Showing papers on "Photodiode published in 1995"

System for reading two-dimensional images using ambient and/or projected light

Abstract: A system for reading a two-dimensional image, and for comparing the two-dimensional image to stored data representative of a known image. The optical scanning device comprises a sensor for capturing the two-dimensional image, which sensor includes a light source for projecting an emitted light towards the two-dimensional image and an optical assembly for focussing light, which may be ambient and or emitted light from the light source, reflected from the framed two-dimensional image onto a CMOS or CCD detector for detecting the focussed light, the detector including a photodiode array for sensing the focussed light and generating a signal therefrom. Aiming of the sensor to read the two-dimensional image is facilitated by a frame locator consisting of a laser diode which emits a beam that is modified by optics, including diffractive optics, to divide the beam into beamlets which having a spacing therebetween that expands to match the dimensions of the field of view of the sensor, forming points of light at the target to define the edges of the field of view.

Optical generation of millimeter-wave signals for fiber-radio systems using a dual-mode DFB semiconductor laser

Abstract: This paper presents a new approach to the optical generation of millimeter-wave signals using a dual-mode multisection distributed feedback semiconductor laser. This simple device is capable of generating high power signals between 40 and 60 GHz with extremely high spectral purity and stability. The two optical modes produced by this laser are heterodyned on an ultrafast photodiode to give a beat signal at the mode difference frequency. The phase noise of the beat signal is greatly reduced by phase-locking the modes using an electrical drive signal applied to the laser at a subharmonic of the beat frequency. Millimeter-wave signals are obtained with a linewidth of less than 10 Hz, a phase noise of less than -85 dBc/Hz at 100 kHz offset, and a locking range of about 500 MHz. Millimeter-wave fiber-radio systems are seen as a major application area for these new compact optical sources. >

Thin-film nonlinear optical diode

Abstract: We present results of a theoretical investigation into a nonlinear thin‐film multilayer device that exhibits passive anisotropic optical transmission—the analogue of the electronic diode. This optical diode is a nonlinear, asymmetric, distributed Bragg reflector. Material parameters for a nonlinear polymer (polydiacetylene 9‐BCMU) and rutile are used in alternating layers to model a realistic device. The diode exhibits more than five times as much transmittance in one direction as in the opposite direction. It has a thickness of only 2 μm and is polarization insensitive.

Photodiode Amplifiers: OP AMP Solutions

Abstract: Table of contents Photodiodes.The Basic Amplifier.Bandwidth and Stability.Wideband Photodiode Amplifiers.Noise.Noise Reduction.High-Gain Photodiode Amplifiers.Reducing Power-Supply Noise Coupling.Reducing External Noise Effects.Position-Sensing Photodiode Amplifiers.

Integration of laser with photodiode for feedback control

Abstract: Photodiodes are integrally formed with vertical cavity surface emitting lasers (VCSELs) and superluminescent light emitting diodes (SLEDs) for monitoring optical radiation intensities. In different embodiments, the photodiode is epitaxially formed within a mirror of a VCSEL, non-epitaxially formed on top of a VCSEL, non-epitaxially formed on side of a VCSEL, or formed on the substrate on the side opposite the VCSEL. A lateral injection vertical cavity surface emitting laser is also disclosed for integration with a lateral PIN photodiode. A photodiode having the same epitaxial layers as a VCSEL is also integrally formed alongside of the VCSEL. Similar devices using SLEDs are also disclosed.

New digital detector for projection radiography

Abstract: The operational principle of a new, patented digital radiographic system using a multi-layer structure consisting of a thin-film pixel array, selenium x-ray photoconductor, dielectric layer and top electrode is described. Under an applied electric field, a diagnostic x-ray signal is obtained by the direct conversion of x-ray energy to electron-hole pairs which are collected as electrical charges by individual storage capacitor associated with each pixel element. The electronic readout sequence is initiated immediately after the x-ray exposure, and in several seconds, the image data is available for display on a video monitor, for data storage, data transmission, and hard copy generation. Signal strength of this direct conversion method is estimated to be significantly higher than that of other indirect conversion methods where light is first generated using a scintillator or phosphor and then detected by charge-coupled devices (CCDs) or thin-film-transistor (TFT) arrays in conjunction with photodiodes. In addition, since charges generated by x-ray photons move mostly along the direction of the bias electric field, images of very high spatial resolution can be obtained. The resolution limits are principally defined by the smallest pixel that can be manufactured. Recent x-ray images obtained from experimental detector panels are presented. X-ray sensitivity, dynamic range, signal-to-noise ratio, and spatial resolution are discussed.

