Showing papers on "Photodetection published in 2010"
IBM1
TL;DR: In this paper, an asymmetric metallization scheme is adopted to break the mirror symmetry of the internal electric-field profile in conventional graphene field effect transistor channels, allowing for efficient photodetection.
Abstract: Although silicon has dominated solid-state electronics for more than four decades, a variety of other materials are used in photonic devices to expand the wavelength range of operation and improve performance. For example, gallium-nitride based materials enable light emission at blue and ultraviolet wavelengths1, and high index contrast silicon-on-insulator facilitates ultradense photonic devices2,3. Here, we report the first use of a photodetector based on graphene4,5, a two-dimensional carbon material, in a 10 Gbit s−1 optical data link. In this interdigitated metal–graphene–metal photodetector, an asymmetric metallization scheme is adopted to break the mirror symmetry of the internal electric-field profile in conventional graphene field-effect transistor channels6,7,8,9, allowing for efficient photodetection. A maximum external photoresponsivity of 6.1 mA W−1 is achieved at a wavelength of 1.55 µm. Owing to the unique band structure of graphene10,11 and extensive developments in graphene electronics12,13 and wafer-scale synthesis13, graphene-based integrated electronic–photonic circuits with an operational wavelength range spanning 300 nm to 6 µm (and possibly beyond) can be expected in the future. A graphene-based photodetector with unprecedented photoresponsivity and the ability to perform error-free detection of 10 Gbit s−1s data streams is demonstrated. The results suggest that graphene-based photonic devices have a bright future in telecommunications and other optical applications.
2,238 citations
TL;DR: Locally modulated photoresponse enables a new range of applications for graphene-based photodetectors including, for example, pixilated infrared imaging with control of response on subwavelength dimensions.
Abstract: We study photodetection in graphene near a local electrostatic gate, which enables active control of the potential landscape and carrier polarity. We find that a strong photoresponse only appears when and where a p-n junction is formed, allowing on-off control of photodetection. Photocurrents generated near p-n junctions do not require biasing and can be realized using submicron gates. Locally modulated photoresponse enables a new range of applications for graphene-based photodetectors including, for example, pixilated infrared imaging with control of response on subwavelength dimensions.
381 citations
TL;DR: A fundamentally different approach in which disorder is used as a resource rather than a nuisance is demonstrated, generating strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides.
Abstract: A major challenge in quantum optics and quantum information technology is to enhance the interaction between single photons and single quantum emitters. This requires highly engineered optical cavities that are inherently sensitive to fabrication imperfections. We have demonstrated a fundamentally different approach in which disorder is used as a resource rather than a nuisance. We generated strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides. The emission rate of a semiconductor quantum dot embedded in the waveguide was enhanced by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices.
316 citations
TL;DR: The resonance fluorescence of this composite system of hybrid molecules composed of an individual quantum dot and a metallic nanoparticle is calculated and opens a good perspective for applications in active metamaterials and ultracompact single-photon devices.
Abstract: We study theoretically the quantum optical properties of hybrid molecules composed of an individual quantum dot and a metallic nanoparticle We calculate the resonance fluorescence of this composite system Its incoherent part, arising from nonlinear quantum processes, is enhanced by more than 2 orders of magnitude as compared to that of the dot alone The coupling between the two systems gives rise to a Fano interference effect which strongly influences the quantum statistical properties of the scattered photons: a small frequency shift of the incident light field may cause changes in the intensity correlation function of the scattered field of orders of magnitude The system opens a good perspective for applications in active metamaterials and ultracompact single-photon devices
301 citations
TL;DR: In this paper, a bridged β-Ga 2 O 3 nanowire-based photodetector was used for solar-blind photodeter detection, which has a high 250-to-280-nm rejection ratio, low photocurrent noise, and fast decay time.
Abstract: An increasing number of applications using ultraviolet radiation have renewed interest in ultraviolet photodetector research. Particularly, solar-blind photodetectors sensitive to only deep UV ( < 280 nm), have attracted growing attention because of their wide applicability. Among recent advances in UV detection, nanowire (NW)-based photodetectors seem promising, however, none of the reported devices possesses the required attributes for practical solar-blind photodetection, namely, an effi cient fabrication process, a high solar light rejection ratio, a low photocurrent noise, and a fast response. Herein, the assembly of β -Ga 2 O 3 NWs into high-performance solar-blind photodetectors by use of an effi cient bridging method is reported. The device is made in a single-step chemical vapor deposition process and has a high 250-to-280-nm rejection ratio ( ∼ 2 × 10 3 ), low photocurrent fl uctuation ( < 3%), and a fast decay time ( < < 20 ms). Further, variations in the synthesis parameters of the NWs induce drastic changes in the photoresponse properties, which suggest a possibility for tuning the performance of the photodetectors. The effi cient fabrication method and high performance of the bridged β -Ga 2 O 3 NW photodetectors make them highly suitable for solar-blind photodetection.
