A Master-Oscillator-Power-Amplifier 2-micron Laser Using Fiber Phase-conjugate Mirror

NASA Technical Reports Server (NTRS)

Yu, Jirong; Bai, Yingxin; Shkunov, V.; Rockwell, D.; Betin, A.; Wang, J.; Petros, M.; Petzar, Paul; Trieu, Bo

2007-01-01

For the first time, a 2-micron master-oscillator-power-amplifier laser using a fiber based phase conjugation mirror has been demonstrated. The beam quality improvement and 56% of the PCM reflectivity have been achieved.

Improved Beam Jitter Control Methods for High Energy Laser Systems

DTIC Science & Technology

2009-12-01

Figure 16. The inner loop is a rate control loop composed of a gimbal, power amplifier , controller, and servo components (gyro, motor, and encoder...system characterization experiments 1. WFOV Control Loop a. Resonance Frequency Random signals were applied to the power amplifier and output...Loop Stabilization By applying a disturbance to the input of the power amplifier and measuring torque error, one is able to determine the torque

Log amplifier with pole-zero compensation

DOEpatents

Brookshier, W.

1985-02-08

A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifer circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedstock loop. The compensated output signal is provided by the second operational amplifier with the log elements, i.e., resistors, and the compensating capacitors in each of the feedback loops having equal values so that each break point is offset by a compensating break point or zero.

Strain gauge ambiguity sensor for segmented mirror active optical system

NASA Technical Reports Server (NTRS)

Wyman, C. L.; Howe, T. L. (Inventor)

1974-01-01

A system is described to measure alignment between interfacing edges of mirror segments positioned to form a segmented mirror surface. It serves as a gauge having a bending beam with four piezoresistive elements coupled across the interfaces of the edges of adjacent mirror segments. The bending beam has a first position corresponding to alignment of the edges of adjacent mirror segments, and it is bendable from the first position in a direction and to a degree dependent upon the relative misalignment between the edges of adjacent mirror segments to correspondingly vary the resistance of the strain guage. A source of power and an amplifier are connected in circuit with the strain gauge whereby the output of the amplifier varies according to the misalignment of the edges of adjacent mirror segments.

High temperature current mirror amplifier

DOEpatents

Patterson, III, Raymond B.

1984-05-22

A high temperature current mirror amplifier having biasing means in the transdiode connection of the input transistor for producing a voltage to maintain the base-collector junction reversed-biased and a current means for maintaining a current through the biasing means at high temperatures so that the base-collector junction of the input transistor remained reversed-biased. For accuracy, a second current mirror is provided with a biasing means and current means on the input leg.

Design of ultra-low power biopotential amplifiers for biosignal acquisition applications.

PubMed

Zhang, Fan; Holleman, Jeremy; Otis, Brian P

2012-08-01

Rapid development in miniature implantable electronics are expediting advances in neuroscience by allowing observation and control of neural activities. The first stage of an implantable biosignal recording system, a low-noise biopotential amplifier (BPA), is critical to the overall power and noise performance of the system. In order to integrate a large number of front-end amplifiers in multichannel implantable systems, the power consumption of each amplifier must be minimized. This paper introduces a closed-loop complementary-input amplifier, which has a bandwidth of 0.05 Hz to 10.5 kHz, an input-referred noise of 2.2 μ Vrms, and a power dissipation of 12 μW. As a point of comparison, a standard telescopic-cascode closed-loop amplifier with a 0.4 Hz to 8.5 kHz bandwidth, input-referred noise of 3.2 μ Vrms, and power dissipation of 12.5 μW is presented. Also for comparison, we show results from an open-loop complementary-input amplifier that exhibits an input-referred noise of 3.6 μ Vrms while consuming 800 nW of power. The two closed-loop amplifiers are fabricated in a 0.13 μ m CMOS process. The open-loop amplifier is fabricated in a 0.5 μm SOI-BiCMOS process. All three amplifiers operate with a 1 V supply.

Direct generation of 128-fs Gaussian pulses from a compensation-free fiber laser using dual mode-locking mechanisms

NASA Astrophysics Data System (ADS)

Peng, Junsong; Zhan, Li; Gu, Zhaochang; Qian, Kai; Luo, Shouyu; Shen, Qishun

2012-03-01

We have experimentally demonstrated the direct generation of 128-fs pulses in an all-anomalous-dispersion all-fiber mode-locked laser. The laser is free of dispersion compensation in the cavity based on standard single mode fiber (SMF). The time-bandwidth product is 0.536. The laser is achieved by using two mode-lockers, one is nonlinear polarization rotation (NPR), and the other is nonlinear amplifying loop mirror. The coexistence of dual mode-locking mechanisms can decrease the cavity length to 12-m, and also results in producing high-quality pulses with a Gaussian shape both on the pulse profile and spectrum, but without Kelly sidebands.

Dual-pulses and harmonic patterns of a square-wave soliton in passively mode-locked fiber laser

NASA Astrophysics Data System (ADS)

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Zhang, Jing; Jia, Qingsong; Jiang, Huilin

2018-06-01

We demonstrate a square-wave soliton pulse passively mode-locked fiber laser. The mode-locked pulses are achieved by using a nonlinear amplifying loop mirror. Single-pulse operation at a fundamental repetition rate of 3.2 MHz is obtained. The optical spectrum presents the soliton feature of several sidebands. The pulse duration expands with increasing pump power, but the amplitude hardly varies. Pulse breaking occurs and a stable dual-pulse is obtained with a fixed interval of 48 ns. Harmonic mode-locked states can be achieved when the total pump power is higher than 740 mW. The harmonic pulses can also operate in both single-pulse and dual-pulse states.

High temperature current mirror amplifier

DOEpatents

Patterson, R.B. III.

1984-05-22

Disclosed is a high temperature current mirror amplifier having biasing means in the transdiode connection of the input transistor for producing a voltage to maintain the base-collector junction reversed-biased and a current means for maintaining a current through the biasing means at high temperatures so that the base-collector junction of the input transistor remained reversed-biased. For accuracy, a second current mirror is provided with a biasing means and current means on the input leg. 2 figs.

Over 10-watt pico-second diffraction-limited output from a Nd:YVO4 slab amplifier with a phase conjugate mirror.

PubMed

Ojima, Yasukuni; Nawata, Kouji; Omatsu, Takashige

2005-10-31

We have produced a high beam quality pico-second laser based on a continuous-wave diode pumped Nd:YVO4 slab amplifier with a photorefractive phase conjugate mirror. 12.8W diffraction-limited output with a pulse width of 8.7ps was obtained.

System and circuitry to provide stable transconductance for biasing

NASA Technical Reports Server (NTRS)

Garverick, Steven L. (Inventor); Yu, Xinyu (Inventor)

2012-01-01

An amplifier system can include an input amplifier configured to receive an analog input signal and provide an amplified signal corresponding to the analog input signal. A tracking loop is configured to employ delta modulation for tracking the amplified signal, the tracking loop providing a corresponding output signal. A biasing circuit is configured to adjust a bias current to maintain stable transconductance over temperature variations, the biasing circuit providing at least one bias signal for biasing at least one of the input amplifier and the tracking loop, whereby the circuitry receiving the at least one bias signal exhibits stable performance over the temperature variations. In another embodiment the biasing circuit can be utilized in other applications.

Birefringent Fiber Devices and Lasers

NASA Astrophysics Data System (ADS)

Theimer, James Prentice

1995-01-01

This thesis presents the results of numerical simulations of mode-locked figure eight lasers and their components: fiber amplifiers and nonlinear optical loop mirrors (NOLMs). The computations were designed to study pulse evolution in optical amplifiers and NOLMs with periodic repetition of these elements. Since fiber laser systems also include birefringent fiber, the effects of fiber birefringence was incorporated into the simulations. My studies of pulse amplification in non-birefringent amplifiers show pulse breakup when their energies exceed 4.5 fundamental soliton energies. In birefringent fibers pulse breakup is also found, but the two orthogonally polarized pulses propagate together. I find that their behavior is related to the properties of a vector soliton. I found that vector waves have close to unity transmission through a birefringent NOLM, but the pulse shape is distorted. This shape distortion reduces subsequent transmissions through the NOLM. The energy required for peak transmission of the pulse is predicted by the theory based on vector solitons. The same theory also predicted the low intensity transmission. The performance of the NOLM with birefringent fiber could not be improved by altering the polarization state of the pulse from linear polarization; the polarization controller introduced pulse distortion that resulted in excessive loss. I found an instability in the steady-state operation of the figure eight laser, which is due to pulse reshaping during propagation in the amplifier section. To remove this instability I introduced the concept of dispersion balancing; by increasing the dispersion in the amplifier section, the pulse can propagate nearly as a fundamental soliton in both the amplifier and the NOLM sections of the laser. This eliminated a major source of dispersive wave shedding and allowed the laser operation to become independent of the amplifier length. Sidebands were found on the pulse spectrum and their maxima corresponded well with the periodic resonance model.

Environmentally stable all-PM all-fiber giant chirp oscillator.

PubMed

Erkintalo, Miro; Aguergaray, Claude; Runge, Antoine; Broderick, Neil G R

2012-09-24

We report on an environmentally stable giant chirp oscillator operating at 1030 nm. Thanks to the use of a nonlinear amplifying loop mirror as the mode-locker, we are able to extract pulse energies in excess of 10 nJ from a robust all-PM cavity with no free-space elements. Extensive numerical simulations reveal that the output oscillator energy and duration can simply be up-scaled through the lengthening of the cavity with suitably positioned single-mode fiber. Experimentally, using different cavity lengths we have achieved environmentally stable mode-locking at 10, 3.7 and 1.7 MHz with corresponding pulse energies of 2.3, 10 and 16 nJ. In all cases external grating-pair compression below 400 fs has been demonstrated.

Deflection amplifier for image dissectors

NASA Technical Reports Server (NTRS)

Salomon, P. M.

1977-01-01

Balanced symmetrical y-axis amplifier uses zener-diode level shifting to interface operational amplifiers to high voltage bipolar output stages. Nominal voltage transfer characteristic is 40 differential output volts per input volt; bandwidth, between -3-dB points, is approximately 8 kHz; loop gain is nominally 89 dB with closed loop gain of 26 dB.

Nonlinear mirror modelocking of a bounce geometry laser.

PubMed

Thomas, G M; Bäuerle, A; Farrell, D J; Damzen, M J

2010-06-07

We present the investigation of nonlinear mirror modelocking (NLM) of a bounce amplifier laser. This technique, a potential rival to SESAM modelocking, uses a nonlinear crystal and a dichroic mirror to passively modelock a Nd:GdVO(4) slab bounce amplifier operating at 1063nm. At 11.3W, we present the highest power achieved using the NLM technique, using type-II phase-matched KTP, with a pulse duration of 57ps. Using type-I phase-matched BiBO, modelocking was achieved with a shorter pulse duration of 5.7ps at an average power of 7.1W.

12 J, 10 Hz diode-pumped Nd:YAG distributed active mirror amplifier chain with ASE suppression.

PubMed

Liu, Tinghao; Sui, Zhan; Chen, Lin; Li, Zhupeng; Liu, Qiang; Gong, Mali; Fu, Xing

2017-09-04

Experimental amplification of 10-ns pulses to an energy of 12.2 J at the repetition rate of 1-10 Hz is reported from a diode-pumped room-temperature distributed active mirror amplifier chain (DAMAC) based on Nd:YAG slabs. Efficient power scaling at the optical-optical efficiency of 20.6% was achieved by suppressing the transverse parasitic oscillation with ASE absorbers. To the best of our knowledge, this is the first demonstration of a diode-pumped Nd:YAG active-mirror laser with nanosecond pulse energy beyond 10 joules. The verified DAMAC concept holds the promise of scaling the energy to a 50 J level and higher by adding 10-12 more pieces of active mirror in the chain.

Dual-range linearized transimpedance amplifier system

DOEpatents

Wessendorf, Kurt O.

2010-11-02

A transimpedance amplifier system is disclosed which simultaneously generates a low-gain output signal and a high-gain output signal from an input current signal using a single transimpedance amplifier having two different feedback loops with different amplification factors to generate two different output voltage signals. One of the feedback loops includes a resistor, and the other feedback loop includes another resistor in series with one or more diodes. The transimpedance amplifier system includes a signal linearizer to linearize one or both of the low- and high-gain output signals by scaling and adding the two output voltage signals from the transimpedance amplifier. The signal linearizer can be formed either as an analog device using one or two summing amplifiers, or alternately can be formed as a digital device using two analog-to-digital converters and a digital signal processor (e.g. a microprocessor or a computer).

PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Reversal of the contrast of optical radiation in round-trip amplifiers with a phase conjugation mirror

NASA Astrophysics Data System (ADS)

Afanas'ev, Anatolii A.; Samson, B. A.

1989-02-01

A description is given of a method for inversion of the contrast of optical radiation in a round-trip amplifier with a phase conjugation mirror and a phase nonreciprocal element. The system can be used to achieve high powers of contrast-reversed radiation because of compensation of phase distortions introduced by amplification.

A 16-Channel CMOS Chopper-Stabilized Analog Front-End ECoG Acquisition Circuit for a Closed-Loop Epileptic Seizure Control System.

PubMed

Wu, Chung-Yu; Cheng, Cheng-Hsiang; Chen, Zhi-Xin

2018-06-01

In this paper, a 16-channel analog front-end (AFE) electrocorticography signal acquisition circuit for a closed-loop seizure control system is presented. It is composed of 16 input protection circuits, 16 auto-reset chopper-stabilized capacitive-coupled instrumentation amplifiers (AR-CSCCIA) with bandpass filters, 16 programmable transconductance gain amplifiers, a multiplexer, a transimpedance amplifier, and a 128-kS/s 10-bit delta-modulated successive-approximation-register analog-to-digital converter (SAR ADC). In closed-loop seizure control system applications, the stimulator shares the same electrode with the AFE amplifier for effective suppression of epileptic seizures. To prevent from overstress in MOS devices caused by high stimulation voltage, an input protection circuit with a high-voltage-tolerant switch is proposed for the AFE amplifier. Moreover, low input-referred noise is achieved by using the chopper modulation technique in the AR-CSCCIA. To reduce the undesired effects of chopper modulation, an improved offset reduction loop is proposed to reduce the output offset generated by input chopper mismatches. The digital ripple reduction loop is also used to reduce the chopper ripple. The fabricated AFE amplifier has 49.1-/59.4-/67.9-dB programmable gain and 2.02-μVrms input referred noise in a bandwidth of 0.59-117 Hz. The measured power consumption of the AFE amplifier is 3.26 μW per channel, and the noise efficiency factor is 3.36. The in vivo animal test has been successfully performed to verify the functions. It is shown that the proposed AFE acquisition circuit is suitable for implantable closed-loop seizure control systems.

LINC-NIRVANA piston control elements

NASA Astrophysics Data System (ADS)

Brix, Mario; Pott, Jörg-Uwe; Bertram, Thomas; Rost, Steffen; Borelli, Jose Luis; Herbst, Thomas M.; Kuerster, Martin; Rohloff, Ralf-Rainer

2010-07-01

We review the status of hardware developments related to the Linc-Nirvana optical path difference (OPD) control. The status of our telescope vibration measurements is given. We present the design concept of a feed-forward loop to damp the impact of telescope mirror vibrations on the OPD seen by Linc-Nirvana. At the focus of the article is a description of the actuator of the OPD control loop. The weight and vibration optimized construction of this actuator (aka piston mirror) and its mount has a complex dynamical behavior, which prevents classical PI feedback control from delivering fast and precise motion of the mirror surface. Therefore, an H-; optimized control strategy will be applied, custom designed for the piston mirror. The effort of realizing a custom controller on a DSP to drive the piezo is balanced by the outlook of achieving more than 5x faster servo bandwidths. The laboratory set-up to identify the system, and verify the closed loop control performance is presented. Our goal is to achieve 30 Hz closed-loop control bandwidth at a precision of 30 nm.

Laser beam pulse formatting method

DOEpatents

Daly, T.P.; Moses, E.I.; Patterson, R.W.; Sawicki, R.H.

1994-08-09

A method for formatting a laser beam pulse using one or more delay loops is disclosed. The delay loops have a partially reflective beam splitter and a plurality of highly reflective mirrors arranged such that the laser beam pulse enters into the delay loop through the beam splitter and circulates therein along a delay loop length defined by the mirrors. As the laser beam pulse circulates within the delay loop a portion thereof is emitted upon each completed circuit when the laser beam pulse strikes the beam splitter. The laser beam pulse is thereby formatted into a plurality of sub-pulses. The delay loops are used in combination to produce complex waveforms by combining the sub-pulses using additive waveform synthesis. 8 figs.

Numerical analysis of amplification of picosecond pulses in a THL-100 laser system with an increase in the pump energy of the XeF(C – A) amplifier

NASA Astrophysics Data System (ADS)

Yastremskii, A. G.; Ivanov, N. G.; Losev, V. F.

2018-03-01

Energy characteristics of laser radiation with a pulse width of 50 ps at an elevated pump energy of the XeF(C – A) amplifier of a hybrid THL-100 laser system are analysed numerically. The dynamics of the change in the energy and maximum intensity of laser radiation with an increase in the pump energy of the XeF(C – A) amplifier from 270 to 400 J is investigated. The results of studying the influence of the input beam divergence on the energy characteristics of the output beam are presented. It is shown that, for the existing system of mirrors, an increase in the pump energy to 400 J leads to an increase in the output energy from 3.2 to 5.5 J at a maximum radiation intensity of 57 GW cm-2. A system of amplifier mirrors with 27 laser beam passes and enlarged divergence angle of the amplified beam is considered. Theoretically, the proposed system of mirrors allows one to increase the laser pulse energy to 7.5 J at a maximum intensity of no more than 14.8 GW cm-2. The calculated efficiency of the conversion of the pump energy absorbed in the amplifier gas chamber into the lasing energy exceeds 3% in this regime.

Robust optical signal-to-noise ratio monitoring scheme using a phase-modulator-embedded fiber loop mirror.

PubMed

Ku, Yuen-Ching; Chan, Chun-Kit; Chen, Lian-Kuan

2007-06-15

We propose and experimentally demonstrate a novel in-band optical signal-to-noise ratio (OSNR) monitoring technique using a phase-modulator-embedded fiber loop mirror. This technique measures the in-band OSNR accurately by observing the output power of a fiber loop mirror filter, where the transmittance is adjusted by an embedded phase modulator driven by a low-frequency periodic signal. The measurement errors are less than 0.5 dB for an OSNR between 0 and 40 dB in a 10 Gbit/s non-return-to-zero system. This technique was also shown experimentally to have high robustness against various system impairments and high feasibility to be deployed in practical implementation.

Calibration and optimization of an x-ray bendable mirror using displacement-measuring sensors.

PubMed

Vannoni, Maurizio; Martín, Idoia Freijo; Music, Valerija; Sinn, Harald

2016-07-25

We propose a method to control and to adjust in a closed-loop a bendable x-ray mirror using displacement-measuring devices. For this purpose, the usage of capacitive and interferometric sensors is investigated and compared. We installed the sensors in a bender setup and used them to continuously measure the position and shape of the mirror in the lab. The sensors are vacuum-compatible such that the same concept can also be applied in final conditions. The measurement is used to keep the calibration of the system and to create a closed-loop control compensating for external influences: in a demonstration measurement, using a 950 mm long bendable mirror, the mirror sagitta is kept stable inside a range of 10 nm Peak-To-Valley (P-V).

Development of Low Noise-Broadband Raman Amplification Systems Based on Photonic Crystal Fibers for High Capacity DWDM Networks

NASA Astrophysics Data System (ADS)

Elgamri, Abdelghafor

The increased demand from IP traffic, video application and cell backhaul has placed fiber routes under severe stains. The high demands for large bandwidth from enormous numbers from cell sites on a network made the capacity of yesterday's networks not adequate for today's bandwidth demand. Carries considered Dense Wavelength Division Multiplexing (DWDM) network to overcome this issue. Recently, there has been growing interest in fiber Raman amplifiers due to their capability to upgrade the wavelength-division-multiplexing bandwidth, arbitrary gain bandwidth. In addition, photonic crystal fibers have been widely modeled, studied, and fabricated due to their peculiar properties that cannot be achieved with conventional fibers. The focus of this thesis is to develop a low-noise broadband Raman amplification system based on photonic crystal Fiber that can be implemented in high capacity DWDM network successfully. The design a module of photonic crystal fiber Raman amplifier is based on the knowledge of the fiber cross-sectional characteristics i.e. the geometric parameters and the Germania concentration in the dope area. The module allows to study different air-hole dimension and disposition, with or without a central doped area. In addition the design integrates distributed Raman amplifier and nonlinear optical loop mirror to improve the signal to noise ratio and overall gain in large capacity DWDM networks.

Controlling the 1 μm spontaneous emission in Er/Yb co-doped fiber amplifiers.

PubMed

Sobon, Grzegorz; Kaczmarek, Pawel; Antonczak, Arkadiusz; Sotor, Jaroslaw; Abramski, Krzysztof M

2011-09-26

In this paper we present our experimental studies on controlling the amplified spontaneous emission (ASE) from Yb(3+) ions in Er/Yb co-doped fiber amplifiers. We propose a new method of controlling the Yb-ASE by stimulating a laser emission at 1064 nm in the amplifier, by providing a positive 1 μm signal feedback loop. The results are discussed and compared to a conventional amplifier setup without 1 μm ASE control and to an amplifier with auxiliary 1064 nm seeding. We have shown, that applying a 1064 nm signal loop in an Er/Yb amplifier can increase the output power at 1550 nm and provide stable operation without parasitic lasing at 1 μm. © 2011 Optical Society of America

DC superconducting quantum interference device usable in nuclear quadrupole resonance and zero field nuclear magnetic spectrometers

DOEpatents

Fan, N.Q.; Clarke, J.

1993-10-19

A spectrometer for measuring the nuclear quadrupole resonance spectra or the zero-field nuclear magnetic resonance spectra generated by a sample is disclosed. The spectrometer uses an amplifier having a dc SQUID operating in a flux-locked loop for generating an amplified output as a function of the intensity of the signal generated by the sample. The flux-locked loop circuit includes an integrator. The amplifier also includes means for preventing the integrator from being driven into saturation. As a result, the time for the flux-locked loop to recover from the excitation pulses generated by the spectrometer is reduced. 7 figures.

DC superconducting quantum interference device usable in nuclear quadrupole resonance and zero field nuclear magnetic spectrometers

DOEpatents

Fan, Non Q.; Clarke, John

1993-01-01

A spectrometer for measuring the nuclear quadrupole resonance spectra or the zero-field nuclear magnetic resonance spectra generated by a sample is disclosed. The spectrometer uses an amplifier having a dc SQUID operating in a flux-locked loop for generating an amplified output as a function of the intensity of the signal generated by the sample. The flux-locked loop circuit includes an integrator. The amplifier also includes means for preventing the integrator from being driven into saturation. As a result, the time for the flux-locked loop to recover from the excitation pulses generated by the spectrometer is reduced.

Laser beam pulse formatting method

DOEpatents

Daly, Thomas P.; Moses, Edward I.; Patterson, Ralph W.; Sawicki, Richard H.

1994-01-01

A method for formatting a laser beam pulse (20) using one or more delay loops (10). The delay loops (10) have a partially reflective beam splitter (12) and a plurality of highly reflective mirrors (14) arranged such that the laser beam pulse (20) enters into the delay loop (10) through the beam splitter (12) and circulates therein along a delay loop length (24) defined by the mirrors (14). As the laser beam pulse (20) circulates within the delay loop (10) a portion thereof is emitted upon each completed circuit when the laser beam pulse (20) strikes the beam splitter (12). The laser beam pulse (20) is thereby formatted into a plurality of sub-pulses (50, 52, 54 and 56). The delay loops (10) are used in combination to produce complex waveforms by combining the sub-pulses (50, 52, 54 and 56) using additive waveform synthesis.

Analysis of TMT primary mirror control-structure interaction

NASA Astrophysics Data System (ADS)

MacMynowski, Douglas G.; Thompson, Peter M.; Sirota, Mark J.

2008-07-01

The primary mirror control system (M1CS) keeps the 492 segments of the Thirty Meter Telescope primary mirror aligned in the presence of disturbances. A global position control loop uses feedback from inter-segment edge sensors to three actuators behind each segment that control segment piston, tip and tilt. If soft force actuators are used (e.g. voice-coil), then in addition to the global position loop there will be a local servo loop to provide stiffness. While the M1 control system at Keck compensates only for slow disturbances such as gravity and thermal variations, the M1CS for TMT will need to provide some compensation for higher frequency wind disturbances in order to meet stringent error budget targets. An analysis of expected high-wavenumber wind forces on M1 suggests that a 1Hz control bandwidth is required for the global feedback of segment edge-sensorbased position information in order to minimize high spatial frequency segment response for both seeing-limited and adaptive optics performance. A much higher bandwidth is required from the local servo loop to provide adequate stiffness to wind or acoustic disturbances. A related paper presents the control designs for the local actuator servo loops. The disturbance rejection requirements would not be difficult to achieve for a single segment, but the structural coupling between segments mounted on a flexible mirror cell results in controlstructure interaction (CSI) that limits the achievable bandwidth. Using a combination of simplified modeling to build intuition and the full telescope finite element model for verification, we present designs and analysis for both the local servo loop and global loop demonstrating sufficient bandwidth and resulting wind-disturbance rejection despite the presence of CSI.

Pulse compression and prepulse suppression apparatus

DOEpatents

Dane, Clifford B.; Hackel, Lloyd A.; George, Edward V.; Miller, John L.; Krupke, William F.

1993-01-01

A pulse compression and prepulse suppression apparatus (10) for time compressing the output of a laser (14). A pump pulse (46) is separated from a seed pulse (48) by a first polarized beam splitter (20) according to the orientation of a half wave plate (18). The seed pulse (48) is directed into an SBS oscillator (44) by two plane mirrors (22, 26) and a corner mirror (24), the corner mirror (24) being movable to adjust timing. The pump pulse (46) is directed into an SBS amplifier 34 wherein SBS occurs. The seed pulse (48), having been propagated from the SBS oscillator (44), is then directed through the SBS amplifier (34) wherein it sweeps the energy of the pump pulse (46) out of the SBS amplifier (34) and is simultaneously compressed, and the time compressed pump pulse (46) is emitted as a pulse output (52). A second polarized beam splitter (38) directs any undepleted pump pulse 58 away from the SBS oscillator (44).

Pulse compression and prepulse suppression apparatus

DOEpatents

Dane, C.B.; Hackel, L.A.; George, E.V.; Miller, J.L.; Krupke, W.F.

1993-11-09

A pulse compression and prepulse suppression apparatus (10) for time compressing the output of a laser (14). A pump pulse (46) is separated from a seed pulse (48) by a first polarized beam splitter (20) according to the orientation of a half wave plate (18). The seed pulse (48) is directed into an SBS oscillator (44) by two plane mirrors (22, 26) and a corner mirror (24), the corner mirror (24) being movable to adjust timing. The pump pulse (46) is directed into an SBS amplifier 34 wherein SBS occurs. The seed pulse (48), having been propagated from the SBS oscillator (44), is then directed through the SBS amplifier (34) wherein it sweeps the energy of the pump pulse (46) out of the SBS amplifier (34) and is simultaneously compressed, and the time compressed pump pulse (46) is emitted as a pulse output (52). A second polarized beam splitter (38) directs any undepleted pump pulse 58 away from the SBS oscillator (44).

978-nm square-wave in an all-fiber single-mode ytterbium-doped fiber laser

NASA Astrophysics Data System (ADS)

Li, Shujie; Xu, Lixin; Gu, Chun

2018-01-01

A 978 nm single mode passively mode-locked all-fiber laser delivering square-wave pulses was demonstrated using a figure-8 cavity and a 75 cm commercial double-clad ytterbium-doped fiber. We found the three-level system near 978 nm was able to operate efficiently under clad pumping, simultaneously oscillation around 1030 nm well inhibited. The optimized nonlinear amplifying loop mirror made the mode locking stable and performed the square-pulses shaping. To the best of our knowledge, it is the first time to report the square-wave pulse fiber laser operating at 980 nm. The spectral width of the 978 mode-locked square pulses was about 4 nm, far greater than that of the mode-locked square pulses around 1060 nm reported before, which would be helpful to deeply understand the various square-wave pulses' natures and forming mechanisms. Compared with modulated single-mode or multimode 980 nm LDs, this kind of 980 nm square-wave sources having higher brightness, more steeper rising and falling edge and shorter pulse width, might have potential applications in pumping nanosecond ytterbium or erbium fiber lasers and amplifiers.

Noise and noise figure of vertical-cavity semiconductor optical amplifiers (VCSOAs) operated in reflection mode

NASA Astrophysics Data System (ADS)

Wen, Pengyue; Sanchez, Michael; Gross, Matthias; Esener, Sadik C.

2003-05-01

In this paper, the noise properties of vertical cavity semiconductor optical amplifiers (VCSOAs) operated in reflection mode are studied. Expressions for noise sources contributing to the total noise detected at amplifier output are derived, based on the photon statistics master equations. The noise figure, defined as the degradation of signal-to-noise ratio (SNR), is analyzed using the assumption that spontaneous emission-signal beat noise dominates. The analysis shows that the noise figure of reflection mode VCSOAs has the same values as that in transmission mode as long as amplifier gain is high (G>>1). Furthermore, simulations depict the dependence of noise figure on device parameters and bias conditions, as well as reveal the importance of the low reflectivity front mirror and the high reflectivity rear mirror for low noise operation. In addition, the noise figure analysis results are compared with experimental measurements, in which amplified spontaneous emission (ASE) power is measured by an optical spectrum analyzer and the noise figure is obtained from the ASE power and the amplifier gain. The measured data are in good agreement with the theoretical predictions.

Multi-pass light amplifier

NASA Technical Reports Server (NTRS)

Plaessmann, Henry (Inventor); Grossman, William M. (Inventor); Olson, Todd E. (Inventor)

1996-01-01

A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A resonator or a White Cell cavity is provided, including two or more mirrors (planar or curvilinearly shaped) facing each other along a resonator axis and an optical gain medium positioned on a resonator axis between the mirrors or adjacent to one of the mirrors. In a first embodiment, two curvilinear mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator. A second embodiment uses two curvilinear mirrors and one planar mirror, with a gain medium positioned in the optical path between each curvilinear mirror and the planar mirror. A third embodiment uses two curvilinear mirrors and two planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses a curvilinear mirror and three planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses four planar mirrors and a focusing lens system, with a gain medium positioned between the four mirrors. A fifth embodiment uses first and second planar mirrors, a focusing lens system and a third mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the third mirror. A sixth embodiment uses two planar mirrors and a curvilinear mirror and a fourth mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the fourth mirror. In a seventh embodiment, first and second mirrors face a third mirror, all curvilinear, in a White Cell configuration, and a gain medium is positioned adjacent to one of the mirrors.

Ultrahigh-speed phaselocked-loop type clock recovery circuit using a travelling-wave laser diode amplifier as a 50 GHz phase detector

NASA Astrophysics Data System (ADS)

Kawanishi, S.; Takara, H.; Saruwatari, M.; Kitoh, T.

1993-09-01

Successful operation of a phase-locked loop is demonstrated using a traveling-wave laser-diode amplifier as a 50 GHz phase detector. Optical gain modulation in the laser diode amplifier and an all-optical clock multiplication technique using a silica-based guided-wave optical circuit are used to achieve the extremely high-speed operation. Also discussed is the possibility of more than 100 GHz operation.

Learning the Art of Electronics

NASA Astrophysics Data System (ADS)

Hayes, Thomas C.; Horowitz, Paul

2016-03-01

1. DC circuits; 2. RC circuits; 3. Diode circuits; 4. Transistors I; 5. Transistors II; 6. Operational amplifiers I; 7. Operational amplifiers II: nice positive feedback; 8. Operational amplifiers III; 9. Operational amplifiers IV: nasty positive feedback; 10. Operational amplifiers V: PID motor control loop; 11. Voltage regulators; 12. MOSFET switches; 13. Group audio project; 14. Logic gates; 15. Logic compilers, sequential circuits, flip-flops; 16. Counters; 17. Memory: state machines; 18. Analog to digital: phase-locked loop; 19. Microcontrollers and microprocessors I: processor/controller; 20. I/O, first assembly language; 21. Bit operations; 22. Interrupt: ADC and DAC; 23. Moving pointers, serial buses; 24. Dallas Standalone Micro, SiLabs SPI RAM; 25. Toys in the attic; Appendices; Index.

Multi-pass light amplifier

NASA Technical Reports Server (NTRS)

Plaessmann, Henry (Inventor); Grossman, William M. (Inventor)

1997-01-01

A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A confocal resonator or White Cell resonator is provided, including two or three curvilinearly shaped mirrors facing each other along a resonator axis and an optical gain medium positioned on the resonator axis between the mirrors (confocal resonator) or adjacent to one of the mirrors (White Cell). In a first embodiment, two mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator. The optical gain medium may be solid-state, liquid or gaseous medium and may be pumped longitudinally or transversely. In a second embodiment, first and second mirrors face a third mirror in a White Cell configuration, and the optical gain medium is positioned at or adjacent to one of the mirrors. Defocusing means and optical gain medium cooling means are optionally provided with either embodiment, to controllably defocus the light beam, to cool the optical gain medium and to suppress thermal lensing in the gain medium.

Analysis and design of segment control system in segmented primary mirror

NASA Astrophysics Data System (ADS)

Yu, Wenhao; Li, Bin; Chen, Mo; Xian, Hao

2017-10-01

Segmented primary mirror will be adopted widely in giant telescopes in future, such as TMT, E-ELT and GMT. High-performance control technology of the segmented primary mirror is one of the difficult technologies for telescopes using segmented primary mirror. The control of each segment is the basis of control system in segmented mirror. Correcting the tilt and tip of single segment is the main work of this paper which is divided into two parts. Firstly, harmonic response done in finite element model of single segment matches the Bode diagram of a two-order system whose natural frequency is 45 hertz and damping ratio is 0.005. Secondly, a control system model is established, and speed feedback is introduced in control loop to suppress resonance point gain and increase the open-loop bandwidth, up to 30Hz or even higher. Corresponding controller is designed based on the control system model described above.

Influence of cross-phase modulation in SPM-based nonlinear optical loop mirror

NASA Astrophysics Data System (ADS)

Pitois, Stéphane

2005-09-01

We study the role of cross-phase modulation (CPM) occurring between the two counter-propagating parts of a signal wave in a standard SPM-based nonlinear optical fiber loop mirror (NOLM). For pulse train with high duty-cycle, we experimentally observe the influence of cross-phase modulation on NOLM transmittivity. Finally, we propose a solution based on properly designed dispersion imbalanced NOLM to overcome undesirable CPM effects.

Fabry-Perot resonators with transverse coupling on SOI using loop mirrors

NASA Astrophysics Data System (ADS)

Saber, Md Ghulam; Abadía, Nicolás; Wang, Yun; Plant, David V.

2018-05-01

A novel integrated transversely coupled Fabry-Perot resonator using loop mirrors as the end reflectors are demonstrated via simulations and experiments on the silicon-on-insulator (SOI) platform. The resonator is formed by connecting two loop mirrors to the two output ports of a directional coupler to form the resonant cavity and utilizing the other two ports as the input and the output. Depending on which two ports of the directional coupler are mirrored, two configurations of the resonator can be achieved. The impacts of varying the cavity length and the coupling coefficient of the directional coupler on the output characteristics of the resonators are analyzed. A Q-factor of 28086 and an extinction ratio of 10.04 dB with an insertion loss of 1.9 dB is achieved experimentally for a 1038 μm cavity length and an extinction ratio of 18.14 dB and a Q-factor of 5120 with an insertion loss of 2.12 dB is obtained for a cavity length of 376 μm. The reported resonator offers additional freedom to tune the spectral characteristics.

Preliminary studies of radiation coupling between remote soft X-ray laser amplifiers

NASA Astrophysics Data System (ADS)

Cairns, G.; Lewis, C. L. S.; Macphee, A. G.; Neely, D.; Holden, M.; Krishnan, J.; Tallents, G. J.; Key, M. H.; Norreys, P. N.; Smith, C. G.; Zhang, J.; Holden, P. B.; Pert, G. J.; Plowes, J.; Ramsden, S. A.

1994-01-01

Coupling of a soft X-ray laser beam with a relaying concave mirror in a sequentially pumped amplifier geometry using the Ne-like Ge system has been studied experimentally. Preliminary observations indicate an increase in the spatial coherence of the amplified relayed beam. In addition, near-field imaging of one of the amplifier plasmas shows a double-lobed intensity pattern of the emergent beam indicating refractive guiding of the amplified beam with components both normal and tangential to the target surface.

Phasing surface emitting diode laser outputs into a coherent laser beam

DOEpatents

Holzrichter, John F [Berkeley, CA

2006-10-10

A system for generating a powerful laser beam includes a first laser element and at least one additional laser element having a rear laser mirror, an output mirror that is 100% reflective at normal incidence and <5% reflective at an input beam angle, and laser material between the rear laser mirror and the output mirror. The system includes an injector, a reference laser beam source, an amplifier and phase conjugater, and a combiner.

PLZT Ceramic Driving Rotary Micro-mirror Based on Photoelectric-electrostatic Mechanism

NASA Astrophysics Data System (ADS)

Tang, Yujuan; Yang, Zhong; Chen, Yusong; Wang, Xinjie

2017-12-01

Based on the anomalous photovoltaic effect of PLZT, a rotary micro-mirror driven by hybrid photoelectric-electrostatic actuation of PLZT ceramic is proposed. Firstly, the mathematical modelling of coupled multi-physics fields of PLZT ceramic is established during illumination and light off phases. Then, the relationship between the rotation angle and the photovoltage of PLZT ceramics is established. In addition, the feasibility of rotary micro-mirror with hybrid photoelectric-electrostatic driving is verified via closed-loop control for photo-induced voltage of PLZT ceramic. The experimental results show that the photo-induced voltage of PLZT ceramics has good dynamic control precision using on-off closed-loop control method.

Tunable multi-wavelength SOA based linear cavity dual-output port fiber laser using Lyot-Sagnac loop mirror.

PubMed

Ummy, M A; Madamopoulos, N; Joyo, A; Kouar, M; Dorsinville, R

2011-02-14

We propose and demonstrate a simple dual port tunable from the C- to the L-band multi-wavelength fiber laser based on a SOA designed for C-band operation and fiber loop mirrors. The laser incorporates a polarization maintaining fiber in one of the fiber loop mirrors and delivers multi-wavelength operation at 9 laser lines with a wavelength separation of ~2.8 nm at room temperature. We show that the number of lasing wavelengths increases with the increase of the bias current of the SOA. Wavelength tunability from the C to L-band is achieved by exploiting the gain compression of a SOA. Stable multi-wavelength operation is achieved at room temperature without temperature compensation techniques, with measured power and the wavelength stability within < ±0.5 dB and 
±0.1 nm, respectively.

Phase-Locked Optical Generation of mmW/THz Signals

DTIC Science & Technology

2009-11-01

22 6.2. TIA (Trans-Impedance Amplifier ...24 6.3. Variable gain Amplifier ...loop architectures. Generate models including detector impulse response, feedback amplifier impulse response and laser current tuning response

Model-Based Angular Scan Error Correction of an Electrothermally-Actuated MEMS Mirror

PubMed Central

Zhang, Hao; Xu, Dacheng; Zhang, Xiaoyang; Chen, Qiao; Xie, Huikai; Li, Suiqiong

2015-01-01

In this paper, the actuation behavior of a two-axis electrothermal MEMS (Microelectromechanical Systems) mirror typically used in miniature optical scanning probes and optical switches is investigated. The MEMS mirror consists of four thermal bimorph actuators symmetrically located at the four sides of a central mirror plate. Experiments show that an actuation characteristics difference of as much as 4.0% exists among the four actuators due to process variations, which leads to an average angular scan error of 0.03°. A mathematical model between the actuator input voltage and the mirror-plate position has been developed to predict the actuation behavior of the mirror. It is a four-input, four-output model that takes into account the thermal-mechanical coupling and the differences among the four actuators; the vertical positions of the ends of the four actuators are also monitored. Based on this model, an open-loop control method is established to achieve accurate angular scanning. This model-based open loop control has been experimentally verified and is useful for the accurate control of the mirror. With this control method, the precise actuation of the mirror solely depends on the model prediction and does not need the real-time mirror position monitoring and feedback, greatly simplifying the MEMS control system. PMID:26690432

Stable photosensor amplifiers

NASA Technical Reports Server (NTRS)

Fujimoto, H.

1972-01-01

Minimization of common mode effects in differential amplifier arrangement which processes signals from two high impedance photosensors is achieved by connecting one photosensor in feedback loop of amplifier and using field effect transistors in the input circuit.

Vector nature of multi-soliton patterns in a passively mode-locked figure-eight fiber laser.

PubMed

Ning, Qiu-Yi; Liu, Hao; Zheng, Xu-Wu; Yu, Wei; Luo, Ai-Ping; Huang, Xu-Guang; Luo, Zhi-Chao; Xu, Wen-Cheng; Xu, Shan-Hui; Yang, Zhong-Min

2014-05-19

The vector nature of multi-soliton dynamic patterns was investigated in a passively mode-locked figure-eight fiber laser based on the nonlinear amplifying loop mirror (NALM). By properly adjusting the cavity parameters such as the pump power level and intra-cavity polarization controllers (PCs), in addition to the fundamental vector soliton, various vector multi-soliton regimes were observed, such as the random static distribution of vector multiple solitons, vector soliton cluster, vector soliton flow, and the state of vector multiple solitons occupying the whole cavity. Both the polarization-locked vector solitons (PLVSs) and the polarization-rotating vector solitons (PRVSs) were observed for fundamental soliton and each type of multi-soliton patterns. The obtained results further reveal the fundamental physics of multi-soliton patterns and demonstrate that the figure-eight fiber lasers are indeed a good platform for investigating the vector nature of different soliton types.

Experimental investigation into generation of bursts of linearly-polarized, dissipative soliton pulses from a figure-eight fiber laser at 1.03 µm

NASA Astrophysics Data System (ADS)

Ko, Seunghwan; Lee, Junsu; Koo, Joonhoi; Lee, Ju Han

2018-03-01

We experimentally demonstrate a simple and stable all-polarization maintaining fiber (PMF) nonlinear amplifying loop mirror (NALM)-based burst pulse fiber laser with a pulse number tuning capability, which can readily generate bursts of linearly-polarized femtosecond pulses at 1030 nm. The laser was based on an NALM that was operated to produce burst-mode, dissipative soliton pulses at a wavelength of 1030 nm, and these were then compressed into 400 fs Gaussian pulses using a grating pair-based compressor. The laser was constructed with the figure-eight configuration incorporating ytterbium-doped fiber as gain medium. It was shown that the number of burst pulses was readily tunable through the adjustment of the pump power. Further, the output-pulse characteristics were quantitatively investigated and the laser stability was checked by observing the temporal characteristic variation of the output pulses for one hour.

Feedback Augmented Sub-Ranging (FASR) Quantizer

NASA Technical Reports Server (NTRS)

Guilligan, Gerard

2012-01-01

This innovation is intended to reduce the size, power, and complexity of pipeline analog-to-digital converters (ADCs) that require high resolution and speed along with low power. Digitizers are important components in any application where analog signals (such as light, sound, temperature, etc.) need to be digitally processed. The innovation implements amplification of a sampled residual voltage in a switched capacitor amplifier stage that does not depend on charge redistribution. The result is less sensitive to capacitor mismatches that cause gain errors, which are the main limitation of such amplifiers in pipeline ADCs. The residual errors due to mismatch are reduced by at least a factor of 16, which is equivalent to at least 4 bits of improvement. The settling time is also faster because of a higher feedback factor. In traditional switched capacitor residue amplifiers, closed-loop amplification of a sampled and held residue signal is achieved by redistributing sampled charge onto a feedback capacitor around a high-gain transconductance amplifier. The residual charge that was sampled during the acquisition or sampling phase is stored on two or more capacitors, often equal in value or integral multiples of each other. During the hold or amplification phase, all of the charge is redistributed onto one capacitor in the feedback loop of the amplifier to produce an amplified voltage. The key error source is the non-ideal ratios of feedback and input capacitors caused by manufacturing tolerances, called mismatches. The mismatches cause non-ideal closed-loop gain, leading to higher differential non-linearity. Traditional solutions to the mismatch errors are to use larger capacitor values (than dictated by thermal noise requirements) and/or complex calibration schemes, both of which increase the die size and power dissipation. The key features of this innovation are (1) the elimination of the need for charge redistribution to achieve an accurate closed-loop gain of two, (2) a higher feedback factor in the amplifier stage giving a higher closed-loop bandwidth compared to the prior art, and (3) reduced requirement for calibration. The accuracy of the new amplifier is mainly limited by the sampling networks parasitic capacitances, which should be minimized in relation to the sampling capacitors.

First on-sky demonstration of the piezoelectric adaptive secondary mirror.

PubMed

Guo, Youming; Zhang, Ang; Fan, Xinlong; Rao, Changhui; Wei, Ling; Xian, Hao; Wei, Kai; Zhang, Xiaojun; Guan, Chunlin; Li, Min; Zhou, Luchun; Jin, Kai; Zhang, Junbo; Deng, Jijiang; Zhou, Longfeng; Chen, Hao; Zhang, Xuejun; Zhang, Yudong

2016-12-15

We propose using a piezoelectric adaptive secondary mirror (PASM) in the medium-sized adaptive telescopes with a 2-4 m aperture for structure and control simplification by utilizing the piezoelectric actuators in contrast with the voice-coil adaptive secondary mirror. A closed-loop experimental setup was built for on-sky demonstration of the 73-element PASM developed by our laboratory. In this Letter, the PASM and the closed-loop adaptive optics system are introduced. High-resolution stellar images were obtained by using the PASM to correct high-order wavefront errors in May 2016. To the best of our knowledge, this is the first successful on-sky demonstration of the PASM. The results show that with the PASM as the deformable mirror, the angular resolution of the 1.8 m telescope can be effectively improved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joung, M.; Woo, M. H.; Jeong, J. H.

For a high-performance, advanced tokamak mode in KSTAR, we have been developing a real-time control system of MHD modes such as sawtooth and Neo-classical Tearing Mode (NTM) by ECH/ECCD. The active feedback control loop will be also added to the mirror position and the real-time detection of the mode position. In this year, for the stabilization of NTM that is crucial to plasma performance we have implemented open-loop ECH antenna control system in KSTAR Plasma Control System (PCS) for ECH mirror movement during a single plasma discharge. KSTAR 170 GHz ECH launcher which was designed and fabricated by collaboration withmore » PPPL and POSTECH has a final mirror of a poloidally and toroidally steerable mirror. The poloidal steering motion is only controlled in the real-time NTM control system and its maximum steering speed is 10 degree/sec by DC motor. However, the latency of the mirror control system and the return period of ECH antenna mirror angle are not fast because the existing launcher mirror control system is based on PLC which is connected to the KSTAR machine network through serial to LAN converter. In this paper, we present the design of real time NTM control system, ECH requirements, and the upgrade plan.« less

10 W single-mode Er/Yb co-doped all-fiber amplifier with suppressed Yb-ASE

NASA Astrophysics Data System (ADS)

Sobon, G.; Sliwinska, D.; Abramski, K. M.; Kaczmarek, P.

2014-02-01

In this work we demonstrate a single-frequency, single-mode all-fiber master oscillator power amplifier (MOPA) source, based on erbium-ytterbium co-doped double-clad fiber emitting 10 W of continuous wave power at 1565 nm. In the power amplifier stage, the amplified spontaneous emission from Yb3+ ions (Yb-ASE) is forced to recirculate in a loop resonator in order to provide stable lasing at 1060 nm. The generated signal acts as an additional pump source for the amplifier and is reabsorbed by the Yb3+ ions in the active fiber, allowing an increase in the efficiency and boosting the output power. The feedback loop also protects the amplifier from parasitic lasing or self-pulsing at a wavelength of 1 μm. This allows one to significantly scale the output power in comparison to a conventional setup without any Yb-ASE control.

Active rc filter permits easy trade-off of amplifier gain and sensitivity to gain

NASA Technical Reports Server (NTRS)

Kerwin, W. J.; Shaffer, C. V.

1968-01-01

Passive RC network was designed with zeros of transmission in the right half of the complex frequency plane in the feedback loop of a simple negative-gain amplifier. The proper positioning provides any desired trade-off between amplifier gain and sensitivity to amplifier gain.

Tunable narrow linewidth all-fiber thulium-doped fiber laser in a 2 µm-band using two Hi-Bi fiber optical loop mirrors

NASA Astrophysics Data System (ADS)

Posada-Ramírez, B.; Durán-Sánchez, M.; Álvarez-Tamayo, R. I.; Ibarra-Escamilla, B.; Hernández-Arriaga, M. V.; Sánchez-de-la-Llave, D.; Kuzin, E. A.

2017-08-01

We propose an all-fiber Tm-doped fiber laser with a tunable and narrow laser line generated in a wavelength region of 2 µm. A single laser line with a linewidth below 0.05 nm, tunable in a wavelength range of 44.25 nm, is obtained. The laser linewidth and the discrete wavelength tuning range depend on the characteristics of the two fiber optical loop mirrors with high birefringence in the loop that forms the cavity. Dual-wavelength laser operation is also observed at tuning range limits with a wavelength separation of 47 nm. Alternate wavelength switching is also observed.

Hysteresis compensation of piezoelectric deformable mirror based on Prandtl-Ishlinskii model

NASA Astrophysics Data System (ADS)

Ma, Jianqiang; Tian, Lei; Li, Yan; Yang, Zongfeng; Cui, Yuguo; Chu, Jiaru

2018-06-01

Hysteresis of piezoelectric deformable mirror (DM) reduces the closed-loop bandwidth and the open-loop correction accuracy of adaptive optics (AO) systems. In this work, a classical Prandtl-Ishlinskii (PI) model is employed to model the hysteresis behavior of a unimorph DM with 20 actuators. A modified control algorithm combined with the inverse PI model is developed for piezoelectric DMs. With the help of PI model, the hysteresis of the DM was reduced effectively from about 9% to 1%. Furthermore, open-loop regenerations of low-order aberrations with or without hysteresis compensation were carried out. The experimental results demonstrate that the regeneration accuracy with PI model compensation is significantly improved.

Time Difference Amplifier with Robust Gain Using Closed-Loop Control

NASA Astrophysics Data System (ADS)

Nakura, Toru; Mandai, Shingo; Ikeda, Makoto; Asada, Kunihiro

This paper presents a Time Difference Amplifier (TDA) that amplifies the input time difference into the output time difference. Cross coupled chains of variable delay cells with the same number of stages are applicable for TDA, and the gain is adjusted via the closed-loop control. The TDA was fabricated using 65nm CMOS and the measurement results show that the time difference gain is 4.78 at a nominal power supply while the designed gain is 4.0. The gain is stable enough to be less than 1.4% gain shift under ±10% power supply voltage fluctuation.

Design of the deformable mirror demonstration CubeSat (DeMi)

NASA Astrophysics Data System (ADS)

Douglas, Ewan S.; Allan, Gregory; Barnes, Derek; Figura, Joseph S.; Haughwout, Christian A.; Gubner, Jennifer N.; Knoedler, Alex A.; LeClair, Sarah; Murphy, Thomas J.; Skouloudis, Nikolaos; Merck, John; Opperman, Roedolph A.; Cahoy, Kerri L.

2017-09-01

The Deformable Mirror Demonstration Mission (DeMi) was recently selected by DARPA to demonstrate in-space operation of a wavefront sensor and Microelectromechanical system (MEMS) deformable mirror (DM) payload on a 6U CubeSat. Space telescopes designed to make high-contrast observations using internal coronagraphs for direct characterization of exoplanets require the use of high-actuator density deformable mirrors. These DMs can correct image plane aberrations and speckles caused by imperfections, thermal distortions, and diffraction in the telescope and optics that would otherwise corrupt the wavefront and allow leaking starlight to contaminate coronagraphic images. DeMi is provide on-orbit demonstration and performance characterization of a MEMS deformable mirror and closed loop wavefront sensing. The DeMi payload has two operational modes, one mode that images an internal light source and another mode which uses an external aperture to images stars. Both the internal and external modes include image plane and pupil plane wavefront sensing. The objectives of the internal measurement of the 140-actuator MEMS DM actuator displacement are characterization of the mirror performance and demonstration of closed-loop correction of aberrations in the optical path. Using the external aperture to observe stars of magnitude 2 or brighter, assuming 3-axis stability with less than 0.1 degree of attitude knowledge and jitter below 10 arcsec RMSE, per observation, DeMi will also demonstrate closed loop wavefront control on an astrophysical target. We present an updated payload design, results from simulations and laboratory optical prototyping, as well as present our design for accommodating high-voltage multichannel drive electronics for the DM on a CubeSat.

Discovery Channel Telescope active optics system early integration and test

NASA Astrophysics Data System (ADS)

Venetiou, Alexander J.; Bida, Thomas A.

2012-09-01

The Discovery Channel Telescope (DCT) is a 4.3-meter telescope with a thin meniscus primary mirror (M1) and a honeycomb secondary mirror (M2). The optical design is an f/6.1 Ritchey-Chrétien (RC) with an unvignetted 0.5° Field of View (FoV) at the Cassegrain focus. We describe the design, implementation and performance of the DCT active optics system (AOS). The DCT AOS maintains collimation and controls the figure of the mirror to provide seeing-limited images across the focal plane. To minimize observing overhead, rapid settling times are achieved using a combination of feed-forward and low-bandwidth feedback control using a wavefront sensing system. In 2011, we mounted a Shack-Hartmann wavefront sensor at the prime focus of M1, the Prime Focus Test Assembly (PFTA), to test the AOS with the wavefront sensor, and the feedback loop. The incoming wavefront is decomposed using Zernike polynomials, and the mirror figure is corrected with a set of bending modes. Components of the system that we tested and tuned included the Zernike to Bending Mode transformations. We also started open-loop feed-forward coefficients determination. In early 2012, the PFTA was replaced by M2, and the wavefront sensor moved to its normal location on the Cassegrain instrument assembly. We present early open loop wavefront test results with the full optical system and instrument cube, along with refinements to the overall control loop operating at RC Cassegrain focus.

Enhancement of the beam quality of non-uniform output slab laser amplifier with a 39-actuator rectangular piezoelectric deformable mirror.

PubMed

Yang, Ping; Ning, Yu; Lei, Xiang; Xu, Bing; Li, Xinyang; Dong, Lizhi; Yan, Hu; Liu, Wenjing; Jiang, Wenhan; Liu, Lei; Wang, Chao; Liang, Xingbo; Tang, Xiaojun

2010-03-29

We present a slab laser amplifier beam cleanup experimental system based on a 39-actuator rectangular piezoelectric deformable mirror. Rather than use a wave-front sensor to measure distortions in the wave-front and then apply a conjugation wave-front for compensating them, the system uses a Stochastic Parallel Gradient Descent algorithm to maximize the power contained within a far-field designated bucket. Experimental results demonstrate that at the output power of 335W, more than 30% energy concentrates in the 1x diffraction-limited area while the beam quality is enhanced greatly.

Real time MHD mode control using ECCD in KSTAR: Plan and requirements

NASA Astrophysics Data System (ADS)

Joung, M.; Woo, M. H.; Jeong, J. H.; Hahn, S. H.; Yun, S. W.; Lee, W. R.; Bae, Y. S.; Oh, Y. K.; Kwak, J. G.; Yang, H. L.; Namkung, W.; Park, H.; Cho, M. H.; Kim, M. H.; Kim, K. J.; Na, Y. S.; Hosea, J.; Ellis, R.

2014-02-01

For a high-performance, advanced tokamak mode in KSTAR, we have been developing a real-time control system of MHD modes such as sawtooth and Neo-classical Tearing Mode (NTM) by ECH/ECCD. The active feedback control loop will be also added to the mirror position and the real-time detection of the mode position. In this year, for the stabilization of NTM that is crucial to plasma performance we have implemented open-loop ECH antenna control system in KSTAR Plasma Control System (PCS) for ECH mirror movement during a single plasma discharge. KSTAR 170 GHz ECH launcher which was designed and fabricated by collaboration with PPPL and POSTECH has a final mirror of a poloidally and toroidally steerable mirror. The poloidal steering motion is only controlled in the real-time NTM control system and its maximum steering speed is 10 degree/sec by DC motor. However, the latency of the mirror control system and the return period of ECH antenna mirror angle are not fast because the existing launcher mirror control system is based on PLC which is connected to the KSTAR machine network through serial to LAN converter. In this paper, we present the design of real time NTM control system, ECH requirements, and the upgrade plan.

NONLINEAR OPTICAL EFFECTS AND FIBER OPTICS: Pulsed neodymium amplifier with phase conjugation and direct amplification

NASA Astrophysics Data System (ADS)

Basov, N. G.; Efimkov, V. F.; Zubarev, I. G.; Kolobrodov, V. V.; Pastukhov, S. A.; Smirnov, M. G.; Sobolev, V. B.

1988-12-01

A study was made of the characteristics of an amplifier containing neodymium-activated silicate rods, 45 mm in diameter, used in direct amplification and phase conjugation systems. At low output energies the divergence of the output radiation in the presence of a phase-conjugating mirror was half ( ~ 10- 4 rad) that in the case of direct amplification. An increase in the output power caused the divergence to rise more rapidly in the presence of a phase-conjugating mirror, which was tentatively attributed to an earlier manifestation of large-scale self-focusing. Output energies of 130 J in the case of direct amplification and 80 J in the presence of a phase-conjugating mirror were obtained when the output pulse duration was ~ 2 ns and the fraction of the total energy contained within an angle of ~ 10- 4 rad was ~ 0.3.

Gain equalization in cascaded optical amplifiers using short-period Bragg gratings

NASA Astrophysics Data System (ADS)

Rochette, Martin; Cortes, Pierre-Yves; Guy, Martin; LaRochelle, Sophie; Trepanier, Francois; Lauzon, Jocelyn

2000-12-01

Gain equalization of an amplifier is performed by introducing spectrally designed Bragg gratings in the mid-stage of a dual-stage erbium-doped fiber amplifier. The long-haul performances of the amplifier are evaluated using a 50 km recirculating loop. The results show a clear improvement of the transmission quality when equalizing the gain.

Improved-Bandwidth Transimpedance Amplifier

NASA Technical Reports Server (NTRS)

Chapsky, Jacob

2009-01-01

The widest available operational amplifier, with the best voltage and current noise characteristics, is considered for transimpedance amplifier (TIA) applications where wide bandwidth is required to handle fast rising input signals (as for time-of-flight measurement cases). The added amplifier inside the TIA feedback loop can be configured to have slightly lower voltage gain than the bandwidth reduction factor.

Differential transimpedance amplifier circuit for correlated differential amplification

DOEpatents

Gresham, Christopher A [Albuquerque, NM; Denton, M Bonner [Tucson, AZ; Sperline, Roger P [Tucson, AZ

2008-07-22

A differential transimpedance amplifier circuit for correlated differential amplification. The amplifier circuit increase electronic signal-to-noise ratios in charge detection circuits designed for the detection of very small quantities of electrical charge and/or very weak electromagnetic waves. A differential, integrating capacitive transimpedance amplifier integrated circuit comprising capacitor feedback loops performs time-correlated subtraction of noise.

Agency over Phantom Limb Enhanced by Short-Term Mirror Therapy

PubMed Central

Imaizumi, Shu; Asai, Tomohisa; Koyama, Shinichi

2017-01-01

Most amputees experience phantom limb, whereby they feel that the amputated limb is still present. In some cases, these experiences include pain that can be alleviated by “mirror therapy.” Mirror therapy consists of superimposing a mirrored image of the moving intact limb onto the phantom limb. This therapy provides a closed loop between the motor command to the amputated limb and its predicted visual feedback. This loop is also involved in the sense of agency, a feeling of controlling one’s own body. However, it is unclear how mirror therapy is related to the sense of agency over a phantom limb. Using mirror therapy, we investigated phantom limb pain and the senses of agency and ownership (i.e., a feeling of having one’s own body) of the phantom limb. Nine upper-limb amputees, five of whom reported recent phantom limb pain, underwent a single 15-min trial of mirror therapy. Before and after the trial, the participants completed a questionnaire regarding agency, ownership, and pain related to their phantom limb. They reported that the sense of agency over the phantom limb increased following the mirror therapy trial, while the ownership slightly increased but not as much as did the agency. The reported pain did not change; that is, it was comparably mild before and after the trial. These results suggest that short-term mirror therapy can, at least transiently, selectively enhance the sense of agency over a phantom limb, but may not alleviate phantom limb pain. PMID:29046630

Agency over Phantom Limb Enhanced by Short-Term Mirror Therapy.

PubMed

Imaizumi, Shu; Asai, Tomohisa; Koyama, Shinichi

2017-01-01

Most amputees experience phantom limb, whereby they feel that the amputated limb is still present. In some cases, these experiences include pain that can be alleviated by "mirror therapy." Mirror therapy consists of superimposing a mirrored image of the moving intact limb onto the phantom limb. This therapy provides a closed loop between the motor command to the amputated limb and its predicted visual feedback. This loop is also involved in the sense of agency, a feeling of controlling one's own body. However, it is unclear how mirror therapy is related to the sense of agency over a phantom limb. Using mirror therapy, we investigated phantom limb pain and the senses of agency and ownership (i.e., a feeling of having one's own body) of the phantom limb. Nine upper-limb amputees, five of whom reported recent phantom limb pain, underwent a single 15-min trial of mirror therapy. Before and after the trial, the participants completed a questionnaire regarding agency, ownership, and pain related to their phantom limb. They reported that the sense of agency over the phantom limb increased following the mirror therapy trial, while the ownership slightly increased but not as much as did the agency. The reported pain did not change; that is, it was comparably mild before and after the trial. These results suggest that short-term mirror therapy can, at least transiently, selectively enhance the sense of agency over a phantom limb, but may not alleviate phantom limb pain.

Modeling and Simulation of a Parametrically Resonant Micromirror With Duty-Cycled Excitation.

PubMed

Shahid, Wajiha; Qiu, Zhen; Duan, Xiyu; Li, Haijun; Wang, Thomas D; Oldham, Kenn R

2014-12-01

High frequency large scanning angle electrostatically actuated microelectromechanical systems (MEMS) mirrors are used in a variety of applications involving fast optical scanning. A 1-D parametrically resonant torsional micromirror for use in biomedical imaging is analyzed here with respect to operation by duty-cycled square waves. Duty-cycled square wave excitation can have significant advantages for practical mirror regulation and/or control. The mirror's nonlinear dynamics under such excitation is analyzed in a Hill's equation form. This form is used to predict stability regions (the voltage-frequency relationship) of parametric resonance behavior over large scanning angles using iterative approximations for nonlinear capacitance behavior of the mirror. Numerical simulations are also performed to obtain the mirror's frequency response over several voltages for various duty cycles. Frequency sweeps, stability results, and duty cycle trends from both analytical and simulation methods are compared with experimental results. Both analytical models and simulations show good agreement with experimental results over the range of duty cycled excitations tested. This paper discusses the implications of changing amplitude and phase with duty cycle for robust open-loop operation and future closed-loop operating strategies.

