Showing papers on "Photodiode published in 1985"

The quantum well self-electrooptic effect device: Optoelectronic bistability and oscillation, and self-linearized modulation

Abstract: We report extended experimental and theoretical results for the quantum well self-electrooptic effect devices. Four modes of operation are demonstrated: 1) optical bistability, 2) electrical bistability, 3) simultaneous optical and electronic self-oscillation, and 4) self-linearized modulation and optical level shifting. All of these can be observed at room-temperature with a CW laser diode as the light source. Bistability can be observed with 18 nW of incident power, or with 30 ns switching time at 1.6 mW with a reciprocal relation between switching power and speed. We also now report bistability with low electrical bias voltages (e.g., 2 V) using a constant current load. Negative resistance self-oscillation is observed with an inductive load; this imposes a self-modulation on the transmitted optical beam. With current bias, self-linearized modulation is obtained, with absorbed optical power linearly proportional to current. This is extended to demonstrate light-by-light modulation and incoherent-to-incoherent conversion using a separate photodiode. The nature of the optoelectronic feedback underlying the operation of the devices is discussed, and the physical mechanisms which give rise to the very low optical switching energy (∼4 fJ/ μm2) are discussed.

Nonequilibrium devices for infra-red detection

Abstract: To increase the operating temperature of long-wavelength infra-red detectors it is proposed that narrow-gap semiconductor devices be operated in a nonequilibrium mode such that the carrier densities are held below their equilibrium, near-intrinsic, levels The possible use of exclusion in photo-conductors and extraction in photodiodes is discussed, and experimental results are shown for the former

Optical imaging applied to microelectronic chip-to-chip interconnections.

Abstract: An imaging system is proposed as an alternative to metallized connections between integrated circuits. Power requirements for metallized interconnects and electrooptic links are compared. A holographic optical element is considered as the imaging device. Several experimental systems have been constructed which have visible LEDs as the transmitters and PIN photodiodes as the receivers. Signals are evaluated at different source–detector separations. Multiple exposure holograms are used as a means of optical fan out allowing one source to simultaneously address several receiver locations. Limitations of this technique are also discussed.

Nonlinear and bistable optical device

Abstract: The invention is a nonlinear or bistable optical device having a low switching energy. The invention uses a means responsive to light for generating a photocurrent, a structure having a semiconductor quantum well region, and means responsive to the photocurrent for electrically controlling an optical absorption of the semiconductor quantum well region. The optical absorption of the semiconductor quantum well region varies in response to variations in the photocurrent. A photodiode or phototransistor may be used as the means responsive to light, and may be made integral with the structure having the semiconductor quantum well region. An array of devices may be fabricated on a single chip for parallel logic processing.

InGaAs PIN photodetectors with modulation response to millimetre wavelengths

Abstract: The transit-time and parasitic limitations on the bandwidth of PIN photodetectors are described and compared with experimental results. Packaged InGaAs photodetectors with measured 3 dB response to 36 GHz (8.3 mm wavelength) have been made.

Wavelength‐selective voltage‐tunable photodetector made from multiple quantum wells

Abstract: We show that a pin‐doped multiple quantum well (MQW) diode can be used as a photodetector whose voltage of maximum photocurrent is wavelength dependent. The voltage of maximum photocurrent can be located accurately and related to the wavelength of the incident light, allowing measurements of the wavelength with a precision of 0.03 A=1.2 GHz. This provides a simple, compact, solid‐state device that can be simultaneously used to measure the intensity and wavelength of an optical beam. Furthermore, the device shows high responsivity, low dark current, and fast response.

Photoelastic measurements by means of computer-assisted spectral-contents analysis

Abstract: A new method of photoelastic measurement has been developed. The light emerging from a polariscope is spectrally separated and projected on a photodiode array. It is shown that the relative retardation can be retrieved from light intensity measured at several wavelengths. Key parameters affecting the precision of this approach are discussed and evaluated.

