Focusing on graphene’s high thermal conductivity and high emissivity, we developed a mid-IR light source using a suspended graphene structure as the light emitter. Compared to conventional mid-IR light emitters, this new source has approximately 1000x faster response time and 95% lower power consumption. In addition, it features high brightness and an emission spectrum similar to that of a black body. We used multilayer graphene deposited on Ni foil and transferred it onto a micro-trench etched into a Si/SiO2 wafer to create the suspended structure. The thermal insulation provided by this design allowed for heating of the free standing segment to temperatures over 1000 deg. C through electrical currents. Packaging the light emitter into a vacuum-sealed TO-5 metal can further improved the insulation and ensures a long lifetime for the graphene light emitter. These characteristics make the light source ideal for many analytical applications.
We have developed a new Hybrid Photo-Detector (HPD) with relatively large effective area, fast time response, high
timing resolution, high quantum efficiency and extremely low probability of afterpulse. A GaAsP (Gallium Arsenide
Phosphide) photocathode type has high quantum efficiency approximately 45% around the wavelength of 500 nm, and
the size of the effective area is 3 mm in diameter. The pulse height for single photon is approximately +2 mV with 50
ohm load impedance, and it can be easily observed with a fast response oscilloscope. The rise and fall times for impulse
light are approximately 0.4 ns. The timing resolution for single photon for the GaAsP photocathode type was estimated
to be approximately 80 ps.
We report benchmark tests of a new single-photon counting detector based on a GaAsP photocathode and an electron-bombarded
avalanche photodiode developed by Hamamatsu Photonics. We compare its performance with those of
standard Geiger-mode avalanche photodiodes. We show its advantages for FCS due to the absence of after-pulsing and
for fluorescence lifetime measurements due to its excellent time resolution. Its large sensitive area also greatly simplifies
setup alignment. Its spectral sensitivity being similar to that of recently introduced CMOS SPADs, this new detector
could become a valuable tool for single-molecule fluorescence measurements, as well as for many other applications.
A highly sensitive image sensor for single photon imaging has been developed. The sensor (referred as an intensified EBCCD here) contains a photocathode, a microchannel plate (MCP) and an electron-sensitive CCD in a vacuum tube. In response to incident photons, electrons emitted from the photocathode are multiplied once by the MCP, further by the CCD and read out. Either an image intensifier containing MCPs or an EBCCD containing an electron-sensitive CCD has sensitivity for single photon by itself, however, many intense white spot-noise appear on output image and degrade the image quality seriously at such high-gain operation. In the case of intensified EBCCD reported here, since both the MCP and the electron-sensitive CCD are used for electron multiplication, high gain for single photon detection is available in total at low gains of both devices. This operation reduces the noise drastically, and improves the image quality. We have developed the intensified EBCCD with a GaAsP photocathode for high quantum efficiency, and evaluated the performance. Comparing with conventional cameras, such as an EM-CCD and an image intensifier, the intensified EBCCD shows superior detection capability at especially low-light level, that is single photon imaging.
Electron Bombardment CCD sensor (EB-CCD) had originally developed for the low light imaging application and recently it has been coming to be used as an alternative to SIT tube camera and I-CCD camera. However, some of applications required higher sensitivity and higher dynamic range. In order to meet these expectations, we have been continuing the improvement of sensor such as higher gain and higher quantum efficiency. In this paper, we would like to introduce the new high gain sensor and new photo-cathode of GaAs and GaAsP, which realize the 30 to 50% quantum efficiency. And also we would like to show that how GaAs EB- CCD is sensitive based on the sensitivity comparison test between multi alkali photo-cathode image intensifier and new GaAs photo-cathode EB-CCD sensor.
We have developed the two kinds of Electron Bombardment CCD Camera employing a full frame transfer type and a frame transfer type electron bombardment sensor made by Hamamatsu Photonics. Especially in order to make a camera practicable for various application, we improve the image resolution and tried to measure the life of frame transfer type sensor. With regard to the resolution, there are many factors which degrades the resolution. This time, we reduced the gap length between a photo-cathode and a CCD to 60 percent of original one, hence, the sensor had greater resolution than 450 TV. Furthermore life of sensor is getting longer, because of the MPP CCD structure. C7162-20 Frame transfer Electron Bombardment CCD camera performs as a standard TV rate camera. From the point of camera performance, it can be replaced the SIT tube camera and I-CCD camera. In order to prove this fact, camera was compared with GEN 4 I-CCD camera which uses a small aperture MCP and a Blue-GaAs photo- cathode coupled to the CCD through optical fiber, and we show the result of comparison.
Life characteristics of an EB-CCD incorporating a full frame transfer CCD have been evaluated. Applying -8kV to the photocathode, the accelerated life test corresponding to 3,500 hours of operation was carried out. As the result, there are no degradation of the photocathode sensitivity and the gain. However, an offset is increased linearly proportional to the operation period, including the upper and lower of the irradiated area. The increment after the life test is approximately 700 at 20 degree centigrade with a multi-pinned phase (MPP) operation. From the comparison between the MP and the non-MPP operation of the CCD, the original of the offset is concluded to be the increased dark current (DC) from the Si-SiO2 interface, which is damaged by the Bremsstrahlung x-ray. The DC slightly affects the signal as the offset when positive voltage to gate electrodes depletes the Si-SiO2 interface during the vertical transfer. The DC does not affect the signal at all with the MPP operation in the exposure time. The lifetime of the EB-CCD is calculated to be much longer than 10,000 hours, if the lifetime is defined by the period that the DC fulfills the half of the full well capacity.
For low light level imaging application, a proximity focused electron bombardment CCD (EB-CCD) tube has been developed. In the tube, electrons emitted from the multi-alkali (S-20) photocathode in response to incident light are accelerated by the electric field and bombarded the specially processed CCD which is sensitive to electrons. The electron bombardment gain is 600 at applied voltage of -8kV to the photocathode. Single photon counting operation is possible, because the gain is larger than the readout noise and the dark noise of the CCD. The spatial resolution is better than 360 TV lines, which is the theoretical limit of the full frame transfer CCD (FFT-CCD) of 512 by 512 pixels. No major degradation of either the photocathode sensitivity or the incorporated CCD was observed during the operation for a few tens hours. The life of the EB-CCD tube is being under evaluation. Keywords: Electron tube, Photocathode, Image intensifier, Electron-bombardment, CCD, Low light level imaging
A new magnetic focusing streak tube with a traveling wave deflection electrode has been developed. In the operation, a pulse voltage is applied between the photocathode and the accelerating mesh electrode. The limiting time resolution of approximately 180 fs has been experimentally obtained.
In order to produce a streak tube operated easily, we have developed a new streak tube having ultra-high deflection sensitivity based on a new design concept. Both the low photocathode voltage of -2 kV referred to the anode and the long deflection plate of 63 mm made it possible to achieve the deflection sensitivity of 670 mm/kV. Furthermore, the temporal resolution of 2 ps was achieved by applying a high electric field of 2 kV/mm between the photocathode and the acceleration mesh electrode.
A new femtosecond streak tube is proposed aiming at good time resolution. Based on the
idea, the tube has been designed and computer simulations on the electron trajectory, which
includes dynamic operation of the sweeping electrode, have shown that the tube has
theoretically time resolution of 5Ofs.
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