Showing papers on "Photodiode published in 1987"

Recent Measurements on Scintillator-Photodetector Systems

Abstract: The pulse height distributions from eleven kinds of scintillators coupled with a photomultiplier(PMT) and with a silicon photodiode were measured for gamma-ray energies between 14 keV and 1836 keV and compared. The numbers of photoelectrons from the PMT photocathode and those of electron-hole pairs in the photodiode were obtained. The intrinsic pulse height broadening was clearly demonstrated in NaI(Tl), CsI(Na), CsI(Tl) and CsI(pure) scintillators.

Quantum efficiency stability of silicon photodiodes

Abstract: The stability of the quantum efficiency of inversion layer, phosphorus-diffused (n on p), and boron-diffused (p on n) photodiodes has been investigated. Unsatisfactory silicon-silicon dioxide interfaces, latent recombination centers in the diffused layers, and moisture absorption by the device were identified as possible causes of instability. Diodes were fabricated using processes in which these sources of instability were carefully controlled. The resulting diodes were subjected to various accelerated aging tests, and the external quantum efficiency of the diodes was monitored during the tests. Diodes made by older procedures, in which some important parameters affecting stability were not controlled, were included in the study for comparison. The major result of this work is the demonstration that n on p photodiodes are inherently more stable than p on n types in the ultraviolet and blue spectral regions, but that stable p on n devices can also be produced with sufficient care.

Optical motion sensor

Abstract: An optical motion sensor comprises first and second light emitting diodes that emit complementary pulsed beams of infrared energy within a sensing region. A photodiode sums the energies to produce a proportional sensing signal. An amplifier AC coupled to the photodiode blocks the constant portion of the sensing signal and passes a time varying signal portion produced by motion of an object to a sampling circuit. The sampling circuit samples the sensing signal synchronous with emission of the first pulsed beam and converts the time varying signal to a proportional detection signal. An integrator coupled to the sampling circuit responds to a detection signal by modulating the intensity of the second pulsed beam to null the earlier time varying portion of the sensing signal. The motion sensor can be configured as a presence sensor by changing the time constant of the integrator. A slower time constant changes the rate at which the beam intensity is modulated and thus increases the duration of the detection signal.

Optical surface plasmon sensor device

Abstract: An optical sensor device uses surface plasmon resonance to detect the presence of a specific material. A transparent body (12) is coated with a thin gold film (14) which film may be coated e.g. with an antibody material. The arrangement is illuminated with a divergent light beam and light internally reflected from the gold film is detected by a photodiode array (16). The dielectric conditions adjacent the gold film determine the position of the surface resonance angle, this being indicated by a dark area on the detector array.

Pulse oximeter sensor control system

Abstract: A pulse oximeter is provided including two light emitting diodes. Each LED is energized by a unique modulation signal. Light produced by the LEDs passes through the tissue of a subject and is detected by a photodiode. The photodiode signal is separated by tuned circuits resonant at the two modulation signal frequencies and physiological information signals are recovered from the separated signals by amplitude demodulation. The inventive arrangement provides identification of back-to-back coupled LEDs and narrow band filtering for good noise immunity.

Multigigabit-per-second avalanche photodiode lightwave receivers

Abstract: High-speed avalanche photodiodes and high-sensitivity receivers are vital components for future multigigabit-per-second lightwave transmission systems. We review theoretical and experimental performance of high-speed III-V avalanche photodiodes, and also that of multigigabit-per-second lightwave receivers using FET and bi-polar amplifiers. Particular attention is given to APD gain-bandwidth product, and to its effect on high-speed receiver sensitivity. Comparisons between measured receiver sensitivities and calculated performance are presented for bit rates up to 8 Gbit/s.

GaAs traveling‐wave polarization electro‐optic waveguide modulator with bandwidth in excess of 20 GHz at 1.3 μm

Abstract: We report a 13‐μm GaAs traveling‐wave electro‐optic waveguide modulator with a 3‐dB optical bandwidth in excess of 20 GHz The bandwidth was determined by directly detecting the modulated optical signal with a high‐speed InP/GaInAs photodiode The modulator has a coplanar strip electrode configuration with a double heterojunction Al0032Ga0968As/GaAs/Al0032Ga0968As optical guide grown by low‐pressure organometallic vapor phase epitaxy

Waveguide-integrated pin photodiode on InP

Abstract: An InGaAs PIN photodiode was vertically integrated with an inverted optical rib waveguide in InGaAsP. Guided light was transferred to and absorbed by the photodiode at a rate of 0.07dB/?m. For detectors with sufficient length (>300?m) a responsivity of 0.81 A/W was achieved at 1.3 ?m wave-length.

