Single-photon counting modules

As an example the EG and G SPCM single photon counting modules. 

Becker Hickl GmbH, SPC-134 through SPC-830 time-correlated single photon counting modules, application manual, www.becker-hickl.com (2004)... 

Perkin Elmer Optoelectronics, Single photon counting module, SPCM-AQR series, www.perkinelmer.com... 

Fig. 14 Typical time course of the fluorescence intensity of single Cy3 molecules. The fluorescence intensity was measured with an avalanche photodiode single photon counting module (SPCM-AQR-16, Perkin Elmer, Canada). Excitation wavelength, 514.5 nm. Sampling interval, 30 ms...

The type of laser source that can be used is exactly the same as for single-photon counting pulse fluorometry (see above). Such a laser system, which delivers pulses in the picosecond range with a repetition rate of a few MHz can be considered as an intrinsically modulated source. The harmonic content of the pulse train - which depends on the width of the pulses (as illustrated in Figure 6.11) - extends to several gigahertz. 

The well-defined statistics in single-photon counting is an advantage for data analysis. In phase fluorometry, the evaluation of the standard deviation of phase shift and modulation ratio may not be easy. 

Abbreviations BSA, bovine serum albumin PBS, phosphate buffered saline PMFS, phase-modulation fluorescence spectroscopy TCSPC, lime-correlated single photon counting. 

The time-correlated single photon counting electronics incorporate ORTEC modules including a 454 timing filter amplifier,... 

The excitation dichroism of the electric field modulated fluorescence yield was measured in a single photon counting fluorimeter in orthogonal geometry as described in [11]. The intensity of the exciting light was < 250 /iW/cm, corresponding to 0.2-1.0 turnovers/sec. RCs of Rb.sphaeroides R 26 obtained by modified standard procedures were imbedded in PVA,... 

Fig.11.6a,b. Observed output pulses from an argon laser at X = 488 nm, actively mode locked by an acousto-optic modulator, (a) Detected with a fast photodiode and a sampling oscilloscope, (b) detected by single-photon counting technique using a photomultiplier. The oscillations following the optical pulse in (a) are due to cable reflections of the electric output signal from the diode. The pulse width in (b) is limited by electron transit time variations in the photomultiplier [11.10]... 

Two time-resolved fluorescence techniques, pulse Jluorimetry and phase-modulation fluorimetjy, are commonly employed to recover the lifetimes. The former uses a short exciting pulse (from femtoseconds to nanoseconds) of light, which leads to the pulsed response of the sample, which should then be deconvolved from the instrument response. In phase-modulation fluorimetry, the intensity of light used for excitation is modulated at a frequency whose reciprocal is similar to the fluorescence decay time. The sample response is also modulated, but with a time delay, measured as phase shift, from which the emission decay time can be calculated. Thus, the first technique works in the time domain, while the second one in the frequency domain. The most widely used technique in the time domain is the time-correlated single-photon counting [10, 11]. The merits of both techniques have been extensively discussed [12]. 

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