Stable multi-wavelength fiber lasers for temperature measurements using an optical loop mirror.

PubMed

Diaz, Silvia; Socorro, Abian Bentor; Martínez Manuel, Rodolfo; Fernandez, Ruben; Monasterio, Ioseba

2016-10-10

In this work, two novel stable multi-wavelength fiber laser configurations are proposed and demonstrated by using a spool of a single-mode fiber as an optical loop mirror and one or two fiber ring cavities, respectively. The lasers are comprised of fiber Bragg grating reflectors as the oscillation wavelength selecting filters. The influence of the length of the spool of fiber on the laser stability both in terms of wavelength and laser output power was investigated. An application for temperature measurement is also shown.

Multiwavelength erbium-doped fiber laser employing a nonlinear optical loop mirror

NASA Astrophysics Data System (ADS)

Feng, Xinhuan; Tam, Hwa-yaw; Liu, Heliang; Wai, P. K. A.

2006-12-01

A stable and broad bandwidth multiwavelength erbium-doped fiber laser is proposed and demonstrated successfully. A nonlinear optical loop mirror which induces wavelength-dependent cavity loss and behaves as an amplitude equalizer is employed to ensure stable room-temperature multiwavelength operation. Up to 50 wavelengths lasing oscillations with wavelength spacing of 0.8 nm within a 3-dB spectral range of 1562-1605 nm has been achieved. The measured power fluctuation of each wavelength is about 0.1 dB within a 2-h period.

Fiber lasers with loop reflectors.

PubMed

Urquhart, P

1989-09-01

The theory of homogeneously broadened four level fiber lasers, which use fiber loops as distributed reflective elements, is examined. Such cavities can be made entirely from rare earth doped fiber. The amplifying characteristics of doped fiber loops are examined. The threshold pump power and the loop reflectivity necessary to optimize the lasing output power from an oscillator formed from two loops in series are predicted.

Current status of Kumgang laser system

NASA Astrophysics Data System (ADS)

Kong, Hong Jin; Park, Sangwoo; Ahn, HeeKyung; Lee, Hwihyeong; Oh, Jungsuk; Kim, Jom Sool

2015-02-01

In KAIST, Kumgang laser is being developed for demonstration of the kW level coherent beam combination using stimulated Brillouin scattering phase conjugation mirrors. It will combine 4 modules of DPSSL rod amplifier which produces 1 kW output power. It is composed of the single frequency front-end, pre-amplifier module, and main amplifier. The output powers of the pre-amp and main amplifier module are 200 W (20 mJ @ 10 kHz / 10 ns) and 1.07kW (107 mJ @ 10 kHz / 10 ns), respectively.

High power lasers for gamma source

NASA Astrophysics Data System (ADS)

Durand, Magali; Sangla, Damien; Trophème, Benoit; Sevillano, Pierre; Casanova, Alexis; Caillon, Laurianne; Courjaud, Antoine

2017-02-01

A high intensity Gamma source is required for Nuclear Spectroscopy, it will be delivered by the interaction between accelerated electron and intense laser beams. Those two interactions lasers are based on a multi-stage amplification scheme that ended with a second harmonics generation to deliver 200 mJ, 3.5 ps pulses at 515 nm and 100 Hz. A t-Pulse oscillator with slow and fast feedback loop implemented inside the oscillator cavity allows the possibility of synchronization to an optical reference. A temporal jitter of 120 fs rms is achieved, integrated from 10 Hz to 10 MHz. Then a regenerative amplifier, based on Yb:YAG technology, pumped by fiber-coupled QCW laser diodes, delivers pulses up to 30 mJ. The 1 nm bandwidth was compressed to 1.5 ps with a good spatial quality: M2 of 1.1. This amplifier is integrated in a compact sealed housing (750x500x150 cm), which allows a pulse-pulse stability of 0.1% rms, and a long-term stability of 1,9% over 100 hours (with +/-1°C environment). The main amplification stage uses a cryocooled Yb:YAG crystal in an active mirror configuration. The crystal is cooled at 130 K via a compact and low-vibration cryocooler, avoiding any additional phase noise contribution, 340 mJ in a six pass scheme was achieved, with 0.9 of Strehl ratio. The trade off to the gain of a cryogenic amplifier is the bandwidth reduction, however the 1030 nm pulse was compressed to 3.5 ps.

High-efficiency cyrogenic-cooled diode-pumped amplifier with relay imaging for nanosecond pulses

NASA Astrophysics Data System (ADS)

Körner, J.; Hein, J.; Kahle, M.; Liebetrau, H.; Kaluza, M.; Siebold, M.; Loeser, M.

2011-06-01

We present temperature dependent gain measurements with different Ytterbium doped laser media, such as Yb:YAG, Yb:FP15-glass and Yb:CaF2 in a multi-pass amplifier setup. The temperature of these materials was adjusted arbitrarily between 100K and 300K, while heat removal was realized by transverse cooling. In order to obtain a good beam profile throughout the amplification process, we used an all-mirror based relay imaging setup consisting of a telescope accomplishing a 4f-imaging with a plane mirror in each image plane. The amplification beam is then coupled into the cavity and doing several round trips wandering over the surface of the spherical mirrors. Hence the laser material is placed in one of the image planes, the beam quality of the amplifier was ruled by the intensity profile of the pumping laser diodes consisting of two stacks with 2.5kW peak output power each. Due to the given damage threshold fluence, the output energy of the amplifier was limited to about 1J at a beam diameter of 4.5 mm (FWHM). The seed pulses with a duration of 6 ns were generated in a Yb:FP15-glass cavity dumped oscillator with further amplification up to the 100mJ level by a room temperature Yb:YAG multi pass amplifier. The 1 Hz repetition rate of the system was limited by the repetition rate of the front-end. With Yb:YAG for instance an output energy of 1.1 J with an record high optical to optical efficiency of more than 35% was achieved, which was further increased to 45% for 500 mJ output energy.

Decreased oscillation threshold of a continuous-wave OPO using a semiconductor gain mirror.

PubMed

Siltanen, Mikael; Leinonen, Tomi; Halonen, Lauri

2011-09-26

We have constructed a singly resonant, continuous-wave optical parametric oscillator, where the signal beam resonates and is amplified by a semiconductor gain mirror. The gain mirror can significantly decrease the oscillation threshold compared to an identical system with conventional mirrors. The largest idler beam tuning range reached by changing the pump laser wavelength alone is from 3.6 to 4.7 µm. The single mode output power is limited but can be continuously scanned for at least 220 GHz by adding optical components in the oscillator cavity for increased stability. © 2011 Optical Society of America

Multistaged stokes injected Raman capillary waveguide amplifier

DOEpatents

Kurnit, Norman A.

1980-01-01

A multistaged Stokes injected Raman capillary waveguide amplifier for providing a high gain Stokes output signal. The amplifier uses a plurality of optically coupled capillary waveguide amplifiers and one or more regenerative amplifiers to increase Stokes gain to a level sufficient for power amplification. Power amplification is provided by a multifocused Raman gain cell or a large diameter capillary waveguide. An external source of CO.sub.2 laser radiation can be injected into each of the capillary waveguide amplifier stages to increase Raman gain. Devices for injecting external sources of CO.sub.2 radiation include: dichroic mirrors, prisms, gratings and Ge Brewster plates. Alternatively, the CO.sub.2 input radiation to the first stage can be coupled and amplified between successive stages.

High-Power Laser Source Evaluation

DTIC Science & Technology

1998-07-01

uniform:«»! had been:taped. A sample beam profile at the receiver Zerodur Au-coated mirror 20 cm diameter f/6 Diode laser Diode bars 1 21 m beam...amplifiers and mirrors . This is of concern to the NIF Project and the use of unconverted 1.06 p.m light to produce these x-ray sources might require...they may result in DSWA Final Report - 34 NWET ANNUAL REPORT - QDV-99-0001 undesirable conditions at the turning mirrors or ghosts in the up-beam

Analysis and design of optically pumped far infrared oscillators and amplifiers

NASA Technical Reports Server (NTRS)

Galantowicz, T. A.

1978-01-01

A waveguide laser oscillator was designed and experimental measurements made of relationships among output power, pressure, pump power, pump frequency, cavity tuning, output beam pattern, and cavity mirror properties for various active gases. A waveguide regenerative amplifier was designed and gain measurements were made for various active gases. An external Fabry-Perot interferometer was fabricated and used for accurate wavelength determination and for measurements of the refractive indices of solids transparent in the far infrared. An electronic system was designed and constructed to provide an appropriate error signal for use in feedback control of pump frequency. Pump feedback from the FIR laser was decoupled using a vibrating mirror to phase modulate the pump signal.

Bio-isolated dc operational amplifier. [for bioelectric measurements

NASA Technical Reports Server (NTRS)

Lee, R. D. (Inventor)

1974-01-01

A bio-isolated dc operational amplifier is described for use in making bioelectrical measurements of a patient while providing isolation of the patient from electrical shocks. The circuit contains a first operational amplifier coupled to the patient with its output coupled in a forward loop through a first optic coupler to a second operational amplifier. The output of the second operational amplifier is coupled to suitable monitoring circuitry via a feedback circuit including a second optic coupler to the input of the first operational amplifier.

2 µm high-power dissipative soliton resonance in a compact σ-shaped Tm-doped double-clad fiber laser

NASA Astrophysics Data System (ADS)

Du, Tuanjie; Li, Weiwei; Ruan, Qiujun; Wang, Kaijie; Chen, Nan; Luo, Zhengqian

2018-05-01

We report direct generation of a high-power, large-energy dissipative soliton resonance (DSR) in a 2 µm Tm-doped double-clad fiber laser. A compact σ-shaped cavity is formed by a fiber Bragg grating and a 10/90 fiber loop mirror (FLM). The 10/90 FLM is not only used as an output mirror, but also acts as a nonlinear optical loop mirror for initiating mode locking. The mode-locked laser can deliver high-power, nanosecond DSR pulses at 2005.9 nm. We further perform a comparison study of the effect of the FLM’s loop length on the mode-locking threshold, peak power, pulse energy, and optical spectrum of the DSR pulses. We achieve a maximum average output power as high as 1.4 W, a maximum pulse energy of 353 nJ, and a maximum peak power of 84 W. This is, to the best of our knowledge, the highest power for 2 µm DSR pulses obtained in a mode-locked fiber laser.

10 GHz dual loop opto-electronic oscillator without RF-amplifiers

NASA Astrophysics Data System (ADS)

Zhou, Weimin; Okusaga, Olukayode; Nelson, Craig; Howe, David; Carter, Gary

2008-02-01

We report the first demonstration of a 10 GHz dual-fiber-loop Opto-Electronic Oscillator (OEO) without RF-amplifiers. Using a recently developed highly efficient RF-Photonic link with RF-to-RF gain facilitated by a high power laser, highly efficient optical modulator and high power phototectectors, we have built an amplifier-less OEO that eliminates the phase noise produced by the electronic amplifier. The dual-loop approach can provide additional gain and reduce unwanted multi-mode spurs. However, we have observed RF phase noise produced by the high power laser include relative intensity noise (RIN) and noise related to the laser's electronic control system. In addition, stimulated Brillouin scattering limits the fiber loop's length to ~2km at the 40mW laser power needed to provide the RF gain which limits the system's quality factor, Q. We have investigated several different methods for solving these problems. One promising technique is the use of a multi-longitudinal-mode laser to carry the RF signal, maintaining the total optical power but reducing the optical power of each mode to eliminate the Brillouin scattering in a longer fiber thereby reducing the phase noise of the RF signal produced by the OEO. This work shows that improvement in photonic components increases the potential for more RF system applications such as an OEO's with higher performance and new capabilities.

Multi-pass amplifier architecture for high power laser systems

DOEpatents

Manes, Kenneth R; Spaeth, Mary L; Erlandson, Alvin C

2014-04-01

A main amplifier system includes a first reflector operable to receive input light through a first aperture and direct the input light along an optical path. The input light is characterized by a first polarization. The main amplifier system also includes a first polarizer operable to reflect light characterized by the first polarization state. The main amplifier system further includes a first and second set of amplifier modules. Each of the first and second set of amplifier modules includes an entrance window, a quarter wave plate, a plurality of amplifier slablets arrayed substantially parallel to each other, and an exit window. The main amplifier system additionally includes a set of mirrors operable to reflect light exiting the first set of amplifier modules to enter the second set of amplifier modules and a second polarizer operable to reflect light characterized by a second polarization state.

Polarographic carbon dioxide transducer amplifier

NASA Technical Reports Server (NTRS)

Stillman, G.

1971-01-01

Electronic amplifier contains matched pair of metal oxide semiconductor field effect transistor devices which have high input impedance and long-term stability. Thermistor in feedback loop provides temperature compensation for large drifts in the sensor.

Voltage regulator/amplifier is self-regulated

NASA Technical Reports Server (NTRS)

Day, W. E.; Phillips, D. E.

1967-01-01

Signal modulated, self-regulating voltage regulator/amplifier controls the output b-plus voltage in modulated regulator systems. It uses self-oscillation with feedback to a control circuit with a discontinuous amplitude action feedback loop.

Active telescope systems; Proceedings of the Meeting, Orlando, FL, Mar. 28-31, 1989

NASA Astrophysics Data System (ADS)

Roddier, Francois J.

1989-09-01

The present conference discusses topics in the fundamental limitations of adaptive optics in astronomical telescopy, integrated telescope systems designs, novel components for adaptive telescopes, active interferometry, flexible-mirror and segmented-mirror telescopes, and various aspects of the NASA Precision Segmented Reflectors Program. Attention is given to near-ground atmospheric turbulence effects, a near-IR astronomical adaptive optics system, a simplified wavefront sensor for adaptive mirror control, excimer laser guide star techniques for adaptive astronomical imaging, active systems in long-baseline interferometry, mirror figure control primitives for a 10-m primary mirror, and closed-loop active optics for large flexible mirrors subject to wind buffet deformations. Also discussed are active pupil geometry control for a phased-array telescope, extremely lightweight space telescope mirrors, segmented-mirror manufacturing tolerances, and composite deformable mirror design.

Acoustic velocity measurements in materials using a regenerative method

DOEpatents

Laine, Edwin F.

1986-01-01

Acoustic energy is propagated through earth material between an electro-acoustic generator and a receiver which converts the received acoustic energy into electrical signals. A closed loop is formed by a variable gain amplifier system connected between the receiver and the generator. The gain of the amplifier system is increased until sustained oscillations are produced in the closed loop. The frequency of the oscillations is measured as an indication of the acoustic propagation velocity through the earth material. The amplifier gain is measured as an indication of the acoustic attenuation through the earth materials. The method is also applicable to the non-destructive testing of structural materials, such as steel, aluminum and concrete.

Acoustic-velocity measurements in materials using a regenerative method

DOEpatents

Laine, E.F.

1982-09-30

Acoustic energy is propatated through earth material between an electro-acoustic generator and a receiver which converts the received acoustic energy into electrical signals. A closed loop is formed by a variable gain amplifier system connected between the receiver and the generator. The gain of the amplifier system is increased until sustained oscillations are produced in the closed loop. The frequency of the oscillations is measured as an indication of the acoustic propagation velocity through the earth material. The amplifier gain is measured as an indication of the acoustic attenuation through the earth materials. The method is also applicable to the non-destructive testing of structural materials, such as steel, aluminum and concrete.

Dispersion management for a sub-10-fs, 10 TW optical parametric chirped-pulse amplifier.

PubMed

Tavella, Franz; Nomura, Yutaka; Veisz, Laszlo; Pervak, Vladimir; Marcinkevicius, Andrius; Krausz, Ferenc

2007-08-01

We report the amplification of three-cycle, 8.5 fs optical pulses in a near-infrared noncollinear optical parametric chirped-pulse amplifier (OPCPA) up to energies of 80 mJ. Improved dispersion management in the amplifier by means of a combination of reflection grisms and a chirped-mirror stretcher allowed us to recompress the amplified pulses to within 6% of their Fourier limit. The novel ultrabroad, ultraprecise dispersion control technology presented in this work opens the way to scaling multiterawatt technology to even shorter pulses by optimizing the OPCPA bandwidth.

Octave-spanning carrier-envelope phase stabilized visible pulse with sub-3-fs pulse duration.

PubMed

Okamura, Kotaro; Kobayashi, Takayoshi

2011-01-15

The visible second harmonic of the idler output from a noncollinear optical parametric amplifier was compressed using adaptive dispersion control with a deformable mirror. The amplifier was pumped by and seeded in the signal path by a common 400 nm second-harmonic pulse from a Ti:sapphire regenerative amplifier. Thus, both the idler output and the second harmonic of the idler were passively carrier-envelope phase stabilized. The shortest pulse duration achieved was below 3 fs.

MEMS deformable mirror for wavefront correction of large telescopes

NASA Astrophysics Data System (ADS)

Manhart, Sigmund; Vdovin, Gleb; Collings, Neil; Sodnik, Zoran; Nikolov, Susanne; Hupfer, Werner

2017-11-01

A 50 mm diameter membrane mirror was designed and manufactured at TU Delft. It is made from bulk silicon by micromachining - a technology primarily used for micro-electromechanical systems (MEMS). The mirror unit is equipped with 39 actuator electrodes and can be electrostatically deformed to correct wavefront errors in optical imaging systems. Performance tests on the deformable mirror were carried out at Astrium GmbH using a breadboard setup with a wavefront sensor and a closed-loop control system. It was found that the deformable membrane mirror is well suited for correction of low order wavefront errors as they must be expected in lightweighted space telescopes.

A digitally controlled AGC loop circuitry for GNSS receiver chip with a binary weighted accurate dB-linear PGA

NASA Astrophysics Data System (ADS)

Gang, Jin; Yiqi, Zhuang; Yue, Yin; Miao, Cui

2015-03-01

A novel digitally controlled automatic gain control (AGC) loop circuitry for the global navigation satellite system (GNSS) receiver chip is presented. The entire AGC loop contains a programmable gain amplifier (PGA), an AGC circuit and an analog-to-digital converter (ADC), which is implemented in a 0.18 μm complementary metal-oxide-semiconductor (CMOS) process and measured. A binary-weighted approach is proposed in the PGA to achieve wide dB-linear gain control with small gain error. With binary-weighted cascaded amplifiers for coarse gain control, and parallel binary-weighted trans-conductance amplifier array for fine gain control, the PGA can provide a 64 dB dynamic range from -4 to 60 dB in 1.14 dB gain steps with a less than 0.15 dB gain error. Based on the Gaussian noise statistic characteristic of the GNSS signal, a digital AGC circuit is also proposed with low area and fast settling. The feed-backward AGC loop occupies an area of 0.27 mm2 and settles within less than 165 μs while consuming an average current of 1.92 mA at 1.8 V.

Design of hybrid laser structures with QD-RSOA and silicon photonic mirrors

NASA Astrophysics Data System (ADS)

Gioannini, Mariangela; Benedetti, Alessio; Bardella, Paolo; Bovington, Jock; Traverso, Matt; Siriani, Dominic; Gothoskar, Prakash

2018-02-01

We compare the design of three different single mode laser structures consisting in a Reflective Semiconductor Optical Amplifier coupled to a silicon photonic external cavity mirror. The three designs differ for the mirror structure and are compared in terms of SOA power consumption and side mode suppression ratio (SMSR). Assuming then a Quantum Dot active material, we simulate the best laser design using a numerical model that includes the peculiar physical characteristics of the QD gain medium. The simulated QD laser CW characteristics are shown and discussed.

Gain drift compensation with no-feedback-loop developed for the X-IFU/ATHENA readout chain

NASA Astrophysics Data System (ADS)

Prêle, D.; Voisin, F.; Beillimaz, C.; Chen, S.; Goldwurm, A.

2016-07-01

The focal plane of the X-ray Integral Field Unit (X-IFU) instrument of the Athena observatory is composed of about 4000 micro-calorimeters. These sensors, based on superconducting Transition Edge Sensors, are read out through a frequency multiplexer and a base-band feedback to linearize SQUIDs. However, the loop gain of this feedback is lower than 10 in the modulated TES signal bandwidth, which is not enough to fix the gain of the full readout chain. Calibration of the instrument is planned to be done at a time scale larger than a dozen minutes and the challenging energy resolution goal of 2.5 eV at 6 keV will probably require a gain stability larger than 10-4 over a long duration. A large part of this gain is provided by a Low-Noise Amplifier (LNA) in the Warm Front-End Electronics (WFEE). To reach such gain stability over more than a dozen minutes, this non-cooled amplifier has to cope with the temperature and supply voltage variations. Moreover, mainly for noise reasons, common large loop gain with feedback can not be used. We propose a new amplifier topology using diodes as loads of a differential amplifier to provide a fixed voltage gain, independent of the temperature and of the bias fluctuations. This amplifier is designed using a 350 nm SiGe BiCMOS technology and is part of an integrated circuit developed for the WFEE. Our simulations provide the expected gain drift and noise performances of such structure. Comparison with standard resistive loaded differential pair clearly shows the advantages of the proposed amplifier topology with a gain drift decreasing by more than an order of magnitude. Performances of this diode loaded amplifier are discussed in the context of the X-IFU requirements.

Differential Amplifier with Current-Mirror Load: Influence of Current Gain, Early Voltage, and Supply Voltage on the DC Output Voltage

ERIC Educational Resources Information Center

Paulik, G. F.; Mayer, R. P.

2012-01-01

A differential amplifier composed of an emitter-coupled pair is useful as an example in lecture presentations and laboratory experiments in electronic circuit analysis courses. However, in an active circuit with zero input load V[subscript id], both laboratory measurements and PSPICE and LTspice simulation results for the output voltage…

Quantum channels from reflections on moving mirrors.

PubMed

Gianfelici, Giulio; Mancini, Stefano

2017-11-16

Light reflection on a mirror can be thought as a simple physical effect. However if this happens when the mirror moves a rich scenario opens up. Here we aim at analyzing it from a quantum communication perspective. In particular, we study the kind of quantum channel that arises from (Gaussian) light reflection upon an accelerating mirror. Two competing mechanisms emerge in such a context, namely photons production by the mirror's motion and interference between modes. As consequence we find out a quantum amplifier channel and quantum lossy channel respectively below and above a threshold frequency (that depends on parameters determining mirror's acceleration). Exactly at the threshold frequency the channel behaves like a purely classical additive channel, while it becomes purely erasure for large frequencies. In addition the time behavior of the channel is analyzed by employing wave packets expansion of the light field.

A High Input Impedance Low Noise Integrated Front-End Amplifier for Neural Monitoring.

PubMed

Zhou, Zhijun; Warr, Paul A

2016-12-01

Within neural monitoring systems, the front-end amplifier forms the critical element for signal detection and pre-processing, which determines not only the fidelity of the biosignal, but also impacts power consumption and detector size. In this paper, a novel combined feedback loop-controlled approach is proposed to compensate for input leakage currents generated by low noise amplifiers when in integrated circuit form alongside signal leakage into the input bias network. This loop topology ensures the Front-End Amplifier (FEA) maintains a high input impedance across all manufacturing and operational variations. Measured results from a prototype manufactured on the AMS 0.35 [Formula: see text] CMOS technology is provided. This FEA consumes 3.1 [Formula: see text] in 0.042 [Formula: see text], achieves input impedance of 42 [Formula: see text], and 18.2 [Formula: see text] input-referred noise.

High power green lasers for gamma source

NASA Astrophysics Data System (ADS)

Durand, Magali; Sevillano, Pierre; Alexaline, Olivier; Sangla, Damien; Casanova, Alexis; Aubourg, Adrien; Saci, Abdelhak; Courjaud, Antoine

2018-02-01

A high intensity Gamma source is required for Nuclear Spectroscopy, it will be delivered by the interaction between accelerated electron and intense laser beams. Those two interactions lasers are based on a multi-stage amplification scheme that ended with a second harmonics generation to deliver 200 mJ, 5 ps pulses at 515 nm and 100 Hz. A t-Pulse oscillator with slow and fast feedback loop implemented inside the oscillator cavity allows the possibility of synchronization to an optical reference. A temporal jitter of 120 fs rms is achieved, integrated from 10 Hz to 10 MHz. Then a regenerative amplifier, based on Yb:YAG technology, pumped by fiber-coupled QCW laser diodes, delivers pulses up to 30 mJ. The 1 nm bandwidth was compressed to 1.5 ps with a good spatial quality: M2 of 1.1. This amplifier is integrated in a compact sealed housing (750 x 500 x 150 mm), which allows a pulse-pulse stability of 0.1 % rms, and a long-term stability of 1,9 % over 100 hours (with +/-1°C environment). The main amplification stage uses a cryocooled Yb:YAG crystal in an active mirror configuration. The crystal is cooled at 130 K via a compact and low-vibration cryocooler, avoiding any additional phase noise contribution, 340 mJ in a six pass scheme was achieved, with 0.9 of Strehl ratio. The trade off to the gain of a cryogenic amplifier is the bandwidth reduction, however the 1030 nm pulse was compressed to 4.4 ps. As for the regenerative amplifier a long-term stability of 1.9 % over 30 hours was achieved in an environment with +/-1°C temperature fluctuations The compression and Second Harmonics Generation Stages have allowed the conversion of 150 mJ of uncompressed infrared beam into 60 mJ at 515 nm.

Two kinds of novel tunable Thulium-doped fiber laser

NASA Astrophysics Data System (ADS)

Ma, Xiaowei; Chen, Daru; Feng, Gaofeng; Yang, Junyong

2014-11-01

Two kinds of tunable Thulium-doped fiber laser (TDFL) respectively using a Sagnac loop mirror and a novel tunable multimode interference (MMI) fiber filter are experimentally demonstrated. The TDFL with the Sagnac loop mirror made by a 145.5-cm polarization-maintaining fiber (PMF) can operate with stable dual-wavelength lasing or tunable single-wavelength lasing around 1860nm. Both stable dual-wavelength and tunable single-wavelength lasing are achieved by adjusting a polarization controller in the Sagnac loop mirror. The TDFL with a novel tunable MMI fiber filter formed by splicing a segment of a special no-core fiber that is an all silica fiber without fiber core to single mode fibers can achieve tuning range from 1813.52 nm to 1858.70 nm. The no-core fiber with a large diameter of 200 μm is gradually vertically covered by refractive index matching liquid, which leads to a wavelength tuning of the transmission peak of the MMI fiber filter. The relationship between the refractive index of the refractive index matching liquid and the peak wavelength shift of the MMI fiber filter is also discussed. Using the MMI fiber filter, a Thulium-doped fiber laser with a tuning range of 45.18 nm is demonstrated.

Coronagraphic Wavefront Control for the ATLAST-9.2m Telescope

NASA Technical Reports Server (NTRS)

Lyon, RIchard G.; Oegerle, William R.; Feinberg, Lee D.; Bolcar, Matthew R.; Dean, Bruce H.; Mosier, Gary E.; Postman, Marc

2010-01-01

The Advanced Technology for Large Aperture Space Telescope (ATLAST) concept was assessed as one of the NASA Astrophysics Strategic Mission Concepts (ASMC) studies. Herein we discuss the 9.2-meter diameter segmented aperture version and its wavefront sensing and control (WFSC) with regards to coronagraphic detection and spectroscopic characterization of exoplanets. The WFSC would consist of at least two levels of sensing and control: (i) an outer coarser level of sensing and control to phase and control the segments and secondary mirror in a manner similar to the James Webb Space Telescope but operating at higher temporal bandwidth, and (ii) an inner, coronagraphic instrument based, fine level of sensing and control for both amplitude and wavefront errors operating at higher temporal bandwidths. The outer loop would control rigid-body actuators on the primary and secondary mirrors while the inner loop would control one or more segmented deformable mirror to suppress the starlight within the coronagraphic field-of view. Herein we discuss the visible nulling coronagraph (VNC) and the requirements it levies on wavefront sensing and control and show the results of closed-loop simulations to assess performance and evaluate the trade space of system level stability versus control bandwidth.

Low-common-mode differential amplifier

NASA Technical Reports Server (NTRS)

Morrison, S.

1980-01-01

Outputs of differential amplifier are excellently matched in phase and amplitude over wide range of frequencies. Common mode feedback loop offsets differences between two signal paths. Possible applications of circuit are in oscilloscopes, integrated circuit logic tester, and other self contained instruments.

Micro ring cavity resonator incorporating total internal reflection mirrors

NASA Astrophysics Data System (ADS)

Kim, Doo Gun; Choi, Woon Kyung; Choi, Young Wan; Yi, Jong Chang; Chung, Youngchul; Dagli, Nadir

2007-02-01

We investigate the properties of a multimode-interference (MMI) coupled micro ring cavity resonator with total-internal-reflection (TIR) mirrors and a semiconductor optical amplifier (SOA). The TIR mirrors were fabricated by the self-aligned process with a loss of 0.7 dB per mirror. The length and width of an MMI are 142 μm and 10 μm, respectively. The resulting free spectral range (FSR) of the resonator was approximately 1.698 nm near 1571 nm and the extinction ratio was about 17 dB. These devices might be useful as optical switching and add-drop filters in a photonic integrated circuit or as small and fast resonator devices.

All solid-state diode pumped Nd:YAG MOPA with stimulated Brillouin phase conjugate mirror

NASA Astrophysics Data System (ADS)

Offerhaus, H. L.; Godfried, H. P.; Witteman, W. J.

1996-02-01

At the Nederlands Centrum voor Laser Research (NCLR) a 1 kHz diode-pumped Nd:YAG Master Oscillator Power Amplifier (MOPA) chain with a Stimulated Brillouin Scattering (SBS) Phase Conjugate mirror is designed and operated. A small Brewster angle Nd:YAG slab (2 by 2 by 20 mm) is side pumped with 200 μs diode pulses in a stable oscillator. The oscillator is Q-switched and injection seeded with a commercial diode pumped single frequency CW Nd:YAG laser. The output consists of single-transverse, single-longitudinal mode 25 ns FWHM-pulses at 1064 nm. The oscillator slab is imaged on a square aperture that transmits between 3 and 2 mJ (at 100 and 400 Hz, resp.) The aperture is subsequently imaged four times in the amplifier. The amplifier is a 3 by 6 by 60 mm Brewster angle zig-zag slab, pumped by an 80-bar diode stack with pulses up to 250 μs. After the second pass the light is focused in two consecutive cells containing Freon-113 for wave-front reversal in an oscillator/amplifier-setup with a reflectivity of 60%. The light then passes through the amplifier twice more to produce 20 W (at 400 Hz) of output with near diffraction limited beam quality. To increase the output to 50 W at 1 kHz thermal lensing in the oscillator will be reduced.

A wavelength scannable XeCl oscillator-ring amplifier laser system

NASA Technical Reports Server (NTRS)

Pacala, T. J.; Mcdermid, I. S.; Laudenslager, J. B.

1982-01-01

A holographic grating at grazing angle of incidence was used to achieve tunable, narrow bandwidth (0.005 nm) operation of a XeCl oscillator for injection locking of a ring amplifier. The amplifier's narrow bandwidth output energy was constant and equal to the untuned, broadband output (approximately 15 mJ) in regions where injection locking was achieved. Scanning was provided by use of a stepping motor-driven differential micrometer on the tuning mirror. This system was used to produce a laser excitation spectrum of hydroxyl radicals (OH) in a flame.

Correcting highly aberrated eyes using large-stroke adaptive optics.

PubMed

Sabesan, Ramkumar; Ahmad, Kamran; Yoon, Geunyoung

2007-11-01

To investigate the optical performance of a large-stroke deformable mirror in correcting large aberrations in highly aberrated eyes. A large-stroke deformable mirror (Mirao 52D; Imagine Eyes) and a Shack-Hartmann wavefront sensor were used in an adaptive optics system. Closed-loop correction of the static aberrations of a phase plate designed for an advanced keratoconic eye was performed for a 6-mm pupil. The same adaptive optics system was also used to correct the aberrations in one eye each of two moderate keratoconic and three normal human eyes for a 6-mm pupil. With closed-loop correction of the phase plate, the total root-mean-square (RMS) over a 6-mm pupil was reduced from 3.54 to 0.04 microm in 30 to 40 iterations, corresponding to 3 to 4 seconds. Adaptive optics closed-loop correction reduced an average total RMS of 1.73+/-0.998 to 0.10+/-0.017 microm (higher order RMS of 0.39+/-0.124 to 0.06+/-0.004 microm) in the three normal eyes and 2.73+/-1.754 to 0.10+/-0.001 microm (higher order RMS of 1.82+/-1.058 to 0.05+/-0.017 microm) in the two keratoconic eyes. Aberrations in both normal and highly aberrated eyes were successfully corrected using the large-stroke deformable mirror to provide almost perfect optical quality. This mirror can be a powerful tool to assess the limit of visual performance achievable after correcting the aberrations, especially in eyes with abnormal corneal profiles.

Narrow line width dual wavelength semiconductor optical amplifier based random fiber laser

NASA Astrophysics Data System (ADS)

Shawki, Heba A.; Kotb, Hussein E.; Khalil, Diaa

2018-02-01

A novel narrow line-width Single longitudinal mode (SLM) dual wavelength random fiber laser of 20 nm separation between wavelengths of 1530 and 1550 nm is presented. The laser is based on Rayleigh backscattering in a standard single mode fiber of 2 Km length as distributed mirrors, and a semiconductor optical amplifier (SOA) as the optical amplification medium. Two optical bandpass filters are used for the two wavelengths selectivity, and two Faraday Rotator mirrors are used to stabilize the two lasing wavelengths against fiber random birefringence. The optical signal to noise ratio (OSNR) was measured to be 38 dB. The line-width of the laser was measured to be 13.3 and 14 KHz at 1530 and 1550 nm respectively, at SOA pump current of 370 mA.

Phase Diversity Wavefront Sensing for Control of Space Based Adaptive Optics Systems

DTIC Science & Technology

2007-12-01

given a cursory review below. 1. The Fast-Steering Mirror or “Tip- Tilt ” mirror is the simplest image corrector. It is capable of correcting for...movements either onboard the optical platform or the majority of atmospherics by applying 2-dimensional offsets in “tip and tilt .” It is used in the...SRDC 3 loop AO system discussed in Chapter V and identified in Figure 24 2. Piezoelectric Deformable Mirrors (PDM’s) use glass, silicon or fused

Parameters of loop-controlled magnetic rheology drive for segmented large mirror

NASA Astrophysics Data System (ADS)

Deulin, Eugeni A.; Mikhailov, Valeri P.; Eliseev, Oleg N.; Sytchev, Victor V.

2000-07-01

The design, parameters and the amplitude-frequency analysis of the new magnetic rheology (MR) drive are presented. The combination of hydrostatic carrier, MR hydraulic loop control, elastic thin wall seal joined in a single unit ensures small positioning error nm and small time of response T

The Emergence of Dirac points in Photonic Crystals with Mirror Symmetry

PubMed Central

He, Wen-Yu; Chan, C. T.

2015-01-01

We show that Dirac points can emerge in photonic crystals possessing mirror symmetry when band gap closes. The mechanism of generating Dirac points is discussed in a two-dimensional photonic square lattice, in which four Dirac points split out naturally after the touching of two bands with different parity. The emergence of such nodal points, characterized by vortex structure in momentum space, is attributed to the unavoidable band crossing protected by mirror symmetry. The Dirac nodes can be unbuckled through breaking the mirror symmetry and a photonic analog of Chern insulator can be achieved through time reversal symmetry breaking. Breaking time reversal symmetry can lead to unidirectional helical edge states and breaking mirror symmetry can reduce the band gap to amplify the finite size effect, providing ways to engineer helical edge states. PMID:25640993

Loop Mirror Laser Neural Network with a Fast Liquid-Crystal Display

NASA Astrophysics Data System (ADS)

Mos, Evert C.; Schleipen, Jean J. H. B.; de Waardt, Huug; Khoe, Djan G. D.

1999-07-01

In our laser neural network (LNN) all-optical threshold action is obtained by application of controlled optical feedback to a laser diode. Here an extended experimental LNN is presented with as many as 32 neurons and 12 inputs. In the setup we use a fast liquid-crystal display to implement an optical matrix vector multiplier. This display, based on ferroelectric liquid-crystal material, enables us to present 125 training examples s to the LNN. To maximize the optical feedback efficiency of the setup, a loop mirror is introduced. We use a -rule learning algorithm to train the network to perform a number of functions toward the application area of telecommunication data switching.

Single mode terahertz quantum cascade amplifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Y., E-mail: yr235@cam.ac.uk; Wallis, R.; Shah, Y. D.

2014-10-06

A terahertz (THz) optical amplifier based on a 2.9 THz quantum cascade laser (QCL) structure has been demonstrated. By depositing an antireflective coating on the QCL facet, the laser mirror losses are enhanced to fully suppress the lasing action, creating a THz quantum cascade (QC) amplifier. Terahertz radiation amplification has been obtained, by coupling a separate multi-mode THz QCL of the same active region design to the QC amplifier. A bare cavity gain is achieved and shows excellent agreement with the lasing spectrum from the original QCL without the antireflective coating. Furthermore, a maximum optical gain of ∼30 dB with single-modemore » radiation output is demonstrated.« less

Simple two-electrode biosignal amplifier.

PubMed

Dobrev, D; Neycheva, T; Mudrov, N

2005-11-01

A simple, cost effective circuit for a two-electrode non-differential biopotential amplifier is proposed. It uses a 'virtual ground' transimpedance amplifier and a parallel RC network for input common mode current equalisation, while the signal input impedance preserves its high value. With this innovative interface circuit, a simple non-inverting amplifier fully emulates high CMRR differential. The amplifier equivalent CMRR (typical range from 70-100 dB) is equal to the open loop gain of the operational amplifier used in the transimpedance interface stage. The circuit has very simple structure and utilises a small number of popular components. The amplifier is intended for use in various two-electrode applications, such as Holter-type monitors, defibrillators, ECG monitors, biotelemetry devices etc.

Solar Collector Mirror for Brayton Power System

NASA Image and Video Library

1966-09-21

NASA’s Lewis Research Center conducted extensive research programs in the 1960s and 1970s to develop systems that provide electrical power in space. One system, the Brayton cycle engine, converted solar thermal energy into electrical power. This system operated on a closed-loop Brayton thermodynamic cycle. The Brayton system relied on this large mirror to collect radiation from the sun. The mirror concentrated the Sun's rays on a heat storage receiver which warmed the Brayton system’s working fluid, a helium-xenon gas mixture. The heated fluid powered the system’s generator which produced power. In the mid-1960s Lewis researchers constructed this 30-foot diameter prototype of a parabolic solar mirror for the Brayton cycle system. The mirror had to be rigid, impervious to micrometeorite strikes, and lightweight. This mirror was comprised of twelve 1-inch thick magnesium plate sections that were coated with aluminum. The mirror could be compactly broken into its sections for launch.

The Design and Construction of a Long-Distance Atmospheric Propagation Test Chamber

DTIC Science & Technology

2015-06-01

supply, a gain medium where the light is generated and amplified, and an optical cavity consisting of one partially reflecting mirror and one fully... reflecting mirror [6]. There is also a pump stored in the optical cavity that excites electrons in the gain medium, leading to spontaneous and...Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management

Navy Shipboard Lasers for Surface, Air, and Missile Defense: Background and Issues for Congress

DTIC Science & Technology

2013-06-27

include silicon carbide ( SiC )- based transistors, transformers and power converters. “ SiC is important because it improves power quality and reduces size...existing shipboard gun systems. An airborne mirror , perhaps mounted on an aerostat,11 could bounce light from a shipboard laser, so as to permit non-line...super conducting RF electron beam injectors, advanced high power cathode technologies, high power compact amplifiers, and advanced mirrors

Steering and positioning targets for HWIL IR testing at cryogenic conditions

NASA Astrophysics Data System (ADS)

Perkes, D. W.; Jensen, G. L.; Higham, D. L.; Lowry, H. S.; Simpson, W. R.

2006-05-01

In order to increase the fidelity of hardware-in-the-loop ground-truth testing, it is desirable to create a dynamic scene of multiple, independently controlled IR point sources. ATK-Mission Research has developed and supplied the steering mirror systems for the 7V and 10V Space Simulation Test Chambers at the Arnold Engineering Development Center (AEDC), Air Force Materiel Command (AFMC). A portion of the 10V system incorporates multiple target sources beam-combined at the focal point of a 20K cryogenic collimator. Each IR source consists of a precision blackbody with cryogenic aperture and filter wheels mounted on a cryogenic two-axis translation stage. This point source target scene is steered by a high-speed steering mirror to produce further complex motion. The scene changes dynamically in order to simulate an actual operational scene as viewed by the System Under Test (SUT) as it executes various dynamic look-direction changes during its flight to a target. Synchronization and real-time hardware-in-the-loop control is accomplished using reflective memory for each subsystem control and feedback loop. This paper focuses on the steering mirror system and the required tradeoffs of optical performance, precision, repeatability and high-speed motion as well as the complications of encoder feedback calibration and operation at 20K.

Tunable all-optical signal regenerator with a semiconductor optical amplifier and a Sagnac loop: principles of operation

NASA Astrophysics Data System (ADS)

Granot, Er'el; Zaibel, Reuven; Narkiss, Niv; Ben-Ezra, Shalva; Chayet, Haim; Shahar, Nir; Sternklar, Shmuel; Tsadka, Sagie; Prucnal, Paul R.

2005-12-01

In this paper we investigate the wavelength conversion and regeneration properties of a tunable all-optical signal regenerator (TASR). In the TASR, the wavelength conversion is done by a semiconductor optical amplifier, which is incorporated in an asymmetric Sagnac loop (ASL). We demonstrate both theoretically and experimentally that the ASL regenerates the incident signal's bit pattern, reduces its noise, increases the extinction ratio (which in many aspects is equivalent to noise reduction) and improves its bit-error rate. We also demonstrate the general behavior of the TASR with a numerical simulation.

Gain drift compensation with no feedback-loop developed for the X-Ray Integral Field Unit/ATHENA readout chain

NASA Astrophysics Data System (ADS)

Prêle, Damien; Voisin, Fabrice; Beillimaz, Cyril; Chen, Si; Goldwurm, Andrea

2016-10-01

The focal plane of the X-Ray Integral Field Unit (X-IFU) instrument of the Advanced Telescope for High-Energy Astrophysics observatory is composed of 3840 microcalorimeters. These sensors, based on superconducting transition edge sensors (TES), are read out through a frequency multiplexer. A "base-band feedback" suppresses all the carriers of the multiplexed signal in the superconducting quantum interference devices input coil (cryogenic readout). However, the loop gain of this feedback is too small (less than 10 in the present baseline of the phase A mission) to strongly compensate the readout gain drifts. An onboard x-ray source is considered to calibrate the gain of the full instrument. However, in-flight calibration time must be minimized, which leads to a requirement on the gain stability larger than 10-4 over a long duration (between each calibration) to reach the challenging energy resolution goal of 2.5 eV at 6 keV of the X-IFU. A significant part of this gain is provided by a low-noise amplifier in the warm front-end electronics (WFEE). To reach such gain stability over more than a dozen minutes, this noncooled amplifier has to cope with the temperature and supply voltage variations. Moreover, mainly for noise reasons, a common large loop gain with feedback cannot be used. We propose a new amplifier topology using diodes as loads of a differential amplifier to provide a fixed voltage gain, independent of the temperature and of the bias fluctuations. This amplifier is designed using 350-nm SiGe BiCMOS technology and is part of an integrated circuit developed for the WFEE. Our simulations provide the expected gain and noise performances. Comparison with standard resistive loaded differential pair clearly shows the advantages of the proposed amplifier topology with a gain drift decreased by more than an order of magnitude. Performances of this diode loaded amplifier are discussed in the context of the X-IFU requirements.

Frequency-Offset Cartesian Feedback Based on Polyphase Difference Amplifiers

PubMed Central

Zanchi, Marta G.; Pauly, John M.; Scott, Greig C.

2010-01-01

A modified Cartesian feedback method called “frequency-offset Cartesian feedback” and based on polyphase difference amplifiers is described that significantly reduces the problems associated with quadrature errors and DC-offsets in classic Cartesian feedback power amplifier control systems. In this method, the reference input and feedback signals are down-converted and compared at a low intermediate frequency (IF) instead of at DC. The polyphase difference amplifiers create a complex control bandwidth centered at this low IF, which is typically offset from DC by 200–1500 kHz. Consequently, the loop gain peak does not overlap DC where voltage offsets, drift, and local oscillator leakage create errors. Moreover, quadrature mismatch errors are significantly attenuated in the control bandwidth. Since the polyphase amplifiers selectively amplify the complex signals characterized by a +90° phase relationship representing positive frequency signals, the control system operates somewhat like single sideband (SSB) modulation. However, the approach still allows the same modulation bandwidth control as classic Cartesian feedback. In this paper, the behavior of the polyphase difference amplifier is described through both the results of simulations, based on a theoretical analysis of their architecture, and experiments. We then describe our first printed circuit board prototype of a frequency-offset Cartesian feedback transmitter and its performance in open and closed loop configuration. This approach should be especially useful in magnetic resonance imaging transmit array systems. PMID:20814450

1.9 μm square-wave passively Q-witched mode-locked fiber laser.

PubMed

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Wang, Furen; Zhang, Jing; Wang, Chengbo; Jiang, Huilin

2018-05-14

We propose and demonstrate the operation of Q-switched mode-locked square-wave pulses in a thulium-holmium co-doped fiber laser. By using a nonlinear amplifying loop mirror, continuous square-wave dissipative soliton resonance pulse is obtained with 4.4 MHz repetition rate. With the increasing pump power, square-wave pulse duration can be broadened from 1.7 ns to 3.2 ns. On such basis Q-switched mode-locked operation is achieved by properly setting the pump power and the polarization controllers. The internal mode-locked pulses in Q-switched envelope still keep square-wave type. The Q-switched repetition rate can be varied from 41.6 kHz to 74 kHz by increasing pump power. The corresponding average single-pulse energy increases from 2.67 nJ to 5.2 nJ. The average peak power is also improved from 0.6 W to 1.1 W when continuous square-wave operation is changed into Q-switched mode-locked operation. It indicates that Q-switched mode-locked operation is an effective method to increase the square-wave pulse energy and peak power.

A 5 Gb/s CMOS adaptive equalizer for serial link

NASA Astrophysics Data System (ADS)

Wu, Hongbing; Wang, Jingyu; Liu, Hongxia

2018-04-01

A 5 Gb/s adaptive equalizer with a new adaptation scheme is presented here by using 0.13 μm CMOS process. The circuit consists of the combination of equalizer amplifier, limiter amplifier and adaptation loop. The adaptive algorithm exploits both the low frequency gain loop and the equalizer loop to minimize the inter-symbol interference (ISI) for a variety of cable characteristics. In addition, an offset cancellation loop is used to alleviate the offset influence of the signal path. The adaptive equalizer core occupies an area of 0.3567 mm2 and consumes a power consumption of 81.7 mW with 1.8 V power supply. Experiment results demonstrate that the equalizer could compensate for a designed cable loss with 0.23 UI peak-to-peak jitter. Project supported by the National Natural Science Foundation of China (No. 61376099), the Foundation for Fundamental Research of China (No. JSZL2016110B003), and the Major Fundamental Research Program of Shaanxi (No. 2017ZDJC-26).

Optical control of the Advanced Technology Solar Telescope.

PubMed

Upton, Robert

2006-08-10

The Advanced Technology Solar Telescope (ATST) is an off-axis Gregorian astronomical telescope design. The ATST is expected to be subject to thermal and gravitational effects that result in misalignments of its mirrors and warping of its primary mirror. These effects require active, closed-loop correction to maintain its as-designed diffraction-limited optical performance. The simulation and modeling of the ATST with a closed-loop correction strategy are presented. The correction strategy is derived from the linear mathematical properties of two Jacobian, or influence, matrices that map the ATST rigid-body (RB) misalignments and primary mirror figure errors to wavefront sensor (WFS) measurements. The two Jacobian matrices also quantify the sensitivities of the ATST to RB and primary mirror figure perturbations. The modeled active correction strategy results in a decrease of the rms wavefront error averaged over the field of view (FOV) from 500 to 19 nm, subject to 10 nm rms WFS noise. This result is obtained utilizing nine WFSs distributed in the FOV with a 300 nm rms astigmatism figure error on the primary mirror. Correction of the ATST RB perturbations is demonstrated for an optimum subset of three WFSs with corrections improving the ATST rms wavefront error from 340 to 17.8 nm. In addition to the active correction of the ATST, an analytically robust sensitivity analysis that can be generally extended to a wider class of optical systems is presented.

Plug-in module acceleration feedback control for fast steering mirror-based beam stabilization systems

NASA Astrophysics Data System (ADS)

Deng, Chao; Ren, Wei; Mao, Yao; Ren, Ge

2017-08-01

A plug-in module acceleration feedback control (Plug-In AFC) strategy based on the disturbance observer (DOB) principle is proposed for charge-coupled device (CCD)-based fast steering mirror (FSM) stabilization systems. In classical FSM tracking systems, dual-loop control (DLC), including velocity feedback and position feedback, is usually utilized to enhance the closed-loop performance. Due to the mechanical resonance of the system and CCD time delay, the closed-loop bandwidth is severely restricted. To solve this problem, cascade acceleration feedback control (AFC), which is a kind of high-precision robust control method, is introduced to strengthen the disturbance rejection property. However, in practical applications, it is difficult to realize an integral algorithm in an acceleration controller to compensate for the quadratic differential contained in the FSM acceleration model, resulting in a challenging controller design and a limited improvement. To optimize the acceleration feedback framework in the FSM system, different from the cascade AFC, the accelerometers are used to construct DOB to compensate for the platform vibrations directly. The acceleration nested loop can be plugged into the velocity loop without changing the system stability, and the controller design is quite simple. A series of comparative experimental results demonstrate that the disturbance rejection property of the CCD-based FSM can be effectively improved by the proposed approach.

Method for pulse control in a laser including a stimulated brillouin scattering mirror system

DOEpatents

Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.

2007-10-23

A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.

Stimulated Brillouin scattering mirror system, high power laser and laser peening method and system using same

DOEpatents

Dane, C Brent [Livermore, CA; Hackel, Lloyd [Livermore, CA; Harris, Fritz B [Rocklin, CA

2007-04-24

A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.

Comparison of detection limit in fiber-based conventional, amplified, and gain-clamped cavity ring-down techniques

NASA Astrophysics Data System (ADS)

Sharma, K.; Abdul Khudus, M. I. M.; Alam, S. U.; Bhattacharya, S.; Venkitesh, D.; Brambilla, G.

2018-01-01

Relative performance and detection limit of conventional, amplified, and gain-clamped cavity ring-down techniques (CRDT) in all-fiber configurations are compared experimentally for the first time. Refractive index measurement using evanescent field in tapered fibers is used as a benchmark for the comparison. The systematic optimization of a nested-loop configuration in gain-clamped CRDT is also discussed, which is crucial for achieving a constant gain in a CRDT experiment. It is found that even though conventional CRDT has the lowest standard error in ring-down time (Δτ), the value of ring-down time (τ) is very small, thus leading to poor detection limit. Amplified CRDT provides an improvement in τ, albeit with two orders of magnitude higher Δτ due to amplifier noise. The nested-loop configuration in gain-clamped CRDT helps in reducing Δτ by an order of magnitude as compared to amplified CRDT whilst retaining the improvement in τ. A detection limit of 1 . 03 × 10-4 RIU at refractive index of 1.322 with a 3 mm long and 4.5 μm diameter tapered fiber is demonstrated with the gain-clamped CRDT.

Experiments and analysis of tunable monolithic 1- μm single-frequency fiber lasers with loop mirror filters

NASA Astrophysics Data System (ADS)

Wang, Qi; Song, Huaqing; Wang, Xingpeng; Wang, Dongdong; Li, Li

2018-03-01

In this paper, we demonstrated thermally tunable 1- μm single-frequency fiber lasers utilizing loop mirror filters (LMFs) with unpumped Yb-doped fibers. The frequency selection and tracking was achieved by combining a fiber Bragg grating (FBG) and a dynamic grating established inside the LMF. The central emission wavelength was at 1064.07 nm with a tuning range of 1.4 nm, and the measured emission linewidth was less than 10 kHz. We also systematically studied the wavelength-tracking thermal stability of the LMF with separate thermal treatment upon the FBG and LMF, respectively. Finally, we presented a selection criterion for the minimum unpumped doped fiber length inside the LMF with experimental verification.

Ignition feedback regenerative free electron laser (FEL) amplifier

DOEpatents

Kim, Kwang-Je; Zholents, Alexander; Zolotorev, Max

2001-01-01

An ignition feedback regenerative amplifier consists of an injector, a linear accelerator with energy recovery, and a high-gain free electron laser amplifier. A fraction of the free electron laser output is coupled to the input to operate the free electron laser in the regenerative mode. A mode filter in this loop prevents run away instability. Another fraction of the output, after suitable frequency up conversion, is used to drive the photocathode. An external laser is provided to start up both the amplifier and the injector, thus igniting the system.

Removing left-right asymmetry in a Sagnac interferometer applied to cancel its reflectance dependence on birefringence.

PubMed

Golub, Ilya; Exir, Hourieh

2013-05-01

We present a left-right symmetry restoring method, which removes the detrimental birefringence in the single-mode fiber Sagnac interferometer, achieved with the aid of a half waveplate oriented at a specific angle. We show theoretically and demonstrate experimentally that adding a π-shift between clockwise and counterclockwise propagating, horizontally (in fiber loop plane) polarized field components, the Sagnac loop mirror's reflection becomes independent on birefringence of an element placed in the loop.

Performance Evaluation of Photonic Sigma Delta ADCs

DTIC Science & Technology

2010-12-01

resulted in an output at the MZI driver that is too low to drive the MZI itself. It is recommended that a transimpedance amplifier be used instead of...Accumulator The accumulator shown in Figure 1 consists of a single delay, a feedback loop and two amplifiers . The input of the accumulator is the...fiber amplifier (EDFA), an output coupler, an electro–optic modulator, a tunable filter and the fiber that connects these devices together. The piezo

A low-voltage sense amplifier with two-stage operational amplifier clamping for flash memory

NASA Astrophysics Data System (ADS)

Guo, Jiarong

2017-04-01

A low-voltage sense amplifier with reference current generator utilizing two-stage operational amplifier clamp structure for flash memory is presented in this paper, capable of operating with minimum supply voltage at 1 V. A new reference current generation circuit composed of a reference cell and a two-stage operational amplifier clamping the drain pole of the reference cell is used to generate the reference current, which avoids the threshold limitation caused by current mirror transistor in the traditional sense amplifier. A novel reference voltage generation circuit using dummy bit-line structure without pull-down current is also adopted, which not only improves the sense window enhancing read precision but also saves power consumption. The sense amplifier was implemented in a flash realized in 90 nm flash technology. Experimental results show the access time is 14.7 ns with power supply of 1.2 V and slow corner at 125 °C. Project supported by the National Natural Science Fundation of China (No. 61376028).

Evaluation of microfabricated deformable mirror systems

NASA Astrophysics Data System (ADS)

Cowan, William D.; Lee, Max K.; Bright, Victor M.; Welsh, Byron M.

1998-09-01

This paper presents recent result for aberration correction and beam steering experiments using polysilicon surface micromachined piston micromirror arrays. Microfabricated deformable mirrors offer a substantial cost reduction for adaptive optic systems. In addition to the reduced mirror cost, microfabricated mirrors typically require low control voltages, thus eliminating high voltage amplifiers. The greatly reduced cost per channel of adaptive optic systems employing microfabricated deformable mirrors promise high order aberration correction at low cost. Arrays of piston micromirrors with 128 active elements were tested. Mirror elements are on a 203 micrometers 12 by 12 square grid. The overall array size is 2.4 mm square. The arrays were fabricated in the commercially available DARPA supported MUMPs surface micromachining foundry process. The cost per mirror array in this prototyping process is less than 200 dollars. Experimental results are presented for a hybrid correcting element comprised of a lenslet array and piston micromirror array, and for a piston micromirror array only. Also presented is a novel digital deflection micromirror which requires no digital to analog converters, further reducing the cost of adaptive optics system.

Integrated P-channel MOS gyrator

NASA Technical Reports Server (NTRS)

Hochmair, E. S. (Inventor)

1974-01-01

A gyrator circuit is described which is of the conventional configuration of two amplifiers in a circular loop, one producing zero phase shift and the other producing 180 phase reversal, in a circuit having medium Q composed of all field effect transistors of the same conductivity type. The current source to each gyrator amplifier comprises an amplifier which responds to changes in current, with the amplified signals feed back so as to limit current. The feedback amplifier has a large capacitor connected to bypass high frequency components, thereby stabilizing the output. The design makes possible fabrication of circuits with transistors of only one conductivity type, providing economies in manufacture and use.

A 1microW 85nV/ radicalHz pseudo open-loop preamplifier with programmable band-pass filter for neural interface system.

PubMed

Chang, Sun-Il; Yoon, Euisik

2009-01-01

We report an energy efficient pseudo open-loop amplifier with programmable band-pass filter developed for neural interface systems. The proposed amplifier consumes 400nA at 2.5V power supply. The measured thermal noise level is 85nV/ radicalHz and input-referred noise is 1.69microV(rms) from 0.3Hz to 1 kHz. The amplifier has a noise efficiency factor of 2.43, the lowest in the differential topologies reported up to date to our knowledge. By programming the switched-capacitor frequency and bias current, we could control the bandwidth of the preamplifier from 138 mHz to 2.2 kHz to meet various application requirements. The entire preamplifier including band-pass filters has been realized in a small area of 0.043mm(2) using a 0.25microm CMOS technology.

Target-in-the-loop high-power adaptive phase-locked fiber laser array using single-frequency dithering technique

NASA Astrophysics Data System (ADS)

Tao, R.; Ma, Y.; Si, L.; Dong, X.; Zhou, P.; Liu, Z.

2011-11-01

We present a theoretical and experimental study of a target-in-the-loop (TIL) high-power adaptive phase-locked fiber laser array. The system configuration of the TIL adaptive phase-locked fiber laser array is introduced, and the fundamental theory for TIL based on the single-dithering technique is deduced for the first time. Two 10-W-level high-power fiber amplifiers are set up and adaptive phase locking of the two fiber amplifiers is accomplished successfully by implementing a single-dithering algorithm on a signal processor. The experimental results demonstrate that the optical phase noise for each beam channel can be effectively compensated by the TIL adaptive optics system under high-power applications and the fringe contrast on a remotely located extended target is advanced from 12% to 74% for the two 10-W-level fiber amplifiers.

Initial Performance of the Keck AO Wavefront Controller System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johansson, E M; Acton, D S; An, J R

2001-03-01

The wavefront controller for the Keck Observatory AO system consists of two separate real-time control loops: a tip-tilt control loop to remove tilt from the incoming wavefront, and a deformable mirror control loop to remove higher-order aberrations. In this paper, we describe these control loops and analyze their performance using diagnostic data acquired during the integration and testing of the AO system on the telescope. Disturbance rejection curves for the controllers are calculated from the experimental data and compared to theory. The residual wavefront errors due to control loop bandwidth are also calculated from the data, and possible improvements tomore » the controller performance are discussed.« less

Diffraction limited 1064nm monolithic DBR-master oscillator power amplifier with more than 7W output power

NASA Astrophysics Data System (ADS)

Zink, Christof; Maaβdorf, André; Fricke, Jörg; Ressel, Peter; Maiwald, Martin; Sumpf, Bernd; Erbert, Götz; Tränkle, Günther

2018-02-01

High brightness diode lasers with a spectrally narrowband emission, several watts of output power with an almost diffraction limited beam quality are requested light sources for several applications. In this work, a monolithic master oscillator power amplifier will be presented. The resonator of the master oscillator is formed by a high-reflection DBR grating on the rear side and an internal DBR mirror. Its power is amplified in a ridge waveguide followed by a tapered section. The monolithic MOPA provides over 7 W at 1064 nm with a narrow spectral emission width below 20 pm and an almost diffraction limited beam.

RF Single Electron Transistor Readout Amplifiers for Superconducting Astronomical Detectors for X-Ray to Sub-mm Wavelengths

NASA Technical Reports Server (NTRS)

Stevenson, Thomas; Aassime, Abdelhanin; Delsing, Per; Frunzio, Luigi; Li, Li-Qun; Prober, Daniel; Schoelkopf, Robert; Segall, Ken; Wilson, Chris; Stahle, Carl

2000-01-01

We report progress on using a new type of amplifier, the Radio-Frequency Single-Electron Transistor (RF-SET), to develop multi-channel sensor readout systems for fast and sensitive readout of high impedance cryogenic photodetectors such as Superconducting Tunnel Junctions and Single Quasiparticle Photon Counters. Although cryogenic, these detectors are desirable because of capabilities not other-wise attainable. However, high impedances and low output levels make low-noise, high-speed readouts challenging, and large format arrays would be facilitated by compact, low-power, on-chip integrated amplifiers. Well-suited for this application are RF-SETs, very high performance electrometers which use an rf readout technique to provide 100 MHz bandwidth. Small size, low power, and cryogenic operation allow direct integration with detectors, and using multiple rf carrier frequencies permits simultaneous readout of 20-50 amplifiers with a common electrical connection. We describe both the first 2-channel demonstration of this wavelength division multiplexing technique for RF-SETs, and Charge-Locked-Loop operation with 100 kHz of closed-loop bandwidth.

High-speed carrier-envelope phase drift detection of amplified laser pulses.

