Showing papers on "Photodetection published in 2008"

Enhanced Sensitivity of Photodetection via Quantum Illumination

Abstract: The use of quantum-mechanically entangled light to illuminate objects can provide substantial enhancements over unentangled light for detecting and imaging those objects in the presence of high levels of noise and loss. Each signal sent out is entangled with an ancilla, which is retained. Detection takes place via an entangling measurement on the returning signal together with the ancilla. This paper shows that for photodetection, quantum illumination with m bits of entanglement can in principle increase the effective signal-to-noise ratio by a factor of 2 m , an exponential improvement over unentangled illumination. The enhancement persists even when noise and loss are so great that no entanglement survives at the detector.

Photodetection in Silicon Beyond the Band Edge with Surface States

Abstract: Silicon is an extremely attractive material platform for integrated optics at telecommunications wavelengths, particularly for integration with CMOS circuits. Developing detectors and electrically pumped lasers at telecom wavelengths are the two main technological hurdles before silicon can become a comprehensive platform for integrated optics. We report on the generation of free carriers in unimplanted SOI ridge waveguides, which we attribute to surface state absorption. By electrically contacting the waveguides, a photodetector with a responsivity of 36 mA/W and quantum efficiency of 2.8% is demonstrated. The photoconductive effect is shown to have minimal falloff at speeds of up to 60 Mhz.

Improving Sensitivity and Spectral Efficiency in Direct-Detection Optical OFDM Systems

Abstract: Analysis and simulations show that boosting the carrier power relative to the sideband just prior to photodetection, using an optical filter, will significantly increase the sensitivity and spectral efficiency of direct-detection optical orthogonal frequency-division multiplexed systems.

Single charged quantum dot in a strong optical field: absorption, gain, and the ac-Stark effect.

Abstract: We investigate a singly charged quantum dot under a strong optical driving field by probing the system with a weak optical field. We observe all critical features predicted by Mollow for a strongly driven two-level atomic system in this solid state nanostructure, such as absorption, the ac-Stark effect, and optical gain. Our results demonstrate that even at high optical field strengths the electron in a single quantum dot with its dressed ground state and trion state behaves as a well-isolated two-level quantum system.

High-Performance Waveguided Ge-on-SOI Metal–Semiconductor–Metal Photodetectors With Novel Silicon–Carbon (Si : C) Schottky Barrier Enhancement Layer

Abstract: We report the demonstration of waveguided germanium-on-silicon-on-insulator metal-semiconductor-metal (MSM) photodetectors with novel silicon-carbon (Si:C) Schottky barrier enhancement layer. Significant suppression of dark current (/dark) by ~4 orders of magnitude was achieved over a conventional MSM photodetector due to an enhanced hole Schottky barrier height of 0.52 eV. At an applied bias VA of 1.0 V a -3-dB bandwidth of ~12 GHz at an incident wavelength of 1550 nm was demonstrated. Optical measurements performed at photon wavelengths lambda of 1520-1570 nm reveal a uniform spectral response and quantum efficiency of ~760 mA/W and ~60%, respectively, demonstrating an effective photodetection for the entire C-band spectrum range.

Novel NiGe MSM Photodetector Featuring Asymmetrical Schottky Barriers Using Sulfur Co-Implantation and Segregation

Abstract: We report the first demonstration of a novel germanium (Ge) metal-semiconductor-metal (MSM) photodetector featuring asymmetrical Schottky-barrier height for low dark current and high-speed photodetection applications. Through co-implantation and segregation of valence-mending adsorbate such as sulfur at the NiGe/Ge interface, the germanide Fermi level can be pinned close to the conduction band edge. This results in an effective modulation of hole Schottky-barrier height, leading to a significant dark current suppression by >3 orders of magnitude over a conventional MSM photodetector. When operated at a bias voltage VA of 1.0 V, a detector with an area of 804 mum2 shows a spectrum response of ~ 0.36 A/W or a corresponding quantum efficiency of ~ 34%. In addition, a frequency response measurement reveals the achievement of a -3-dB bandwidth of ~15 GHz at an illumination photon wavelength of 1550 nm.

