It's official: a physicist's laboratory is the coldest place in the universe. Physicists and physical chemists are finding that having the coldest place in the universe is becoming increasingly useful. Small collections of atoms or ions cooled to ultra-low temperatures provide the ideal laboratory for a wide variety of applications, including the study of fundamental physics, the development of sensors and ultra-precise time clocks and possibly the development of a future generation of supercomputers.
What is Bose-Einstein condensation
Bose-Einstein condensation describes the collapse of the atoms into a single quantum state. This phenomenon was predicted in the 1920's, and derived originally from Satyendra Bose's work on the statistical mechanics of photons, and subsequently formalized by Albert Einstein. Governed by the Bose-Einstein statistics, a Bose gas describes the statistical distribution of certain types of identical particles known as bosons. "Bosonic particles", are allowed to share quantum states with each other.
Einstein speculated that cooling bosonic atoms to a very low temperature, to beyond a "critical temperature" for the atom, would cause them to condense into the lowest available quantum state, resulting in a new wavelike form. In this state, a cloud of atoms will form a macroscopic quantum state in which all the atoms share the same space and have phase coherence in their wavefunctions.
Thus, as the value for momentum becomes more certain, the position of the atoms becomes more uncertain or (in quantum mechanical terms), the wavepacket that describes an individual atom becomes "delocalized".
As the atoms cool down, their kinetic energy and hence their momentum reduce. Heisenberg's uncertainty principle confirms this.
ΔxΔp ≥ h/2
Δx = the uncertainty in the measured value of position and Δp = the uncertainty in the measured value of a component of momentumh = reduced Planck constant
Laser cooling can reduce the temperatures of atoms to a few billionths of a degree above the coldest temperature it is possible to achieve: absolute zero Kelvin (-273.15°C). This environment created in the laboratory is even colder than the most remote regions of deep space, which are pervaded by cold microwave radiation - the afterglow of the big bang. So, advanced techniques are evolving to create, trap and manipulate such novel states - another challenge is to see them.
Andor Solutions for Bose Einstein Condensation
Andor high-performance CCD and Electron Multiplying CCD (EMCCD) camera solutions have been a key component to dedicated set-ups throughout the world, aimed at creating and detecting Bose Einstein Condensates.The challenging detection requirements associated with typical optical configurations for laser-cooling have been addressed though a number of particular operational modes of Andor cameras, including combinations of the following:
- EMCCD: rapid readout and flexible Electron Multiplication sensitivity, tuneable to single photon-counting levels
- Rapid charge "purging": crucial to eradicate bright signal, e.g. from magneto-optical traps, prior to absorption or fluorescence measurement.
- External Trigger: capture synchronous with probe laser pulse
- Fast Kinetics: sub-microsecond time resolution from industry fastest parallel shifts. Extensive storage area.
- Cropped Sensor: readout mode for continuous readout with fast time resolution
- Deep Depletion Devices: specialised sensors for higher Quantum Efficiency (QE) in near infra-red.
Some of these modes are described in more detail later in this section.
QE curves relevant to Bose Einstein
iXon EMCCD Camera Series
Andor's pioneering iXon EMCCD Camera Series is a revolutionary range of CCD cameras that provides single photon detection sensitivity, highest QE and -100°C Thermoelectric (TE) cooling at rapid frame rates, utilizing Andor's pioneering and award-winning EMCCD technology.
Features and Benefits of the iXonEM+ for BEC
Features and Benefits of the iXon EMCCD Camera Series for Bose-Einstein condensation include:
- Single photon sensitivity and high QE
- RealGain™: easily tune gain multiplication factor to balance signal amplification vs dynamic range
- Faster frame rates
- Minimized darkcurrent from unparalleled -100°C TE cooling
- Industry fastest parallel (vertical) shifts: sub µs time resolution is fast kinetics readout mode
- Charge purging: dump bright laser signal immediately prior to measurement
- Flexible external trigger modes: applicable to standard and fast kinetic readout modes
- Single photon counting capability from industry-leading minimization of dark noise events
iXon EMCCD Camera Series
- iXonEM+ DU-897: houses a 512 x 512 back illuminated sensor offering single photon sensitivity, > 90% QE, 16 x 16µm pixel size and -100°C TE cooling.