PubMed

Fordell, T; Miranda, M; Arnold, C L; L'Huillier, A

2011-11-21

An instrument for measuring carrier-envelope phase (CEP) drift of amplified femtosecond laser pulses at repetition rates up to the 100-kHz regime is presented. The device can be used for real-time pulse labeling and it could also enable single-loop CEP control of future high-repetition rate laser amplifiers. The scheme is demonstrated by measuring the CEP drift of a 1-kHz source. © 2011 Optical Society of America

Ways to suppress click and pop for class D amplifiers

NASA Astrophysics Data System (ADS)

Haishi, Wang; Bo, Zhang; Jiang, Sun

2012-08-01

Undesirable audio click and pop may be generated in a speaker or headphone. Compared to linear (class A/B/AB) amplifiers, class D amplifiers that comprise of an input stage and a modulation stage are more prone to producing click and pop. This article analyzes sources that generate click and pop in class D amplifiers, and corresponding ways to suppress them. For a class D amplifier with a single-ended input, click and pop is likely to be due to two factors. One is from a voltage difference (VDIF) between the voltage of an input capacitance (VCIN) and a reference voltage (VREF) of the input stage, and the other one is from the non-linear switching during the setting up of the bias and feedback voltages/currents (BFVC) of the modulation stage. In this article, a fast charging loop is introduced into the input stage to charge VCIN to roughly near VREF. Then a correction loop further charges or discharges VCIN, substantially equalizing it with VREF. Dummy switches are introduced into the modulation stage to provide switching signals for setting up BFVC, and the power switches are disabled until the BFVC are set up successfully. A two channel single-ended class D amplifier with the above features is fabricated with 0.5 μm Bi-CMOS process. Road test and fast Fourier transform analysis indicate that there is no noticeable click and pop.

Closed-Loop Adaptive Optics Control in Strong Atmospheric Turbulence

DTIC Science & Technology

2008-09-01

115 7.1.1 Kalman estimation of anisoplanatic Zernike tilt . . . . 115 7.1.2 An improved temporally phase-shifted design . . . . . 115 7.1.3...5 7. Shack-Hartmann lenslet diagram [40] . . . . . . . . . . . . . . . . . . 9 8. Determining phase tilt from a S-H WFS [8...wavefront prior to it encountering the WFS. In this system a non- deformable mirror known as a fast-steering mirror (FSM) corrects the tilt (average phase

Gain measurements and spatial coherence in neon-like x-ray lasers

NASA Astrophysics Data System (ADS)

Krishnan, J.; Cairns, C.; Dwivedi, L.; Holden, M.; Key, M. H.; Lewis, C. L. S.; MacPhee, A.; Neely, D.; Norreys, P. A.; Pert, G. J.; Ramsden, S. A.; Smith, C. G.; Tallents, G. J.; Zhang, J.

1995-05-01

Many of the applications with x-ray lasers require high quality output radiation with properties such as short wavelength and a high degree of coherence (longitudinal and spatial). Ne-like Yttrium (Z=39) is potentially a bright and monochromatic XUV lasing medium. The output at 15.5 nm is monochromatic due to the overlap of the J=2-1 and J=0-1 lines. A gain coefficient of 3±1 was obtained at 15.5 nm by irradiating 100 μm wide yttrium stripes at 6×1013 W/cm2 with 1.06 μm, 650 ps pulses from the Rutherford Appleton Laboratory VULCAN laser. We have investigated improving x-ray laser spatial coherence utilizing a series of amplifiers instead of the standard double target configuration. An ``injector-amplifier'' scheme was successfully demonstrated with the Ne-like Ge x-ray laser. A spatially small and coherent part of the 23 nm beam from the standard double target geometry has been relayed using a W/Si multilayer mirror onto a single or double target configuration situated at a distance of ˜1.5 m from the mirror and pumped by two 150 mm diameter beams of VULCAN laser. A beam ``foot-print monitor'' was employed with a flat mirror to relay 23 nm output onto a film pack to record the spatial variation of the x-ray laser beam. Analyzing the fringes obtained through a cross-wire placed in front of the beam shows that an increase in spatial coherence was achieved by adding amplifiers to the x-ray laser beam line.

Three-beam coherent combination experiments based on segmented mirrors and measure of phase characteristics of beams passing through Yb-doped fiber amplifier

NASA Astrophysics Data System (ADS)

Yang, Ping; Yang, Ruo fu; Shen, Feng; Ao, Mingwu; Jiang, Wenhan

2009-05-01

Coherent combination is one of the most promising ways to realize high power laser output. A three- laser-beam coherent combination system based on adaptive optics (AO) technique has been set up in our laboratory. In this system, three 1064nm laser beams are placed side-by-side and compressed by two reflective mirrors. An active segmented deformable mirror (DM) is used to compensate the optical path difference (OPD) among three laser beams. The beams are overlapped onto a 2900Hz CCD camera to form an interference pattern while the peak intensity of the interference pattern is taken as the cost function to optimize by a stochastic parallel gradient descent (SPGD) algorithm. SPGD algorithm is realized on a RT-Linux dual-core industrial computer. A series of experiments have been accomplished and experimental results show that both static distorted aberrations in the beams and active distorted aberrations (which are brought in by a hot iron and the frequency is about 5Hz) can be compensated successfully when the gain coefficients and the perturbation amplitude of SPGD are chosed appropriately, thereby three beams can be well combined. For controlling the phase of fiber lasers, the phase characteristics of beams passing through Yb-doped dual-clad fiber amplifier are measured by means of investigating the interference pattern under different output power through experiments. The frequency of phase fluctuation is evaluated through analyzing the fluctuation of power within a 90um aperture of far-field focal spot. Experimental results show that the phase fluctuation frequencies of laser beam transmitted through fiber amplifier are mainly in the range of 100~1500Hz. As a result, to control the phase fluctuation of beams passing through fiber amplifier, the bandwidth of any potential phase control scheme must be greater than 1.5 kilohertz.

DISTRIBUTED AMPLIFIER INCORPORATING FEEDBACK

DOEpatents

Bell, P.R. Jr.

1958-10-21

An improved distributed amplifier system employing feedback for stabilization is presented. In accordance with the disclosed invention, a signal to be amplified is applled to one end of a suitable terminated grid transmission line. At intervals along the transmission line, the signal is fed to stable, resistance-capacitance coupled amplifiers incorporating feedback loops therein. The output current from each amplifier is passed through an additional tube to minimize the electrostatic capacitance between the tube elements of the last stage of the amplifier, and fed to appropriate points on an output transmission line, similar to the grid line, but terminated at the opposite (input) end. The output taken from the unterminated end of the plate transmission line is proportional to the input voltage impressed upon the grid line.

Coma of modified Gregorian and Cassegrainian mirror systems

NASA Technical Reports Server (NTRS)

Jones, R. T.

1976-01-01

The equivalence of the classical Newtonian, Cassegrainian, and Gregorian mirror systems with respect to the first two Seidel aberrations is rederived by means of a simple congruence. The effects of arbitrary small modifications of the two mirror systems are then studied and general formulas are derived for the effects of such modifications on the spherical aberration and coma. Spherical aberration is corrected to the third order if the amount of glass removed from one surface is replaced at the corresponding zone of the other surface. Modifications in which one surface is made spherical while the other is adjusted to eliminate spherical aberration result in large increases of coma for systems having the usual amplifying ratios.

Fast terahertz imaging using a quantum cascade amplifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Yuan, E-mail: yr235@cam.ac.uk; Wallis, Robert; Jessop, David Stephen

2015-07-06

A terahertz (THz) imaging scheme based on the effect of self-mixing in a 2.9 THz quantum cascade (QC) amplifier has been demonstrated. By coupling an antireflective-coated silicon lens to the facet of a QC laser, with no external optical feedback, the laser mirror losses are enhanced to fully suppress lasing action, creating a THz QC amplifier. The addition of reflection from an external target to the amplifier creates enough optical feedback to initiate lasing action and the resulting emission enhances photon-assisted transport, which in turn reduces the voltage across the device. At the peak gain point, the maximum photon densitymore » coupled back leads to a prominent self-mixing effect in the QC amplifier, leading to a high sensitivity, with a signal to noise ratio up to 55 dB, along with a fast data acquisition speed of 20 000 points per second.« less

Characterization of a medium-sized washer-gun for an axisymmetric mirror

NASA Astrophysics Data System (ADS)

Yi, Hongshen; Liu, Ming; Shi, Peiyun; Yang, Zhida; Zhu, Guanghui; Lu, Quanming; Sun, Xuan

2018-04-01

A new medium-sized washer gun is developed for a plasma start-up in a fully axisymmetric mirror. The gun is positioned at the east end of the Keda Mirror with AXisymmetricity facility and operated in the pulsed mode with an arc discharging time of 1.2 ms and a typical arc current of 8.5 kA with 1.5 kV discharge voltage. To optimize the operation, a systematic scan of the neutral pressure, the arc voltage, the bias voltage on a mesh grid 6 cm in front of the gun and an end electrode located on the west end of mirror, and the mirror ratio was performed. The streaming plasma was measured with triple probes in the three mirror cells and a diamagnetic loop in the central cell. Floating potential measurements suggest that the plasma could be divided into streaming and mirror-confined plasmas. The floating potential for the streaming plasma is negative, with an electric field pointing inwards. The mirror-confined plasma has a typical lifetime of 0.5 ms.

Characterization of a medium-sized washer-gun for an axisymmetric mirror.

PubMed

Yi, Hongshen; Liu, Ming; Shi, Peiyun; Yang, Zhida; Zhu, Guanghui; Lu, Quanming; Sun, Xuan

2018-04-01

A new medium-sized washer gun is developed for a plasma start-up in a fully axisymmetric mirror. The gun is positioned at the east end of the Keda Mirror with AXisymmetricity facility and operated in the pulsed mode with an arc discharging time of 1.2 ms and a typical arc current of 8.5 kA with 1.5 kV discharge voltage. To optimize the operation, a systematic scan of the neutral pressure, the arc voltage, the bias voltage on a mesh grid 6 cm in front of the gun and an end electrode located on the west end of mirror, and the mirror ratio was performed. The streaming plasma was measured with triple probes in the three mirror cells and a diamagnetic loop in the central cell. Floating potential measurements suggest that the plasma could be divided into streaming and mirror-confined plasmas. The floating potential for the streaming plasma is negative, with an electric field pointing inwards. The mirror-confined plasma has a typical lifetime of 0.5 ms.

Enhancement of the transversal magnetic optic Kerr effect: Lock-in vs. hysteresis method.

PubMed

Hayek, Jorge Nicolás; Herreño-Fierro, César A; Patiño, Edgar J

2016-10-01

The lock-in amplifier is often used to study the enhancement of the magneto-optical Kerr effect (MOKE) in the presence of plasmon resonances. In the present work we show that it is possible to investigate such effect replacing the lock-in amplifier by a compensator, filter, and differential amplifier. This allows us to extract the full hysteresis loop in and out of the resonance without the need of a lock-in amplifier. Our results demonstrate these two setups are equivalent to study the enhancement of the transversal MOKE (T-MOKE) in magnetoplasmonic systems.

Preliminary design and development of a reflectance spectrometer instrument

NASA Technical Reports Server (NTRS)

Mccord, T. B.

1979-01-01

An improved design for the reflectance spectrometer is described to be used on various terrestrial body missions. These improvements were made on the original Lunar Polar Orbiter design. These include a larger entrance mirror, rectangular aperture, multiple optical beams, spatial resolution, and a bandwidth extension to 5 microns. In addition, detailed electronic designs were produced for a charge amplifier and an amplifier/demodulator/integrator. Design of a microprocessor driven test system was begun. Laboratory tests were performed on a tuning fork chopper.

Development of a novel loop-mediated isothermal amplification (LAMP) assay for the detection of Salmonella ser. Enteritidis from egg products

USDA-ARS?s Scientific Manuscript database

Salmonella ser. Enteritidis is a major public health concern worldwide. Loop-mediated isothermal amplification (LAMP) is a novel simple, easy-to-operate detection technology that amplifies DNA with high speed, efficiency, and specificity under isothermal conditions. The objective of this study was t...

Reflex ring laser amplifier system

DOEpatents

Summers, M.A.

1983-08-31

The invention is a method and apparatus for providing a reflex ring laser system for amplifying an input laser pulse. The invention is particularly useful in laser fusion experiments where efficient production of high-energy and high power laser pulses is required. The invention comprises a large aperture laser amplifier in an unstable ring resonator which includes a combination spatial filter and beam expander having a magnification greater than unity. An input pulse is injected into the resonator, e.g., through an aperture in an input mirror. The injected pulse passes through the amplifier and spatial filter/expander components on each pass around the ring. The unstable resonator is designed to permit only a predetermined number of passes before the amplified pulse exits the resonator. On the first pass through the amplifier, the beam fills only a small central region of the gain medium. On each successive pass, the beam has been expanded to fill the next concentric non-overlapping region of the gain medium.

Bidirectional amplifier

DOEpatents

Wright, James T.

1986-01-01

A bilateral circuit is operable for transmitting signals in two directions without generation of ringing due to feedback caused by the insertion of the circuit. The circuit may include gain for each of the signals to provide a bidirectional amplifier. The signals are passed through two separate paths, with a unidirectional amplifier in each path. A controlled sampling device is provided in each path for sampling the two signals. Any feedback loop between the two signals is disrupted by providing a phase displacement between the control signals for the two sampling devices.

Bidirectional amplifier

DOEpatents

Wright, J.T.

1984-02-02

A bilateral circuit is operable for transmitting signals in two directions without generation of ringing due to feedback caused by the insertion of the circuit. The circuit may include gain for each of the signals to provide a bidirectional amplifier. The signals are passed through two separate paths, with a unidirectional amplifier in each path. A controlled sampling device is provided in each path for sampling the two signals. Any feedback loop between the two signals is disrupted by providing a phase displacement between the control signals for the two sampling devices.

Observation of laser formation inside a laser cavity containing a phase conjugate mirror

NASA Astrophysics Data System (ADS)

Wu, Frank F.

2012-03-01

Adaptive optics (AO) systems are used to compensate atmospheric perturbations on a propagating laser beam. However, AO needs a beacon to obtain the phase information. This paper presents a possible formation of beacon in target-in-theloop (TIL) geometry which is analog to a laser cavity. The TIL laser cavity is formed with a high reflectivity mirror on one end and an optical phase conjugate mirror as the second mirror. The TIL laser is initialized by a single frequency 10 ns Q-switched laser pulse. This is very similar to how an injection seeding or regenerative amplifier scheme starts a laser oscillation. With a cavity length of around 11 meters and an initial laser pulse of 10 ns, we have been able to isolate laser field images related to each round-trip pulse. Furthermore, by replacing the first mirror with a rough-surface target to simulate an uncooperative target and adding phase distortion elements to simulate atmospheric effects, we can observe the image status under such conditions.

Advances in optical structure systems; Proceedings of the Meeting, Orlando, FL, Apr. 16-19, 1990

NASA Astrophysics Data System (ADS)

Breakwell, John; Genberg, Victor L.; Krumweide, Gary C.

Various papers on advances in optical structure systems are presented. Individual topics addressed include: beam pathlength optimization, thermal stress in glass/metal bond with PR 1578 adhesive, structural and optical properties for typical solid mirror shapes, parametric study of spinning polygon mirror deformations, simulation of small structures-optics-controls system, spatial PSDs of optical structures due to random vibration, mountings for a four-meter glass mirror, fast-steering mirrors in optical control systems, adaptive state estimation for control of flexible structures, surface control techniques for large segmented mirrors, two-time-scale control designs for large flexible structures, closed-loop dynamic shape control of a flexible beam. Also discussed are: inertially referenced pointing for body-fixed payloads, sensor blending line-of-sight stabilization, controls/optics/structures simulation development, transfer functions for piezoelectric control of a flexible beam, active control experiments for large-optics vibration alleviation, composite structures for a large-optical test bed, graphite/epoxy composite mirror for beam-steering applications, composite structures for optical-mirror applications, thin carbon-fiber prepregs for dimensionally critical structures.

Dynamical simulation of E-ELT segmented primary mirror

NASA Astrophysics Data System (ADS)

Sedghi, B.; Muller, M.; Bauvir, B.

2011-09-01

The dynamical behavior of the primary mirror (M1) has an important impact on the control of the segments and the performance of the telescope. Control of large segmented mirrors with a large number of actuators and sensors and multiple control loops in real life is a challenging problem. In virtual life, modeling, simulation and analysis of the M1 bears similar difficulties and challenges. In order to capture the dynamics of the segment subunits (high frequency modes) and the telescope back structure (low frequency modes), high order dynamical models with a very large number of inputs and outputs need to be simulated. In this paper, different approaches for dynamical modeling and simulation of the M1 segmented mirror subject to various perturbations, e.g. sensor noise, wind load, vibrations, earthquake are presented.

A 15 W 1152 nm Raman fiber laser with 6 nm spectral width for Ho3+-doped crystal's pumping source

NASA Astrophysics Data System (ADS)

Chen, Xiuyan; Jiang, Huawei

2016-12-01

A 11.5 W 1152 nm Raman fiber laser with 6 nm spectral width was demonstrated based on the resonator constructed with one fiber loop mirror and one fiber Bragg grating. By mans of experimental measurement and theoretical calculation, the reflectivity of the fiber loop mirror was confirmed as 0.93. The Yb3+-doped 1090 nm fiber length was about 5 m. When the maximum pumping power of 976 nm laser was 54.8 W, 32.2 W 1090 nm laser was obtained and the optical to optical conversion efficiency from 1090 nm to 1152 nm light was 48%. Finally, the 1152 nm Raman fiber laser was used for pumping Ho3+:LLF crystal, and the 1194 nm fluorescence emission peak was detected for the first time.

The Multidisk Diode-Pumped High Power Yb:YAG Laser Amplifier of High-Intensity Laser System with 1 kHz Repetition Rate

NASA Astrophysics Data System (ADS)

Kuptsov, G. V.; Petrov, V. V.; Petrov, V. A.; Laptev, A. V.; Kirpichnikov, A. V.; Pestryakov, E. V.

2018-04-01

The source of instabilities in the multidisk diode-pumped high power Yb:YAG laser amplifier with cryogenic closed-loop cooling in the laser amplification channel of the high-intensity laser system with 1 kHz repetition rate was determined. Dissected copper mounts were designed and used to suppress instabilities and to achieve repeatability of the system. The equilibrium temperature dependency of the active elements on average power was measured. The seed laser for the multidisk amplifier was numerically simulated and designed to allow one to increase pulses output energy after the amplifier up to 500 mJ.

REVIEWS OF TOPICAL PROBLEMS: Coronal magnetic loops

NASA Astrophysics Data System (ADS)

Zaitsev, Valerii V.; Stepanov, Alexander V.

2008-11-01

The goal of this review is to outline some new ideas in the physics of coronal magnetic loops, the fundamental structural elements of the atmospheres of the Sun and flaring stars, which are involved in phenomena such as stellar coronal heating, flare energy release, charged particle acceleration, and the modulation of optical, radio, and X-ray emissions. The Alfvén-Carlqvist view of a coronal loop as an equivalent electric circuit allows a good physical understanding of loop processes. Describing coronal loops as MHD-resonators explains various ways in which flaring emissions from the Sun and stars are modulated, whereas modeling them by magnetic mirror traps allows one to describe the dynamics and emission of high-energy particles. Based on these approaches, loop plasma and fast particle parameters are obtained and models for flare energy release and stellar corona heating are developed.

First pulse effect self-suppression picosecond regenerative amplifier (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fan, Haitao; Chang, Liang; Zhang, Yi; Yao, Siyi; Lu, Wei; Yang, Xiaohong

2017-03-01

First pulse effect, commonly seen in nanosecond cavity-dumped lasers and picosecond regenerative amplifiers, not only leads to degradation of processing quality, but also acts as potential threat to optical switching elements. Several methods have been developed to suppress that effect, including electronic controls, polarization controls, and diffraction controls. We present a new way for first pulse self-suppression without any additional components. By carefully arranging the cavity mirror of a regenerative amplifier, we realized `parasitic lasing like' radiation. When the regenerative amplifier works in `operation ready' status, the parasitic lasing occurs and prevents the gain crystal from saturation. When the regenerative amplifier starts working and amplifying pulses, the first pulse in a pulse train will not get much more gain and energy than pulses following it. As parasitic lasing disappears at the same time, the average output power of the amplifier does not significantly reduce. This cost effective method does not require any additional component. In addition, as it is not polarization dependent, this method is widely suitable for different kinds of regenerative amplifiers. It's the easiest and cheapest way to suppress first pulse effect, to the best of our knowledge.

Optical interferometer testbed

NASA Technical Reports Server (NTRS)

Blackwood, Gary H.

1991-01-01

Viewgraphs on optical interferometer testbed presented at the MIT Space Research Engineering Center 3rd Annual Symposium are included. Topics covered include: space-based optical interferometer; optical metrology; sensors and actuators; real time control hardware; controlled structures technology (CST) design methodology; identification for MIMO control; FEM/ID correlation for the naked truss; disturbance modeling; disturbance source implementation; structure design: passive damping; low authority control; active isolation of lightweight mirrors on flexible structures; open loop transfer function of mirror; and global/high authority control.

A tip/tilt mirror with large dynamic range for the ESO VLT Four Laser Guide Star Facility

NASA Astrophysics Data System (ADS)

Rijnveld, N.; Henselmans, R.; Nijland, B.

2011-09-01

One of the critical elements in the Four Laser Guide Star Facility (4LGSF) for the ESO Very Large Telescope (VLT) is the Optical Tube Assembly (OTA), consisting of a stable 20x laser beam expander and an active tip/tilt mirror, the Field Selector Mechanism (FSM). This paper describes the design and performance testing of the FSM. The driving requirement for the FSM is its large stroke of +/-6.1 mrad, in combination with less than 1.5 μrad RMS absolute accuracy. The FSM design consists of a Zerodur mirror, bonded to a membrane spring and strut combination to allow only tip and tilt. Two spindle drives actuate the mirror, using a stiffness based transmission to increase resolution. Absolute accuracy is achieved with two differential inductive sensor pairs. A prototype of the FSM is realized to optimize the control configuration and measure its performance. Friction in the spindle drive is overcome by creating a local velocity control loop between the spindle drives and the shaft encoders. Accuracy is achieved by using a cascaded low bandwidth control loop with feedback from the inductive sensors. The pointing jitter and settling time of the FSM are measured with an autocollimator. The system performance meets the strict requirements, and is ready to be implemented in the first OTA.

Sensitivity enhancement of remotely coupled NMR detectors using wirelessly powered parametric amplification.

PubMed

Qian, Chunqi; Murphy-Boesch, Joseph; Dodd, Stephen; Koretsky, Alan

2012-09-01

A completely wireless detection coil with an integrated parametric amplifier has been constructed to provide local amplification and transmission of MR signals. The sample coil is one element of a parametric amplifier using a zero-bias diode that mixes the weak MR signal with a strong pump signal that is obtained from an inductively coupled external loop. The NMR sample coil develops current gain via reduction in the effective coil resistance. Higher gain can be obtained by adjusting the level of the pumping power closer to the oscillation threshold, but the gain is ultimately constrained by the bandwidth requirement of MRI experiments. A feasibility study here shows that on a NaCl/D(2) O phantom, (23) Na signals with 20 dB of gain can be readily obtained with a concomitant bandwidth of 144 kHz. This gain is high enough that the integrated coil with parametric amplifier, which is coupled inductively to external loops, can provide sensitivity approaching that of direct wire connection. Copyright © 2012 Wiley Periodicals, Inc.

Electronic control of different generation regimes in mode-locked all-fibre F8 laser

NASA Astrophysics Data System (ADS)

Kobtsev, Sergey; Ivanenko, Aleksey; Kokhanovskiy, Alexey; Smirnov, Sergey

2018-04-01

We demonstrate for the first time an electronically controlled realisation of markedly different generation regimes in a mode-locked all-fibre figure-eight (F8) Yb-doped laser. Electronic adjustment of the ratio of pumping powers of two amplification stages in a nonlinear amplifying loop mirror enables the establishment of stable pulse generation regimes with different degrees of coherence and control over their parameters within relatively broad limits, with the pulse duration range exceeding a factor of two in the picosecond domain for coherent and incoherent pulses, the energy range exceeding an order of magnitude for incoherent pulses (2.2-24.8 nJ) and over a factor of 8 for coherent pulses (1.9-16.2 nJ). Adjustment of the pumping powers allows one to maintain the duration of the coherent pulses and to set their peak power in the range of 32.5-292.5 W. The proposed configuration of electronic control over the radiation parameters of a mode-locked all-fibre F8 laser enables reproducible generation of pulses of different types with specified parameters within a broad range of values.

Novel techniques for optical performance monitoring in optical systems

NASA Astrophysics Data System (ADS)

Ku, Yuen Ching

The tremendous increase of data traffic in the worldwide Internet has driven the rapid development of optical networks to migrate from numerous point-to-point links towards meshed, transparent optical networks with dynamically routed light paths. This increases the need for appropriate network supervision methods. In view of this, optical performance monitoring (OPM) has emerged as an indispensable element for the quality assurance of an optical network. This thesis is devoted to the proposal of several new and accurate techniques to monitor different optical impairments so as to enhance proper network management. When the optical signal is carried on fiber links with optical amplifiers, the accumulated amplified spontaneous emission (ASE) noise will result in erroneous detection of the received signals. The first part of the thesis presents a novel, simple, and robust in-band optical signal to noise ratio (OSNR) monitoring technique using phase modulator embedded fiber loop mirror (PM-FLM). This technique measures the in-band OSNR accurately by observing the output power of a fiber loop mirror filter, where the transmittance is adjusted by an embedded phase modulator driven by a low-frequency periodic signal. The robustness against polarization mode dispersion, chromatic dispersion, bit-rate, and partially polarized noise is experimentally demonstrated. Chromatic dispersion (CD) is due to the fact that light with different frequencies travel at different speeds inside fiber. It causes pulse spreading and intersymbol interference (ISI) which would severely degrade the transmission performance. By feeding a signal into a fiber loop which consists of a high-birefringence (Hi-Bi) fiber, we experimentally show that the amount of experienced dispersion can be deduced from the RF power at a specific selected frequency which is determined by the length of the Hi-Bi fiber. Experimental results show that this technique can provide high monitoring resolution and dynamic range. Polarization mode dispersion (PMD) splits an optical pulse into two orthogonally polarized pulses traveling along the fiber at different speeds, causing crosstalk and ISI. The third part of the thesis demonstrates two different PMD monitoring schemes. The first one is based on the analysis of frequency-resolved state-of-polarization (SOP) rotation, with signal spectrum broadened by self-phase modulation (SPM) effect. Experimental results show that the use of broadened signal spectrum induced by SPM not only relaxes the filter requirement and reduces the computational complexity, but also improves the estimation accuracy, and extends the monitoring range of the pulsewidth. The second one is based on the delay-tap asynchronous waveform sampling technique. By examining the statistical distribution of the measured scatter plot, unambiguous PMD measurement range up to 50% of signal bit-period is demonstrated. The final part of the thesis focuses on the monitoring of alignment status between the pulse carver and data modulator in an optical system. We again employ the two-tap asynchronous sampling technique to perform such kind of monitoring in RZ-OOK transmission system. Experimental results show that both the misalignment direction and magnitude can be successfully determined. Besides, we propose and experimentally demonstrate the use of off-center optical filtering technique to capture the amount of spectrum broadening induced by the misalignment between the pulse-carver and the data modulator in RZ-DPSK transmission system. The same technique was also applied to monitor the synchronization between the old and the new data in synchronized phase re-modulation (SPRM) system.

Fully Integrated Biopotential Acquisition Analog Front-End IC

PubMed Central

Song, Haryong; Park, Yunjong; Kim, Hyungseup; Ko, Hyoungho

2015-01-01

A biopotential acquisition analog front-end (AFE) integrated circuit (IC) is presented. The biopotential AFE includes a capacitively coupled chopper instrumentation amplifier (CCIA) to achieve low input referred noise (IRN) and to block unwanted DC potential signals. A DC servo loop (DSL) is designed to minimize the offset voltage in the chopper amplifier and low frequency respiration artifacts. An AC coupled ripple rejection loop (RRL) is employed to reduce ripple due to chopper stabilization. A capacitive impedance boosting loop (CIBL) is designed to enhance the input impedance and common mode rejection ratio (CMRR) without additional power consumption, even under an external electrode mismatch. The AFE IC consists of two-stage CCIA that include three compensation loops (DSL, RRL, and CIBL) at each CCIA stage. The biopotential AFE is fabricated using a 0.18 µm one polysilicon and six metal layers (1P6M) complementary metal oxide semiconductor (CMOS) process. The core chip size of the AFE without input/output (I/O) pads is 10.5 mm2. A fourth-order band-pass filter (BPF) with a pass-band in the band-width from 1 Hz to 100 Hz was integrated to attenuate unwanted signal and noise. The overall gain and band-width are reconfigurable by using programmable capacitors. The IRN is measured to be 0.94 µVRMS in the pass band. The maximum amplifying gain of the pass-band was measured as 71.9 dB. The CIBL enhances the CMRR from 57.9 dB to 67 dB at 60 Hz under electrode mismatch conditions. PMID:26437404

Status of E-ELT M5 scale-one demonstrator

NASA Astrophysics Data System (ADS)

Barriga, Pablo; Sedghi, Babak; Dimmler, Martin; Kornweibel, Nick

2014-07-01

The fifth mirror of the European Extremely Large Telescope optical train is a field stabilization tip/tilt unit responsible for correcting the dynamical tip and tilt caused mainly by wind load on the telescope. A scale-one prototype including the inclined support, the fixed frame and a basic control system was designed and manufactured by NTE-SENER (Spain) and CSEM (Switzerland) as part of the prototyping and design activities. All interfaces to the mirror have been reproduced on a dummy structure reproducing the inertial characteristics of the optical element. The M5 unit is required to have sufficient bandwidth for tip/tilt reference commands coming from the wavefront control system. Such a bandwidth can be achieved using local active damping loop to damp the low frequency mechanical modes before closing a position loop. Prototyping on the M5 unit has been undertaken in order to demonstrate the E-ELT control system architecture, concepts and development standards and to further study active damping strategies. The control system consists of two nested loops: a local damping loop and a position loop. The development of this control system was undertaken following the E-ELT control system development standards in order to determine their applicability and performance and includes hardware selection, communication, synchronization, configuration, and data logging. In this paper we present the current status of the prototype M5 control system and the latest results on the active damping control strategy, in particular the promising results obtained with the method of positive position feedback.

Neural Networks For Demodulation Of Phase-Modulated Signals

NASA Technical Reports Server (NTRS)

Altes, Richard A.

1995-01-01

Hopfield neural networks proposed for demodulating quadrature phase-shift-keyed (QPSK) signals carrying digital information. Networks solve nonlinear integral equations prior demodulation circuits cannot solve. Consists of set of N operational amplifiers connected in parallel, with weighted feedback from output terminal of each amplifier to input terminals of other amplifiers. Used to solve signal processing problems. Implemented as analog very-large-scale integrated circuit that achieves rapid convergence. Alternatively, implemented as digital simulation of such circuit. Also used to improve phase estimation performance over that of phase-locked loop.

Cryogenic transimpedance amplifier for micromechanical capacitive sensors.

PubMed

Antonio, D; Pastoriza, H; Julián, P; Mandolesi, P

2008-08-01

We developed a cryogenic transimpedance amplifier that works at a broad range of temperatures, from room temperature down to 4 K. The device was realized with a standard complementary metal oxide semiconductor 1.5 mum process. Measurements of current-voltage characteristics, open-loop gain, input referred noise current, and power consumption are presented as a function of temperature. The transimpedance amplifier has been successfully applied to sense the motion of a polysilicon micromechanical oscillator at low temperatures. The whole device is intended to serve as a magnetometer for microscopic superconducting samples.

Erbium-doped fiber amplifier elements for structural analysis sensors

NASA Technical Reports Server (NTRS)

Hanna-Hawver, P.; Kamdar, K. D.; Mehta, S.; Nagarajan, S.; Nasta, M. H.; Claus, R. O.

1992-01-01

The use of erbium-doped fiber amplifiers (EDFA's) in optical fiber sensor systems for structural analysis is described. EDFA's were developed for primary applications as periodic regenerator amplifiers in long-distance fiber-based communication systems. Their in-line amplification performance also makes them attractive for optical fiber sensor systems which require long effective lengths or the synthesis of special length-dependent signal processing functions. Sensor geometries incorporating EDFA's in recirculating and multiple loop sensors are discussed. Noise and polarization birefringence are also considered, and the experimental development of system components is discussed.

Study of IEMP Effects on IC Operational Amplifier Circuits

DTIC Science & Technology

1975-12-10

plasma focus to study their IEMP responses with and without superposition of TREE responses. The 30-kJ plasma focus device produced photons primarily in the 8- to 100-keV range with pulse widths typically in the range of 10 to 15 nsec. Pulses of electrons were also deposited on the external leads of the operational amplifiers to determine the characteristic responses. These units were operated in circuits with closed-loop gains ranging from 5 to 100. During direct irradiation of the operational amplifiers, it was found that the IEMP responses (caused

Energy flow of electric dipole radiation in between parallel mirrors

NASA Astrophysics Data System (ADS)

Xu, Zhangjin; Arnoldus, Henk F.

2017-11-01

We have studied the energy flow patterns of the radiation emitted by an electric dipole located in between parallel mirrors. It appears that the field lines of the Poynting vector (the flow lines of energy) can have very intricate structures, including many singularities and vortices. The flow line patterns depend on the distance between the mirrors, the distance of the dipole to one of the mirrors and the angle of oscillation of the dipole moment with respect to the normal of the mirror surfaces. Already for the simplest case of a dipole moment oscillating perpendicular to the mirrors, singularities appear at regular intervals along the direction of propagation (parallel to the mirrors). For a parallel dipole, vortices appear in the neighbourhood of the dipole. For a dipole oscillating under a finite angle with the surface normal, the radiating tends to swirl around the dipole before travelling off parallel to the mirrors. For relatively large mirror separations, vortices appear in the pattern. When the dipole is off-centred with respect to the midway point between the mirrors, the flow line structure becomes even more complicated, with numerous vortices in the pattern, and tiny loops near the dipole. We have also investigated the locations of the vortices and singularities, and these can be found without any specific knowledge about the flow lines. This provides an independent means of studying the propagation of dipole radiation between mirrors.

Kerr hysteresis loop tracer with alternate driving magnetic field up to 10 kHz

NASA Astrophysics Data System (ADS)

Callegaro, Luca; Fiorini, Carlo; Triggiani, Giacomo; Puppin, Ezio

1997-07-01

A magneto-optical Kerr loop tracer for hysteresis loop measurements in thin films with field excitation frequency f0 from 10 mHz to 10 kHz is described. A very high sensitivity is obtained by using an ultrabright light-emitting diode as a low-noise light source and a novel acquisition process. The field is generated with a coil driven by an audio amplifier connected to a free-running oscillator. The conditioned detector output constitutes the magnetization signal (M); the magnetic field (H) is measured with a fast Hall probe. The acquisition electronics are based on a set of sample-and-hold amplifiers which allow the simultaneous sampling of M, H, and dH/dt. Acquisition is driven by a personal computer equipped with a multifunction I/O board. Test results on a 120 nm Fe film on Si substrate are shown. The coercive field of the film increases with frequency and nearly doubles at 10 kHz with respect to dc.

Genetic distance of Malaysian mousedeer based on mitochondrial DNA cytochrome oxidase I (COI) and D-loop region sequences

NASA Astrophysics Data System (ADS)

Bakar, Mohamad-Azam Akmal Abu; Rovie-Ryan, Jeffrine Japning; Ampeng, Ahmad; Yaakop, Salmah; Nor, Shukor Md; Md-Zain, Badrul Munir

2018-04-01

Mousedeer is one of the primitive mammals that can be found mainly in Southeast-Asia region. There are two species of mousedeer in Malaysia which are Tragulus kanchil and Tragulus napu. Both species can be distinguish by size, coat coloration, and throat pattern but clear diagnosis still cannot be found. The objective of the study is to show the genetic distance relationship between T. kanchil and T. napu and their population based on mitochondrial DNA (mtDNA) cytochrome oxidase I (COI) and D-loop region. There are 42 sample of mousedeer were used in this study collected by PERHILITAN from different locality. Another 29 D-loop sequence were retrieved from Genbank for comparative analysis. All sample were amplified using universal primer and species-specific primer for COI and D-loop genes via PCR process. The amplified sequences were analyzed to determine genetic distance of T. kanchil and T. napu. From the analysis, the average genetic distance between T. kanchil and T. napu based on locus COI and D-loop were 0.145 and 0.128 respectively. The genetic distance between populations of T. kanchil based on locus COI was between 0.003-0.013. For locus D-loop, genetic distance analysis showed distance in relationship between west-coast populations to east-coast population of T. kanchil. COI and D-loop mtDNA region provided a clear picture on the relationship within the mousedeer species. Last but not least, conservation effort toward protecting this species can be done by study the molecular genetics and prevent the extinction of this species.

Self-stabilizing optical clock pulse-train generator using SOA and saturable absorber for asynchronous optical packet processing.

PubMed

Nakahara, Tatsushi; Takahashi, Ryo

2013-05-06

We propose a novel, self-stabilizing optical clock pulse-train generator for processing preamble-free, asynchronous optical packets with variable lengths. The generator is based on an optical loop that includes a semiconductor optical amplifier (SOA) and a high-extinction spin-polarized saturable absorber (SA), with the loop being self-stabilized by balancing out the gain and absorption provided by the SOA and SA, respectively. The optical pulse train is generated by tapping out a small portion of a circulating seed pulse. The convergence of the generated pulse energy is enabled by the loop round-trip gain function that has a negative slope due to gain saturation in the SOA. The amplified spontaneous emission (ASE) of the SOA is effectively suppressed by the SA, and a backward optical pulse launched into the SOA enables overcoming the carrier-recovery speed mismatch between the SOA and SA. Without external control for the loop gain, a stable optical pulse train consisting of more than 50 pulses with low jitter is generated from a single 10-ps seed optical pulse even with a variation of 10 dB in the seed pulse intensity.

Modeling and Simulation of a Parametrically Resonant Micromirror With Duty-Cycled Excitation

PubMed Central

Shahid, Wajiha; Qiu, Zhen; Duan, Xiyu; Li, Haijun; Wang, Thomas D.; Oldham, Kenn R.

2014-01-01

High frequency large scanning angle electrostatically actuated microelectromechanical systems (MEMS) mirrors are used in a variety of applications involving fast optical scanning. A 1-D parametrically resonant torsional micromirror for use in biomedical imaging is analyzed here with respect to operation by duty-cycled square waves. Duty-cycled square wave excitation can have significant advantages for practical mirror regulation and/or control. The mirror’s nonlinear dynamics under such excitation is analyzed in a Hill’s equation form. This form is used to predict stability regions (the voltage-frequency relationship) of parametric resonance behavior over large scanning angles using iterative approximations for nonlinear capacitance behavior of the mirror. Numerical simulations are also performed to obtain the mirror’s frequency response over several voltages for various duty cycles. Frequency sweeps, stability results, and duty cycle trends from both analytical and simulation methods are compared with experimental results. Both analytical models and simulations show good agreement with experimental results over the range of duty cycled excitations tested. This paper discusses the implications of changing amplitude and phase with duty cycle for robust open-loop operation and future closed-loop operating strategies. PMID:25506188

Critical dimensional linewidth calibration using UV microscope and laser interferometry

NASA Astrophysics Data System (ADS)

Li, Qi; Gao, Si-tian; Li, Wei; Lu, Ming-zhen; Zhang, Ming-kai

2013-10-01

In order to calibrate the critical dimensional (CD) uncertainty of lithography masks in semiconductor manufacturing, NIM is building a two dimensional metrological UV microscope which has traceable measurement ability for nanometer linewidths and pitches. The microscope mainly consists of UV light receiving components, piezoelectric ceramics (PZT) driven stage and interferometer calibration framework. In UV light receiving components they include all optical elements on optical path. The UV light originates from Köhler high aperture transmit/reflect illumination sources; then goes through objective lens to UV splitting optical elements; after that, one part of light attains UV camera for large range calibration, the other part of light passes through a three dimensional adjusted pinhole and is collected by PMT for nanoscale scanning. In PZT driven stage, PZT stick actuators with closed loop control are equipped to push/pull a flexural hinge based platform. The platform has a novel designed compound flexural hinges which nest separate X, Y direction moving mechanisms within one layer but avoiding from mutual cross talk, besides this, the hinges also contain leverage structures to amplify moving distance. With these designs, the platform can attain 100 μm displacement ranges as well as 1 nm resolution. In interferometer framework a heterodyne multi-pass interferometer is mounted on the platform, which measures X-Y plane movement and Z axis rotation, through reference mirror mounted on objective lens tube and Zerodur mirror mounted on PZT platform, the displacement is traced back to laser wavelength. When development is finished, the apparatus can offer the capability to calibrate one dimensional linewidths and two dimensional pitches ranging from 200nm to 50μm with expanded uncertainty below 20nm.

Sparse aperture differential piston measurements using the pyramid wave-front sensor

NASA Astrophysics Data System (ADS)

Arcidiacono, Carmelo; Chen, Xinyang; Yan, Zhaojun; Zheng, Lixin; Agapito, Guido; Wang, Chaoyan; Zhu, Nenghong; Zhu, Liyun; Cai, Jianqing; Tang, Zhenghong

2016-07-01

In this paper we report on the laboratory experiment we settled in the Shanghai Astronomical Observatory (SHAO) to investigate the pyramid wave-front sensor (WFS) ability to measure the differential piston on a sparse aperture. The ultimate goal is to verify the ability of the pyramid WFS work in close loop to perform the phasing of the primary mirrors of a sparse Fizeau imaging telescope. In the experiment we installed on the optical bench we performed various test checking the ability to flat the wave-front using a deformable mirror and to measure the signal of the differential piston on a two pupils setup. These steps represent the background from which we start to perform full close loop operation on multiple apertures. These steps were also useful to characterize the achromatic double pyramids (double prisms) manufactured in the SHAO optical workshop.

Close-loop performance of a high precision deflectometry controlled deformable mirror (DCDM) unit for wavefront correction in adaptive optics system

NASA Astrophysics Data System (ADS)

Huang, Lei; Zhou, Chenlu; Zhao, Wenchuan; Choi, Heejoo; Graves, Logan; Kim, Daewook

2017-06-01

We present a high precision deflectometry system (DS) controlled deformable mirror (DM) solution for optical system. Different from wavefront and non-wavefront system, the DS and the DM are set to be an individual integrated DCDM unit and can be installed in one base plate. In the DCDM unit, the DS can directly provide the influence functions and surface shape of the DM to the industrial computer in any adaptive optics system. As an integrated adaptive unit, the DCDM unit could be put into various optical systems to realize aberration compensation. In this paper, the configuration and principle of the DCDM unit is introduced first. Theoretical simulation on the close-loop performance of the DCDM unit is carried out. Finally, a verification experiment is proposed to verify the compensation capability of the DCDM unit.

Effect of control-beam polarization and power on optical time-domain demultiplexing in a new nonlinear optical loop mirror design

NASA Astrophysics Data System (ADS)

Grendár, Drahomír; Pottiez, Olivier; Dado, Milan; Müllerová, Jarmila; Dubovan, Jozef

2009-05-01

A new scheme of a control-beam-driven nonlinear optical loop mirror (NOLM) with a birefringent twisted fiber and a symmetrical coupler designed for optical time division demultiplexing (OTDM) is analyzed. The theoretical model of the proposed NOLM scheme considers the evolution of polarization states of data and control beams and the mutual interactions of the data and control beams due to the cross-phase modulation (XPM). Attention is given to the optical switching commanded by the control-beam power and by the manipulation of nonlinear polarization rotation of the data and control beam. The simulations of NOLM transmissions demonstrate that the cross talk between demultiplexed and nondemultiplexed beams as an important parameter for optical switching by the presented NOLM can be significantly reduced. The results show that the device can be of interest for all-optical signal manipulations in optical communication networks.

Resistor-less charge sensitive amplifier for semiconductor detectors

NASA Astrophysics Data System (ADS)

Pelczar, K.; Panas, K.; Zuzel, G.

2016-11-01

A new concept of a Charge Sensitive Amplifier without a high-value resistor in the feedback loop is presented. Basic spectroscopic parameters of the amplifier coupled to a coaxial High Purity Germanium detector (HPGe) are discussed. The amplifier signal input is realized with an n-channel J-FET transistor. The feedback capacitor is discharged continuously by the second, forward biased n-channel J-FET, driven by an RC low-pass filter. Both the analog-with a standard spectroscopy amplifier and a multi-channel analyzer-and the digital-by applying a Flash Analog to Digital Converter-signal readouts were tested. The achieved resolution in the analog and the digital readouts was 0.17% and 0.21%, respectively, at the Full Width at Half Maximum of the registered 60Co 1332.5 keV gamma line.

Constant peak-power single-frequency linearly-polarized all-fiber laser for coherent detection based on closed-loop feedback technology

NASA Astrophysics Data System (ADS)

Ding, Yaqian; Zhang, Xiang; Li, Dong; Wang, Dapeng; Zhang, Renzhong; Song, Chengying; Che, Haozhao; Wang, Rui; Guo, Baoling; Chen, Guanghui

2015-10-01

In this paper, a practical single-frequency high-repetition linearly-polarized eye-safe all-fiber laser with constant peak power is demonstrated. It is based on master-oscillator power amplifier (MOPA) system. A distributed feedback laser diode simulating at 1550nm with narrow linewidth of 2.3 kHz is employed as the seed source. It is modulated to a pulse laser with high repetition of 20 kHz and peak power of 10mW by an acousto-optic modulator (AOM). The pulse width is tunable between 100ns to 400ns. Two-stage cascade amplifier is established, which consists of a pre-amplifier and a power-amplifier. Amplified spontaneous emission (ASE) and stimulated billion scattering are well suppressed by special management. The output peak power of 30W is obtained, which has nearly diffraction-limited beam quality. It operates in linewidth of 1.2MHz, polarization-extinction ratio (PER) of 25dB and signal-to-noise ratio (SNR) of more than 40dB. Gain of the whole amplifier achieves nearly 35dB. Furthermore, an embedded control system (ECS) based on the WinCE operating system (OS) and the chip of S3C2440 is proposed. This control system based on closed-loop feedback technology makes the peak power keeping constant even the pulse width tunable, which is convenient for the end user of the radar. This robust portable laser is remarkable and fulfills the desire of coherent detection excellently.

The Novel Multiple Inner Primers-Loop-Mediated Isothermal Amplification (MIP-LAMP) for Rapid Detection and Differentiation of Listeria monocytogenes.

PubMed

Wang, Yi; Wang, Yan; Ma, Aijing; Li, Dongxun; Luo, Lijuan; Liu, Dongxin; Hu, Shoukui; Jin, Dong; Liu, Kai; Ye, Changyun

2015-12-03

Here, a novel model of loop-mediated isothermal amplification (LAMP), termed multiple inner primers-LAMP (MIP-LAMP), was devised and successfully applied to detect Listeria monocytogenes. A set of 10 specific MIP-LAMP primers, which recognized 14 different regions of target gene, was designed to target a sequence in the hlyA gene. The MIP-LAMP assay efficiently amplified the target element within 35 min at 63 °C and was evaluated for sensitivity and specificity. The templates were specially amplified in the presence of the genomic DNA from L. monocytogenes. The limit of detection (LoD) of MIP-LAMP assay was 62.5 fg/reaction using purified L. monocytogenes DNA. The LoD for DNA isolated from serial dilutions of L. monocytogenes cells in buffer and in milk corresponded to 2.4 CFU and 24 CFU, respectively. The amplified products were analyzed by real-time monitoring of changes in turbidity, and visualized by adding Loop Fluorescent Detection Reagent (FD), or as a ladder-like banding pattern on gel electrophoresis. A total of 48 pork samples were investigated for L. monocytogenes by the novel MIP-LAMP method, and the diagnostic accuracy was shown to be 100% when compared to the culture-biotechnical method. In conclusion, the MIP-LAMP methodology was demonstrated to be a reliable, sensitive and specific tool for rapid detection of L. monocytogenes strains.

Electronic circuits

NASA Technical Reports Server (NTRS)

1976-01-01

Twenty-nine circuits and circuit techniques developed for communications and instrumentation technology are described. Topics include pulse-code modulation, phase-locked loops, data coding, data recording, detection circuits, logic circuits, oscillators, and amplifiers.

Accounting for a mirror-image conformation as a subtle effect in protein folding.

PubMed

Kachlishvili, Khatuna; Maisuradze, Gia G; Martin, Osvaldo A; Liwo, Adam; Vila, Jorge A; Scheraga, Harold A

2014-06-10

By using local (free-energy profiles along the amino acid sequence and (13)C(α) chemical shifts) and global (principal component) analyses to examine the molecular dynamics of protein-folding trajectories, generated with the coarse-grained united-residue force field, for the B domain of staphylococcal protein A, we are able to (i) provide the main reason for formation of the mirror-image conformation of this protein, namely, a slow formation of the second loop and part of the third helix (Asp29-Asn35), caused by the presence of multiple local conformational states in this portion of the protein; (ii) show that formation of the mirror-image topology is a subtle effect resulting from local interactions; (iii) provide a mechanism for how protein A overcomes the barrier between the metastable mirror-image state and the native state; and (iv) offer a plausible reason to explain why protein A does not remain in the metastable mirror-image state even though the mirror-image and native conformations are at least energetically compatible.

Accounting for a mirror-image conformation as a subtle effect in protein folding

PubMed Central

Kachlishvili, Khatuna; Maisuradze, Gia G.; Martin, Osvaldo A.; Liwo, Adam; Vila, Jorge A.; Scheraga, Harold A.

2014-01-01

By using local (free-energy profiles along the amino acid sequence and 13Cα chemical shifts) and global (principal component) analyses to examine the molecular dynamics of protein-folding trajectories, generated with the coarse-grained united-residue force field, for the B domain of staphylococcal protein A, we are able to (i) provide the main reason for formation of the mirror-image conformation of this protein, namely, a slow formation of the second loop and part of the third helix (Asp29–Asn35), caused by the presence of multiple local conformational states in this portion of the protein; (ii) show that formation of the mirror-image topology is a subtle effect resulting from local interactions; (iii) provide a mechanism for how protein A overcomes the barrier between the metastable mirror-image state and the native state; and (iv) offer a plausible reason to explain why protein A does not remain in the metastable mirror-image state even though the mirror-image and native conformations are at least energetically compatible. PMID:24912167

Feedback-controlled radiation pressure cooling

NASA Astrophysics Data System (ADS)

Prior, Yehiam; Vilensky, Mark; Averbukh, Ilya Sh.

2008-03-01

We propose a new approach to laser cooling of micromechanical devices, which is based on the phenomenon of optical bistability. These devices are modeled as a Fabry-Perot resonator with one fixed and one oscillating mirror. The bistability may be induced by an external feedback loop. When excited by an external laser, the cavity field has two co-existing stable steady-states depending on the position of the moving mirror. If the latter moves slow enough, the field in the cavity adjusts itself adiabatically to the mirror's instantaneous position. The mirror experiences radiation pressure corresponding to the intensity value. A sharp transition between two values of the radiation pressure force happens twice per every period of the mirror oscillation at non-equivalent positions (hysteresis effect), which leads to a non-zero net energy loss. The cooling mechanism resembles Sisyphus cooling in which the cavity mode performs sudden transitions between two stable states. We provide a dynamical stability analysis of the coupled moving mirror -- cavity field system, and find the parameters for efficient cooling. Direct numerical simulations show that a bistable cavity provides much more efficient cooling compared to the regular one.

Efficient ECH-assisted plasma start-up using trapped particle configuration in the versatile experiment spherical torus

NASA Astrophysics Data System (ADS)

An, YoungHwa; Lee, Jeongwon; Jo, JongGab; Jung, Bong-Ki; Lee, HyunYeong; Chung, Kyoung-Jae; Na, Yong-Su; Hahm, T. S.; Hwang, Y. S.

2017-01-01

An efficient and robust ECH (electron cyclotron heating)-assisted plasma start-up scheme with a low loop voltage and low volt-second consumption utilizing the trapped particle configuration (TPC) has been developed in the versatile experiment spherical torus (VEST). The TPC is a mirror-like magnetic field configuration providing a vertical magnetic field in the same direction as the equilibrium field. It significantly enhances ECH pre-ionization with enhanced particle confinement due to its mirror effect, and intrinsically provides an equilibrium field with a stable decay index enabling prompt plasma current initiation. Consequently, the formation of TPC before the onset of the loop voltage allows the plasma to start up with a lower loop voltage and lower volt-second consumption as well as a wider operation range in terms of ECH pre-ionization power and H2 filling pressure. The TPC can improve the widely-used field null configuration significantly for more efficient start-up when ECH pre-ionization is used. This can then be utilized in superconducting tokamaks requiring a low loop voltage start-up, such as ITER, or in spherical tori with limited volt-seconds. The TPC can be particularly useful in superconducting tokamaks with a limited current slew-rate of superconducting PF coils, as it can save volt-second consumption before plasma current initiation by providing prompt initiation with an intrinsic stable equilibrium field.

A Fourier Transform Spectrometer Based on an Electrothermal MEMS Mirror with Improved Linear Scan Range

PubMed Central

Wang, Wei; Chen, Jiapin; Zivkovic, Aleksandar. S.; Xie, Huikai

2016-01-01

A Fourier transform spectrometer (FTS) that incorporates a closed-loop controlled, electrothermally actuated microelectromechanical systems (MEMS) micromirror is proposed and experimentally verified. The scan range and the tilting angle of the mirror plate are the two critical parameters for MEMS-based FTS. In this work, the MEMS mirror with a footprint of 4.3 mm × 3.1 mm is based on a modified lateral-shift-free (LSF) bimorph actuator design with large piston and reduced tilting. Combined with a position-sensitive device (PSD) for tilt angle sensing, the feedback controlled MEMS mirror generates a 430 µm stable linear piston scan with the mirror plate tilting angle less than ±0.002°. The usable piston scan range is increased to 78% of the MEMS mirror’s full scan capability, and a spectral resolution of 0.55 nm at 531.9 nm wavelength, has been achieved. It is a significant improvement compared to the prior work. PMID:27690047

Bimorph deformable mirror: an appropriate wavefront corrector for retinal imaging?

NASA Astrophysics Data System (ADS)

Laut, Sophie; Jones, Steve; Park, Hyunkyu; Horsley, David A.; Olivier, Scot; Werner, John S.

2005-11-01

The purpose of this study was to evaluate the performance of a bimorph deformable mirror from AOptix, inserted into an adaptive optics system designed for in-vivo retinal imaging at high resolution. We wanted to determine its suitability as a wavefront corrector for vision science and ophthalmological instrumentation. We presented results obtained in a closed-loop system, and compared them with previous open-loop performance measurements. Our goal was to obtain precise wavefront reconstruction with rapid convergence of the control algorithm. The quality of the reconstruction was expressed in terms of root-mean-squared wavefront residual error (RMS), and number of frames required to perform compensation. Our instrument used a Hartmann-Shack sensor for the wavefront measurements. We also determined the precision and ability of the deformable mirror to compensate the most common types of aberrations present in the human eye (defocus, cylinder, astigmatism and coma), and the quality of its correction, in terms of maximum amplitude of the corrected wavefront. In addition to wavefront correction, we had also used the closed-loop system to generate an arbitrary aberration pattern by entering the desired Hartmann-Shack centroid locations as input to the AO controller. These centroid locations were computed in Matlab for a user-defined aberration pattern, allowing us to test the ability of the DM to generate and compensate for various aberrations. We conclude that this device, in combination with another DM based on Micro-Electro Mechanical Systems (MEMS) technology, may provide better compensation of the higher-order ocular wavefront aberrations of the human eye

The effect of compressive viscosity and thermal conduction on the longitudinal MHD waves

NASA Astrophysics Data System (ADS)

Bahari, K.; Shahhosaini, N.

2018-05-01

longitudinal Magnetohydrodynamic (MHD) oscillations have been studied in a slowly cooling coronal loop, in the presence of thermal conduction and compressive viscosity, in the linear MHD approximation. WKB method has been used to solve the governing equations. In the leading order approximation the dispersion relation has been obtained, and using the first order approximation the time dependent amplitude has been determined. Cooling causes the oscillations to amplify and damping mechanisms are more efficient in hot loops. In cool loops the oscillation amplitude increases with time but in hot loops the oscillation amplitude decreases with time. Our conclusion is that in hot loops the efficiency of the compressive viscosity in damping longitudinal waves is comparable to that of the thermal conduction.

The effect of compressive viscosity and thermal conduction on the longitudinal MHD waves

NASA Astrophysics Data System (ADS)

Bahari, K.; Shahhosaini, N.

2018-07-01

Longitudinal magnetohydrodynamic (MHD) oscillations have been studied in a slowly cooling coronal loop, in the presence of thermal conduction and compressive viscosity, in the linear MHD approximation. The WKB method has been used to solve the governing equations. In the leading order approximation the dispersion relation has been obtained, and using the first-order approximation the time-dependent amplitude has been determined. Cooling causes the oscillations to amplify and damping mechanisms are more efficient in hot loops. In cool loops the oscillation amplitude increases with time but in hot loops the oscillation amplitude decreases with time. Our conclusion is that in hot loops the efficiency of the compressive viscosity in damping longitudinal waves is comparable to that of the thermal conduction.

Analog circuit for the measurement of phase difference between two noisy sine-wave signals

NASA Technical Reports Server (NTRS)

Shakkottai, P.; Kwack, E. Y.; Back, L. H.

1989-01-01

A simple circuit was designed to measure the phase difference between two noisy sine waves. It locks over a wide range of frequencies and produces an output proportional to the phase difference of rapidly varying signals. A square wave locked in frequency and phase to the first signal is produced by a phase-locked loop and is amplified by an operational amplifier.

Photonic generation of ultra-wideband doublet pulse using a semiconductor-optical-amplifier based polarization-diversified loop.

PubMed

Luo, Bowen; Dong, Jianji; Yu, Yuan; Yang, Ting; Zhang, Xinliang

2012-06-15

We propose and demonstrate a novel scheme of ultra-wideband (UWB) doublet pulse generation using a semiconductor optical amplifier (SOA) based polarization-diversified loop (PDL) without any assistant light. In our scheme, the incoming gaussian pulse is split into two parts by the PDL, and each of them is intensity modulated by the other due to cross-gain modulation (XGM) in the SOA. Then, both parts are recombined with incoherent summation to form a UWB doublet pulse. Bi-polar UWB doublet pulse generation is demonstrated using an inverted gaussian pulse injection. Moreover, pulse amplitude modulation of UWB doublet is also experimentally demonstrated. Our scheme shows some advantages, such as simple implementation without assistant light and single optical carrier operation with good fiber dispersion tolerance.

Gain-assisted broadband ring cavity enhanced spectroscopy

NASA Astrophysics Data System (ADS)

Selim, Mahmoud A.; Adib, George A.; Sabry, Yasser M.; Khalil, Diaa

2017-02-01

Incoherent broadband cavity enhanced spectroscopy can significantly increase the effective path length of light-matter interaction to detect weak absorption lines over broad spectral range, for instance to detect gases in confined environments. Broadband cavity enhancement can be based on the decay time or the intensity drop technique. Decay time measurement is based on using tunable laser source that is expensive and suffers from long scan time. Intensity dependent measurement is usually reported based on broadband source using Fabry-Perot cavity, enabling short measurement time but suffers from the alignment tolerance of the cavity and the cavity insertion loss. In this work we overcome these challenges by using an alignment-free ring cavity made of an optical fiber loop and a directional coupler, while having a gain medium pumped below the lasing threshold to improve the finesse and reduce the insertion loss. Acetylene (C2H2) gas absorption is measured around 1535 nm wavelength using a semiconductor optical amplifier (SOA) gain medium. The system is analyzed for different ring resonator forward coupling coefficient and loses, including the 3-cm long gas cell insertion loss and fiber connector losses used in the experimental verification. The experimental results are obtained for a coupler ratio of 90/10 and a fiber length of 4 m. The broadband source is the amplified spontaneous emission of another SOA and the output is measured using a 70pm-resolution optical spectrum analyzer. The absorption depth and the effective interaction length are improved about an order of magnitude compared to the direct absorption of the gas cell. The presented technique provides an engineering method to improve the finesse and, consequently the effective length, while relaxing the technological constraints on the high reflectivity mirrors and free-space cavity alignment.

Fault-tolerant drive electronics for a Xinetics deformable mirror at GeMS DM0

NASA Astrophysics Data System (ADS)

Barberio, Michael J.

2016-07-01

Gemini South is replacing one of the (3) CILAS DMs with a 349-actuator Xinetics DM in its GeMS MCAO system. Xinetics mirrors operate over a 40-100V dynamic range and require that inter-actuator stroke differences are limited to half-scale; each actuator must be within 30V of its neighbor to prevent mechanical stress and possible face sheet separation. A robust way to implement this protection is to use high power transient voltage suppressors (TVSs) as a 2D-mesh between the amplifiers and mirror, but this has system implications. A sustained clamp condition dissipates significant power in the devices, and if an actuator fails as short (which occurred once with the DM in a thermal chamber), the system is subject to a cascade failure event as multiple outputs drive the shorted actuator through the TVS network. This latter risk is readily resolved by using series fuses to the DM. In this third-generation driver, current sensing and logic inhibit amplifier outputs after a sustained TVS clamp condition or shorted output, and LED indicators show the location. Redundant thermal sensing is used on modular TVS row and column boards. A second 2D-mesh of high impedance resistors after the fuses will hold an unpowered channel to the average voltage of its neighbors, with a negligible influence function. A Failure Modes and Effects Analysis shows significant fault tolerance.

[The design of all solid-state tunable pulsed Ti:sapphire laser system].

PubMed

Chen, Zhe; Ku, Geng; Wan, Junchao; Wang, Wei; Zhou, Chuanqing

2013-05-01

This paper presented a design of broadly all solid-state tunable pulsed Ti:sapphire laser with high power and stable performance. The laser was pumped by custom-made Nd:YAG laser which had water cooling system and amplified by two stage amplifier. The method accomplished tunable output of all solid-state tunable pulsed Ti:sapphire laser by modifying the reflection angle of the back mirror. We investigated the relationship between the power of the pumping laser and the all solid-state tunable pulsed Ti: sapphire laser by changing the power of the pumping source.

Electroformed Nickel Mirrors for the Next Generation Space Telescope

NASA Technical Reports Server (NTRS)

Redmon, John W.; Engelhaupt, Darrel

1998-01-01

This paper summarizes the work to date on a novel mirror fabrication technique being developed at the Marshall Space Flight Center for potential use on the Next Generation Space Telescope (NGST). This technique involves forming an extremely lightweight mirror by electroplating nickel and nickel based alloys onto a highly polished precision mandrel. The resulting mirror shell can then be backed up with or attached to a lightweight structure to produce a mirror element that is on the order of 15 kg/sq m areal density. Since the mirrors are fabricated from a mandrel (or master), subsequent mirrors can be made with very high economy; this technique is particularly suited to segmented mirrors schemes whereby large apertures are achieved through the deployment of smaller segments. Control of the electroplating process is the key element for producing high quality optics; bath chemistry and real time control of the plating current density yields uniform grained electroforms with zero residual stress. To accomplish this, a special electronic sensor was developed whereby the residual stress can be monitored as the nickel is electrolytically deposited. This information is used in a feedback loop to modulate current density which, in turn, directly governs the residual stress. Details pertaining to this and other aspects of the fabrication of a half meter mirror will be published along with test results and metrology data.

