Sensitive Amplifier Research Articles

Narrowband phase sensitive fiber parametric amplifier

We describe a widely tunable phase sensitive fiber amplifier, based on narrowband parametric amplification in dispersion shifted fiber. Using a fiber with a zero dispersion wavelength of 1549 nm and a pump wavelength in the range of 1549 nm to 1532 nm, we obtained phase sensitive amplification between 1344 nm and 1781 nm, for an overall wavelength range of 437 nm. The amplifier threshold power is 7 W, and the maximum gain is 50 dB at a pump peak power of 25 W. The variance in gain due to phase sensitivity was measured to be up to 15 dB.

Phase sensitive amplification with noise figure below the 3 dB quantum limit using CW pumped PPLN waveguide

The noise figure (NF) of a phase sensitive amplifier (PSA) based on a periodically poled LiNbO3 (PPLN) waveguide was evaluated in the optical and electrical domains. Phase sensitive amplification was realized using degenerate parametric amplification in the PPLN waveguide, which was pumped by the second harmonic frequency of the signal. Second harmonic pumping enables direct observation of the intrinsic amplified spontaneous emission (ASE), which determined the NF of the PSA. An NF below the 3 dB quantum limit was obtained by observing the intrinsic ASE. The low NF was also confirmed via the noise floor measurement of a cascaded PSA and erbium doped fiber amplifier in the electrical domain. The PSA was used as a preamplifier for detecting a 40 Gbit/s phase shift keying signal. The low noise characteristics were confirmed by the improved sensitivity.

Development of high performance Avalanche Photodiodes and dedicated analog systems for HXI/SGD detectors onboard the Astro-H mission

Hard X-ray Imager and Soft Gamma-ray Detector are being developed as onboard instruments for the Astro-H mission, which is scheduled for launch in 2014. In both detectors, BGO scintillators play key roles in achieving high sensitivity in low Earth orbit (LEO), by generating active veto signals to reject cosmic-ray events and gamma-ray backgrounds from radio-activated detector materials. In order to maximize background rejection power, it is also important to minimize the energy threshold of this shield. As a readout sensor of weak scintillation light from a number of BGO crystals in a complicated detector system, high performance, reverse-type Avalanche Photodiodes (APDs), with an effective area of 10×10mm2 are being employed, instead of bulky photomultiplier tubes (PMTs).Another advantage of using APDs is their low power consumption, although the relatively low gain of APDs (compared to conventional PMTs) requires dedicated analog circuits for noise suppression. In this paper, we report on the development and performance of APD detectors specifically designed for the Astro-H mission. In addition to APD performance, various environmental tests, including radiation hardness and qualification thermal cycling, will be described in detail. Moreover, a dedicated charge sensitive amplifier and analog filters are newly developed and tested here to optimize the performance of APDs to activate fast veto signals within a few μs from the BGO trigger. We will also report on overall performance testing of a prototype BGO detector system that mimics the data acquisition system onboard Astro-H.

Investigation on gain characteristics in non-degenerate cascaded phase sensitive parametric amplifiers

We theoretically and experimentally show the impact of the ratio between the signal and idler generated from the PIA part on the gain characteristics in the continuous wave (CW) pump non-degenerate cascaded phase-sensitive fiber optical parametric amplifier (PS-FOPA). The results show that the length of highly nonlinear fiber (HNLF) used for generating the idler can cause the variation of power ratio between the idler and signal, which significantly affects the gain characteristics of the PS-FOPA under the small signal gain condition. To obtain high gain, it is better to choose long HNLF to generate idler. In our experiment, 5.5 dB gain and 18 nm bandwidth (on/off gain>10 dBm) in PS-FOPA can be achieved when 300 m-long HNLF instead of 200 m-long HNLF is used in PIA.

