Continuous wave terahertz systems exploiting 15 µm telecom technologies

Abstract

A fiber-assembled CW THz System operating at 1.5 microm is presented. High speed telecom photodiodes integrated with planar THz antennas serve as THz emitters with power up to 10 microW. Photoconductive antennas based on LT InGaAs/InAlAs multi-layer structures allow coherent detection. The system operates in a wide frequency range of 0.1 -1.6 THz.

A Frequency-Multiplied Source With More Than 1 mW of Power Across the 840–900-GHz Band

“…Photonic solutions to coherent generation at terahertz frequencies have dominated the field for decades starting with far-infrared lasers able to produce tens of milliwatts of coherent power, to femtosecond infrared lasers and photoconductors that enable broadband terahertz sources suited for numerous spectro-imagery applications [5]. Photomixers are also an attractive solution for generating coherent terahertz continuous waves (CWs) thanks to their wide frequency tunability [6], [7]. Recently, quantum cascade lasers have made incursions into the sub-terahertz domain and are routinely delivering milliwatts or tens of milliwatts in the 1-4-THz range [8], [9] albeit at cryogenic temperatures and with limited bandwidth.…”

1550 nm ErAs:In(Al)GaAs large area photoconductive emitters

“…7 A reduction of the lifetime could be demonstrated by using low temperature grown InAlAs, showing efficient recombination, followed by InGaAs absorption regions in a superlattice. 3,8 Another option is heavy ion bombardment with high kinetic energy, generating efficient trap states. A lifetime of 0.46 ps has been reported.…”

Semiconductors for terahertz photonics applications

“…Low-temperature growth, Be-doped, and post growth annealed InGaAs/InAlAs MQWs were shown to result in subpicosecond photoresponses and electron concentration of the order of 10 16 cm -3 [107,108]. Recently, the problem of low temperature growth of InGaAs on InP substrates was approached by combining two techniques: conventional compensation of the donors by balanced doping with Be acceptors and by embedding thin (12 nm) photoconductive InGaAs layers between InAlAs barriers transparent at 1.5 µm wavelength [109,110]. LTG InAlAs layers are known to contain a large number of deep trapping centres [99], thus the residual electrons are captured in this material, resulting in a sheet resistivity of the order of 10 6 Ω/square.…”

“…LTG InAlAs layers are known to contain a large number of deep trapping centres [99], thus the residual electrons are captured in this material, resulting in a sheet resistivity of the order of 10 6 Ω/square. Such structures were used in pulsed THz components of a TDS system with an useable frequency range >2.5 THz [109] and in CW optical mixing system operated at frequencies up to 1.6 THz [110]; both systems were using 1.5 µm wavelength laser sources.…”