A room temperature LSO/PIN photodiode PET detector module that measures depth of interaction

Abstract: We present measurements of a 4 element PET detector module that uses a 2/spl times/2 array of 3 mm square PIN photodiodes to both measure the depth of interaction (DOI) and identify the crystal of interaction. Each photodiode is coupled to one end of a 3/spl times/3/spl times/25 mm LSO crystal, with the opposite ends of all 4 crystals attached to a single PMT that provides a timing signal and initial energy discrimination. Each LSO crystal is coated with a "lossy" reflector, so the ratio of light detected in the photodiode and PMT depends on the position of interaction in the crystal, and is used to determine this position on an event by event basis. This module is operated at +25/spl deg/C with a photodiode amplifier peaking time of 2 /spl mu/s. When excited by a collimated beam of 511 keV photons at the photodiode end of the module (i.e. closest to the patient), the DOI resolution is 4 mm FWHM and the crystal of interaction is identified correctly 95% of the time. When excited at the opposite end of the module, the DOI resolution is 13 mm FWHM and the crystal of interaction is identified correctly 73% of the time. The channel to channel variations in performance are minimal. >

128 x 128 CMOS photodiode-type active pixel sensor with on-chip timing, control, and signal chain electronics

Abstract: A 128 X 128 element CMOS active pixel image sensor (APS) with on-chip timing, control, and signal chain electronics has been designed, fabricated and tested The chip is implemented in 12 micrometers n-well process with a 192 micrometers pixel pitch The sensor uses a photodiode-type CMOS APS pixel with in-pixel source follower, row selection and reset transistors The sensor operates from a +5 V supply and requires only a clock signal to produce video output The chip performs correlated double sampling (CDS) to suppress pixel fixed pattern noise, and double delta sampling (DDS) to suppress column fixed pattern noise The on-chip control circuitry allows asynchronous control of an inter frame delay to adjust pixel integration On-chip control is also provided to select the readout of any size window of interest

Signal generation using pulsed semiconductor lasers for application in millimeter-wave wireless links

Abstract: We investigate the generation of signals using pulsed semiconductor lasers for application in millimeter-wave (mm-wave) wireless links. The generation of mm wave harmonic frequencies in both mode-locked and gain-switched lasers is considered and a method to generate mm-wave modulated optical signals with modulation depths approaching 100% is implemented. The technique uses optical filtering to select only two optical modes in the pulsed laser spectrum that beat together in a highspeed photodiode. The application of this method to the feeding of mm-wave wireless links incorporating microstrip patch antennas is demonstrated. These optically fed links have application in indoor wireless LAN's and optical fiber microcellular systems. >

Integrated high frequency low-noise current-mode optical transimpedance preamplifiers: theory and practice

Abstract: Classical designs of optical transimpedance amplifiers for p-i-n photodiode receiver circuits generally employ common-emitter or common-source input stages. In this paper we explore the design of a new class of low noise "current-mode" optical transimpedance preamplifier based upon common-base input stages. Simulated and measured results of a 10 GHz GaAs HBT and 3.5 GHz BiCMOS common-base input optical transimpedance amplifier are presented. >

Si-OEIC with a built-in PIN-photodiode

Abstract: A Si-OEIC with a built-in PIN-photodiode has been developed by a new device structure. We have successfully fabricated an optical link receiver with a speed of 50 Mb/s. The new device structure consists of stacked epitaxial layers each with a buried diffusion region. The cutoff frequency of the photodiode thus realized is 300 MHz and the fall time is 1.6 ns. In this paper, the structure of this new device is presented along with its fabrication process, while the performance is analyzed using device simulation. It was found that the speed of the PIN-photodiode in the Si-OEIC is dominated by carrier transit time in the n/sup +/-buried region. Further investigation was made by device simulation on two advanced structures. The speed of response of PIN-photodiode will be improved to as fast as 1 ns by the current Si technology. By more advanced technology, 0.7 ns will be achieved for the fall time showing the ultimate characteristic of Si-OEIC. >

Layered solid state photodiode sensor array

Abstract: A photodetecting device and a method for constructing the photodetecting device. The photodetecting device provides at least one transistor formed over a substrate and at least one photodiode formed over the at least one transistor. Each of the at least one photodiode is coupled to one of the at least one transistor. The fill factor of the photodiode is very high even when the resolution of the photodetecting device is increased. The photodetecting devices are formed in a matrix having rows and columns. The matrix of photodetecting devices forms a two dimensional imaging device.