Enhanced 400-600 nm photoresponsivity of metal-oxide-semiconductor diodes with multi-stack germanium quantum dots

Abstract: Metal–oxide–semiconductor (MOS) diodes with zero-, one- or three-layer Ge quantum dots (QDs) embedded in the gate oxide are fabricated for visible to near-ultraviolet photodetection. Ge dots are formed by thermally oxidizing one or three stacks of amorphous Si (a-Si)/polycrystalline-Si0.87Ge0.13/a-Si multi-layers that are sandwiched by SiO2 barriers. The current–voltage characteristics of Ge QD MOS diodes exhibit strong rectification in darkness and feature significant current enhancement in the inversion mode when illuminated. Increasing the number of Ge QD layers from zero through one to three in the gate oxide improves the responsivity from 4.64 through 482 to 812 mA W−1 and enhances the corresponding quantum efficiency from 1.42 through 148 to 245%, respectively. The spectral response reveals a considerable blueshift in peak energies as the Ge dot size decreases from 9.1 to 5.1 nm, suggesting that the light absorption originates from the quantum confinement effect of Ge QDs. The temperature and bias dependences of the dark current indicate that the carrier transport mechanism involves percolation hopping.

Quantum memory with optically trapped atoms.

Abstract: We report the experimental demonstration of quantum memory for collective atomic states in a fardetuned optical dipole trap. Generation of the collective atomic state is heralded by the detection of a Raman scattered photon and accompanied by storage in the ensemble of atoms. The optical dipole trap provides confinement for the atoms during the quantum storage while retaining the atomic coherence. We probe the quantum storage by cross correlation of the photon pair arising from the Raman scattering and the retrieval of the atomic state stored in the memory. Nonclassical correlations are observed for storage times up to 60 � s.

Laser surveying system and distance measuring method

Abstract: A laser surveying system, comprising a light source for emitting a laser beam, a projection optical system for turning the laser beam from the light source to a parallel luminous flux, a scanning unit for projecting the luminous flux of the projected laser beam for scanning, a scanning direction detecting unit for detecting a scanning direction, a photodetection optical system for receiving a reflected light of the projected laser beam from an object to be measured, a photodetection element for performing photo-electric conversion of the reflected light received via the photodetection optical system, and a distance measuring unit for measuring a distance based on a signal from the photodetection element, wherein the projection optical system has a luminous flux diameter changing means, and a luminous flux diameter of the projected laser beam is enabled to be changed

Coherently driven semiconductor quantum dot at a telecommunication wavelength

Abstract: We proposed and demonstrate use of optical driving pulses at a telecommunication wavelength for exciton-based quantum gate operation. The exciton in a self-assembled quantum dot is coherently manipulated at 1.3 µm through Rabi oscillation. The telecom-band exciton-qubit system incorporates standard optical fibers and fiber optic devices. The coherent manipulation of the two-level system compatible with flexible and stable fiber network paves the way toward practical optical implementation of quantum information processing devices.

Photodetection semiconductor device, photodetector, and image display device

Abstract: Shields (61) that transmit light to be detected and have conductivity and are disposed on light receiving surfaces of photodiodes (1 and 2) to prevent electric charges from being induced to the photodiodes (1 and 2) by electromagnetic waves entered from an external. Two kinds of filters (61) having light transmittance depending on a wavelength of light are disposed on the light receiving surfaces of the photodiodes (1 and 2), respectively, to take a difference between their spectral characteristics. The shield and filter (61) may be made of, for example, polysilicon or a semiconductor thin film of a given conductivity type, and may be readily manufactured by incorporating those manufacturing processes into a semiconductor manufacturing process.

Optical ac coupling to overcome limitations in the detection of optical power fluctuations.

Abstract: A high-sensitivity detection method for optical power fluctuations is demonstrated based on photodetection in reflection of an optical resonator with a specific impedance matching. That resonator is used to reduce the carrier power reflected by the resonator while preserving the power fluctuation sidebands for frequencies above the resonator bandwidth. A sensitivity of 7 x 10(-10) Hz(-1/2) for relative power fluctuations was achieved with only 3 mA of detected photocurrent and 99.6% of the power remained for downstream experiments. As in the widely used ac coupling of electrical signals, this technique overcomes dynamic-range limits and reduces detector noise associated with large carrier amplitudes of the optical field.

Photon statistics of V-type three-level system in single quantum dots

Abstract: Based on the generating function approach developed recently, the theoretical study of the photon emission statistics in single InGaAs∕GaAs quantum dots is presented. We show the X- and Y-polarized photon emission statistics, the joint probabilities and marginal probabilities of V-type three-level system in single quantum dots driven by single pulse and a pair of pulses, respectively. The first moment confirm known experimental results while the Mandel’s Q parameters results display complex behaviors.