Evolution of the gain extinction ratio in dual-pump phase sensitive amplification

We have experimentally achieved a gain extinction ratio (GER) of 30 dB at 21.75 dBm pump power in a dual-pump phase sensitive amplifier based on highly nonlinear fiber, which is more efficient than what we predict with the conventional three-wave model. We point out that high-order sidebands play a key role. Then we scrutinize the trajectories of the output signal vector in the complex plane with increasing nonlinear phase shift and understand the roll-over behavior of GER versus pump power curve. We found that the phase "flip" of the output signal occurs around the largest GER. Adjusting design parameters, we show how to improve GER.

The PreAmplifier ShAper for the ALICE TPC detector

In this paper the PreAmplifier ShAper (PASA) for the Time Projection Chamber (TPC) of the ALICE experiment at LHC is presented. The ALICE TPC PASA is an ASIC that integrates 16 identical channels, each consisting of Charge Sensitive Amplifiers (CSA) followed by a Pole-Zero network, self-adaptive bias network, two second-order bridged-T filters, two non-inverting level shifters and a start-up circuit. The circuit is optimized for a detector capacitance of 18–25pF. For an input capacitance of 25pF, the PASA features a conversion gain of 12.74mV/fC, a peaking time of 160ns, a FWHM of 190ns, a power consumption of 11.65mW/ch and an equivalent noise charge of 244e+17e/pF. The circuit recovers smoothly to the baseline in about 600ns. An integral non-linearity of 0.19% with an output swing of about 2.1V is also achieved. The total area of the chip is 18mm2 and is implemented in AMS's C35B3C1 0.35μm CMOS technology. Detailed characterization tests were performed on about 48000 PASA circuits before mounting them on the ALICE TPC front-end cards. After more than two years of operation of the ALICE TPC with p–p and Pb–Pb collisions, the PASA has demonstrated to fulfill all requirements.

An alternative pulse height correction method for pole zero cancellation circuitry

CdTe diode radiation detectors have a problem called the “polarization effect”, which causes CdTe performance to degrade with time. The pulsed bias voltage shutdown technique, in which a bias voltage is turned off and on quickly to recombine the accumulated charges, is used to suppress the effect. When this technique is used with a charge sensitive amplifier equipped with a pole zero cancellation (PZC) circuit, an extra dead time is observed. After a 40ms shutdown, we have to wait for 130ms (net 170ms dead time) due to the saturation of the amplifier when equipped with a PZC stage while only 10ms (net 50ms dead time) is necessary without a PZC. However, PZC is essential to reduce the degradation of the energy resolution in high count rate conditions. Therefore, an alternative technique to avoid degrading the energy resolution in high count rate conditions without a PZC circuit was investigated. A present pulse height was corrected by using both the pulse heights and the elapsed times from the previous events. As a result, in a readout circuit having no PZC circuitry, an energy resolution of 4.7% for a 122keV photo peak at a count rate of 20kcps was obtained when using the correction, and a 9.1% one was obtained without the correction. In addition, an energy resolution of 2.7% for a 662keV photo peak at a count rate of 21kcps was obtained when using the correction, and a 5.3% one was obtained without the correction. It is shown that this new correction method has almost the same effect as PZC circuitry.

Field-Trial of an All-Optical PSK Regenerator/Multicaster in a 40 Gbit/s, 38 Channel DWDM Transmission Experiment

The performance of future ultra-long haul communication systems exploiting phase-encoded signals is likely to be compromised by noise generated during signal transmission. One potential way to mitigate such noise is to use Phase Sensitive Amplifiers (PSAs) which have been demonstrated to help remove phase as well as amplitude noise from phase-encoded signals. Recently, we showed that a PSA-based signal regenerator based on degenerate four-wave mixing can be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). The developed regenerator was also able to perform simultaneous wavelength conversion and multicasting, details/analysis of which are presented herein. However, this scheme was tested only with artificial noise generated in the laboratory and with the regenerator placed in front of the receiver, rather than in-line where even greater performance benefits are to be expected. Here, we address both theoretically and experimentally the important issue of how such a regenerator, operating for convenience in a multicasting mode, performs as an in-line device in an installed transmission fiber link. We also investigate the dispersion tolerance of the approach.

