Streak Camera Measurements Research Articles

A Low Time-Dispersion Refractive Optical Transmission Line for Streak Camera Measurements

A Low Time-Dispersion Refractive Optical Transmission Line for Streak Camera Measurements

Time-resolved fluorescence methods (IUPAC Technical Report)

Abstract This IUPAC Technical Report describes and compares the currently applied methods for measuring and analyzing time-resolved fluorescence traces using phase-modulation fluorometry as well as pulse fluorometry (direct emission decay measurements, single-photon timing, streak camera measurements, fluorescence upconversion, and optical Kerr gating). The paper starts with a brief description of the basic principles for time and frequency domain fluorescence spectroscopy. The fundamental equations are given, and recommendations for adequate use are emphasized. The up-to-date, commonly employed excitation sources and photodetectors are described in detail. The analysis of time-resolved fluorescence data is discussed. Attention is paid to possible artifacts, and remedies are presented on how to avoid them or to account for them. Finally, fluorescence lifetime standards for the nanosecond and picosecond timescales are collected.

Oscillatory solitons and time-resolved phase locking of two polariton condensates

When pumped nonresonantly, semiconductor microcavity polaritons form Bose–Einstein condensates that can be manipulated optically. Using tightly-focused excitation spots, radially expanding condensates can be formed in close proximity. Using high time resolution streak camera measurements we study the time dependent properties of these macroscopic coherent states. By coupling this method with interferometry we observe directly the phase locking of two independent condensates in time, showing the effect of polariton–polariton interactions. We also directly observe fast spontaneous soliton-like oscillations of the polariton cloud trapped between the pump spots, which can be either dark or bright solitons. This transition from dark to bright is a consequence of the change of sign of the nonlinearity which we propose is due to the shape of the polariton dispersion leading to either positive or negative polariton effective mass.

Gain-switching dynamics in optically pumped single-mode InGaN vertical-cavity surface-emitting lasers

The gain-switching dynamics of single-mode pulses were studied in blue InGaN multiple-quantum-well vertical-cavity surface-emitting lasers (VCSELs) through impulsive optical pumping. We measured the shortest single-mode pulses of 6.0 ps in width with a method of up-conversion, and also obtained the pulse width and the delay time as functions of pump powers from streak-camera measurements. Single-mode rate-equation calculations quantitatively and consistently explained the observed data. The calculations indicated that the pulse width in the present VCSELs was mostly limited by modal gain, and suggested that subpicosecond pulses should be possible within feasible device parameters.

Evolution of multi-mode operation in vertical-external-cavity surface-emitting lasers

The longitudinal multi-mode emission in a vertical-external-cavity surface-emitting laser is investigated using both single shot streak camera measurements and interferometric measurement techniques. For this, the laser is operated in the single- and two-color emission regime using both an etalon and a free-running configuration without etalon, respectively. The laser emission is analyzed with respect to pump power and output coupling losses for a long and for a short resonator. We observe a steep increase of emission bandwidth close to the laser threshold and monitor the transition between longitudinal single- and multi-mode operation. Additionally, the results indicate that a stable two-color operation is related to a sufficiently high number of oscillating longitudinal modes within each color.

In situ spectroscopy of high-power vertical-external-cavity surface-emitting lasers

Spectroscopic techniques for an in situ analysis of vertical-external-cavity surface-emitting lasers are presented and exemplary results are discussed. Spatially resolved photoluminescence is shown to provide access to the temperature distribution inside the active area of the laser chip. Both the shape and the size of the pump spot are found to strongly influence the thermal properties and the output power of the device. In addition, the temporal stability of a laser emitting at two distinct wavelengths is studied using single-shot streak-camera measurements. The collected data is evaluated via quantitative statistical analysis schemes identifying stable and unstable regimes of operation.

Current Status of Short X-ray Pulse Generation with a Vertical Kicker in the SPring-8 Storage Ring

From 2008, we have developed a scheme of short X-ray pulse generation by head-tail oscillation with a vertical kicker in SPring-8 storage ring in order to fulfill the demand of shorter pulse undulator radiation for the time resolved experiment. The developed system generates a vertical kick of 0.143 mrad and pulse width as short as 2.4 μs with 200 Hz repetition. With this system we successfully observed a bunch profile which tilted 362 mrad by visible light streak camera measurement for bending magnet light source. The expected tilt angle on the undulator position is 163 mrad, whose tilt angle has a capability of generating the 630 fs (RMS) without the beam spread effect after 50 μm slitting. As a preliminary test, we observed the reduction of the X-ray pulse duration as a function of the tilt angle by X-ray streak camera for the undulator radiation. From this result, we observed the saturation of the minimum short pulse duration at 4.5±2.1 ps (RMS) by 50 μm slitting, which almost corresponds to the detection limit of the X-ray streak camera, in the tilt angle region larger than 40 mrad.