- iXonEM+ DU-885: houses a 1Mpixel sensor offering single photon sensitivity, > 60% QE, 8 x 8µm pixel size and -100°C cooling.
- iXonEM+ DU-860: houses a 128 x 128 back illuminated sensor offering single photon sensitivity, > 90% QE, 24 x 24µm pixel size and -100°C cooling @ 500 full frames/sec.
- iXonEM+ DU-888: houses a 1024 x 1024 back illuminated sensor offering unique photon sensitivity, > 90% QE, 13 x 13µm pixel size and -90°C cooling @ 2000 rows for fast operation
Back Illuminated vs Front Illuminated?
Whilst back illumination undoubtedly offers the highest QE across the entire spectral range, when imaging beyond 780nm, it is often prudent to potential consider etaloning effects of back illuminated sensors. The extent of the resulting fringing patterns can depend on optical factors such as the parallel nature of light impinging on the sensor and of the relative shot noise of the signal. The Virtual Phase (VP) front illuminated iXonEM+ DU-885 can be a popular choice to ensure that such fringing is completely eradicated from signals at such long probe wavelengths, whilst still maintaining relatively high QE across the entire wavelength range.Alternatively, if QE in the near IR is of utmost importance, Andor's back illuminated deep-depletion imaging CCD camera, the iKon-M DV-934-BRD offers 90% QE @ 780nm on a 1k x 1k imaging sensor format.
Andor's iKon-M CCD range offers affordable, yet unmatched sensitivity for slow scan astronomy. The iKon-M platform houses a range of full frame and frame transfer sensors, in both front-illuminated and back-illuminated (>90% QE) varieties.
For highest QE @ 780nm, we recommend the new line iKon-M DU-934N-BRD. Andor's BRD cameras are currently the only back-illuminated Deep Depletion sensors that incorporate Fringe Suppression Technology, to minimise etaloning/fringing effects. The 1024 x 1024 array boasts high resolution 13µm2 pixels. The system also benefits from negligible dark current with thermoelectric cooling down to -100°C, coupled with low readout noise of 2 to 3 electrons rms.
Features & Benefits of iKon-M for BEC
Features & Benefits of iKon-M for Bose-Einstein condensation include:
- 90% QE @ 780nm and low noise readout: detection of extremely weak signals with optimal S/N
- -100°C TE cooling for exceptionally low darkcurrent: especially necessary for extra silicon of DD sensors
- Ultra low-noise readout: intelligent low-noise electronics offer the most "silent" system noise performance available from these sensors.
- Software selectable readout speeds (up to 2.5MHz) - Faster readout for focusing, slower readout for absolute minimal noise performance acquisition.
- Fast kinetics mode operation available
- USB 2.0 connectivity: Plug and play. Long distance connection via USB Extender
EMCCD Special Readout Modes for Fastest Time Resolution
The absolute maximum time-resolution affordable from an EMCCD is available in this readout mode. Illustrated here for fast spectroscopy, fast kinetics can also be used for imaging at µs time resolution. Andor's EMCCDs have industry fastest parallel (vertical) shift speeds (sub µs available), and can be harnessed to optimal effect in this readout mode. In this configuration, the imaged area is focused onto a user-defined number of rows at the very top of the sensor. The "dark rows" beneath are subsequently used for storing the images shifted down from the exposed area, reaching time resolution down to 0.4µs/row.
A new unique feature enables the user to use signal accumulated in the exposed are also, provided the probe pulse can be rapidly switched off prior to readout, hence affording an extra image - this can be important if only dividing the entire image area into 4 segments. Vertical shift timings can be either driven by camera or by external trigger pulses.
Illustration of fast kinetics acquisition mode
In this mode, we can "fool" the sensor into thinking it is smaller than it actually is, and readout continuously at a much faster frame rate. For example, by focusing an image onto a 10 x 1000 area at the bottom of iXonEM+ DU-885at 35 MHz pixel readout, one can readout up to 3500 images/sec.
If your experiment dictates that you need fast time resolution but cannot be constrained by the storage size of the sensor, then it is possible to readout the EMCCD in a "cropped sensor" mode, as illustrated on the left.
Illustration of cropped sensor acquisition mode
Rapid Charge Purging in EMCCDs
It is a fundamental need of many atom-cooling experiments, to be able to "expel" light collected from bright "set-up" lasers, immediately prior to introduction of probe lasers.