Quantum noise in heterodyne detection

Abstract: A fully quantum mechanical theory of diode mixers which includes quantization of the external circuit is presented. We find that Tucker's theory for SIS mixer conversion efficiencies is correct, but that his expression for the measurement noise must be augmented by an amount corresponding to half a photon at every frequency to which the mixer responds. Noise in high quality SIS mixers is shown to be accurately described by the conceptually simpler photodiode mixer noise theory. The radiation coupling efficiency term, η, which appears in photodiode theory turns out to be the coupling efficiency between the signal source admittance and the admittance which the SIS presents to the LO. Our theory reduces to Caves' quantum linear amplifier formalism, and therefore predicts measurement noises bounded by the quantum lower limit of hv/k_{B} . Predictions of performance versus frequency for SIS's are made. We predict that NbN SIS's will behave as nearly ideal photodiodes for frequencies as high as 3000 GHz.

Implementation of optical interconnections for VLSI

Abstract: This paper reports on the progress in implementing optical interconnections for VLSI. Four areas are covered: 1) the holographic optical element (HOE), 2) the laser sources, 3) the detectors and associated circuits forming an optically addressed gate, and 4) interconnection experiments in which five gates are actuated from one source. A laser scanner system with a resolution of 12 µm × 20 µm has been utilized to generate the HOE's. Diffraction efficiency of the HOE and diffracted spot size have been measured. Stock lasers have been modified with a high-frequency package for interconnect experiments, and buried heterostructure fabrication techniques have been pursued. Measurements have been made on the fabricated photodetectors to determine dark current, responsivity and response time. The optical gates and the overall chip have been driven successfully with an input light beam, as well as with the optical signal interconnected through the one to five hologram.

Stable, high quantum efficiency, UV-enhanced silicon photodiodes by arsenic diffusion

Abstract: Very high quantum efficiency, UV-enhanced silicon photodiodes have been developed by arsenic diffusion into p -type silicon as an alternative to the inversion layer photodiodes commonly used in precise radiometric and spectroscopic measurements. The fabricated diodes had an unbiased internal quantum efficiency that was 100% from 350 to 550 nm, and that exceeded 100% at shorter wavelengths. A typical responsivity at 200 nm was 0.1 A/W. No degradation in responsivity was detected anywhere in the 200–1100 nm range when these devices were exposed to 20 mW/cm 2 of 254 nm radiation for 60 days. Thus the theoretical maximum value of internal quantum efficiency for a diffused photodiode appears to have been achieved in the UV and short wavelength visible, without compromising the diode's long term stability. This is in marked contrast to older types of diffused photodiodes, which either were “dead” in the UV, or exhibited a spectral response vs flux characteristic that changed considerably with UV exposure.

Radiation protection circuit for protection against gamma ray and neutron radiation

Abstract: A circuit for protecting a protected circuit against radiation has a PIN diode series coupled to a laser, which is optically coupled to a photodiode. The photodiode is coupled to the protected circuit. When radiation occurs, the resistance of the PIN diode increases, which causes the laser to cease emitting light. In turn, the resistance of the photodiode increases, thereby decreasing the current from a power supply through the protected circuit.

Opto-electronic scanning arrangement

Abstract: An opto-electronic arrangement for line-by-line scanning of color originals in reproduction technology by means of photodiodes as the opto-electronic transducers characterized by a light source with a condenser system whose light is projected at a fiber-optical shape converter, whose output cross section forms a linear optical pattern which is focussed further by a cylindrical lens into a band shape onto the original. In one embodiment, a filter wheel is provided between the light source and shape converter and in another embodiment the photodiodes are provided with dichroitic filters for selecting the color of the light received from the original into desired colored patterns. In another modification, the first cylindrical lens focusses the light onto a diffusing element and then a second cylindrical lens is present for focussing the light from the diffusing element directly onto the original. The light from the original is preferably received either by a macrolens and focussed onto the row of photodiodes or is received by a GRIN fiber optical arrangement for directing the light onto the photodiodes.

110 GHz high-efficiency photodiodes fabricated from indium tin oxide/GaAs

Abstract: An indium tin oxide/GaAs photodiode is reported with a –3 dB bandwidth in excess of 110 GHz. This device exhibits an external quantum efficiency of > 25% (~0.2 A/W). The device is mounted enabling direct measurements of bandwidth to be made using external mixers and a high-frequency spectrum analyser.

Electron-beam probing of photodiodes

Abstract: Method and apparatus for testing photodiode arrays using an electron beam. The diodes are charged at successive intervals over the RC time constant curve to develop successively increasing voltages at the ends of succeeding time intervals. Diode voltage and current are measured at the end of each interval and the resulting data are used to develop a current-voltage characteristic for each diode.