Improved very-high-speed packaged InGaAs PIN punch-through photodiode

Abstract: We describe the fabrication and characterisation of an improved, coaxially packaged, back-illuminated mesa PIN photodetector utilising an InGaAs absorbing layer on an InP substrate. The measured 3 dB bandwidth is 22 GHz.

Gain of a heterojunction bipolar phototransistor

Abstract: Analytical expressions have been derived for the collector current, optical gain, and quantum efficiency for a heterojunction, bi-polar phototransistor (HPT). These expressions can be utilized to optimize the current gain and quantum efficiency for HPT design. The presence of avalanche multiplication in the base-collector junction has been taken into account and shown to be a significant factor in determining the gain of an InGaAs/InP phototransistor. Experimental results of optical gain versus the collector-emitter voltage can only be explained in terms Of avalanche multiplication.

Optical transmission system

Abstract: In a coherent optical transmission system an input optical signal is amplified by being frequency down converted to an intermediate frequency, for example by means of a photodiode (1) and a reference optical local oscillator signal, and the photodiode output current is amplified in a GaAs FET wideband amplifier (6) and inserted on an optical carrier signal comprised by the reference signal by means, for example, of an integrated optical single sideband modulator (up converter) (7). By use of the same optical local oscillator to drive both the photodiode down converter and the integrated optic single sideband up converter, input/output coherence is ensured. The optical local oscillator may be comprised by a GaAlAs laser (3) stabilized to an "atomic" standard (4,5). Channel dropping/insertion may be carried out at the intermediate frequency, for example following the amplifier (6).

The DSI diode—A fast large-area optoelectronic detector

Abstract: Fast double-Schottky-interdigitated diodes have been fabricated by evaporating Al-Schottky contacts on lowly doped n-GaAs (n=1014cm-3), These detectors have a relatively large light-sensitive area of 400 µm2. Rise and fall times are in the order of 10 ps. The external quantum efficiency is 25 percent at λ = 820 nm. The frequency response of the diodes is essentially flat up to 18 GHz, which is the limit of the measuring equipment.

Photodiode array Fourier transform spectrometer with improved dynamic range.

Abstract: An unconventional Fourier transform spectrometer is described which does not require mechanical scanning. The instrument uses a photodiode array as detector and incorporates features whereby the systematic background noise associated with this type of device may be compensated for to give good quality interferograms. Sample spectra are presented to demonstrate the performance of the instrument.

Carrier diffusion effects in the time-response of a fast photodiode

Abstract: A single-photon avalanche diode (SPAD), in which single carrier events can be measured, is used as a probe for accurate measurements of time-dependent carrier diffusion effects in silicon. Basic criteria are discussed for a Monte Carlo simulation program for computing such diffusion effects in various device geometries. A simple program, suitable also for small minicomputers ( e.g. PDP 11 23 ) has been developed. Its accuracy has been checked by comparison with the experimental data obtained from the available SPAD devices, with pulsed illumination at various wavelengths from laser sources. Results are discussed showing that the simulation program can be reliably employed as a tool for analysis and design of new devices.

Room‐temperature 1.3‐μm optical time domain reflectometer using a photon counting InGaAs/InP avalanche detector

Abstract: We demonstrate the first room‐temperature photon counting optical time domain reflectometer at λ=1.3 μm. A high sensitivity (10−14 W) equal to that of a Ge avalanche diode cooled to 77 K has been realized.

Solid state image sensor

Abstract: A solid state image sensor comprising a plurality of photosensors (8A) including a plurality of avalanche photodiodes (12A) arranged at least in the form of a one-dimensional array and delivering pulse signals each representing the number of photons incident to each of the photosensors; counters (10A) connected to the respective photosensors (8A) to count the pulse signals and hold the count value as a video output; a reset circuit (5) for resetting the counters (10A) to the initial states at a predetermined frequency; and a scanning circuit (14) for sequentially reading out the count value in the counters (10A). The counter (10A) counts the number of photons subjected to photoelectric conversion by the photodiode (12A) so that the video signal is directly derived in the form of a digital signal and thus the video signal with a high S/N ratio is obtained.