Nearly Temperature‐Independent Threshold for Amplified Spontaneous Emission in Colloidal CdSe/CdS Quantum Dot‐in‐Rods

Nearly Temperature‐Independent Threshold for Amplified Spontaneous Emission in Colloidal CdSe/CdS Quantum Dot‐in‐Rods

Single-laser shot fluorescence lifetime imaging on the nanosecond timescale using a Dual Image and Modeling Evaluation algorithm

A novel technique, designated dual imaging and modeling evaluation (DIME), for evaluating single-laser shot fluorescence lifetimes is presented. The technique is experimentally verified in a generic gas mixing experiment to provide a clear demonstration of the rapidness and sensitivity of the detector scheme. Single-laser shot fluorescence lifetimes of roughly 800 ps with a standard deviation of ~120 ps were determined. These results were compared to streak camera measurements. Furthermore, a general fluorescence lifetime determination algorithm is proposed. The evaluation algorithm has an analytic, linear relationship between the fluorescence lifetime and detector signal ratio. In combination with the DIME detector scheme, it is a faster, more accurate and more sensitive approach for rapid fluorescence lifetime imaging than previously proposed techniques. Monte Carlo simulations were conducted to analyze the sensitivity of the detector scheme as well as to compare the proposed evaluation algorithm to previously presented rapid lifetime determination algorithms.

Time-dynamics of the two-color emission from vertical-external-cavity surface-emitting lasers

The temporal stability of a two-color vertical-external-cavity surface-emitting laser is studied using single-shot streak-camera measurements. The collected data is evaluated via quantitative statistical analysis schemes. Dynamically stable and unstable regions for the two-color operation are identified and the dependence on the pump conditions is analyzed.

Measuring the bunch frequency multiplication at the 3rd CLIC Test Facility

The CLIC Test Facility 3 (CTF3) is being built and commissioned by an international collaboration to test the feasibility of the proposed Compact Linear Collider (CLIC) drive beam generation scheme. Central to this scheme is the use of RF deflectors to inject bunches into a delay loop and a combiner ring, in order to transform the initial bunch frequency of 1.5 GHz from the linac to a final bunch frequency of 12 GHz. To do so, the machine's transverse optics must be tuned to ensure beam isochronicity and each ring's length can finally be adjusted with wiggler magnets to a sub millimeter path length accuracy. Diagnostics based on optical streak camera and RF power measurements, in particular frequency bands, have been designed to measure the longitudinal behaviour of the beam during the combination. This paper presents the diagnostics and recent commissioning measurements.

2-ps Hard X-Ray Streak Camera Measurements at Sector 7 Beamline of the Advanced Photon Source

A hard X-ray streak camera capable of 2-ps time resolution is in operation at the Sector 7 beamline of the Advanced Photon Source. It is used for laser-pump, X-ray probe experiments using the Ti:Sapphire femtosecond laser system installed on the beamline. This streak camera, combined with standardized and prealigned experimental setups, can perform time-resolved liquid-phase absorption spectroscopy, reflectivity, and diffraction experiments.

Organic light-emitting diodes under high currents explored by transient electroluminescence on the nanosecond scale

We investigate organic light-emitting diodes (OLEDs) comprising the singlet emitter system 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) doped into aluminium tris(8-hydro-xyquinoline) (Alq${}_{3}$) at high excitation densities. With the OLED active area reduced to $100\ifmmode\times\else\texttimes\fi{}100\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}$m${}^{2}$, current densities up to 800 A/cm${}^{2}$ are achieved in pulsed operation. These devices exhibit an intense electroluminescence (EL) turn-on peak on the nanosecond time scale. With the help of streak camera measurements, we prove that the steady state EL of the fluorescent OLEDs is reduced due to singlet-triplet quenching. We demonstrate that short electrical pulses with a rise time of 10 ns make the separation of singlet emission and singlet-triplet quenching in time domain possible. By modeling the singlet and triplet population dynamics in the emission layer, we find that the triplet-triplet annihilation-rate coefficient in doped fluorescent materials is triplet-density dependent at high excitation density. The increased triplet lifetime usually observed in host:guest systems due to triplet trapping on guest molecules vanishes at high current densities. An increase in current density leads to an increased triplet-triplet annihilation rate, while the triplet density in the emission layer stays constant.

Exploration of the Correlation between Solvation Dynamics and Internal Dynamics of a Protein

Protein function is intimately related to the dynamics of the protein as well as to the dynamics of the solvent shell around the protein. Although it has been argued extensively that protein dynamics is slaved to solvent dynamics, experimental support for this hypothesis is scanty. In this study, measurements of fluorescence anisotropy decay kinetics have been used to determine the motional dynamics of the fluorophore acrylodan linked to several locations in a small protein barstar in its various structural forms, including the native and unfolded states as well as the acid and protofibril forms. Fluorescence upconversion and streak camera measurements have been used to determine the solvation dynamics around the fluorophore. Both the motional dynamics and solvent dynamics were found to be dependent upon the location of the probe as well as on the structural form of the protein. While the (internal) motional dynamics of the fluorophore occur in the 0.1-3 ns time domain, the observed mean solvent relaxation times are in the range of 20-300 ps. A strong positive correlation between these two dynamical modes was found in spite of the significant difference in their time scales. This observed correlation is a strong indicator of the coupling between solvent dynamics and the dynamics in the protein.

