The effect of pupil transmittance on axial resolution of reflection phase microscopy

A reflection phase microscope (RPM) can be equipped with the capability of depth selection by employing a gating mechanism. However, it is difficult to achieve an axial resolution close to the diffraction limit in real implementation. Here, we systematically investigated the uneven interference contrast produced by pupil transmittance of the objective lens and found that it was the main cause of the practical limit that prevents the axial resolution from reaching its diffraction limit. Then we modulated the power of illumination light to obtain a uniform interference contrast over the entire pupil. Consequently, we could achieve an axial resolution fairly close to the diffraction limit set by the experimental conditions.

Ultra-Wideband Reconfigurable X-Band and Ku-Band Metasurface Beam-Steerable Reflector for Satellite Communications

A continuously reconfigurable metasurface reflector based on unit cell mushroom geometry that was integrated with a varactor diode is presented in this paper. The unit cell of the metasurface was designed and optimized to operate in the X-band and Ku-band, improving satellite communication’s quality of service. The losses mechanisms of continuous control over the unit cell phase reflection in beam steering resolution are considered and the analysis results are presented. The unit cell design parameters were analyzed with an emphasis on losses and dynamic reflection phase range. The unit cell magnitude and phase reflection are shown in the wide frequency bandwidth and showed a good agreement between all the measurements and the simulations. This metasurface enabled a high dynamic range in the unit cell resonant frequency range from 7.8 to 15 GHz. In addition, the reflection phase and absorption calibration are demonstrated for multiple operating frequencies, namely, 11 GHz, 12 GHz, and 13.5 GHz. Furthermore, design trade-offs and manufacturing limitations were considered. Finally, a beam-steering simulation using the designed metasurface is shown and discussed.

Reflectarray Resonant Element based on a Dielectric Resonator Antenna for 5G Applications

The performance of a proposed cross hybrid dielectric resonator antenna (DRA) element for dual polarization configuration operating at 26 GHz for 5G applications is presented in this paper. The new cross hybrid DRA unit cell is introduced which combines a cross shape DRA with a bottom loading cross microstrip patch. This technique of a bottom loading cross microstrip patch is chosen as the tuning mechanism (varying the length of the microstrip to tune the phase) instead of changing the DRA dimensions because of their ease of implementation and fabrication. By doing so, high reflection phase range with low reflection loss performance can be obtained, which is essential for a high bandwidth and high gain reflectarray for 5G applications. The design and simulation have been done using commercial software of CST MWS. The reflection loss, reflection phase and slope variation were analyzed and compared. A metallic cross microstrip patch of varying length placed beneath the DRA to act as the phase shifter to tune the phase and give smooth variation in slope with a large phase range. The proposed cross hybrid DRA unit cell provides a high reflection phase range of 342º and 1.8 dB reflection loss. The computed results are compared with experimental results revealing reasonable agreement, thereby confirming the viability of the design.

Eliciting Idiom Retention through Alliteration in a Classroom Activity

Alliteration comes up as one of the efforts that follow the notion of linguistic motivation in creating language retention and memorization to learners. Idiom is one of the language phenomena where alliteration takes place as part of its non-arbitrariness principle. The claim underlying the effectiveness of alliteration in aiding language retention in idiom is tried to be applied in some classroom activities which may consist of pre, whilst, and post-teaching. All the activities in the teaching session are arranged to be integrated with idiom learning using alliteration. Learners' ability to recall idioms containing aliteration will also be tested in the provided exercises. The success of the expected retention on learners will be measured from the result gained from the activity divided simply into three phases, pre-teaching, whilst-teaching, and post-teaching where it will be conducted for approximately 90 minutes. As some deviations possibly made can influence the result, the teacher should figure out some considerations affecting the effectiveness of the lesson given. Reflection phase should be conducted maximally, so that learners’ response is really fruitful that it can be known whether they are engaged with the activity and gain the material well. In the first activity, they work semi-independently, so that the assessment is expected to be more objective, covering the combination of group and individual work.

Construction of Optical Topological Cavities Using Photonic Crystals

A novel design of the Fabry–Pérot optical cavity is proposed, utilizing both the topological interface state structures and photonic bandgap materials with a controllable reflection phase. A one-to-one correspondence between the traditional Fabry–Pérot cavity and optical topological cavity is found, while the tunable reflection phase of the photonic crystal mirrors provides an extra degree of freedom on cavity mode selection. The relationship between the Zak phase and photonic bandgap provides theoretical guidance to the manipulation of the reflection phase of photonic crystals. The dispersions of interface states with different topology origins are explored. Linear interfacial dispersion emerging in photonic crystals with the valley–spin Hall effect leads to an extra n = 0 cavity mode compared to the Zak phase–induced deterministic interface states with quadratic dispersion. The frequency of the n = 0 cavity mode is not affected by the cavity length, whose quality factor can also be tuned by the thickness of the photonic crystal mirrors. With the recent help of topology photonics in the tuning reflection phase and dispersion relationship, we hope our results can provide more intriguing ideas to construct topological optical devices.

A wideband, compact, high gain, low-profile, monopole antenna using wideband artificial magnetic conductor for off-body communications

A wideband staircase pattern defected ground monopole antenna integrated with an artificial magnetic conductor (AMC) reflector has been proposed for C-band (4–8 GHz) and ITU band (8.01–8.5 GHz) applications. The integrated antenna consists of a staircase antenna at top, a 2 × 2 AMC reflector at the bottom and an air substrate as gap between them. The AMC offers 18.5% ± 90° reflection phase bandwidth from 6.10 to 7.32 GHz. The AMC layer has achieved mu-negative properties in the designated band. The AMC proffers polarization independent behavior in the respective frequency band depicting robustness in AMC reflection phase characteristics. The integrated antenna has offered a wide impedance bandwidth of 2.78 GHz (42.8% at 6.5 GHz and 34.1% at 8.15 GHz) due to the defected ground monopole. The integration of wideband AMC beneath the staircase monopole antenna alters the out of phase radiation to in-phase planer pattern which enhances the peak gain up to 9.7 dB. It reduces the 1-g averaged specific absorption rate to 0.223 and 0.324 W/kg at the two designated bands. The structure maintains almost similar bandwidth and gain due to artificial human body loading.