293 citations
TL;DR: A novel and economic way of synchronization method is designed and incorporated into the system, which allows to work at a low frequency of 40kHz and removes the use of highly precise clock.
Abstract: We report an implementation of decoy-state quantum key distribution (QKD) over 200 km optical fiber cable through photon polarization encoding. This is achieved by constructing the whole QKD system operating at 320 MHz repetition rate, and developing high-speed transmitter and receiver modules. A novel and economic way of synchronization method is designed and incorporated into the system, which allows to work at a low frequency of 40kHz and removes the use of highly precise clock. A final key rate of 15 Hz is distributed within the experimental time of 3089 seconds, by using super-conducting single photon detectors. This is longest decoy-state QKD yet demonstrated up to date. It helps to make a significant step towards practical secure communication in long-distance scope.
226 citations
TL;DR: A measurement scheme capable of recording the amplitude and phase of arbitrary shaped optical waveforms with a bandwidth of up to 160 GHz is presented that is compatible with integration on a silicon photonic chip and could aid the study of transient ultrafast phenomena.
Abstract: The development of a real-time optical waveform measurement technique with quantum-limited sensitivity, unlimited record lengths and an instantaneous bandwidth scalable to terahertz frequencies would be beneficial in the investigation of many ultrafast optical phenomena. Currently, full-field (amplitude and phase) optical measurements with a bandwidth greater than 100 GHz require repetitive signals to facilitate equivalent-time sampling methods or are single-shot in nature with limited time records. Here, we demonstrate a bandwidth- and time-record scalable measurement that performs parallel coherent detection on spectral slices of arbitrary optical waveforms in the 1.55 µm telecommunications band. External balanced photodetection and high-speed digitizers record the in-phase and quadrature-phase components of each demodulated spectral slice, and digital signal processing reconstructs the signal waveform. The approach is passive, extendable to other regions of the optical spectrum, and can be implemented as a single silicon photonic integrated circuit. A measurement scheme that is capable of recording the amplitude and phase of arbitrary shaped optical waveforms with a bandwidth of up to 160 GHz is presented. The approach is compatible with integration on a silicon photonic chip and could aid the study of transient ultrafast phenomena.
177 citations
TL;DR: This reported unique 3D branched nanowire structure offers a generic approach for the integration of new functional materials for photodetection and photovoltaic applications.
Abstract: This Communication reports a low-cost solution fabrication of wafer-scale ZnO/Si branched nanowire heterostructures and their high photodetection sensitivity, with an ON/OFF ratio larger than 250 and a peak photoresponsivity of 12.8 mA/W at 900 nm. This reported unique 3D branched nanowire structure offers a generic approach for the integration of new functional materials for photodetection and photovoltaic applications.
119 citations
TL;DR: Normal incident photodetection at mid infrared spectral region is achieved using the intersublevel transitions from strain-free GaAs quantum dot pairs in Al(0.3)Ga( 0.7)As matrix.
Abstract: Normal incident photodetection at mid infrared spectral region is achieved using the intersublevel transitions from strain-free GaAs quantum dot pairs in Al0.3Ga0.7As matrix. The GaAs quantum dot pairs are fabricated by high temperature droplet epitaxy, through which zero strain quantum dot pairs are obtained from lattice matched materials. Photoluminescence, photoluminescence excitation optical spectroscopy, and visible-near-infrared photoconductivity measurement are carried out to study the electronic structure of the photodetector. Due to the intersublevel transitions from GaAs quantum dot pairs, a broadband photoresponse spectrum is observed from 3 to 8 μm with a full width at half-maximum of ∼2.0 μm.
116 citations
TL;DR: In this paper, multiple-graphene-layer structures with lateral p-i-n junctions for terahertz and infrared (IR) photodetection are proposed.
