12 research outputs found
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Metal-semiconductor-metal ion-implanted Si waveguide photodetectors for C-band operation
Metal-semiconductor-metal Si waveguide photodetectors are demonstrated with responsivities of greater than 0.5 A/W at a wavelength of 1550 nm for a device length of 1mm. Sub-bandgap absorption in the Si waveguide is achieved by creating divacancy lattice defects via Si+ ion implantation. The modal absorption coefficient of the ion-implanted Si waveguide is measured to be ā185 dB/cm, resulting in a detector responsivity of ā0.51 A/W at a 50V bias. The frequency response of a typical 1mm-length detector is measured to be 2.6 GHz, with simulations showing that a frequency response of 9.8 GHz is achievable with an optimized contact configuration and bias voltage of 15V. Due to the ease with which these devices can be fabricated, and their potential for high performance, these detectors are suitable for various applications in Si-based photonic integrated circuits
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Helium-ion-induced radiation damage in LiNbOā thin-film electro-optic modulators
Helium-ion-induced radiation damage in a LiNbOā-thin-film (10 Ī¼m-thick) modulator is experimentally investigated. The results demonstrate a degradation of the device performance in the presence of Heāŗ irradiation at doses of ā„ 1016 cmā»Ā². The experiments also show that the presence of the Heāŗ stopping region, which determines the degree of overlap between the ion-damaged region and the guided optical mode, plays a major role in determining the degree of degradation in modulation performance. Our measurements showed that the higher overlap can lead to an additional ~5.5 dB propagation loss. The irradiation-induced change of crystal-film anisotropy(nāānā )of ~36% was observed for the highest dose used in the experiments. The relevant device extinction ratio, VĻL, and device insertion loss, as well the damage mechanisms of each of these parameters are also reported and discussed
Ar+-Implanted Si-Waveguide Photodiodes for Mid-Infrared Detection
Complementary metal-oxide-semiconductor (CMOS)-compatible Ar+-implanted Si-waveguide p-i-n photodetectors operating in the mid-infrared (2.2 to 2.3 Āµm wavelengths) are demonstrated at room temperature. Responsivities exceeding 21 mA/W are measured at a 5 V reverse bias with an estimated internal quantum efficiency of 3.1%ā3.7%. The dark current is found to vary from a few nanoamps down to less than 11 pA after post-implantation annealing at 350 Ā°C. Linearity is demonstrated over four orders of magnitude, confirming a single-photon absorption process. The devices demonstrate a higher thermal processing budget than similar Si+-implanted devices and achieve higher responsivity after annealing up to 350 Ā°C
Lead-related quantum emitters in diamond
We report on quantum emission from Pb-related color centers in diamond following ion implantation and high-temperature vacuum annealing. First-principles calculations predict a negatively charged Pb-vacancy (PbV) center in a split-vacancy configuration, with a zero-phonon transition around 2.4 eV. Cryogenic photoluminescence measurements performed on emitters in nanofabricated pillars reveal several transitions, including a prominent doublet near 520 nm. The splitting of this doublet, 5.7 THz, exceeds that reported for other group-IV centers. These observations are consistent with the PbV center, which is expected to have a combination of narrow optical transitions and stable spin states, making it a promising system for quantum network nodes.U.S. Army Research Laboratory. Center for Distributed Quantum InformationNational Science Foundation (U.S.). Graduate Research Fellowship ProgramNational Science Foundation (U.S.) (Grant DMR-1231319)United States. National Aeronautics and Space Administration (Space Technology Research Fellowship)MIT-Harvard Center for Ultracold Atoms MIT International Science and Technology Initiativ
Transform-limited photons from a coherent tin-vacancy spin in diamond
Solid-state quantum emitters that couple coherent optical transitions to
long-lived spin qubits are essential for quantum networks. Here we report on
the spin and optical properties of individual tin-vacancy (SnV) centers in
diamond nanostructures. Through cryogenic magneto-optical and spin
spectroscopy, we verify the inversion-symmetric electronic structure of the
SnV, identify spin-conserving and spin-flipping transitions, characterize
transition linewidths, measure electron spin lifetimes and evaluate the spin
dephasing time. We find that the optical transitions are consistent with the
radiative lifetime limit even in nanofabricated structures. The spin lifetime
is phononlimited with an exponential temperature scaling leading to
10 ms, and the coherence time, reaches the nuclear spin-bath limit upon
cooling to 2.9 K. These spin properties exceed those of other
inversion-symmetric color centers for which similar values require millikelvin
temperatures. With a combination of coherent optical transitions and long spin
coherence without dilution refrigeration, the SnV is a promising candidate for
feasable and scalable quantum networking applications
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Micro-Raman spectroscopic visualization of lattice vibrations and strain in He+- implanted single-crystal LiNbO3
Scanning micro-Raman spectroscopy has been utilized to image and investigate strain in He+-implanted congruent LiNbO3 samples. By using abruptly patterned implanted samples, we show that the spatial two-dimensional mapping of the Raman spectral peaks can be used to image the strain distribution and determine its absolute magnitude. We demonstrate that both short- and long-range length-scale in-plane and out-of-plane strain and stress states can be determined using the secular equations of phonon-deformation-potential theory. We also show that two-dimensional Raman imaging can be used to visualize the relaxation of strain in the crystal during low-temperature annealing
Self-Balancing Position-Sensitive Detector (SBPSD)
Optical position-sensitive detectors (PSDs) are a non-contact method of tracking the location of a light spot. Silicon-based versions of such sensors are fabricated with standard CMOS technology, are inexpensive and provide a real-time, analog signal output corresponding to the position of the light spot. An innovative type of optical position sensor was developed using two back-to-back connected photodiodes. These so called self-balancing position-sensitive detectors (SBPSDs) eliminate the need for external readout circuitry entirely. Fabricated prototype devices demonstrate linear, symmetric coordinate characteristics and a spatial resolution of 200 Ī¼m for a 74 mm device. PSDs are commercially available only up to a length of 37 mm. Prototype devices were fabricated with various lengths up to 100 mm and can be scaled down to any size below that