Fractional charge packet counting with constant relative resolution

SUMMARYA charge‐to‐digital converter concept suitable for pixel‐level charge sensitive amplifiers is presented. The circuit implements a technique referred here as fractional charge packet counting, which ensures large dynamic range operation using constant integration time. By means of a particular circuit arrangement a constant number of significant bits is provided as output, thus ensuring a constant relative resolution over the entire dynamic range.A circuit implementing the concepts described above has been designed and simulated. Each block of the circuit is described in details and its characterization is presented. The circuit is capable to convert input currents in the range of 100 fA to 100 nA at 2 ksample/s with a constant resolution of 10 bit without the need of gain switching. Copyright © 2010 John Wiley & Sons, Ltd.

Phase sensitive amplifier for PSK signals based on non-degenerate four-wave-mixing in the optical fiber

A phase-sensitive-amplifier (PSA) using only one pump channel based on frequency non-degenerate four-wave-mixing (FWM) process for phase-shift-keying (PSK) signals is proposed and demonstrated. Theoretical analyses are given first. By optimizing power levels of three channels and parameters of the highly nonlinear fiber (HNLF), the PSA is able to restore the signal fidelity (down to a BER of 10−9) as the input signal shows an error-floor with the BER of 10−6. Moreover, the PSA for the multi-level PSK signals could be achieved by adjusting the phase relationship between two input signals.

The TDCpix Readout ASIC: A 75 ps Resolution Timing Front-End for the Gigatrackerof theNA62 Experiment

Abstract NA62 is an experiment under development at the CERN Super Proton Synchrotron, aiming at measuring ultra rare kaon decays. The Gigatracker (GTK) detector shall combine on-beam tracking of individual particles with a time resolution of 150 ps rms. The peak flow of particles crossing the detector modules reaches 1.27 MHz/mm 2 fora total rateof about 0.75 GHz.Ahybrid siliconpixel detectoris beingdevelopedto meet these requirements. The pixel chip for the Gigatracker (TDCpix) is under design. The TDCpix chip will feature 1800 square pixels of 300×300 μm2 arranged in a matrix of 45 rows × 40 columns. Bump-bonded to a silicon pixel sensor it shall perform time stamping of particle hits with a timing accuracybetter than 200 ps rms and a detection efficiencyabove 99%. The chosen architecture provides full separation of the sensitive analog amplifiers of the pixel matrix from the noisy digital circuits of the TDCs and of the readout blocks. Discriminated hit signals from each pixel are transmitted to the end of column region. An array ofTime to Digital Converters (TDC) is implemented at the bottom of the pixel array. The TDCs are based on time tagging the events with the fine time codes generated by Delay Locked Loops (DLL) and have a nominal time bin of ∼100 ps. Time stamps and time-over-threshold are recorded for each discriminated hit and the correction of the discriminator's time-walk is performed off-detector. Data are continuously transmitted on four 2.4 Gb/s serial output links. Adescription of the on-going design of the final TDCpix is given in this paper. Design choices and some technical implementation details are presented. Aprototype ASIC including thekeycomponents of this architecture has been manufactured. The achievement of specification figures such as a time resolution of the processing chain of 75 ps rms as well as charged particle time stampingwitha resolutionbetterthan200psrmswere demonstratedexperimentally.Asummaryoftheseresultsisalso presented in this contribution. The ongoing R&Deffort provided an understanding of some of the processes limiting the timing resolution that can beachievedwithhybridplanarpixels.Some considerationsonthese aspectsare discussedatlast.

A practical phase sensitive amplification scheme for two channel phase regeneration

A "black-box" phase sensitive amplifier is presented achieving simultaneous suppression of deterministic phase distortion on two independent 42.66 Gbit/s DPSK modulated signal wavelengths.