Method and apparatus for reducing microwave oscillator output noise

NASA Technical Reports Server (NTRS)

Dick, G. John (Inventor); Saunders, Jonathan E. (Inventor)

1991-01-01

Microwave oscilltors incorporate r.f. feedback with carrier suppression to reduce phase noise. In a direct feedback oscillator arrngement a circulator is interposed between the r.f. amplifier and the high-Q resonator. The amplifier output is applied to the slightly over-coupled input port of the resonator so that the resultant net return signal is the vectorial difference between the signals emitted and reflected from the resonator. The gain of the r.f. amplifier is chosen to regenerate the forward signal from the net return signal. In a STALO-type arrangement, the resonator is critically coupled and an r.f. amplifier added to the path of the net return signal. The sensitivity of the STALO-type feedback loop is thereby enhanced while added amplifier noise is minimized by the superposition of the signals emitted by and reflected from the resonator.

Phase-Noise and Amplitude-Noise Measurement of Low-Power Signals

NASA Technical Reports Server (NTRS)

Rubiola, Enrico; Salik, Ertan; Yu, Nan; Maleki, Lute

2004-01-01

Measuring the phase fluctuation between a pair of low-power microwave signals, the signals must be amplified before detection. In such cases the phase noise of the amplifier pair is the main cause of 1/f background noise of the instrument. this article proposes a scheme that makes amplification possible while rejecting the close in 1/f (flicker) noise of the two amplifiers. Noise rejection, which relies upon the understanding of the amplifier noise mechanism does not require averaging. Therefore, our scheme can also be the detector of a closed loop noise reduction system. the first prototype, compared to a traditional saturated mixer system under the same condition, show a 24 dB noise reduction of the 1/f region.

Disruption of a stem-loop structure located upstream of pseudoknot domain in Tobacco mosaic virus enhanced its infectivity and viral RNA accumulation.

PubMed

Guo, Song; Wong, Sek-Man

2018-06-01

A predicted stem-loop structure of 25 nucleotides, located in the coat protein (CP) gene and 3'-UTR sequences of Tobacco mosaic virus (TMV), was validated previously (Guo et al., 2015). In this study, both disrupted stem-loop and nucleotide deletion mutants of TMV replicated more rapidly in Nicotiana benthamiana protoplasts. The TMV mutant with a complete mirrored stem-loop structure showed similar level of viral RNA accumulation as TMV. Recovering the stem-loop structure also resulted in a similar replication level as TMV. All these mutants induced necrosis in N. benthamiana and assembled into typical rigid rod-shaped virions. TMV mutant without the stem-loop structure induced more local lesions in Chenopodium quinoa. When the putative stem-loop structure in Tomato mosaic virus (ToMV) was disrupted, the mutant also showed an enhanced virus replication. This suggests that the stem-loop structure of TMV is a new cis-acting element with a role in virus replication. Copyright © 2018 Elsevier Inc. All rights reserved.

Akt kinase C-terminal modifications control activation loop dephosphorylation and enhance insulin response.

PubMed

Chan, Tung O; Zhang, Jin; Tiegs, Brian C; Blumhof, Brian; Yan, Linda; Keny, Nikhil; Penny, Morgan; Li, Xue; Pascal, John M; Armen, Roger S; Rodeck, Ulrich; Penn, Raymond B

2015-10-01

The Akt protein kinase, also known as protein kinase B, plays key roles in insulin receptor signalling and regulates cell growth, survival and metabolism. Recently, we described a mechanism to enhance Akt phosphorylation that restricts access of cellular phosphatases to the Akt activation loop (Thr(308) in Akt1 or protein kinase B isoform alpha) in an ATP-dependent manner. In the present paper, we describe a distinct mechanism to control Thr(308) dephosphorylation and thus Akt deactivation that depends on intramolecular interactions of Akt C-terminal sequences with its kinase domain. Modifications of amino acids surrounding the Akt1 C-terminal mTORC2 (mammalian target of rapamycin complex 2) phosphorylation site (Ser(473)) increased phosphatase resistance of the phosphorylated activation loop (pThr(308)) and amplified Akt phosphorylation. Furthermore, the phosphatase-resistant Akt was refractory to ceramide-dependent dephosphorylation and amplified insulin-dependent Thr(308) phosphorylation in a regulated fashion. Collectively, these results suggest that the Akt C-terminal hydrophobic groove is a target for the development of agents that enhance Akt phosphorylation by insulin. © 2015 Authors; published by Portland Press Limited.

Akt kinase C-terminal modifications control activation loop dephosphorylation and enhance insulin response

PubMed Central

Chan, Tung O.; Zhang, Jin; Tiegs, Brian C.; Blumhof, Brian; Yan, Linda; Keny, Nikhil; Penny, Morgan; Li, Xue; Pascal, John M.; Armen, Roger S.; Rodeck, Ulrich; Penn, Raymond B.

2015-01-01

The Akt protein kinase, also known as protein kinase B, plays key roles in insulin receptor signalling and regulates cell growth, survival and metabolism. Recently, we described a mechanism to enhance Akt phosphorylation that restricts access of cellular phosphatases to the Akt activation loop (Thr308 in Akt1 or protein kinase B isoform alpha) in an ATP-dependent manner. In the present paper, we describe a distinct mechanism to control Thr308 dephosphorylation and thus Akt deactivation that depends on intramolecular interactions of Akt C-terminal sequences with its kinase domain. Modifications of amino acids surrounding the Akt1 C-terminal mTORC2 (mammalian target of rapamycin complex 2) phosphorylation site (Ser473) increased phosphatase resistance of the phosphorylated activation loop (pThr308) and amplified Akt phosphorylation. Furthermore, the phosphatase-resistant Akt was refractory to ceramide-dependent dephosphorylation and amplified insulin-dependent Thr308 phosphorylation in a regulated fashion. Collectively, these results suggest that the Akt C-terminal hydrophobic groove is a target for the development of agents that enhance Akt phosphorylation by insulin. PMID:26201515

Experimental investigation of the deformable mirror with bidirectional thermal actuators.

PubMed

Huang, Lei; Ma, Xingkun; Gong, Mali; Bian, Qi

2015-06-29

A deformable mirror with actuators of thermoelectric coolers (TECs) is introduced in this paper. Due to the bidirectional thermal actuation property of the TEC, both upward and downward surface control is available for the DM. The response functions of the actuators are investigated. A close-loop wavefront control experiment is performed too, where the defocus and the astigmatism were corrected. The results reveal that there is a promising prospect for the novel design to be used in corrections of static aberrations, such as in the Inertial Confinement Fusion (ICF).

Stabilization and control of the carrier-envelope phase of high-power femtosecond laser pulses using the direct locking technique.

PubMed

Imran, Tayyab; Lee, Yong S; Nam, Chang H; Hong, Kyung-Han; Yu, Tae J; Sung, Jae H

2007-01-08

We have stabilized and electronically controlled the carrier-envelope phase (CEP) of high-power femtosecond laser pulses, generated in a grating-based chirped-pulse amplification kHz Ti:sapphire laser, using the direct locking technique [Opt. Express 13, 2969 (2005)] combined with a slow feedback loop. An f-2f spectral interferometer has shown the CEP stabilities of 1.2 rad with the direct locking loop applied to the oscillator and of 180 mrad with an additional slow feedback loop, respectively. The electronic CEP modulations that can be easily realized in the direct locking loop are also demonstrated with the amplified pulses.

Control of adaptive optic element displacement with the help of a magnetic rheology drive

NASA Astrophysics Data System (ADS)

Deulin, Eugeni A.; Mikhailov, Valeri P.; Sytchev, Victor V.

2000-10-01

The control system of adaptive optic of a large astronomical segmentated telescope was designed and tested. The dynamic model and the amplitude-frequency analysis of the new magnetic rheology (MR) drive are presented. The loop controlled drive consists of hydrostatic carrier, MR hydraulic loop controlling system, elastic thin wall seal, stainless seal which are united in a single three coordinate manipulator. This combination ensures short positioning error (delta) (phi)

Conformational motions regulate phosphoryl transfer in related protein tyrosine phosphatases

PubMed Central

Whittier, Sean K.; Hengge, Alvan C.; Loria, J. Patrick

2014-01-01

Many studies have implicated a role for conformational motions during the catalytic cycle, acting to optimize the binding pocket or facilitate product release, but a more intimate role in the chemical reaction has not been described. We address this by monitoring active-site loop motion in two protein tyrosine phosphatases (PTPs) using NMR spectroscopy. The PTPs, YopH and PTP1B, have very different catalytic rates, however we find in both that the active-site loop closes to its catalytically competent position at rates that mirror the phosphotyrosine cleavage kinetics. This loop contains the catalytic acid, suggesting that loop closure occurs concomitantly with the protonation of the leaving group tyrosine and explains the different kinetics of two otherwise chemically and mechanistically indistinguishable enzymes. PMID:23970698

High-reflectivity phase conjugation using Brillouin preamplification.

PubMed

Ridley, K D; Scott, A M

1990-07-15

We describe experiments in which a weak laser pulse is phase conjugated by using a high-gain Brillouin amplifier in front of a stimulated Brillouin scattering phase-conjugate mirror. We observe phase conjugation with signal energies as low as 3 x 10(-13) J and with a maximum reflection coefficient of 2 x 10(8).

The generation of amplified spontaneous emission in high-power CPA laser systems.

PubMed

Keppler, Sebastian; Sävert, Alexander; Körner, Jörg; Hornung, Marco; Liebetrau, Hartmut; Hein, Joachim; Kaluza, Malte Christoph

2016-03-01

An analytical model is presented describing the temporal intensity contrast determined by amplified spontaneous emission in high-intensity laser systems which are based on the principle of chirped pulse amplification. The model describes both the generation and the amplification of the amplified spontaneous emission for each type of laser amplifier. This model is applied to different solid state laser materials which can support the amplification of pulse durations ≤350 fs . The results are compared to intensity and fluence thresholds, e.g. determined by damage thresholds of a certain target material to be used in high-intensity applications. This allows determining if additional means for contrast improvement, e.g. plasma mirrors, are required for a certain type of laser system and application. Using this model, the requirements for an optimized high-contrast front-end design are derived regarding the necessary contrast improvement and the amplified "clean" output energy for a desired focussed peak intensity. Finally, the model is compared to measurements at three different high-intensity laser systems based on Ti:Sapphire and Yb:glass. These measurements show an excellent agreement with the model.

1.2 MW peak power, all-solid-state picosecond laser with a microchip laser seed and a high gain single-passing bounce geometry amplifier

NASA Astrophysics Data System (ADS)

Wang, Chunhua; Shen, Lifeng; Zhao, Zhiliang; Liu, Bin; Jiang, Hongbo; Chen, Jun; Liu, Chong

2016-11-01

A semiconductor saturable absorber mirror (SESAM) based passively Q-switched microchip Nd:YVO4 seed laser with pulse duration of 90 ps at repetition rate of 100 kHz is amplified by single-passing a Nd:YVO4 bounce amplifier with varying seed input power from 20 μW to 10 mW. The liquid pure metal greasy thermally conductive material is used to replace the traditional thin indium foil as the thermal contact material for better heat load transfer of the Nd:YVO4 bounce amplifier. Temperature distribution at the pump surface is measured by an infrared imager to compare with the numerically simulated results. A highest single-passing output power of 11.3 W is obtained for 10 mW averaged seed power, achieving a pulse peak power of ~1.25 MW and pulse energy of ~113 μJ. The beam quality is well preserved with M2 ≤1.25. The simple configuration of this bounce laser amplifier made the system flexible, robust and cost-effective, showing attractive potential for further applications.

Two-loop virtual top-quark effect on Higgs-boson decay to bottom quarks.

PubMed

Butenschön, Mathias; Fugel, Frank; Kniehl, Bernd A

2007-02-16

In most of the mass range encompassed by the limits from the direct search and the electroweak precision tests, the Higgs boson of the standard model preferably decays to bottom quarks. We present, in analytic form, the dominant two-loop electroweak correction, of O(GF2mt4), to the partial width of this decay. It amplifies the familiar enhancement due to the O(GFmt2) one-loop correction by about +16% and thus more than compensates the screening by about -8% through strong-interaction effects of order O(alphasGFmt2).

Quantum noise and squeezing in optical parametric oscillator with arbitrary output coupling

NASA Technical Reports Server (NTRS)

Prasad, Sudhakar

1993-01-01

The redistribution of intrinsic quantum noise in the quadratures of the field generated in a sub-threshold degenerate optical parametric oscillator exhibits interesting dependences on the individual output mirror transmittances, when they are included exactly. We present a physical picture of this problem, based on mirror boundary conditions, which is valid for arbitrary transmittances. Hence, our picture applies uniformly to all values of the cavity Q factor representing, in the opposite extremes, both perfect oscillator and amplifier configurations. Beginning with a classical second-harmonic pump, we shall generalize our analysis to the finite amplitude and phase fluctuations of the pump.

Scattering (stochastic) recoupling of a coupled ten-stripe AlGaAs-GaAs-InGaAs quantum-well heterostructure laser

NASA Astrophysics Data System (ADS)

Kellogg, D. A.; Holonyak, N.

2001-04-01

Data are presented on coupled ten-stripe AlGaAs-GaAs-InGaAs quantum well heterostructure (QWH) lasers recoupled stochastically at the cleaved end mirrors. Recoupling of neighboring elements of a ten-stripe laser is accomplished by the scattering (random feedback) afforded by applying ˜10-μm-diam Al powder or 0.3 μm α-Al2O3 polishing compound in microscopy immersion oil or in epoxy at the cleaved ends (mirrors). Data on QWH samples with the end mirrors coated with the scatterer (Al or Al2O3 powder in "liquid") exhibit spectral and far-field broadening, as well as increased laser threshold because of the reduced cavity Q. Single mode operation is possible with the conventional evanescent wave coupling of the ten-stripe QWH and is destroyed, even the laser operation itself, with the scattering recoupling (dephasing) at the end mirrors, which is reversible (removable). The narrow ten-stripe QWH laser with strong end-mirror scattering, a long amplifier with random feedback, indicates that a photopumped III-V or II-VI powder (a random "wall" cavity) has little or no merit.

A Nodal-independent and tissue-intrinsic mechanism controls heart-looping chirality

NASA Astrophysics Data System (ADS)

Noël, Emily S.; Verhoeven, Manon; Lagendijk, Anne Karine; Tessadori, Federico; Smith, Kelly; Choorapoikayil, Suma; den Hertog, Jeroen; Bakkers, Jeroen

2013-11-01

Breaking left-right symmetry in bilateria is a major event during embryo development that is required for asymmetric organ position, directional organ looping and lateralized organ function in the adult. Asymmetric expression of Nodal-related genes is hypothesized to be the driving force behind regulation of organ laterality. Here we identify a Nodal-independent mechanism that drives asymmetric heart looping in zebrafish embryos. In a unique mutant defective for the Nodal-related southpaw gene, preferential dextral looping in the heart is maintained, whereas gut and brain asymmetries are randomized. As genetic and pharmacological inhibition of Nodal signalling does not abolish heart asymmetry, a yet undiscovered mechanism controls heart chirality. This mechanism is tissue intrinsic, as explanted hearts maintain ex vivo retain chiral looping behaviour and require actin polymerization and myosin II activity. We find that Nodal signalling regulates actin gene expression, supporting a model in which Nodal signalling amplifies this tissue-intrinsic mechanism of heart looping.

Apparatus and methods for a human de-amplifier system

DOEpatents

Kress, Reid L.; Jansen, John F.

2000-01-01

A human de-amplifier system for interfacing a human operator and a physical object through a physical plant, wherein the physical object has dimensions in the range of 1 micrometer to 1 mm. The human de-amplifier system uses an inner-feedback loop to increases the equivalent damping of the operating system to stabilize the system when it contacts with the environment and reduces the impact of the environment variation by utilizing a high feedback gain, determined by a root locus sketch. Because the stability of the human de-amplifier system of the present invention is greatly enhanced over that of the prior art, the de-amplifier system is able to manipulate the physical object has dimensions in the range of 1 micrometer to 1 mm with high stability and accuracy. The system also has a monitoring device to monitor the motion of the physical object under manipulation.

A high efficiency PWM CMOS class-D audio power amplifier

NASA Astrophysics Data System (ADS)

Zhangming, Zhu; Lianxi, Liu; Yintang, Yang; Han, Lei

2009-02-01

Based on the difference close-loop feedback technique and the difference pre-amp, a high efficiency PWM CMOS class-D audio power amplifier is proposed. A rail-to-rail PWM comparator with window function has been embedded in the class-D audio power amplifier. Design results based on the CSMC 0.5 μm CMOS process show that the max efficiency is 90%, the PSRR is -75 dB, the power supply voltage range is 2.5-5.5 V, the THD+N in 1 kHz input frequency is less than 0.20%, the quiescent current in no load is 2.8 mA, and the shutdown current is 0.5 μA. The active area of the class-D audio power amplifier is about 1.47 × 1.52 mm2. With the good performance, the class-D audio power amplifier can be applied to several audio power systems.

Design and analysis of an active optics system for a 4-m telescope mirror combining hydraulic and pneumatic supports

NASA Astrophysics Data System (ADS)

Lousberg, Gregory P.; Moreau, Vincent; Schumacher, Jean-Marc; Piérard, Maxime; Somja, Aude; Gloesener, Pierre; Flebus, Carlo

2015-09-01

AMOS has developed a hybrid active optics system that combines hydraulic and pneumatic properties of actuators to support a 4-m primary mirror. The mirror is intended to be used in the Daniel K. Inouye Solar Telescope (DKIST, formerly the Advanced Technology Solar Telescope) that will be installed by the National Solar Observatory (NSO) atop the Haleakala volcano in Hawaii. The mirror support design is driven by the needs of (1) minimizing the support-induced mirror distortions under telescope operating conditions, (2) shaping the mirror surface to the desired profile, and (3) providing a high stiffness against wind loads. In order to fulfill these requirements, AMOS proposes an innovative support design that consist of 118 axial actuators and 24 lateral actuators. The axial support is based on coupled hydraulic and pneumatic actuators. The hydraulic part is a passive system whose main function is to support the mirror weight with a high stiffness. The pneumatic part is actively controlled so as to compensate for low-order wavefront aberrations that are generated by the mirror support itself or by any other elements in the telescope optical chain. The performances of the support and its adequacy with the requirements are assessed with the help of a comprehensive analysis loop involving finite-element, thermal and optical modellings.

Digital frequency offset-locked He–Ne laser system with high beat frequency stability, narrow optical linewidth and optical fibre output

NASA Astrophysics Data System (ADS)

Sternkopf, Christian; Manske, Eberhard

2018-06-01

We report on the enhancement of a previously-presented heterodyne laser source on the basis of two phase-locked loop (PLL) frequency coupled internal-mirror He–Ne lasers. Our new system consists of two digitally controlled He–Ne lasers with slightly different wavelengths, and offers high-frequency stability and very narrow optical linewidth. The digitally controlled system has been realized by using a FPGA controller and transconductance amplifiers. The light of both lasers was coupled into separate fibres for heterodyne interferometer applications. To enhance the laser performance we observed the sensitivity of both laser tubes to electromagnetic noise from various laser power supplies and frequency control systems. Furthermore, we describe how the linewidth of a frequency-controlled He–Ne laser can be reduced during precise frequency stabilisation. The digitally controlled laser source reaches a standard beat frequency deviation of less than 20 Hz (with 1 s gate time) and a spectral full width at half maximum (FWHM) of the beat signal less than 3 kHz. The laser source has enough optical output power to serve a fibre-coupled multi axis heterodyne interferometer. The system can be adjusted to output beat frequencies in the range of 0.1 MHz–20 MHz.

First results of the wind evaluation breadboard for ELT primary mirror design

NASA Astrophysics Data System (ADS)

Reyes García-Talavera, Marcos; Viera, Teodora; Núñez, Miguel

2010-07-01

The Wind Evaluation Breadboard (WEB) is a primary mirror and telescope simulator formed by seven aluminium segments, including position sensors, electromechanical support systems and support structures. WEB has been developed to evaluate technologies for primary mirror wavefront control and to evaluate the performance of the control of wind buffeting disturbance on ELT segmented mirrors. For this purpose WEB electro-mechanical set-up simulates the real operational constrains applied to large segmented mirrors. This paper describes the WEB assembly, integration and verification, the instrument characterisation and close loop control design, including the dynamical characterization of the instrument and the control architecture. The performance of the new technologies developed for position sensing, acting and controlling is evaluated. The integration of the instrument in the observatory and the results of the first experiments are summarised, with different wind conditions, elevation and azimuth angles of incidence. Conclusions are extracted with respect the wind rejection performance and the control strategy for an ELT. WEB has been designed and developed by IAC, ESO, ALTRAN and JUPASA, with the integration of subsystems of FOGALE and TNO.

Distortion cancellation performance of miniature delay filters for feed-forward linear power amplifiers.

PubMed

Roy, Manas K

2002-11-01

The technique of feed-forward amplitude control has been widely used in the linearization of power amplifiers for wireless communication systems. In this technique, an error signal due to third order intermodulation distortion (IMD) is extracted, amplified, and used to correct the delayed main line distorted signal. For example, a miniature prototype base station for the Global System for Mobile Communications/Code Division Multiple Access (GSM/CDMA) cellular system uses feed-forward amplifiers with bulky and expensive coaxial cables, about 20 feet in length, to provide about 25 ns of delay. This paper shows alternate space-saving approaches of achieving these delays using three different types of delay filters: electromagnetic interdigital/lumped (<2.5"), ceramic (<1.8"), and ladder-type surface acoustic wave (SAW) (0.15"). The delay lines introduce phase and amplitude imbalance and delay mismatch in the linearization loop due to fabrication tolerances. These adversely affect the IMD cancellation. Using an RF system simulation tool, this paper critically compares the IMD cancellation performance achieved using the three technologies. Simulation results show that the optimization of delay mismatch can achieve the desired cancellation more easily than other parameters. It is shown that, if the critical system parameter (phase deviation from linearity), is maintained at <2.5 degrees peak-to-peak over a 20 MHz bandwidth in the frequency range 855 MHz to 875 MHz, one can achieve 25 dB of IMD cancellation performance. This paper concludes with the suggestion of a set of realistic specifications for a miniature delay filter for the low power loop of the feed-forward amplifier.

21 CFR 874.4420 - Ear, nose, and throat manual surgical instrument.

Code of Federal Regulations, 2010 CFR

2010-04-01

... device includes the esophageal dilator; tracheal bistour (a long, narrow surgical knife); tracheal dilator; tracheal hook; laryngeal injection set; laryngeal knife; laryngeal saw; laryngeal trocar...; wire ear loop; microrule; mirror; mobilizer; ear, nose, and throat punch; ear, nose and throat knife...

Quasi-monolithic tunable optical resonator

NASA Technical Reports Server (NTRS)

Arbore, Mark (Inventor); Tapos, Francisc (Inventor)

2003-01-01

An optical resonator has a piezoelectric element attached to a quasi-monolithic structure. The quasi-monolithic structure defines an optical path. Mirrors attached to the structure deflect light along the optical path. The piezoelectric element controllably strains the quasi-monolithic structure to change a length of the optical path by about 1 micron. A first feedback loop coupled to the piezoelectric element provides fine control over the cavity length. The resonator may include a thermally actuated spacer attached to the cavity and a mirror attached to the spacer. The thermally actuated spacer adjusts the cavity length by up to about 20 microns. A second feedback loop coupled to the sensor and heater provides a coarse control over the cavity length. An alternative embodiment provides a quasi-monolithic optical parametric oscillator (OPO). This embodiment includes a non-linear optical element within the resonator cavity along the optical path. Such an OPO configuration is broadly tunable and capable of mode-hop free operation for periods of 24 hours or more.

Slope efficiency over 30% single-frequency ytterbium-doped fiber laser based on Sagnac loop mirror filter.

PubMed

Yin, Mojuan; Huang, Shenghong; Lu, Baole; Chen, Haowei; Ren, Zhaoyu; Bai, Jintao

2013-09-20

A high-slope-efficiency single-frequency (SF) ytterbium-doped fiber laser, based on a Sagnac loop mirror filter (LMF), was demonstrated. It combined a simple linear cavity with a Sagnac LMF that acted as a narrow-bandwidth filter to select the longitudinal modes. And we introduced a polarization controller to restrain the spatial hole burning effect in the linear cavity. The system could operate at a stable SF oscillating at 1064 nm with the obtained maximum output power of 32 mW. The slope efficiency was found to be primarily dependent on the reflectivity of the fiber Bragg grating. The slope efficiency of multi-longitudinal modes was higher than 45%, and the highest slope efficiency of the single longitudinal mode we achieved was 33.8%. The power stability and spectrum stability were <2% and <0.1%, respectively, and the signal-to-noise ratio measured was around 60 dB.

High-resolution quantization based on soliton self-frequency shift and spectral compression in a bi-directional comb-fiber architecture

NASA Astrophysics Data System (ADS)

Zhang, Xuyan; Zhang, Zhiyao; Wang, Shubing; Liang, Dong; Li, Heping; Liu, Yong

2018-03-01

We propose and demonstrate an approach that can achieve high-resolution quantization by employing soliton self-frequency shift and spectral compression. Our approach is based on a bi-directional comb-fiber architecture which is composed of a Sagnac-loop-based mirror and a comb-like combination of N sections of interleaved single-mode fibers and high nonlinear fibers. The Sagnac-loop-based mirror placed at the terminal of a bus line reflects the optical pulses back to the bus line to achieve additional N-stage spectral compression, thus single-stage soliton self-frequency shift (SSFS) and (2 N - 1)-stage spectral compression are realized in the bi-directional scheme. The fiber length in the architecture is numerically optimized, and the proposed quantization scheme is evaluated by both simulation and experiment in the case of N = 2. In the experiment, a quantization resolution of 6.2 bits is obtained, which is 1.2-bit higher than that of its uni-directional counterpart.

Active hexagonally segmented mirror to investigate new optical phasing technologies for segmented telescopes.

PubMed

Gonté, Frédéric; Dupuy, Christophe; Luong, Bruno; Frank, Christoph; Brast, Roland; Sedghi, Baback

2009-11-10

The primary mirror of the future European Extremely Large Telescope will be equipped with 984 hexagonal segments. The alignment of the segments in piston, tip, and tilt within a few nanometers requires an optical phasing sensor. A test bench has been designed to study four different optical phasing sensor technologies. The core element of the test bench is an active segmented mirror composed of 61 flat hexagonal segments with a size of 17 mm side to side. Each of them can be controlled in piston, tip, and tilt by three piezoactuators with a precision better than 1 nm. The context of this development, the requirements, the design, and the integration of this system are explained. The first results on the final precision obtained in closed-loop control are also presented.

Hypervelocity gun. [using both electric and chemical energy for projectile propulsion

NASA Technical Reports Server (NTRS)

Ford, F. C.; Biehl, A. J. (Inventor)

1965-01-01

A velocity amplifier system which uses both electric and chemical energy for projectile propulsion is provided in a compact hypervelocity gun suitable for laboratory use. A relatively heavy layer of a tamping material such as concrete encloses a loop of an electrically conductive material. An explosive charge at least partially surrounding the loop is adapted to collapse the loop upon detonation of the charge. A source of electricity charges the loop through two leads, and an electric switch which is activated by the charge explosive charge, disconnects the leads from the source of electricity and short circuits them. An opening in the tamping material extends to the loop and forms a barrel. The loop, necked down in the opening, forms the sabot on which the projectile is located. When the loop is electrically charged and the explosive detonated, the loop is short circuited and collapsed thus building up a magnetic field which acts as a sabot catcher. The sabot is detached from the loop and the sabot and projectile are accelerated to hypervelocity.

Mid-infrared source with 0.2 J pulse energy based on nonlinear conversion of Q-switched pulses in ZnGeP2.

PubMed

Haakestad, Magnus W; Fonnum, Helge; Lippert, Espen

2014-04-07

Mid-infrared (3-5 μm) pulses with high energy are produced using nonlinear conversion in a ZnGeP(2)-based master oscillator-power amplifier, pumped by a Q-switched cryogenic Ho:YLF oscillator. The master oscillator is based on an optical parametric oscillator with a V-shaped 3-mirror ring resonator, and the power amplifier is based on optical parametric amplification in large-aperture ZnGeP(2) crystals. Pulses with up to 212 mJ energy at 1 Hz repetition rate are obtained, with FWHM duration 15 ns and beam quality M(2) = 3.

Josephson Parametric Amplifer Based on a Cavity-Embedded Cooper Pair Transistor

NASA Astrophysics Data System (ADS)

Li, Juliang; Rimberg, A. J.

In this experiment a cavity-embedded Cooper-pair transistor (cCPT) is used as a Josephson parametric amplifier. The cCPT consists of a Cooper pair transistor placed at the voltage antinode of a 5.7 GHz shorted quarter-wave resonator so that the CPT provides a galvanic connection between the cavity's central conductor and ground plane, which forms a SQUID loop. Both the flux threading the loop as well as the gate charge can be modulated, and each can provide the parametric pumping. The reflected signal from the cCPT is further amplified by both SLUG and HEMT amplifiers for characterizing the parametric amplification. A first application of the parametric amplification is to improve the charge sensitivity of a single electron charge detector. This can be done either by pumping on a side band or by shifting the charge state of the cCPT near a bifurcation point. Stimulated emission has been also observed when the cCPT is pumped at twice the resonant frequency in the absence of an input signal. This could allow investigation of the dynamic Casimir effect as well as generation of non-classical photon states. Supported by Grants ARO W911NF-13-10377 and NSF DMR 1507400.

A single chip 2 Gbit/s clock recovery subsystem for digital communications

NASA Astrophysics Data System (ADS)

Hickling, Ronald M.

A self-contained clock recovery/data resynchronizer phase locked loop (PLL) for use in microwave and fiber optic digital communications has been fabricated using GaAs integrated circuit technology. The IC contains the analog and digital components for the PLL: an edge-triggered phase detector based on a 1.2 GHz phase/frequency comparator, an op amp for creating the loop filter, and a VCO based on a differential source-coupled pair amplifier.

Closed-loop carrier-envelope phase stabilization with an acousto-optic programmable dispersive filter.

PubMed

Forget, N; Canova, L; Chen, X; Jullien, A; Lopez-Martens, R

2009-12-01

We demonstrate arbitrary carrier-envelope (CE) phase control of femtosecond laser pulses by an acousto-optic programmable dispersive filter (AOPDF), with an accuracy better than pi/100 at a repetition rate of 1 kHz. We also demonstrate, for the first time to the best of our knowledge, 15 Hz closed-loop CE phase stabilization using an AOPDF inside a 1 kHz chirped pulse amplifier to correct for slow CE phase drifts.

Demonstration of the feasibility of large-port-count optical switching using a hybrid Mach-Zehnder interferometer-semiconductor optical amplifier switch module in a recirculating loop.

PubMed

Cheng, Q; Wonfor, A; Wei, J L; Penty, R V; White, I H

2014-09-15

For what we believe is the first time, the feasibility of large-port-count nanosecond-reconfiguration-time optical switches is demonstrated using a hybrid approach, where Mach-Zehnder interferometric (MZI) switches provide low-loss, high-speed routing with short semiconductor optical amplifiers (SOAs) being integrated to enhance extinction. By repeatedly passing signals through a monolithic hybrid dilated 2×2 switch module in a recirculating loop, the potential performance of high-port-count switches using the hybrid approach is demonstrated. Experimentally, a single pass switch penalty of only 0.1 dB is demonstrated for the 2×2 module, while even after seven passes through the switch, equivalent to a 128×128 router, a penalty of only 2.4 dB is recorded at a data rate of 10 Gb/s.

Multiwavelength ytterbium-Brillouin random Rayleigh feedback fiber laser

NASA Astrophysics Data System (ADS)

Wu, Han; Wang, Zinan; Fan, Mengqiu; Li, Jiaqi; Meng, Qingyang; Xu, Dangpeng; Rao, Yunjiang

2018-03-01

In this letter, we experimentally demonstrate the multiwavelength ytterbium-Brillouin random fiber laser for the first time, in the half-open cavity formed by a fiber loop mirror and randomly distributed Rayleigh mirrors. With a cladding-pumped ytterbium-doped fiber and a long TrueWave fiber, the narrow linewidth Brillouin pump can generate multiple Brillouin Stokes lines with hybrid ytterbium-Brillouin gain. Up to six stable channels with a spacing of about 0.06 nm are obtained. This work extends the operation wavelength of the multiwavelength Brillouin random fiber laser to the 1 µm band, and has potential in various applications.

An efficient and reliable DNA-based sex identification method for archaeological Pacific salmonid (Oncorhynchus spp.) remains.

PubMed

Royle, Thomas C A; Sakhrani, Dionne; Speller, Camilla F; Butler, Virginia L; Devlin, Robert H; Cannon, Aubrey; Yang, Dongya Y

2018-01-01

Pacific salmonid (Oncorhynchus spp.) remains are routinely recovered from archaeological sites in northwestern North America but typically lack sexually dimorphic features, precluding the sex identification of these remains through morphological approaches. Consequently, little is known about the deep history of the sex-selective salmonid fishing strategies practiced by some of the region's Indigenous peoples. Here, we present a DNA-based method for the sex identification of archaeological Pacific salmonid remains that integrates two PCR assays that each co-amplify fragments of the sexually dimorphic on the Y chromosome (sdY) gene and an internal positive control (Clock1a or D-loop). The first assay co-amplifies a 95 bp fragment of sdY and a 108 bp fragment of the autosomal Clock1a gene, whereas the second assay co-amplifies the same sdY fragment and a 249 bp fragment of the mitochondrial D-loop region. This method's reliability, sensitivity, and efficiency, were evaluated by applying it to 72 modern Pacific salmonids from five species and 75 archaeological remains from six Pacific salmonids. The sex identities assigned to each of the modern samples were concordant with their known phenotypic sex, highlighting the method's reliability. Applications of the method to dilutions of modern DNA samples indicate it can correctly identify the sex of samples with as little as ~39 pg of total genomic DNA. The successful sex identification of 70 of the 75 (93%) archaeological samples further demonstrates the method's sensitivity. The method's reliance on two co-amplifications that preferentially amplify sdY helps validate the sex identities assigned to samples and reduce erroneous identifications caused by allelic dropout and contamination. Furthermore, by sequencing the D-loop fragment used as a positive control, species-level and sex identifications can be simultaneously assigned to samples. Overall, our results indicate the DNA-based method reported in this study is a sensitive and reliable sex identification method for ancient salmonid remains.

Observation of laser beam profile progression inside an extended laser cavity

NASA Astrophysics Data System (ADS)

Wu, Frank F.; Farrell, Thomas C.

2013-03-01

This report presents the result of the laser beam profile progression in target-in-the-loop (TIL) system. This simulation experiment is to verify whether it is possible to form a tight hot spot similar to a single transversal mode in an extended laser cavity. Therefore, it is very important to observe the progression of the laser profile at a laser cavity mirror when a seeded high energy laser pulse is injected into the TIL system. The extended laser cavity is formed with a high reflectivity mirror on one end and an optical phase conjugated mirror as the second mirror, with potential disturbance media inside. The laser oscillation occurs only when it is triggered with a single frequency high energy laser pulse to overcome the threshold condition. With a laser cavity length of around 11 meters and a seeded laser pulse of 10 ns, we have been able to acquire and distinguish the laser beam profiles of each round-trip. Inserting a scattering media and other distortion elements can simulate atmospheric effects.

Method for removing tilt control in adaptive optics systems

DOEpatents

Salmon, Joseph Thaddeus

1998-01-01

A new adaptive optics system and method of operation, whereby the method removes tilt control, and includes the steps of using a steering mirror to steer a wavefront in the desired direction, for aiming an impinging aberrated light beam in the direction of a deformable mirror. The deformable mirror has its surface deformed selectively by means of a plurality of actuators, and compensates, at least partially, for existing aberrations in the light beam. The light beam is split into an output beam and a sample beam, and the sample beam is sampled using a wavefront sensor. The sampled signals are converted into corresponding electrical signals for driving a controller, which, in turn, drives the deformable mirror in a feedback loop in response to the sampled signals, for compensating for aberrations in the wavefront. To this purpose, a displacement error (gradient) of the wavefront is measured, and adjusted by a modified gain matrix, which satisfies the following equation: G'=(I-X(X.sup.T X).sup.-1 X.sup.T)G(I-A)

Design of a Compact, Bimorph Deformable Mirror-Based Adaptive Optics Scanning Laser Ophthalmoscope.

PubMed

He, Yi; Deng, Guohua; Wei, Ling; Li, Xiqi; Yang, Jinsheng; Shi, Guohua; Zhang, Yudong

2016-01-01

We have designed, constructed and tested an adaptive optics scanning laser ophthalmoscope (AOSLO) using a bimorph mirror. The simulated AOSLO system achieves diffraction-limited criterion through all the raster scanning fields (6.4 mm pupil, 3° × 3° on pupil). The bimorph mirror-based AOSLO corrected ocular aberrations in model eyes to less than 0.1 μm RMS wavefront error with a closed-loop bandwidth of a few Hz. Facilitated with a bimorph mirror at a stroke of ±15 μm with 35 elements and an aperture of 20 mm, the new AOSLO system has a size only half that of the first-generation AOSLO system. The significant increase in stroke allows for large ocular aberrations such as defocus in the range of ±600° and astigmatism in the range of ±200°, thereby fully exploiting the AO correcting capabilities for diseased human eyes in the future.

Ultrahigh-speed clock recovery with optical phase lock loop based on four-wave-mixing in a semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Kim, Dong Hwan; Kim, Sang Hyuck; Jo, Jae Cheol; Choi, Sang Sam

2000-08-01

A new phase lock loop (PLL) is proposed and demonstrated for clock recovery from 40 Gbps time-division-multiplexed (TDM) optical signal using simple optical phase lock loop circuit. The proposed clock recovery scheme improves the jitter effect in PLL circuit from the clock pulse laser of harmonically-mode locked fiber laser. The cross-correlation component between the optical signal and an optical clock pulse train is detected as a four-wave-mixing (FWM) signal generated in SOA. The lock-in frequency range of the clock recovery is found to be within 10 KHz.

Method and device for measuring single-shot transient signals

DOEpatents

Yin, Yan

2004-05-18

Methods, apparatus, and systems, including computer program products, implementing and using techniques for measuring multi-channel single-shot transient signals. A signal acquisition unit receives one or more single-shot pulses from a multi-channel source. An optical-fiber recirculating loop reproduces the one or more received single-shot optical pulses to form a first multi-channel pulse train for circulation in the recirculating loop, and a second multi-channel pulse train for display on a display device. The optical-fiber recirculating loop also optically amplifies the first circulating pulse train to compensate for signal losses and performs optical multi-channel noise filtration.

The Y-located gonadoblastoma gene TSPY amplifies its own expression through a positive feedback loop in prostate cancer cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kido, Tatsuo; Lau, Yun-Fai Chris, E-mail: Chris.Lau@UCSF.edu

2014-03-28

Highlights: • Y-encoded proto-oncoprotein TSPY amplifies its expression level via a positive feedback loop. • TSPY binds to the chromatin/DNA at exon 1 of TSPY gene. • TSPY enhances the gene expression in a TSPY exon 1 sequence dependent manner. • The conserved SET/NAP-domain is essential for TSPY transactivation. • Insights on probable mechanisms on TSPY exacerbation on cancer development in men. - Abstract: The testis-specific protein Y-encoded (TSPY) is a repetitive gene located on the gonadoblastoma region of the Y chromosome, and has been considered to be the putative gene for this oncogenic locus on the male-only chromosome. Itmore » is expressed in spermatogonial cells and spermatocytes in normal human testis, but abundantly in gonadoblastoma, testicular germ cell tumors and a variety of somatic cancers, including melanoma, hepatocellular carcinoma and prostate cancer. Various studies suggest that TSPY accelerates cell proliferation and growth, and promotes tumorigenesis. In this report, we show that TSPY could bind directly to the chromatin/DNA at exon 1 of its own gene, and greatly enhance the transcriptional activities of the endogenous gene in the LNCaP prostate cancer cells. Domain mapping analyses of TSPY have localized the critical and sufficient domain to the SET/NAP-domain. These results suggest that TSPY could efficiently amplify its expression and oncogenic functions through a positive feedback loop, and contribute to the overall tumorigenic processes when it is expressed in various human cancers.« less

STABILIZED OSCILLATOR

DOEpatents

Jessen, P.L.; Price, H.J.

1958-03-18

This patent relates to sine-wave generators and in particular describes a generator with a novel feedback circuit resulting in improved frequency stability. The generator comprises two triodes having a common cathode circuit connected to oscillate at a frequency and amplitude at which the loop galn of the circutt ls unity, and another pair of triodes having a common cathode circuit arranged as a conventional amplifier. A signal is conducted from the osciliator through a frequency selective network to the amplifier and fed back to the osciliator. The unique feature of the feedback circuit is the amplifier operates in the nonlinear portion of its tube characteristics thereby providing a relatively constant feedback voltage to the oscillator irrespective of the amplitude of its input signal.

Distributed meandering waveguides (DMWs) for novel photonic circuits (Conference Presentation)

NASA Astrophysics Data System (ADS)

Dag, Ceren B.; Anil, Mehmet Ali; Serpengüzel, Ali

2017-05-01

Meandering waveguide distributed feedback structures are novel integrated photonic lightwave and microwave circuit elements. Meandering waveguide distributed feedback structures with a variety of spectral responses can be designed for a variety of lightwave and microwave circuit element functions. Distributed meandering waveguide (DMW) structures [1] show a variety of spectral behaviors with respect to the number of meandering loop mirrors (MLMs) [2] used in their composition as well as their internal coupling constants (Cs). DMW spectral behaviors include Fano resonances, coupled resonator induced transparency (CRIT), notch, add-drop, comb, and hitless filters. What makes the DMW special is the self-coupling property intrinsic to the DMW's nature. The basic example of DMW's nature is motivated through the analogy between the so-called symmetric meandering resonator (SMR), which consists of two coupled MLMs, and the resonator enhanced Mach-Zehnder interferometer (REMZI) [3]. A SMR shows the same spectral characteristics of Fano resonances with its self-coupling property, similar to the single, distributed and binary self coupled optical waveguide (SCOW) resonators [4]. So far DMWs have been studied for their electric field intensity, phase [5] and phasor responses [6]. The spectral analysis is performed using the coupled electric field analysis and the generalization of single meandering loop mirrors to multiple meandering distributed feedback structures is performed with the transfer matrix method. The building block of the meandering waveguide structures, the meandering loop mirror (MLM), is the integrated analogue of the fiber optic loop mirrors. The meandering resonator (MR) is composed of two uncoupled MLM's. The meandering distributed feedback (MDFB) structure is the DFB of the MLM. The symmetric MR (SMR) is composed of two coupled MLM's, and has the characteristics of a Fano resonator in the general case, and tunable power divider or tunable hitless filter in special cases. The antisymmetric MR (AMR) is composed of two coupled MLM's. The AMR has the characteristics of an add-drop filter in the general case, and coupled resonator induced transparency (CRIT) filter in a special case. The symmetric MDFB (SMDFB) is composed of multiple coupled MLM's. The antisymmetric MDFB (AMDFB) is composed of multiple coupled MLM's. The SMDFB and AMDFB can be utilized as band-pass, Fano, or Lorentzian filters, or Rabi splitters. Distributed meandering waveguide elements with extremely rich spectral and phase responses can be designed with creative combinations of distributed meandering waveguides structures for various novel photonic circuits. References [1 ] C. B. Dağ, M. A. Anıl, and A. Serpengüzel, "Meandering Waveguide Distributed Feedback Lightwave Circuits," J. Lightwave Technol, vol. 33, no. 9, pp. 1691-1702, May 2015. [2] N. J. Doran and D. Wood, "Nonlinear-optical loop mirror," Opt. Lett. vol. 13, no. 1, pp. 56-58, Jan. 1988. [3] L. Zhou and A. W. Poon, "Fano resonance-based electrically reconfigurable add-drop filters in silicon microring resonator-coupled Mach-Zehnder interferometers," Opt. Lett. vol. 32, no. 7, pp. 781-783, Apr. 2007. [4] Z. Zou, L. Zhou, X. Sun, J. Xie, H. Zhu, L. Lu, X. Li, and J. Chen, "Tunable two-stage self-coupled optical waveguide resonators," Opt. Lett. vol. 38, no. 8, pp. 1215-1217, Apr. 2013. [5] C. B. Dağ, M. A. Anıl, and A. Serpengüzel, "Novel distributed feedback lightwave circuit elements," in Proc. SPIE, San Francisco, 2015, vol. 9366, p. 93660A. [6] C. B. Dağ, M. A. Anıl, and A. Serpengüzel, "Meandering Waveguide Distributed Feedback Lightwave Elements: Phasor Diagram Analysis," in Proc. PIERS, Prague, 1986-1990 (2015).

Design, fabrication, and testing of duralumin zoom mirror with variable thickness

NASA Astrophysics Data System (ADS)

Hui, Zhao; Xie, Xiaopeng; Xu, Liang; Ding, Jiaoteng; Shen, Le; Liu, Meiying; Gong, Jie

2016-10-01

Zoom mirror is a kind of active optical component that can change its curvature radius dynamically. Normally, zoom mirror is used to correct the defocus and spherical aberration caused by thermal lens effect to improve the beam quality of high power solid-state laser since that component was invented. Recently, the probable application of zoom mirror in realizing non-moving element optical zoom imaging in visible band has been paid much attention. With the help of optical leveraging effect, the slightly changed local optical power caused by curvature variation of zoom mirror could be amplified to generate a great alteration of system focal length without moving elements involved in, but in this application the shorter working wavelength and higher surface figure accuracy requirement make the design and fabrication of such a zoom mirror more difficult. Therefore, the key to realize non-moving element optical zoom imaging in visible band lies in zoom mirror which could provide a large enough saggitus variation while still maintaining a high enough surface figure. Although the annular force based actuation could deform a super-thin mirror having a constant thickness to generate curvature variation, it is quite difficult to maintain a high enough surface figure accuracy and this phenomenon becomes even worse when the diameter and the radius-thickness ratio become bigger. In this manuscript, by combing the pressurization based actuation with a variable thickness mirror design, the purpose of obtaining large saggitus variation and maintaining quite good surface figure accuracy at the same time could be achieved. A prototype zoom mirror with diameter of 120mm and central thickness of 8mm is designed, fabricated and tested. Experimental results demonstrate that the zoom mirror having an initial surface figure accuracy superior to 1/50λ could provide at least 21um saggitus variation and after finishing the curvature variation its surface figure accuracy could still be superior to 1/20λ, which proves that the effectiveness of the theoretical design.

Millijoule-level 20 ps Nd:YAG oscillator-amplifier laser system for investigation of stimulated Raman scattering and optical parametric generation

NASA Astrophysics Data System (ADS)

Jelínek, Michal; Kubecek, Vàclav

2012-06-01

We report on quasi-continuously pumped oscillator-amplifier laser system. The laser oscillator was based on highly 2.4 at.% doped crystalline Nd:YAG in a bounce geometry and passively mode locked by a semiconductor saturable absorber mirror. Using the cavity dumping technique, 19 ps pulses with the energy of 20 μJ and Gaussian spatial beam profile were generated directly from the oscillator at the repetition rate up to 50 Hz. For applications requiring more energetic pulses the amplification was studied using either an identical highly doped Nd:YAG module in bounce geometry or flashlamp pumped Nd:YAG laser rod. Using compact all diode pumped oscillator-amplifier system, 130 μJ pulses were generated. The flashlamp pumped amplifier with 100 mm long Nd:YAG enabled to obtain higher energy. In the single pass configuration the pulse was amplified to 4.5 mJ, using the double pass configuration the pulse energy was further increased up to 20 mJ with the duration of 25 ps at 10 Hz. The developed laser system was used for investigation of stimulated Raman scattering in Strontium Barium Niobate and optical parametric generation in CdSiP2.

Diode pumped, regenerative Nd:YAG ring amplifier for space application

NASA Technical Reports Server (NTRS)

Coyle, D. B.; Kay, Richard B.; Degnan, John J.; Krebs, Danny J.; Seery, Bernard D.

1992-01-01

The study reviews the research and development of a prototype laser used to study one possible method of short-pulse production and amplification, in particular, a pulsed Nd:YAG ring laser pumped by laser diode arrays and injected seeded by a 100-ps source. The diode array pumped, regenerative amplifier consists of only five optical elements, two mirrors, one thin film polarizer, one Nd:YAG crystal, and one pockels cell. The pockels cell performed both as a Q-switch and a cavity dumper for amplified pulse ejection through the thin film polarizer. The total optical efficiency was low principally due to the low gain provided by the 2-bar pumped laser head. After comparison with a computer model, a real seed threshold of about 10 exp -15 J was achieved because only about 0.1 percent of the injected energy mode-matched with the ring.

Device for translating negative film image to a line scan

DOEpatents

Dutton, G.W.

1998-05-19

A negative film reader records high-resolution optical density changes across negative film radiographic images to allow precise image dimensions to be determined. A laser light source capable of high-resolution focusing is passed through an intensity control filter, focused by a lens, and reflected off a mirror to focus in the plane of the negative film. The light transmitted through the film is collected by a second lens and directed to a photo diode detector which senses the transmitted intensity. The output of the photo diode signal amplifier is sent to the Y-axis input of an X-Y recorder. The film sample is transported in a plane perpendicular to the beam axis by means of a slide. The film position is monitored, with the signal amplified and recorded as the X-axis on the X-Y recorder. The linear dimensions and positions of image components can be determined by direct measurement of the amplified recording.

James Webb Space Telescope optical simulation testbed IV: linear control alignment of the primary segmented mirror

NASA Astrophysics Data System (ADS)

Egron, Sylvain; Soummer, Rémi; Lajoie, Charles-Philippe; Bonnefois, Aurélie; Long, Joseph; Michau, Vincent; Choquet, Elodie; Ferrari, Marc; Leboulleux, Lucie; Levecq, Olivier; Mazoyer, Johan; N'Diaye, Mamadou; Perrin, Marshall; Petrone, Peter; Pueyo, Laurent; Sivaramakrishnan, Anand

2017-09-01

The James Webb Space Telescope (JWST) Optical Simulation Testbed (JOST) is a tabletop experiment designed to study wavefront sensing and control for a segmented space telescope, such as JWST. With the JWST Science and Operations Center co-located at STScI, JOST was developed to provide both a platform for staff training and to test alternate wavefront sensing and control strategies for independent validation or future improvements beyond the baseline operations. The design of JOST reproduces the physics of JWST's three-mirror anastigmat (TMA) using three custom aspheric lenses. It provides similar quality image as JWST (80% Strehl ratio) over a field equivalent to a NIRCam module, but at 633 nm. An Iris AO segmented mirror stands for the segmented primary mirror of JWST. Actuators allow us to control (1) the 18 segments of the segmented mirror in piston, tip, tilt and (2) the second lens, which stands for the secondary mirror, in tip, tilt and x, y, z positions. We present the most recent experimental results for the segmented mirror alignment. Our implementation of the Wavefront Sensing (WFS) algorithms using phase diversity is tested on simulation and experimentally. The wavefront control (WFC) algorithms, which rely on a linear model for optical aberrations induced by misalignment of the secondary lens and the segmented mirror, are tested and validated both on simulations and experimentally. In this proceeding, we present the performance of the full active optic control loop in presence of perturbations on the segmented mirror, and we detail the quality of the alignment correction.

Nutating subreflector for a millimeter wave telescope

NASA Astrophysics Data System (ADS)

Radford, Simon J. E.; Boynton, Paul; Melchiorri, Francesco

1990-03-01

Nutating a Cassegrain telescope's secondary mirror is a convenient method of steering the telescope beam through a small angle. This principle has been used to construct a high-performance beam switch for a millimeter wave telescope. A low mass, graphite-epoxy laminate secondary mirror is driven by linear electric motors operated in a frequency compensated control loop. By design, the nutator exerts little net oscillating torque on the telescope structure, resulting in virtually vibration free operation. The inherent versatility of beam switching by subreflector nutation permits a variety of switching waveforms to be tested without making any hardware changes. The nutator can shift the telescope beam by 10 arcminutes, a 1.25 deg rotation of the 75-cm-diam secondary mirror, in an interval of 8 ms and it can sustain a switching frequency of 10 Hz.

Performance evaluation of coherent free space optical communications with a double-stage fast-steering-mirror adaptive optics system depending on the Greenwood frequency.

PubMed

Liu, Wei; Yao, Kainan; Huang, Danian; Lin, Xudong; Wang, Liang; Lv, Yaowen

2016-06-13

The Greenwood frequency (GF) is influential in performance improvement for the coherent free space optical communications (CFSOC) system with a closed-loop adaptive optics (AO) unit. We analyze the impact of tilt and high-order aberrations on the mixing efficiency (ME) and bit-error-rate (BER) under different GF. The root-mean-square value (RMS) of the ME related to the RMS of the tilt aberrations, and the GF is derived to estimate the volatility of the ME. Furthermore, a numerical simulation is applied to verify the theoretical analysis, and an experimental correction system is designed with a double-stage fast-steering-mirror and a 97-element continuous surface deformable mirror. The conclusions of this paper provide a reference for designing the AO system for the CFSOC system.

On-sky performance of the Zernike phase contrast sensor for the phasing of segmented telescopes.

PubMed

Surdej, Isabelle; Yaitskova, Natalia; Gonte, Frederic

2010-07-20

The Zernike phase contrast method is a novel technique to phase the primary mirrors of segmented telescopes. It has been tested on-sky on a unit telescope of the Very Large Telescope with a segmented mirror conjugated to the primary mirror to emulate a segmented telescope. The theoretical background of this sensor and the algorithm used to retrieve the piston, tip, and tilt information are described. The performance of the sensor as a function of parameters such as star magnitude, seeing, and integration time is discussed. The phasing accuracy has always been below 15 nm root mean square wavefront error under normal conditions of operation and the limiting star magnitude achieved on-sky with this sensor is 15.7 in the red, which would be sufficient to phase segmented telescopes in closed-loop during observations.

High-speed wavefront control using MEMS micromirrors

NASA Astrophysics Data System (ADS)

Bifano, T. G.; Stewart, J. B.

2005-08-01

Over the past decade, a number of electrostatically-actuated MEMS deformable mirror devices have been used for adaptive control in beam-forming and imaging applications. One architecture that has been widely used is the silicon device developed by Boston University, consisting of a continuous or segmented mirror supported by post attachments to an array of parallel plate electrostatic actuators. MEMS deformable mirrors and segmented mirrors with up to 1024 of these actuators have been used in open loop and closed loop control systems to control wavefront errors. Frame rates as high as 11kHz have been demonstrated. Mechanically, the actuators used in this device exhibit a first-mode resonant frequency that is in the range of many tens of kilohertz up to a few hundred kilohertz. Viscous air damping has been found to limit operation at such high frequencies in air at standard pressure. Some applications in high-speed tracking and beam-forming could benefit from increased speed. In this paper, several approaches to achieving critically-damped performance with such MEMS DMs are detailed, and theoretical and experimental results are presented. One approach is to seal the MEMS DM in a full or partial vacuum environment, thereby affecting air damping. After vacuum sealing the device's predicted resonant behavior at tens of kilohertz was observed. In vacuum, the actuator's intrinsic material damping is quite small, resulting in considerable oscillation in step response. To alleviate this problem, a two-step actuation algorithm was employed. Precise control of a single actuator frequencies up to 100kHz without overshoot was demonstrated using this approach. Another approach to increasing actuation speed was to design actuators that reduce air damping effects. This is also demonstrated in the paper.

Multiple feedback control apparatus for power conditioning equipment

NASA Technical Reports Server (NTRS)

Biess, John (Inventor); Yu, Yuan (Inventor)

1977-01-01

An improved feedback control system to govern the cyclic operation of the power switch of a non-dissipative power conditioning equipment. The apparatus includes two or three control loops working in unison. The first causes the output DC level to be compared with a reference, and the error amplified for control purposes. The second utilizes the AC component of the voltage across the output filter inductor or the current through the output filter capacitor, and the third loop senses the output transients.

Miniature Fourier transform spectrometer with a dual closed-loop controlled electrothermal micromirror.

PubMed

Han, Fengtian; Wang, Wei; Zhang, Xiaoyang; Xie, Huikai

2016-10-03

A large piston-displacement electrothermal micromirror with closed-loop control of both piston scan and tilting of the mirror plate is demonstrated for use in a miniature Fourier transform spectrometer. Constant scan velocity in an ultra large piston scan range has been demonstrated by the proposed closed-loop piston control scheme which can be easily implemented without considerably increasing system complexity. The experimental results show that the usable linear scan range generated by the micromirror has been extended up to 505 μm. The measured spectral resolution in a compact spectrometer reaches 20 cm^-1, or 0.57 nm at 532 nm wavelength. Compared to other presented systems, this microspectrometer will benefit from the closed-loop thermal actuator approach utilizing both the piston servo and tilt control to provide more consistent spectral response, improved spectral resolution and enhanced robustness to disturbances.

A Mixed Mode Cochlear Amplifier Including Neural Feedback

NASA Astrophysics Data System (ADS)

Flax, Matthew R.; Holmes, W. Harvey

2011-11-01

The mixed mode cochlear amplifier (MMCA) model is derived from the physiology of the cochlea. It is comprised of three main elements of the peripheral hearing system: the cochlear mechanics, hair cell motility, and neurophysiology. This model expresses both active compression wave and active traveling wave modes of operation. The inclusion of a neural loop with a time delay, and a new paradigm for the mechanical response of the outer hair cells, are believed to be unique features of the MMCA. These elements combine to form an active feedback loop to constitute the cochlear amplifier, whose input is a passive traveling wave vibration. The result is a cycle-by-cycle amplifier with nonlinear response. This system can assume an infinite number of different operating states. The stable state and the first few amplitude-limited unstable (Hopf-bifurcated) states are significant in describing the operation of the peripheral hearing system. A hierarchy of models can be constructed from this concept, depending on the amount of detail included. The simplest model of the MMCA is a nonlinear delay line resonator. It was found that even this simple MMCA version can explain a large number of hearing phenomena, at least qualitatively. This paper concentrates on explaining the fractional octave shift from the living to postmortem response in terms of the new model. Other mechanical, hair cell and neurological phenomena can also be accounted for by the MMCA, including two-tone suppression behavior, distortion product responses, otoacoustic emissions and neural spontaneous rates.

Multilayer active shell mirrors for space telescopes

NASA Astrophysics Data System (ADS)

Steeves, John; Jackson, Kathryn; Pellegrino, Sergio; Redding, David; Wallace, J. Kent; Bradford, Samuel Case; Barbee, Troy

2016-07-01

A novel active mirror technology based on carbon fiber reinforced polymer (CFRP) substrates and replication techniques has been developed. Multiple additional layers are implemented into the design serving various functions. Nanolaminate metal films are used to provide a high quality reflective front surface. A backing layer of thin active material is implemented to provide the surface-parallel actuation scheme. Printed electronics are used to create a custom electrode pattern and flexible routing layer. Mirrors of this design are thin (< 1.0 mm), lightweight (2.7 kg/m2), and have large actuation capabilities. These capabilities, along with the associated manufacturing processes, represent a significant change in design compared to traditional optics. Such mirrors could be used as lightweight primaries for small CubeSat-based telescopes or as meter-class segments for future large aperture observatories. Multiple mirrors can be produced under identical conditions enabling a substantial reduction in manufacturing cost and complexity. An overview of the mirror design and manufacturing processes is presented. Predictions on the actuation performance have been made through finite element simulations demonstrating correctabilities on the order of 250-300× for astigmatic modes with only 41 independent actuators. A description of the custom metrology system used to characterize the active mirrors is also presented. The system is based on a Reverse Hartmann test and can accommodate extremely large deviations in mirror figure (> 100 μm PV) down to sub-micron precision. The system has been validated against several traditional techniques including photogrammetry and interferometry. The mirror performance has been characterized using this system, as well as closed-loop figure correction experiments on 150 mm dia. prototypes. The mirrors have demonstrated post-correction figure accuracies of 200 nm RMS (two dead actuators limiting performance).

Design of a Programmable Gain, Temperature Compensated Current-Input Current-Output CMOS Logarithmic Amplifier.

PubMed

Ming Gu; Chakrabartty, Shantanu

2014-06-01

This paper presents the design of a programmable gain, temperature compensated, current-mode CMOS logarithmic amplifier that can be used for biomedical signal processing. Unlike conventional logarithmic amplifiers that use a transimpedance technique to generate a voltage signal as a logarithmic function of the input current, the proposed approach directly produces a current output as a logarithmic function of the input current. Also, unlike a conventional transimpedance amplifier the gain of the proposed logarithmic amplifier can be programmed using floating-gate trimming circuits. The synthesis of the proposed circuit is based on the Hart's extended translinear principle which involves embedding a floating-voltage source and a linear resistive element within a translinear loop. Temperature compensation is then achieved using a translinear-based resistive cancelation technique. Measured results from prototypes fabricated in a 0.5 μm CMOS process show that the amplifier has an input dynamic range of 120 dB and a temperature sensitivity of 230 ppm/°C (27 °C- 57°C), while consuming less than 100 nW of power.

Amplifiers dedicated for large area SiC photodiodes

NASA Astrophysics Data System (ADS)

Doroz, P.; Duk, M.; Korwin-Pawlowski, M. L.; Borecki, M.

2016-09-01

Large area SiC photodiodes find applications in optoelectronic sensors working at special conditions. These conditions include detection of UV radiation in harsh environment. Moreover, the mentioned sensors have to be selective and resistant to unwanted signals. For this purpose, the modulation of light at source unit and the rejection of constant current and low frequency component of signal at detector unit are used. The popular frequency used for modulation in such sensor is 1kHz. The large area photodiodes are characterized by a large capacitance and low shunt resistance that varies with polarization of the photodiode and can significantly modify the conditions of signal pre-amplification. In this paper two pre-amplifiers topology are analyzed: the transimpedance amplifier and the non-inverting voltage to voltage amplifier with negative feedback. The feedback loops of both pre-amplifiers are equipped with elements used for initial constant current and low frequency signals rejections. Both circuits are analyzed and compared using simulation and experimental approaches.

