Synchroscan Streak Camera Research Articles

Urbach rule in luminescence and dynamics of a momentarily localized exciton in PbI 2 and HgI 2

The Urbach-Martienssen rule for luminescence spectra is experimentally established for the first time in PbI 2 and HgI 2, as theoretically suggested by Sumi and Toyozawa. This fact means that the exciton having an energy corresponding to the Urbach tail (Urbach excition) is in thermal equilibrium. It is suggested from the excitation spectra of the luminescence quantum yield that the free and Urbach excitons are not in thermal equilibrium with each other. The luminescence decay times of the free and Urbach excitons are measured in HgI 2 by using a combination system of a picosecond mode-locked YAG laser and a synchroscan streak camera. As they depend strongly on the sample, the lifetimes of not only the free exciton but also the Urbach exciton are considered to be governed by the density of impurities or defects in the crystal.

Effects of an Electric Field on the Decay Time of Luminescence from a GaAs/Ga0.6Al0.4As Multi-Quantum-Well Structure

The decay time of luminescence from a multi-quantum well has been measured at 20 K by using a cw mode-locked Kr laser and a synchroscan-streak camera. The decay time was found to increase with applied electric field. The increase is considered to be attributable to a field-induced carrier separation. The decay time depends on the observed wavelength of luminescence. This dependence changes with the electric field, suggesting that the energy-decreasing rate of excitons becomes slower in the presence of an electric field.

Multimode dispersion behavior in optical fibers at high resolution

Multimode dispersion behavior in optical-fiber propagation is observed by using a synchroscan streak camera. Sharp optical pulses are applied to fibers of limited bandwidth. Temporal delays are studied in conjunction with spatial- or chromatic-mode distribution. Various features of group-delay properties are observed. In addition to the conventional mode broadening due to intermode coupling in some fibers, pulse splitting without broadening is observed. It is found that all the kinds of propagation behavior are dependent on the fiber fabrication sources, even though the fiber parameters are similar.

Observation of the diffusion-free intermolecular excimer of 9-methyladenine in aqueous solution by picosecond time-resolved spectroscopy

Diffusion-free intermolecular excimer formation in liquid solution is observed for an aqueous solution of 9-methyladenine using the synchroscan streak camera technique. The excimer fluorescence (330 ps lifetime) appears at 380 nm, at longer wavelength than the monomer fluorescence (5 ps lifetime). The excimer is formed via a weakly coupled stacking dimer composed of ground-state monomers.

Spectral and temporal study of picosecond-pulse propagation in a single-mode optical fibre

The power-dependent pulsewidth variations for input 85 ps pulses from a cw mode-locked Nd: YAG laser propagating through 125 m of single-mode optical fibre have been examined using a Synchroscan streak camera. Simultaneous spectral and temporal measurements provide information as to the optimum parameters for pulse compression in fibres.

Measurement of the weak Luminescence from the Semiconductor by Synchroscan Streak Camera system

Measurement of the weak Luminescence from the Semiconductor by Synchroscan Streak Camera system

A theoretical analysis of the time resolution of a synchroscan streak camera

A statistical method has been developed to treat the phase jitter between the laser pulse and the deflection Signal and the amplitude jitter of the deflection voltage of a synchroscan streak camera. Using normal distribution functions to model these random jitters, an expression for the recorded pulsewidth of a synchroscan streak camera has been obtained. With the aid of this expression, some experimental observations may be explained.

Measurement of 1.3 and 1.55 μm gain-switched semiconductor laser pulses with a picosecond IR streak camera and a high-speed InGaAs PIN photodiode

Gain-switched semiconductor laser pulses at 1.3 and 1.55 μm were measured both with a high-speed InGaAs PIN photodiode and an IR synchroscan streak camera. Gain-switching characteristics and their bias dependence observed with both detection schemes are consistent with each other. Laser pulses of 24-30 ps duration are observed. Picosecond pulses from a gain-switched 1.55 μm DFB laser are found to be chirped but not transform-limited.

