This article describes the novel design of printed and doubled-sided dipole array antennas with parallel reflector in the application of 2.4 GHz ISM band operated in WiFi access point. The printed dipole array antenna consists of one dipole array arranged back to back and can be easily formed by printing on both sides of a dielectric substrate and is suitable for integration with monolithic microwave integrated circuit (MMIC) module. Based on the matching theory, a 50 ⍀ microstrip feed line with open stub matched circuits is determined to possess high performance. The all extremely wideband or high gain dipole antenna array for value of standing wave ratio (VSWR) Յ 1.5 has been successfully implemented and achieved. Simulator IE3D is used to verify our analysis. Both simulated and measured data are much identical. The designed 8-element printed dipole array antenna without and with a reflector metallic ground plane achieves a gain of 8.5-9.3 dB with a 200 MHz bandwidth and a gain of 11.4 -12.3 dB with a 80 MHz bandwidth, respectively.

An angle-dependent surface photovoltage spectroscopy ͑SPS͒ study has been performed at room temperature on a GaAs/GaAlAs-based vertical-cavity-surface-emitting-laser ͑VCSEL͒ structure emitting at a wavelength near 850 nm. For comparison purposes, we have also measured the angle-dependent reflectance ͑R͒. The surface photovoltage spectra exhibit both the fundamental conduction to heavy-hole ͑1C-1H͒ excitonic transition and cavity mode plus additional interference features related to the properties of the mirror stacks, whereas in the R spectra only the cavity mode and interference features are clearly visible. The energy position of the excitonic feature is not dependent on the angle of incidence, in contrast to that of the cavity mode, whose angular dependence can be fitted with a simple model. This study demonstrates the considerable potential of angle-dependent SPS for the contactless and nondestructive characterization of VCSEL structures at room temperature.

Articles you may be interested inDifferential surface photovoltage spectroscopy characterization of a 1.3 μm InGaAlAs/InP vertical-cavity surfaceemitting laser structure An angle-dependent wavelength-modulated differential-photovoltage spectroscopy ͑DPVS͒ investigation has been performed at room temperature on a bare as-grown wafer of GaAs/ GaAlAs-based vertical-cavity surface-emitting laser ͑VCSEL͒ structure, designed for emitting at a wavelength near 850 nm. The differential-photovoltage ͑DPV͒ spectra exhibit both the fundamental conduction to heavy-hole excitonic transition and cavity mode plus an interference pattern related to the mirror stacks. By changing the angle of incidence in the DPV measurements the energy positions of the cavity mode and distributed Bragg reflector features show a blueshift while the excitonic transition remains unchanged. The energies of the excitonic transition and cavity mode are accurately determined from the DPV spectra. The advantages of DPVS in relation to other methods of characterizing VCSEL structures, such as surface photovoltage, photoreflectance, photocurrent, and differential photocurrent spectroscopy, are discussed. The results demonstrate considerable potential of DPVS for the nondestructive characterization of these structures at room temperature.

We have investigated a 1.3 m InGaAlAs/InP vertical-cavity surface-emitting laser ͑VCSEL͒ structure using angle-and temperature-dependent wavelength-modulated differential surface photovoltage spectroscopy ͑DSPS͒. The DSPS measurements as functions of incident angle and temperature have been carried out in the ranges 0°рр60°and 300 KрTр420 K, respectively. Angle-dependent reflectance ͑R͒ and surface photovoltage spectroscopy ͑SPS͒ measurements have also been performed to illustrate the superior features of the DSPS technique. The differential surface photovoltage ͑DSPV͒ and SPV spectra exhibit both the fundamental conduction to heavy-hole excitonic transition of quantum well and cavity mode ͑CM͒ plus a rich interference pattern related to the mirror stacks, whereas in the R spectra only the CM and interference features are clearly visible. The energies of the excitonic transition and CM are accurately determined from the DSPV spectra. By changing the angle of incidence in the DSPS measurements the energy positions of the CM and distributed Bragg reflector features show a blueshift while the excitonic transition remains unchanged. At a fixed incident angle, the energy positions of the excitonic feature and CM show a different rate of redshift with increasing temperature, with the latter at a much slower pace. The results demonstrate considerable potential of DSPS for the nondestructive characterization of the VCSEL structures.

We have investigated an 850 nm GaAs/GaAlAs (001) vertical-cavity surface-emitting laser (VCSEL) structure using angle- and temperature-dependent surface photovoltage spectroscopy (SPS). The SPS measurements were performed as functions of angle of incidence (0° ≤ θ ≤ 60°) and temperature (25° C ≤ T ≤ 215° C) for both the metal–insulator–semiconductor (MIS) and wavelength-modulated MIS configurations. Angle-dependent reflectance (R) measurements have also been performed to illustrate the superior features of the SPS technique. The SPS spectra exhibit both the fundamental conduction to heavy-hole excitonic transition of quantum well and cavity mode (CM) plus a rich interference pattern related to the mirror stacks, whereas in the R spectra only the CM and interference features are clearly visible. The variations of SPS spectra as functions of incident angle and temperature enable exploration of light emission from the quantum well confined in a microcavity with relation to the Fabry–Pérot cavity mode. The results demonstrate considerable potential of SPS for the contactless and nondestructive characterization of VCSEL structures.