Cavity-enhanced optical bottle beam as a mechanical amplifier

NASA Astrophysics Data System (ADS)

Freegarde, Tim; Dholakia, Kishan

2002-07-01

We analyze the resonant cavity enhancement of a hollow ``optical bottle beam'' for the dipole-force trapping of dark-field-seeking species. We first improve upon the basic bottle beam by adding further Laguerre-Gaussian components to deepen the confining potential. Each of these components itself corresponds to a superposition of transverse cavity modes, which are then enhanced simultaneously in a confocal cavity to produce a deep optical trap needing only a modest incident power. The response of the trapping field to displacement of the cavity mirrors offers an unusual form of mechanical amplifier in which the Gouy phase shift produces an optical Vernier scale between the Laguerre-Gaussian beam components.

Focal plane infrared readout circuit

NASA Technical Reports Server (NTRS)

Pain, Bedabrata (Inventor)

2002-01-01

An infrared imager, such as a spectrometer, includes multiple infrared photodetectors and readout circuits for reading out signals from the photodetectors. Each readout circuit includes a buffered direct injection input circuit including a differential amplifier with active feedback provided through an injection transistor. The differential amplifier includes a pair of input transistors, a pair of cascode transistors and a current mirror load. Photocurrent from a photodetector can be injected onto an integration capacitor in the readout circuit with high injection efficiency at high speed. A high speed, low noise, wide dynamic range linear infrared multiplexer array for reading out infrared detectors with large capacitances can be achieved even when short exposure times are used. The effect of image lag can be reduced.

An AC modulated near infrared gain calibration system for a "Violin-Mode" transimpedance amplifier, intended for advanced LIGO suspensions.

PubMed

Lockerbie, N A; Tokmakov, K V

2016-07-01

The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a "tall-thin" rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse "Violin-Mode" vibrations of such a fibre, via the oscillatory movement of the shadow cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor's DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor's more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz-300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m(-1) was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain ratio of 922.5 for this sensor, at 500 Hz, translated into a maximum Violin-Mode (AC) responsivity of (1.16 ± 0.05) MV m(-1), at that frequency.

Stellar figure sensor

NASA Technical Reports Server (NTRS)

Peters, W. N.

1973-01-01

A compilation of analytical and experimental data is presented concerning the stellar figure sensor. The sensor is an interferometric device which is located in the focal plane of an orbiting large space telescope (LST). The device was designed to perform interferometry on the optical wavefront of a single star after it has propagated through the LST. An analytical model of the device was developed and its accuracy was verified by an operating laboratory breadboard. A series of linear independent control equations were derived which define the operations required for utilizing a focal plane figure sensor in the control loop for the secondary mirror position and for active control of the primary mirror.

Simple piezoelectric-actuated mirror with 180 kHz servo bandwidth.

PubMed

Briles, Travis C; Yost, Dylan C; Cingöz, Arman; Ye, Jun; Schibli, Thomas R

2010-05-10

We present a high bandwidth piezoelectric-actuated mirror for length stabilization of an optical cavity. The actuator displays a transfer function with a flat amplitude response and greater than 135 masculine phase margin up to 200 kHz, allowing a 180 kHz unity gain frequency to be achieved in a closed servo loop. To the best of our knowledge, this actuator has achieved the largest servo bandwidth for a piezoelectric transducer (PZT). The actuator should be very useful in a wide variety of applications requiring precision control of optical lengths, including laser frequency stabilization, optical interferometers, and optical communications. (c) 2010 Optical Society of America.

A real-time sub-μrad laser beam tracking system

NASA Astrophysics Data System (ADS)

Buske, Ivo; Schragner, Ralph; Riede, Wolfgang

2007-10-01

We present a rugged and reliable real-time laser beam tracking system operating with a high speed, high resolution piezo-electric tip/tilt mirror. Characteristics of the piezo mirror and position sensor are investigated. An industrial programmable automation controller is used to develop a real-time digital PID controller. The controller provides a one million field programmable gate array (FPGA) to realize a high closed-loop frequency of 50 kHz. Beam tracking with a root-mean-squared accuracy better than 0.15 μrad has been laboratory confirmed. The system is intended as an add-on module for established mechanical mrad tracking systems.

Closed-loop optical stabilization and digital image registration in adaptive optics scanning light ophthalmoscopy

PubMed Central

Yang, Qiang; Zhang, Jie; Nozato, Koji; Saito, Kenichi; Williams, David R.; Roorda, Austin; Rossi, Ethan A.

2014-01-01

Eye motion is a major impediment to the efficient acquisition of high resolution retinal images with the adaptive optics (AO) scanning light ophthalmoscope (AOSLO). Here we demonstrate a solution to this problem by implementing both optical stabilization and digital image registration in an AOSLO. We replaced the slow scanning mirror with a two-axis tip/tilt mirror for the dual functions of slow scanning and optical stabilization. Closed-loop optical stabilization reduced the amplitude of eye-movement related-image motion by a factor of 10–15. The residual RMS error after optical stabilization alone was on the order of the size of foveal cones: ~1.66–2.56 μm or ~0.34–0.53 arcmin with typical fixational eye motion for normal observers. The full implementation, with real-time digital image registration, corrected the residual eye motion after optical stabilization with an accuracy of ~0.20–0.25 μm or ~0.04–0.05 arcmin RMS, which to our knowledge is more accurate than any method previously reported. PMID:25401030

A closed-loop phase-locked interferometer for wide bandwidth position sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleming, Andrew J., E-mail: Andrew.Fleming@Newcastle.edu.au; Routley, Ben S., E-mail: Ben.Routley@Newcastle.edu.au

This article describes a position sensitive interferometer with closed-loop control of the reference mirror. A calibrated nanopositioner is used to lock the interferometer phase to the most sensitive point in the interferogram. In this configuration, large low-frequency movements of the sensor mirror can be detected from the control signal applied to the nanopositioner and high-frequency short-range signals can be measured directly from the photodiode. It is demonstrated that these two signals are complementary and can be summed to find the total displacement. The resulting interferometer has a number of desirable characteristics: it is optically simple, does not require polarization ormore » modulation to detect the direction of motion, does not require fringe-counting or interpolation electronics, and has a bandwidth equal to that of the photodiode. Experimental results demonstrate the frequency response analysis of a high-speed positioning stage. The proposed instrument is ideal for measuring the frequency response of nanopositioners, electro-optical components, MEMs devices, ultrasonic devices, and sensors such as surface acoustic wave detectors.« less

Possible Quantum Absorber Effects in Cortical Synchronization

NASA Astrophysics Data System (ADS)

Kämpf, Uwe

The Wheeler-Feynman transactional "absorber" approach was proposed originally to account for anomalous resonance coupling between spatio-temporally distant measurement partners in entangled quantum states of so-called Einstein-Podolsky-Rosen paradoxes, e.g. of spatio-temporal non-locality, quantum teleportation, etc. Applied to quantum brain dynamics, however, this view provides an anticipative resonance coupling model for aspects of cortical synchronization and recurrent visual action control. It is proposed to consider the registered activation patterns of neuronal loops in so-called synfire chains not as a result of retarded brain communication processes, but rather as surface effects of a system of standing waves generated in the depth of visual processing. According to this view, they arise from a counterbalance between the actual input's delayed bottom-up data streams and top-down recurrent information-processing of advanced anticipative signals in a Wheeler-Feynman-type absorber mode. In the framework of a "time-loop" model, findings about mirror neurons in the brain cortex are suggested to be at least partially associated with temporal rather than spatial mirror functions of visual processing, similar to phase conjugate adaptive resonance-coupling in nonlinear optics.

Quadrature demultiplexing using a degenerate vector parametric amplifier.

PubMed

Lorences-Riesgo, Abel; Liu, Lan; Olsson, Samuel L I; Malik, Rohit; Kumpera, Aleš; Lundström, Carl; Radic, Stojan; Karlsson, Magnus; Andrekson, Peter A

2014-12-01

We report on quadrature demultiplexing of a quadrature phase-shift keying (QPSK) signal into two cross-polarized binary phase-shift keying (BPSK) signals with negligible penalty at bit-error rate (BER) equal to 10(-9). The all-optical quadrature demultiplexing is achieved using a degenerate vector parametric amplifier operating in phase-insensitive mode. We also propose and demonstrate the use of a novel and simple phase-locked loop (PLL) scheme based on detecting the envelope of one of the signals after demultiplexing in order to achieve stable quadrature decomposition.

Space Adaptation of Active Mirror Segment Concepts

NASA Technical Reports Server (NTRS)

Ames, Gregory H.

1999-01-01

This report summarizes the results of a three year effort by Blue Line Engineering Co. to advance the state of segmented mirror systems in several separate but related areas. The initial set of tasks were designed to address the issues of system level architecture, digital processing system, cluster level support structures, and advanced mirror fabrication concepts. Later in the project new tasks were added to provide support to the existing segmented mirror testbed at Marshall Space Flight Center (MSFC) in the form of upgrades to the 36 subaperture wavefront sensor. Still later, tasks were added to build and install a new system processor based on the results of the new system architecture. The project was successful in achieving a number of important results. These include the following most notable accomplishments: 1) The creation of a new modular digital processing system that is extremely capable and may be applied to a wide range of segmented mirror systems as well as many classes of Multiple Input Multiple Output (MIMO) control systems such as active structures or industrial automation. 2) A new graphical user interface was created for operation of segmented mirror systems. 3) The development of a high bit rate serial data loop that permits bi-directional flow of data to and from as many as 39 segments daisy-chained to form a single cluster of segments. 4) Upgrade of the 36 subaperture Hartmann type Wave Front Sensor (WFS) of the Phased Array Mirror, Extendible Large Aperture (PAMELA) testbed at MSFC resulting in a 40 to 5OX improvement in SNR which in turn enabled NASA personnel to achieve many significant strides in improved closed-loop system operation in 1998. 5) A new system level processor was built and delivered to MSFC for use with the PAMELA testbed. This new system featured a new graphical user interface to replace the obsolete and non-supported menu system originally delivered with the PAMELA system. The hardware featured Blue Line's new stackable processing system which included fiber optic data links, a WFS digital interface, and a very compact and reliable electronics package. The project also resulted in substantial advances in the evolution of concepts for integrated structures to be used to support clusters of segments while also serving as the means to distribute power, timing, and data communications resources. A prototype cluster base was built and delivered that would support a small array of 7 cm mirror segments. Another conceptual design effort led to substantial progress in the area of laminated silicon mirror segments. While finished mirrors were never successfully produced in this exploratory effort, the basic feasibility of the concept was established through a significant amount of experimental development in microelectronics processing laboratories at the University of Colorado in Colorado Springs. Ultimately lightweighted aluminum mirrors with replicated front surfaces were produced and delivered as part of a separate contract to develop integrated segmented mirror assemblies. Overall the project was very successful in advancing segmented mirror system architectures on several fronts. In fact, the results of this work have already served as the basic foundation for the system architectures of several projects proposed by Blue Line for different missions and customers. These include the NMSD and AMSD procurements for NASA's Next Generation Space Telescope, the HET figure maintenance system, and the 1 meter FAST telescope project.

Mirror-image duplication of the primary axis and heart in Xenopus embryos by the overexpression of Msx-1 gene.

PubMed

Chen, Y; Solursh, M

1995-10-01

The Msx-1 gene (formerly known as Hox-7) is a member of a discrete subclass of homeobox-containing genes. Examination of the expression pattern of Msx-1 in murine and avian embryos suggests that this gene may be involved in the regionalization of the medio-lateral axis during earlier development. We have examined the possible functions of Xenopus Msx-1 during early Xenopus embryonic development by overexpression of the Msx-1 gene. Overexpression of Msx-1 causes a left-right mirror-image duplication of primary axial structures, including notochord, neural tube, somites, suckers, and foregut. The embryonic developing heart is also mirror-image duplicated, including looping directions and polarity. These results indicate that Msx-1 may be involved in the mesoderm formation as well as left-right patterning in the early Xenopus embryonic development.

Streptavidin-mirror DNA tetrahedron hybrid as a platform for intracellular and tumor delivery of enzymes.

PubMed

Kim, Kyoung-Ran; Hwang, Dohyeon; Kim, Juhyeon; Lee, Chang-Yong; Lee, Wonseok; Yoon, Dae Sung; Shin, Dongyun; Min, Sun-Joon; Kwon, Ick Chan; Chung, Hak Suk; Ahn, Dae-Ro

2018-06-28

Despite the extremely high substrate specificity and catalytically amplified activity of enzymes, the lack of efficient cellular internalization limits their application as therapeutics. To overcome this limitation and to harness enzymes as practical biologics for targeting intracellular functions, we developed the streptavidin-mirror DNA tetrahedron hybrid as a platform for intracellular delivery of various enzymes. The hybrid consists of streptavidin, which provides a stoichiometrically controlled loading site for the enzyme cargo and an L-DNA (mirror DNA) tetrahedron, which provides the intracellular delivery potential. Due to the cell-penetrating ability of the mirror DNA tetrahedron of this hybrid, enzymes loaded on streptavidin can be efficiently delivered into the cells, intracellularly expressing their activity. In addition, we demonstrate tumor delivery of enzymes in an animal model by utilizing the potential of the hybrid to accumulate in tumors. Strikingly, the hybrid is able to transfer the apoptotic enzyme specifically into tumor cells, leading to strong suppression of tumor growth without causing significant damage to other tissues. These results suggest that the hybrid may allow anti-proliferative enzymes and proteins to be utilized as anticancer drugs. Copyright © 2018 Elsevier B.V. All rights reserved.

Correction of large amplitude wavefront aberrations

NASA Astrophysics Data System (ADS)

Cornelissen, S. A.; Bierden, P. A.; Bifano, T. G.; Webb, R. H.; Burns, S.; Pappas, S.

2005-12-01

Recently, a number of research groups around the world have developed ophthalmic instruments capable of in vivo diffraction limited imaging of the human retina. Adaptive optics was used in these systems to compensate for the optical aberrations of the eye and provide high contrast, high resolution images. Such compensation uses a wavefront sensor and a wavefront corrector (usually a deformable mirror) coordinated in a closed- loop control system that continuously works to counteract aberrations. While those experiments produced promising results, the deformable mirrors have had insufficient range of motion to permit full correction of the large amplitude aberrations of the eye expected in a normal population of human subjects. Other retinal imaging systems developed to date with MEMS (micro-electromechanical systems) DMs suffer similar limitations. This paper describes the design, manufacture and testing of a 6um stroke polysilicon surface micromachined deformable mirror that, coupled with an new optical method to double the effective stroke of the MEMS-DM, will permit diffraction-limited retinal imaging through dilated pupils in at least 90% of the human population. A novel optical design using spherical mirrors provides a double pass of the wavefront over the deformable mirror such that a 6um mirror displacement results in 12um of wavefront compensation which could correct for 24um of wavefront error. Details of this design are discussed. Testing of the effective wavefront modification was performed using a commercial wavefront sensor. Results are presented demonstrating improvement in the amplitude of wavefront control using an existing high degree of freedom MEMS deformable mirror.

High power, high beam quality regenerative amplifier

DOEpatents

Hackel, L.A.; Dane, C.B.

1993-08-24

A regenerative laser amplifier system generates high peak power and high energy per pulse output beams enabling generation of X-rays used in X-ray lithography for manufacturing integrated circuits. The laser amplifier includes a ring shaped optical path with a limited number of components including a polarizer, a passive 90 degree phase rotator, a plurality of mirrors, a relay telescope, and a gain medium, the components being placed close to the image plane of the relay telescope to reduce diffraction or phase perturbations in order to limit high peak intensity spiking. In the ring, the beam makes two passes through the gain medium for each transit of the optical path to increase the amplifier gain to loss ratio. A beam input into the ring makes two passes around the ring, is diverted into an SBS phase conjugator and proceeds out of the SBS phase conjugator back through the ring in an equal but opposite direction for two passes, further reducing phase perturbations. A master oscillator inputs the beam through an isolation cell (Faraday or Pockels) which transmits the beam into the ring without polarization rotation. The isolation cell rotates polarization only in beams proceeding out of the ring to direct the beams out of the amplifier. The diffraction limited quality of the input beam is preserved in the amplifier so that a high power output beam having nearly the same diffraction limited quality is produced.

High power, high beam quality regenerative amplifier

DOEpatents

Hackel, Lloyd A.; Dane, Clifford B.

1993-01-01

A regenerative laser amplifier system generates high peak power and high energy per pulse output beams enabling generation of X-rays used in X-ray lithography for manufacturing integrated circuits. The laser amplifier includes a ring shaped optical path with a limited number of components including a polarizer, a passive 90 degree phase rotator, a plurality of mirrors, a relay telescope, and a gain medium, the components being placed close to the image plane of the relay telescope to reduce diffraction or phase perturbations in order to limit high peak intensity spiking. In the ring, the beam makes two passes through the gain medium for each transit of the optical path to increase the amplifier gain to loss ratio. A beam input into the ring makes two passes around the ring, is diverted into an SBS phase conjugator and proceeds out of the SBS phase conjugator back through the ring in an equal but opposite direction for two passes, further reducing phase perturbations. A master oscillator inputs the beam through an isolation cell (Faraday or Pockels) which transmits the beam into the ring without polarization rotation. The isolation cell rotates polarization only in beams proceeding out of the ring to direct the beams out of the amplifier. The diffraction limited quality of the input beam is preserved in the amplifier so that a high power output beam having nearly the same diffraction limited quality is produced.

Method for removing tilt control in adaptive optics systems

DOEpatents

Salmon, J.T.

1998-04-28

A new adaptive optics system and method of operation are disclosed, whereby the method removes tilt control, and includes the steps of using a steering mirror to steer a wavefront in the desired direction, for aiming an impinging aberrated light beam in the direction of a deformable mirror. The deformable mirror has its surface deformed selectively by means of a plurality of actuators, and compensates, at least partially, for existing aberrations in the light beam. The light beam is split into an output beam and a sample beam, and the sample beam is sampled using a wavefront sensor. The sampled signals are converted into corresponding electrical signals for driving a controller, which, in turn, drives the deformable mirror in a feedback loop in response to the sampled signals, for compensating for aberrations in the wavefront. To this purpose, a displacement error (gradient) of the wavefront is measured, and adjusted by a modified gain matrix, which satisfies the following equation: G{prime} = (I{minus}X(X{sup T} X){sup {minus}1}X{sup T})G(I{minus}A). 3 figs.

Instrumentation to Record Evoked Potentials for Closed-Loop Control of Deep Brain Stimulation

PubMed Central

Kent, Alexander R.; Grill, Warren M.

2012-01-01

Closed-loop deep brain stimulation (DBS) systems offer promise in relieving the clinical burden of stimulus parameter selection and improving treatment outcomes. In such a system, a feedback signal is used to adjust automatically stimulation parameters and optimize the efficacy of stimulation. We explored the feasibility of recording electrically evoked compound action potentials (ECAPs) during DBS for use as a feedback control signal. A novel instrumentation system was developed to suppress the stimulus artifact and amplify the small magnitude, short latency ECAP response during DBS with clinically relevant parameters. In vitro testing demonstrated the capabilities to increase the gain by a factor of 1,000x over a conventional amplifier without saturation, reduce distortion of mock ECAP signals, and make high fidelity recordings of mock ECAPs at latencies of only 0.5 ms following DBS pulses of 50 to 100 μs duration. Subsequently, the instrumentation was used to make in vivo recordings of ECAPs during thalamic DBS in cats, without contamination by the stimulus artifact. The signal characteristics were similar across three experiments, suggesting common neural activation patterns. The ECAP recordings enabled with this novel instrumentation may provide insight into the type and spatial extent of neural elements activated during DBS, and could serve as feedback control signals for closed-loop systems. PMID:22255894

Characterization and Design of Digital Pointing Subsystem for Optical Communication Demonstrator

NASA Technical Reports Server (NTRS)

Racho, C.; Portillo, A.

1998-01-01

The Optical Communications Demonstrator (OCD) is a laboratory-based lasercom demonstration terminal designed to validate several key technologies, including beacon acquisition, high bandwidth tracking, precision bearn pointing, and point-ahead compensation functions. It has been under active development over the past few years. The instrument uses a CCD array detector for both spatial acquisition and high-bandwidth tracking, and a fiber coupled laser transmitter. The array detector tracking concept provides wide field-of-view acquisition and permits effective platform jitter compensation and point-ahead control using only one steering mirror. This paper describes the detailed design and characterization of the digital control loop system which includes the Fast Steering Mirror (FSM), the CCD image tracker, and the associated electronics. The objective is to improve the overall system performance using laboratory measured data. The. design of the digital control loop is based on a linear time invariant open loop model. The closed loop performance is predicted using the theoretical model. With the digital filter programmed into the OCD control software, data is collected to verify the predictions. This paper presents the results of the, system modeling and performance analysis. It has been shown that measurement data closely matches theoretical predictions. An important part of the laser communication experiment is the ability of FSM to track the laser beacon within the. required tolerances. The pointing must be maintained to an accuracy that is much smaller than the transmit signal beamwidth. For an earth orbit distance, the system must be able to track the receiving station to within a few microradians. The failure. to do so will result in a severely degraded system performance.

Integrated packaging of 2D MOEMS mirrors with optical position feedback

NASA Astrophysics Data System (ADS)

Baumgart, M.; Lenzhofer, M.; Kremer, M. P.; Tortschanoff, A.

2015-02-01

Many applications of MOEMS microscanners rely on accurate position feedback. For MOEMS devices which do not have intrinsic on-chip feedback, position information can be provided with optical methods, most simply by using a reflection from the backside of a MOEMS scanner. By measuring the intensity distribution of the reflected beam across a quadrant diode, one can precisely detect the mirror's deflection angles. Previously, we have presented a position sensing device, applicable to arbitrary trajectories, which is based on the measurement of the position of the reflected laser beam with a quadrant diode. In this work, we present a novel setup, which comprises the optical position feedback functionality integrated into the device package itself. The new device's System-in-Package (SiP) design is based on a flip-folded 2.5D PCB layout and fully assembled as small as 9.2×7×4 mm³ in total. The device consists of four layers, which supply the MOEMS mirror, a spacer to provide the required optical path length, the quadrant photo-diode and a laser diode to serve as the light source. In addition to describing the mechanical setup of the novel device, we will present first experimental results and optical simulation studies. Accurate position feedback is the basis for closed-loop control of the MOEMS devices, which is crucial for some applications as image projection for example. Position feedback and the possibility of closed-loop control will significantly improve the performance of these devices.

Rapid specific and visible detection of porcine circovirus type 3 using loop-mediated isothermal amplification (LAMP).

PubMed

Zheng, S; Wu, X; Shi, J; Peng, Z; Gao, M; Xin, C; Liu, Y; Wang, S; Xu, S; Han, H; Yu, J; Sun, W; Cong, X; Li, J; Wang, J

2018-06-01

In this study, a rapid and specific assay for the detection of porcine circovirus type 3 (PCV3) was established using loop-mediated isothermal amplification (LAMP). Four primers were specifically designed to amplify PCV3. The LAMP assay was effectively optimized to amplify PCV3 by water bath at 60°C for 60 min. The detection limit was approximately 1 × 10 1 copy in this LAMP assay. Compared to porcine circovirus type 2 (PCV2), both gE and gD genes of pseudorabies virus (PRV) and porcine parvovirus (PPV), the LAMP assay showed a high specific detection of PCV3. A visible detection method was developed using SYBR Green I to recognize the results rapidly. Based on the detection of 20 clinical tissue samples, the LAMP assay was more practical and convenient than classical PCR due to its simplicity, high sensitivity, rapidity, specificity, visibility and cost efficiency. © 2018 Blackwell Verlag GmbH.

An All-Digital Fast Tracking Switching Converter with a Programmable Order Loop Controller for Envelope Tracking RF Power Amplifiers

PubMed Central

Anabtawi, Nijad; Ferzli, Rony; Harmanani, Haidar M.

2017-01-01

This paper presents a step down, switched mode power converter for use in multi-standard envelope tracking radio frequency power amplifiers (RFPA). The converter is based on a programmable order sigma delta modulator that can be configured to operate with either 1st, 2nd, 3rd or 4th order loop filters, eliminating the need for a bulky passive output filter. Output ripple, sideband noise and spectral emission requirements of different wireless standards can be met by configuring the modulator’s filter order and converter’s sampling frequency. The proposed converter is entirely digital and is implemented in 14nm bulk CMOS process for post layout verification. For an input voltage of 3.3V, the converter’s output can be regulated to any voltage level from 0.5V to 2.5V, at a nominal switching frequency of 150MHz. It achieves a maximum efficiency of 94% at 1.5 W output power. PMID:28919657

Detection of early and single infections of Schistosoma japonicum in the intermediate host snail, Oncomelania hupensis, by PCR and loop-mediated isothermal amplification (LAMP) assay.

PubMed

Kumagai, Takashi; Furushima-Shimogawara, Rieko; Ohmae, Hiroshi; Wang, Tian-Ping; Lu, Shaohong; Chen, Rui; Wen, Liyong; Ohta, Nobuo

2010-09-01

Polymerase chain reaction (PCR) with the specific primer set amplifying 28S ribosomal DNA (rDNA) of Schistosoma japonicum was able to detect genomic DNA of S. japonicum, but not S. mansoni, at 100 fg. This procedure enabled us to detect the DNA from a single miracidium and a snail infected with one miracidium at just 1 day after infection. We compared these results with those from loop-mediated isothermal amplification (LAMP) targeting 28S rDNA and found similar results. The LAMP could amplify the specific DNA from a group of 100 normal snails mixed with one infected snail A PCR screening of infected snails from endemic regions in Anhui Province revealed schistosomal DNA even in snails found negative by microscopy. PCR and LAMP show promise for monitoring the early infection rate in snails, and they may be useful for predicting the risk of infection in the endemic places.

MOEMS deformable mirror testing in cryo for future optical instrumentation

NASA Astrophysics Data System (ADS)

Zamkotsian, Frederic; Lanzoni, Patrick; Barette, Rudy; Grassi, Emmanuel; Vors, Patrick; Helmbrecht, Michael; Marchis, Franck; Teichman, Alex

2017-02-01

MOEMS Deformable Mirrors (DM) are key components for next generation optical instruments implementing innovative adaptive optics systems, in existing telescopes as well as in the future ELTs. Due to the wide variety of applications, these DMs must perform at room temperature as well as in cryogenic and vacuum environment. Ideally, the MOEMS-DMs must be designed to operate in such environment. This is unfortunately usually not the case. We will present some major rules for designing / operating DMs in cryo and vacuum. Next step is to characterize with high accuracy the different DM candidates. We chose to use interferometry for the full characterization of these devices, including surface quality measurement in static and dynamical modes, at ambient and in vacuum/cryo. Thanks to our previous set-up developments, we are placing a compact cryo-vacuum chamber designed for reaching 10-6 mbar and 160K, in front of our custom Michelson interferometer, able to measure performances of the DM at actuator/segment level as well as whole mirror level, with a lateral resolution of 2μm and a sub-nanometric zresolution. Using this interferometric bench, we tested the PTT 111 DM from Iris AO: this unique and robust design uses an array of single crystalline silicon hexagonal mirrors with a pitch of 606μm, able to move in tip, tilt and piston with strokes from 5 to 7μm, and tilt angle in the range of +/- 5mrad. They exhibit typically an open-loop flat surface figure as good as < 20nm rms. A specific mount including electronic and opto-mechanical interfaces has been designed for fitting in the test chamber. Segment deformation, mirror shaping, open-loop operation are tested at room and cryo temperature and results are compared. The device could be operated successfully at 160K. An additional, mainly focus-like, 500 nm deformation is measured at 160K; we were able to recover the best flat in cryo by correcting the focus and local tip-tilts on some segments. Tests on DM with different mirror thicknesses (25μm and 50μm) and different coatings (silver and gold) are currently under way. Finally, the goal of these studies is to test DMs in cryo and vacuum conditions as well as to improve their architecture for staying efficient in harsh environment.

High average power diode pumped solid state laser

NASA Astrophysics Data System (ADS)

Gao, Yue; Wang, Yanjie; Chan, Amy; Dawson, Murray; Greene, Ben

2017-03-01

A new generation of high average power pulsed multi-joule solid state laser system has been developed at EOS Space Systems for various space related tracking applications. It is a completely diode pumped, fully automated multi-stage system consisting of a pulsed single longitudinal mode oscillator, three stages of pre-amplifiers, two stages of power amplifiers, completely sealed phase conjugate mirror or stimulated Brillouin scattering (SBS) cell and imaging relay optics with spatial filters in vacuum cells. It is capable of generating pulse energy up to 4.7 J, a beam quality M 2 ~ 3, pulse width between 10-20 ns, and a pulse repetition rate between 100-200 Hz. The system has been in service for more than two years with excellent performance and reliability.

Electrical crosstalk-coupling measurement and analysis for digital closed loop fibre optic gyro

NASA Astrophysics Data System (ADS)

Jin, Jing; Tian, Hai-Ting; Pan, Xiong; Song, Ning-Fang

2010-03-01

The phase modulation and the closed-loop controller can generate electrical crosstalk-coupling in digital closed-loop fibre optic gyro. Four electrical cross-coupling paths are verified by the open-loop testing approach. It is found the variation of ramp amplitude will lead to the alternation of gyro bias. The amplitude and the phase parameters of the electrical crosstalk signal are measured by lock-in amplifier, and the variation of gyro bias is confirmed to be caused by the alternation of phase according to the amplitude of the ramp. A digital closed-loop fibre optic gyro electrical crosstalk-coupling model is built by approximating the electrical cross-coupling paths as a proportion and integration segment. The results of simulation and experiment show that the modulation signal electrical crosstalk-coupling can cause the dead zone of the gyro when a small angular velocity is inputted, and it could also lead to a periodic vibration of the bias error of the gyro when a large angular velocity is inputted.

Optically controlled switch-mode current-source amplifiers for on-coil implementation in high field parallel transmission

PubMed Central

Gudino, Natalia; Duan, Qi; de Zwart, Jacco A; Murphy-Boesch, Joe; Dodd, Stephen J; Merkle, Hellmut; van Gelderen, Peter; Duyn, Jeff H

2015-01-01

Purpose We tested the feasibility of implementing parallel transmission (pTX) for high field MRI using a radiofrequency (RF) amplifier design to be located on or in the immediate vicinity of a RF transmit coil. Method We designed a current-source switch-mode amplifier based on miniaturized, non-magnetic electronics. Optical RF carrier and envelope signals to control the amplifier were derived, through a custom-built interface, from the RF source accessible in the scanner control. Amplifier performance was tested by benchtop measurements as well as with imaging at 7 T (300 MHz) and 11.7 T (500 MHz). The ability to perform pTX was evaluated by measuring inter-channel coupling and phase adjustment in a 2-channel setup. Results The amplifier delivered in excess of 44 W RF power and caused minimal interference with MRI. The interface derived accurate optical control signals with carrier frequencies ranging from 64 to 750 MHz. Decoupling better than 14 dB was obtained between 2 coil loops separated by only 1 cm. Application to MRI was demonstrated by acquiring artifact-free images at 7 T and 11.7 T. Conclusion An optically controlled miniaturized RF amplifier for on-coil implementation at high field is demonstrated that should facilitate implementation of high-density pTX arrays. PMID:26256671

Performance of a modified feedback loop adaptive array with TVRO satellite signals

NASA Technical Reports Server (NTRS)

Steadman, Karl N.; Gupta, Inder J.; Walton, Eric K.

1990-01-01

Performance of an experimental adaptive antenna array system is evaluated using television receive-only (TVRO) satellite signals. The experimental system is a sidelobe canceller with two auxiliary channels. Modified feedback loops are used to enhance the suppression of weak interfering signals. The modified feedback loops used two spatialy separated antennas, each with an individual amplifier for each auxiliary channel. Thus, the experimental system uses five antenna elements. Instead of using five separate antennas, a reflector antenna with multiple feeds is used to receive signals from various TVRO satellites. The details of the earth station are given. It is shown that the experimental system can null up to two signals originating from interfering TVRO satellites while receiving the signals from a desired TVRO satellite.

OSA Trends in Optics and Photonics Series, Volume 14 Spatial Light Modulators

DTIC Science & Technology

1998-05-26

Extreme Ultraviolet Lithography Glenn D. Kubiak andDon R. Kania, eds. Vol. 5 Optical Amplifiers and Their Applications (1996) Edited by...micromirror device ( DMD ), and photorefractive crystal. Note that other devices not discussed in this article have been developed, such as the charge...earlier. DMDs are fabricated by micromachining a silicon wafer.7 Tiny (16 um X 16 um) suspended mirrors are micromachined on cantilevers. The

Cryogenic ultra-low power dissipation operational amplifiers with GaAs JFETs

NASA Astrophysics Data System (ADS)

Hibi, Yasunori; Matsuo, Hiroshi; Ikeda, Hirokazu; Fujiwara, Mikio; Kang, Lin; Chen, Jian; Wu, Peiheng

2016-01-01

To realize a multipixel camera for astronomical observation, we developed cryogenic multi-channel readout systems using gallium arsenide junction field-effect transistor (GaAs JFET) integrated circuits (ICs). Based on our experience with these cryogenic ICs, we designed, manufactured, and demonstrated operational amplifiers requiring four power supplies and two voltage sources. The amplifiers operate at 4.2 K with an open-loop gain of 2000. The gain-bandwidth product can expect 400 kHz at a power dissipation of 6 μW. In performance evaluations, the input-referred voltage noise was 4 μVrms/Hz0.5 at 1 Hz and 30 nVrms/Hz0.5 at 10 kHz, respectively. The noise power spectrum density was of type 1/f and extended to 10 kHz.

Gain dynamics of clad-pumped Yb-fiber amplifier and intensity noise control.

PubMed

Zhao, Jian; Guiraud, Germain; Floissat, Florian; Gouhier, Benoit; Rota-Rodrigo, Sergio; Traynor, Nicholas; Santarelli, Giorgio

2017-01-09

Gain dynamics study provides an attractive method to understand the intensity noise behavior in fiber amplifiers. Here, the gain dynamics of a medium power (5 W) clad-pumped Yb-fiber amplifier is experimentally evaluated by measuring the frequency domain transfer functions for the input seed and pump lasers from 10 Hz to 1 MHz. We study gain dynamic behavior of the fiber amplifier in the presence of significant residual pump power (compared to the seed power), showing that the seed transfer function is strongly saturated at low Fourier frequencies while the pump power modulation transfer function is nearly unaffected. The characterization of relative intensity noise (RIN) of the fiber amplifier is well explained by the gain dynamics analysis. Finally, a 600 kHz bandwidth feedback loop using an acoustic-optical modulator (AOM) controlling the seed intensity is successfully demonstrated to suppress the broadband laser intensity noise. A maximum noise reduction of about 30 dB is achieved leading to a RIN of -152 dBc/Hz (~1 kHz-10 MHz) at 2.5 W output power.

Lepton flavor violating radiative decays in EW-scale ν R model: an update

DOE PAGES

Hung, P. Q.; Le, Trinh; Tran, Van Que; ...

2015-12-28

Here, we perform an updated analysis for the one-loop induced charged lepton flavor violating radiative decays l i → l j γ in an extended mirror model. Mixing effects of the neutrinos and charged leptons constructed with a horizontal A 4 symmetry are also taken into account. Current experimental limit and projected sensitivity on the branching ratio of μ → eγ are used to constrain the parameter space of the model. Calculations of two related observables, the electric and magnetic dipole moments of the leptons, are included. Implications concerning the possible detection of mirror leptons at the LHC and themore » ILC are also discussed.« less

Reconnection, Particle Acceleration, and Hard X-ray Emission in Eruptive Solar Flares

NASA Astrophysics Data System (ADS)

Martens, Petrus C.

1998-11-01

The frequent occurrence of Hard X-ray emission from the top of flaring loops was one of the discoveries by the Hard X-ray telescope on board the Japanese Yohkoh satellite. I will show how the combined effect of magnetic field convergence and pitch- angle scattering of non-thermal electrons injected at the top of the loop results in the generation of looptop sources with properties akin to those observed by Yohkoh. In addition it is shown that the injection of proton beams in the loop legs, expected from theory, reproduces the observed high temperature ``ridges" in the loop legs by mirroring and energy loss through collisions. I will interpret these numerical results as supporting the now widely accepted model of an erupting magnetic flux tube generating a reconnecting current sheet in its wake, where most of the energy release takes place. The strong similarity with the reconnection observed in the MRX experiment in Princeton will be analyzed in detail.

Linear versus non-linear measures of temporal variability in finger tapping and their relation to performance on open- versus closed-loop motor tasks: comparing standard deviations to Lyapunov exponents.

PubMed

Christman, Stephen D; Weaver, Ryan

2008-05-01

The nature of temporal variability during speeded finger tapping was examined using linear (standard deviation) and non-linear (Lyapunov exponent) measures. Experiment 1 found that right hand tapping was characterised by lower amounts of both linear and non-linear measures of variability than left hand tapping, and that linear and non-linear measures of variability were often negatively correlated with one another. Experiment 2 found that increased non-linear variability was associated with relatively enhanced performance on a closed-loop motor task (mirror tracing) and relatively impaired performance on an open-loop motor task (pointing in a dark room), especially for left hand performance. The potential uses and significance of measures of non-linear variability are discussed.

Laser spark distribution and ignition system

DOEpatents

Woodruff, Steven [Morgantown, WV; McIntyre, Dustin L [Morgantown, WV

2008-09-02

A laser spark distribution and ignition system that reduces the high power optical requirements for use in a laser ignition and distribution system allowing for the use of optical fibers for delivering the low peak energy pumping pulses to a laser amplifier or laser oscillator. An optical distributor distributes and delivers optical pumping energy from an optical pumping source to multiple combustion chambers incorporating laser oscillators or laser amplifiers for inducing a laser spark within a combustion chamber. The optical distributor preferably includes a single rotating mirror or lens which deflects the optical pumping energy from the axis of rotation and into a plurality of distinct optical fibers each connected to a respective laser media or amplifier coupled to an associated combustion chamber. The laser spark generators preferably produce a high peak power laser spark, from a single low power pulse. The laser spark distribution and ignition system has application in natural gas fueled reciprocating engines, turbine combustors, explosives and laser induced breakdown spectroscopy diagnostic sensors.

The Dual-Loop Model and the Human Mirror Neuron System: an Exploratory Combined fMRI and DTI Study of the Inferior Frontal Gyrus.

PubMed

Hamzei, Farsin; Vry, Magnus-Sebastian; Saur, Dorothee; Glauche, Volkmar; Hoeren, Markus; Mader, Irina; Weiller, Cornelius; Rijntjes, Michel

2016-05-01

The inferior frontal gyrus (IFG) is active during both goal-directed action and while observing the same motor act, leading to the idea that also the meaning of a motor act (action understanding) is represented in this "mirror neuron system" (MNS). However, in the dual-loop model, based on dorsal and ventral visual streams, the MNS is thought to be a function of the dorsal steam, projecting to pars opercularis (BA44) of IFG, while recent studies suggest that conceptual meaning and semantic analysis are a function of ventral connections, projecting mainly to pars triangularis (BA45) of IFG. To resolve this discrepancy, we investigated action observation (AO) and imitation (IMI) using fMRI in a large group of subjects. A grasping task (GR) assessed the contribution from movement without AO. We analyzed connections of the MNS-related areas within IFG with postrolandic areas with the use of activation-based DTI. We found that action observation with imitation are mainly a function of the dorsal stream centered on dorsal part of BA44, but also involve BA45, which is dorsally and ventrally connected to the same postrolandic regions. The current finding suggests that BA45 is the crucial part where the MNS and the dual-loop system interact. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Observation of a metric type N solar radio burst

DOE PAGES

Kong, Xiangliang; Chen, Yao; Feng, Shiwei; ...

2016-10-10

Type III and type-III-like radio bursts are produced by energetic electron beams guided along coronal magnetic fields. As a variant of type III bursts, Type N bursts appear as the letter "N" in the radio dynamic spectrum and reveal a magnetic mirror effect in coronal loops. Here, we report a well-observed N-shaped burst consisting of three successive branches at metric wavelength with both fundamental and harmonic components and a high brightness temperature (>10 9 K). We verify the burst as a true type N burst generated by the same electron beam from three aspects of the data. First, durations ofmore » the three branches at a given frequency increase gradually and may be due to the dispersion of the beam along its path. Second, the flare site, as the only possible source of non-thermal electrons, is near the western feet of large-scale closed loops. Third, the first branch and the following two branches are localized at different legs of the loops with opposite senses of polarization. We also find that the sense of polarization of the radio burst is in contradiction to the O-mode and there exists a fairly large time delay (~3–5 s) between the fundamental and harmonic components. Possible explanations accounting for these observations are presented. Finally, assuming the classical plasma emission mechanism, we can infer coronal parameters such as electron density and magnetic field near the radio source and make diagnostics on the magnetic mirror process.« less

Active Mirror Predictive and Requirements Verification Software (AMP-ReVS)

NASA Technical Reports Server (NTRS)

Basinger, Scott A.

2012-01-01

This software is designed to predict large active mirror performance at various stages in the fabrication lifecycle of the mirror. It was developed for 1-meter class powered mirrors for astronomical purposes, but is extensible to other geometries. The package accepts finite element model (FEM) inputs and laboratory measured data for large optical-quality mirrors with active figure control. It computes phenomenological contributions to the surface figure error using several built-in optimization techniques. These phenomena include stresses induced in the mirror by the manufacturing process and the support structure, the test procedure, high spatial frequency errors introduced by the polishing process, and other process-dependent deleterious effects due to light-weighting of the mirror. Then, depending on the maturity of the mirror, it either predicts the best surface figure error that the mirror will attain, or it verifies that the requirements for the error sources have been met once the best surface figure error has been measured. The unique feature of this software is that it ties together physical phenomenology with wavefront sensing and control techniques and various optimization methods including convex optimization, Kalman filtering, and quadratic programming to both generate predictive models and to do requirements verification. This software combines three distinct disciplines: wavefront control, predictive models based on FEM, and requirements verification using measured data in a robust, reusable code that is applicable to any large optics for ground and space telescopes. The software also includes state-of-the-art wavefront control algorithms that allow closed-loop performance to be computed. It allows for quantitative trade studies to be performed for optical systems engineering, including computing the best surface figure error under various testing and operating conditions. After the mirror manufacturing process and testing have been completed, the software package can be used to verify that the underlying requirements have been met.

A microprocessor-based position control system for a telescope secondary mirror

NASA Technical Reports Server (NTRS)

Lorell, K. R.; Barrows, W. F.; Clappier, R. R.; Lee, G. K.

1983-01-01

The pointing requirements for the Shuttle IR Telescope Facility (SIRTF), which consists of an 0.85-m cryogenically cooled IR telescope, call for an image stability of 0.25 arcsec. Attention is presently given to a microprocessor-based position control system developed for the control of the SIRTF secondary mirror, employing a special control law (to minimize energy dissipation), a precision capacitive position sensor, and a specially designed power amplifier/actuator combination. The microprocessor generates the command angular position and rate waveforms in order to maintain a 90 percent dwell time/10 percent transition time ratio independently of chop frequency or amplitude. Performance and test results of a prototype system designed for use with a demonstration model of the SIRTF focal plane fine guidance sensor are presented.

Electrostatic polymer-based microdeformable mirror for adaptive optics

NASA Astrophysics Data System (ADS)

Zamkotsian, Frederic; Conedera, Veronique; Granier, Hugues; Liotard, Arnaud; Lanzoni, Patrick; Salvagnac, Ludovic; Fabre, Norbert; Camon, Henri

2007-02-01

Future adaptive optics (AO) systems require deformable mirrors with very challenging parameters, up to 250 000 actuators and inter-actuator spacing around 500 μm. MOEMS-based devices are promising for the development of a complete generation of new deformable mirrors. Our micro-deformable mirror (MDM) is based on an array of electrostatic actuators with attachments to a continuous mirror on top. The originality of our approach lies in the elaboration of layers made of polymer materials. Mirror layers and active actuators have been demonstrated. Based on the design of this actuator and our polymer process, realization of a complete polymer-MDM has been done using two process flows: the first involves exclusively polymer materials while the second uses SU8 polymer for structural layers and SiO II and sol-gel for sacrificial layers. The latest shows a better capability in order to produce completely released structures. The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. Then, we have developed a dedicated 14-bit electronics in order to "linearize" the actuation, using a calibration and a sixth-order polynomial fitting strategy. The response is nearly perfect over our 3×3 MDM prototype with a standard deviation of 3.5 nm; the influence function of the central actuator has been measured. First evaluation on the cross non-linarities has also been studied on OKO mirror and a simple look-up table is sufficient for determining the location of each actuator whatever the locations of the neighbor actuators. Electrostatic MDM are particularly well suited for open-loop AO applications.

CMOS analogue amplifier circuits optimisation using hybrid backtracking search algorithm with differential evolution

NASA Astrophysics Data System (ADS)

Mallick, S.; Kar, R.; Mandal, D.; Ghoshal, S. P.

2016-07-01

This paper proposes a novel hybrid optimisation algorithm which combines the recently proposed evolutionary algorithm Backtracking Search Algorithm (BSA) with another widely accepted evolutionary algorithm, namely, Differential Evolution (DE). The proposed algorithm called BSA-DE is employed for the optimal designs of two commonly used analogue circuits, namely Complementary Metal Oxide Semiconductor (CMOS) differential amplifier circuit with current mirror load and CMOS two-stage operational amplifier (op-amp) circuit. BSA has a simple structure that is effective, fast and capable of solving multimodal problems. DE is a stochastic, population-based heuristic approach, having the capability to solve global optimisation problems. In this paper, the transistors' sizes are optimised using the proposed BSA-DE to minimise the areas occupied by the circuits and to improve the performances of the circuits. The simulation results justify the superiority of BSA-DE in global convergence properties and fine tuning ability, and prove it to be a promising candidate for the optimal design of the analogue CMOS amplifier circuits. The simulation results obtained for both the amplifier circuits prove the effectiveness of the proposed BSA-DE-based approach over DE, harmony search (HS), artificial bee colony (ABC) and PSO in terms of convergence speed, design specifications and design parameters of the optimal design of the analogue CMOS amplifier circuits. It is shown that BSA-DE-based design technique for each amplifier circuit yields the least MOS transistor area, and each designed circuit is shown to have the best performance parameters such as gain, power dissipation, etc., as compared with those of other recently reported literature.

A Kinetics Model for KrF Laser Amplifiers

NASA Astrophysics Data System (ADS)

Giuliani, J. L.; Kepple, P.; Lehmberg, R.; Obenschain, S. P.; Petrov, G.

1999-11-01

A computer kinetics code has been developed to model the temporal and spatial behavior of an e-beam pumped KrF laser amplifier. The deposition of the primary beam electrons is assumed to be spatially uniform and the energy distribution function of the nascent electron population is calculated to be near Maxwellian below 10 eV. For an initial Kr/Ar/F2 composition, the code calculates the densities of 24 species subject to over 100 reactions with 1-D spatial resolution (typically 16 zones) along the longitudinal lasing axis. Enthalpy accounting for each process is performed to partition the energy into internal, thermal, and radiative components. The electron as well as the heavy particle temperatures are followed for energy conservation and excitation rates. Transport of the lasing photons is performed along the axis on a dense subgrid using the method of characteristics. Amplified spontaneous emission is calculated using a discrete ordinates approach and includes contributions to the local intensity from the whole amplifier volume. Specular reflection off side walls and the rear mirror are included. Results of the model will be compared with data from the NRL NIKE laser and other published results.

Impact of primer dimers and self-amplifying hairpins on reverse transcription loop-mediated isothermal amplification detection of viral RNA

DOE PAGES

Meagher, Robert J.; Priye, Aashish; Light, Yooli K.; ...

2018-03-27

Loop-mediated isothermal amplification (LAMP), coupled with reverse transcription (RT), has become a popular technique for detection of viral RNA due to several desirable characteristics for use in point-of-care or low-resource settings. The large number of primers in LAMP (six per target) leads to an increased likelihood of primer-dimer interactions, and the inner primers in particular are prone to formation of stable hairpin structures due to their length (typically 40-45 bases). Although primer-dimers and hairpin structures are known features to avoid in nucleic acid amplification techniques, there is little quantitative information in literature regarding the impact of these structures on LAMPmore » or RT-LAMP assays. In this study, we examine the impact of primer-dimers and hairpins on previously-published primer sets for dengue virus and yellow fever virus. We demonstrate that minor changes to the primers to eliminate amplifiable primer dimers and hairpins improves the performance of the assays when monitored in real time with intercalating dyes, and when monitoring a fluorescent endpoint using the QUASR technique. We also discuss the thermodynamic implications of these minor changes on the overall stability of amplifiable secondary structures, and we present a single thermodynamic parameter to predict the probability of non-specific amplification associated with LAMP primers.« less

Impact of primer dimers and self-amplifying hairpins on reverse transcription loop-mediated isothermal amplification detection of viral RNA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meagher, Robert J.; Priye, Aashish; Light, Yooli K.

Loop-mediated isothermal amplification (LAMP), coupled with reverse transcription (RT), has become a popular technique for detection of viral RNA due to several desirable characteristics for use in point-of-care or low-resource settings. The large number of primers in LAMP (six per target) leads to an increased likelihood of primer-dimer interactions, and the inner primers in particular are prone to formation of stable hairpin structures due to their length (typically 40-45 bases). Although primer-dimers and hairpin structures are known features to avoid in nucleic acid amplification techniques, there is little quantitative information in literature regarding the impact of these structures on LAMPmore » or RT-LAMP assays. In this study, we examine the impact of primer-dimers and hairpins on previously-published primer sets for dengue virus and yellow fever virus. We demonstrate that minor changes to the primers to eliminate amplifiable primer dimers and hairpins improves the performance of the assays when monitored in real time with intercalating dyes, and when monitoring a fluorescent endpoint using the QUASR technique. We also discuss the thermodynamic implications of these minor changes on the overall stability of amplifiable secondary structures, and we present a single thermodynamic parameter to predict the probability of non-specific amplification associated with LAMP primers.« less

A low-noise transimpedance amplifier for the detection of “Violin-Mode” resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lockerbie, N. A.; Tokmakov, K. V.

2014-11-15

This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level “Violin-Mode” (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent “noise-gain peaking” arising from large area photodiode (and cable) capacitances, and which also usefullymore » separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes’ two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m{sup −1}(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.« less

A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in Advanced Laser Interferometer Gravitational wave Observatory suspensions.

PubMed

Lockerbie, N A; Tokmakov, K V

2014-11-01

This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations-this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m(-1)(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

NASA Astrophysics Data System (ADS)

Lockerbie, N. A.; Tokmakov, K. V.

2014-11-01

This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m-1(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

Concerted loop motion triggers induced fit of FepA to ferric enterobactin

PubMed Central

Smallwood, Chuck R.; Jordan, Lorne; Trinh, Vy; Schuerch, Daniel W.; Gala, Amparo; Hanson, Mathew; Shipelskiy, Yan; Majumdar, Aritri; Newton, Salete M.C.

2014-01-01

Spectroscopic analyses of fluorophore-labeled Escherichia coli FepA described dynamic actions of its surface loops during binding and transport of ferric enterobactin (FeEnt). When FeEnt bound to fluoresceinated FepA, in living cells or outer membrane fragments, quenching of fluorophore emissions reflected conformational motion of the external vestibular loops. We reacted Cys sulfhydryls in seven surface loops (L2, L3, L4, L5, L7 L8, and L11) with fluorophore maleimides. The target residues had different accessibilities, and the labeled loops themselves showed variable extents of quenching and rates of motion during ligand binding. The vestibular loops closed around FeEnt in about a second, in the order L3 > L11 > L7 > L2 > L5 > L8 > L4. This sequence suggested that the loops bind the metal complex like the fingers of two hands closing on an object, by individually adsorbing to the iron chelate. Fluorescence from L3 followed a biphasic exponential decay as FeEnt bound, but fluorescence from all the other loops followed single exponential decay processes. After binding, the restoration of fluorescence intensity (from any of the labeled loops) mirrored cellular uptake that depleted FeEnt from solution. Fluorescence microscopic images also showed FeEnt transport, and demonstrated that ferric siderophore uptake uniformly occurs throughout outer membrane, including at the poles of the cells, despite the fact that TonB, its inner membrane transport partner, was not detectable at the poles. PMID:24981231

Concerted loop motion triggers induced fit of FepA to ferric enterobactin.

PubMed

Smallwood, Chuck R; Jordan, Lorne; Trinh, Vy; Schuerch, Daniel W; Gala, Amparo; Hanson, Mathew; Hanson, Matthew; Shipelskiy, Yan; Majumdar, Aritri; Newton, Salete M C; Klebba, Phillip E

2014-07-01

Spectroscopic analyses of fluorophore-labeled Escherichia coli FepA described dynamic actions of its surface loops during binding and transport of ferric enterobactin (FeEnt). When FeEnt bound to fluoresceinated FepA, in living cells or outer membrane fragments, quenching of fluorophore emissions reflected conformational motion of the external vestibular loops. We reacted Cys sulfhydryls in seven surface loops (L2, L3, L4, L5, L7 L8, and L11) with fluorophore maleimides. The target residues had different accessibilities, and the labeled loops themselves showed variable extents of quenching and rates of motion during ligand binding. The vestibular loops closed around FeEnt in about a second, in the order L3 > L11 > L7 > L2 > L5 > L8 > L4. This sequence suggested that the loops bind the metal complex like the fingers of two hands closing on an object, by individually adsorbing to the iron chelate. Fluorescence from L3 followed a biphasic exponential decay as FeEnt bound, but fluorescence from all the other loops followed single exponential decay processes. After binding, the restoration of fluorescence intensity (from any of the labeled loops) mirrored cellular uptake that depleted FeEnt from solution. Fluorescence microscopic images also showed FeEnt transport, and demonstrated that ferric siderophore uptake uniformly occurs throughout outer membrane, including at the poles of the cells, despite the fact that TonB, its inner membrane transport partner, was not detectable at the poles. © 2014 Smallwood et al.

A Hybrid Semi-Digital Transimpedance Amplifier With Noise Cancellation Technique for Nanopore-Based DNA Sequencing.

PubMed

Hsu, Chung-Lun; Jiang, Haowei; Venkatesh, A G; Hall, Drew A

2015-10-01

Over the past two decades, nanopores have been a promising technology for next generation deoxyribonucleic acid (DNA) sequencing. Here, we present a hybrid semi-digital transimpedance amplifier (HSD-TIA) to sense the minute current signatures introduced by single-stranded DNA (ssDNA) translocating through a nanopore, while discharging the baseline current using a semi-digital feedback loop. The amplifier achieves fast settling by adaptively tuning a DC compensation current when a step input is detected. A noise cancellation technique reduces the total input-referred current noise caused by the parasitic input capacitance. Measurement results show the performance of the amplifier with 31.6 M Ω mid-band gain, 950 kHz bandwidth, and 8.5 fA/ √Hz input-referred current noise, a 2× noise reduction due to the noise cancellation technique. The settling response is demonstrated by observing the insertion of a protein nanopore in a lipid bilayer. Using the nanopore, the HSD-TIA was able to measure ssDNA translocation events.

BICMOS power detector for pulsed Rf power amplifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bridge, Clayton D.

2016-10-01

A BiCMOS power detector for pulsed radio-frequency power amplifiers is proposed. Given the pulse waveform and a fraction of the power amplifier's input or output signal, the detector utilizes a low-frequency feedback loop to perform a successive approximation of the amplitude of the input signal. Upon completion of the successive approximation, the detector returns 9-bits representing the amplitude of the RF input signal. Using the pulse waveform from the power amplifier, the detector can dynamically adjust the rate of the binary search operation in order to return the updated amplitude information of the RF input signal at least every 1ms.more » The detector can handle pulse waveform frequencies from 50kHz to 10MHz with duty cycles in the range of 5- 50% and peak power levels of -10 to 10dBm. The signal amplitude measurement can be converted to a peak power measurement accurate to within ±0.6dB of the input RF power.« less

H∞ Robust Control of a Large-Piston MEMS Micromirror for Compact Fourier Transform Spectrometer Systems.

PubMed

Chen, Huipeng; Li, Mengyuan; Zhang, Yi; Xie, Huikai; Chen, Chang; Peng, Zhangming; Su, Shaohui

2018-02-08

Incorporating linear-scanning micro-electro-mechanical systems (MEMS) micromirrors into Fourier transform spectral acquisition systems can greatly reduce the size of the spectrometer equipment, making portable Fourier transform spectrometers (FTS) possible. How to minimize the tilting of the MEMS mirror plate during its large linear scan is a major problem in this application. In this work, an FTS system has been constructed based on a biaxial MEMS micromirror with a large-piston displacement of 180 μm, and a biaxial H∞ robust controller is designed. Compared with open-loop control and proportional-integral-derivative (PID) closed-loop control, H∞ robust control has good stability and robustness. The experimental results show that the stable scanning displacement reaches 110.9 μm under the H∞ robust control, and the tilting angle of the MEMS mirror plate in that full scanning range falls within ±0.0014°. Without control, the FTS system cannot generate meaningful spectra. In contrast, the FTS yields a clean spectrum with a full width at half maximum (FWHM) spectral linewidth of 96 cm -1 under the H∞ robust control. Moreover, the FTS system can maintain good stability and robustness under various driving conditions.

H∞ Robust Control of a Large-Piston MEMS Micromirror for Compact Fourier Transform Spectrometer Systems

PubMed Central

Li, Mengyuan; Zhang, Yi; Chen, Chang; Peng, Zhangming; Su, Shaohui

2018-01-01

Incorporating linear-scanning micro-electro-mechanical systems (MEMS) micromirrors into Fourier transform spectral acquisition systems can greatly reduce the size of the spectrometer equipment, making portable Fourier transform spectrometers (FTS) possible. How to minimize the tilting of the MEMS mirror plate during its large linear scan is a major problem in this application. In this work, an FTS system has been constructed based on a biaxial MEMS micromirror with a large-piston displacement of 180 μm, and a biaxial H∞ robust controller is designed. Compared with open-loop control and proportional-integral-derivative (PID) closed-loop control, H∞ robust control has good stability and robustness. The experimental results show that the stable scanning displacement reaches 110.9 μm under the H∞ robust control, and the tilting angle of the MEMS mirror plate in that full scanning range falls within ±0.0014°. Without control, the FTS system cannot generate meaningful spectra. In contrast, the FTS yields a clean spectrum with a full width at half maximum (FWHM) spectral linewidth of 96 cm−1 under the H∞ robust control. Moreover, the FTS system can maintain good stability and robustness under various driving conditions. PMID:29419765

Realtime system for GLAS on WHT

NASA Astrophysics Data System (ADS)

Skvarč, Jure; Tulloch, Simon; Myers, Richard M.

2006-06-01

The new ground layer adaptive optics system (GLAS) on the William Herschel Telescope (WHT) on La Palma will be based on the existing natural guide star adaptive optics system called NAOMI. A part of the new developments is a new control system for the tip-tilt mirror. Instead of the existing system, built around a custom built multiprocessor computer made of C40 DSPs, this system uses an ordinary PC machine and a Linux operating system. It is equipped with a high sensitivity L3 CCD camera with effective readout noise of nearly zero. The software design for the tip-tilt system is being completely redeveloped, in order to make a use of object oriented design which should facilitate easier integration with the rest of the observing system at the WHT. The modular design of the system allows incorporation of different centroiding and loop control methods. To test the system off-sky, we have built a laboratory bench using an artificial light source and a tip-tilt mirror. We present results of tip-tilt correction quality using different centroiding algorithms and different control loop methods at different light levels. This system will serve as a testing ground for a transition to a completely PC-based real-time control system.

Fast autonomous holographic adaptive optics

NASA Astrophysics Data System (ADS)

Andersen, G.

2010-07-01

We have created a new adaptive optics system using a holographic modal wavefront sensing method capable of autonomous (computer-free) closed-loop control of a MEMS deformable mirror. A multiplexed hologram is recorded using the maximum and minimum actuator positions on the deformable mirror as the "modes". On reconstruction, an input beam will be diffracted into pairs of focal spots - the ratio of particular pairs determines the absolute wavefront phase at a particular actuator location. The wavefront measurement is made using a fast, sensitive photo-detector array such as a multi-pixel photon counters. This information is then used to directly control each actuator in the MEMS DM without the need for any computer in the loop. We present initial results of a 32-actuator prototype device. We further demonstrate that being an all-optical, parallel processing scheme, the speed is independent of the number of actuators. In fact, the limitations on speed are ultimately determined by the maximum driving speed of the DM actuators themselves. Finally, being modal in nature, the system is largely insensitive to both obscuration and scintillation. This should make it ideal for laser beam transmission or imaging under highly turbulent conditions.

Angle amplifying optics using plane and ellipsoidal reflectors

DOEpatents

Glass, Alexander J.

1977-01-01

An optical system for providing a wide angle input beam into ellipsoidal laser fusion target illumination systems. The optical system comprises one or more pairs of centrally apertured plane and ellipsoidal mirrors disposed to accept the light input from a conventional lens of modest focal length and thickness, to increase the angular divergence thereof to a value equivalent to that of fast lenses, and to direct the light into the ellipsoidal target illumination system.

An AC modulated near infrared gain calibration system for a “Violin-Mode” transimpedance amplifier, intended for advanced LIGO suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lockerbie, N. A.; Tokmakov, K. V.

The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a “tall-thin” rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse “Violin-Mode” vibrations of such a fibre, via the oscillatory movement of the shadowmore » cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor’s DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor’s more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz–300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m{sup −1} was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain ratio of 922.5 for this sensor, at 500 Hz, translated into a maximum Violin-Mode (AC) responsivity of (1.16 ± 0.05) MV m{sup −1}, at that frequency.« less

Multipass OPCPA system at 100 kHz pumped by a CPA-free solid-state amplifier.

PubMed

Ahrens, J; Prochnow, O; Binhammer, T; Lang, T; Schulz, B; Frede, M; Morgner, U

2016-04-18

We present a compact few-cycle 100 kHz OPCPA system pumped by a CPA-free picosecond Nd:YVO₄ solid-state amplifier with all-optical synchronization to an ultra-broadband Ti:sapphire oscillator. This pump approach shows an exceptional conversion rate into the second harmonic of almost 78%. Efficient parametric amplification was realized by a two stage double-pass scheme with following chirped mirror compressor. The amount of superfluorescence was measured by an optical cross-correlation. Pulses with a duration of 8.7 fs at energies of 18 µJ are demonstrated. Due to the peak power of 1.26 GW, this simple OPCPA approach forms an ideal high repetition rate driving source for high-order harmonic generation.