Theory of electron and hole impact ionization in quantum well and staircase superlattice avalanche photodiode structures

Abstract: An ensemble many particle Monte Carlo simulation of both electron and hole impact ionization superlattice avalanche photodiodes is presented. The effects of the well depth, width, and applied electric field are analyzed for both the electrons and holes in the quantum well structure. The results are consistent with the current theory of impact ionization first proposed by Shichijo and Hess. It is found that the ratio of the electron to hole impact ionization rates is roughly two orders of magnitude in the staircase APD while α/β is enhanced by one order of magnitude in the quantum well device.

Ultra-low-capacitance flip-chip-bonded GaInAs PIN photodetector for long-wavelength high-data-rate fibre-optic systems

Abstract: A novel GaInAs substrate illuminated photodetector structure is reported for the 1.0–1.7 μm wavelength range with capacitance as low as 0.02 pF, packaging stray capacitance below 0.02 pF, 97% quantum efficiency and subnanoampere leakage current. The device is rugged, epoxy-free, does not use an integral fibre pig-tail and wire bonding to the detector chip is not required.

20 GHz bandwidth InGaAs photodetector for long-wavelength microwave optical links

Abstract: InGaAs photodetectors have been fabricated having a packaged RC plus transit-time-limited bandwidth of 20 GHz and a fibre-coupled responsivity of 0.55 A/W. Using a directly modulated InGaAsP diode laser, the photodetector optical frequency response was measured 3 dB flat to 17 GHz, the bandwidth limit of the laser.

Frequency response of InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption "grading" and multiplication regions

Abstract: We have measured the frequency response of InP/ InGaAsP/InGaAs photodiodes with separate absorption, "grading," and multiplication regions (SAGM-APD's) for a wide range ( 2 \leq M_{0} \leq 35 ) of dc gains. The results are explained in terms of a theoretical model which incorporates the transit time of carriers through the depletion region, the RC time constant, the accumulation of holes at the valence band discontinuity of the heterojunction interfaces, and the gain-bandwidth limit.

A New MOS Phototransistor Operating in a Non-Destructive Readout Mode

Abstract: A new MOS phototransistor with high optical gain and non-destructive readout operation is proposed as a photosensor in an imaging device. The principle of this device is a conduction mechanism whereby an incident light changes the surface potential under the MOS gate and the electron current flowing in a buried channel is modulated by the surface potential. The device has a saturation exposure value of 0.1 lxs, saturation output voltage of 500 mV at VDD=2 V, the dynamic range of 50 dB with no signal processing and non-destructive readout operation.

New high‐speed long‐wavelength Al0.48In0.52As/Ga0.47In0.53As multiquantum well avalanche photodiodes

Abstract: We report the operation of a new long‐wavelength (λ=1.3 μm) superlattice avalanche photodiode. The p+in+ structure, grown by molecular beam epitaxy, consists of a 35 period Al0.48In0.52As (139 A)/Ga0.47In0.53As (139 A) multiquantum well i region sandwiched between p+ and n+‐Al0.48In0.52As transparent layers. dc and high‐frequency multiplications of 32 and 12, respectively, have been measured; the dark current at unity gain is 70 nA. High speed of response with full width at half‐maximum of 220 ps at a gain of 12 and the absence of tails are demonstrated, indicating that carrier trapping in the wells is negligible. In addition, detailed studies of the spectral response for samples with thin layers (103 A) show extremely clearly the effect of the quantum states of the wells on the photocurrent at room temperature.

IMPROVEMENTS IN PHOTODIODE READOUT FOR SMALL CsI(Tl) CRYSTALS

Abstract: Measurements of photon energy resolution in the region around 1 MeV with a small CsI(Tl) photodiode detector will be presented.

