Sung-Pu Yang

This letter presents the design, fabrication, and characterization of a 4-to-2 optoelectronic encoder utilizing the light-emitting transistors (LETs) platform. By employing a GaAs-based heterojunction structure with an InGaAs quantum well (QW), the LET architecture significantly enhances light emitting, enabling efficient optical-to-electrical signal conversion. This marks the first successful demonstration of an LET-based encoder circuit, advancing monolithic integration for optical receiver applications and contributing to the development of high-performance optoelectronic systems. This work highlights the potential of LETs as a versatile platform for scalable and efficient photonic integrated circuits.

We report an optimized monolithic dual-wavelength distributed feedback (DFB) laser for terahertz (THz) applications, designed to address the challenges of complexity, cost, and power efficiency in a THz transmitter. This laser can achieve a high optical power of 65.93 mW. Under a wide temperature range and high-bias current, the power difference between the two primary modes remains below 1 dB, with each side-mode suppression ratio exceeding 36 dB. Additionally, the two primary modes exhibit low relative intensity noise peaks of −153.88 dB/Hz and −153.46 dB/Hz and narrow linewidths of 117.33 kHz and 70.59 kHz, demonstrating stable and high-performance dual-wavelength operation. These results underscore the potential of the dual-wavelength (DW)-DFB laser as a compact and cost-effective solution for THz systems.

In this letter, we present a 1.55- $\mu \text{m}$ DFB laser that possesses characteristics including high power, low noise, and high-speed direct modulation capabilities across a wide temperature range. The DFB laser demonstrates an optical power of 125.76-mW and sustains power exceeding 45-mW, with an SMSR surpassing 45-dB at 85°C. It exhibits the ability to modulate signals at frequencies exceeding 5.26-GHz and transmits a clear 10-Gb/s eye pattern. The RIN maintains as low as -153.51-dB/Hz within the dynamic range of 0–10-GHz, and even with the operating temperature increases, it still stays impressively low at -141.47-dB/Hz. Consequently, these outcomes indicate the 1.55- $\mu \text{m}$ DFB laser offers several advantages, reinforcing its potential as a promising device for satellite optical links.

Optical coupling between an external optical fiber and a silicon waveguide is vital for successful silicon photonics applications. Direct edge coupling has been desirable but challenging in the past to substitute for bulky, non-coplanar grating-assisted coupling. A silicon-cored fiber (SCF) is proposed as a novel solution for coplanar light coupling from an incoming fiber to a silicon waveguide. The simulation results show that an optimized polished conical SCF coupler can reach very high coupling efficiencies in both TE and TM modes and with low polarization dependence.

A silicon-cored-fiber (SCF) is used in, what we believe to be, a novel way for coplanar light coupling from an incoming fiber to a silicon waveguide on a chip. Two schemes of utilizing SCFs are investigated, namely a tapered SCF coupler and a D-shaped SCF coupler. A tapered SCF coupler is chosen for further optimization, leading to a coupling efficiency of ∼97% obtained from the results of 3D FDTD simulation.