A nonlinear disturbance-decoupled elevation axis controller for the Multiple Mirror Telescope

NASA Astrophysics Data System (ADS)

Clark, Dusty; Trebisky, Tom; Powell, Keith

2008-07-01

The Multiple Mirror Telescope (MMT), upgraded in 2000 to a monolithic 6.5m primary mirror from its original array of six 1.8m primary mirrors, was commissioned with axis controllers designed early in the upgrade process without regard to structural resonances or the possibility of the need for digital filtering of the control axis signal path. Post-commissioning performance issues led us to investigate replacement of the original control system with a more modern digital controller with full control over the system filters and gain paths. This work, from system identification through controller design iteration by simulation, and pre-deployment hardware-in-the-loop testing, was performed using latest-generation tools with Matlab® and Simulink®. Using Simulink's Real Time Workshop toolbox to automatically generate C source code for the controller from the Simulink diagram and a custom target build script, we were able to deploy the new controller into our existing software infrastructure running Wind River's VxWorks™real-time operating system. This paper describes the process of the controller design, including system identification data collection, with discussion of implementation of non-linear control modes and disturbance decoupling, which became necessary to obtain acceptable wind buffeting rejection.

A theory of circular organization and negative feedback: defining life in a cybernetic context.

PubMed

Tsokolov, Sergey

2010-12-01

All life today incorporates a variety of systems controlled by negative feedback loops and sometimes amplified by positive feedback loops. The first forms of life necessarily also required primitive versions of feedback, yet surprisingly little emphasis has been given to the question of how feedback emerged out of primarily chemical systems. One chemical system has been established that spontaneously develops autocatalytic feedback, the Belousov-Zhabotinsky (BZ) reaction. In this essay, I discuss the BZ reaction as a possible model for similar reactions that could have occurred under prebiotic Earth conditions. The main point is that the metabolism of contemporary life evolved from primitive homeostatic networks regulated by negative feedback. Because life could not exist in their absence, feedback loops should be included in definitions of life.

Performance of a modified feedback loop adaptive array with TVRO satellite signals

NASA Technical Reports Server (NTRS)

Steadman, K.; Gupta, I. J.; Walton, E. K.

1990-01-01

The performance of an experimental adaptive antenna array system is evaluated using television-receive-only (TVRO) satellite signals. The experimental system is a sidelobe canceler with two auxiliary channels. Modified feedback loops are used to enhance the suppression of weak interfering signals. The modified feedback loops use two spatially separate antennas, each with an individual amplifier for each auxiliary channel. Thus, the experimental system uses five antenna elements. Instead of using five separate antennas, a reflector antenna with multiple feeds is used to receive signals from various TVRO satellites. The details of the earth station are given. It is shown that the experimental system can null up to two signals originating from interfering TVRO satellites while receiving the signals from a desired TVRO satellite.

A Theory of Circular Organization and Negative Feedback: Defining Life in a Cybernetic Context

NASA Astrophysics Data System (ADS)

Tsokolov, Sergey

2010-12-01

All life today incorporates a variety of systems controlled by negative feedback loops and sometimes amplified by positive feedback loops. The first forms of life necessarily also required primitive versions of feedback, yet surprisingly little emphasis has been given to the question of how feedback emerged out of primarily chemical systems. One chemical system has been established that spontaneously develops autocatalytic feedback, the Belousov-Zhabotinsky (BZ) reaction. In this essay, I discuss the BZ reaction as a possible model for similar reactions that could have occurred under prebiotic Earth conditions. The main point is that the metabolism of contemporary life evolved from primitive homeostatic networks regulated by negative feedback. Because life could not exist in their absence, feedback loops should be included in definitions of life.

Simultaneous Solar Maximum Mission (SMM) and very large array observations of solar active regions

NASA Technical Reports Server (NTRS)

Lang, K. R.

1986-01-01

The research deals mainly with Very Large Array and Solar Maximum Mission observations of the ubiquitous coronal loops that dominate the structure of the low corona. As illustrated, the observations of thermal cyclotron lines at microwave wavelengths provide a powerful new method of accurately specifying the coronal magnetic field strength. Processes are delineated that trigger solar eruptions from coronal loops, including preburst heating and the magnetic interaction of coronal loops. Evidence for coherent burst mechanisms is provided for both the Sun and nearby stars, while other observations suggest the presence of currents that may amplify the coronal magnetic field to unexpectedly high levels. The existence is reported of a new class of compact, variable moving sources in regions of apparently weak photospheric field.

A Printed Organic Amplification System for Wearable Potentiometric Electrochemical Sensors.

PubMed

Shiwaku, Rei; Matsui, Hiroyuki; Nagamine, Kuniaki; Uematsu, Mayu; Mano, Taisei; Maruyama, Yuki; Nomura, Ayako; Tsuchiya, Kazuhiko; Hayasaka, Kazuma; Takeda, Yasunori; Fukuda, Takashi; Kumaki, Daisuke; Tokito, Shizuo

2018-03-02

Electrochemical sensor systems with integrated amplifier circuits play an important role in measuring physiological signals via in situ human perspiration analysis. Signal processing circuitry based on organic thin-film transistors (OTFTs) have significant potential in realizing wearable sensor devices due to their superior mechanical flexibility and biocompatibility. Here, we demonstrate a novel potentiometric electrochemical sensing system comprised of a potassium ion (K + ) sensor and amplifier circuits employing OTFT-based pseudo-CMOS inverters, which have a highly controllable switching voltage and closed-loop gain. The ion concentration sensitivity of the fabricated K + sensor was 34 mV/dec, which was amplified to 160 mV/dec (by a factor of 4.6) with high linearity. The developed system is expected to help further the realization of ultra-thin and flexible wearable sensor devices for healthcare applications.

Theoretical Model Images and Spectra for Comparison with HESSI and Microwave Observations of Solar Flares

NASA Technical Reports Server (NTRS)

Fisher, Richard R. (Technical Monitor); Holman, G. D.; Sui, L.; McTiernan, J. M.; Petrosian, V.

2003-01-01

We have computed bremsstrahlung and gyrosynchrotron images and spectra from a model flare loop. Electrons with a power-law energy distribution are continuously injected at the top of a semi-circular magnetic loop. The Fokker-Planck equation is integrated to obtain the steady-state electron distribution throughout the loop. Coulomb scattering and energy losses and magnetic mirroring are included in the model. The resulting electron distributions are used to compute the radiative emissions. Sample images and spectra are presented. We are developing these models for the interpretation of the High Energy Solar Spectroscopic Imager (HESSI) x-ray/gamma ray data and coordinated microwave observations. The Fokker-Planck and radiation codes are available on the Web at http://hesperia.gsfc.nasa.gov/hessi/modelware.htm This work is supported in part by the NASA Sun-Earth Connection Program.

Hexagonalization of correlation functions II: two-particle contributions

NASA Astrophysics Data System (ADS)

Fleury, Thiago; Komatsu, Shota

2018-02-01

In this work, we compute one-loop planar five-point functions in N=4 super-Yang-Mills using integrability. As in the previous work, we decompose the correlation functions into hexagon form factors and glue them using the weight factors which depend on the cross-ratios. The main new ingredient in the computation, as compared to the four-point functions studied in the previous paper, is the two-particle mirror contribution. We develop techniques to evaluate it and find agreement with the perturbative results in all the cases we analyzed. In addition, we consider next-to-extremal four-point functions, which are known to be protected, and show that the sum of one-particle and two-particle contributions at one loop adds up to zero as expected. The tools developed in this work would be useful for computing higher-particle contributions which would be relevant for more complicated quantities such as higher-loop corrections and non-planar correlators.

A fully integrated neural recording amplifier with DC input stabilization.

PubMed

Mohseni, Pedram; Najafi, Khalil

2004-05-01

This paper presents a low-power low-noise fully integrated bandpass operational amplifier for a variety of biomedical neural recording applications. A standard two-stage CMOS amplifier in a closed-loop resistive feedback configuration provides a stable ac gain of 39.3 dB at 1 kHz. A subthreshold PMOS input transistor is utilized to clamp the large and random dc open circuit potentials that normally exist at the electrode-electrolyte interface. The low cutoff frequency of the amplifier is programmable up to 50 Hz, while its high cutoff frequency is measured to be 9.1 kHz. The tolerable dc input range is measured to be at least +/- 0.25 V with a dc rejection factor of at least 29 dB. The amplifier occupies 0.107 mm2 in die area, and dissipates 115 microW from a 3 V power supply. The total measured input-referred noise voltage in the frequency range of 0.1-10 kHz is 7.8 microVrms. It is fabricated using AMI 1.5 microm double-poly double-metal n-well CMOS process. This paper presents full characterization of the dc, ac, and noise performance of this amplifier through in vitro measurements in saline using two different neural recording electrodes.

Combining a Disturbance Observer with Triple-Loop Control Based on MEMS Accelerometers for Line-of-Sight Stabilization

PubMed Central

Huang, Yongmei; Deng, Chao; Ren, Wei; Wu, Qiongyan

2017-01-01

In the CCD-based fine tracking optical system (FTOS), the whole disturbance suppression ability (DSA) is the product of the inner loop and outer position loop. Traditionally, high sampling fiber-optic gyroscopes (FOGs) are added to the platform to stabilize the line-of-sight (LOS). However, because of the FOGs’ high cost and relatively big volume relative to the back narrow space of small rotating mirrors, we attempt in this work to utilize a cheaper and smaller micro-electro-mechanical system (MEMS) accelerometer to build the inner loop, replacing the FOG. Unfortunately, since accelerometers are susceptible to the low-frequency noise, according to the classical way of using accelerometers, the crucial low-frequency DSA of the system is insufficient. To solve this problem, in this paper, we propose an approach based on MEMS accelerometers combining disturbance observer (DOB) with triple-loop control (TLC) in which the composite velocity loop is built by acceleration integration and corrected by CCD. The DOB is firstly used to reform the platform, greatly improving the medium-frequency DSA. Then the composite velocity loop exchanges a part of medium-frequency performance for the low-frequency DSA. A detailed analysis and experiments verify the proposed method has a better DSA than the traditional way and could totally substitute FOG in the LOS stabilization. PMID:29149050

Isolation, characterization, and expression analyses of plant elicitor peptides (pep) genes in maize

USDA-ARS?s Scientific Manuscript database

PROPEP1, PROPEP 2, and PROPEP3 genes appear to have roles in a feedback loop that amplifies defense signaling pathways initiated by pathogens. We present evidence to support the role of peptides derived from PROPEP genes as endogenous elicitors that are generated in response to pathogens. The preval...

Development of a rapid assay to detect the jellyfish Cyanea nozakii using a loop-mediated isothermal amplification method.

PubMed

Liu, Zhongyuan; Dong, Zhijun; Liu, Dongyan

2016-07-01

Blooms of the harmful jellyfish Cyanea nozakii, which are a severe nuisance to fisheries and tourisms, frequently occur in the northern East China Sea, Yellow Sea, and Bohai Sea. To provide early warning of this species, a simple and effective molecular method for identifying C. nozakii was developed using the loop-mediated isothermal amplification method (LAMP). The LAMP assay is highly specific and uses a set of four primers that target six different regions on the mitochondrial cytochrome c oxidase subunit I (COI) gene of C. nozakii. The amplification conditions, including the dNTP and betaine concentrations, the inner primer to outer primer concentration ratio, reaction time and temperature, were optimized. The LAMP assay amplified DNA extracted from tissue samples of C. nozakii but did not amplify DNA from other common scyphozoans and hydrozoans collected in the same region. In addition, the LAMP assay was more sensitive than conventional PCR. Therefore, the established LAMP assay is a sensitive, specific, fast, and easily performed method for detection of C. nozakii at different stages in their life cycle.

Comparison of the Shack-Hartmann and plenoptic sensor in closed-loop adaptive optics system

NASA Astrophysics Data System (ADS)

Jiang, Pengzhi; Xu, Jieping; Liang, Yonghui; Mao, Hongjun

2016-03-01

The wavefront sensor is used in adaptive optics (AO) to detect the atmospheric distortion, which feeds back to the deformable mirror to compensate for this distortion. While the Shack-Hartmann sensor has been widely used, the plenoptic sensor was proposed in recent years. The two different wavefront sensing methods have different interpretations and numerical consequences, though they are both slope-based. The plenoptic sensor is compared with the Shack-Hartmann sensor in a closed-loop AO system. Simulations are performed to investigate their performances under closed-loop conditions. The plenoptic sensors both without and with modulation are discussed. The results show that the closed-loop performance of the plenoptic sensor without modulation is worse than that of the Shack-Hartmann sensor when the star for observation is brighter than magnitude 7, but better when the star is fainter. The closed-loop performance of the plenoptic sensor could be improved by modulation, except for the faint star. In summary, the limiting magnitude of the astronomical AO system may be improved by using the plenoptic sensor instead of the Shack-Hartmann sensor, and the modulation of the plenoptic sensor is more suitable for the bright star.

Determination of the structure and heating mechanisms of coronal loops from soft X-ray observations with the solar probe. [grazing incidence telescope

NASA Technical Reports Server (NTRS)

Davis, J. M.; Krieger, A. S.

1978-01-01

High resolution soft X-ray imaging from the solar probe is justified in terms of the expected scientific returns which include the determination of the temperature and density structure of a coronal loop. The advantages of the grazing incidence telescope over the multiple pinhole camera are discussed. An instrument package is described which includes a grazing incidence mirror, a thermal prefilter, a three position filter wheel and a focal plane detector baselined as an 800 by 800 back-illuminated charge coupled device. The structural assembly together with the data processing equipment would draw heavily on the designs being developed for the Solar Polar Mission.

The Digital Motion Control System for the Submillimeter Array Antennas

NASA Astrophysics Data System (ADS)

Hunter, T. R.; Wilson, R. W.; Kimberk, R.; Leiker, P. S.; Patel, N. A.; Blundell, R.; Christensen, R. D.; Diven, A. R.; Maute, J.; Plante, R. J.; Riddle, P.; Young, K. H.

2013-09-01

We describe the design and performance of the digital servo and motion control system for the 6-meter parabolic antennas of the Submillimeter Array (SMA) on Mauna Kea, Hawaii. The system is divided into three nested layers operating at a different, appropriate bandwidth. (1) A rack-mounted, real-time Unix system runs the position loop which reads the high resolution azimuth and elevation encoders and sends velocity and acceleration commands at 100 Hz to a custom-designed servo control board (SCB). (2) The microcontroller-based SCB reads the motor axis tachometers and implements the velocity loop by sending torque commands to the motor amplifiers at 558 Hz. (3) The motor amplifiers implement the torque loop by monitoring and sending current to the three-phase brushless drive motors at 20 kHz. The velocity loop uses a traditional proportional-integral-derivative (PID) control algorithm, while the position loop uses only a proportional term and implements a command shaper based on the Gauss error function. Calibration factors and software filters are applied to the tachometer feedback prior to the application of the servo gains in the torque computations. All of these parameters are remotely adjustable in the software. The three layers of the control system monitor each other and are capable of shutting down the system safely if a failure or anomaly occurs. The Unix system continuously relays the antenna status to the central observatory computer via reflective memory. In each antenna, a Palm Vx hand controller displays the complete system status and allows full local control of the drives in an intuitive touchscreen user interface. The hand controller can also be connected outside the cabin, a major convenience during the frequent reconfigurations of the interferometer. Excellent tracking performance ( 0.3‧‧ rms) is achieved with this system. It has been in reliable operation on 8 antennas for over 10 years and has required minimal maintenance.

Ultra-wideband microwave photonic filter with a high Q-factor using a semiconductor optical amplifier.

PubMed

Chen, Han

2017-04-01

An ultra-wideband microwave photonic filter (MPF) with a high quality (Q)-factor based on the birefringence effects in a semiconductor optical amplifier (SOA) is presented, and the theoretical fundamentals of the design are explained. The proposed MPF along orthogonal polarization in an active loop operates at up to a Ku-band and provides a tunable free spectral range from 15.44 to 19.44 GHz by controlling the SOA injection current. A prototype of the equivalent second-order infinite impulse response filter with a Q-factor over 6300 and a rejection ration exceeding 41 dB is experimentally demonstrated.

Microwave oscillator with reduced phase noise by negative feedback incorporating microwave signals with suppressed carrier

NASA Technical Reports Server (NTRS)

Dick, G. J.; Saunders, J.

1989-01-01

Oscillator configurations which reduce the effect of 1/f noise sources for both direct feedback and stabilized local oscillator (STALO) circuits are developed and analyzed. By appropriate use of carrier suppression, a small signal is generated which suffers no loss of loop phase information or signal-to-noise ratio. This small signal can be amplified without degradation by multiplicative amplifier noise, and can be detected without saturation of the detector. Together with recent advances in microwave resonator Qs, these circuit improvements will make possible lower phase noise than can be presently achieved without the use of cryogenic devices.

The Pathological and Physiological Roles of IL-6 Amplifier Activation

PubMed Central

Murakami, Masaaki; Hirano, Toshio

2012-01-01

The NFκB-triggered positive feedback loop for IL-6 signaling in type 1 collagen+ non-immune cells (IL-6 amplifier) was first discovered to be a synergistic signal that is activated following IL-17A and IL-6 stimulation in type 1 collagen+ non-immune cells. Subsequent disease models have shown that it can also be stimulated by the simultaneous activation of NFκB and STAT3, functions as a local chemokine inducer, and acts as a mechanism for local inflammation, particularly chronic ones like rheumatoid arthritis and a multiple sclerosis. Moreover, we have recently shown that hyper activation of the IL-6 amplifier via regional neural activation establishes a gateway for immune cells including autoreactive T cells to pass the blood-brain barrier at dorsal vessels in 5th lumbar cord. Here we review how the IL-6 amplifier is activated by neural activation and the physiological relevance of the gateway to the central nervous system. Accumulating evidences continues to suggest that the IL-6 amplifier offers a potential molecular mechanism for the relationship between neural activation and the development of inflammatory diseases, which could establish a new interdisciplinary field that fuses neurology and immunology. PMID:23136555

Einstein-Podolsky-Rosen paradox and quantum steering in a three-mode optomechanical system

NASA Astrophysics Data System (ADS)

He, Qiongyi; Ficek, Zbigniew

2014-02-01

We study multipartite entanglement, the generation of Einstein-Podolsky-Rosen (EPR) states, and quantum steering in a three-mode optomechanical system composed of an atomic ensemble located inside a single-mode cavity with a movable mirror. The cavity mode is driven by a short laser pulse, has a nonlinear parametric-type interaction with the mirror and a linear beam-splitter-type interaction with the atomic ensemble. There is no direct interaction of the mirror with the atomic ensemble. A threshold effect for the dynamics of the system is found, above which the system works as an amplifier and below which as an attenuator of the output fields. The threshold is determined by the ratio of the coupling strengths of the cavity mode to the mirror and to the atomic ensemble. It is shown that above the threshold, the system effectively behaves as a two-mode system in which a perfect bipartite EPR state can be generated, while it is impossible below the threshold. Furthermore, a fully inseparable tripartite entanglement and even further a genuine tripartite entanglement can be produced above and below the threshold. In addition, we consider quantum steering and examine the monogamy relations that quantify the amount of bipartite steering that can be shared between different modes. It is found that the mirror is more capable for steering of entanglement than the cavity mode. The two-way steering is found between the mirror and the atomic ensemble despite the fact that they are not directly coupled to each other, while it is impossible between the output of cavity mode and the ensemble which are directly coupled to each other.

Investigation of Closed Loop Adaptive Optics with the Deformable Mirror not in Pupil- Part 2: Theory (POSTPRINT)

DTIC Science & Technology

2008-07-01

Photo-Optical Instrumentation Engineers (SPIE) Conference 6272, July 2006. 2. F. P. Wildi , G. Brusa, A. Riccardi, M. Lloyd-Hart, H. M. Martin, and L. M...2003. 3. G. Brusa, A. Riccardi, P. Salinari, F. P. Wildi , M. Lloyd-Hart, H. M. Martin, R. Allen, D. Fisher, D. L. Miller, R. Biasi, D. Gallieni, and F

Micro EEG/ECG signal’s chopper-stabilization amplifying chip for novel dry-contact electrode

NASA Astrophysics Data System (ADS)

Sun, Jianhui; Wang, Chunxing; Wang, Gongtang; Wang, Jinhui; Hua, Qing; Cheng, Chuanfu; Cai, Xinxia; Yin, Tao; Yu, Yang; Yang, Haigang; Li, Dengwang

2017-02-01

Facing the body’s EEG (electroencephalograph, 0.5–100 Hz, 5–100 μV) and ECG’s (electrocardiogram, < 100 {Hz}, 0.01–5 mV) micro signal detection requirement, this paper develops a pervasive application micro signal detection ASIC chip with the chopping modulation/demodulation method. The chopper-stabilization circuit with the RRL (ripple reduction loop) circuit is to suppress the ripple voltage, which locates at the single-stage amplifier’s outputting terminal. The single-stage chopping core’s noise has been suppressed too, and it is beneficial for suppressing noises of post-circuit. The chopping core circuit uses the PFB (positive feedback loop) to increase the inputting resistance, and the NFB (negative feedback loop) to stabilize the 40 dB intermediate frequency gain. The cascaded switch-capacitor sample/hold circuit has been used for deleting spike noises caused by non-ideal MOS switches, and the VGA/BPF (voltage gain amplifier/band pass filter) circuit is used to tune the chopper system’s gain/bandwidth digitally. Assisted with the designed novel dry-electrode, the real test result of the chopping amplifying circuit gives some critical parameters: 8.1 μW/channel, 0.8 μVrms (@band-width = 100 Hz), 4216–11220 times digitally tuning gain range, etc. The data capture system uses the NI CO’s data capturing DAQmx interface, and the captured micro EEG/ECG’s waves are real-time displayed with the PC-Labview. The proposed chopper system is a unified EEG/ECG signal’s detection instrument and has a critical real application value. Project supported by the National Natural Science Foundation of China (Nos. 61527815, 31500800, 61501426, 61471342), the National Key Basic Research Plan (No. 2014CB744600), the Beijing Science and Technology Plan (No. Z141100000214002), and the Chinese Academy of Sciences’ Key Project (No. KJZD-EW-L11-2).

Design of a prototype position actuator for the primary mirror segments of the European Extremely Large Telescope

NASA Astrophysics Data System (ADS)

Jiménez, A.; Morante, E.; Viera, T.; Núñez, M.; Reyes, M.

2010-07-01

European Extremely Large Telescope (E-ELT) based in 984 primary mirror segments achieving required optical performance; they must position relatively to adjacent segments with relative nanometer accuracy. CESA designed M1 Position Actuators (PACT) to comply with demanding performance requirements of EELT. Three PACT are located under each segment controlling three out of the plane degrees of freedom (tip, tilt, piston). To achieve a high linear accuracy in long operational displacements, PACT uses two stages in series. First stage based on Voice Coil Actuator (VCA) to achieve high accuracies in very short travel ranges, while second stage based on Brushless DC Motor (BLDC) provides large stroke ranges and allows positioning the first stage closer to the demanded position. A BLDC motor is used achieving a continuous smoothly movement compared to sudden jumps of a stepper. A gear box attached to the motor allows a high reduction of power consumption and provides a great challenge for sizing. PACT space envelope was reduced by means of two flat springs fixed to VCA. Its main characteristic is a low linear axial stiffness. To achieve best performance for PACT, sensors have been included in both stages. A rotary encoder is included in BLDC stage to close position/velocity control loop. An incremental optical encoder measures PACT travel range with relative nanometer accuracy and used to close the position loop of the whole actuator movement. For this purpose, four different optical sensors with different gratings will be evaluated. Control strategy show different internal closed loops that work together to achieve required performance.

Adaptive optics system for Cassegrain focus of SUBARU 8.2-m telescope

NASA Astrophysics Data System (ADS)

Takami, Hideki; Takato, Naruhisa; Otsubo, Masashi; Kanzawa, Tomio; Kamata, Yukiko; Nakashima, Koji; Iye, Masanori

1998-09-01

The adaptive optics system for Subaru 8.2m telescope of the National Astronomical Observatory Japan has been developed for the Cassegrain ear-IR instruments, CIAO and IRCS. The system consists of a wavefront curvature sensor with 36 subaperture photon-counting avalanche photodiode modules and a bimorph deformable mirror with 36 electrodes. The expected Strehl ratio at K band exceeds 0.4 for objects that are located close enough to a bright guide star as faint as R equals 16 mag at the median seeing of 0.45 arcsec at Mauna Kea. The system will be in operation in 1999 as a natural guide star system, and will eventually be upgraded to a laser guide star system in cooperating an IR wavefront tilt sensor to provide nearly full sky. The construction of this common use system to Subaru telescope is now underway in our laboratory in Tokyo. Prior to starting the fabrication of this common use system, a full size prototype system was constructed and tested with the 1.6 m IR telescope at our observatory in Tokyo. This system has the identical optical design, deformable mirror, loop control computer to those for the Subaru system, while the wavefront sensing detectors were less-sensitive analog APDs. We succeeded in getting closed loop images of stars in K band with diffraction limited core. The Strehl ratio was around 0.5 and the factor of improvement was about 20 at K-band under the average seeing of 2 arcsec during the observation. The loop sped of the system was 2 K corrections per second.

Detection of HbsAg and hATIII genetically modified goats (Caprahircus) by loop-mediated isothermal amplification.

PubMed

Tao, Chenyu; Zhang, Qingde; Zhai, Shanli; Liu, Bang

2013-11-01

In this study, sensitive and rapid detection systems were designed using a loop-mediated isothermal amplification (LAMP) method to detect the genetically modified goats. A set of 4 primers were designed for each exogenous nucleic acids HBsAg and hATIII. The DNA samples were first amplified with the outer and inner primers and released a single-stranded DNA,of which both ends were stem-loop structure. Then one inner primer hybridized with the loop, and initiated displacement synthesis in less than 1 h. The result could be visualized by both agarose gel electrophoresis and unaided eyes directly after adding SYBR GREEN 1. The detection limit of LAMP was ten copies of target molecules, indicating that LAMP was tenfold more sensitive than the classical PCR. Furthermore, all the samples of genetically modified goats were tested positively by LAMP, and the results demonstrated that the LAMP was a rapid and sensitive method for detecting the genetically modified organism.

Cryogenic Scan Mechanism for Fourier Transform Spectrometer

NASA Technical Reports Server (NTRS)

Brasunas, John C.; Francis, John L.

2011-01-01

A compact and lightweight mechanism has been developed to accurately move a Fourier transform spectrometer (FTS) scan mirror (a cube corner) in a near-linear fashion with near constant speed at cryogenic temperatures. This innovation includes a slide mechanism to restrict motion to one dimension, an actuator to drive the motion, and a linear velocity transducer (LVT) to measure the speed. The cube corner mirror is double-passed in one arm of the FTS; double-passing is required to compensate for optical beam shear resulting from tilting of the moving cube corner. The slide, actuator, and LVT are off-the-shelf components that are capable of cryogenic vacuum operation. The actuator drives the slide for the required travel of 2.5 cm. The LVT measures translation speed. A proportional feedback loop compares the LVT voltage with the set voltage (speed) to derive an error signal to drive the actuator and achieve near constant speed. When the end of the scan is reached, a personal computer reverses the set voltage. The actuator and LVT have no moving parts in contact, and have magnetic properties consistent with cryogenic operation. The unlubricated slide restricts motion to linear travel, using crossed roller bearings consistent with 100-million- stroke operation. The mechanism tilts several arc seconds during transport of the FTS mirror, which would compromise optical fringe efficiency when using a flat mirror. Consequently, a cube corner mirror is used, which converts a tilt into a shear. The sheared beam strikes (at normal incidence) a flat mirror at the end of the FTS arm with the moving mechanism, thereby returning upon itself and compensating for the shear

Last results of MADRAS, a space active optics demonstrator

NASA Astrophysics Data System (ADS)

Laslandes, Marie; Hourtoule, Claire; Hugot, Emmanuel; Ferrari, Marc; Devilliers, Christophe; Liotard, Arnaud; Lopez, Céline; Chazallet, Frédéric

2017-11-01

The goal of the MADRAS project (Mirror Active, Deformable and Regulated for Applications in Space) is to highlight the interest of Active Optics for the next generation of space telescope and instrumentation. Wave-front errors in future space telescopes will mainly come from thermal dilatation and zero gravity, inducing large lightweight primary mirrors deformation. To compensate for these effects, a 24 actuators, 100 mm diameter deformable mirror has been designed to be inserted in a pupil relay. Within the project, such a system has been optimized, integrated and experimentally characterized. The system is designed considering wave-front errors expected in 3m-class primary mirrors, and taking into account space constraints such as compactness, low weight, low power consumption and mechanical strength. Finite Element Analysis allowed an optimization of the system in order to reach a precision of correction better than 10 nm rms. A dedicated test-bed has been designed to fully characterize the integrated mirror performance in representative conditions. The test set up is made of three main parts: a telescope aberrations generator, a correction loop with the MADRAS mirror and a Shack-Hartman wave-front sensor, and PSF imaging. In addition, Fizeau interferometry monitors the optical surface shape. We have developed and characterized an active optics system with a limited number of actuators and a design fitting space requirements. All the conducted tests tend to demonstrate the efficiency of such a system for a real-time, in situ wave-front. It would allow a significant improvement for future space telescopes optical performance while relaxing the specifications on the others components.

FPGA-based real time controller for high order correction in EDIFISE

NASA Astrophysics Data System (ADS)

Rodríguez-Ramos, L. F.; Chulani, H.; Martín, Y.; Dorta, T.; Alonso, A.; Fuensalida, J. J.

2012-07-01

EDIFISE is a technology demonstrator instrument developed at the Institute of Astrophysics of the Canary Islands (IAC), intended to explore the feasibility of combining Adaptive Optics with attenuated optical fibers in order to obtain high spatial resolution spectra at the surroundings of a star, as an alternative to coronagraphy. A simplified version with only tip tilt correction has been tested at the OGS telescope in Observatorio del Teide (Canary islands, Spain) and a complete version is intended to be tested at the OGS and at the WHT telescope in Observatorio del Roque de los Muchachos, (Canary Islands, Spain). This paper describes the FPGA-based real time control of the High Order unit, responsible of the computation of the actuation values of a 97-actuactor deformable mirror (11x11) with the information provided by a configurable wavefront sensor of up to 16x16 subpupils at 500 Hz (128x128 pixels). The reconfigurable logic hardware will allow both zonal and modal control approaches, will full access to select which mode loops should be closed and with a number of utilities for influence matrix and open loop response measurements. The system has been designed in a modular way to allow for easy upgrade to faster frame rates (1500 Hz) and bigger wavefront sensors (240x240 pixels), accepting also several interfaces from the WFS and towards the mirror driver. The FPGA-based (Field Programmable Gate Array) real time controller provides bias and flat-fielding corrections, subpupil slopes to modal matrix computation for up to 97 modes, independent servo loop controllers for each mode with user control for independent loop opening or closing, mode to actuator matrix computation and non-common path aberration correction capability. It also provides full housekeeping control via UPD/IP for matrix reloading and full system data logging.

ARC length control for plasma welding

NASA Technical Reports Server (NTRS)

Iceland, William F. (Inventor)

1988-01-01

A control system to be used with a plasma arc welding apparatus is disclosed. The plasma arc welding apparatus includes a plasma arc power supply, a contactor, and an electrode assembly for moving the electrode relative to a work piece. The electrode assembly is raised or lowered by a drive motor. The present apparatus includes a plasma arc adapter connected across the power supply to measure the voltage across the plasma arc. The plasma arc adapter forms a dc output signal input to a differential amplifier. A second input is defined by an adjustable resistor connected to a dc voltage supply to permit operator control. The differential amplifier forms an output difference signal provided to an adder circuit. The adder circuit then connects with a power amplifier which forms the driving signal for the motor. In addition, the motor connects to a tachometor which forms a feedback signal delivered to the adder to provide damping, therby avoiding servo loop overshoot.

Resolution enhancement of fiber Bragg grating temperature sensor using a cavity ring-down technique

NASA Astrophysics Data System (ADS)

Yarai, Atsushi; Hara, Katsuyuki

2018-02-01

A new technique for enhancing the measurement resolution of a fiber Bragg grating (FBG) temperature sensor is proposed. This technique uses a cavity ring-down approach to amplify optical intensity by accumulating unremarkable intensity changes. A wavelength-stabilized optical pulse with a width of 10 ns rotates several times inside an optical fiber loop that contains a FBG sensor. In other words, the loop system functions as an integrator of slight intensity transition. A temperature resolution of at least 0.02 °C was achieved at 20.0 °C. Resolution with this technique is at least five times higher than previous techniques.

Development of Loop-Mediated Isothermal Amplification Assay for Detection of Entamoeba histolytica▿

PubMed Central

Liang, Shih-Yu; Chan, Yun-Hsien; Hsia, Kan-Tai; Lee, Jing-Lun; Kuo, Ming-Chu; Hwa, Kuo-Yuan; Chan, Chi-Wen; Chiang, Ting-Yi; Chen, Jung-Sheng; Wu, Fang-Tzy; Ji, Dar-Der

2009-01-01

A novel one-step, closed-tube, loop-mediated isothermal amplification (LAMP) assay for detecting Entamoeba histolytica, one of the leading causes of morbidity in developing countries, was developed. The sensitivity of the LAMP assay is 1 parasite per reaction. A total of 130 clinical samples were analyzed, and the results compared with those of conventional nested PCR to validate the practicability of this assay. No DNA was amplified from other diarrheal pathogens, such as other Entamoeba species, bacteria, and viruses. These results indicate that LAMP is a rapid, simple, and valuable diagnostic tool for epidemiological studies of amebiasis. PMID:19321720

Nonlinear cellular dynamics of keratinocytes in normal and psoriatic epidermis under action of UV radiation

NASA Astrophysics Data System (ADS)

Stolnitz, Mikhail M.; Medvedev, Boris A.; Gribko, Tatyana V.

2004-05-01

The semi-phenomenological model of epidermal cell dynamics is submitted. The model takes into account three types of basal layer keratinocytes (stem, transient amplifying, terminally differentiated), distribution of first two types cells on mitotic cycle stages and resting states, keratinocytes-lymphocytes interactions that provide a positive feedback loop, influence of more differentiated cells on their progenitors that provide a negative feedback loop. Simplified model are developed and its stationary solutions are received. The opportunity of interpretation of some received modes as corresponding to various stages of psoriasis is discussed. Influence of UV-radiation on transitions between various modes of epidermis functioning is qualitatively analyzed.

Evaluation of 3M molecular detection system and ANSR pathogen detection system for rapid detection of salmonella from egg products

USDA-ARS?s Scientific Manuscript database

Loop-mediated isothermal amplification (LAMP) is a novel simple detection technology that amplifies DNA with high speed, efficiency, and specificity under isothermal conditions. The objective of this study was to evaluate the effectiveness of 3M Molecular Detection System (MDS) and ANSR Pathogen Det...

Simple Optoelectronic Feedback in Microwave Oscillators

NASA Technical Reports Server (NTRS)

Maleki, Lute; Iltchenko, Vladimir

2009-01-01

A proposed method of stabilizing microwave and millimeter-wave oscillators calls for the use of feedback in optoelectronic delay lines characterized by high values of the resonance quality factor (Q). The method would extend the applicability of optoelectronic feedback beyond the previously reported class of optoelectronic oscillators that comprise two-port electronic amplifiers in closed loops with high-Q feedback circuits.

Continuous-time ΣΔ ADC with implicit variable gain amplifier for CMOS image sensor.

PubMed

Tang, Fang; Bermak, Amine; Abbes, Amira; Benammar, Mohieddine Amor

2014-01-01

This paper presents a column-parallel continuous-time sigma delta (CTSD) ADC for mega-pixel resolution CMOS image sensor (CIS). The sigma delta modulator is implemented with a 2nd order resistor/capacitor-based loop filter. The first integrator uses a conventional operational transconductance amplifier (OTA), for the concern of a high power noise rejection. The second integrator is realized with a single-ended inverter-based amplifier, instead of a standard OTA. As a result, the power consumption is reduced, without sacrificing the noise performance. Moreover, the variable gain amplifier in the traditional column-parallel read-out circuit is merged into the front-end of the CTSD modulator. By programming the input resistance, the amplitude range of the input current can be tuned with 8 scales, which is equivalent to a traditional 2-bit preamplification function without consuming extra power and chip area. The test chip prototype is fabricated using 0.18 μm CMOS process and the measurement result shows an ADC power consumption lower than 63.5 μW under 1.4 V power supply and 50 MHz clock frequency.

Comparison of sensitivity and resolution load sensor at various configuration polymer optical fiber

NASA Astrophysics Data System (ADS)

Arifin, A.; Yusran, Miftahuddin, Abdullah, Bualkar; Tahir, Dahlang

2017-01-01

This study uses a load sensor with a macro-bending on polymer optical fiber loop model which is placed between two plates with a buffer spring. The load sensor with light intensity modulation principle is an infrared LED emits light through the polymer optical fiber then received by the phototransistor and amplifier. Output voltage from the amplifier continued to arduino sequence and displayed on the computer. Load augment on the sensor resulted in an increase of curvature on polymer optical fibers that can cause power losses gets bigger too. This matter will result in the intensity of light that received by phototransistor getting smaller, so that the output voltage that ligable on computer will be getting smaller too. The sensitivity and resolution load sensors analyzed based on configuration with various amount of loops, imperfection on the jacket, and imperfection at the cladding and core of polymer optical fiber. The results showed that the augment on the amount of load, imperfection on the jacket and imperfection on the sheath and core polymer optical fiber can improve the sensitivity and resolution of the load sensor. The best sensors resolution obtained on the number of loops 4 with imperfection 8 on the core and cladding polymer optical fiber that is 0.037 V/N and 0,026 N. The advantages of the load sensor based on polymers optical fiber are easy to make, low cost and simple to use measurement methods.

Temperature feedback control for long-term carrier-envelope phase locking.

PubMed

Yun, Chenxia; Chen, Shouyuan; Wang, He; Chini, Michael; Chang, Zenghu

2009-09-20

We report a double feedback loop for the improvement of the carrier-envelope phase stabilization of a chirped mirror based femtosecond laser oscillator. By combining the control of the Ti:sapphire crystal temperature and the modulation of the pump power, the carrier envelope offset frequency, fCEO, was locked for close to 20 h, which is much longer than the typical phase stabilization time with only pump power modulation.

The low-order wavefront control system for the PICTURE-C mission: preliminary testbed results from the Shack-Hartmann sensor

NASA Astrophysics Data System (ADS)

Howe, Glenn A.; Mendillo, Christopher B.; Hewawasam, Kuravi; Martel, Jason; Finn, Susanna C.; Cook, Timothy A.; Chakrabarti, Supriya

2017-09-01

The Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C) mission will directly image debris disks and exozodiacal dust around three nearby stars from a high-altitude balloon using a vector vortex coronagraph. We present experimental results of the PICTURE-C low-order wavefront control (LOWFC) system utilizing a Shack-Hartmann (SH) sensor in an instrument testbed. The SH sensor drives both the alignment of the telescope secondary mirror using a 6-axis Hexapod and a surface parallel array deformable mirror to remove residual low-order aberrations. The sensor design and actuator calibration methods are discussed and the preliminary LOWFC closed-loop performance is shown to stabilize a reference wavefront to an RMS error of 0.30 +/- 0.29 nm.

Optical-Path-Difference Linear Mechanism for the Panchromatic Fourier Transform Spectrometer

NASA Technical Reports Server (NTRS)

Blavier, Jean-Francois L.; Heverly, Matthew C.; Key, Richard W.; Sander, Stanley P.

2011-01-01

A document discusses a mechanism that uses flex-pivots in a parallelogram arrangement to provide frictionless motion with an unlimited lifetime. A voicecoil actuator drives the parallelogram over the required 5-cm travel. An optical position sensor provides feedback for a servo loop that keeps the velocity within 1 percent of expected value. Residual tip/tilt error is compensated for by a piezo actuator that drives the interferometer mirror. This mechanism builds on previous work that targeted ground-based measurements. The main novelty aspects include cryogenic and vacuum operation, high reliability for spaceflight, compactness of the design, optical layout compatible with the needs of an imaging FTS (i.e. wide overall field-of-view), and mirror optical coatings to cover very broad wavelength range (i.e., 0.26 to 15 m).

Latest experience in design of piezoelectric-driven fine-steering mirrors

NASA Astrophysics Data System (ADS)

Marth, Harry; Donat, Michael; Pohlhammer, Charles F.

1992-01-01

The European Space Organization (ESO) requested Physik Instrumente (PI) to develop a system to compensate for atmospherically induced image jitter in astronomical telescopes. The product, designated S-380 by PI, is a sophisticated adaptive optic system using closed loop piezoelectric actuators and momentum compensation to significantly improve telescope resolution during long integrations by correcting for image jitter in real time. Optimizing the design of this system involved solving several interdependent problems, including: (1) selection of the motion system, (2) arrangement of the pivot points and actuators, (3) momentum compensation, and (4) selection of the sensor system. This paper presents the trade-offs leading to final design of the S-380 system, some supporting technical analysis and ongoing efforts at PI to provide fast tilting platforms for larger mirrors.

An integrated nonlinear optical loop mirror in silicon photonics for all-optical signal processing

NASA Astrophysics Data System (ADS)

Wang, Zifei; Glesk, Ivan; Chen, Lawrence R.

2018-02-01

The nonlinear optical loop mirror (NOLM) has been studied for several decades and has attracted considerable attention for applications in high data rate optical communications and all-optical signal processing. The majority of NOLM research has focused on silica fiber-based implementations. While various fiber designs have been considered to increase the nonlinearity and manage dispersion, several meters to hundreds of meters of fiber are still required. On the other hand, there is increasing interest in developing photonic integrated circuits for realizing signal processing functions. In this paper, we realize the first-ever passive integrated NOLM in silicon photonics and demonstrate its application for all-optical signal processing. In particular, we show wavelength conversion of 10 Gb/s return-to-zero on-off keying (RZ-OOK) signals over a wavelength range of 30 nm with error-free operation and a power penalty of less than 2.5 dB, we achieve error-free nonreturn to zero (NRZ)-to-RZ modulation format conversion at 10 Gb/s also with a power penalty of less than 2.8 dB, and we obtain error-free all-optical time-division demultiplexing of a 40 Gb/s RZ-OOK data signal into its 10 Gb/s tributary channels with a maximum power penalty of 3.5 dB.

Holographic Adaptive Laser Optics System

NASA Astrophysics Data System (ADS)

Andersen, G.; Ghebremichael, F.

2011-09-01

We have created a new adaptive optics system using a holographic modal wavefront sensing method with the autonomous (computer-free) closed-loop control of a MEMS deformable mirror (DM). A multiplexed hologram is recorded using the maximum and minimum actuator positions on the deformable mirror as the “modes”. On reconstruction, an input beam is diffracted into pairs of focal spots and the ratio of the intensities of certain pairs determines the absolute wavefront phase at a particular actuator location. The wavefront measurement is made using fast, sensitive silicon photomultiplier arrays with the parallel outputs directly controlling individual actuators in the MEMS DM. In this talk, we will present the results from an all-optical, ultra-compact system that runs in closed-loop without the need for a computer. The speed is limited only by the response time of any given DM actuator and not the number of actuators. In our case, our 32-actuator prototype device already operates at 10 kHz and our next generation system is being designed for > 100 kHz. As a modal system, it is largely insensitive to scintillation and obscuration and is thus ideal for extreme adaptive optics applications. We will present information on how HALOS can be used for image correction and beam propagation as well as several other novel applications.

Optomechanical entanglement via non-degenerate parametric interactions

NASA Astrophysics Data System (ADS)

Ahmed, Rizwan; Qamar, Shahid

2017-10-01

We present a scheme for the optomechanical entanglement between a micro-mechanical mirror and the field inside a bimodal cavity system using a non-degenerate optical parametric amplifier (NOPA). Our results show that the introduction of NOPA makes the entanglement stronger or more robust against the mean number of average thermal phonons and cavity decay. Interestingly, macroscopic entanglement depends upon the choice of the phase associated with classical field driving NOPA. We also consider the effects of input laser power on optomechanical entanglement.

Active mirror amplifiers for HiPER kiloJoule beamlines

NASA Astrophysics Data System (ADS)

Chanteloup, J.-C.; Lucianetti, A.

2013-11-01

A major challenge the HiPER [1] project is facing is to derive laser architectures satisfying simultaneously all HiPER requirements; among them, high wall-plug efficiency (15 to 20%) and repetition rate (around 10 Hz) are the most challenging constraints. Several groups over the world are actively pursuing research in the field of High average power Diode Pumped Solid State Lasers (DPSSL) [2]. We propose a comprehensive solution for a 1 kJ DPSSL beamline as the unit brick of a 12 beams bundle.

Multiple Channel Laser Beam Combination and Phasing Using Stimulated Brillouin Scattering in Optical Fibers

DTIC Science & Technology

2005-12-22

etched glass into a waveguide containing methane gas (the SBS medium). The experiment compared the reflection from the SBS cell with that of a mirror...proposed tellurite glass as a candidate for fiber devices.105 Their work has led to the development of a number of rare-earth doped fiber lasers and...Tellurite glasses have also been quite successful as Raman amplifiers110,111 demonstrating over 90 times higher Raman gain than silica-based devices

Multiple Channel Laser Beam Combination and Phasing Using Stimulated Brillouin Scattering in Optical Fibers

DTIC Science & Technology

2005-12-01

etched glass into a waveguide containing methane gas (the SBS medium). The experiment compared the reflection from the SBS cell with that of a mirror...proposed tellurite glass as a candidate for fiber devices.105 Their work has led to the development of a number of rare-earth doped fiber lasers and...Tellurite glasses have also been quite successful as Raman amplifiers110,111 demonstrating over 90 times higher Raman gain than silica-based devices

Alpha channeling in a rotating plasma.

PubMed

Fetterman, Abraham J; Fisch, Nathaniel J

2008-11-14

The wave-particle alpha-channeling effect is generalized to include rotating plasma. Specifically, radio frequency waves can resonate with alpha particles in a mirror machine with ExB rotation to diffuse the alpha particles along constrained paths in phase space. Of major interest is that the alpha-particle energy, in addition to amplifying the rf waves, can directly enhance the rotation energy which in turn provides additional plasma confinement in centrifugal fusion reactors. An ancillary benefit is the rapid removal of alpha particles, which increases the fusion reactivity.

A Comparative Analysis of CMUT Receiving Architectures for the Design Optimization of Integrated Transceiver Front Ends.

PubMed

Sautto, Marco; Savoia, Alessandro Stuart; Quaglia, Fabio; Caliano, Giosue; Mazzanti, Andrea

2017-05-01

A formal comparison between fundamental RX amplifier configurations for capacitive micromachined ultrasonic transducers (CMUTs) is proposed in this paper. The impact on both RX and the pulse-echo frequency response and on the output SNR is thoroughly analyzed and discussed. It is shown that the resistive-feedback amplifier yields a bandpass RX frequency response, while both open-loop voltage and capacitive-feedback amplifiers exhibit a low-pass frequency response. For a given power dissipation, it is formally proved that a capacitive-feedback amplifier provides a remarkable SNR improvement against the commonly adopted resistive feedback stage, achieved at the expense of a reduced pulse-echo center frequency, making its use convenient in low-frequency and midfrequency ultrasound imaging applications. The advantage mostly comes from a much lower noise contributed by the active devices, especially with low- Q , broadband transducers. The results of the analysis are applied to the design of a CMUT front end in BIPOLAR-CMOS-DMOS Silicon-on-Insulator technology operating at 10-MHz center frequency. It comprises a low-power RX amplifier, a high-voltage Transmission/Reception switch, and a 100-V TX driver. Extensive electrical characterization, pulse-echo measurements, and imaging results are shown. Compared with previously reported CMUT front ends, this transceiver demonstrates the highest dynamic range and state-of-the-art noise performance with an RX amplifier power dissipation of 1 mW.

HALOS: fast, autonomous, holographic adaptive optics

NASA Astrophysics Data System (ADS)

Andersen, Geoff P.; Gelsinger-Austin, Paul; Gaddipati, Ravi; Gaddipati, Phani; Ghebremichael, Fassil

2014-08-01

We present progress on our holographic adaptive laser optics system (HALOS): a compact, closed-loop aberration correction system that uses a multiplexed hologram to deconvolve the phase aberrations in an input beam. The wavefront characterization is based on simple, parallel measurements of the intensity of fixed focal spots and does not require any complex calculations. As such, the system does not require a computer and is thus much cheaper, less complex than conventional approaches. We present details of a fully functional, closed-loop prototype incorporating a 32-element MEMS mirror, operating at a bandwidth of over 10kHz. Additionally, since the all-optical sensing is made in parallel, the speed is independent of actuator number - running at the same bandwidth for one actuator as for a million.

Plant Stem and Leaf Movements in Microgravity. Preliminary Results from a Study Using the EMCS Hardware on the ISS

NASA Astrophysics Data System (ADS)

Johnsson, Anders; Bokn Solheim, Bjarte Gees; Henning Iversen, Tor

2008-06-01

In the 72 days long MULTIGEN-1 experiment movements of Arabidopsis thaliana were recorded using the European Modular Cultivation System, EMCS. One main goal in the experiment was to study possible oscillatory movements of plant parts in weightlessness and under acceleration pulses on centrifuge rotors. Recording was made by video sampling of the plants in cultivation chambers every 5 min. The camera + mirror set-up in the EMCS was developed by alternating the mirror positions to get 'stereoscopic' 2D pictures so that 3D-movements could be constructed. Studies of rhythmic, helical movements of shoots as well as of rhythmic movements of leaves are discussed. It is concluded that gravity amplifies self-sustained circumnutations. Also gravitropical reactions of leaves were successfully documented. The results are of importance, for example in the discussion since Charles Darwin's days on the influence of gravity on circumnutations.

Mitochondrial D-loop sequence of domesticated waterfowl in Central Java: goose and muscovy duck

NASA Astrophysics Data System (ADS)

Susanti, R.; Iswari, R. S.

2018-03-01

This study aims to determine the genetic characterization of domesticated waterfowl (goose and Muscovy duck) in Central Java based on a D-loop mtDNA gene. The D-loop gene was amplified using PCR technique by specific primer and sequenced using dideoxy termination method. Multiple alignments of D-loop gene obtained were 710 nucleotides at position 74 to 783 at the 5’ end (for goose) and 712 nucleotides at position 48 to 759 at the 5’ end (for Muscovy duck). The results of the polymorphism analysis on D-loop sequences of muscovy duck produced 3 haplotypes. In the D-loop gene of goose does not show polymorphism, with substitution at G117A. Phylogenetic trees reconstructions of goose and Muscovy duck, which was collected during this research compared with another species from Anser, Chairina and Anas was generated 2 forms of clusters. The first group consists of all kind of Muscovy duck together with Chairina moschata and Anas, while the second group consists of all geese and Anser cygnoides the other. The determination of Muscovy duck and geese identity can be distinguished from the genetic marker information. Based on the phylogenetic analysis, it can be concluded that the Muscovy duck is closely related to Chairina moschata, while geese is closely related to Anser cygnoides.

Designing new classes of high-power, high-brightness VECSELs

NASA Astrophysics Data System (ADS)

Moloney, J. V.; Zakharian, A. R.; Hader, J.; Koch, Stephan W.

2005-10-01

Optically-pumped vertical external cavity semiconductor lasers offer the exciting possibility of designing kW-class solid state lasers that provide significant advantages over their doped YAG, thin-disk YAG and fiber counterparts. The basic VECSEL/OPSL (optically-pumped semiconductor laser) structure consists of a very thin (approximately 6 micron thick) active mirror consisting of a DBR high-reflectivity stack followed by a multiple quantum well resonant periodic (RPG) structure. An external mirror (reflectivity typically between 94%-98%) provides conventional optical feedback to the active semiconductor mirror chip. The "cold" cavity needs to be designed to take into account the semiconductor sub-cavity resonance shift with temperature and, importantly, the more rapid shift of the semiconductor material gain peak with temperature. Thermal management proves critical in optimizing the device for serious power scaling. We will describe a closed-loop procedure that begins with a design of the semiconductor active epi structure. This feeds into the sub-cavity optimization, optical and thermal transport within the active structure and thermal transport though the various heat sinking elements. Novel schemes for power scaling beyond current record performances will be discussed.

A Low-Noise Transimpedance Amplifier for BLM-Based Ion Channel Recording.

PubMed

Crescentini, Marco; Bennati, Marco; Saha, Shimul Chandra; Ivica, Josip; de Planque, Maurits; Morgan, Hywel; Tartagni, Marco

2016-05-19

High-throughput screening (HTS) using ion channel recording is a powerful drug discovery technique in pharmacology. Ion channel recording with planar bilayer lipid membranes (BLM) is scalable and has very high sensitivity. A HTS system based on BLM ion channel recording faces three main challenges: (i) design of scalable microfluidic devices; (ii) design of compact ultra-low-noise transimpedance amplifiers able to detect currents in the pA range with bandwidth >10 kHz; (iii) design of compact, robust and scalable systems that integrate these two elements. This paper presents a low-noise transimpedance amplifier with integrated A/D conversion realized in CMOS 0.35 μm technology. The CMOS amplifier acquires currents in the range ±200 pA and ±20 nA, with 100 kHz bandwidth while dissipating 41 mW. An integrated digital offset compensation loop balances any voltage offsets from Ag/AgCl electrodes. The measured open-input input-referred noise current is as low as 4 fA/√Hz at ±200 pA range. The current amplifier is embedded in an integrated platform, together with a microfluidic device, for current recording from ion channels. Gramicidin-A, α-haemolysin and KcsA potassium channels have been used to prove both the platform and the current-to-digital converter.

A Low-Noise Transimpedance Amplifier for BLM-Based Ion Channel Recording

PubMed Central

Crescentini, Marco; Bennati, Marco; Saha, Shimul Chandra; Ivica, Josip; de Planque, Maurits; Morgan, Hywel; Tartagni, Marco

2016-01-01

High-throughput screening (HTS) using ion channel recording is a powerful drug discovery technique in pharmacology. Ion channel recording with planar bilayer lipid membranes (BLM) is scalable and has very high sensitivity. A HTS system based on BLM ion channel recording faces three main challenges: (i) design of scalable microfluidic devices; (ii) design of compact ultra-low-noise transimpedance amplifiers able to detect currents in the pA range with bandwidth >10 kHz; (iii) design of compact, robust and scalable systems that integrate these two elements. This paper presents a low-noise transimpedance amplifier with integrated A/D conversion realized in CMOS 0.35 μm technology. The CMOS amplifier acquires currents in the range ±200 pA and ±20 nA, with 100 kHz bandwidth while dissipating 41 mW. An integrated digital offset compensation loop balances any voltage offsets from Ag/AgCl electrodes. The measured open-input input-referred noise current is as low as 4 fA/√Hz at ±200 pA range. The current amplifier is embedded in an integrated platform, together with a microfluidic device, for current recording from ion channels. Gramicidin-A, α-haemolysin and KcsA potassium channels have been used to prove both the platform and the current-to-digital converter. PMID:27213382

Multi-Megawatt-Scale Power-Hardware-in-the-Loop Interface for Testing Ancillary Grid Services by Converter-Coupled Generation: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koralewicz, Przemyslaw J; Gevorgian, Vahan; Wallen, Robert B

Power-hardware-in-the-loop (PHIL) is a simulation tool that can support electrical systems engineers in the development and experimental validation of novel, advanced control schemes that ensure the robustness and resiliency of electrical grids that have high penetrations of low-inertia variable renewable resources. With PHIL, the impact of the device under test on a generation or distribution system can be analyzed using a real-time simulator (RTS). PHIL allows for the interconnection of the RTS with a 7 megavolt ampere (MVA) power amplifier to test multi-megawatt renewable assets available at the National Wind Technology Center (NWTC). This paper addresses issues related to themore » development of a PHIL interface that allows testing hardware devices at actual scale. In particular, the novel PHIL interface algorithm and high-speed digital interface, which minimize the critical loop delay, are discussed.« less

Multi-Megawatt-Scale Power-Hardware-in-the-Loop Interface for Testing Ancillary Grid Services by Converter-Coupled Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koralewicz, Przemyslaw J; Gevorgian, Vahan; Wallen, Robert B

Power-hardware-in-the-loop (PHIL) is a simulation tool that can support electrical systems engineers in the development and experimental validation of novel, advanced control schemes that ensure the robustness and resiliency of electrical grids that have high penetrations of low-inertia variable renewable resources. With PHIL, the impact of the device under test on a generation or distribution system can be analyzed using a real-time simulator (RTS). PHIL allows for the interconnection of the RTS with a 7 megavolt ampere (MVA) power amplifier to test multi-megawatt renewable assets available at the National Wind Technology Center (NWTC). This paper addresses issues related to themore » development of a PHIL interface that allows testing hardware devices at actual scale. In particular, the novel PHIL interface algorithm and high-speed digital interface, which minimize the critical loop delay, are discussed.« less

Wavefront sensorless adaptive optics versus sensor-based adaptive optics for in vivo fluorescence retinal imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wahl, Daniel J.; Zhang, Pengfei; Jian, Yifan; Bonora, Stefano; Sarunic, Marinko V.; Zawadzki, Robert J.

2017-02-01

Adaptive optics (AO) is essential for achieving diffraction limited resolution in large numerical aperture (NA) in-vivo retinal imaging in small animals. Cellular-resolution in-vivo imaging of fluorescently labeled cells is highly desirable for studying pathophysiology in animal models of retina diseases in pre-clinical vision research. Currently, wavefront sensor-based (WFS-based) AO is widely used for retinal imaging and has demonstrated great success. However, the performance can be limited by several factors including common path errors, wavefront reconstruction errors and an ill-defined reference plane on the retina. Wavefront sensorless (WFS-less) AO has the advantage of avoiding these issues at the cost of algorithmic execution time. We have investigated WFS-less AO on a fluorescence scanning laser ophthalmoscopy (fSLO) system that was originally designed for WFS-based AO. The WFS-based AO uses a Shack-Hartmann WFS and a continuous surface deformable mirror in a closed-loop control system to measure and correct for aberrations induced by the mouse eye. The WFS-less AO performs an open-loop modal optimization with an image quality metric. After WFS-less AO aberration correction, the WFS was used as a control of the closed-loop WFS-less AO operation. We can easily switch between WFS-based and WFS-less control of the deformable mirror multiple times within an imaging session for the same mouse. This allows for a direct comparison between these two types of AO correction for fSLO. Our results demonstrate volumetric AO-fSLO imaging of mouse retinal cells labeled with GFP. Most significantly, we have analyzed and compared the aberration correction results for WFS-based and WFS-less AO imaging.

Ecological consequences of body size decline in harvested fish species: positive feedback loops in trophic interactions amplify human impact.

PubMed

Audzijonyte, Asta; Kuparinen, Anna; Gorton, Rebecca; Fulton, Elizabeth A

2013-04-23

Humans are changing marine ecosystems worldwide, both directly through fishing and indirectly through climate change. One of the little explored outcomes of human-induced change involves the decreasing body sizes of fishes. We use a marine ecosystem model to explore how a slow (less than 0.1% per year) decrease in the length of five harvested species could affect species interactions, biomasses and yields. We find that even small decreases in fish sizes are amplified by positive feedback loops in the ecosystem and can lead to major changes in natural mortality. For some species, a total of 4 per cent decrease in length-at-age over 50 years resulted in 50 per cent increase in predation mortality. However, the magnitude and direction in predation mortality changes differed among species and one shrinking species even experienced reduced predation pressure. Nevertheless, 50 years of gradual decrease in body size resulted in 1-35% decrease in biomasses and catches of all shrinking species. Therefore, fisheries management practices that ignore contemporary life-history changes are likely to overestimate long-term yields and can lead to overfishing.

Plenoptic camera wavefront sensing with extended sources

NASA Astrophysics Data System (ADS)

Jiang, Pengzhi; Xu, Jieping; Liang, Yonghui; Mao, Hongjun

2016-09-01

The wavefront sensor is used in adaptive optics to detect the atmospheric distortion, which feeds back to the deformable mirror to compensate for this distortion. Different from the Shack-Hartmann sensor that has been widely used with point sources, the plenoptic camera wavefront sensor has been proposed as an alternative wavefront sensor adequate for extended objects in recent years. In this paper, the plenoptic camera wavefront sensing with extended sources is discussed systematically. Simulations are performed to investigate the wavefront measurement error and the closed-loop performance of the plenoptic sensor. The results show that there are an optimal lenslet size and an optimal number of pixels to make the best performance. The RMS of the resulting corrected wavefront in closed-loop adaptive optics system is less than 108 nm (0.2λ) when D/r0 ≤ 10 and the magnitude M ≤ 5. Our investigation indicates that the plenoptic sensor is efficient to operate on extended sources in the closed-loop adaptive optics system.

Robustness study of the pseudo open-loop controller for multiconjugate adaptive optics.

PubMed

Piatrou, Piotr; Gilles, Luc

2005-02-20

Robustness of the recently proposed "pseudo open-loop control" algorithm against various system errors has been investigated for the representative example of the Gemini-South 8-m telescope multiconjugate adaptive-optics system. The existing model to represent the adaptive-optics system with pseudo open-loop control has been modified to account for misalignments, noise and calibration errors in deformable mirrors, and wave-front sensors. Comparison with the conventional least-squares control model has been done. We show with the aid of both transfer-function pole-placement analysis and Monte Carlo simulations that POLC remains remarkably stable and robust against very large levels of system errors and outperforms in this respect least-squares control. Approximate stability margins as well as performance metrics such as Strehl ratios and rms wave-front residuals averaged over a 1-arc min field of view have been computed for different types and levels of system errors to quantify the expected performance degradation.

Dislocation loop formation in model FeCrAl alloys after neutron irradiation below 1 dpa

DOE PAGES

Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar; ...

2017-08-01

FeCrAl alloys with varying compositions and microstructures are under consideration for accident-tolerant fuel cladding, but limited details exist on dislocation loop formation and growth for this class of alloys under neutron irradiation. Four model FeCrAl alloys with chromium contents ranging from 10.01 to 17.51 wt % and alunimum contents of 4.78 to 2.93 wt % were neutron irradiated to doses of 0.3–0.8 displacements per atom (dpa) at temperatures of 335–355°C. On-zone STEM imaging revealed a mixed population of black dots and larger dislocation loops with either a/2< 111 > or a< 100 > Burgers vectors. Weak composition dependencies were observedmore » and varied depending on whether the defect size, number density, or ratio of defect types was of interest. Here, the results were found to mirror those of previous studies on FeCrAl and FeCr alloys irradiated under similar conditions, although distinct differences exist.« less

Dislocation loop formation in model FeCrAl alloys after neutron irradiation below 1 dpa

NASA Astrophysics Data System (ADS)

Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar; Yamamoto, Yukinori; Howard, Richard H.