Automatic digital wavelength calibration system for a spectrophotometer

Abstract: This invention is directed to a digital wavelength calibration system for a spectrophotometer, which includes a photodiode array that forms an output detector for the spectrophotometer, a light source for generating at least one reference emission line of known peak wavelength, a computer controlled mechanism for causing the peak of said reference line to fall in close proximity to the center of a preselected pixel of said photodiode array, peak location computing apparatus for computing the exact position data of the peak relative to the pixel center in terms of the pixel spacing and the ordinal number of the preselected pixel and for retaining this position data for subsequent wavelength computation, wavelength identification computing apparatus for computing the numerical relationship data of the ordinate number of each pixel to the wavelength falling on that pixel and for retaining this relationship data for subsequent correlation with data generated by the pixel, and apparatus for computational processing and display of the data correlated with the associated wavelength value.

Voltage calibration in e-beam probe using optical flooding.

Abstract: Method and apparatus for calibrating equipment used for testing photodiode arrays by reference to the diode under test. The diodes are illuminated with infrared radiation and different bias voltages, developed by bombardment with an electron beam, are measured at zero current. The measured voltage values are correlated with secondary emission sensor readouts to calibrate the sensor according to the specific diode being tested. Remote light emitting diodes generate the infrared radiation which is coupled to the photodiode array via optical fiber elements.

Performance Characteristics of BGO-Silicon Avalanche Photodiode Detectors for PET

Abstract: Spectroscopic and timing characteristics of a gamma-ray detector based on silicon avalanche photodiodes (APD) and bismuth germanate (BGO) scintillators are reported. The APD used in this work is a large area (25 mm2) device of the "reach through" type having a quantum efficiency of 70% at 480 nm. When coupled to a 5×5×3 mm3 BGO crystal, its spectroscopic performance is found to be superior to that of a PMT coupled to the same crystal, owing largely to its higher quantum efficiency. At room temperature, the APD achieves better energy resolution than any other (unity gain) solid state photodetector currently available; at -15 °C, its spectroscopic performance is comnparable to that of large area p-i-n photodiodes at -150 °C. Preliminary measurements show that the timing performance of the new detector allows it to be used for both energy and coincidence discrimination in positron emission tomography (PET). Results obtained with a realistic BGO crystal shape and size for PET are also presented. Limitations and possible improvements are discussed.

Peak optical power control circuit for laser driver

Abstract: To compensate for variations in a laser's peak power output due to changes in slope efficiency, a feedback loop is provided to monitor light output and effect compensatory changes in the drive current. In the feedback loop, the light output is detected by a photodiode. The output of the photodiode is filtered by a bandpass filter. The mean power of the filtered signal is determined and compared with a reference to control the laser drive. The reference takes account of the relationship between the filtered signal power and the peak power in the frequency spectrum of the pseudo-random input signal. The use of this reduced-bandwidth signal allows a relatively cheap, low bandwidth photodiode to be used with a long-wavelength laser.

The sensitivity of photoconductor receivers for long-wavelength optical communications

Abstract: We calculate the sensitivity of In 0.53 Ga 0.47 As photoconductor receivers for use in moderate to high bit-rate lightwave transmission applications. It is found that the noise of photoconductive receivers is dominated at all bit rates B Gbit/s by Johnson noise in the conductive channel. Nevertheless, the total noise current decreases approximately linearly with photoconductive gain, and therefore the sensitivity of photoconductive receivers can be comparable to high-sensitivity p-i-n photodiode receivers. The sensitivity of practical photoconductive receivers compares most favorably with p-i-n receivers in the bit-rate range of 500-2 Gbit/s. However, receivers employing high-speed In 0.53 Ga 0.47 As/InP avalanche photodiodes are expected to be more sensitive than photoconductive receivers over the entire bit-rate range considered. In this analysis, we consider the effects of slow photoconductor response on receiver sensitivity, and find that the limited gain-bandwidth product of practical photoconductors increases the complexity of the receiver circuit by necessitating equalization, resulting in a decrease in receiver sensitivity and dynamic range.