Midterm exam questions (October 15, 2012)
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What is a single photon source? How did you produce single photons in your Lab? Can you use a
single ion for single-photon source application?
What is the difference between photons from single photon sources and laser light attenuated to a
single photon level?
Why do single emitters emit single photons at a time?
Give the examples of different types of emitters for single photon sources.
What types of single photon counting detectors did you use in these labs? What material is used
for fabrication of these detectors? Do you know a spectral region of these detectors?
What are the main elements of a confocal microscope?
For what purpose do you need an oil-immersion objective? What is a role of the oil?
Can we image single molecule fluorescence with some other objective without oil immersion?
Are you using an EM-CCD-camera for imaging of several single emitters in a confocal
microscopy or in a conventional wide-field microscopy?
What is a numerical aperture of a microscope objective? Do you know a NA of our objective?
Does confocal microscope enhance a resolution? What are its advantages?
If you have a lens with a diameter 5 cm and with a focal length 20 cm, what is a spot size of a 633nm wavelength beam in a focus?
If you know the NA of the objective what would be a size of the focal spot? Calculate this size for
532 nm light and NA =1.3.
What is antibunching? What is the value of g (2) (0): (a) for antibunched light; (b) for classical
light; (c) for laser light attenuated to the single-photon level.
Make a sketch of a Hanbury Brown and Twiss interferometer. For what light was it used
initially?
Why do we use two detectors to measure time intervals between two consecutive photons? Can we
use only one detector for these measurements?
How can we define a zero point on the antibunching histogram? What electrical delay did we use
in one of the channels? In which channel did we put a delay?
What type of electrical pulses did you record on the oscilloscope from the output of y
our avalanche photodetector module?
What is a fluorescence lifetime? If a fluorescence lifetime is τ, how will a transition intensity
change in time?
Why do you have stripes in a quantum dot fluorescence in a confocal microscope?
What are photonic bandgap materials? What are photonic crystals? Provide some examples of
photonic bandgap materials. How do you think, is a multilayer dielectric mirror a photonic
crystal?
What type of liquid crystal should you take to obtain selective reflection?
Is it possible to obtain selective reflection with glassy oligomeric liquid crystal which is solid?
Describe the procedure for obtaining selective reflection from the liquid crystal layer.
What parameters of liquid crystal define the wavelength of a maximum of a selective reflection
band? What parameters of liquid crystal define the spectral bandwidth of a selective reflection
curve? Make a plot of a selective reflection curve of the liquid crystal sample that you prepared.