2017-11-01

FeCrAl alloys with varying compositions and microstructures are under consideration for accident-tolerant fuel cladding, but limited details exist on dislocation loop formation and growth for this class of alloys under neutron irradiation. Four model FeCrAl alloys with chromium contents ranging from 10.01 to 17.51 wt % and aluminum contents of 4.78 to 2.93 wt % were neutron irradiated to doses of 0.3-0.8 displacements per atom (dpa) at temperatures of 335-355 °C. On-zone STEM imaging revealed a mixed population of black dots and larger dislocation loops with either a / 2 〈 111 〉 or a 〈 100 〉 Burgers vectors. Weak composition dependencies were observed and varied depending on whether the defect size, number density, or ratio of defect types was of interest. Results were found to mirror those of previous studies on FeCrAl and FeCr alloys irradiated under similar conditions, although distinct differences exist.

Waveguide couplers with new power splitting ratios made possible by cascading of short multimode interference sections

NASA Astrophysics Data System (ADS)

Feng, David J. Y.; Lay, T. S.; Chang, T. Y.

2007-02-01

We show that it is possible to obtain 2 x 2 waveguide couplers with new power splitting ratios for cross coupling of 7%, 64%, 80% and 93% by cascading two short MMI sections. These couplers have simple geometry and low loss. They offer valuable new possibilities for designing waveguide power taps, high-Q ring resonators, ladder-structure optical filters, and loop-mirror partial reflectors.

Fine pattern replication on 10 x 10-mm exposure area using ETS-1 laboratory tool in HIT

NASA Astrophysics Data System (ADS)

Hamamoto, K.; Watanabe, Takeo; Hada, Hideo; Komano, Hiroshi; Kishimura, Shinji; Okazaki, Shinji; Kinoshita, Hiroo

2002-07-01

Utilizing ETS-1 laboratory tool in Himeji Institute of Technology (HIT), as for the fine pattern replicated by using the Cr mask in static exposure, it is replicated in the exposure area of 10 mm by 2 mm in size that the line and space pattern width of 60 nm, the isolated line pattern width of 40 nm, and hole pattern width of 150 nm. According to the synchronous scanning of the mass and wafer with EUVL laboratory tool with reduction optical system which consisted of three-aspherical-mirror in the NewSUBARU facilities succeeded in the line of 60 nm and the space pattern formation in the exposure region of 10mm by 10mm. From the result of exposure characteristics for positive- tone resist for KrF and EB, KrF chemically amplified resist has better characteristics than EB chemically amplified resist.

Analytic treatment of the black-hole bomb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hod, Shahar; Hod, Oded; School of Chemistry, Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978

2010-03-15

A bosonic field impinging on a rotating black hole can be amplified as it scatters off the hole, a phenomenon known as superradiant scattering. If in addition the field has a nonzero rest mass {mu}, the mass term effectively works as a mirror, reflecting the scattered wave back towards the black hole. In this physical system, known as a black-hole bomb, the wave may bounce back and forth between the black hole and some turning point, amplifying itself each time. Consequently, the field grows exponentially over time and is unstable. In this paper we study analytically for the first timemore » the phenomenon of superradiant instability (the black-hole bomb mechanism) in the regime M{mu}=O(1) of greatest instability. We find a maximal instability growth rate of {tau}{sup -1}=1.7x10{sup -3}M{sup -1}. This instability is 4 orders of magnitude stronger than has been previously estimated.« less

Sequence analysis of the mitochondrial DNA control region of ciscoes (genus Coregonus): taxonomic implications for the Great Lakes species flock.

PubMed

Reed, K M; Dorschner, M O; Todd, T N; Phillips, R B

1998-09-01

Sequence variation in the control region (D-loop) of the mitochondrial DNA (mtDNA) was examined to assess the genetic distinctiveness of the shortjaw cisco (Coregonus zenithicus). Individuals from within the Great Lakes Basin as well as inland lakes outside the basin were sampled. DNA fragments containing the entire D-loop were amplified by PCR from specimens of C. zenithicus and the related species C. artedi, C. hoyi, C. kiyi, and C. clupeaformis. DNA sequence analysis revealed high similarity within and among species and shared polymorphism for length variants. Based on this analysis, the shortjaw cisco is not genetically distinct from other cisco species.

Diagnostics of electron-heated solar flare models. III - Effects of tapered loop geometry and preheating

NASA Technical Reports Server (NTRS)

Emslie, A. G.; Li, Peng; Mariska, John T.

1992-01-01

A series of hydrodynamic numerical simulations of nonthermal electron-heated solar flare atmospheres and their corresponding soft X-ray Ca XIX emission-line profiles, under the conditions of tapered flare loop geometry and/or a preheated atmosphere, is presented. The degree of tapering is parameterized by the magnetic mirror ratio, while the preheated atmosphere is parameterized by the initial upper chromospheric pressure. In a tapered flare loop, it is found that the upward motion of evaporated material is faster compared with the case where the flare loop is uniform. This is due to the diverging nozzle seen by the upflowing material. In the case where the flare atmosphere is preheated and the flare geometry is uniform, the response of the atmosphere to the electron collisional heating is slow. The upward velocity of the hydrodynamic gas is reduced due not only to the large coronal column depth, but also to the increased inertia of the overlying material. It is concluded that the only possible electron-heated scenario in which the predicted Ca XIX line profiles agree with the BCS observations is when the impulsive flare starts in a preheated dense corona.

Highly conserved D-loop-like nuclear mitochondrial sequences (Numts) in tiger (Panthera tigris).

PubMed

Zhang, Wenping; Zhang, Zhihe; Shen, Fujun; Hou, Rong; Lv, Xiaoping; Yue, Bisong

2006-08-01

Using oligonucleotide primers designed to match hypervariable segments I (HVS-1) of Panthera tigris mitochondrial DNA (mtDNA), we amplified two different PCR products (500 bp and 287 bp) in the tiger (Panthera tigris), but got only one PCR product (287 bp) in the leopard (Panthera pardus). Sequence analyses indicated that the sequence of 287 bp was a D-loop-like nuclear mitochondrial sequence (Numts), indicating a nuclear transfer that occurred approximately 4.8-17 million years ago in the tiger and 4.6-16 million years ago in the leopard. Although the mtDNA D-loop sequence has a rapid rate of evolution, the 287-bp Numts are highly conserved; they are nearly identical in tiger subspecies and only 1.742% different between tiger and leopard. Thus, such sequences represent molecular 'fossils' that can shed light on evolution of the mitochondrial genome and may be the most appropriate outgroup for phylogenetic analysis. This is also proved by comparing the phylogenetic trees reconstructed using the D-loop sequence of snow leopard and the 287-bp Numts as outgroup.

Optical telescope refocussing mechanism concept design on remote sensing satellite

NASA Astrophysics Data System (ADS)

Kuo, Jen-Chueh; Ling, Jer

2017-09-01

The optical telescope system in remote sensing satellite must be precisely aligned to obtain high quality images during its mission life. In practical, because the telescope mirrors could be misaligned due to launch loads, thermal distortion on supporting structures or hygroscopic distortion effect in some composite materials, the optical telescope system is often equipped with refocussing mechanism to re-align the optical elements while optical element positions are out of range during image acquisition. This paper is to introduce satellite Refocussing mechanism function model design development process and the engineering models. The design concept of the refocussing mechanism can be applied on either cassegrain type telescope or korsch type telescope, and the refocussing mechanism is located at the rear of the secondary mirror in this paper. The purpose to put the refocussing mechanism on the secondary mirror is due to its higher sensitivity on MTF degradation than other optical elements. There are two types of refocussing mechanism model to be introduced: linear type model and rotation type model. For the linear refocussing mechanism function model, the model is composed of ceramic piezoelectric linear step motor, optical rule as well as controller. The secondary mirror is designed to be precisely moved in telescope despace direction through refocussing mechanism. For the rotation refocussing mechanism function model, the model is assembled with two ceramic piezoelectric rotational motors around two orthogonal directions in order to adjust the secondary mirror attitude in tilt angle and yaw angle. From the validation test results, the linear type refocussing mechanism function model can be operated to adjust the secondary mirror position with minimum 500 nm resolution with close loop control. For the rotation type model, the attitude angle of the secondary mirror can be adjusted with the minimum 6 sec of arc resolution and 5°/sec of angle velocity.

Closed Loop, DM Diversity-based, Wavefront Correction Algorithm for High Contrast Imaging Systems

NASA Technical Reports Server (NTRS)

Give'on, Amir; Belikov, Ruslan; Shaklan, Stuart; Kasdin, Jeremy

2007-01-01

High contrast imaging from space relies on coronagraphs to limit diffraction and a wavefront control systems to compensate for imperfections in both the telescope optics and the coronagraph. The extreme contrast required (up to 10(exp -10) for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. This paper presents a general closed loop correction algorithm for high contrast imaging coronagraphs by minimizing the energy in a predefined region in the image where terrestrial planets could be found. The estimation part of the algorithm reconstructs the complex field in the image plane using phase diversity caused by the deformable mirror. This method has been shown to achieve faster and better correction than classical speckle nulling.

Color film spectral properties test experiment for target simulation

NASA Astrophysics Data System (ADS)

Liu, Xinyue; Ming, Xing; Fan, Da; Guo, Wenji

2017-04-01

In hardware-in-loop test of the aviation spectra camera, the liquid crystal light valve and digital micro-mirror device could not simulate the spectrum characteristics of the landmark. A test system frame was provided based on the color film for testing the spectra camera; and the spectrum characteristics of the color film was test in the paper. The result of the experiment shows that difference was existed between the landmark and the film spectrum curse. However, the spectrum curse peak should change according to the color, and the curse is similar with the standard color traps. So, if the quantity value of error between the landmark and the film was calibrated and the error could be compensated, the film could be utilized in the hardware-in-loop test for the aviation spectra camera.

Nonperturbative Dynamical Casimir Effect in Optomechanical Systems: Vacuum Casimir-Rabi Splittings

NASA Astrophysics Data System (ADS)

Macrı, Vincenzo; Ridolfo, Alessandro; Di Stefano, Omar; Kockum, Anton Frisk; Nori, Franco; Savasta, Salvatore

2018-01-01

We study the dynamical Casimir effect using a fully quantum-mechanical description of both the cavity field and the oscillating mirror. We do not linearize the dynamics, nor do we adopt any parametric or perturbative approximation. By numerically diagonalizing the full optomechanical Hamiltonian, we show that the resonant generation of photons from the vacuum is determined by a ladder of mirror-field vacuum Rabi splittings. We find that vacuum emission can originate from the free evolution of an initial pure mechanical excited state, in analogy with the spontaneous emission from excited atoms. By considering a coherent drive of the mirror, using a master-equation approach to take losses into account, we are able to study the dynamical Casimir effect for optomechanical coupling strengths ranging from weak to ultrastrong. We find that a resonant production of photons out of the vacuum can be observed even for mechanical frequencies lower than the cavity-mode frequency. Since high mechanical frequencies, which are hard to achieve experimentally, were thought to be imperative for realizing the dynamical Casimir effect, this result removes one of the major obstacles for the observation of this long-sought effect. We also find that the dynamical Casimir effect can create entanglement between the oscillating mirror and the radiation produced by its motion in the vacuum field, and that vacuum Casimir-Rabi oscillations can occur. Finally, we also show that all these findings apply not only to optomechanical systems, but also to parametric amplifiers operating in the fully quantum regime.

Particle-in-cell Simulations of Continuously Driven Mirror and Ion Cyclotron Instabilities in High Beta Astrophysical and Heliospheric Plasmas

NASA Astrophysics Data System (ADS)

Riquelme, Mario A.; Quataert, Eliot; Verscharen, Daniel

2015-02-01

We use particle-in-cell simulations to study the nonlinear evolution of ion velocity space instabilities in an idealized problem in which a background velocity shear continuously amplifies the magnetic field. We simulate the astrophysically relevant regime where the shear timescale is long compared to the ion cyclotron period, and the plasma beta is β ~ 1-100. The background field amplification in our calculation is meant to mimic processes such as turbulent fluctuations or MHD-scale instabilities. The field amplification continuously drives a pressure anisotropy with p > p ∥ and the plasma becomes unstable to the mirror and ion cyclotron instabilities. In all cases, the nonlinear state is dominated by the mirror instability, not the ion cyclotron instability, and the plasma pressure anisotropy saturates near the threshold for the linear mirror instability. The magnetic field fluctuations initially undergo exponential growth but saturate in a secular phase in which the fluctuations grow on the same timescale as the background magnetic field (with δB ~ 0.3 langBrang in the secular phase). At early times, the ion magnetic moment is well-conserved but once the fluctuation amplitudes exceed δB ~ 0.1 langBrang, the magnetic moment is no longer conserved but instead changes on a timescale comparable to that of the mean magnetic field. We discuss the implications of our results for low-collisionality astrophysical plasmas, including the near-Earth solar wind and low-luminosity accretion disks around black holes.

Erbium:ytterbium fiber-laser system delivering watt-level femtosecond pulses using divided pulse amplification

NASA Astrophysics Data System (ADS)

Herda, Robert; Zach, Armin

2015-03-01

We present an Erbium:Ytterbium codoped fiber-amplifer system based on Divided-Pulses-Amplification (DPA) for ultrashort pulses. The output from a saturable-absorber mode-locked polarization-maintaining (PM) fiber oscillator is amplified in a PM normal-dispersion Erbium-doped fiber. After this stage the pulses are positively chirped and have a duration of 2.0 ps at an average power of 93 mW. A stack of 5 birefringent Yttrium-Vanadate crystals divides these pulses 32 times. We amplify these pulses using a double-clad Erbium:Ytterbium codoped fiber pumped through a multimode fiber combiner. The pulses double pass the amplifier and recombine in the crystals using non-reciprocal polarization 90° rotation by a Faraday rotating mirror. Pulses with a duration of 144 fs are obtained after separation from the input beam using a polarizing beam splitter cube. These pulses have an average power of 1.85 W at a repetition rate of 80 MHz. The generation of femtosecond pulses directly from the amplifier was enabled by a positively chirped seed pulse, normally dispersive Yttrium-Vanadate crystals, and anomalously dispersive amplifier fibers. Efficient frequency doubling to 780 nm with an average power of 725 mW and a pulse duration of 156 fs is demonstrated. In summary we show a DPA setup that enables the generation of femtosecond pulses at watt-level at 1560 nm without the need for further external dechirping and demonstrate a good pulse quality by efficient frequency doubling. Due to the use of PM fiber components and a Faraday rotator the setup is environmentally stable.

Analog phase lock between two lasers at LISA power levels

NASA Astrophysics Data System (ADS)

Diekmann, Christian; Steier, Frank; Sheard, Benjamin; Heinzel, Gerhard; Danzmann, Karsten

2009-03-01

This paper presents the implementation of an analog optical phase-locked-loop with an offset frequency of about 20MHz between two lasers, where the detected light powers were of the order of 31 pW and 200 μW. The goal of this setup was the design and characterization of a photodiode transimpedance amplifier for application in LISA. By application of a transimpedance amplifier designed to have low noise and low power consumption, the phase noise between the two lasers was a factor of two above the shot noise limit down to 60mHz. The achievable phase sensitivity depends ultimately on the available power of the highly attenuated master laser and on the input current noise of the transimpedance amplifier of the photodetector. The limiting noise source below 60mHz was the analog phase measurement system that was used in this experiment. A digital phase measurement system that is currently under development at the AEI will be used in the near future. Its application should improve the sensitivity.

Wide bandwidth transimpedance amplifier for extremely high sensitivity continuous measurements.

PubMed

Ferrari, Giorgio; Sampietro, Marco

2007-09-01

This article presents a wide bandwidth transimpedance amplifier based on the series of an integrator and a differentiator stage, having an additional feedback loop to discharge the standing current from the device under test (DUT) to ensure an unlimited measuring time opportunity when compared to switched discharge configurations while maintaining a large signal amplification over the full bandwidth. The amplifier shows a flat response from 0.6 Hz to 1.4 MHz, the capability to operate with leakage currents from the DUT as high as tens of nanoamperes, and rail-to-rail dynamic range for sinusoidal current signals independent of the DUT leakage current. Also available is a monitor output of the stationary current to track experimental slow drifts. The circuit is ideal for noise spectral and impedance measurements of nanodevices and biomolecules when in the presence of a physiological medium and in all cases where high sensitivity current measurements are requested such as in scanning probe microscopy systems.

Spectrally tunable, temporally shaped parametric front end to seed high-energy Nd:glass laser systems

DOE PAGES

Dorrer, C.; Consentino, A.; Cuffney, R.; ...

2017-10-18

Here, we describe a parametric-amplification–based front end for seeding high-energy Nd:glass laser systems. The front end delivers up to 200 mJ by parametric amplification in 2.5-ns flat-in-time pulses tunable over more than 15 nm. Spectral tunability over a range larger than what is typically achieved by laser media at similar energy levels is implemented to investigate cross-beam energy transfer in multibeam target experiments. The front-end operation is simulated to explain the amplified signal’s sensitivity to the input pump and signal. A large variety of amplified waveforms are generated by closed-loop pulse shaping. Various properties and limitations of this front endmore » are discussed.« less

Spectrally tunable, temporally shaped parametric front end to seed high-energy Nd:glass laser systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorrer, C.; Consentino, A.; Cuffney, R.

Here, we describe a parametric-amplification–based front end for seeding high-energy Nd:glass laser systems. The front end delivers up to 200 mJ by parametric amplification in 2.5-ns flat-in-time pulses tunable over more than 15 nm. Spectral tunability over a range larger than what is typically achieved by laser media at similar energy levels is implemented to investigate cross-beam energy transfer in multibeam target experiments. The front-end operation is simulated to explain the amplified signal’s sensitivity to the input pump and signal. A large variety of amplified waveforms are generated by closed-loop pulse shaping. Various properties and limitations of this front endmore » are discussed.« less

Low power, highly linear output buffer. [for infrared focal plane arrays

NASA Technical Reports Server (NTRS)

Foley, D.; Butler, N.; Stobie, J.

1992-01-01

A class AB CMOS output buffer has been designed for use on an IR focal plane array. Given the requirements for power dissipation and load capacitance a class A output, such as a source follower, would be unsuitable. The approach taken uses a class AB amplifier configured as a charge integrator. Thus it converts a charge packet in the focal plane multiplexer to a voltage which is then the output of the focal plane. With a quiescent current of 18 micro-a and a load capacitance of 100 pf, the amplifier has an open loop unity gain bandwidth of 900 khz. Integral nonlinearity is better than .03 percent over 5.5 volts when run with VDD-VSS = 6v.

180 mJ, long-pulse-duration, master-oscillator power amplifier with linewidth less than 25.6 kHz for laser guide stars.

PubMed

Wang, Chunhua; Zhang, Xiang; Ye, Zhibin; Liu, Chong; Chen, Jun

2013-07-01

A high-energy single-frequency hundred-microsecond long-pulse solid-state laser is demonstrated, which features an electro-optically modulated seed laser and two-stage double-passed pulse-pumped solid-state laser rod amplifier. Laser output with energy of 180 mJ, repetition rate of 50 Hz, and pulse width of 150 μs is achieved. The laser linewidth is measured to be less than 25.52 kHz by a fiber delay self-heterodyne method. In addition, a closed-loop controlling system is adopted to lock the center wavelength. No relaxation oscillation spikes appear in the pulse temporal profile, which is beneficial for further amplification.

Optical injection locking-based amplification in phase-coherent transfer of optical frequencies.

PubMed

Kim, Joonyoung; Schnatz, Harald; Wu, David S; Marra, Giuseppe; Richardson, David J; Slavík, Radan

2015-09-15

We demonstrate the use of an optical injection phase locked loop (OIPLL) as a regenerative amplifier for optical frequency transfer applications. The optical injection locking provides high gain within a narrow bandwidth (<100  MHz) and is capable of preserving the fractional frequency stability of the incoming carrier to better than 10(-18) at 1000 s. The OIPLL was tested in the field as a mid-span amplifier for the transfer of an ultrastable optical carrier, stabilized to an optical frequency standard, over a 292 km long installed dark fiber link. The transferred frequency at the remote end reached a fractional frequency instability of less than 1×10(-19) at averaging time of 3200 s.

A high power, pulsed, microwave amplifier for a synthetique aperture radar electrical model. Phase 1: Design

NASA Astrophysics Data System (ADS)

Atkinson, J. E.; Barker, G. G.; Feltham, S. J.; Gabrielson, S.; Lane, P. C.; Matthews, V. J.; Perring, D.; Randall, J. P.; Saunders, J. W.; Tuck, R. A.

1982-05-01

An electrical model klystron amplifier was designed. Its features include a gridded gun, a single stage depressed collector, a rare earth permanent magnet focusing system, an input loop, six rugged tuners and a coaxial line output section incorporating a coaxial-to-waveguide transducer and a pillbox window. At each stage of the design, the thermal and mechanical aspects were investigated and optimized within the framework of the RF specification. Extensive use was made of data from the preliminary design study and from RF measurements on the breadboard model. In an additional study, a comprehensive draft tube specification has been produced. Great emphasis has been laid on a second additional study on space-qualified materials and processes.

Analysis and Design of a Digital Controller for a Seismically Stable Platform.

DTIC Science & Technology

1981-12-01

disturbances are critical in gyroscope and accelerometer sensor evaluations. Distur- bances may be either measured, modeled and compensated in test profiles...controller design issues separately. Basically, the control law considerations are investigated assuming the SSP sensors provide perfect state...signal noise effects into sensor measurements through voltages induced in cabling directly or indirectly through ground loops in instrument amplifiers or

Shell-Type Micromechanical Oscillator

DTIC Science & Technology

2003-04-01

interferometric setup. A positive feedback loop was implemented by amplifying the red laser signal (related to the oscillator deflection) and using...resonator was actuated by a sharply focused, modulated Ar+ ion (blue) laser beam and detected by a red HeNe laser using an interferometric setup. A positive...top. Fig. 1 shows optical micrograph obtained by DIC (Differential Interference Contrast, known also as Nomarsky contrast). An array of three domes

CMOS Optoelectronic Lock-In Amplifier With Integrated Phototransistor Array.

PubMed

An Hu; Chodavarapu, Vamsy P

2010-10-01

We describe the design and development of an optoelectronic lock-in amplifier (LIA) for optical sensing and spectroscopy applications. The prototype amplifier is fabricated using Taiwan Semiconductor Manufacturing Co. complementary metal-oxide semiconductor 0.35-μm technology and uses a phototransistor array (total active area is 400 μm × 640μm) to convert the incident optical signals into electrical currents. The photocurrents are then converted into voltage signals using a transimpedance amplifier for subsequent convenient signal processing by the LIA circuitry. The LIA is optimized to be operational at 20-kHz modulation frequency but is operational in the frequency range from 13 kHz to 25 kHz. The system is tested with a light-emitting diode (LED) as the light source. The noise and signal distortions are suppressed with filters and a phase-locked loop (PLL) implemented in the LIA. The output dc voltage of the LIA is proportional to the incident optical power. The minimum measured dynamic reserve and sensitivity are 1.31 dB and 34 mV/μW, respectively. The output versus input relationship has shown good linearity. The LIA consumes an average power of 12.79 mW with a 3.3-V dc power supply.

NASA Tech Briefs, January 2009

NASA Technical Reports Server (NTRS)

2009-01-01

Tech Briefs are short announcements of innovations originating from research and development activities of the National Aeronautics and Space Administration. They emphasize information considered likely to be transferable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. Topics covered include: The Radio Frequency Health Node Wireless Sensor System; Effects of Temperature on Polymer/Carbon Chemical Sensors; Small CO2 Sensors Operate at Lower Temperature; Tele-Supervised Adaptive Ocean Sensor Fleet; Synthesis of Submillimeter Radiation for Spectroscopy; 100-GHz Phase Switch/Mixer Containing a Slot-Line Transition; Generating Ka-Band Signals Using an X-Band Vector Modulator; SiC Optically Modulated Field-Effect Transistor; Submillimeter-Wave Amplifier Module with Integrated Waveguide Transitions; Metrology System for a Large, Somewhat Flexible Telescope; Economical Implementation of a Filter Engine in an FPGA; Improved Joining of Metal Components to Composite Structures; Machined Titanium Heat-Pipe Wick Structure; Gadolinia-Doped Ceria Cathodes for Electrolysis of CO2; Utilizing Ocean Thermal Energy in a Submarine Robot; Fuel-Cell Power Systems Incorporating Mg-Based H2 Generators; Alternative OTEC Scheme for a Submarine Robot; Sensitive, Rapid Detection of Bacterial Spores; Adenosine Monophosphate-Based Detection of Bacterial Spores; Silicon Microleaks for Inlets of Mass Spectrometers; CGH Figure Testing of Aspherical Mirrors in Cold Vacuums; Series-Coupled Pairs of Silica Microresonators; Precise Stabilization of the Optical Frequency of WGMRs; Formation Flying of Components of a Large Space Telescope; Laser Metrology Heterodyne Phase-Locked Loop; Spatial Modulation Improves Performance in CTIS; High-Performance Algorithm for Solving the Diagnosis Problem; Truncation Depth Rule-of-Thumb for Convolutional Codes; Efficient Method for Optimizing Placement of Sensors.

Wind Evaluation Breadboard electronics and software

NASA Astrophysics Data System (ADS)

Núñez, Miguel; Reyes, Marcos; Viera, Teodora; Zuluaga, Pablo

2008-07-01

WEB, the Wind Evaluation Breadboard, is an Extremely Large Telescope Primary Mirror simulator, developed with the aim of quantifying the ability of a segmented primary mirror to cope with wind disturbances. This instrument supported by the European Community (Framework Programme 6, ELT Design Study), is developed by ESO, IAC, MEDIA-ALTRAN, JUPASA and FOGALE. The WEB is a bench of about 20 tons and 7 meter diameter emulating a segmented primary mirror and its cell, with 7 hexagonal segments simulators, including electromechanical support systems. In this paper we present the WEB central control electronics and the software development which has to interface with: position actuators, auxiliary slave actuators, edge sensors, azimuth ring, elevation actuator, meteorological station and air balloons enclosure. The set of subsystems to control is a reduced version of a real telescope segmented primary mirror control system with high real time performance but emphasizing on development time efficiency and flexibility, because WEB is a test bench. The paper includes a detailed description of hardware and software, paying special attention to real time performance. The Hardware is composed of three computers and the Software architecture has been divided in three intercommunicated applications and they have been implemented using Labview over Windows XP and Pharlap ETS real time operating system. The edge sensors and position actuators close loop has a sampling and commanding frequency of 1KHz.

The deformable secondary mirror of VLT: final electro-mechanical and optical acceptance test results

NASA Astrophysics Data System (ADS)

Briguglio, Runa; Biasi, Roberto; Xompero, Marco; Riccardi, Armando; Andrighettoni, Mario; Pescoller, Dietrich; Angerer, Gerald; Gallieni, Daniele; Vernet, Elise; Kolb, Johann; Arsenault, Robin; Madec, Pierre-Yves

2014-07-01

The Deformable Secondary Mirror (DSM) for the VLT ended the stand-alone electro-mechanical and optical acceptance process, entering the test phase as part of the Adaptive Optics Facility (AOF) at the ESO Headquarter (Garching). The VLT-DSM currently represents the most advanced already-built large-format deformable mirror with its 1170 voice-coil actuators and its internal metrology based on co-located capacitive sensors to control the shape of the 1.12m-diameter 2mm-thick convex shell. The present paper reports the final results of the electro-mechanical and optical characterization of the DSM executed in a collaborative effort by the DSM manufacturing companies (Microgate s.r.l. and A.D.S. International s.r.l.), INAF-Osservatorio Astrofisico di Arcetri and ESO. The electro-mechanical acceptance tests have been performed in the company premises and their main purpose was the dynamical characterization of the internal control loop response and the calibration of the system data that are needed for its optimization. The optical acceptance tests have been performed at ESO (Garching) using the ASSIST optical test facility. The main purpose of the tests are the characterization of the optical shell flattening residuals, the corresponding calibration of flattening commands, the optical calibration of the capacitive sensors and the optical calibration of the mirror influence functions.

A fully automated digitally controlled 30-inch telescope

NASA Technical Reports Server (NTRS)

Colgate, S. A.; Moore, E. P.; Carlson, R.

1975-01-01

A fully automated 30-inch (75-cm) telescope has been successfully designed and constructed from a military surplus Nike-Ajax radar mount. Novel features include: closed-loop operation between mountain telescope and campus computer 30 km apart via microwave link, a TV-type sensor which is photon shot-noise limited, a special lightweight primary mirror, and a stepping motor drive capable of slewing and settling one degree in one second or a radian in fifteen seconds.

Organization of the Integrated Photonics Topical Meeting Held in Victoria, British Columbia on 30 March-1 April 1998. Technical Digest Series. Volume 4. Postconference Edition

DTIC Science & Technology

1999-03-22

amplifiers fabricated on Si substrates by co- sputtering, (p. 27) 11:30am IMC3 ■ Birefrlngent oxidized porous silicon-based optical waveguides, Yu. N...that integrated optical waveguides based on oxidized porous silicon have a relatively large birefringence. As a result, the modes of both... Membrane microresonator lasers with 2-D photonic bandgap crystal mirrors for compact in- plane optics, B. D’Urso, O. Painter, A. Yariv, A. Scherer

A mirror for science.

PubMed

Jasanoff, Sheila

2014-01-01

Early conceptions of the public understanding of science suffered from a narrow framing of what science means and a presumption that science is divided from its publics by walls of ignorance and indifference. Those assumptions amplified misunderstanding and led to faulty policies. It is time to reopen each element in the term "public understanding of science" to renewed reflection. This journal can advance that goal by encouraging research on actual rather than imagined public responses to science, on representations of science in the public sphere, and on interactions between science, technology and society.

Ponderomotive Acceleration in Coronal Loops

NASA Astrophysics Data System (ADS)

Dahlburg, Russell B.; Laming, J. Martin; Taylor, Brian; Obenschain, Keith

2017-08-01

Ponderomotive acceleration has been asserted to be a cause of the First Ionization Potential (FIP) effect, the by now well known enhancement in abundance by a factor of 3-4 over photospheric values of elements in the solar corona with FIP less than about 10 eV. It is shown here by means of numerical simulations that ponderomotive acceleration occurs in solar coronal loops, with the appropriate magnitude and direction, as a ``byproduct'' of coronal heating. The numerical simulations are performed with the HYPERION code, which solves the fully compressible three-dimensional magnetohydrodynamic equations including nonlinear thermal conduction and optically thin radiation. Numerical simulations of a coronal loops with an axial magnetic field from 0.005 Teslas to 0.02 Teslas and lengths from 25000 km to 75000 km are presented. In the simulations the footpoints of the axial loop magnetic field are convected by random, large-scale motions. There is a continuous formation and dissipation of field-aligned current sheets which act to heat the loop. As a consequence of coronal magnetic reconnection, small scale, high speed jets form. The familiar vortex quadrupoles form at reconnection sites. Between the magnetic footpoints and the corona the reconnection flow merges with the boundary flow. It is in this region that the ponderomotive acceleration occurs. Mirroring the character of the coronal reconnection, the ponderomotive acceleration is also found to be intermittent.

Wireless Power Transfer for Space Applications

NASA Technical Reports Server (NTRS)

Ramos, Gabriel Vazquez; Yuan, Jiann-Shiun

2011-01-01

This paper introduces an implementation for magnetic resonance wireless power transfer for space applications. The analysis includes an equivalent impedance study, loop material characterization, source/load resonance coupling technique, and system response behavior due to loads variability. System characterization is accomplished by executing circuit design from analytical equations and simulations using Matlab and SPICE. The theory was validated by a combination of different experiments that includes loop material consideration, resonance coupling circuits considerations, electric loads considerations and a small scale proof-of-concept prototype. Experiment results shows successful wireless power transfer for all the cases studied. The prototype provided about 4.5 W of power to the load at a separation of -5 cm from the source using a power amplifier rated for 7 W.

Sequence analysis of the mitochondrial DNA control region of ciscoes (genus Coregonus): Taxonomic implications for the Great Lakes species flock

USGS Publications Warehouse

Reed, Kent M.; Dorschner, Michael O.; Todd, Thomas N.; Phillips, Ruth B.

1998-01-01

Sequence variation in the control region (D-loop) of the mitochondrial DNA (mtDNA) was examined to assess the genetic distinctiveness of the shortjaw cisco (Coregonus zenithicus). Individuals from within the Great Lakes Basin as well as inland lakes outside the basin were sampled. DNA fragments containing the entire D-loop were amplified by PCR from specimens ofC. zenithicus and the related species C. artedi, C. hoyi, C. kiyi, and C. clupeaformis. DNA sequence analysis revealed high similarity within and among species and shared polymorphism for length variants. Based on this analysis, the shortjaw cisco is not genetically distinct from other cisco species.

Mirror symmetry breaking of silicon polymers--from weak bosons to artificial helix.

PubMed

Fujiki, Michiya

2009-01-01

From elemental particles to human beings, matter and living worlds in our universe are dissymmetric with respect to mirror symmetry. Since the early 19th century, the origin of biomolecular handedness has been puzzling scientists. Nature's elegant bottom-up preference, however, sheds light on new concepts of generating, amplifying, and switching artificial polymers, supramolecules, liquid crystals, and organic crystals that can exhibit ambidextrous circular dichroism in the UV/Visible region with efficiency in production under milder ambient conditions. In the 1920s, Kipping, who first synthesized polysilanes with phenyl groups, had much interest in the handedness of inorganic and organic substances from 1898 to 1909 in his early research life. Polysilanes--which are soluble Si-Si bonded chain-like near-UV chromophores that carry a rich variety of organic groups--may become a bridge between animate and inanimate polymer systems. The present account focuses on several mirror symmetry breaking phenomena exemplified in polysilanes carrying chiral and/or achiral side groups, which are in isotropic dilute solution, as polymer particles dispersed in solution, and in a double layer film immobilized at the solid surface, and subtle differences in the helix, by dictating ultimately ultraweak chiral forces at subatomic, atomic, and molecular levels. Copyright 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Proton and Ion Acceleration on the Contrast Upgraded Texas Petawatt Laser

NASA Astrophysics Data System (ADS)

McCary, Edward; Roycroft, Rebecca; Jiao, Xuejing; Kupfer, Rotem; Tiwari, Ganesh; Wagner, Craig; Yandow, Andrew; Franke, Philip; Dyer, Gilliss; Gaul, Erhard; Toncian, Toma; Ditmire, Todd; Hegelich, Bjorn; CenterHigh Energy Density Science Team

2016-10-01

Recent upgrades to the Texas Petawatt (TPW) laser system have eliminated pre-pulses and reduced the laser pedestal, resulting in improved laser contrast. Previously unwanted pre-pulses and amplified spontaneous emission (ASE) would ionize targets thinner than 1 micron, leaving an under-dense plasma which was not capable of accelerating ions to high energies. After the upgrade the contrast was drastically improved allowing us to successfully shoot targets as thin as 20 nm without plasma mirrors. We have also observed evidence of relativistic transparency and Break-Out Afterburner (BOA) ion acceleration when shooting ultra-thin, nanometer scale targets. Data taken with a wide angle ion spectrometer (IWASP) showed the characteristic asymmetry of BOA in the plane orthogonal to the laser polarization on thin targets but not on micron scale targets. Thick micron scale targets saw improvement as well; shots on 2 μm thick gold targets saw ions with energies up to 100 MeV, which broke the former record proton energy on the TPW. Switching the focusing optic from an f/3 parabolic mirror to an f/40 spherical mirror showed improvement in the number of low energy protons created, and provided a source for hundreds of picosecond heating of aluminum foils for warm dense matter measurements.

Focusing X-ray free-electron laser pulses using Kirkpatrick-Baez mirrors at the NCI hutch of the PAL-XFEL.

PubMed

Kim, Jangwoo; Kim, Hyo Yun; Park, Jaehyun; Kim, Sangsoo; Kim, Sunam; Rah, Seungyu; Lim, Jun; Nam, Ki Hyun

2018-01-01

The Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL) is a recently commissioned X-ray free-electron laser (XFEL) facility that provides intense ultrashort X-ray pulses based on the self-amplified spontaneous emission process. The nano-crystallography and coherent imaging (NCI) hutch with forward-scattering geometry is located at the hard X-ray beamline of the PAL-XFEL and provides opportunities to perform serial femtosecond crystallography and coherent X-ray diffraction imaging. To produce intense high-density XFEL pulses at the interaction positions between the X-rays and various samples, a microfocusing Kirkpatrick-Baez (KB) mirror system that includes an ultra-precision manipulator has been developed. In this paper, the design of a KB mirror system that focuses the hard XFEL beam onto a fixed sample point of the NCI hutch, which is positioned along the hard XFEL beamline, is described. The focusing system produces a two-dimensional focusing beam at approximately 2 µm scale across the 2-11 keV photon energy range. XFEL pulses of 9.7 keV energy were successfully focused onto an area of size 1.94 µm × 2.08 µm FWHM.

100J-level nanosecond pulsed Yb:YAG cryo-cooled DPSSL amplifier

NASA Astrophysics Data System (ADS)

Smith, J. M.; Butcher, T. J.; Mason, P. D.; Ertel, K.; Phillips, P. J.; Banerjee, S.; De Vido, M.; Chekhlov, O.; Divoky, M.; Pilar, J.; Shaikh, W.; Hooker, C.; Lucianetti, A.; Hernandez Gomez, C.; Mocek, T.; Edwards, C.; Collier, J. L.

2018-02-01

We report on the successful demonstration of the world's first kW average power, 100 Joule-class, high-energy, nanosecond pulsed diode-pumped solid-state laser (DPSSL), DiPOLE100. Results from the first long-term test for amplification will be presented; the system was operated for 1 hour with 10 ns duration pulses at 10 Hz pulse repetition rate and an average output energy of 105 J and RMS energy stability of approximately 1%. The laser system is based on scalable cryogenic gas-cooled multi-slab ceramic Yb:YAG amplifier technology. The DiPOLE100 system comprises three major sub-systems, a spatially and temporally shaped front end, a 10 J cryo-amplifier and a 100 J cryo-amplifier. The 10 J cryo-amplifier contain four Yb:YAG ceramic gain media slabs, which are diode pumped from both sides, while a multi-pass architecture configured for seven passes enables 10 J of energy to be extracted at 10 Hz. This seeds the 100 J cryo-amplifier, which contains six Yb:YAG ceramic gain media slabs with the multi-pass configured for four passes. Our future development plans for this architecture will be introduced including closed-loop pulse shaping, increased energy, higher repetition rates and picosecond operation. This laser architecture unlocks the potential for practical applications including new sources for industrial materials processing and high intensity laser matter studies as envisioned for ELI [1], HiLASE [2], and the European XFEL [3]. Alternatively, it can be used as a pump source for higher repetition rate PW-class amplifiers, which can themselves generate high-brightness secondary radiation and ion sources leading to new remote imaging and medical applications.

Design and end-to-end modelling of a deployable telescope

NASA Astrophysics Data System (ADS)

Dolkens, Dennis; Kuiper, Hans

2017-09-01

Deployable optics have the potential of revolutionizing the field of high resolution Earth Observation. By offering the same resolutions as a conventional telescope, while using a much smaller launch volume and mass, the costs of high resolution image data can be brought down drastically. In addition, the technology will ultimately enable resolutions that are currently unattainable due to limitations imposed by the size of launcher fairings. To explore the possibilities and system complexities of a deployable telescope, a concept study was done to design a competitive deployable imager. A deployable telescope was designed for a ground sampling distance of 25 cm from an orbital altitude of 550 km. It offers an angular field of view of 0.6° and has a panchromatic channel as well as four multispectral bands in the visible and near infrared spectrum. The optical design of the telescope is based on an off-axis Korsch Three Mirror Anastigmat. A freeform tertiary mirror is used to ensure a diffraction limited image quality for all channels, while maintaining a compact design. The segmented primary mirror consists of four tapered aperture segments, which can be folded down during launch, while the secondary mirror is mounted on a deployable boom. In its stowed configuration, the telescope fits within a quarter of the volume of a conventional telescope reaching the same resolution. To reach a diffraction limited performance while operating in orbit, the relative position of each individual mirror segment must be controlled to a fraction of a wavelength. Reaching such tolerances with deployable telescope challenging, due to inherent uncertainties in the deployment mechanisms. Adding to the complexity is the fact that the telescope will be operating in a Low Earth Orbit (LEO) where it will be exposed to very dynamic thermal conditions. Therefore, the telescope will be equipped with a robust calibration system. Actuators underneath the primary mirror will be controlled using a closed-loop system based on measurements of the image sharpness as well as measurements obtained with edge sensors placed between the mirror segments. In addition, a phase diversity system will be used to recover residual wavefront aberrations. To aid the design of the deployable telescope, an end-to-end performance model was developed. The model is built around a dedicated ray-trace program written in Matlab. This program was built from the ground up for the purpose of modelling segmented telescope systems and allows for surface data computed with Finite Element Models (FEM) to be imported in the model. The program also contains modules which can simulate the closed-loop calibration of the telescope and it can use simulated images as an input for phase diversity and image processing algorithms. For a given thermo-mechanical state, the end-to-end model can predict the image quality that will be obtained after the calibration has been completed and the image has been processed. As such, the model is a powerful systems engineering tool, which can be used to optimize the in-orbit performance of a segmented, deployable telescope.

Model-based estimation and control for off-axis parabolic mirror alignment

NASA Astrophysics Data System (ADS)

Fang, Joyce; Savransky, Dmitry

2018-02-01

This paper propose an model-based estimation and control method for an off-axis parabolic mirror (OAP) alignment. Current studies in automated optical alignment systems typically require additional wavefront sensors. We propose a self-aligning method using only focal plane images captured by the existing camera. Image processing methods and Karhunen-Loève (K-L) decomposition are used to extract measurements for the observer in closed-loop control system. Our system has linear dynamic in state transition, and a nonlinear mapping from the state to the measurement. An iterative extended Kalman filter (IEKF) is shown to accurately predict the unknown states, and nonlinear observability is discussed. Linear-quadratic regulator (LQR) is applied to correct the misalignments. The method is validated experimentally on the optical bench with a commercial OAP. We conduct 100 tests in the experiment to demonstrate the consistency in between runs.

Closed loop adaptive optics for microscopy without a wavefront sensor.

PubMed

Kner, Peter; Winoto, Lukman; Agard, David A; Sedat, John W

2010-02-24

A three-dimensional wide-field image of a small fluorescent bead contains more than enough information to accurately calculate the wavefront in the microscope objective back pupil plane using the phase retrieval technique. The phase-retrieved wavefront can then be used to set a deformable mirror to correct the point-spread function (PSF) of the microscope without the use of a wavefront sensor. This technique will be useful for aligning the deformable mirror in a widefield microscope with adaptive optics and could potentially be used to correct aberrations in samples where small fluorescent beads or other point sources are used as reference beacons. Another advantage is the high resolution of the retrieved wavefont as compared with current Shack-Hartmann wavefront sensors. Here we demonstrate effective correction of the PSF in 3 iterations. Starting from a severely aberrated system, we achieve a Strehl ratio of 0.78 and a greater than 10-fold increase in maximum intensity.

Adaptive optics vision simulation and perceptual learning system based on a 35-element bimorph deformable mirror.

PubMed

Dai, Yun; Zhao, Lina; Xiao, Fei; Zhao, Haoxin; Bao, Hua; Zhou, Hong; Zhou, Yifeng; Zhang, Yudong

2015-02-10

An adaptive optics visual simulation combined with a perceptual learning (PL) system based on a 35-element bimorph deformable mirror (DM) was established. The larger stroke and smaller size of the bimorph DM made the system have larger aberration correction or superposition ability and be more compact. By simply modifying the control matrix or the reference matrix, select correction or superposition of aberrations was realized in real time similar to a conventional adaptive optics closed-loop correction. PL function was first integrated in addition to conventional adaptive optics visual simulation. PL training undertaken with high-order aberrations correction obviously improved the visual function of adult anisometropic amblyopia. The preliminary application of high-order aberrations correction with PL training on amblyopia treatment was being validated with a large scale population, which might have great potential in amblyopia treatment and visual performance maintenance.

Research on the compensation of laser launch optics to improve the performance of the LGS spot.

PubMed

Liu, Jie; Wang, Jianli; Wang, Yuning; Tian, Donghe; Zheng, Quan; Lin, Xudong; Wang, Liang; Yang, Qingyun

2018-02-01

To improve the beam quality of the uplink laser, a 37 channel piezo-ceramic deformable mirror was inserted into the laser launch optics to compensate the static aberrations. An interferometer was used as the calibration light source as well as the wavefront sensor to perform closed-loop correction for the moment. About 0.38λ root mean square (rms) aberrations, including the deformable mirror's initial figure error, were compensated, and the residual error was less than 0.07λ rms. Field observations with a 2 m optical telescope demonstrated that the peak intensity value of the laser guide star (LGS) spot increased from 5650 to 7658, and the full width at half-maximum (FWHM) size reduced from 4.07 arcseconds to 3.52 arcseconds. With the compensation, an improved guide star spot can be obtained, which is crucial for the adaptive optics systems of ground-based large telescopes.

Metal-in-metal localized surface plasmon resonance

NASA Astrophysics Data System (ADS)

Smith, G. B.; Earp, A. A.

2010-01-01

Anomalous strong resonances in silver and gold nanoporous thin films which conduct are found to arise from isolated metal nano-islands separated from the surrounding percolating metal network by a thin loop of insulator. This observed resonant optical response is modelled. The observed peak position is in agreement with the observed average dimensions of the silver core and insulator shell. As the insulating ring thickness shrinks, the resonance moves to longer wavelengths and strengthens. This structure is the Babinet's principle counterpart of dielectric core-metal shell nanoparticles embedded in dielectric. Like for the latter, tuning of resonant absorption is possible, but here the matrix reflects rather than transmits, and tuning to longer wavelengths is more practical. A new class of metal mirror occurring as a single thin layer is identified using the same resonances in dense metal mirrors. Narrow band deep localized dips in reflectance result.

HYDRAULIC SERVO

DOEpatents

Wiegand, D.E.

1962-05-01

A hydraulic servo is designed in which a small pressure difference produced at two orifices by an electrically operated flapper arm in a constantly flowing hydraulic loop is hydraulically amplified by two constant flow pumps, two additional orifices, and three unconnected ball pistons. Two of the pistons are of one size and operate against the additional orifices, and the third piston is of a different size and operates between and against the first two pistons. (AEC)

Development of hardwares and computer interface for a two-degree-of-freedom robot

NASA Technical Reports Server (NTRS)

Nguyen, Charles C.; Pooran, Farhad J.

1987-01-01

The research results that were obtained are reviewed. Then the robot actuator, the selection of the data acquisition system, and the design of the power amplifier will be discussed. The machine design of the robot manipulator will then be presented. After that, the integration of the developed hardware into the open-loop system will also be discussed. Current and future research work is addressed.

Loop-mediated isothermal amplification (LAMP): a versatile technique for detection of micro-organisms.

PubMed

Wong, Y-P; Othman, S; Lau, Y-L; Radu, S; Chee, H-Y

2018-03-01

Loop-mediated isothermal amplification (LAMP) amplifies DNA with high specificity, efficiency and rapidity under isothermal conditions by using a DNA polymerase with high displacement strand activity and a set of specifically designed primers to amplify targeted DNA strands. Following its first discovery by Notomi et al. ( Nucleic Acids Res 28: E63), LAMP was further developed over the years which involved the combination of this technique with other molecular approaches, such as reverse transcription and multiplex amplification for the detection of infectious diseases caused by micro-organisms in humans, livestock and plants. In this review, available types of LAMP techniques will be discussed together with their applications in detection of various micro-organisms. Up to date, there are varieties of LAMP detection methods available including colorimetric and fluorescent detection, real-time monitoring using turbidity metre and detection using lateral flow device which will also be highlighted in this review. Apart from that, commercialization of LAMP technique had also been reported such as lyophilized form of LAMP reagents kit and LAMP primer sets for detection of pathogenic micro-organisms. On top of that, advantages and limitations of this molecular detection method are also described together with its future potential as a diagnostic method for infectious disease. © 2017 The Society for Applied Microbiology.

Endpoint visual detection of three genetically modified rice events by loop-mediated isothermal amplification.

PubMed

Chen, Xiaoyun; Wang, Xiaofu; Jin, Nuo; Zhou, Yu; Huang, Sainan; Miao, Qingmei; Zhu, Qing; Xu, Junfeng

2012-11-07

Genetically modified (GM) rice KMD1, TT51-1, and KF6 are three of the most well known transgenic Bt rice lines in China. A rapid and sensitive molecular assay for risk assessment of GM rice is needed. Polymerase chain reaction (PCR), currently the most common method for detecting genetically modified organisms, requires temperature cycling and relatively complex procedures. Here we developed a visual and rapid loop-mediated isothermal amplification (LAMP) method to amplify three GM rice event-specific junction sequences. Target DNA was amplified and visualized by two indicators (SYBR green or hydroxy naphthol blue [HNB]) within 60 min at an isothermal temperature of 63 °C. Different kinds of plants were selected to ensure the specificity of detection and the results of the non-target samples were negative, indicating that the primer sets for the three GM rice varieties had good levels of specificity. The sensitivity of LAMP, with detection limits at low concentration levels (0.01%−0.005% GM), was 10- to 100-fold greater than that of conventional PCR. Additionally, the LAMP assay coupled with an indicator (SYBR green or HNB) facilitated analysis. These findings revealed that the rapid detection method was suitable as a simple field-based test to determine the status of GM crops.

Ultrafast optomechanical pulse picking

NASA Astrophysics Data System (ADS)

Lilienfein, Nikolai; Holzberger, Simon; Pupeza, Ioachim

2017-01-01

State-of-the-art optical switches for coupling pulses into and/or out of resonators are based on either the electro-optic or the acousto-optic effect in transmissive elements. In high-power applications, the damage threshold and other nonlinear and thermal effects in these elements impede further improvements in pulse energy, duration, and average power. We propose a new optomechanical switching concept which is based solely on reflective elements and is suitable for switching times down to the ten-nanosecond range. To this end, an isolated section of a beam path is moved in a system comprising mirrors rotating at a high angular velocity and stationary imaging mirrors, without affecting the propagation of the beam thereafter. We discuss three variants of the concept and exemplify practical parameters for its application in regenerative amplifiers and stack-and-dump enhancement cavities. We find that optomechanical pulse picking has the potential to achieve switching rates of up to a few tens of kilohertz while supporting pulse energies of up to several joules.

FY2005 Progress Summary and FY2006 Program Plan Statement of Work and Deliverables for Development of High Average Power Diode-Pumped Solid State Lasers, and Complementary Technologies, for Applications in Energy and Defense

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebbers, C

The primary focus this year was to operate the system with two amplifiers populated with and pumped by eight high power diode arrays. The system was operated for extended run periods which enabled average power testing of components, diagnostics, and controls. These tests were highly successful, with a demonstrated energy level of over 55 joules for 4 cumulative hours at a repetition rate of 10 Hz (average power 0.55 kW). In addition, high average power second harmonic generation was demonstrated, achieving 227 W of 523.5 nm light (22.7 J, 10 Hz, 15 ns, 30 minutes) Plans to achieve higher energymore » levels and average powers are in progress. The dual amplifier system utilizes a 4-pass optical arrangement. The Yb:S-FAP slabs were mounted in aerodynamic aluminum vane structures to allow turbulent helium gas flow across the faces. Diagnostic packages that monitored beam performance were deployed during operation. The laser experiments involved injecting a seed beam from the front end into the system and making four passes through both amplifiers. Beam performance diagnostics monitored the beam on each pass to assess system parameters such as gain and nearfield intensity profiles. This year, an active mirror and wavefront sensor were procured and demonstrated in an off-line facility. The active mirror technology can correct for low order phase distortions at user specified operating conditions (such as repetition rates different than 10 Hz) and is a complementary technology to the static phase plates used in the system for higher order distortions. A picture of the laser system with amplifier No.2 (foreground) and amplifier No.1 (background) is shown in Fig. 1.0.1.1. The control system and diagnostics were recently enhanced for faster processing and allow remote operation of the system. The growth and fabrication of the Yb:S-FAP slabs constituted another major element of our program objectives. Our goal was to produce at least fourteen 4x6 cm2 crystalline slabs. These goals were met. Nine crystal boules were successfully grown to produce 14 slabs. In addition, we have prepared the way to scale the Yb:S-FAP crystals to the next growth diameter (10-inch diameter as opposed to 7-inch diameter). An outside contract was placed with Northrop-Grumman to scaleup the Yb:S-FAP crystal size. The following sections discuss the above accomplishments in more technical detail and are followed by plans and a budget request for FY2006.« less

Adaptive optics for the ESO-VLT

NASA Astrophysics Data System (ADS)

Merkle, Fritz

1989-04-01

This paper discusses adaptive optics, its performance, and its requirements for applications in astronomy to overcome limitations due to atmospheric turbulence. Guidelines for the implementation of these devices in telescopes are given, in particular for the Very Large Telescope (VLT) at ESO. It is intended to equip each one of the four 8-m telescopes of the VLT, which are arranged in a linear array with an independent adaptive optical system. These systems will serve the individual and the combined coude foci. A small-scale prototype adaptive system is under development. It is equipped with a 19-piezoelectric-actuator deformable mirror, a Shack-Hartmann-type wavefront sensor, and a dedicated wavefront computer for closing the feedback loop. This system is based on a polychromatic approach; i.e., it senses the wavefront in the visible, but the adaptive correction loop works at 3-5 microns.

Design of optical axis jitter control system for multi beam lasers based on FPGA

NASA Astrophysics Data System (ADS)

Ou, Long; Li, Guohui; Xie, Chuanlin; Zhou, Zhiqiang

2018-02-01

A design of optical axis closed-loop control system for multi beam lasers coherent combining based on FPGA was introduced. The system uses piezoelectric ceramics Fast Steering Mirrors (FSM) as actuator, the Fairfield spot detection of multi beam lasers by the high speed CMOS camera for optical detecting, a control system based on FPGA for real-time optical axis jitter suppression. The algorithm for optical axis centroid detecting and PID of anti-Integral saturation were realized by FPGA. Optimize the structure of logic circuit by reuse resource and pipeline, as a result of reducing logic resource but reduced the delay time, and the closed-loop bandwidth increases to 100Hz. The jitter of laser less than 40Hz was reduced 40dB. The cost of the system is low but it works stably.

Complete analog control of the carrier-envelope-phase of a high-power laser amplifier.

PubMed

Feng, C; Hergott, J-F; Paul, P-M; Chen, X; Tcherbakoff, O; Comte, M; Gobert, O; Reduzzi, M; Calegari, F; Manzoni, C; Nisoli, M; Sansone, G

2013-10-21

In this work we demonstrate the development of a complete analog feedback loop for the control of the carrier-envelope phase (CEP) of a high-average power (20 W) laser operating at 10 kHz repetition rate. The proposed method combines a detection scheme working on a single-shot basis at the full-repetition-rate of the laser system with a fast actuator based either on an acousto-optic or on an electro-optic crystal. The feedback loop is used to correct the CEP fluctuations introduced by the amplification process demonstrating a CEP residual noise of 320 mrad measured on a single-shot basis. The comparison with a feedback loop operating at a lower sampling rate indicates an improvement up to 45% in the residual noise. The measurement of the CEP drift for different integration times clearly evidences the importance of the single-shot characterization of the residual CEP drift. The demonstrated scheme could be efficiently applied for systems approaching the 100 kHz repetition rate regime.

Advanced ECCD based NTM control in closed-loop operation at ASDEX Upgrade (AUG)

NASA Astrophysics Data System (ADS)

Reich, Matthias; Barrera-Orte, Laura; Behler, Karl; Bock, Alexander; Giannone, Louis; Maraschek, Marc; Poli, Emanuele; Rapson, Chris; Stober, Jörg; Treutterer, Wolfgang

2012-10-01

In high performance plasmas, Neoclassical Tearing Modes (NTMs) are regularly observed at reactor-grade beta-values. They limit the achievable normalized beta, which is undesirable because fusion performance scales as beta squared. The method of choice for controlling and avoiding NTMs at AUG is the deposition of ECCD inside the magnetic island for stabilization in real-time (rt). Our approach to tackling such complex control problems using real-time diagnostics allows rigorous optimization of all subsystems. Recent progress in rt-equilibrium reconstruction (< 3.5 ms), rt-localization of NTMs (< 8 ms) and rt beam tracing (< 25 ms) allows closed-loop feedback operation using multiple movable mirrors as the ECCD deposition actuator. The rt-equilibrium uses function parametrization or a fast Grad-Shafranov solver with an option to include rt-MSE measurements. The island localization is based on a correlation of ECE and filtered Mirnov signals. The rt beam-tracing module provides deposition locations and their derivative versus actuator position of multiple gyrotrons. The ``MHD controller'' finally drives the actuators. Results utilizing closed-loop operation with multiple gyrotrons and their effect on NTMs are shown.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sokollik, Thomas; Shiraishi, Satomi; Osterhoff, Jens

We present experimental results on a tape-drive based plasma mirror which could be used for a compact coupling of a laser beam into a staged laser driven electron accelerator. This novel kind of plasma mirror is suitable for high repetition rates and for high number of laser shots. In order to design a compact, staged laser plasma based accelerator or collider [1], the coupling of the laser beam into the different stages represents one of the key issues. To limit the spatial foot print and thus to realize a high overall acceleration gradient, a concept has to be found whichmore » realizes this in-coupling within a few centimeters (cf. Fig 1). The fluence of the laser pulse several centimeters away from the acceleration stage (focus) exceeds the damage threshold of any available mirror coating. Therefore, in reference [2] a plasma mirror was suggested for this purpose. We present experiments on a tape-drive based plasma mirror which could be used to reflect the focused laser beam into the acceleration stage. Plasma mirrors composed of antireflection coated glass substrates are usually used to improve the temporal laser contrast of laser pulses by several orders of magnitudes [3,4]. This is particularly important for laser interaction with solid matter, such as ion acceleration [5,6] and high harmonic generation on surfaces [7]. Therefore, the laser pulse is weekly focused onto a substrate. The main pulse generates a plasma and is reflected at the critical surface, whereas the low intensity pre-pulse (mainly the Amplified Spontaneous Emission pedestal) will be transmitted through the substrate before the mirror has been triggered. Several publications [3,4] demonstrate a conservation of the spatial beam quality and a reflectivity of about 70 %. The drawback of this technique is the limited repetition rate since for every shot a fresh surface has to be provided. In the past years several novel approaches for high repetition rate plasma mirrors have been developed [2, 8]. Nevertheless, for the staged accelerator scheme a second important requirement has to be considered. Since the electron beam has to propagate through the mirror, the thickness of the substrate has to be as thin as possible to reduce the distortion of the electron beam. A tape of only several micrometer thickness can overcome these disadvantages. It can be used with a sufficient repetition rate while it allows the electron beam to propagate through with a minimum of scattering.« less

Low speed phaselock speed control system. [for brushless dc motor

NASA Technical Reports Server (NTRS)

Fulcher, R. W.; Sudey, J. (Inventor)

1975-01-01

A motor speed control system for an electronically commutated brushless dc motor is provided which includes a phaselock loop with bidirectional torque control for locking the frequency output of a high density encoder, responsive to actual speed conditions, to a reference frequency signal, corresponding to the desired speed. The system includes a phase comparator, which produces an output in accordance with the difference in phase between the reference and encoder frequency signals, and an integrator-digital-to-analog converter unit, which converts the comparator output into an analog error signal voltage. Compensation circuitry, including a biasing means, is provided to convert the analog error signal voltage to a bidirectional error signal voltage which is utilized by an absolute value amplifier, rotational decoder, power amplifier-commutators, and an arrangement of commutation circuitry.

