Integrated polarizer components with polarization extinctions 40 dB are desirable for state-of-the-art photonic integrated circuits. We demonstrate 60-dB polarization extinction from a single-chip InGaAsP-InP broadband source by combining an edge light-emitting diode consisting of compressively strained quantum wells (QWs) with an absorber consisting of tensile strained QWs. A 600-m polarizer exhibits only 5 dB of insertion loss.

We have fabricated AlGaAs/GaAs/GaN heterojunction bipolar transistors (HBTs) formed by direct wafer fusion with different fusion temperatures. By employing a low wafer fusion temperature of 550 degC, current gains as high as ~9 and output currents as high as ~65 mA (emitter size of 100times120 mum2) were obtained. The effective minority carrier lifetime in the base was estimated to have decreased ~20 times due to the fusion process. In comparison, HBTs produced with higher wafer fusion temperatures (600 degC and 650 degC) exhibit lower current gains (~2-3) and higher base-collector leakage currents

High spee 98 nm VCSELs with tapere oxi e apertures were esigne an fabricate The evices show > GHz ban wi ths for bias currents between an 4 mA Open eyes up to 3 Gb s are a so emonstrate.

Short-cavity, 980nm DBR lasers with integrated EAMs were designed and fabricated using a quantum well intermixing processing platform. Open eyes at 40Gb/s and preliminary error free operation at 25Gb/s were, suitable for optical interconnect applications.

Band-edge absorption spectra from bulk, quantum-well, and quantum-well-intermixed InGaAsP material are collected and compared using photocurrent spectroscopy. The expected performances of ideal electroabsorption modulators fabricated from these materials are predicted and compared using the band-edge absorption data. A graphical method for simultaneously considering chirp, insertion-loss, extinction-ratio, and tuning range is presented, and is used to compare the suitability of the various materials for electroabsorption modulator applications. The quantum-well material is shown to be superior to bulk material for most EAM applications. Quantum wells with 85 meV conduction band depth and 80 A width are shown to be superior to quantum wells with 120 meV conduction band depth and 65 A width. Both well designs exhibit strong excitons. Finally, the effect of quantum-well intermixing is considered, and the expected performances of quantum-well-intermixed electroabsorption modulators are presented. (c) 2006 Elsevier Ltd. All rights reserved.

The authors have compared AlGaAs∕GaAs∕GaN heterojunction bipolar transistors (HBTs) formed by wafer fusion with AlGaAs∕GaAs∕GaAs as-grown HBTs subject to high temperature annealing conditions similar to those used in the wafer fusion process. The high temperature annealing alone is found to cause gain degradation by a factor of 2–6, a result of reduction in minority carrier lifetime in the base. Detailed analysis indicates that the fused HBTs also suffer from higher recombination in the emitter-base junction, exacerbated base degradation as well as effective potential barriers formed at the GaAs base/GaN collector junction.

Short-cavity, 980 nm distributed Bragg reflector (DBR) lasers with integrated electroabsorption modulators (EAMs) were designed and fabricated using a quantum-well intermixing (QWI) processing platform. Design curves are discussed and the QWI fabrication details are presented. The transmitters exhibited RF bandwidths of 20 GHz and demonstrated error-free operation at 10 Gb/s.

We present revised widely-tunable vertical-cavity SOAs exhibiting a reduced tuning voltage and an increased wavelength tuning range. Additionally, detailed theoretical models have been developed and are shown to be in good agreement with experimental observations.

A separate absorption, charge, and multiplication In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode with an impact-ionization-engineered multiplication region is reported. By implementing an electric field gradient in the multiplication region, better control of impact-ionization can be achieved. Gain-bandwidth product of 160 GHz and excess noise factor with an equivalent k value of 0.1 are demonstrated.

It is shown that optimization of the electric field profile in the absorption region of separate absorption, charge, and multiplication InGaAs-InAlAs avalanche photodiodes is critical to achieve low excess noise and high gain bandwidth product.

The mixing of near-infrared and terahertz THz beams has been observed in n-doped GaAs quantum wells QWs and is shown to be quite different from that in undoped QWs. The resonant behavior of the sidebands demonstrates that mixing in doped QWs is primarily sensitive to electronic intersubband transitions while that in undoped QWs is due to excitonic intersubband transitions. These results demonstrate that THz-optical mixing can be used to probe the collective dynamics of a driven electron gas.