Abstract: We propose to utilize multiple-graphene-layer structures with lateral p-i-n junctions for terahertz and infrared (IR) photodetection and substantiate the operation of photodetectors based on these structures. Using the developed device model, we calculate the detector dc responsivity and detectivity as functions of the number of graphene layers and geometrical parameters and show that the dc responsivity and detectivity can be fairly large, particularly, at the lower end of the terahertz range at room temperatures. Due to relatively high quantum efficiency and low thermogeneration rate, the photodetectors under consideration can substantially surpass other terahertz and IR detectors. Calculations of the detector responsivity as a function of modulation frequency of THz and IR radiation demonstrate that the proposed photodetectors are very fast and can operate at the modulation frequency of several tens of gigahertz.
97 citations
TL;DR: In this paper, the authors measured the third-order temporal and spatial correlation functions of chaotic thermal light in the single-photon counting regime and found that the probability of jointly detecting three randomly radiated photons from a chaotic thermal source by three individual detectors is 6 times greater if the photodetection events fall in the coherence time and coherence area of the radiation field than if they do not.
Abstract: In a near-field three-photon correlation measurement, we observed the third-order temporal and spatial correlation functions of chaotic thermal light in the single-photon counting regime. In the study, we found that the probability of jointly detecting three randomly radiated photons from a chaotic thermal source by three individual detectors is 6 times greater if the photodetection events fall in the coherence time and coherence area of the radiation field than if they do not. From the viewpoint of quantum mechanics, the observed phenomenon is the result of three-photon interference. By making use of this property, we measured the three-photon thermal light lensless ghost image of a double spot and achieved higher visibility compared with the two-photon thermal light ghost image.
TL;DR: The CMOS-APD is based on N+/P-well junction, and its current-voltage characteristics, responsivity, avalanche gain, and photodetection frequency response are measured.
Abstract: We present a silicon avalanche photodetector (APD) fabricated with standard complementary metal-oxide-semiconductor (CMOS) technology without any process modification or special substrates. The CMOS-APD is based on N+/P-well junction, and its current-voltage characteristics, responsivity, avalanche gain, and photodetection frequency response are measured. Gain-bandwidth product over 1 THz is achieved with the CMOS-APD having avalanche gain of 569 and 3-dB photodetection bandwidth of 3.2 GHz.
TL;DR: It is demonstrated that resolution enhancement beyond the Rayleigh diffraction limit is demonstrated using an N-photon detection strategy that is implemented with a single-Photon imager.
Abstract: The Rayleigh diffraction bound sets the minimum separation for two point objects to be distinguishable in a conventional imaging system. We demonstrate sub-Rayleigh resolution by scanning a focused beam--in an arbitrary, object-covering pattern that is unknown to the imager--and using N-photon photodetection implemented with a single-photon avalanche detector array. Experiments show resolution improvement by a factor ∼(N-N(max))(½) beyond the Rayleigh bound, where N(max) is the maximum average detected photon number in the image, in good agreement with theory.
TL;DR: In this article, the design and fabrication of a monolithic integrated evanescent-coupled Ge-On-silicon-on-insulator (SOI) photodetector and CMOS circuits were realized on common SOI platform using an?electronic-first and photonic-last? integration approach.
Abstract: The design and fabrication of a monolithically integrated evanescent-coupled Ge-on-silicon-on-insulator (SOI) photodetector and CMOS circuits were realized on common SOI platform using an ?electronic-first and photonic-last? integration approach. High-performance detector with an integrated Si waveguide was demonstrated on epitaxial Ge-absorbing layer selectively grown on an ultrathin SOI substrate. Performance metrics of photodetector designs featuring vertical and lateral PIN configurations were investigated. When operated at a bias of -1.0 V, a vertical PIN detector achieved a lower I dark of ~ 0.57 ?A as compared to a lateral PIN detector, a value that is below the typical ~ 1 ?A upper limit acceptable for high-speed-receiver design. Very high responsivity of ~ 0.92 A/W was obtained in both detector designs for a wavelength of 1550 nm, which corresponds to a quantum efficiency of ~ 73%. Impulse response measurements showed that the vertical PIN detector gives rise to a smaller full-width at half-maximum of ~ 24.4 ps over a lateral PIN detector, which corresponds to a -3 dB bandwidth of ~ 11.3 GHz. RC time delay is shown to be the dominant factor limiting the speed performance. Eye patterns (pseudorandom binary sequence 27-1) measurement further confirms the achievement of high-speed and low-noise photodetection at a bit rate of 8.5 Gb/s. Excellent transfer and output characteristics have also been achieved by the integrated CMOS inverter circuits in addition to the well-behaved logic functions. The introduction of an additional thermal budget (800°C) arising from the Ge epitaxy growth has no observable detrimental impact on the short-channel control of the CMOS inverter circuit. In addition, we describe the issues associated with monolithic integration and discuss the potential of Ge-detector/Si CMOS receiver for future optical communication applications.