Low noise preamplifier ASIC for the PANDA experiment

For the electromagnetic calorimeter of the PANDA detector a preamplifier ASIC named APFEL (ASIC for Panda Front-end ELectronics) has been developed at GSI. It is optimized for the readout of large area avalanche photodiodes (LAAPDs) with a capacitance of 300 pF and an event rate of 350 kHz. The ASIC has two equivalent analog channels each consisting of a charge sensitive amplifier, a shaper stage and differential output drivers. For operating the ASIC in a wide temperature range programmable voltage references are implemented on chip.

Imaging X-ray detector front-end with high dynamic range: IDeF-X HD

Presented circuit, IDeF-X HD (Imaging Detector Front-end) is a member of the IDeF-X ASICs family for space applications. It has been optimized for a half millimeter pitch CdTe or CdZnTe pixelated detector arranged in 16×16 array. It is aimed to operate in the hard X-ray range from few keV up to 250keV or more. The ASIC has been realized in AMS 0.35μm CMOS process.The IDeF-X HD is a 32 channel analog front-end with self-triggering capability. The architecture of the analog channel includes a chain of charge sensitive amplifier with continuous reset system and non-stationary noise suppressor, adjustable gain stage, pole-zero cancellation stage, adjustable shaping time low pass filter, baseline holder and peak detector with discriminator. The power consumption of the IDeF-X HD is 800μW per channel. With the in-channel variable gain stage the nominal 250keV dynamic range of the ASIC can be extended up to 1MeV anticipating future applications using thick sensors. Measuring the noise performance without a detector at the input with minimized leakage current (programmable) at the input, we achieved ENC of 33 electrons rms at 10.7μs peak time. Measurements with CdTe detector show good energy resolution FWHM of 1.1keV at 60keV and 4.3keV at 662keV with detection threshold below 4keV. In addition, an absolute temperature sensor has been integrated with resolution of 1.5°C.

Functionalized Nanowire-Based Antigen Detection Using Frequency-Based Signals

As part of clinical diagnosis, a clinician is required to detect disease causing antigens, bacteria, or viruses in serum, saliva, or other biological samples. Usually, this requires the sample to be sent to a pathology laboratory for analysis. Silicon nanowires can be made into sensitive molecular sensors. When being functionalized with antibodies, they are capable of detecting femto molar concentrations of antigens in real time. Biological molecules at a pH different from their isoelectric point exhibit a net charge. When an antigen attaches to the antibody on the nanowire, the net charged on the antigen displaces free carriers in the nanowire changing its conductance. To date, detection methods have been based upon directly measuring the change in dc conductance. This is difficult and requires sensitive low-noise amplifiers and high-resolution analog-to-digital converters. This is not ideal for low-cost and highly integrated systems. In this paper, it is demonstrated that nanowires exhibit an ac-transfer function that resembles that of a high-pass filter. To the authors' knowledge, this is the first time this effect has been reported. Furthermore, it is illustrated that as molecules with a higher net charge attach to the nanowire and displace more charge carriers within the nanowire channel, the filter's corner frequency decreases. This property of silicon nanowires is exploited to build a low-cost real-time antigen detection system.

Low-Power Amplifier for Readout Interface of Semiconductor Scintillator

We present the design of a readout system, comprising a charge sensitive amplifier and a pulse shaper, that directly interfaces a semiconductor scintillator. The designed amplifier quantifies optical response of a large-area epitaxial photodiode that registers luminescence produced by a scintillating semiconductor wafer when excited by ionizing radiation. The epitaxial photodiode is characterized by a capacitance of 50 pF and a dark current of 10 pA. The presented optimization procedure for the biasing and sizing the input transistor of the CSA directly relates the region of operation of the input transistor with the constraints on power, area and event rate of the readout system. Experimental results of the amplifier implemented in 0.5 μm CMOS technology, verify gain of 71 mV/fC, with the measured linearity of 1.3%. For the parameters of the photodiode, the measured equivalent noise charge (ENC) is 950 electrons with the measured time constant of the pulse shaper of 90 μs and the power consumption of 210 μW. The measured slope of the ENC dependence on the input capacitance is 18 e-/pF.

