Daniel Lasaosa

Ultrafast (370 GHz bandwidth) p-i-n traveling wave photodetector using low-temperature-grown GaAs

The authors demonstrate p-i-n traveling wave photodetectors utilizing low-temperature-grown GaAs as the absorption layer. The electro-optically measured impulse response was found to exhibit a pulsewidth of 1.1 ps full width at half maximum, corresponding to a −3 dB bandwidth of 370 GHz with an external quantum efficiency of 8% at 800 nm.

Selective undercut etching of InGaAs and InGaAsP quantum wells for improved performance of long-wavelength optoelectronic devices

In this paper, the authors show how selective undercut etching of InGaAs and InGaAsP-based quantum wells (QWs) can improve the performance of InP-based optoelectronic devices. First, wet-chemical-etching characteristics are investigated. Mixtures of sulphuric and hydrogen peroxide acids are used as wet-etching solutions, and properties such as etch rates, selectivity, and anisotropy are studied in detail. Problems arising from the anisotropic nature of the etching are analyzed, and their impact on device design and performance is discussed. Second, the authors present several optoelectronic devices where selective undercut etching of InGaAs- or InGaAsP-based multiquantum wells (MQWs) improves device performance; these devices include electroabsorption modulators (EAMs), vertical-cavity semiconductors optical amplifiers (VCSOAs), and waveguide amplifier photodetectors (WAPs). Very high extinction ratios were obtained for the EAM. A selective undercut-etched VCSOA reached a record-high 17-dB fiber-to-fiber gain, and the WAP demonstrated an external quantum efficiency higher than 100%

Traveling-wave photodetectors with high power-bandwidth and gain-bandwidth product performance

Traveling-wave photodetectors (TWPDs) are an attractive way to simultaneously maximize external quantum efficiency, electrical bandwidth, and maximum unsaturated output power. We review recent advances in TWPDs. Record high-peak output voltage together with ultrahigh-speed performance has been observed in low-temperature-grown GaAs (LTG-GaAs)-based metal-semiconductor-metal TWPDs at the wavelengths of 800 and 1300 nm. An approach to simultaneously obtain high bandwidth and high external efficiency is a traveling-wave amplifier-photodetector (TAP detector) that combines gain and absorption in either a sequential or simultaneous traveling-wave structure.

Traveling-wave amplification photodetector (TAP detector)

We study a novel type of device, the traveling-wave amplification photodetector (TAP detector). We show that, in a sequential configuration, these devices produce more gain than classical traveling-wave photodetectors (TWPDs) with optical preamplification for the same saturation power, while in a parallel configuration they present gain-bandwidth products similar to those of classical TWPDs, with much larger saturation power.

Modeling of traveling-wave amplification photodetectors (TAP detectors)

High speed, high efficiency, low noise and high saturation power are the characteristics desired for detectors in high bit-rate long-haul optical communication systems. We present the modeling of traveling-wave application photodetectors. These novel monolithic devices combine optical gain and absorption in a distributed fashion along a traveling-wave structure, providing high-responsivity and high-speed performance, without sacrificing saturation power. We present the models used to simulate the behavior of these devices, as well as their result. We show that TAP detectors have higher saturation power than other detectors with the same bandwidth-efficiency product, at the price of a small noise penalty, which is also calculated. The result is a net increase in the dynamic range.

Optimization of GaAs amplification photodetectors for 700% quantum efficiency

We investigate the device physics of novel GaAs waveguide photodetectors with integrated photon multiplication. Such detectors have the potential to achieve simultaneously high saturation power, high speed, high responsivity, and quantum efficiencies above 100%. Our device design vertically combines a bulk photodetector ridge waveguide region with laterally confined quantum wells for amplification. Measurements on the first device generation show quantum efficiencies of only 56%. Advanced device simulation is employed to analyze these devices and to reveal performance limitations. Excellent agreement between simulations and measurements is obtained. Device design optimization is proposed, promising more than 700% efficiency.

InP-based waveguide photodetector with integrated photon multiplication

We report on novel InP based traveling wave amplification photodetectors exhibiting an external quantum efficiency of more than 100%. Our detectors vertically combine a bulk InGaAs photodetector ridge region with laterally confined InGaAsP quantum wells for amplification. In addition to ultra high responsivities, such detectors have the potential to also achieve high saturation power and high speed. The device physics is discussed using advanced numerical simulation.

Physics of Waveguide Photodetectors with Integrated Amplification

The promising concept of waveguide photodetection with integrated amplification is evaluated by self-consistent device simulation. Such integrated amplification detectors have the potential to achieve simultaneously high saturation power, high speed, high responsivity, and quantum efficiencies well above one. Our example design vertically combines a bulk photodetector ridge region with laterally confined quantum wells for amplification. The current flow in the three-terminal device exhibits ground current reversal with increasing light power. The net optical gain is evaluated for different waveguide modes. For the dominating mode, the detector responsivity is shown to scale with the device length, reaching quantum efficiencies larger than 100%.

Recent advances in photodetectors with distributed optical amplification

For the past few years, we have been researching a novel type of photodetector featuring distributed optical amplification. We call these devices traveling-wave amplifier-photodetectors, or TAP detectors. The distributed combination of gain and absorption seeks a larger efficiency while keeping a low optical power, thus avoiding saturation. In this paper, we present experimental results both of GaAs- and InP-based TAP detectors, showing in the former case an external quantum efficiency larger than 200%, and larger than 100% in the latter. The performance limitation is shown to be related to the competition between the optical input signal and the amplified spontaneous emission (ASE) generated in the amplifier.

1.55 /spl mu/m traveling-wave amplification photodetector

We demonstrate a novel InP-based ridge-waveguide photodetector with monolithically integrated multiple-quantum well amplification layers. Performance limitations are analyzed using advanced device simulation and design optimizations are proposed.