Solid state image sensor having variable charge accumulation time period

Abstract: A solid state image sensor in which the charge accumulation period of each picture element can be set at the same point of time. Additionally, the lenngth of the charge period can be set at will, thus providing a video signal picture in which all picture elements bear image information with the same time reference. Sensitivity of the solid state image senosr can be adjusted by setting the length of charge accumulation period. In the solid state image sensor, photodiodes are disposed as picture elements, and video signal is output in accordance with a charge which is light-generated within respective photodiodes. A series circuit of a switch and a capacitance element is connected in parallel with the photodiode. The switch is closed for at least the charge accumulation period during which charge is light-generated within the photodiode, and the video signal is obtained in accordance with level of charging of said capacitance element.

Graded gap inversion layer photodiode array

Abstract: A HgCdTe photodiode array for detecting mid-wavelength infrared radiation has a laminated structure consisting of a substrate, a heavily doped wide bandgap buffer layer, and a more lightly doped narrow bandgap base layer. Two sets of a orthogonally disposed U-shaped grooves are etched completely through the base layer and partially through the buffer layer, thereby forming a plurality of mesa-shaped structures. Overlying the portion of base layer contained within each mesa is a capping layer of opposite conductivity. The junction of the base and capping layer within each mesa forms a photodiode. In contact with each capping layer is a metalization area for connection of the underlying diode to a readout device. In contact with the buffer layer is another metalization layer for making a common electrical connection to the array of photodiodes. Overlying the mesa surfaces is a layer of passivation which contains a fixed positive charge. The charge creates an inversion layer within the surface of the base layer exposed along the mesa walls, thereby enlarging the p-n junction of each photodiode. Radiation impinging on a lower surface of the transparent substrate passes through the substrate and into the buffer layer, which is also transparent. Transmitted through the buffer layer, the radiation is absorbed within that portion of the base layer contained within each mesa, resulting in the generation of diode currents.

Low-noise 8 GHz PIN/FET optical receiver

Abstract: An ultrawide-bandwidth, low-noise optical receiver has been designed for use in both multigigabit direct-detection or coherent heterodyne systems at 1.3 and 1.55 ?m wavelengths. The receiver consists of a low-capacitance InGaAs PIN photodiode connected to a high-impedance three-stage GaAs FET preamplifier. Inductive peaking at the front end is used to reduce the receiver noise at high frequencies. The receiver has an equivalent input RMS noise current of < 12 pA/?Hz from 4 to 7 GHz. The measured 3 dB bandwidth of 8 GHz is the widest receiver bandwidth reported to date.

Solid-state image sensor

Abstract: PURPOSE:To prevent the decrease in sensitivity and the increase in smear, by arranging a flattening film on the irregularity of the surface on a photoelectric conversion part, and providing a light-screening metal film, which specifies the opening of the photoelectric conversion part so that incident light is not bent at the end part of said metal film CONSTITUTION:On an N-type substrate 1, the following parts are formed: a P-well layer 2; an N-type impurity layer 3 for a photodiode; an embedded channel type CCD N-well layer 4; an element isolating P impurity layer 5; an interlayer insulating film 6; a polycrystalline silicon gate electrode 7; a light- screening aluminum electrode 8; and a cover insulating film 9 A flattening film 10, which has approximately the same refractive index as that of the cover insulating film 9 is formed on the surface of an element Then, incident light beams (a) and (b) at the end part of the light-screening aluminum electrode are inputted to the photodiode for photoelectric conversion without bending of their optical paths as shown in the Figure

Photo-sensitive device

Abstract: According to the invention, each photosensitive element consists of the series connection of a capacitor (G), a photodiode (D) and an electronic switch (I). The light signal to be read is applied to the device after the photodiodes have been reverse biased by a voltage pulse of amplitude V P1 . The device is read, line by line, by applying a voltage pulse of amplitude V P2 greater than V P1 to each line read. The switches I of the line read are closed while the switches of the other lines are open. Once the device has been read, the photodiodes are reset.

Alignment of optical components

Abstract: In the assembly of a device package, an optoelectronic device (10), such as a light emitting diode (LED) or a photodiode, mounted on a header (14) is aligned with a lens (12), such as a spherical lens, mounted in a housing (2) by making a light beam (23) from a microscope (24) incident on the lens so that light reflected (25) from the lens creates a symmetrical reference image (42, 42', 42"). Light (27) emitted by the device (LED) or reflected from the device (photodiode) forms an object image (44) of the active area of the device. The two images are detected by a camera (28) and are compared (real-image observation by an operator or electronic image comparison by a computer). The device on an x-y table (16) is moved until the object image is centered with respect to the reference image. Then the position of the device within the package is fixed by epoxying, or otherwise securing, the header to the housing (FIG. 1).

Application of a photodiode array detector to multi-component determination by flow injection analysis

Abstract: The capabilities of a photodiode array detector in flow injection analysis for multi-component determination with normal and derivative spectra is outlined. Mixtures of two, three and four components with completely overlapping spectra have been accurately resolved. The effect of wavelength range and mode of spectral selection has also been studied. The proposed analytical method has been successfully applied to the determination of the four active components of a commercial pharmaceutical formulation.

