Edinburgh Photonics, a division of Edinburgh Instruments, has designed a compact, high performance fluorescence lifetime spectrometer called LifeSpec II.
Designed for use with high repetition rate pulsed sources, such as femtosecond Ti:Sapphire lasers and picosecond pulsed lasers, this fully integrated system has zero temporal dispersion optics which sets the benchmark for measuring ultra-fast decays.
The LifeSpec II is a fully automated solution and combines software and hardware in a single package for basic research and routine laboratory applications.
Time Correlated Single Photon Counting
Figure 1. LifeSpec II spectrometer.
The LifeSpec II includes a subtractive double monochromator, enabling it to measure fluorescence lifetimes down to 5 - 10 ps. LifeSpec II uses the Time Correlated Single Photon Counting (TCSPC) technique for precise measurements of fluorescence lifetimes.
In the standard configuration, the LifeSpec II is available with a single detector. The system can be upgraded with additional detectors, if required. For operation, the system requires at least one pulsed LED, picosecond pulsed diode laser, Ti:Sapphire laser, or supercontinuum laser.
Figure 2. Complete software package for data acquisition and lifetime data analysis.
Sophisticated software analyses the raw data and controls all the hardware. By applying numerical reconvolution, the software can calculate fluorescence lifetimes down to 1/10th of the instrument response function.
Users can view their profiles live on screen and can manipulate and analyze data across the UV/Vis/NIR spectral range. Data acquisition modes range from time-resolved spectra and fluorescence decay through to temperature maps and automated time- resolved anisotropy measurements.
The LifeSpec II features a huge sample chamber that accommodates a wide range of sample holders. These comprise cryostats, thermostated sample holders, front face film/bulk/powder holders, single cuvette holders, multiple sample holders and fibre attachments.
In order to realize accurate measurements in the lower picosecond time scale, zero temporal dispersion in the optical path is important. Pulse broadening and temporal shifts, which arise from propagation delays caused by grating’s dimensions, are often introduced by traditional monochromators.
The newly designed LifeSpec II spectrometer utilizes a subtractive double monochromator with opposite pulse broadening characteristics. This helps in removing temporal dispersion and temporal delays and improves the stray light rejection. Thus lifetime measurements can be carried out and studied more precisely, and sources of errors in the response of the instrument are reduced to a great extent.
Computer Controlled Polarizers
To operate the Glan Thompson polarizers, motorized mounts are utilized in the excitation beam path as well as in the emission path.
If the laser's emission is naturally polarized, then an excitation polarizer may not be required as in the case of picosecond-pulsed diode and Ti:Sapphire lasers. Nevertheless, for accurate fluorescence decays, polarizers may be needed to remove rotational artifacts that tend to be superimposed on the fluorescence decay.
Principal Layout of LifeSpec II Spectrometer
A typical LifeSpec II spectrometer includes the optical spectrometer, a PC equipped with TCC900 data acquisition card, and a power supply module. However, additional sources like detectors, fiber optics, polarizers and sample cooling stages can be included in the system.
The main unit of the LifeSpec II can be adjusted so that the optical plane can be set to between 130 to 180 mm from the table top, thus simplifying beam steering and merging of external laser systems to the instrument.
Figure 3. Layout of LifeSpec II spectrometer.
Detectors and Light Sources
The LifeSpec II is compatible with LEDS, picosecond pulsed diode lasers, femtosecond Ti:Sapphire lasers, supercontinuum "white" picosecond pulsed lasers, and other high repetition rate pulsed sources. The LifeSpec II spectrometer is supplied with an adjustable receptor flange for the UV-LEDs (EPLED Series) and picosecond pulsed diode lasers (EPL Series).
The shortest measurable lifetime depends on the pulse width of the picosecond pulsed light source and on the speed of the detector. With reconvolution, lifetimes down to 1/10th of the instrument response function can be obtained from the data, enabling the LifeSpec II to cover the spectral range from 5 ps to 50 µs.
The LifeSpec II is a high performance fluorescence lifetime spectrometer and is compatible with TCSPC methods. The system allows real-time direct measurement, enables digital counting to reduce background noise, and also helps in acquiring short and long lifetimes from a single measurement.
Equipped with a subtractive double monochromator, the LifeSpec II offers spectral resolution and simultaneously removes the effect of temporal dispersion which prevents precise lifetime measurements in the lower picosecond time range.
This information has been sourced, reviewed and adapted from materials provided by Edinburgh Instruments.
For more information on this source, please visit Edinburgh Instruments.