In this paper, we present the fabrication and regrowth of first order, high contrast, AlGaAs/GaAs Bragg gratings for short-wavelength applications. The gratings are employed as reflectors in a distributed Bragg reflector (DBR) laser emitting at 980 nm. We first present a novel immersion holography technique used to fabricate the first order short-wavelength gratings. Next, we discuss a matrix of regrowth experiments used to overgrow high contrast gratings. Solid source Molecular Beam Epitaxy (MBE) was used for regrowth, and atomic force microscopy (AFM) and scanning electron microscope (SEM) were used to characterize the gratings and quality of overgrowth. Finally, results of these gratings monolithically integrated into a DBR laser are presented. High contrast, first order gratings are important technologically because of the high reflectivity with a small footprint. There are two main methods of patterning diffraction gratings—direct e-beam writing and holography. Standard holography is attractive due to its ease of fabrication, high throughput, and low cost. In our holography setup, a HeCd laser emitting at 325 nm was used as the source. However, to achieve the short grating pitch of ~150 nm necessary for our first-order 980 nm gratings, the wavelength of the laser source was reduced via a prism. Xylene was used to adhere the sample to the prism and also act as an index-matching fluid. This immersion holography technique was thereby effective in patterning uniform gratings at a shorter pitch. The exposed grating pattern is then transferred directly to the semiconductor via dry etching, and the sample is cleaned and prepared for regrowth. MBE regrowth has generally been considered a difficult or impractical growth technique for smooth overgrowth of gratings. Chemical vapor deposition is more commonly used due to the high mass transport properties [1]. In this work, MBE regrowth has been successfully achieved on patterned gratings. The gratings were targeted to have a high coupling coefficient, κ ~ 650 cm. Therefore, Al0.75Ga0.25As was used to overgrow GaAs gratings that were ~300 Å deep. Similar to work performed by Pickrell, et. al., we find that a slow growth rate is effective in overgrowing the gratings [2]. By growing at a slow growth rate, pitting defects are greatly reduced. Finally, substrate temperature and Arsenic overpressure were optimized to achieve both smooth overgrowth in non-grating regions as well as filled overgrowth over grating regions. The high contrast, first order gratings were monolithically integrated into a DBR laser to evaluate its performance as a mirror [3]. The devices demonstrated single mode lasing at 978 nm with >30 dB side mode suppression. The lasers had a threshold current of 9 mA, and had output powers >5 mW. In summary, first order, high contrast, AlGaAs/GaAs diffraction grating have been developed and implemented into a DBR laser emitting at 980 nm. A novel immersion holography technique has been developed to fabricate highly uniform gratings. Optimum regrowth conditions were found to overgrow and fill in the gratings. These gratings were successfully integrated in a DBR laser structure resulting in single mode emission at 980 nm.

An InGaAs quantum well driven by a strong THz field has exhibited a splitting of the exciton line, due to strong coupling of hole states. This effect is closely-related to the Autler-Townes effect and electromagnetically-induced-transparency.

We present the signal gain, wavelength tuning characteristics, saturation properties, and noise figure (NF) of MEMS-based widely tunable vertical-cavity semiconductor optical amplifiers (VCSOAs) for various optical cavity designs, and we compare the theoretical results to data generated from a number of experimental devices. Using general Fabry-Pe/spl acute/rot relationships, it is possible to model both the wavelength tuning characteristics and the peak signal gain of tunable vertical-cavity amplifiers, while a rate-equation analysis is used to describe the saturation output power and NF as a function of the VCSOA resonant wavelength. Additionally, the basic design principles for an integrated electrostatic actuator are outlined. It is found that MEMS-tunable VCSOAs follow many of the same design trends as fixed-wavelength devices. However, with tunable devices, the effects of varying mirror reflectance and varying single-pass gain associated with the MEMS-based tuning mechanism lead to changing amplifier properties over the wavelength span of the device.

We present bottom-emitting tunable vertical-cavity semiconductor optical amplifiers (VCSOAs) with an effective wavelength tuning range of > 20 nm. These devices utilize a high reflectivity micromechanically tunable Bragg mirror as the back reflector. Compared with our first generation tunable VCSOAs, the bottom-emitting devices exhibit a two-fold increase in the effective tuning range as well as a five-fold reduction in the required tuning voltage.

Short-cavity InGaAs/GaAs/AlGaAs lasers with first order DBRs and integrated EAMs were fabricated using a quantum well intermixing process. >5mW output was achieved at 45mA. DC extinction was >15dB at -1.5V with efficiencies up to 20dB/V.

Nonlinear mixing of terahertz and near-infrared radiation is observed for the first time in an n-doped GaAs quantum well. The resonant structure of three-wave mixing is much simpler than in undoped quantum wells

We present stable polarization of a long-wavelength vertical-cavity surface-emitting laser (LW VCSEL). The polarization control was achieved through growing its active region on a (113)B InP substrate, which was integrated to [001] GaAs-based distributed Bragg reflectors by a wafer-bonding technique. Theoretical investigation showed that to achieve high polarization stability, a large dichroism such as an anisotropic gain is needed. It was also shown that the (113)B and other planes of the (11n) family have asymmetry, which results in asymmetric stress and anisotropic optical gain in a strained multiquantum well. An index-guiding mesa structure was fabricated in an asymmetric shape. The index guiding either enhanced or distracted the polarization stability originating from gain anisotropy, depending on its orientation of the asymmetry, as was confirmed by a statistical summary. Using a VCSEL with an appropriate index-guiding structure, we performed 1-Gb/s modulation and confirmed single polarization under large-signal modulation.

We present the first microelectromechanical tunable vertical-cavity semiconductor optical amplifier. The device operates in the long wavelength range and exhibits a minimum of 10 dB of device gain through 11 nm of tuning.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text G. Cole, Q. Chen, S. Björlin, T. Kimura, S. Wu, C. Wang, J. Bowers, and N. MacDonald, "Wavelength selection in MEMS tunable vertical-cavity SOAs," in Optical Amplifiers and Their Applications/Integrated Photonics Research, Technical Digest (CD) (Optica Publishing Group, 2004), paper OMB3. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article