickness of all the samples were evaluated using Stylus Profilometer and Coherence Correlation interferometer. Surface properties such as wettability, adhesion and hardness were studied. Additionally, to investigate the change in chemical bonding and structural properites of the coating materials used for evaporation before (bulk powdered material) and after deposition of thin films (material left in the crucible after deposition process), FTIR and XRD studies were carried out.

Damping of vibrations in superconducting quarter wave resonators

Damping of vibrations in superconducting quarter wave resonators