Proposal of InGaAs/InAlAs multiple quantum well Mach–Zehnder modulator integrated with array of planar antennas

Abstract

We propose an InGaAs/InAlAs multiple quantum well (MQW) Mach-Zehnder modulator integrated with an array of gap-embedded planar antennas for 60 GHz band radio-over-fiber system. The modulator enables us to directly convert from wireless millimeter-wave (MMW) signals to light-wave signals without any connection cables. A newly designed MQW for the modulator exhibits a large refractive index change at low electric field owing to its unique quantum confined Stark effect, which can achieve push-pull driving in modulation without any external electrical power supply. In addition, by introducing a PIN structure to waveguides, an electric field induced in the antena gap can be applied to a core layer of the waveguide efficiently under the irradiation of MMW signals. The modulator with a 2-element array planar antenna can be driven under an MMW power density of 98 W m −2 . We theoretically discuss designs and characteristics of the MQW, planar antenna, and modulator.

Proposal of Highly Efficient Quantum Well Microring Resonator-Loaded Optical Phase Modulator Integrated with Antenna-Coupled Electrodes for Radio-over-Fiber

“…On the other hand, such a peak is not observed in the D-ACE curve because the impedance of the resonant electrode is changed by the MSL on the other side, and the resonance at 57.2 GHz is suppressed. Compared with the previously reported printed dipole type device with a pin junction [17], the D-ACE is approximately 1.63 times as large as |E z /E 0 |. Figure 12 shows the relationship between the electric field enhancement factor |E z /E 0 | and the distance ∆y from the center of the coupled microstrip resonant electrode to the feeding point of the MSL.…”

“…The electric-field-induced optical phase shift in the MRR waveguide is increased by the unique quantum confinement Stark effect (QCSE) in the FACQW and an enhanced phase shift in the MRR, while the ACE based on a coupled microstrip resonant electrode applies a strong standing wave electric field to the waveguide. Owing to the combination of these effects, the proposed modulator is expected to provide tens of times higher phase modulation efficiency than the previously reported gap-embedded planar antenna-integrated modulator [17]. Figure 1 shows a schematic of the proposed phase modulator, which employs Fedoped InP (Fe-InP) as a substrate to improve the ACE antenna characteristics; the straight part of the MRR waveguide is located along the edge on the gap side of the ACE to efficiently receive voltage signals enhanced as the odd mode.…”

“…However, there are some issues such as a relatively small change in refractive index induced by an electric field, large power consumption, poor integration with semiconductor light-emitting devices such as laser diodes (LDs), and enlargement and high losses of an entire system. To date, we reported a printed dipole antenna integrated phase modulator [17,18] with a multiple five-layer asymmetric coupled quantum well (FACQW) [19]. Its high-speed modulation under irradiation of MMW signals is experimentally demonstrated.…”

“…Each layer is lattice-matched to InP. The modulator is designed so that the absorption loss is small for the operation wavelength of 1550 nm [17]. Figure 2 shows the potential diagram of the InGaAs/InAlAs FACQW [ is used for a core layer of the waveguide in this modulator.…”

“…Each layer is la to InP. The modulator is designed so that the absorption loss is small for wavelength of 1550 nm [17]. Figure 4 shows a schematic cross-section of the waveguide for the MRR.…”