High-performance Optical Receiver Research Articles

Gain and Excess Noise in HgCdTe e-Avalanche Photodiodes at Various Temperatures and Wavelengths

Avalanche photodiodes (APDs) can amplify the weak optical signal as well as enable higher receiver sensitivity due to the internal avalanche gain, but the impact ionization process can also introduce the “excess noise”, which limits the practically achievable signal-to-noise ratio (or sensitivity) and gain-bandwidth product. Hg <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{1} -\textit{x}}$</tex-math> </inline-formula> Cd <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\textit{x}}$</tex-math> </inline-formula> Te electron-initialed APDs (e-APD) have been demonstrated to exhibit high performance in terms of gain and excess noise at 77 K. Here, we discuss the gain and excess noise properties of multiple Hg <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{1}-\textit{x}}$</tex-math> </inline-formula> Cd <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\textit{x}}$</tex-math> </inline-formula> Te e-APDs with different Cd compositions targeting at short-wavelength infrared (SWIR), mid-wavelength infrared (MWIR), and long-wavelength infrared (LWIR) band operating at various temperatures. It demonstrates that the gain of APDs increases as the temperature decreases and the cutoff wavelength of the devices increases, which is related to the decrease of electron effective mass, optical photon scattering rate, and bandgap of the materials. In addition, the low excess noise of less than 1.6 at high gains is also achieved for the devices over a wide range of temperatures. The large spin-orbit splitting energy ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta $</tex-math> </inline-formula> so) in comparison to bandgap energy is considered to be responsible for the observed pure electron avalanche and exceptionally low excess noise. This work may provide insight into the low-noise HgCdTe APDs and is beneficial for the future applications of high-temperature operating and high-performance optical receivers.

An Equivalent Circuit Model for a Ge Waveguide Photodetector on Si

We present an equivalent circuit model with improved accuracy for 1.5-μm germanium waveguide-type vertical photodetectors on a silicon-on-insulator substrate. Our model consists of passive circuit components, two current sources for photogenerated carrier transports, and one noise current source. Model parameters are extracted from electrical S-parameter measurements, TCAD simulations of photodetection frequency responses, and noise measurements. The resulting equivalent circuit model accurately provides photodetection frequency responses at different bias voltages and should be of great use for high-performance optical receiver circuit design.

Recent Advances in Avalanche Photodiodes

Until the early 2000's, the avalanche photodiode (APD) was widely deployed in high-performance optical receivers that operated up to 10 Gb/s. In subsequent years, the use of APDs for high-capacity systems declined as a result of their limited gain bandwidth, the transition to coherent detection, and the development of high-efficiency modulation techniques. Recently, the rapid growth of optical-fiber communications systems that utilize baud rates up to 25 Gb/s represented by a 100-Gb/s Ethernet has led to a resurgence of research on APDs and the development of low-noise APDs with enhanced gain bandwidth. This paper presents a brief review of APD fundamentals and describes some of the recent advances.

High-performance Optical Receivers Using Conventional Sub-micron CMOS Technology for Optical Communication Applications

High-performance Optical Receivers Using Conventional Sub-micron CMOS Technology for Optical Communication Applications

Recent Advances in Avalanche Photodiodes

The development of high-performance optical receivers has been a primary driving force for research on III-V compound avalanche photodiodes (APDs). The evolution of fiber optic systems toward higher bit rates has pushed APD performance toward higher bandwidths, lower noise, and higher gain-bandwidth products. Utilizing thin multiplication regions has reduced the excess noise. Further noise reduction has been demonstrated by incorporating new materials and impact ionization engineering with beneficially designed heterostructures. High gain-bandwidth products have been achieved waveguide structures. Recently, imaging and sensing applications have spurred interest in low noise APDs in the infrared and the UV as well as large area APDs and arrays. This paper reviews some of the recent progress in APD technology.

High performance optical receiver module for10 Gbit/s applications with low cost potential

A high performance optical receiver module is presented which incorporates the monolithic integration of an InGaAs-pin photodiode with an InP HBT preamplifier packaged into a low cost TO46 module. A high receiver sensitivity of -16.0 dBm has been achieved at a data rate of 10 Gbit/s.

A high-performance optical receiver for 622 Mb/s direct-detection systems

A report is presented on the measurement of receiver sensitivity and noise characteristics of a high-performance optical receiver using a low-noise InGaAs avalanche photodiode (APD) and a low-noise high-electron mobility transistor (HEMT). At a bit rate of 622.08 Mb/s and a wavelength of 1.297 mu m, the measured receiver sensitivity is -48.3 dBm. This is equivalent to a sensitivity of 155 photons/b and is about 12 dB away from the quantum limit of 10 photons/b. >