InP/InGaAsP/InGaAs avalanche photodiodes with 70 GHz gain‐bandwidth product

Abstract: A wide bandwidth (8 GHz) and a high gain‐bandwidth product (70 GHz) have been achieved with InP/InGaAsP/InGaAs avalanche photodiodes (APD’s) grown by chemical beam epitaxy. These APD’s also exhibit low dark current ( 90% at λ=1.3 μm), and high avalanche gain (M0≂40).

A low dark current InGaAs/InP p-i-n photodiode with covered mesa structure

Abstract: A new InGaAs p-i-n photodiode with a covered mesa (CM) structure having extremely low dark current characteristics and high yields has been developed. The device consists of only two epitaxial layers: n--InP and n--InGaAs, continuously grown on an n+-InP substrate by liquid-phase epitaxy. The InGaAs layer is chemically etched to be a tapered shape in order to make the fabrication process simple, as compared with a conventional mesa diode. The Zn diffusion to form a p-n junction is carried out without a diffusion mask such as Si 3 N 4 or SiO 2 , which induces damage due to the thermal stress. The tapered-shape InGaAs layer is covered with the Zn-diffused layer because a surface p-n junction occurring in an InGaAs region is leaky. Therefore, the surface p-n junction of the photodiode appears in the n--InP layer, which has a bandgap about two times wider than the InGaAs. Finally, the passivation of the surface p-n junction is carried out with a Si 3 N 4 film formed by a plasma-assisted chemical vapor deposition. We have successfully achieved an extremely low dark current of 20 pA at a reverse bias voltage of 10 V and a high yield of 80 percent, by adopting the CM structure and the simple fabrication process.

Highly stable silicon pin photodiode

Abstract: Silicon photodiodies have several interesting advantages as scintillation detectors. Recently the manufacturing techniques for making photodiodes have been greatly improved. Furthermore the selection of optimum operating parameters for the use of photodiodes and their stability are very important. This paper discusses the recently improved characteristics of Hamamatsu Photonics KK photodiodes.

PIN photodiode formed from an amorphous semiconductor

Abstract: The invention provides a PIN photodiode in which at least one of the P, I, N layers is formed by a composition multi-layer including undoped superimposed layers of amorphous semiconductor and undoped insulator. In one embodiment, the P and N layers are formed by an amorphous multi-layer, with five periods for the P layer and nine periods for the N layer, and the I layer is formed from an amorphous semiconductor.

An APD/FET optical receiver operating at 8 Gbit/s

Abstract: A high-sensitivity optical receiver has been designed for a bit rate of 8 Gbit/s and wavelengths of 1.3-1.55\mu m. The receiver uses a 60-GHz gain-bandwidth-product InGaAs/InGaAsP/InP avalanche photodiode followed by a high-impedance hybrid GaAs MESFET preamplifier. A bandwidth of 6.9 GHz was measured, with flat frequency response ±2 dB being obtained through the use of a 3-tap transversal equalizer. A sensitivity \bar{P} as high as -25.8 dBm was measured for 10-9bit-error rate.

Tri-state optical device with quantum well absorption

Abstract: A tri-state optical device 400 is disclosed having photodiodes 401 and 402 with respective quantum-wells 403 and 404 in the intrinsic regions. The photodiodes are connected in series with a bipolar switch 406 and a source of electrical potential 405 for emitting a pair of optical output beams having various combinations of power levels depending on the state of the bipolar switch and the ratio of two optical control beams incident on the photodiodes. In one state of the tri-state device with the bipolar switch in a conducting state, the two output beams have complementary high and low power levels representing, for example, high and low logic levels "1" and "0". In a second state, the power levels of the two output beams are reversed, thus exhibiting complementary and symmetric output power levels. In the third state when the bipolar switch of the tri-state device in a nonconducting state, the output beams both exhibit a low power level, and the tri-state device is nonresponsive to the power levels of the optical control beams.

Liquid crystal light valve utilizing hydrogenated amorphous silicon photodiode

Abstract: A liquid crystal light valve is provided which comprises a pair of glass cover plates. Transparent electrodes are located on the interfaces of each cover plate. The electrodes are electrically connected to alternating current sources. Insulating films are placed on either side of a liquid crystal material to provide electrical and chemical isolation between the liquid crystal and the electrodes. Spacers are employed to maintain a suitable gap between the insulating films and to prevent the liquid crystal from escaping. Positioned on the side of the liquid crystal from which writing light enters the light valve are, respectively, a dielectric mirror, a light blocking layer and a photoactive layer. According to the present invention, the photoactive layer comprises hydrogenated amorphous silicon which is configured as a photodiode with a junction layer facing the writing light.