Picosecond UV Fluorescence Spectroscopy of Bacteriorhodopsin

UV fluorescence spectroscopic behaviors in the picosecond time region for purple membrane were investigated by a method of a two-dimensional synchroscan streak camera with a mode-locked and internally frequency-doubled CW ring dye laser. The UV fluorescence from the tryptophans in bacteriorhodopsin shows the exponentially decaying profile of two components (about 130 and 650 ps). The peaks of the emission bands of the first and slow components are around 325 and 340 nm., respectively. These results show that the circumstance surrounding eight tryptophans in bacteriorhodopsin is at least sorted to the polar and nonpolar in ones. Furthermore, by applying Forster theory of energy transfer to the results, it is determined that the mean distance between the tryptophan indicating the fast fluorescence decay and the chromophore and that for the slow decay are 31 and 26 A. These support the following deduction from another analysis of stereographical conformation of bacteriorhodopsin; the membrane-buried protein has the “INSIDE OUT” conformation.

シンクロスキャンストリークカメラによる極微弱ピコ秒時間分解発光スペクトル計測

シンクロスキャンストリークカメラによる極微弱ピコ秒時間分解発光スペクトル計測

A single-photon sensitive synchroscan streak camera for room temperature picosecond emission dynamics of adenine and polyadenylic acid

It is experimentally verified that a synchroscan streak camera, incorporating a microchannel plate and synchronizing with UV picosecond pulses generated inside the cavity of a mode-locked CW ring dye laser, has enough sensitivity to detect picosecond emission phenomena in the region of a single-photon event. To demonstrate the usefulness of the synchroscan streak camera, the first measurement of time- and wavelength-resolved emissions in the picosecond region is successfully carried out for adenine and polyadenylic acid aqueous solutions at room temperature, and shows that their shortest lifetimes, due to the monomer fluorescence, are 6 and 8 ps, respectively.

Picosecond time-resolved fluorescence spectroscopy of hematoporphyrin derivative

The picosecond time-resolved fluorescence decays I(t) and spectra I(\lambda, t) for hematoporphyrin derivative (HPD) in a phosphate buffer saline aqueous solution at different concentrations ( 8.4 \times 10^{-6}\sim 8.4 \times 10^{-3} M) are measured by a two-dimensional synchroscan streak camera with a mode-locked CW dye laser, and a new emission band (which we call the Y -band) is found at high concentration. It is shown that the fluorescence decays composed of fast and slow components at high concentration are due to the Y -band (120 ps lifetime) from head-to-tail aggregates including equilibrium dimer and stable dimer, and the usual band (3.6 ns lifetime) from monomer, respectively, and the latter band is dynamically quenched by the Forster type resonance energy transfer from the monomer to the aggregate. Furthermore, the measurement of static fluorescence spectra from human gastric cancers and the surrounding in vivo after HPD injection shows that a band corresponding to the Y -band from the aggregate appears at only the cancerous cells.

Quantitative XPS surface chemical analysis and direct measurement of the temporal response times of glass-bonded NEA GaAs transmission photocathodes

Semitransparent GaAs films bonded on to glass substrates with a GaxAl1-xAs strain-matching layer have been activated to give negative electron affinity (NEA) characteristics in a commercial UHV apparatus. Quantitative surface analysis of the photocathodes before and after activation show a Cs-O overlayer with a well defined Cs2O stoichiometry and a thickness of approximately 1.3 nm. Measurements of photoelectron energy distribution curves (EDC) from the cathodes confirm the NEA mode of operation, giving very narrow almost wavelength-independent 'thermalised' electron distributions throughout the photosensitivity range. Measurements of the response times of different GaAs NEA cathodes using a special UHV demountable Synchroscan streak camera gave response times as low as approximately 8 ps, suggesting the feasibility of a medium-high temporal resolution streak camera sensitive in the technologically important 1.3-1.55 mu m spectral region.