Theory of Superconductive Traveling-Wave Photodetectors

Abstract: This paper studies the theory of traveling-wave photodetection in superconductive multilayer optical waveguides, as a general platform for ultrafast, ultrasensitive, and ultralow-noise optoelectronics. The kinetic inductance theory of superconductive thin films and the modified transmission line theory are employed to investigate the distributed photodetection and signal generation mechanisms in superconductive traveling-wave devices. A general model for calculation of the optical responsivity of superconductive traveling-wave photodetectors is developed and operation regimes of interest are highlighted. Moreover, the inclusion of a photoconductive layer in the device structure and some important loading schemes are discussed and their effects on the device performance, such as quantum efficiency and electrical bandwidth, are addressed.

Photo-detection device and image display device

Abstract: Provided is a photodetection device which is small in size and has excellent sensitivity. The photodetection device (10) puts cathode terminals of photodiodes (1 and 2) having different spectral characteristics, or a photodiode (1) provided with an optical filter and a photodiode (2) provided with a light shield layer, into an open end state, and detects light intensity of a desired wavelength region according to a difference in electric charges that have been stored in those photodiodes in a given period of time. Since the photodiodes 1 and 2 store electric charges, even if a photocurrent is small, it is possible to store the photocurrent to obtain the electric charges required for detection, permitting achievement of downsizing and high detection performance of the semiconductor device on which the photodiodes 1 and 2 are formed. It is also possible to realize a wide dynamic range by making the electric charge storage time variable according to the light intensity, to suppress electric power consumption by intermittently driving an element required for differential detection at the time of differential detection, and to reduce an effect from flicker by averaging the output.

Analogs of time-dependent quantum phenomena in optical fibers

Abstract: Review of the paraxial approximation to the problem of light beams propagating in optical fibers is presented. The analogy of time-dependent integrals of motion for the quantum system and space-dependent invariants for the radiation in inhomogeneous optical waveguides is elucidated. A specific tomographic probability distribution associated with the light-pulse profile is considered analogously to tomographic probabilities in quantum mechanics. The new inequality is presented for the tomographic probability.

Investigation of quantum coherence excitation and coherence transfer in an inhomogeneously broadened rare-earth doped solid.

Abstract: Quantum coherence excitation onto spin ensembles by resonant Raman optical fields and coherence transfer back to an optical emission are discussed in a three-level optical system composed of inhomogeneously broadened spins, where the spin decay time is much slower than the optical decay time. Dynamic quantum coherent control of the spin excitations and coherence conversion are also discussed at a strong coupling field limit for practical applications of optical information processing.

Reversible quantum optical data storage based on resonant Raman optical field excited spin coherence.

Abstract: A method of reversible quantum optical data storage is presented using resonant Raman field excited spin coherence, where the spin coherence is stored in an inhomogeneously broadened spin ensemble. Unlike the photon echo method, in the present technique, a 2π Raman optical rephasing pulse area is used and multimode (parallel) optical channels are available in which the multimode access gives a great benefit to quantum information processors such as quantum repeaters.

HBT Optoelectronic Mixer Design for Radio over Fiber System

Abstract: Radio over fiber (RoF) system is the solution for the providing highly reliable communication service This system is characterized by having both a fiber optic link and free-space radio path to exploit the synergy of two complementary technologies; the broadband mobile wireless access and fixed optical access Optoelectronic mixing is required in RoF systems to detect the RF modulated optical signal and perform frequency up-conversion In this work, three-terminal InP/InGaAs HBT with optical access has been used as the optoelectronic mixer (OEM) for front-end RoF optical receiver configuration Thus in this configuration, the photodetection and frequency conversion can be achieved in p-i-n photodiode and HBT device, which considerably simplify the conventional method The RoF OEM was successfully simulated using a nonlinear microwave simulator to perform harmonics balance analysis, which represented actual photodetection model and nonlinear dynamic optoelectronic mixing behavior In this paper we reported the - 52 dB maximum internal mixing efficiency for 400 MHz IF modulated signal to 34 GHz upconverted RF signal with LO power is -2dBm, and that agreed with conventional theoretical analysis In this article, the theory of operation, the device structure of the RoF OEM and its characteristic will be presented

Laser measuring system

Abstract: A laser measuring system, which comprises a laser rotary irradiation device for forming a laser reference plane by projecting a laser beam in rotary irradiation, and a photodetection device for performing position measurement by receiving the laser beam, wherein the laser rotary irradiation device comprises a laser beam emitter, an emission light amount adjusting means for adjusting light amount of the laser beam of the laser beam emitter, and a first communication means for performing communication with said photodetection device, and wherein the photodetection device comprises a photodetector for detecting the reference plane, a second communication means for performing communication to and from the laser rotary irradiation device, and a control unit for calculating whether a photodetection signal from the photodetector is within a predetermined range or not, wherein the first communication means transmits a laser beam emitting condition of the laser rotary irradiation device to the second communication means, and the second communication means transmits a photodetecting condition of the photodetection device to the first communication means.