Experimental analysis and modelling of positive streamer in air: towards an estimation of O and N radical production

This paper is mainly devoted to the comparison between the calculation and experimental results of primary and secondary streamer development in a point-to-plane positive corona discharge in dry air at atmospheric pressure. The qualitative agreement between experimental and calculation results based on the hydrodynamics approximation shows that the O radical is mainly produced in the secondary streamer which is in good agreement with the recent literature measurements using TALIF diagnostics. However, the O radical production yield (in terms of radicals produced per energy injected) is more efficient in the primary streamer than in the secondary one. The main positive corona discharge characteristics are revisited using fast electrical and optical ICCD and streak camera measurements. The calculation shows two streamer radii of, respectively, 10 µm (associated with the radial extension of a high electron density region) and 200 µm (corresponding to the extension of the radial space charge electric field).

Time- and space-resolved dynamics of melting, ablation, and solidification phenomena induced by femtosecond laser pulses in germanium

Femtosecond time-resolved microscopy has been used to analyze the structural transformation dynamics (melting, ablation, and solidification phenomena) induced by intense $130\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ laser pulses in single-crystalline (100)-germanium wafers on a time scale from $\ensuremath{\sim}100\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ up to $10\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$. Complementary information on longer time scales $(350\phantom{\rule{0.3em}{0ex}}\mathrm{ps}--1.4\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s})$ has been obtained by means of simultaneous streak camera and photodiode measurements of the sample surface reflectivity. In the ablative regime, transient surface reflectivity patterns are observed by fs microscopy on a ps to ns time scale as a consequence of the complex spatial density structure of the ablating material. Complementing point-probing streak camera measurements allow one to characterize the temporal evolution in real time up to $40\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$ after the fs-laser pulse excitation. Fs microscopy reveals additional reflectivity patterns for fluences below the ablation threshold of the germanium. It is shown that these patterns are originating from the selective removal of the native oxide layer at the wafer surface within a certain fluence range. After solidification, and in contrast to other semiconductors, surface amorphization has not been observed in (100)-germanium upon femtosecond laser pulse irradiation in the studied fluence range.

Pulse duration measurements of grazing-incidence-pumped high repetition rate Ni-like Ag and Cd transient soft x-ray lasers

We have measured the pulse duration of gain-saturated 13.9 nm Ni-like Ag and 13.2 nm Ni-like Cd transient collisional lasers excited by grazing-incidence-pumping for several pumping conditions. High-resolution streak-camera measurements yielded FWHM pulse durations close to 5 ps for both lasers under optimum pumping conditions. The very high brightness and short pulse duration of these new high repetition tabletop soft x-ray lasers make them an attractive source for dynamic applications.

Ultrafast photonic-crystal fiber light flash for streak-camera fluorescence measurements

Photonic-crystal fibers (PCFs) provide a high efficiency of frequency upconversion of femtosecond Cr: forsterite laser pulses through the emission of dispersive waves by solitons and third-harmonic generation. Dispersion management allows the central wavelength of the frequency-upconverted signal in PCF output to be tuned within the range of wavelengths from 400 to 900 nm. PCF frequency shifters are employed as excitation sources for time-resolved fluorescence streak-camera measurements on fluorescein solution.

The oscillator strength of extended exciton states and possibility for very fast scintillators

Streak camera measurements of luminescence from ZnO single crystals as a function of temperature show that the spontaneous radiative lifetime of the “free exciton” band at 380nm is 440ps at room temperature, decreasing to 290ps at 85K. The donor-bound exciton lifetime is 50ps from 85K down to 16K, the lowest temperature we measured. This is significantly faster than is consistent with the dipole matrix element of any single atom transition scaled to the same wavelength. We discuss the oscillator strength of extended exciton states based on the theory of defect-bound excitons, and examine its limit for free excitons. In that regard, we ask what physically limits the coherent dipole size and how a material might be engineered for “giant” exciton oscillator strength. The phenomenon applies to single excitons, not just coherently produced multiple excitations.

A Constant‐Density Gurney Approach to the Cylinder Test

AbstractThe previous analysis of the Cylinder test required the treatment of different wall thicknesses and wall materials separately. To fix this, the Gurney analysis is used, but this results in low values for full‐wall standard, ideal explosives relative to CHEETAH analyses. A new constant metal‐density model is suggested, which takes account of the thinning metal wall as the cylinder expands. With this model, the inner radius of the metal cylinder moves faster than the measured outer radius. Additional small corrections occur in all cylinders because of energy trapped in the copper walls. Also, the half‐wall cylinders have a small correction because the relative volumes of the gas products are smaller at a given outside wall displacement. The Fabry‐Perot and streak camera measurements are compared. The Fabry method is shown to equate to the constant density model.