Laser weld quality monitoring system

Abstract: A method is provided for monitoring of the progression and the quality of laser material processing. Sensors and detectors are placed in the vicinity of reaction area to capture the signatures of material processing. The signals include light, temperature, sound, gas, smoke, vapor, particles, etc. emanating from the reaction area. The intensity and the timing of certain signals indicate the stages of the processing and the processing quality. One example of this invention is the use of photodiode sensors to monitor the progression of laser spot welding of a certain electronic component. Three photodiode sensors are used to monitor the laser pulse, the reflected beam, and the transmitted beam. A computer analyzes these signals in real time to determine the progressive stages of the laser welding process and the expected weld quality.

Calibration of optical lever sensitivity for atomic force microscopy

Abstract: Accurate force determinations in atomic force microscopy require the precise measurement of cantilever deflections. A limiting factor in making these measurements is the calibration of the optical lever detection system, particularly when the tip cannot be pressed against a hard surface. Here we show that, for a given instrument, a fixed displacement of the photodiode detector produces a change in the detector voltage that correlates strongly with optical lever sensitivity. This provides a simple method for optical lever sensitivity calibration not requiring contact of the tip with any surface. The data also suggest that differences in the shape of the laser spot on the photodiode are a major source of variability in optical lever sensitivity.

Independently accessed back-to-back HgCdTe photodiodes: a new dual-band infrared detector

Abstract: We report the first data for a new two-color HgCdTe infrared detector for use in large dual-band infrared focal plane arrays (IRFPAs). Referred to as the independently accessed back-to-back photodiode structure, this novel dual-band HgCdTe detector provides independent electrical access to each of two spatially collocated back-to-back HgCdTe photodiodes so that true simultaneous and independent detection of medium wavelength (MW, 3–5 μm) and long wavelength (LW, 8–12 μm) infrared radiation can be accomplished. This new dual-band detector is directly compatible with standard backside-illuminated bump-interconnected hybrid HgCdTe IRFPA technology. It is capable of high fill factor, and allows high quantum efficiency and BLIP sensitivity to be realized in both the MW and LW photodiodes. We report data that demonstrate experimentally the key features of this new dual-band detector. These arrays have a unit cell size of 100 x 100 μm2, and were fabricated from a four-layer p-n-N-P HgCdTe film grown in situ by metalorganic chemical vapor deposition on a CdZnTe substrate. At 80K, the MW detector cutoff wavelength is 4.5 μm and the LW detector cutoff wavelength is 8.0 μm. Spectral crosstalk is less than 3%. Data confirm that the MW and LW photodiodes are electrically and radiometrically independent.

WDM receiver by monolithic integration of an optical preamplifier, waveguide grating router and photodiode array

Abstract: A high performance monolithic WDM receiver is demonstrated. The chip receives eight optical channels spaced by 200 GHz. An optical amplifier at the input of the device boosts the incoming signal. A fibre insertion DC responsivity of 0.5 A/W and crosstalk below -20 dB are achieved. The receiver has a small signal bandwidth of 3.5 GHz.

Micromachined submicrometer photodiode for scanning probe microscopy

Abstract: A submicrometer photodiode probe with a sub‐50 nanometer tip radius has been developed for optical surface characterization on a nanometer scale. The nanoprobe is built to detect subwavelength optical intensity variations in the near field of an illuminated surface. The probe consists of an Al–Si Schottky diode constructed near the end of a micromachined pyramidal silicon tip. The process for batch fabrication of the nanoprobes is described. Electrical and optical characterization measurements of the nanoprobe are presented. The diode has a submicrometer optically sensitive area with a 150 fW sensitivity.

Recent progress in optical oxygen sensor instrumentation

Abstract: Optical methods for the determination of dissolved or gaseous oxygen are mainly based on the principle of fluorescence quenching. Measurement schemes have been reported which employ various oxygen-sensitive dyes and bulky instrumentation. Typically, expensive fluorescence spectrometers or fibre-optic photometers have been used, and the applicability of such instruments is rather limited. A system based on low-cost semiconductor devices (light-emitting diodes (LEDS), photodiodes, low-cost analogue and digital components) and new LED-compatible oxygen-sensitive membranes has been developed at our institute. The instrument is capable of determining dissolved or gaseous oxygen and may be calibrated, for example, by a simple two-point calibration procedure with air-saturated and oxygen-free water. Thermostatization of the flow-through cell results in higher measurement accuracy and in a reduced influence of the ambient temperature on the instrument. The overall performance of the oxygen sensor has been investigated, e.g. measurement stability, effectivity of thermostatization, calibration, oxygen diffusion into the measuring cell and excitation feed-through.