Quantum computing over the rainbow

Abstract: Laser beams made up of millions of sharply defined and coherently locked optical frequencies, called optical frequency combs, may provide a way to implement a powerful quantum computer.

Self-Oscillating Harmonic Opto-Electronic Mixer Based on a CMOS-Compatible Avalanche Photodetector for Fiber-Fed

Abstract: A self-oscillating harmonic opto-electronic mixer based on a CMOS-compatible avalanche photodetector for fiber-fed 60-GHz self-heterodyne systems is demonstrated. The mixer is composed of an avalanche photodetector fabricated with 0.18- m standard CMOS process and an electrical feedback loop for self oscillation. It simultaneously performs photodetection and frequency up-conversion of photodetected signals into the second harmonic self-oscillation frequency band. The avalanche photodetector and the mixer are characterized and analyzed, and the RF avalanche multiplication factor is investigated. In addition, conversion efficiency as well as internal conversion gain is determined, and bias conditions are optimized for the best self-oscillating harmonic opto-electronic mixer performance. Data transmission of 5-MS/s 32 quadrature amplitude modulation signals using self-oscillating harmonic opto-electronic mixer is successfully demonstrated.

Intraband Auger effect in InAs∕InGaAlAs∕InP quantum dot structures

Abstract: InAs quantum dot structures grown on InGaAlAs have been investigated for midinfrared photodetection. Intraband photocurrent and absorption measurements, together with a full three-dimensional theoretical modeling revealed that a bound-to-bound optical transition, where the final state is about 200meV deep below the conduction band continuum, is responsible for the photogenerated current. The reported results strongly suggest that an Auger process plays a fundamental role in generating the observed intraband photocurrent. Photoluminescence and interband photocurrent spectra of the same structures further support the reached conclusions.

Generation of non-classical states from an optical parametric oscillator/amplifier and their applications

Abstract: Quantum information and quantum optics are rapidly advancing areas of modern physics. As an important device in quantum optics and quantum information, the optical parametric amplifier/oscillator (OPA/O) has been extensively studied and applied to the generation of non-classical state since the 1980s. This article reviews the progress in the generation of non-classical state from an OPO/A and application of twin beams in quantum optics and quantum information

Observation of an inter-Landau level quantum coherence in semiconductor quantum wells

Abstract: Using three-pulse four-wave-mixing femtosecond spectroscopy, we excite a nonradiative coherence between the discrete Landau levels of an undoped quantum well and study its dynamics. We observe quantum beats that reflect the time evolution of the coherence between the two lowest Landau level magnetoexcitons. We interpret our observations using a many-body theory and find that the inter-Landau level coherence decays with a time constant, substantially longer than the corresponding interband magnetoexciton dephasing times. Our results indicate an intraband excitation dynamics that cannot be described in terms of uncorrelated interband excitations.

Far field millimeter-wave imaging via optical upconversion

Abstract: Millimeter-wave imaging has the unique potential to penetrate through poor weather and atmospheric conditions and create a high-resolution image. In pursuit of this goal, we have implemented a far-field imaging system that is based on optical upconversion techniques. Our imaging system is passive, in which all native blackbody radiation that is emitted from the object being scanned is detected by a Cassegrain antenna on a rotating gimbal mount. The signal received by the Cassegrain is passed to an optical modulator which transfers the radiation onto sidebands of a near-infrared optical carrier frequency. The signal is then passed to a low-frequency photodetector that converts remaining sideband energy to a photocurrent. Even though optical upconversion can produce loss, our system demonstrates low noise equivalent powers (NEP) due to the low-noise of the photodetection process. Herein, we present our experimental results and images obtained by using the far-field scanning system, which was assembled with commercially available components. In addition, we detail efforts to increase the resolution of the image and to compact the imaging system as a whole.

Optical detection device, and image display device

Abstract: Provided is a photodetection device which is small in size and has excellent sensitivity. A photodetection device puts cathode terminals of photodiodes having different spectral characteristics into an open end state, and detects light intensity of a desired wavelength region according to a difference in electric charges that have been stored in those photodiodes in a given period of time. The photodiodes employ a system of storing electric charges, and hence even if a photocurrent is small, the photocurrent may be stored to obtain the electric charges required for detection, and the downsizing and high detection performance of a semiconductor device that forms the photodiodes may be achieved. Further, a wide dynamic range may be realized with an electric charge storage time being variable according to the light intensity, to intermittently drive an element required for difference detection at the time of difference detection so as to suppress electric power consumption, or to average the output so as to reduce flicker.