TL;DR: In this paper, the conditional pulse nulling receiver (CPSN) was proposed, which uses photodetection coupled with optimized phase-coherent optical feedback control and a phase sensitive parametric amplifier.
Abstract: We consider the problem of demodulating M-ary optical PPM (pulse-position modulation) waveforms, and propose a structured receiver whose mean probability of symbol error is smaller than all known receivers, and approaches the quantum limit. The receiver uses photodetection coupled with optimized phase-coherent optical feedback control and a phase-sensitive parametric amplifier. We present a general framework of optical receivers known as the conditional pulse nulling receiver, and present new results on ultimate limits and achievable regions of spectral versus photon efficiency tradeoffs for the single-spatial-mode pure-loss optical communication channel.
TL;DR: In this article, phase-conjugate optical coherence tomography (PC-OCT) is used to achieve a quantum optical coherency tomography with a classical source of phase-sensitive cross-correlated beams.
Abstract: We demonstrate phase-conjugate optical coherence tomography (PC-OCT) using a classical source of phase-sensitive cross-correlated beams to achieve measurement improvements shared by quantum OCT (Q-OCT): a factor-of-2 enhancement in axial resolution and even-order dispersion cancellation. Compared with coincidence counting used in Q-OCT, PC-OCT employs standard photodetection that results in much faster data acquisitions. This work belongs to a new class of classical techniques inspired by quantum methods that have advantages once thought to be exclusively quantum mechanical.
01 Jan 2010
TL;DR: The origin of the dephasing of the S-P intersublevel transitions in semiconductor quantum dots is theoretically investigated in this paper, where a good agreement is found between the modelling and temperature dependence of the four wave mixing signal measured in recent experiments.
Abstract: The origin of the dephasing of the S-P intersublevel transitions in semiconductor quantum dots is theoretically investigated. The coherence time of this transition is shown to be lifetime-limited at low temperature, while at higher temperature pure dephasing induced by the coupling to acoustic phonons dominates the coherence decay. Population relaxation is triggered by the combined effects of electron-LO-phonon strong coupling, leading to the polaron formation, and phonon anharmonicity. A good agreement is found between the modelling and temperature dependence of the four wave mixing signal measured in recent experiments.
TL;DR: In this article, a demonstration of the principles of quantum key distribution (QKD) is performed using a single-photon source in a proof of concept test-bed over a distance of 2 km in standard telecommunications optical fiber.
Abstract: A demonstration of the principles of quantum key distribution (QKD) is performed using a single-photon source in a proof of concept test-bed over a distance of 2 km in standard telecommunications optical fiber. The single-photon source was an optically-pumped quantum dot in a microcavity emitting at a wavelength of 895 nm. Characterization of the QKD parameters was performed at a range of different optical excitation powers. An investigation of the effect of varying the optical excitation power of the quantum dot microcavity on the quantum bit error rate and cryptographic key exchange rate of the system are presented.
Patent•
TDK1
TL;DR: In this article, a photodetector used in an optical pickup device is configured such that the distance between the optical aperture and the photidetection unit is maintained constant, and an optical aperture is formed such that an incident light beam passes there through.
Abstract: A photodetector used in, for example, an optical pickup device includes: a photodetection unit including a plurality of photodetection elements and provided on a semiconductor chip; a light transmitting unit formed on the upper surface of the photodetection unit; and a light shielding layer having an optical aperture and disposed on the upper surface of the light transmitting unit, with these components being formed integrally. The light transmitting unit is configured such that the distance between the optical aperture and the photodetection unit is maintained constant, and the optical aperture is formed such that the inner portion of an incident light beam passes therethrough. The positioning of the photodetector and the positioning of the optical aperture such as a pinhole or a slit for adjusting the light beam entering the photodetection elements of the photodetector can be made at the same time.
TL;DR: In this paper, a method employing conjugated polymer thin film blends is shown to provide a simple and convenient way of greatly enhancing the ultraviolet response of silicon photodetectors.
Abstract: A method employing conjugated polymer thin film blends is shown to provide a simple and convenient way of greatly enhancing the ultraviolet response of silicon photodetectors. Hybrid organic semiconductor/silicon photodetectors are demonstrated using fluorene copolymers and give a quantum efficiency of 60% at 200 nm. The quantum efficiency is greater than 34% over the entire 200-620 nm range. These devices show promise for use in high sensitivity, low cost UV-visible photodetection and imaging applications.