Phase synchronization scheme for a practical phase sensitive amplifier of ASK-NRZ signals

We present a phase locking scheme that enables the demonstration of a practical dual pump degenerate phase sensitive amplifier for 10 Gbit/s non-return to zero amplitude shift keying signals. The scheme makes use of cascaded Mach Zehnder modulators for creating the pump frequencies as well as of injection locking for extracting the signal carrier and synchronizing the local lasers. An in depth optimization study has been performed, based on measured error rate performance, and the main degradation factors have been identified.

FPDR90—A Low Noise, Fast Pixel Readout Chip in 90 nm CMOS Technology

We report on the design of a prototype IC called FPDR90 dedicated for readout of hybrid pixel semiconductor detectors used for X-ray imaging applications. The FPDR90 has dimensions of 4 mm × 4 mm and was designed in CMOS 90 nm technology with 9 metal layers. The core of the IC is a matrix of 40 × 32 pixels with 100 μm × 100 μm pixel size. A 50 μm diameter circular passivation opening in each pixel allows connecting FPDR90 to a semiconductor detector using bump bonding technique. Each pixel contains a charge sensitive amplifier (CSA), a main amplifier stage, two discriminators and two 16-bit ripple counters. To minimize the effective threshold spread at the discriminators inputs, one 7-bit and one 6-bit trim DACs are used in each pixel for threshold low and threshold high respectively. The data are read out via a single LVDS output with 200 Mbps rate. Each pixel contains about 1800 transistors and has a nominal power consumption of 42 μW for nominal bias condition. The effective peaking time at the discriminator input is 28 ns and it is mainly determined by the time constants of the CSA. The gain is equal to 32 μV/e- or 64 μV/e- in the low and the high gain mode respectively. In the high gain mode the ENC without the detector is 91 e- rms and rises to 106 e- rms with stud bump-bonded pixel detector. The effective threshold spread at the discriminator input is only 0.76 mV (at one sigma level, with 7-bit trim DACs enabled), which corresponds to 12 e- rms at the input. The maximum count rate per pixel depends on the effective CSA feedback resistance. A dead time in the front-end can be set as low as 117 ns (paralyzable model). The FPDR90 can operate with two energy thresholds in the readout mode separate from exposure. Continuous readout is possible when only one threshold is used.

A comparative study on comb electrodes devices made of MWPECVD diamond films grown on p-doped and intrinsic silicon substrate

Diamond is considered as a very promising material for the development of devices for radiation detection. Unlike other conventional photoconductive detectors diamond-based devices should provide high discrimination between UV and visible radiation. In this work we present the electro-optical properties of devices based on randomly oriented diamond films, synthesized in a microwave plasma enhanced chemical vapor deposition reactor. A comparative study on devices with coplanar interdigitated Cr/Au electrodes (with different interelectrode pitches) made of films grown simultaneously on intrinsic and p-doped silicon (100) substrates has been performed. The chemical–structural, morphological, electrical and optical properties of ROD films have been studied. In particular, the optical response has been measured in air using a Xe flash lamp coupled with an optical quartz fiber and a properly tailored front-end electronics based on a charge sensitive amplifier. Experimental results gave indications on how the device performances are dependent on the two types of employed substrates.

Ultra-low Power CMOS Front-End Readout ASIC for Portable Digital Radiation Detector

An ultra-low power complementary metal-oxide-semiconductor (CMOS) front-end readout ASIC was developed for a portable digital radiation detector. The ASIC having a charge sensitive amplifier and a semi-Gaussian pulse-shaper was produced using the CSMC 0.5 μm DPDM process. The ENC noise of 363 e at 0 pF with a noise slope of 23 e/pF complies with the stringent low noise requirements. The peaking time was 250 ns at a 100 mV/fC conversion gain (detector capacitance is 20 pF). By operating this front-end readout ASIC in the weak inversion region, the ultra-low power dissipation is only 0.1 mW/channel (3.0 V). Simulations and test results suggest that this design gives lower power consumption than the front-end readout ASICs working in the strong inversion and is appropriate for the portable digital radiation detectors.