Adaptive Optics for Industry and Medicine

NASA Astrophysics Data System (ADS)

Dainty, Christopher

2008-01-01

pt. 1. Wavefront correctors and control. Liquid crystal lenses for correction of presbyopia (Invited Paper) / Guoqiang Li and Nasser Peyghambarian. Converging and diverging liquid crystal lenses (oral paper) / Andrew X. Kirby, Philip J. W. Hands, and Gordon D. Love. Liquid lens technology for miniature imaging systems: status of the technology, performance of existing products and future trends (invited paper) / Bruno Berge. Carbon fiber reinforced polymer deformable mirrors for high energy laser applications (oral paper) / S. R. Restaino ... [et al.]. Tiny multilayer deformable mirrors (oral paper) / Tatiana Cherezova ... [et al.]. Performance analysis of piezoelectric deformable mirrors (oral paper) / Oleg Soloviev, Mikhail Loktev and Gleb Vdovin. Deformable membrane mirror with high actuator density and distributed control (oral paper) / Roger Hamelinck ... [et al.]. Characterization and closed-loop demonstration of a novel electrostatic membrane mirror using COTS membranes (oral paper) / David Dayton ... [et al.]. Electrostatic micro-deformable mirror based on polymer materials (oral paper) / Frederic Zamkotsian ... [et al.]. Recent progress in CMOS integrated MEMS A0 mirror development (oral paper) / A. Gehner ... [et al.]. Compact large-stroke piston-tip-tilt actuator and mirror (oral paper) / W. Noell ... [et al.]. MEMS deformable mirrors for high performance AO applications (oral paper) / Paul Bierden, Thomas Bifano and Steven Cornelissen. A versatile interferometric test-rig for the investigation and evaluation of ophthalmic AO systems (poster paper) / Steve Gruppetta, Jiang Jian Zhong and Luis Diaz-Santana. Woofer-tweeter adaptive optics (poster paper) / Thomas Farrell and Chris Dainty. Deformable mirrors based on transversal piezoeffect (poster paper) / Gleb Vdovin, Mikhail Loktev and Oleg Soloviev. Low-cost spatial light modulators for ophthalmic applications (poster paper) / Vincente Durán ... [et al.]. Latest MEMS DM developments and the path ahead at Iris AO (poster paper) / Michael A. Helmbrecht ... [et al.]. Electrostatic push pull mirror improvernents in visual optics (poster paper) / S. Bonora and L. Poletto. 25cm bimorph mirror for petawatt laser / S. Bonora ... [et al.]. Hysteresis compensation for piezo deformable mirror (poster paper) / H. Song ... [et al.]. Static and dynamic responses of an adaptive optics ferrofluidic mirror (poster paper) / A. Seaman ... [et al.]. New HDTV (1920 x 1080) phase-only SLM (poster paper) / Stefan Osten and Sven Krueger. Monomorph large aperture deformable mirror for laser applications (poster paper) / J-C Sinquin, J-M Lurcon, C. Guillemard. Low cost, high speed for adaptive optics control (oral paper) / Christopher D. Saunter and Gordon D. Love. Open loop woofer-tweeter adaptive control on the LAO multi-conjugate adaptive optics testbed (oral paper) / Edward Laag, Don Gavel and Mark Ammons -- pt. 2. Wavefront sensors. Wave front sensorless adaptive optics for imaging and microscopy (invited paper) / Martin J. Booth, Delphine Débarre and Tony Wilson. A fundamental limit for wavefront sensing (oral paper) / Carl Paterson. Coherent fibre-bundle wavefront sensor (oral paper) / Brian Vohnsen, I. Iglesias and Pablo Artal. Maximum-likelihood methods in wave-front sensing: nuisance parameters (oral paper) / David Lara, Harrison H. Barrett, and Chris Dainty. Real-time wavefront sensing for ultrafast high-power laser beams (oral paper) / Juan M. Bueno ... [et al.]. Wavefront sensing using a random phase screen (oral paper) / M. Loktev, G. Vdovin and O. Soloviev. Quadri-Wave Lateral Shearing Interferometry: a new mature technique for wave front sensing in adaptive optics (oral paper) / Benoit Wattellier ... [et al.]. In vivo measurement of ocular aberrations with a distorted grating wavefront sensor (oral paper) / P. Harrison ... [et al.]. Position-sensitive detector designed with unusual CMOS layout strategies for a Hartman-Shack wavefront sensor (oral Paper) / Davies W. de Lima Monteiro ... [et al.]. Adaptive optics system to compensate complex-shaped wavefronts (oral paper) / Miguel Ares, and Santiago Royo. A kind of novel linear phase retrieval wavefront sensor and its application in close-loop adaptive optics system (oral paper) / Xinyang Li ... [et al.]. Ophthalmic Shack-Hatmann wavefront sensor applications (oral paper) / Daniel R. Neal. Wave front sensing of an optical vortex and its correction with the help of bimorph mirror (poster paper) / F. A. Starikov ... [et al.]. Recent advances in laser metrology and correction of high numerical aperture laser beams using quadri-wave lateral shearing-interferometry (poster paper) / Benoit Wattellier, Ivan Doudet and William Boucher. Thin film optical metrology using principles of wavefront sensing and interference (poster paper) / D. M. Faichnie, A. H. Greenaway and I. Bain. Direct diffractive image simulation (poster paper) / A. P. Maryasov, N. P. Maryasov, A. P. Layko. High speed smart CMOS sensor for adaptive optics (poster paper) / T. D. Raymond ... [et al.]. Traceable astigmatism measurements for wavefront sensors (poster paper) / S. R. G. Hall, S. D. Knox, R. F. Stevens -- pt. 3. Adaptive optics in vision science. Dual-conjugate adaptive optics instrument for wide-field retinal imaging (oral paper) / Jörgen Thaung, Mette-Owner Petersen and Zoran Popovic. Visual simulation using electromagnetic adaptive-optics (oral paper) / Laurent Vabre ... [et al.]. High-resolution field-of-view widening in human eye retina imaging (oral paper) / Alexander V. Dubinin, Tatyana Yu. Cherezova, Alexis V. Kudryashov. Psychophysical experiments on visual performance with an ocular adaptive optics system (oral paper) / E. Dalimier, J. C. Dainty and J. Barbur. Does the accommodative mechanism of the eye calibrate itself using aberration dynamics? (oral paper) / K. M. Hampson, S. S. Chin and E. A. H. Mallen. A study of field aberrations in the human eye (oral paper) / Alexander V. Goncharov ... [et al.]. Dual wavefront corrector ophthalmic adaptive optics: design and alignment (oral paper) / Alfredo Dubra and David Williams. High speed simultaneous SLO/OCT imaging of the human retina with adaptive optics (oral paper) / M. Pircher ... [et al.]. Characterization of an AO-OCT system (oral paper) / Julia W. Evans ... [et al.]. Adaptive optics optical coherence tomography for retina imaging (oral paper) / Guohua Shi ... [et al.]. Development, calibration and performance of an electromagnetic-mirror-based adaptive optics system for visual optics (oral paper) / Enrique Gambra ... [et al.]. Adaptive eye model (poster paper) / Sergey O. Galetskzy and Alexty V. Kudryashov. Adaptive optics system for retinal imaging based on a pyramid wavefront sensor (poster paper) / Sabine Chiesa ... [et al.]. Modeling of non-stationary dynamic ocular aberrations (poster paper) / Conor Leahy and Chris Dainty. High-order aberrations and accommodation of human eye (poster paper) / Lixia Xue ... [et al.]. Electromagnetic deformable mirror: experimental assessment and first ophthalmic applications (poster paper) / L. Vabre ... [et al.]. Correcting ocular aberrations in optical coherence tomography (poster paper) / Simon Tuohy ... [et al.] -- pt. 4. Adaptive optics in optical storage and microscopy. The application of liquid crystal aberration compensator for the optical disc systems (invited paper) / Masakazu Ogasawara. Commercialization of the adaptive scanning optical microscope (ASOM) (oral paper) / Benjamin Potsaid ... [et al.]. A practical implementation of adaptive optics for aberration compensation in optical microscopy (oral paper) / A. J. Wright ... [et al.]. Active focus locking in an optically sectioning microscope using adaptive optics (poster paper) / S. Poland, A. J. Wright, J. M. Girkin. Towards four dimensional particle tracking for biological applications / Heather I. Campbell ... [et al.]. Adaptive optics for microscopy (poster paper) / Xavier Levecq -- pt. 5. Adaptive optics in lasers. Improved beam quality of a high power Yb: YAG laser (oral paper) / Dennis G. Harris ... [et al.]. Intracavity adaptive optics optimization of an end-pumped Nd:YVO4 laser (oral paper) / Petra Welp, Ulrich Wittrock. New results in high power lasers beam correction (oral paper) / Alexis Kudryashov ... [et al.]. Adaptive optical systems for the Shenguang-III prototype facility (oral paper) / Zeping Yang ... [et al.]. Adaptive optics control of solid-state lasers (poster paper) / Walter Lubeigt ... [et al.]. Gerchberg-Saxton algorithm for multimode beam reshaping (poster paper) / Inna V. Ilyina, Tatyana Yu. Cherezova. New algorithm of combining for spatial coherent beams (poster paper) / Ruofu Yang ... [et al.]. Intracavity mode control of a solid-state laser using a 19-element deformable mirror (poster paper) / Ping Yang ... [et al.] -- pt. 6. Adaptive optics in communication and atmospheric compensation. Fourier image sharpness sensor for laser communications (oral paper) / Kristin N. Walker and Robert K. Tyson. Fast closed-loop adaptive optics system for imaging through strong turbulence layers (oral paper) / Ivo Buske and Wolfgang Riede. Correction of wavefront aberrations and optical communication using aperture synthesis (oral paper) / R. J. Eastwood ... [et al.]. Adaptive optics system for a small telescope (oral paper) / G. Vdovin, M. Loktev and O. Soloviev. Fast correction of atmospheric turbulence using a membrane deformable mirror (poster paper) / Ivan Capraro, Stefano Bonora, Paolo Villoresi. Atmospheric turbulence measurements over a 3km horizontal path with a Shack-Hartmann wavefront sensor (poster paper) / Ruth Mackey, K. Murphy and Chris Dainty. Field-oriented wavefront sensor for laser guide stars (poster paper) / Lidija Bolbasova, Alexander Goncharov and Vladimir Lukin.

Voltage linear transformation circuit design

NASA Astrophysics Data System (ADS)

Sanchez, Lucas R. W.; Jin, Moon-Seob; Scott, R. Phillip; Luder, Ryan J.; Hart, Michael

2017-09-01

Many engineering projects require automated control of analog voltages over a specified range. We have developed a computer interface comprising custom hardware and MATLAB code to provide real-time control of a Thorlabs adaptive optics (AO) kit. The hardware interface includes an op amp cascade to linearly shift and scale a voltage range. With easy modifications, any linear transformation can be accommodated. In AO applications, the design is suitable to drive a range of different types of deformable and fast steering mirrors (FSM's). Our original motivation and application was to control an Optics in Motion (OIM) FSM which requires the customer to devise a unique interface to supply voltages to the mirror controller to set the mirror's angular deflection. The FSM is in an optical servo loop with a wave front sensor (WFS), which controls the dynamic behavior of the mirror's deflection. The code acquires wavefront data from the WFS and fits a plane, which is subsequently converted into its corresponding angular deflection. The FSM provides +/-3° optical angular deflection for a +/-10 V voltage swing. Voltages are applied to the mirror via a National Instruments digital-to-analog converter (DAC) followed by an op amp cascade circuit. This system has been integrated into our Thorlabs AO testbed which currently runs at 11 Hz, but with planned software upgrades, the system update rate is expected to improve to 500 Hz. To show that the FSM subsystem is ready for this speed, we conducted two different PID tuning runs at different step commands. Once 500 Hz is achieved, we plan to make the code and method for our interface solution freely available to the community.

Applications of tuned mass dampers to improve performance of large space mirrors

NASA Astrophysics Data System (ADS)

Yingling, Adam J.; Agrawal, Brij N.

2014-01-01

In order for future imaging spacecraft to meet higher resolution imaging capability, it will be necessary to build large space telescopes with primary mirror diameters that range from 10 m to 20 m and do so with nanometer surface accuracy. Due to launch vehicle mass and volume constraints, these mirrors have to be deployable and lightweight, such as segmented mirrors using active optics to correct mirror surfaces with closed loop control. As a part of this work, system identification tests revealed that dynamic disturbances inherent in a laboratory environment are significant enough to degrade the optical performance of the telescope. Research was performed at the Naval Postgraduate School to identify the vibration modes most affecting the optical performance and evaluate different techniques to increase damping of those modes. Based on this work, tuned mass dampers (TMDs) were selected because of their simplicity in implementation and effectiveness in targeting specific modes. The selected damping mechanism was an eddy current damper where the damping and frequency of the damper could be easily changed. System identification of segments was performed to derive TMD specifications. Several configurations of the damper were evaluated, including the number and placement of TMDs, damping constant, and targeted structural modes. The final configuration consisted of two dampers located at the edge of each segment and resulted in 80% reduction in vibrations. The WFE for the system without dampers was 1.5 waves, with one TMD the WFE was 0.9 waves, and with two TMDs the WFE was 0.25 waves. This paper provides details of some of the work done in this area and includes theoretical predictions for optimum damping which were experimentally verified on a large aperture segmented system.

Design, development, and validation of a segment support actuator for the prototype segmented mirror telescope

NASA Astrophysics Data System (ADS)

Deshmukh, Prasanna Gajanan; Mandal, Amaresh; Parihar, Padmakar S.; Nayak, Dayananda; Mishra, Deepta Sundar

2018-01-01

Segmented mirror telescopes (SMT) are built using several small hexagonal mirrors positioned and aligned by the three actuators and six edge sensors per segment to maintain the shape of the primary mirror. The actuators are responsible for maintaining and tracking the mirror segments to the desired position, in the presence of external disturbances introduced by wind, vibration, gravity, and temperature. The present paper describes our effort to develop a soft actuator and the actuator controller for prototype SMT at Indian Institute of Astrophysics, Bangalore. The actuator designed, developed, and validated is a soft actuator based on the voice coil motor and flexural elements. It is designed for the range of travel of ±1.5 mm and the force range of 25 N along with an offloading mechanism to reduce the power consumption. A precision controller using a programmable system on chip (PSoC 5Lp) and a customized drive board has also been developed for this actuator. The close loop proportional-integral-derivative (PID) controller implemented in the PSoC gets position feedback from a high-resolution linear optical encoder. The optimum PID gains are derived using relay tuning method. In the laboratory, we have conducted several experiments to test the performance of the prototype soft actuator as well as the controller. We could achieve 5.73- and 10.15-nm RMS position errors in the steady state as well as tracking with a constant speed of 350 nm/s, respectively. We also present the outcome of various performance tests carried out when off-loader is in action as well as the actuator is subjected to dynamic wind loading.

A Hebbian learning rule gives rise to mirror neurons and links them to control theoretic inverse models.

PubMed

Hanuschkin, A; Ganguli, S; Hahnloser, R H R

2013-01-01

Mirror neurons are neurons whose responses to the observation of a motor act resemble responses measured during production of that act. Computationally, mirror neurons have been viewed as evidence for the existence of internal inverse models. Such models, rooted within control theory, map-desired sensory targets onto the motor commands required to generate those targets. To jointly explore both the formation of mirrored responses and their functional contribution to inverse models, we develop a correlation-based theory of interactions between a sensory and a motor area. We show that a simple eligibility-weighted Hebbian learning rule, operating within a sensorimotor loop during motor explorations and stabilized by heterosynaptic competition, naturally gives rise to mirror neurons as well as control theoretic inverse models encoded in the synaptic weights from sensory to motor neurons. Crucially, we find that the correlational structure or stereotypy of the neural code underlying motor explorations determines the nature of the learned inverse model: random motor codes lead to causal inverses that map sensory activity patterns to their motor causes; such inverses are maximally useful, by allowing the imitation of arbitrary sensory target sequences. By contrast, stereotyped motor codes lead to less useful predictive inverses that map sensory activity to future motor actions. Our theory generalizes previous work on inverse models by showing that such models can be learned in a simple Hebbian framework without the need for error signals or backpropagation, and it makes new conceptual connections between the causal nature of inverse models, the statistical structure of motor variability, and the time-lag between sensory and motor responses of mirror neurons. Applied to bird song learning, our theory can account for puzzling aspects of the song system, including necessity of sensorimotor gating and selectivity of auditory responses to bird's own song (BOS) stimuli.

A Hebbian learning rule gives rise to mirror neurons and links them to control theoretic inverse models

PubMed Central

Hanuschkin, A.; Ganguli, S.; Hahnloser, R. H. R.

2013-01-01

Mirror neurons are neurons whose responses to the observation of a motor act resemble responses measured during production of that act. Computationally, mirror neurons have been viewed as evidence for the existence of internal inverse models. Such models, rooted within control theory, map-desired sensory targets onto the motor commands required to generate those targets. To jointly explore both the formation of mirrored responses and their functional contribution to inverse models, we develop a correlation-based theory of interactions between a sensory and a motor area. We show that a simple eligibility-weighted Hebbian learning rule, operating within a sensorimotor loop during motor explorations and stabilized by heterosynaptic competition, naturally gives rise to mirror neurons as well as control theoretic inverse models encoded in the synaptic weights from sensory to motor neurons. Crucially, we find that the correlational structure or stereotypy of the neural code underlying motor explorations determines the nature of the learned inverse model: random motor codes lead to causal inverses that map sensory activity patterns to their motor causes; such inverses are maximally useful, by allowing the imitation of arbitrary sensory target sequences. By contrast, stereotyped motor codes lead to less useful predictive inverses that map sensory activity to future motor actions. Our theory generalizes previous work on inverse models by showing that such models can be learned in a simple Hebbian framework without the need for error signals or backpropagation, and it makes new conceptual connections between the causal nature of inverse models, the statistical structure of motor variability, and the time-lag between sensory and motor responses of mirror neurons. Applied to bird song learning, our theory can account for puzzling aspects of the song system, including necessity of sensorimotor gating and selectivity of auditory responses to bird's own song (BOS) stimuli. PMID:23801941

Ultrasensitive Electrometry with a Cavity-Embedded Cooper Pair Transistor

NASA Astrophysics Data System (ADS)

Rimberg, A. J.; Li, Juliang

In this experiment a cavity-embedded Cooper-pair transistor (cCPT) is used as a potentially quantum-limited electrometer. The cCPT consists of a Cooper pair transistor placed at the voltage antinode of a 5.7 GHz shorted quarter-wave resonator so that the CPT provides a galvanic connection between the cavity's central conductor and ground plane. The quantum inductance of the CPT, which appears in parallel with the effective inductance of the cavity resonance, can be modulated by application of either a gate voltage to the CPT island or a flux bias to the CPT/cavity loop. Changes in the CPT inductance shift the cavity resonant frequency, and therefore the phase of a microwave signal reflected from the cavity. The reflected wave is amplified by both SLUG and HEMT amplifiers before its phase is measured. The cCPT can also be operated as a Josephson parametric amplifier (JPA). A pump tone at 11.4 GHz sent into the flux bias line has been shown to provide about 10dB gain. The possibility of parametrically amplifying the side bands produced by a charge detection measurement, thereby increasing the overall sensitivity of the cCPT, will also be investigated. Supported by Grants ARO W911NF-13-10377 and NSF DMR 1507400.

Mutation detection by mismatch binding protein, MutS, in amplified DNA: Application to the cystic fibrosis gene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lishanski, A.; Ostrander, E.A.; Rine, J.

1994-03-29

An experimental strategy for detecting heterozygosity in genomic DNA has been developed based on preferential binding of Escherichia coli MutS protein to DNA molecules containing mismatched bases. The binding was detected by a gel mobility-shift assay. This approach was tested by using as a model the most commonly occurring mutations within the cystic fibrosis (CFTR) gene. Genomic DNA samples were amplified with 5{prime}-end-labeled primers that bracket the site of the {Delta}F508 3-bp deletion in exon 10 of the CFTR gene. The renatured PCR products from homozygotes produced homoduplexes; the PCR products from heterozygotes produced heteroduplexes and homoduplexes (1:1). MutS proteinmore » bound more strongly to heteroduplexes that correspond to heterozygous carriers of {Delta}F508 and contain a CTT or a GAA loop in one of the strands than to homoduplexes corresponding to homozygotes. The ability of MutS protein to detect heteroduplexes in PCR-amplified DNA extended to fragments {approximately} 500 bp long. The method was also able to detect carriers of the point mutations in exon 11 of the CFTR gene by a preferential binding of MutS to single-base mismatches in PCR-amplified DNA.« less

φ-OTDR sensing system with bidirectional pumped fiber Raman amplifier and unbalanced MZ interferometer

NASA Astrophysics Data System (ADS)

Zhang, Liang; Tian, Ming; Dong, Lei

2017-10-01

In order to improve the detection distance and the sensitivity, we propose a novel distributed optical fiber sensing system. This system is composed of bidirectional pumping fiber Raman amplifier and unbalanced fiber Mach-Zehnder interferometer. Based on the interference mechanism of phase sensitive optical time domain reflectometer (φ-OTDR), the system can get the sensing information of the whole optical fiber by analyzing the backward scattered light. The interferometer is used as the demodulator of the sensing system, which consists of a 3×3 coupler and two faraday rotator mirrors. By means of the demodulator, the signal light is divided into three beams with fixed phase difference. To deal with these three signals, we can get the vibration information directly on the optical fiber. Through experimental study, this system has a high sensitivity. The maximum sensing length and the spatial resolution of the φ-OTDR system are 100 km and 10 m. The signal to noise ratio about 18 dB is achieved.

2.36 J, 50 Hz nanosecond pulses from a diode side-pumped Nd:YAG MOPA system

NASA Astrophysics Data System (ADS)

Li, Chaoyang; Lu, Chengqiang; Li, Chuan; Yang, Ning; Li, Ye; Yang, Zhen; Han, Song; Shi, Junfeng; Zhou, Zewu

2017-07-01

We report on a high-energy high-repetition-rate nanosecond Nd:YAG main oscillator power amplifier (MOPA) system. Maximum output pulse energy of 2.36 J with duration of 9.4 ns at 50 Hz has been achieved. The master oscillator was a LD side-pumped electro-optical Q-switched Nd:YAG rod laser adopting unstable cavity with variable reflectivity mirror (VRM). It delivered a pulse train with energy up to 180 mJ and pulse duration of 10.7 ns. The near-field pattern demonstrated a nearly super Gaussian flat top profile. In the amplification stage, the pulse was boosted via double-pass two Nd:YAG rod amplifiers. Maximum pulse energy was obtained at the peak pump power of 37.5 kW, corresponding to an optical-optical conversion efficiency of 25.2%. The correlative peak power was deduced to be 251 MW. We also presented the result of 100 Hz nanosecond laser with average output power of >100 W.

Near-self-imaging cavity for three-mode optoacoustic parametric amplifiers using silicon microresonators.

PubMed

Liu, Jian; Torres, F A; Ma, Yubo; Zhao, C; Ju, L; Blair, D G; Chao, S; Roch-Jeune, I; Flaminio, R; Michel, C; Liu, K-Y

2014-02-10

Three-mode optoacoustic parametric amplifiers (OAPAs), in which a pair of photon modes are strongly coupled to an acoustic mode, provide a general platform for investigating self-cooling, parametric instability and very sensitive transducers. Their realization requires an optical cavity with tunable transverse modes and a high quality-factor mirror resonator. This paper presents the design of a table-top OAPA based on a near-self-imaging cavity design, using a silicon torsional microresonator. The design achieves a tuning coefficient for the optical mode spacing of 2.46  MHz/mm. This allows tuning of the mode spacing between amplification and self-cooling regimes of the OAPA device. Based on demonstrated resonator parameters (frequencies ∼400  kHz and quality-factors ∼7.5×10(5) we predict that the OAPA can achieve parametric instability with 1.6 μW of input power and mode cooling by a factor of 1.9×10(4) with 30 mW of input power.

Stokes injected Raman capillary waveguide amplifier

DOEpatents

Kurnit, Norman A.

1980-01-01

A device for producing stimulated Raman scattering of CO.sub.2 laser radiation by rotational states in a diatomic molecular gas utilizing a Stokes injection signal. The system utilizes a cryogenically cooled waveguide for extending focal interaction length. The waveguide, in conjunction with the Stokes injection signal, reduces required power density of the CO.sub.2 radiation below the breakdown threshold for the diatomic molecular gas. A Fresnel rhomb is employed to circularly polarize the Stokes injection signal and CO.sub.2 laser radiation in opposite circular directions. The device can be employed either as a regenerative oscillator utilizing optical cavity mirrors or as a single pass amplifier. Additionally, a plurality of Raman gain cells can be staged to increase output power magnitude. Also, in the regenerative oscillator embodiment, the Raman gain cell cavity length and CO.sub.2 cavity length can be matched to provide synchronism between mode locked CO.sub.2 pulses and pulses produced within the Raman gain cell.

Magnetostatic Surface Wave Microwave Oscillator.

DTIC Science & Technology

1981-12-18

feedback loop of a 2-4 Gigahertz (Gliz) amplifier (Ref. 13). Thin film yttrium-iron- garnet (YIG) was used as the propagation medium and the three...Theory, McGraw Hill Book Company, New York, 1964. 16. Tsai, T. and Sethares, J.C., "Band Stop Filter Using LPE -YIG Films ," Proceedings of the IEEE...and Stiglitz System Composed of YIG Film , Conducting Strips, Double Ground Plane and Dielectric Regions .......... . 11 4 Magnetic Field Strength versus

Radar System Characterization Extended to Hardware-in-the-Loop Simulation for the Lab-Volt (Trademark) Training System

DTIC Science & Technology

2007-09-01

devices such as klystrons , magnetrons, and traveling wave tubes. These microwave devices produce high power levels but may have limited bandwidths [20...diagram. The specific arrangement of components within a RADAR transmitter varies with operational specifications. Two options exist to produce high power ...cascading to generate sufficient power [20]. The second option to generate high power levels is to replace RF oscillators and amplifiers with microwave

Q-Band (37-41 GHz) Satellite Beacon Architecture for RF Propagation Experiments

NASA Technical Reports Server (NTRS)

Simmons, Rainee N.; Wintucky, Edwin G.

2012-01-01

In this paper, the design of a beacon transmitter that will be flown as a hosted payload on a geostationary satellite to enable propagation experiments at Q-band (37-41 GHz) frequencies is presented. The beacon uses a phased locked loop stabilized dielectric resonator oscillator and a solid-state power amplifier to achieve the desired output power. The satellite beacon antenna is configured as an offset-fed cut-paraboloidal reflector.

Q-Band (37 to 41 GHz) Satellite Beacon Architecture for RF Propagation Experiments

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Wintucky, Edwin G.

2014-01-01

In this paper, the design of a beacon transmitter that will be flown as a hosted payload on a geostationary satellite to enable propagation experiments at Q-band (37 to 41 GHz) frequencies is presented. The beacon uses a phased locked loop stabilized dielectric resonator oscillator and a solid-state power amplifier to achieve the desired output power. The satellite beacon antenna is configured as an offset-fed cutparaboloidal reflector.

AN OSCILLATOR CONFIGURATION FOR FULL REALIZATION OF HARD X-RAY FREE ELECTRON LASER*

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, K.-J.; Kolodziej, T.; Lindberg, R. R.

2017-06-01

An x-ray free electron laser oscillator (XFELO) is feasible by employing an X-ray cavity with Bragg mirrors such as diamond crystals. An XFELO at the 5th harmonic frequency may be implemented at the LCLS II using its 4 GeV superconducting linac, producing stable, fully coherent, high-spectral-purity hard x-rays. In addition, its output can be a coherent seed to the LCLS amplifier for stable, high-power, femto-second x-ray pulses. We summarize the recent progress in various R&D efforts addressing critical issues for realizing an XFELO at LCLS II.

Feedback stabilization system for pulsed single longitudinal mode tunable lasers

DOEpatents

Esherick, Peter; Raymond, Thomas D.

1991-10-01

A feedback stabilization system for pulse single longitudinal mode tunable lasers having an excited laser medium contained within an adjustable length cavity and producing a laser beam through the use of an internal dispersive element, including detection of angular deviation in the output laser beam resulting from detuning between the cavity mode frequency and the passband of the internal dispersive element, and generating an error signal based thereon. The error signal can be integrated and amplified and then applied as a correcting signal to a piezoelectric transducer mounted on a mirror of the laser cavity for controlling the cavity length.

Spectrally narrowed lasing of a self-injection KrF excimer laser

NASA Astrophysics Data System (ADS)

Shimada, Yasuhiro; Wani, Koichi; Miki, Tadaaki; Kawahara, Hidehito; Mimasu, Mutsumi; Ogata, Yoshiro

1990-08-01

Spectrally nantwed lasing of a KrF excimer laser has teen ahieved by a self-injection technique using abeam splitter for power extraction aixi intravity etalons for spectral-narrowing. The laser cavity is divithi into an amplifying branch aix! a spectralnarrowing branch. The spectral bandwidth was narrowed to <3pm FWHM with air-sed etalons placed in the spectral-narrowing branch. A laser propagation model was intrOdUced for describing the laser intensity traveling in the laser cavity. The calculated intensityincident onthe intracavityetalons wassmaller thanthat in theconventional Fabry-Perotcavity withplane-parallel mirrors.

Research and development of a high-performance differential-hybrid charge sensitive preamplifier.

PubMed

Zeng, Guoqiang; Hu, Chuanhao; Wei, Shilong; Yang, Jian; Li, Qiang; Ge, Liangquan; Tan, Chengjun

2017-02-01

A differential-hybrid charge sensitive preamplifier (CSP) was designed by taking a monolithic dual N-Channel Junction Field-effect Transistor (JFET) and a high-speed, low-noise, operational amplifier as the core parts. Input-stage of the circuit employs low-noise differential dual JFET, which ensures high input impedance and low noise. The differential dual transistor makes the quiescent point of the first-stage differential output stable, which is convenient for connecting with the post stage high-speed operational amplifier. Broadband could be amplified by connecting to the double differential dual transistors through the folded cascode-bootstrap. The amplifying circuit which replaces the interstage and post stage discrete components of a traditional CSP with integrated operational amplifier is simpler and more reliable. It simplifies the design of the quiescent point, gives full play to advantages of releasing large open-loop gain, and improves charge-voltage conversion gain stability. Particularly, the charge-voltage conversion gain is larger under a smaller feedback capacitor, thus enabling to gain better signal-noise ratio. The designed CSP was tested, reporting 3.3×10 13 V/C charge sensitivity, about 90ns rise time of signals, 35:1 signal-noise ratio to gamma-rays of 137 Cs (662keV) and a 0.023 fC/pF noise slope. Gamma-rays of 241 Am (59.5keV) were measured by the BPX66 detector and the designed CSP under room temperature, providing 1.97% energy resolution. Copyright © 2016 Elsevier Ltd. All rights reserved.

EROIC: a BiCMOS pseudo-gaussian shaping amplifier for high-resolution X-ray spectroscopy

NASA Astrophysics Data System (ADS)

Buzzetti, Siro; Guazzoni, Chiara; Longoni, Antonio

2003-10-01

We present the design and complete characterization of a fifth-order pseudo-gaussian shaping amplifier with 1 μs shaping time. The circuit is optimized for the read-out of signals coming from Silicon Drift Detectors for high-resolution X-ray spectroscopy. The novelty of the designed chip stands in the use of a current feedback loop to place the poles in the desired position on the s-plane. The amplifier has been designed in 0.8 μm BiCMOS technology and fully tested. The EROIC chip comprises also the peak stretcher, the peak detector, the output buffer to drive the external ADC and the pile-up rejection system. The circuit needs a single +5 V power supply and the dissipated power is 5 mW per channel. The digital outputs can be directly coupled to standard digital CMOS ICs. The measured integral-non-linearity of the whole chip is below 0.05% and the achieved energy resolution at the Mn Kα line detected by a 5 mm 2 Peltier-cooled Silicon Drift Detector is 167 eV FWHM.

Ring-shaped active mode-locked tunable laser using quantum-dot semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Zhang, Mingxiao; Wang, Yongjun; Liu, Xinyu

2018-03-01

In this paper, a lot of simulations has been done for ring-shaped active mode-locked lasers with quantum-dot semiconductor optical amplifier (QD-SOA). Based on the simulation model of QD-SOA, we discussed about the influence towards mode-locked waveform frequency and pulse caused by QD-SOA maximum mode peak gain, active layer loss coefficient, bias current, incident light pulse, fiber nonlinear coefficient. In the meantime, we also take the tunable performance of the laser into consideration. Results showed QD-SOA a better performance than original semiconductor optical amplifier (SOA) in recovery time, line width, and nonlinear coefficients, which makes it possible to output a locked-mode impulse that has a higher impulse power, narrower impulse width as well as the phase is more easily controlled. After a lot of simulations, this laser can realize a 20GHz better locked-mode output pulse after 200 loops, where the power is above 17.5mW, impulse width is less than 2.7ps, moreover, the tunable wavelength range is between 1540nm-1580nm.

Optical frequency transfer via a 660 km underground fiber link using a remote Brillouin amplifier.

PubMed

Raupach, S M F; Koczwara, A; Grosche, G

2014-11-03

In long-distance, optical continuous-wave frequency transfer via fiber, remote bidirectional Er³ ⁺ -doped fiber amplifiers are commonly used to mitigate signal attenuation. We demonstrate for the first time the ultrastable transfer of an optical frequency using a remote fiber Brillouin amplifier, placed in a server room along the link. Using it as the only means of remote amplification, on a 660 km loop of installed underground fiber we bridge distances of 250 km and 160 km between amplifications. Over several days of uninterrupted measurement, we find an instability of the frequency transfer (Allan deviation of Λ-weighted data with 1 s gate time) of around 1 × 10(-19) and less for averaging times longer than 3000 s. The modified Allan deviation reaches 3 × 10(-19) at an averaging time of 100 s. Beyond 100 s it follows the interferometer noise floor, and for averaging times longer than 1000 s the modified Allan deviation is in the 10(-20) range. A conservative value of the overall accuracy is 1 × 10(-19)

Reduced transposed flicker noise in microwave oscillators using gaas-based feedforward amplifiers.

PubMed

Everard, Jeremy K A; Broomfield, Carl D

2007-06-01

Transposed flicker noise reduction and removal is demonstrated in 7.6 GHz microwave oscillators for offsets greater than 10 kHz. This is achieved by using a GaAs-based feedforward power amplifier as the oscillation-sustaining stage and incorporating a limiter and resonator elsewhere in the loop. 20 dB noise suppression is demonstrated at 12.5 kHz offset when the error correcting amplifier is switched on. Three oscillator pairs have been built. A transmission line feedback oscillator with a Qo of 180 and two sapphire-based, dielectric resonator oscillators (DROs) with a Qo of 44,500. The difference between the two DROs is a change in the limiter threshold power level of 10 dB. The phase noise rolls-off at (1/f)(2) for offsets greater than 10 kHz for the transmission line oscillator and is set by the thermal noise to within 0-1 dB of the theoretical minimum. The noise performance of the DROs is within 6-12 dB of the theory. Possible reasons for this discrepancy are presented.

Integration of a laser doppler vibrometer and adaptive optics system for acoustic-optical detection in the presence of random water wave distortions

NASA Astrophysics Data System (ADS)

Land, Phillip; Robinson, Dennis; Roeder, James; Cook, Dean; Majumdar, Arun K.

2016-05-01

A new technique has been developed for improving the Signal-to-Noise Ratio (SNR) of underwater acoustic signals measured above the water's surface. This technique uses a Laser Doppler Vibrometer (LDV) and an Adaptive Optics (AO) system (consisting of a fast steering mirror, deformable mirror, and Shack-Hartmann Wavefront Sensor) for mitigating the effect of surface water distortions encountered while remotely recording underwater acoustic signals. The LDV is used to perform non-contact vibration measurements of a surface via a two beam laser interferometer. We have demonstrated the feasibility of this technique to overcome water distortions artificially generated on the surface of the water in a laboratory tank. In this setup, the LDV beam penetrates the surface of the water and travels down to be reflected off a submerged acoustic transducer. The reflected or returned beam is then recorded by the LDV as a vibration wave measurement. The LDV extracts the acoustic wave information while the AO mitigates the water surface distortions, increasing the overall SNR. The AO system records the Strehl ratio, which is a measure of the quality of optical image formation. In a perfect optical system the Strehl ratio is unity, however realistic systems with imperfections have Strehl ratios below one. The operation of the AO control system in open-loop and closed-loop configurations demonstrates the utility of the AO-based LDV for many applications.

Fine pointing control for a Next-Generation Space Telescope

NASA Astrophysics Data System (ADS)

Mosier, Gary E.; Femiano, Michael; Ha, Kong; Bely, Pierre Y.; Burg, Richard; Redding, David C.; Kissil, Andrew; Rakoczy, John; Craig, Larry

1998-08-01

The Next Generation Space Telescope will provide at least ten times the collecting area of the Hubble Space Telescope in a package that fits into the shroud of an expendable launch vehicle. The resulting large, flexible structure provides a challenge to the design of a pointing control system for which the requirements are at the milli-arcsecond level. This paper describes a design concept in which pointing stability is achieved by means of a nested-loop design involving an inertial attitude control system (ACS) and a fast steering mirror (FSM). A key to the integrated control design is that the ACS controllers has a bandwidth well below known structural modes and the FSM uses a rotationally balanced mechanism which should not interact with the flexible modes that are within its control bandwidth. The ACS controller provides stable pointing of the spacecraft bus with star trackers and gyros. This low bandwidth loop uses nearly co-located sensors and actuators to slew and acquire faint guide stars in the NIR camera. This controller provides a payload reference stable to the arcsecond level. Low-frequency pointing errors due to sensor noise and dynamic disturbances are suppressed by a 2-axis gimbaled FSM locate din the instrument module. The FSM servo bandwidth of 6 Hz is intended to keep the guide star position stable in the NIR focal plane to the required milli-arcsecond level. The mirror is kept centered in its range of travel by a low-bandwidth loop closed around the ACS. This paper presents the result of parametric trade studies designed to assess the performance of this control design in the presence of modeled reaction wheel disturbances, assumed to be the principle source of vibration for the NGST, and variations in structural dynamics. Additionally, requirements for reaction wheel disturbance levels and potential vibration isolation subsystems were developed.

Loop mediated isothermal amplification: An innovative gene amplification technique for animal diseases.

PubMed

Sahoo, Pravas Ranjan; Sethy, Kamadev; Mohapatra, Swagat; Panda, Debasis

2016-05-01

India being a developing country mainly depends on livestock sector for its economy. However, nowadays, there is emergence and reemergence of more transboundary animal diseases. The existing diagnostic techniques are not so quick and with less specificity. To reduce the economy loss, there should be a development of rapid, reliable, robust diagnostic technique, which can work with high degree of sensitivity and specificity. Loop mediated isothermal amplification assay is a rapid gene amplification technique that amplifies nucleic acid under an isothermal condition with a set of designed primers spanning eight distinct sequences of the target. This assay can be used as an emerging powerful, innovative gene amplification diagnostic tool against various pathogens of livestock diseases. This review is to highlight the basic concept and methodology of this assay in livestock disease.

Open loop model for WDM links

NASA Astrophysics Data System (ADS)

D, Meena; Francis, Fredy; T, Sarath K.; E, Dipin; Srinivas, T.; K, Jayasree V.

2014-10-01

Wavelength Division Multiplexing (WDM) techniques overfibrelinks helps to exploit the high bandwidth capacity of single mode fibres. A typical WDM link consisting of laser source, multiplexer/demultiplexer, amplifier and detectoris considered for obtaining the open loop gain model of the link. The methodology used here is to obtain individual component models using mathematical and different curve fitting techniques. These individual models are then combined to obtain the WDM link model. The objective is to deduce a single variable model for the WDM link in terms of input current to system. Thus it provides a black box solution for a link. The Root Mean Square Error (RMSE) associated with each of the approximated models is given for comparison. This will help the designer to select the suitable WDM link model during a complex link design.

High-energy gamma-ray emission from pion decay in a solar flare magnetic loop

NASA Technical Reports Server (NTRS)

Mandzhavidze, Natalie; Ramaty, Reuven

1992-01-01

The production of high-energy gamma rays resulting from pion decay in a solar flare magnetic loop is investigated. Magnetic mirroring, MHD pitch-angle scattering, and all of the relevant loss processes and photon production mechanisms are taken into account. The transport of both the primary ions and the secondary positrons resulting from the decay of the positive pions, as well as the transport of the produced gamma-ray emission are considered. The distributions of the gamma rays as a function of atmospheric depth, time, emission angle, and photon energy are calculated and the dependence of these distributions on the model parameters are studied. The obtained angular distributions are not sufficiently anisotropic to account for the observed limb brightening of the greater than 10 MeV flare emission, indicating that the bulk of this emission is bremsstrahlung from primary electrons.

Dual physiological rate measurement instrument

NASA Technical Reports Server (NTRS)

Cooper, Tommy G. (Inventor)

1990-01-01

The object of the invention is to provide an instrument for converting a physiological pulse rate into a corresponding linear output voltage. The instrument which accurately measures the rate of an unknown rectangular pulse wave over an extended range of values comprises a phase-locked loop including a phase comparator, a filtering network, and a voltage-controlled oscillator, arranged in cascade. The phase comparator has a first input responsive to the pulse wave and a second input responsive to the output signal of the voltage-controlled oscillator. The comparator provides a signal dependent on the difference in phase and frequency between the signals appearing on the first and second inputs. A high-input impedance amplifier accepts an output from the filtering network and provides an amplified output DC signal to a utilization device for providing a measurement of the rate of the pulse wave.

Experimental investigation of polarization insensitivity and cascadability with semiconductor optical amplifier-based differential phase-shift keyed wavelength converter

NASA Astrophysics Data System (ADS)

Mao, Yaya; Wu, Chongqing; Liu, Bo; Ullah, Rahat; Tian, Feng

2017-12-01

We experimentally investigate the polarization insensitivity and cascadability of an all-optical wavelength converter for differential phase-shift keyed (DPSK) signals for the first time. The proposed wavelength converter is composed of a one-bit delay interferometer demodulation stage followed by a single semiconductor optical amplifier. The impact of input DPSK signal polarization fluctuation on receiver sensitivity for the converted signal is carried out. It is found that this scheme is almost insensitive to the state of polarization of the input DPSK signal. Furthermore, the cascadability of the converter is demonstrated in a two-path recirculating loop. Error-free transmission is achieved with 20 stage cascaded wavelength conversions over 2800 km, where the power penalty is <3.4 dB at bit error rate of 10-9.

Optical fiber sources and transmission controls for multi-Tb/s systems

NASA Astrophysics Data System (ADS)

Nowak, George Adelbert

The accelerating demand for bandwidth capacity in backbone links of terrestrial communications systems is projected to exceed 1Tb/s by 2002. Lightwave carrier frequencies and fused-silica optical fibers provide the natural combination of high passband frequencies and low- loss medium to satisfy this evolving demand for bandwidth capacity. This thesis addresses three key technologies for enabling multi-Tb/s optical fiber communication systems. The first technology is a broadband source based on supercontinuum generation in optical fiber. Using a single modelocked laser with output pulsewidths of 0.5psec pulses, we generate in ~2m of dispersion-shifted fiber more that 200nm of spectral continuum in the vicinity of 1550nm that is flat to better than +/- 0.5 dB over more than 60nm. The short fiber length prevents degradation of timing jitter of the seed pulses and preserves coherence of the continuum by inhibiting environmental perturbations and mapping of random noise from the vicinity of the input pulse across the continuum. Through experiments and simulations, we find that the continuum characteristics result from 3rd order dispersion effects on higher-order soliton compression. We determine optimal fiber properties to provide desired continuum broadness and flatness for given input pulsewidth and energy conditions. The second technology is a novel delay-shifted nonlinear optical loop mirror (DS-NOLM) that performs a transmission control function by serving as an intensity filter and frequency compensator for <5psec soliton transmission systems. A theoretical and experimental study of the DS-NOLM as a transmission control element in a periodically amplified soliton transmission system is presented. We show that DS-NOLMs enable 4ps soliton transmission over 75km of standard dispersion fiber, with 25km spacing between amplifiers, by filtering the dispersive waves and compensating for Raman-induced soliton self-frequency shift. The third technology is all-fiber wavelength conversion employing induced modulational instability. We obtain wavelength conversion over 40nm with a peak conversion efficiency of 28dB using 600mW pump pulses in 720m of high-nonlinearity optical fiber. We show that the high- nonlinearity fiber enhances the phase-matching bandwidth as well as reducing the required fiber lengths and pump powers.

Mars Global Surveyor Ka-Band Frequency Data Analysis

NASA Astrophysics Data System (ADS)

Morabito, D.; Butman, S.; Shambayati, S.

2000-01-01

The Mars Global Surveyor (MGS) spacecraft, launched on November 7, 1996, carries an experimental space-to-ground telecommunications link at Ka-band (32 GHz) along with the primary X-band (8.4 GHz) downlink. The signals are simultaneously transmitted from a 1.5-in diameter parabolic high gain antenna (HGA) on MGS and received by a beam-waveguide (BWG) R&D 34-meter antenna located in NASA's Goldstone Deep Space Network (DSN) complex near Barstow, California. The projected 5-dB link advantage of Ka-band relative to X-band was confirmed in previous reports using measurements of MGS signal strength data acquired during the first two years of the link experiment from December 1996 to December 1998. Analysis of X-band and Ka-band frequency data and difference frequency (fx-fka)/3.8 data will be presented here. On board the spacecraft, a low-power sample of the X-band downlink from the transponder is upconverted to 32 GHz, the Ka-band frequency, amplified to I-W using a Solid State Power Amplifier, and radiated from the dual X/Ka HGA. The X-band signal is amplified by one of two 25 W TWTAs. An upconverter first downconverts the 8.42 GHz X-band signal to 8 GHz and then multiplies using a X4 multiplier producing the 32 GHz Ka-band frequency. The frequency source selection is performed by an RF switch which can be commanded to select a VCO (Voltage Controlled Oscillator) or USO (Ultra-Stable Oscillator) reference. The Ka-band frequency can be either coherent with the X-band downlink reference or a hybrid combination of the USO and VCO derived frequencies. The data in this study were chosen such that the Ka-band signal is purely coherent with the X-band signal, that is the downconverter is driven by the same frequency source as the X-band downlink). The ground station used to acquire the data is DSS-13, a 34-meter BWG antenna which incorporates a series of mirrors inside beam waveguide tubes which guide the energy to a subterranean pedestal room, providing a stable environment for the feed and electronics equipment. A dichroic plate is used to reflect the X-band energy and pass the Ka-band energy to another mirror. The RF energy for each band is then focused onto a feed horn and low-noise amplifier package. After amplification and RF/IF downconversion, the IF signals are sent to the Experimental Tone Tracker (ETT), a digital phase-lock-loop receiver, which simultaneously tracks both X-band and Ka-band carrier signals. Once a signal is detected, the ETT outputs estimates of the SNR in a I -Hz bandwidth (Pc/No), baseband phase and frequency of the signals every I -sec. Between December 1996 and December 1998, the Ka-band and X-band signals from MGS were tracked on a regular basis using the ETT. The Ka-band downlink frequencies described here were referenced to the spacecraft's on-board USO which was also the X-band frequency reference (fka= 3.8 fx). The ETT estimates of baseband phase at I -second sampled time tags were converted to sky frequency estimates. Frequency residuals were then generated for each band by removing a model frequency from each observable frequency at each time tag. The model included Doppler and other effects derived from spacecraft trajectory files obtained from the MGS Navigation Team. A simple troposphere correction was applied to the data. In addition to residuals, the USO frequencies emitted by the spacecraft were estimated. For several passes, the USO frequencies were determined from X-band data and from Ka-band data (referred to X-band by dividing by 3.8) and were found to be in good agreement. In addition, X-band USO frequency estimates from MGS Radio Science data acquired from operational DSN stations were available for comparison and were found to agree within the I Hz level. The remaining sub-Hertz differences were attributed to the different models and software algorithms used by MGS Radio Science and KaBLE-11. A summary of the results of a linear fit of the USO frequency versus time (day of year) is presented in Table I for an initial segment of passes.

Software Development for the Hobby-Eberly Telescope's Segment Alignment Maintenance System using LABView

NASA Technical Reports Server (NTRS)

Hall, Drew P.; Ly, William; Howard, Richard T.; Weir, John; Rakoczy, John; Roe, Fred (Technical Monitor)

2002-01-01

The software development for an upgrade to the Hobby-Eberly Telescope (HET) was done in LABView. In order to improve the performance of the HET at the McDonald Observatory, a closed-loop system had to be implemented to keep the mirror segments aligned during periods of observation. The control system, called the Segment Alignment Maintenance System (SAMs), utilized inductive sensors to measure the relative motions of the mirror segments. Software was developed in LABView to tie the sensors, operator interface, and mirror-control motors together. Developing the software in LABView allowed the system to be flexible, understandable, and able to be modified by the end users. Since LABView is built using block diagrams, the software naturally followed the designed control system's block and flow diagrams, and individual software blocks could be easily verified. LABView's many built-in display routines allowed easy visualization of diagnostic and health-monitoring data during testing. Also, since LABView is a multi-platform software package, different programmers could develop the code remotely on various types of machines. LABView s ease of use facilitated rapid prototyping and field testing. There were some unanticipated difficulties in the software development, but the use of LABView as the software "language" for the development of SAMs contributed to the overall success of the project.

Detection of somatic mutations in the mitochondrial DNA control region D-loop in brain tumors: The first report in Malaysian patients.

PubMed

Mohamed Yusoff, Abdul Aziz; Mohd Nasir, Khairol Naaim; Haris, Khalilah; Mohd Khair, Siti Zulaikha Nashwa; Abdul Ghani, Abdul Rahman Izaini; Idris, Zamzuri; Abdullah, Jafri Malin

2017-11-01

Although the role of nuclear-encoded gene alterations has been well documented in brain tumor development, the involvement of the mitochondrial genome in brain tumorigenesis has not yet been fully elucidated and remains controversial. The present study aimed to identify mutations in the mitochondrial DNA (mtDNA) control region D-loop in patients with brain tumors in Malaysia. A mutation analysis was performed in which DNA was extracted from paired tumor tissue and blood samples obtained from 49 patients with brain tumors. The D-loop region DNA was amplified using the PCR technique, and genetic data from DNA sequencing analyses were compared with the published revised Cambridge sequence to identify somatic mutations. Among the 49 brain tumor tissue samples evaluated, 25 cases (51%) had somatic mutations of the mtDNA D-loop, with a total of 48 mutations. Novel mutations that had not previously been identified in the D-loop region (176 A-deletion, 476 C>A, 566 C>A and 16405 A-deletion) were also classified. No significant associations between the D-loop mutation status and the clinicopathological parameters were observed. To the best of our knowledge, the current study presents the first evidence of alterations in the mtDNA D-loop regions in the brain tumors of Malaysian patients. These results may provide an overview and data regarding the incidence of mitochondrial genome alterations in Malaysian patients with brain tumors. In addition to nuclear genome aberrations, these specific mitochondrial genome alterations may also be considered as potential cancer biomarkers for the diagnosis and staging of brain cancers.

The effect of system nonlinearities on system noise statistics

NASA Technical Reports Server (NTRS)

Robinson, L. H., Jr.

1971-01-01

The effects are studied of nonlinearities in a baseline communications system on the system noise amplitude statistics. So that a meaningful identification of system nonlinearities can be made, the baseline system is assumed to transmit a single biphase-modulated signal through a relay satellite to the receiving equipment. The significant nonlinearities thus identified include square-law or product devices (e.g., in the carrier reference recovery loops in the receivers), bandpass limiters, and traveling wave tube amplifiers.

Embryo Sexing and Sex Chromosomal Chimerism Analysis by Loop-Mediated Isothermal Amplification in Cattle and Water Buffaloes

PubMed Central

HIRAYAMA, Hiroki; KAGEYAMA, Soichi; MORIYASU, Satoru; SAWAI, Ken; MINAMIHASHI, Akira

2013-01-01

Abstract In domestic animals of the family Bovidae, sex preselection of offspring has been demanded for convenience of milk/beef production and animal breeding. Development of the nonsurgical embryo transfer technique and sexing methods of preimplantation embryos made it possible. Sexing based on detection of Y chromosome-specific DNA sequences is considered the most reliable method to date. PCR enables amplification of a target sequence from a small number of blastomeres. However, it requires technical skill and is time consuming. Furthermore, PCR has the risk of false positives because of DNA contamination during handling of the PCR products in duplicate PCR procedures and/or electrophoresis. Therefore, for embryo sexing to become widely used in the cattle embryo transfer industry, a simple, rapid and precise sexing method needs to be developed. Loop-mediated isothermal amplification (LAMP) is a novel DNA amplification method, and the reaction is carried out under isothermal conditions (range, 60 to 65 C) using DNA polymerase with strand displacement activity. When the target DNA is amplified by LAMP, a white precipitate derived from magnesium pyrophosphate (a by-product of the LAMP reaction) is observed. It is noteworthy that LAMP does not need special reagents or electrophoresis to detect the amplified DNA. This review describes the development and application of an embryo sexing method using LAMP in cattle and water buffaloes. PMID:23965599

Efficient and Specific Detection of Salmonella in Food Samples Using a stn-Based Loop-Mediated Isothermal Amplification Method

PubMed Central

2015-01-01

The Salmonella enterotoxin (stn) gene exhibits high homology among S. enterica serovars and S. bongori. A set of 6 specific primers targeting the stn gene were designed for detection of Salmonella spp. using the loop-mediated isothermal amplification (LAMP) method. The primers amplified target sequences in all 102 strains of 87 serovars of Salmonella tested and no products were detected in 57 non-Salmonella strains. The detection limit in pure cultures was 5 fg DNA/reaction when amplified at 65°C for 25 min. The LAMP assay could detect Salmonella in artificially contaminated food samples as low as 220 cells/g of food without a preenrichment step. However, the sensitivity was increased 100-fold (~2 cells/g) following 5 hr preenrichment at 35°C. The LAMP technique, with a preenrichment step for 5 and 16 hr, was shown to give 100% specificity with food samples compared to the reference culture method in which 67 out of 90 food samples gave positive results. Different food matrixes did not interfere with LAMP detection which employed a simple boiling method for DNA template preparation. The results indicate that the LAMP method, targeting the stn gene, has great potential for detection of Salmonella in food samples with both high specificity and high sensitivity. PMID:26543859

Experimental Analysis of Diffraction Effects from a Segmented MEMS Deformable Mirror for a Closed Loop Adaptive Optics System

DTIC Science & Technology

2010-06-01

different approaches were used to model MEMS OM as a grating in Zemax software. First, a 2D grating was directly modeled as a combination of two ID...method of modeling ~IEMS DM in Zemax was implemented by combining two ID gratings. Due to the fact that ZEl\\’IAX allows to easily use ID physical...optics shows thc far field diffractioll pattcrn, which in Zemax geometrical model shows up as distinct spots. each one corresponding to a specific

Sub-μrad laser beam tracking

NASA Astrophysics Data System (ADS)

Buske, Ivo; Riede, Wolfgang

2006-09-01

We compare active optical elements based on different technologies to accomplish the requirements of a 2-dim. fine tracking control system. A cascaded optically and electrically addressable spatial light modulator (OASLM) based on liquid crystals (LC) is used for refractive beam steering. Spatial light modulators provide a controllable phase wedge to generate a beam deflection. Additionally, a tip/tilt mirror approach operating with piezo-electric actuators is investigated. A digital PID controller is implemented for closed-loop control. Beam tracking with a root-mean-squared accuracy of Δα=30 nrad has been laboratory-confirmed.

Feedback stabilization of quantum cascade laser beams for stand-off applications

NASA Astrophysics Data System (ADS)

Müller, Reik; Kendziora, Christopher A.; Furstenberg, Robert

2017-05-01

Techniques which apply tunable quantum cascade lasers (QCLs) for target illumination suffer from fluctuations of the laser beam direction. This manuscript describes a method to stabilize the beam direction by using an active feedback loop. This approach corrects and stabilizes the laser pointing direction using the signal from a 4-element photo sensor as input to control an active 2 dimensional Galvo mirror system. Results are presented for measurements using known perturbations as well as actual mode hops intrinsic to external cavity QCL during wavelength tuning.

High-contrast imaging with an arbitrary aperture: active correction of aperture discontinuities

NASA Astrophysics Data System (ADS)

Pueyo, Laurent; Norman, Colin; Soummer, Rémi; Perrin, Marshall; N'Diaye, Mamadou; Choquet, Elodie

2013-09-01

We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for future Extremely Large Telescopes, even when the pupil features a missing segment" . We show that the converging non-linear mappings resulting from our Deformable Mirror shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and strut's while not amplifying the diffraction at the aperture edges beyond the Fresnel regime and illustrate the broadband properties of ACAD in the case of the pupil configuration corresponding to the Astrophysics Focused Telescope Assets. Since details about these telescopes are not yet available to the broader astronomical community, our test case is based on a geometry mimicking the actual one, to the best of our knowledge.

Sensing mode coupling analysis for dual-mass MEMS gyroscope and bandwidth expansion within wide-temperature range

NASA Astrophysics Data System (ADS)

Cao, Huiliang; Li, Hongsheng; Shao, Xingling; Liu, Zhiyu; Kou, Zhiwei; Shan, Yanhu; Shi, Yunbo; Shen, Chong; Liu, Jun

2018-01-01

This paper presents the bandwidth expanding method with wide-temperature range for sense mode coupling dual-mass MEMS gyro. The real sensing mode of the gyroscope is analyzed to be the superposition of in-phase and anti-phase sensing modes. The mechanical sensitivity and bandwidth of the gyroscope structure are conflicted with each other and both governed by the frequency difference between sensing and drive modes (min {Δω1, Δω2}). The sensing mode force rebalancing combs stimulation method (FRCSM) is presented to simulate the Coriolis force, and based on this method, the gyro's dynamic characteristics are tested. The sensing closed- loop controller is achieved by operational amplifier based on phase lead method, which enable the magnitude margin and phase margin of the system to reach 7.21 dB and 34.6° respectively, and the closed-loop system also expands gyro bandwidth from 13 Hz (sensing open-loop) to 102 Hz (sensing closed-loop). What's more, the turntable test results show that the sensing closed-loop works stably in wide-temperature range (from -40 °C to 60 °C) and the bandwidth values are 107 Hz @-40 °C and 97 Hz @60 °C. The results indicate that the higher temperature causes lower bandwidth, and verify the simulation results are 103 Hz @-40 °C and 98.2 Hz @60 °C. The new bottleneck of the closed loop bandwidth is the valley generated by conjugate zeros, which is formed by superposition of sensing modes.

Parity-time–symmetric optoelectronic oscillator

PubMed Central

2018-01-01

An optoelectronic oscillator (OEO) is a hybrid microwave and photonic system incorporating an amplified positive feedback loop to enable microwave oscillation to generate a high-frequency and low–phase noise microwave signal. The low phase noise is ensured by the high Q factor of the feedback loop enabled by the use of a long and low-loss optical fiber. However, an OEO with a long fiber loop would have a small free spectral range, leading to a large number of closely spaced oscillation modes. To ensure single-mode oscillation, an ultranarrowband optical filter must be used, but such an optical filter is hard to implement and the stability is poor. Here, we use a novel concept to achieve single-mode oscillation without using an ultranarrowband optical filter. The single-mode operation is achieved based on parity-time (PT) symmetry by using two identical feedback loops, with one having a gain and the other having a loss of the same magnitude. The operation is analyzed theoretically and verified by an experiment. Stable single-mode oscillation at an ultralow phase noise is achieved without the use of an ultranarrowband optical filter. The use of PT symmetry in an OEO overcomes the long-existing mode-selection challenge that would greatly simplify the implementation of OEOs for ultralow–phase noise microwave generation. PMID:29888325

Optimizing the feedback control of Galvo scanners for laser manufacturing systems

NASA Astrophysics Data System (ADS)

Mirtchev, Theodore; Weeks, Robert; Minko, Sergey

2010-06-01

This paper summarizes the factors that limit the performance of moving-magnet galvo scanners driven by closed-loop digital servo amplifiers: torsional resonances, drifts, nonlinearities, feedback noise and friction. Then it describes a detailed Simulink® simulator that takes into account these factors and can be used to automatically tune the controller for best results with given galvo type and trajectory patterns. It allows for rapid testing of different control schemes, for instance combined position/velocity PID loops and displays the corresponding output in terms of torque, angular position and feedback sensor signal. The tool is configurable and can either use a dynamical state-space model of galvo's open-loop response, or can import the experimentally measured frequency domain transfer function. Next a drive signal digital pre-filtering technique is discussed. By performing a real-time Fourier analysis of the raw command signal it can be pre-warped to minimize all harmonics around the torsional resonances while boosting other non-resonant high frequencies. The optimized waveform results in much smaller overshoot and better settling time. Similar performance gain cannot be extracted from the servo controller alone.

An Engineering Perspective of External Cardiac Loop Recorder: A Systematic Review

PubMed Central

2016-01-01

External cardiac loop recorder (ELR) is a kind of ECG monitoring system that records cardiac activities of a subject continuously for a long time. When the heart palpitations are not the frequent and nonspecific character, it is difficult to diagnose the disease. In such a case, ELR is used for long-term monitoring of heart signal of the patient. But the cost of ELR is very high. Therefore, it is not prominently available in developing countries like India. Since the design of ELR includes the ECG electrodes, instrumentation amplifier, analog to digital converter, and signal processing unit, a comparative review of each part of the ELR is presented in this paper in order to design a cost effective, low power, and compact kind of ELR. This review will also give different choices available for selecting and designing each part of the ELR system. Finally, the review will suggest the better choice for designing a cost effective external cardiac loop recorder that helps to make it available even for rural people in India. PMID:27872843

AOF LTAO mode: reconstruction strategy and first test results

NASA Astrophysics Data System (ADS)

Oberti, Sylvain; Kolb, Johann; Le Louarn, Miska; La Penna, Paolo; Madec, Pierre-Yves; Neichel, Benoit; Sauvage, Jean-François; Fusco, Thierry; Donaldson, Robert; Soenke, Christian; Suárez Valles, Marcos; Arsenault, Robin

2016-07-01

GALACSI is the Adaptive Optics (AO) system serving the instrument MUSE in the framework of the Adaptive Optics Facility (AOF) project. Its Narrow Field Mode (NFM) is a Laser Tomography AO (LTAO) mode delivering high resolution in the visible across a small Field of View (FoV) of 7.5" diameter around the optical axis. From a reconstruction standpoint, GALACSI NFM intends to optimize the correction on axis by estimating the turbulence in volume via a tomographic process, then projecting the turbulence profile onto one single Deformable Mirror (DM) located in the pupil, close to the ground. In this paper, the laser tomographic reconstruction process is described. Several methods (virtual DM, virtual layer projection) are studied, under the constraint of a single matrix vector multiplication. The pseudo-synthetic interaction matrix model and the LTAO reconstructor design are analysed. Moreover, the reconstruction parameter space is explored, in particular the regularization terms. Furthermore, we present here the strategy to define the modal control basis and split the reconstruction between the Low Order (LO) loop and the High Order (HO) loop. Finally, closed loop performance obtained with a 3D turbulence generator will be analysed with respect to the most relevant system parameters to be tuned.

Closed loop adaptive optics for microscopy without a wavefront sensor

PubMed Central

Kner, Peter; Winoto, Lukman; Agard, David A.; Sedat, John W.

2013-01-01

A three-dimensional wide-field image of a small fluorescent bead contains more than enough information to accurately calculate the wavefront in the microscope objective back pupil plane using the phase retrieval technique. The phase-retrieved wavefront can then be used to set a deformable mirror to correct the point-spread function (PSF) of the microscope without the use of a wavefront sensor. This technique will be useful for aligning the deformable mirror in a widefield microscope with adaptive optics and could potentially be used to correct aberrations in samples where small fluorescent beads or other point sources are used as reference beacons. Another advantage is the high resolution of the retrieved wavefont as compared with current Shack-Hartmann wavefront sensors. Here we demonstrate effective correction of the PSF in 3 iterations. Starting from a severely aberrated system, we achieve a Strehl ratio of 0.78 and a greater than 10-fold increase in maximum intensity. PMID:24392198

Non-linear dynamic compensation system

NASA Technical Reports Server (NTRS)

Lin, Yu-Hwan (Inventor); Lurie, Boris J. (Inventor)

1992-01-01

A non-linear dynamic compensation subsystem is added in the feedback loop of a high precision optical mirror positioning control system to smoothly alter the control system response bandwidth from a relatively wide response bandwidth optimized for speed of control system response to a bandwidth sufficiently narrow to reduce position errors resulting from the quantization noise inherent in the inductosyn used to measure mirror position. The non-linear dynamic compensation system includes a limiter for limiting the error signal within preselected limits, a compensator for modifying the limiter output to achieve the reduced bandwidth response, and an adder for combining the modified error signal with the difference between the limited and unlimited error signals. The adder output is applied to control system motor so that the system response is optimized for accuracy when the error signal is within the preselected limits, optimized for speed of response when the error signal is substantially beyond the preselected limits and smoothly varied therebetween as the error signal approaches the preselected limits.

Program user's manual: cryogen system for the analysis for the Mirror Fusion Test Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1979-04-01

The Mirror Fusion Test Facility being designed and constructed at the Lawrence Livermore Laboratory requires a liquid helium liquefaction, storage, distribution, and recovery system and a liquid nitrogen storage and distribution system. To provide a powerful analytical tool to aid in the design evolution of this system through hardware, a thermodynamic fluid flow model was developed. This model allows the Lawrence Livermore Laboratory to verify that the design meets desired goals and to play what if games during the design evolution. For example, what if the helium flow rate is changed in the magnet liquid helium flow loop; how doesmore » this affect the temperature, fluid quality, and pressure. This manual provides all the information required to run all or portions of this program as desired. In addition, the program is constructed in a modular fashion so changes or modifications can be made easily to keep up with the evolving design.« less