TL;DR: A novel photonic structure for arbitrary waveform generation (AWG) based on the electrooptical intensity modulation of a broadband optical signal which is transmitted by a dispersive element and the optoelectrical processing is realized by combining an interferometric structure with balanced photodetection.
Abstract: A novel photonic structure for arbitrary waveform generation (AWG) is proposed based on the electrooptical intensity modulation of a broadband optical signal which is transmitted by a dispersive element and the optoelectrical processing is realized by combining an interferometric structure with balanced photodetection. The generated waveform can be fully reconfigured through the control of the optical source power spectrum and the interferometric structure. The use of balanced photodetection permits to remove the baseband component of the generated signal which is relevant in certain applications. We have theoretically described and experimentally demonstrated the feasibility of the system by means of the generation of different pulse shapes. Specifically, the proposed structure has been applicable to generate Multiband UWB signaling formats regarding to the FCC requirements in order to show the flexibility of the system.
TL;DR: The whole optical processing is performed inside a compact semiconductor device, suggesting the optoelectronic integration template has a potential for the application of UWB photonic generation.
Abstract: We propose and demonstrate, by proof of concept, a novel method of ultra-wide band (UWB) photonic generation using photodetection and cross-absorption modulation (XAM) of multiple quantum wells (MQW) in a single short-terminated electroabsorption modulator (SEAM). As an optical pump pulse excite the MQWs of SEAM waveguide, the probe light pulse with the same polarity can be generated through XAM, simultaneously creating photocurrent pulse propagating along the waveguide. Using the short termination of SEAM accompanied by the delayed microwave line, the photocurrent pulse can be reversed in polarity and re-modulated the waveguide, forming a monocycle UWB optical pulse. An 89ps cycle of monocycle pulse with 114% fractional bandwidth is obtained, where the electrical power spectrum centered at 4GHz of frequency ranges from 0.1GHz to 8GHz for −10dB drops. Meanwhile, the generation processing is also confirmed by observing the same cycle of monocycle electrical pulse from the photodetection of SEAM. The whole optical processing is performed inside a compact semiconductor device, suggesting the optoelectronic integration template has a potential for the application of UWB photonic generation.
TL;DR: In this paper, a concept of long-period-based optical fiber sensors, with broadband light illumination generated just after the sensing structure, is presented, which allows the interrogation in transmission of the sensing head while integrated in a reflective configuration, which means the LPG sensor is seen in transmission by the optical source but in reflection by the measurement system.
Abstract: A concept of long-period-based optical fiber sensors, with broadband light illumination generated just after the sensing structure, is presented in this work. This new approach allows the interrogation in transmission of the sensing head while integrated in a reflective configuration, which means the long-period grating (LPG) sensor is seen in transmission by the optical source but in reflection by the measurement system. Also, it is shown that with this illumination layout the optical power balance is more favorable when compared with the standard configurations, allowing better sensor performances, particularly when the sensing head is located far away from the photodetection and processing unit. This is demonstrated for the case of the LPG structure applied to measure strain and using ratiometric interrogation based on the readout of the optical power reflected by two fiber Bragg gratings spectrally located in each side of the LPG resonance.
TL;DR: In this paper, the authors reported the enhanced photoabsorption and photodetection of close-packed metallic Au nanoparticles (NPs) in the UV-VIS (visible)-NIR (near infrared) region.
Abstract: Photocurrent generation and photodetection are usually based on semiconductor crystals including Si, CdS, and PbS. This work reports the enhanced photoabsorption and photodetection of close-packed metallic Au nanoparticles (NPs) in the UV-VIS (visible)-NIR (near infrared) region. Photoabsorption in the UV-VIS regions is associated with the interband transition and surface plasmon resonance of AuNPs, while the enhanced NIR absorption is due to the collective effect of interacting AuNPs in the close-packed network. Consequently, the AuNPs exhibits photodetection behavior in the wavelength range of 300–1500 nm. It is proposed that the inter-AuNP photoejection and delocalization of electron-hole pairs changes the carrier lifetime and transit dynamics in favor of photocarrier conduction, thus significantly facilitating photocurrent generation in the metallic AuNP close-pack. Moreover, due to the power-law conduction mechanism in AuNP networks, the quantum yield of AuNPs can be tuned from 10−6 to 10−1 photoelec...
