Device Saturation Behavior of Submillimeter-Wave Membrane Photonic Transmitters

Abstract

Ultrahigh-speed photodetectors and printed-circuit antennas construct photonic transmitters. In this letter, we studied the saturation behaviors of an edge-coupled membrane photonic transmitter based on low-temperature-grown GaAs. The saturation behaviors determine the optimized operation condition of photonic transmitters. Ultrahigh external light-terahertz (THz) conversion efficiency of 0.11% was achieved with 645-GHz radiation. According to our knowledge, this value is the highest reported external conversion efficiency of all photonic transmitters with radiation higher than 500 GHz. The high conversion efficiency and the edge-coupled structure of our devices release the power burden imposed on tunable semiconductor laser sources and imply their applications as compact all-solid-state THz radiation sources.

Traveling-Wave Photodetectors With High Power–Bandwidth and Gain–Bandwidth Product Performance

“…By utilizing the fully distributed microwave guiding property of the MSM-TWPD and a membrane antenna structure, we have also demonstrated a novel terahertz photonic transmitter [32], [33] with high conversion efficiency. Compared with other millimeter-or submillimeter-wave emission techniques such as Gunn diodes [54], p-type Ge-based or quantum cascade terahertz lasers [55], [56], and resonant tunneling diodes [57], photonic transmitters have the advantages of simplicity, compactness, wide tunability, and room temperature operations.…”

“…To test the performance of our fabricated device, the light source that we used was a mode-locked Ti:sapphire laser with 100-fs optical pulsewidth and 82-MHz repetition rate. By passing the broadband femtosecond optical pulses through etalons, we can increase the repetition rate of the light source to terahertz frequency range and trigger the photonic transmitters by coupling this high-repetition-rate light into the edge-coupled MSM-TWPD [32], [33]. The top view of our device is shown in Fig.…”

“…The top view of our device is shown in Fig. 6, which is composed of a MSM-TWPD, a radio frequency (RF) choke filter, and a planar antenna [33]. We adopted a CPW fed slot antenna because it can generate higher power than the spiral antenna in the designed resonant frequency [58] and can be easily integrated with the MSM-TWPD.…”

“…The RF choke filter, which acts as an inductance [41], avoids the high-frequency ac current (with a resonant frequency of the slot line antenna) leaking into the dc probe pad. We removed the GaAs substrate and mounted the membrane of the fabricated device on a glass substrate, which has a much lower dielectric constant than GaAs substrates and can thus allow the radiation of terahertz energy into the substrate or free space without using a Si lens [32], [33]. Fig.…”

“…By utilizing the good speed and output power performances of MSM-TWPD, we have also demonstrated the novel structure of an LTG-GaAs-based terahertz photonic transmitter [32]. By utilizing the fully distributed microwave guiding property of the MSM-TWPD, short carrier-trapping time of LTG-GaAs, and a membrane antenna structure, high conversion efficiency ( 1.1 10 ) can be achieved at 650-GHz frequency [33].…”