Fully integrated multi-optoelectronic synthesizer for THz pumping source in wireless communications with rich backup redundancy and wide tuning range

Abstract

We report a monolithic photonic integrated circuit (PIC) for THz communication applications. The PIC generates up to 4 optical frequency lines which can be mixed in a separate device to generate THz radiation, and each of the optical lines can be modulated individually to encode data. Physically, the PIC comprises an array of wavelength tunable distributed feedback lasers each with its own electro-absorption modulator. The lasers are designed with a long cavity to operate with a narrow linewidth, typically <4 MHz. The light from the lasers is coupled via an multimode interference (MMI) coupler into a semiconductor optical amplifier (SOA). By appropriate selection and biasing of pairs of lasers, the optical beat signal can be tuned continuously over the range from 0.254 THz to 2.723 THz. The EAM of each channel enables signal leveling balanced between the lasers and realizing data encoding, currently at data rates up to 6.5 Gb/s. The PIC is fabricated using regrowth-free techniques, making it economic for volume applications, such for use in data centers. The PIC also has a degree of redundancy, making it suitable for applications, such as inter-satellite communications, where high reliability is mandatory.

Photonic integrated circuits for terahertz source generation

“…An optical micrograph of the four channel fully‐integrated optoelectronic synthesisers together with corresponding scanning electron microscopy (SEM) images are shown in Fig. 1 [8]. The fabrication processes and epitaxial structures are described in [13, 14], respectively.…”

“…Figure 7(a) shows a micrograph of the fabricated device using shallow etched ridge waveguides and sidewall gratings [5,8,9]. The DFB section was 1200 µm long.…”

“…Here we will introduce four kinds of PIC-based photonic sources that can be used to generate terahertz signals though photomixing: 1) an optoelectronic synthesizer for THz communications which can be tuned continuously from 0.254 to 2.723 THz [8]; 2) a dual-grating DWL DFB laser stabilised by four wave mixing (FWM) in an integrated electroabsorption modulator (EAM) where the lasing lines are separated by THz frequencies [6,9]; 3) a DWL using a sampled Bragg grating with a π-phase-shifted seed grating filling half of the sampling period [10]; 4) a THz source based on sampled grating distributed Bragg reflectors (SGDBR) SMLLDs [11,12]. In all of these PIC devices, the THz wave can be generated through difference-frequency generation (DFG) in a square law detector such as photodiode or photoconductive detector [8] or optical rectification in a nonlinear crystal. Except where noted, all the devices reported here were measured at 20 °C using a thermoelectric cooler (TEC) and operated under continuous wave (CW) biasing conditions.…”

Advanced Spatial-Division Multiplexed Measurement Systems Propositions—From Telecommunication to Sensing Applications: A Review

“…For instance, such opto-electronic sources can be integrated on the silicon platform on GaAs, Si and InP, etc. [ 106 , 107 ].…”

Photonic Terahertz Carrier Generation Using an Optical Feedback Mode-Lock Laser Diode

“…Recently, a THz quantum cascade laser with a frequency of 3.2 THz has been reported [1], but the need for cryogenic colling limits its practical application. Optical heterodyning of two optical wavelengths from a dual-wavelength laser (DWL) [2]- [4] or a mode-locked laser (MLL) [5]- [7] for THz generation provides a practical solution due to the simplicity in device structure and commercial availability.…”