With the iXonEM+ DU-885, Andor have adapted the anti-bloom structure inherent to the Texas Instruments frame transfer Impactron sensor, to "flush" charge from the sensor when not exposing. The time to switch to an exposure is in the order of a microsecond. The end of an exposure begins the shift of the image underneath the FT mask. This functionality has been extended to bulb mode acquisition. In bulb mode, the beginning and end of exposure is determined by the rising and falling edges of an external trigger. This trigger can be synchronized to coincide exactly with the probe pulse.
iXonEM+ DU-888 or DU-860
In iXonEM+ cameras housing L3 sensors from E2V, Andor have implemented a readout mode whereby unwanted charge (i.e. during cleaning cycles and sub-array selection) is purged straight from the serial (or "shift") register , therefore it is not readout through the EM gain register and amplifier electronics as the image pixels would.
Zyla 4.2 PLUS sCMOS Camera
Zyla 4.2 PLUS, the latest product in the Andor sCMOS camera portfolio, is based on the advanced generation sCMOS sensor technology. As a result, it can deliver an additional 10% boost in quantum efficiency (QE), which, in turn, leads to a remarkable 82% QEmax. The broad QE profile is highly optimized for a broad range of common fluorophores by providing superior coverage of the visible / NIR wavelength range, whereas the enhanced sensitivity enables faster frame rates and shorter exposure times with reduced phototoxicity.
The combination of excellent data transfer efficiency and Zyla’s unique 12-bit high-speed mode delivers a remarkable 53fps via the very convenient USB 3.0 interface, which is 77% faster than other commercially available sCMOS cameras. As a result, faster dynamic processes can be monitored effectively with better temporal resolution.
By choosing the Camera Link version, users can access up to a blistering 100fps (full resolution). The Zyla 4.2 PLUS also provides industry-leading linearity (99.8%) for unmatched quantitative accuracy of measurement over the entire dynamic range.
The Zyla 4.2 is suitable for applications demanding high level of sensitivity and speed, such as light sheet microscopy, calcium imaging, super-resolution microscopy, and many high-speed applications in the field of astronomy.
The latest application specific capabilities include LightScan PLUS with FlexiScan & CycleMax feature allow the Rolling Shutter scan mode to be adapted easily for applications such as line scan confocal and scanning lightsheet microscopy.
The Zyla 4.2 PLUS is also capable of outputting data at constant 26,041fps from a 2048(h) x 8(v) ROI, which is suitable for determining diffusion coefficients in fluorescence correlation spectroscopy.
The 4-transistor (‘4T’) design of the sensor pixel helps realize 82% QE by allowing additional photons to enter. The 4T design is basically a Rolling Shutter sensor. However, the implementation of a ‘global clear’ feature enables a simulated global exposure mode, which needs TTL communication between a pulsed light source and the camera, thereby mimicking the global shutter exposure condition.
The Andor GPU Express library has been developed to facilitate and optimize data transfers between the camera and a CUDA-enabled NVidia graphical processing unit (GPU) card for rapid GPU processing as part of the acquisition pipeline.
iXon Ultra 897 - Ultimate Sensitivity... Supercharged!
The iXon Ultra platform has undergone a fundamental redesign. It uses the well-established back-illuminated 512x512 frame transfer sensor and overclocks readout to 17MHz, thereby pushing speed performance to an exceptional 56fps (full frame) without compromising the quantitative stability throughout.
Deep thermoelectric cooling down to -100°C along with industry-lowest clock induced charge noise provides the platform with unprecedented sensitivity. Direct raw data access and USB 2.0 connectivity are the other innovative features of the iXon Ultra 897 that allow for on the fly processing. EMCCD and traditional CCD readout modes offer superior application flexibility, coupled with a ‘low and slow’ noise performance in CCD mode.
The iXon Ultra 897 provides unprecedented temporal resolution, thanks to the significant speed boost. Therefore, it is suitable for speed challenged low-light applications such as single molecule tracking, ion signaling, super-resolution microscopy, single photon counting, cell motility, lucky astronomy and adaptive optics.
The iXon Ultra 897’s very low noise and overclocked speed performance makes it an ideal platform for any laboratory planning to upgrade its high end imaging performance.
This information has been sourced, reviewed and adapted from materials provided by Andor Technology Ltd.
For more information on this source, please visit Andor Technology Ltd.