Time-Resolved Polarized Fluorescence of C-Phycocyanin and Its Subunits from Mastigocladus laminosus

The influence of aggregation and temperature on the excited state kinetics of C-phycocyanin from Mastiqocladus laminosus has been studied. Polarized fluorescence decay curves have been recorded using a synchronously pumped dye laser in conjunction with a synchroscan streak camera. The experimental data for all samples can be fit satisfactorily assuming a biexponential decay law. Fluorescence depolarization times have been interpreted in terms of energy transfer among the different chromophores. The influence of temperature is only moderate on the intra­molecular relaxation, but pronounced on the rates of energy transfer. Both are dependent on the size of the aggregate. The biexponential decay of the α-subunit containing only one chromophore, indicates the presence of different subsets of chromophores in these samples. The results are discussed in terms of variations of the chromophore arrangements upon temperature induced changes in the protein conformation.

Synchroscan streak camera study of potential saturable absorbers in the blue spectral region

The viscocity-dependent fluorescence lifetime of some cyanine dyes with peak absorption cross-sections in the 350–500 nm range have been examined using a synchronously operating strek camera in conjunction with the picosecond excitation pulses from a frequency doubled synchronously pumped c.w. dye laser. Through increases in the recovery time of a saturable absorber by employing viscous solutions, the necessary saturation flux is conveniently reduced and passive mode locking of laser systems can occur more easily. This is illustrated by the application of one of the dyes to the mode locking of the coumarin 102 dye laser.

Stroboscopic operation of a synchroscan streak camera

A synchronously driven streak camera with stroboscopic deflection drive and detection provides picosecond time resolution with direct photomultiplier read-out over an extended free temporal range. This technique and its limitations are described. The temporal resolution has been demonstrated to approach that obtained from the camera when operated in the conventional synchroscan mode employing an actively mode locked dye laser source. The increased temporal window has permitted the measurement of fluorescence lifetimes of several nanoseconds for various dye species.

A Compact Synchroscan Streak Camera Using a Microchannel Plate Incorporated Tube

A compact synchroscan streak camera, which incorporates a microchannel plates providing a high light gain, has been constructed. The camera has been operated in synchronism with a synchronous-passive hybrid mode-locked CW dye laser, and the overall time resolution has been 10.8 and 25.9 ps for a recording of ~160 and ~108 cycles of dye laser pulses, respectively. In addition, by using the camera system with the dye laser a weak fluorescence profile (a quantum yield of ~10-3) of an important biomolecule has been directly observed on a picosecond time scale.

Picosecond-Duration Vibrational Relaxation Kinetics in the Excited S1 State of Perylene and Anthracene Molecules

We present and discuss the results of a direct observation of the picosecond range temporal behavior of vibronic lines in the luminescence spectrum of the matrix-isolated perylene and anthracene molecules. A novel subtractive dispersion mount of monochromators in conjunction with the synchroscan streak camera has been used. From spectrochronograms measured at different excitation wavelengths the vibrational energy relaxation times have been obtained. These are in the range of 20–30 ps and are most probably determined by the existence of the phonon bath of the matrix. A comparison of the measured relaxation constants with those estimated from the steady-state hot luminescence spectrum has been made.

Pulsewidth and interpulse jitter measurements of a passively mode-locked ring CW dye laser

Pulsewidth and jitter measurements have been carried out on a passively mode-locked Rhodamine 6G CW ring dye laser using the SHG autocorrelation technique and a synchroscan streak camera respectively. The pulse durations were measured to be ≈0.18 ps and the cumulative long-term jitter was deduced to be subpicosecond.

Simultaneous autocorrelation and synchroscan streak camera measurement of cavity length detuning effects in a synchronously pumped cw dye laser

The cavity matching condition for optimum stable, picosecond pulse generation in a synchronously pumped c.w. mode locked dye laser has been achieved with an accuracy of 2 μm using a synchronously operated streak camera exhibiting a modest temporal resolution of 9 ps. This was possible because of the observed distinct asymmetry of the pulses generated under conditions of cavity mismatch about the zero position. Simultaneous autocorrelation measurements confirmed the streak camera observations.