TL;DR: In this article, a quantum-mechanical theory of first-order coherence for statistically nonstationary light in the space-frequency domain is presented, where the quantum treatment of coherence theory is generally carried out in the time domain.
Abstract: Classical theories of coherence for statistically stationary, as well as, nonstationary optical fields are frequently discussed both in the space-time and in the space-frequency domains. However, the quantum treatment of coherence theory is generally carried out in the space-time domain. In this paper, we present a quantum-mechanical theory of first-order coherence for statistically nonstationary light in the space-frequency domain.
TL;DR: In this article, the authors proposed a multifunctional setup consisting of high-finesse optical cavities, beam splitters, and phase shifters, which can project arbitrary photonic two-mode input states onto the subspace spanned by the product of Fock states.
Abstract: We propose and analyze a multifunctional setup consisting of high-finesse optical cavities, beam splitters, and phase shifters. The basic scheme projects arbitrary photonic two-mode input states onto the subspace spanned by the product of Fock states $|n\ensuremath{\rangle}|n\ensuremath{\rangle}$ with $n=0,1,2,\dots{}.$ This protocol does not only provide the possibility to conditionally generate highly entangled photon number states as resource for quantum information protocols but also allows one to test and hence purify this type of quantum states in a communication scenario, which is of great practical importance. The scheme is especially attractive as a generalization to many modes allows for distribution and purification of entanglement in networks. In an alternative working mode, the setup allows for quantum nondemolition number resolved photodetection in the optical domain.
TL;DR: In this article, single photon generation and single photon-pair generation with little uncorrelated multiphoton emission and the feasibility of media conversion of the quantum states between photon polarization and electron spin are fundamental functions for quantum information applications.
Abstract: Single-photon as well as polarization-correlated photon pair emission from a single semiconductor quantum dots is demonstrated. Single photon generation and single photon-pair generation with little uncorrelated multiphoton emission and the feasibility of media conversion of the quantum states between photon polarization and electron spin are fundamental functions for quantum information applications. Mutual media conversion for the angular momentum between photon polarization and electron spin is also achieved with high fidelity via positively charged exciton state without external magnetic field. This is a clear indication that the coupling of photon polarizations and electron spins keeps secured during whole processes before photon emission. Possibility of a metal-embedded structure is demonstrated with the observation of drastic enhancement of excitation and/or collection efficiency of luminescence as well as clear antibunching of photons generated from a quantum dot.
Patent•
26 Jan 2010
TL;DR: In this article, the authors proposed a thermal photodetector by which light not absorbed by a light-absorbing film can be efficiently reflected and directed to the light absorbing film to increase the detection sensitivity.
Abstract: PROBLEM TO BE SOLVED: To provide a thermal photodetector by which light not absorbed by a light-absorbing film can be efficiently reflected and directed to the light-absorbing film to increase the detection sensitivity of the thermal photodetector. SOLUTION: Each thermal photodetector 10A to 10D includes: a substrate 20 having the bottom surface of a concave portion 22 forming a light-reflecting curved surface 24; a thermal photodetection element 30 including a light-absorbing film 32; and a support member 40 supporting the thermal photodetection element. The substrate 20 and the support member 40 are thermally separated by a cavity 50. The light-reflecting curved surface 24 and the light-absorbing film 32 overlap with each other in a plan view, and the light-reflecting curved surface 24 has a projection area in a plan view larger than an area of the light-absorbing film 32. The light of incident light not absorbed by the light-absorbing film 32 is reflected by the light-reflecting curved surface 24, and absorbed by the light-absorbing film 32 along a reflected light path in a direction opposite to the incidence direction. Photosensitivity is thereby enhanced. COPYRIGHT: (C)2011,JPO&INPIT
13 Jun 2010
TL;DR: A structured receiver whose mean probability of symbol error is smaller than all known receivers, and approaches the quantum limit is proposed.
Abstract: We consider the problem of demodulating M-ary optical PPM (pulse-position modulation) waveforms, and propose a structured receiver whose mean probability of symbol error is smaller than all known receivers, and approaches the quantum limit. The receiver uses photodetection coupled with optimized phase-coherent optical feedback control and a phase-sensitive parametric amplifier. We present a general framework of optical receivers known as the conditional pulse nulling receiver, and present new results on ultimate limits and achievable regions of spectral versus photon efficiency tradeoffs for the single-spatial-mode pure-loss optical communication channel.
TL;DR: In this article, the effects of realistic photodetection, with nonunit quantum efficiency and background noise (dark counts), on the performances of quantum communication schemes based on photon-number entangled states (PNES).