Kenneth A. Costello

Photon counting III-V hybrid photomultipliers using transmission mode photocathodes

This paper reports on the development of solid-state hybrid photomultiplier tubes using high quantum efficiency, transmission mode, III-V photocathodes. The first strike low-noise gain mechanism in these devices is provided via electron bombardment of a solid-state GaAs Schottky diode. In addition, a second-stage gain is provided by solid-state avalanching within a GaAs Schottky APD (SAPD) anode. A combined gain of 2/spl times/10/sup 4/, adequate for photon counting, is achieved. Device bandwidth, exceeding 1 GHz, is optimized by tailoring the diode anode structure. The combined traits of this device provide high quantum efficiency, large dynamic range, large bandwidth, and adequate gain for photon counting. Photon counting beyond 1 /spl mu/m is feasible for a cooled device. The tube structure, diode anode structure, noise issues and preliminary photon counting results are discussed.

Photon counting 1060-nm hybrid photomultiplier with high quantum efficiency

An ultra-low-noise, high-speed, hybrid photomultiplier tube sensitive from 900 to 1300 nm optical wavelength is described. The device, also known as an intensified photodiode (IPD), uses an active transferred electron (TE) photocathode with the quaternary In/sub .69/Ca/sub .31/As/sub .67/P/sub .33/ photo-absorbing layer and a GaAs Schottky avalanche photodiode (SAPD) anode. The detector has a combined electron bombarded and avalanche gain of over 15000 which is sufficient to overcome preamplifier noise and provide high internal counting efficiency of approximately 85%. At an active cathode bias of 1.5 V the room temperature cathode dark count rate is 6.67/spl times/10/sup 5//s. Cooling reduces this substantially corresponding to a dark current activation energy almost equal to the bandgap of the In/sub .69/Ca/sub .31/As/sub .67/P/sub .33/ layer.

Transferred electron photocathode with greater than 5% quantum efficiency beyond 1 micron

This paper details the status of a program at Varian EOSP to develop high-sensitivity transmission photocathodes which function in the 0.95 - 1.65 micron wavelength range. One goal of the program is to develop a streak tube compatible cathode with greater than 1% quantum efficiency at 1.3 micrometers . Sealed tube results are presented. Measured performance characteristics include: cathode spectral response, room temperature cathode photoresponse stability, dark current, emitted electron energy distributions, photodiode resolution/MTF, and preliminary time response data. Finally, the paper includes a brief review of transferred electron photocathode physics and potential applications.

Transferred electron photocathode with greater than 20% quantum efficiency beyond 1 micron

This paper details the status of a program at Intevac ATD to develop high sensitivity transmission photocathodes which function in the 0.95-1.7 micron wavelength range. The goal of the program is to develop this technology for use with both imaging and nonimaging detectors. Sealed tube results are presented. Measured performance characteristics include: cathode spectral response, dark current, linearity, and the effects of cooling. A brief discussion of planned development, potential applications, and simple modeling illustrating the advantages of the proposed detectors are included.

Negative electron affinity photocathodes as high-performance electron sources-Part 2: Energy spectrum measurements

The energy spectra of electrons emitted from transmission-mode negative electron affinity photocathodes have been measured at high resolution using a parllel-plate retarding technique. The spectra from GaAs photocathodes have a basic structure that varies with temperature, activation layer qualitites, cathode thickness, and illuminating wavelength. A FWHM energy spread of approximately 50meV at room temperature has been achieved. Spectra from a GaAsP cathode show a markedly different structure and a much wider energy spread.

Photocathode development for a 1300-nm streak tube

This paper reports on the status of a program to develop a streak tube compatible photocathode optimized for 1300-nm operation. Performance characteristics will be presented for a Transferred Electron photocathode with greater than 1% quantum efficiency at 1300-nm. Photocathode performance results will also be presented over the 950 - 1700 nm spectral range.

Gallium Arsenide Electron Bombarded CCD Technology

Electron Bombarded Charge Coupled Devices (EBCCD) which utilize a high performance Gallium Arsenide (GaAs) photocathode have been fabricated and characterized for performance and tube operating life. The EBCCD utilized an 11 mm diagonal, backside illuminated, frame transfer CCD compatible with RS170 video output. The CCD incorporated lateral anti-blooming structures optimized for backside operation. The EBCCD tube was proximity focused and operated with high gain (greater than 150) at low electron landing voltages (less than 2 kV). The EBCCD was integrated in a gated camera system with fast rise and fall times (less than 50 ns). Predicted operating life in a gated camera system as determined by accelerated tests is in excess of 12,000 hours, limited by photocathode degradation.

Comparison of 16-channel laser photoreceivers for topographic mapping

Topographic mapping lidar instruments must be able to detect extremely weak laser return signals from high altitudes including orbital distance. The signals have a wide dynamic range caused by the variability in atmospheric transmission and surface reflectance under a fast moving spacecraft. Ideally, lidar detectors should be able to detect laser signal return pulses at the single photon level and produce linear output for multiple photon events. Silicon avalanche photodiode (APD) detectors have been used in most space lidar receivers to date. Their sensitivity is typically hundreds of photons per pulse, and is limited by the quantum efficiency, APD gain noise, dark current, and preamplifier noise. NASA is pursuing three approaches for a 16-channel laser photoreceiver for use on the next generation direct-detection airborne and spaceborne lidars. We present our measurement results and a comparison of their performance.

Electron Bombarded Semiconductor Image Sensors

The low noise electron bombarded semiconductor gain process is now enabling new classes of single photon sensitive, photocathode based, image sensors. These imagers form two broad classes of devices: low pixel count imagers for high temporal bandwidth photon counting applications and high pixel count imagers for single photon sensitive staring applications. The first class of devices has demonstrated imaging photon counting imagers operating at bandwidths on the order of 1 GHz and able to distinguish multiple photon events. In the case of the second class of devices, single photon sensitivity in a megapixel format is obtained by integrating modern CMOS image sensors with a photocathode in an electron bombarded configuration. An overview of both classes of devices is presented in this chapter and is shown to approach the characteristics desired in a perfect detector having 100% quantum efficiency, infinite gain and bandwidth, and no excess gain noise.

Multichannel intensified photodiode for near infrared single photon detection

An overview of the Intensified Photodiode (IPD) is presented with an emphasis on IPDs optimized for use in the 950nm to 1350nm spectral range for single photon detection applications. The theory of operation of the IPD, two different electron optics designs, and device performance for a multichannel, 4x4 pixel array, low jitter IPD optimized for operation at 1060nm are presented in this paper. Key results include greater than 15% quantum efficiency, large active area, and less than 550ps impulse response.