Construction and Evaluation of a Visible Spectrometer Using Digital Micromirror Spatial Light Modulation

Abstract: Digital micromirror devices (DMDs), also known as spatial light modulators, have been produced in a wide variety of configurations specific to their applications such as joint-transform correlator systems, optical neural networks, and high-definition televisions. The characteristics of DMD technology and flexibility of design lend themselves to a new application in optical spectrometers. Medium-resolution optical spectrometers, with a spectral bandwidth on the order of 1 nm, are widely used in instrumentation designed to record molecular absorption spectra in the ultraviolet and visible regions and are among the most widely used laboratory instruments. Modern UV-visible spectrometers usually are designed to use a multichannel detector, such as a photodiode array (PDA), in conjunction with a compact fixed-resolution spectrograph and can record spectra with reasonable speed, ∼ 30 ms. These spectrographs have no moving parts and are used for on-line detection of chromatographic eluents, for routine analytical determinations, and for industrial applications such as measurements made in process streams. However, diode array detectors are generally more expensive and are less sensitive than photomultiplier tubes (PMTs), particularly in the UV, and require cooling when a long integration time and low dark current are necessary. In addition, the diode array cannot acquire spectra fast enough for most kinetic studies to be made. A medium-resolution spectrometer which incorporates DMD technology and a PMT for detection has the potential of obtaining a spectrum on the order of a few milliseconds with high sensitivity at a lower cost than that for current PDA or charged-coupled device (CCD) spectrometers. Another advantage of the DMD spectrometer is that it possesses the capability of repetitively scanning a small portion of the spectrum without collecting the entire spectrum (random pixel access). The high sensitivity of a DMD spectrometer using a PMT also makes it ideal for fluorescence and phosphorescence detection.

8–13 μm InAsSb heterojunction photodiode operating at near room temperature

Abstract: p+‐InSb/π‐InAs1−xSbx/n+‐InSb heterojunction photodiodes operating at near room temperature in the 8–13 μm region of infrared (IR) spectrum are reported. A room‐temperature photovoltaic response of up to 13 μm has been observed at 300 K with an x≊0.85 sample. The voltage responsivity‐area product of 3×10−5 V cm2/W has been obtained at 300 K for the λ=10.6 μm optimized device. This was close to the theoretical limit set by the Auger mechanism, with a detectivity at room temperature of ≊1.5×108 cm Hz1/2/W.

Solid-state image pickup apparatus including a unit cell array

Abstract: A unit cell array is formed of unit cells arranged one-dimensionally or two-dimensionally, each unit cell having a photodiode, and first and second switches with one terminal of each switch connected to the photodiode. The other terminals of the first switches of the unit cells are connected to integrators that detect the integrated value of the charge generated by the incident light into the photodiodes, and the other terminals of the second switches of the unit cells are commonly connected to a signal line. The other end of the signal line is connected to a current detector that detects, as a current value, charge generated by light incident to the unit cell array. This arrangement results in a solid-state image pickup apparatus which is provided with means integrated on-chip with a sensor and operated within the same power supply voltage range as the sensor, and capable of detecting brightness on the sensor.

Characterisation and modelling of artificial light interference in optical wireless communication systems

Abstract: Wireless indoor infrared transmission systems are affected by noise and interference induced by natural and artificial ambient light. While the shot noise induced on the receiver photodiode by steady ambient light has been extensively described and included in system models, the interference produced by artificial light has only been mentioned as a source of degradation and quite simple descriptions have been presented. This paper presents a characterisation (through extensive measurements) of the interference produced by artificial light and proposes a simple model to describe it. These measurements show that artificial light can introduce significant in-band components for systems operating at bit rates up to several Mbit/s. Therefore it is essential to include it as part of the optical wireless indoor channel. The measurements show that fluorescent lamps driven by solid state ballasts produce the wider band interfering signals, and are then expected to be the more important source of degradation in optical wireless systems.

On-chip light sensor

Abstract: A brightness sensing circuit for providing a binary electrical signal for indicating whether incident light exceeds a certain brightness. The circuit's light detector is a photodiode, whose output is amplified by a first current mirror. The circuit has a reference current source, whose output is amplified by a second current mirror. Both currents are delivered to a common node, whose voltage level transitions from low to high when the amplified input current exceeds the amplified reference current. This node is connected to the gate input of a CMOS inverter, which provides a binary output.

Low power camera-on-a-chip using CMOS active pixel sensor technology

Abstract: A second generation image sensor technology has been developed at the NASA Jet Propulsion Laboratory as a result of the continuing need to miniaturize space science imaging instruments. Implemented using standard CMOS, the active pixel sensor (APS) technology permits the integration of the detector array with on-chip timing, control and signal chain electronics, including analog-to-digital conversion. This paper describes the technology for implementing a low power camera-on-a-chip.

Integration of surface emitting laser and photodiode for monitoring power output of surface emitting laser

Abstract: The present invention provides a structure and method for integrating a photodiode and surface emitting laser on a substrate which minimizes both process complexity and exposure of epitaxial layers. In a first embodiment, a photodiode structure is integrated with the surface emitting laser simply by adding a separate Schottky contact to the surface of the SEL. In a second embodiment, a photodiode structure is integrated with the surface emitting laser by positioning a current isolation region between the photodiode and the SEL. The current isolation region should extend into a first mirror region but not into the light generation region of the active region so that the light generation region of the SEL is optically coupled to the light absorption region of the photodiode.

Normal‐incidence strained‐layer superlattice Ge0.5Si0.5/Si photodiodes near 1.3 μm

Abstract: Ge0.5Si0.5 strained‐layer pin photodiodes, in which multiple strained layers serve as the absorption region, have been fabricated. These devices exhibit an optical response at wavelengths beyond 1.3 μm at normal incidence. The measured external quantum efficiencies at an applied bias of 4 V are 17% at 0.85 μm and 1% at 1.3 μm, respectively. Excellent electrical characteristics evidenced by the avalanche breakdown at 20 V have also been demonstrated.

Ultrahigh sensitivity single‐photon detector using a Si avalanche photodiode for the measurement of ultraweak biochemiluminescence

Abstract: A single‐photon detector using a Si avalanche photodiode (APD) has been constructed. A trans‐impedance type front‐end circuit was employed in order to achieve a high signal‐to‐noise ratio. The APD and front‐end circuit were cooled in liquid nitrogen to reduce dark count rate and circuit noise. The system performances were measured, and the achieved dark count rate and total quantum efficiency were 0.08 count/s and 5%, respectively. The sensitivity was evaluated to be of the order of 10−19 W. The APD single‐photon detector was demonstrated to be available for measurement of the ultraweak biochemiluminescence at the order of 10−19 W/mm2 from brain slices, i.e., hippocampal slices. It was shown that the addition of tetrodotoxin to the hippocampal slice caused a decrease in the intensity of biochemiluminescence.

Optical line printhead and an LED chip used therefor

Abstract: A light emitting diode chip includes a substrate carrying thereon a number of light emitting diodes aligned in a row to form an array for producing a number of optical beams parallel to each other in a first direction, and monitoring element provided monolithically on the substrate for detecting the power of the optical beams produced by the light emitting diodes, wherein the monitoring element includes: a reference light emitting diode having a structure identical to the light emitting diodes in the array for producing an optical beam in a second direction perpendicular to the first direction; and a photodiode having a structure identical to the light emitting diodes in the array and separated from the reference light emitting diode by an isolation groove for detecting the optical beam produced by the reference light emitting diode.

Light emitting display device having light receiving element for receiving light from light emitting element and self-holding and optical passage for guiding drive light to the light receiving element

Abstract: There is provided an inexpensive light emitting display device which has a simple wiring structure and produces a bright screen display. A photo-transistor is connected in series with a light emitting diode. The photo-transistor is arranged so that light emitted from the light emitting diode enters into the photo-transistor. There is provided an optical guide for guiding a data signal light to the photo-transistor and an optical guide for guiding a scanning signal light to the phototransistor. Further, an optical control section has a laser diode array, a lens array, and a deflection mirror. The above-mentioned arrangement obviates the need of an electric wiring for a data signal and a scanning signal, and is able to turn on the photo-transistor with the emission light from the light emitting diode and makes the photo-transistor self-hold its conductive state.