1 Dec. 17, 2012 Final Exam Labs 3-4 (1) 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? Will you have photon antibunching from idler photons in a parametric down conversion process? (2) What is the difference between photons from single photon sources and laser light attenuated to a single photon level? Can you obtain antibunching from the attenuated thermal light? (3) Why do you have stripes on a confocal fluorescence microscope image of several single quantum dots? (4) What type of microscopy do we use in imaging several single quantum dots by an EMCCD-camera? What improvement for such imaging can you offer? (5) Give the examples of different types of emitters for single photon sources. Do you know some single emitters which can fluoresce without bleaching? (6) Why do single emitters emit single photons at a time? (7) 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? (8) What are the main elements of a confocal fluorescence microscope? (9) What is the advantage of a confocal microscope? (10) Why do we use an oil-immersion objective? Can we image single molecule fluorescence with some other objective without oil immersion? (11) What is a NA of a microscope objective? Do you know a NA of our objective? (12) If you know the NA of the objective what would be a diameter of the focal spot? Calculate it for 532 nm light and NA =1.3. (13) 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; (d) for thermal light. (14) Make a sketch of a Hanbury Brown and Twiss interferometer. For what light was it used initially? (15) Why do we use two detectors to measure time intervals between two consecutive photons? (16) 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? (17) What type of electrical pulses did you record on the oscilloscope from the output of your avalanche photodetector module? 2 (18) If you have a lens with a focal distance f, beam diameter on the lens D, what will be spot diameter in the focus of this lens for laser wavelength λ? Provide the equation without the use of NA. If the medium has a refractive index n, what would be a beam diameter in this case? (19) What is a fluorescence lifetime? If a fluorescence lifetime is τ, how will a transition intensity change in time? (20) 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? (21) What type of liquid crystal should you take to obtain selective reflection? Is it possible to obtain selective reflection with glassy oligomeric liquid crystal? (22) Describe the fabrication procedure for obtaining selective reflection from the liquid crystal layer. (23) What parameters of liquid crystal are important to define (a) a wavelength of maximum of selective reflection band and (b) a spectral bandwidth of a selective reflection curve? Please, provide the equations. Make a plot of a selective reflection curve of the liquid crystal sample that you prepared. Lab 1 (24) What are the main components of a) entanglement set up and describe its main components. b) set up for observation of cones of down converted photons and describe its main components. (25) (a) Explain the difference between a half waveplate and a quarter waveplate. How do they change a polarization state of a linearly polarized beam? (b) To fabricate a waveplate how should you cut a birefringent crystal, with the optical axis in the plane of the waveplate (perpendicular to the beam propagation direction) or perpendicular to this plane? (c) If you place a quarter waveplate in a circular polarized beam, what polarization state will you obtain at its output? (d) What is circular polarized light? How to prepare it from linearly polarized light? (e) You need to rotate a linear polarization on the angle 10o. What waveplate should you select and how to use it? (f) You need to prepare a circular polarized light from linear polarization. What should you do? (g) What light polarization will you obtain if linear polarized light passes through a quarter waveplate with the optical axis fixed (i) in the direction of incident polarization and (ii) at the angle 36o? 3 (26) A signal beam at 1400 nm is generated by parametric down conversion using a pump beam of wavelength 800 nm. What is the wavelength of the idler beam? (27) Is it possible that for some angles the value of S in the CHSH Bell’s inequality will be the same for quantum mechanics and for classical case? What is the maximum value of S and minimum fringe visibility for polarization entanglement? (28) What is the optical axis of a crystal? What are ordinary and extraordinary beams? What is the fast axis of the crystal? If the beam’s propagation direction is along the optical axis, will you see splitting of the beam? Lab. 2. (29) How many photons/s with wavelength of 532 nm do you have at laser power of 10 mW? What should be a filter transmission value to attenuate a 10 mW, 532 nm laser beam to a single-photon level (e.g., for a ~ 100-m distance between photons)? (30) Explain wave-particle duality of photons in your experiments. (31) How did you align the interferometer? What types of interferometers do you know? (32) Explain what is a “which-way information”. Explain it on the example of your experiments. (33) Sketch the pattern in the case of bullets in a double slit experiment. (34) Calculate De Broglie wavelength for thermal electrons (300 K). kB = 1.38 x 10-23J/K, electron rest mass mo = 9.1 x 10-31 kg. (35) What were the slit’s width and slit’s separation in your Young’s double-slit experiment? Calculate the distance between interference maxima if an EM-CCD-camera detector is located at a distance 30 cm from the slits’ screen. (36) What lasers did you use in both entanglement experiments? What are wavelengths and the powers of these lasers? (37) You have a 633-nm laser beam with a 10 μW power focused to the area of the camera ~ 2 mm x 2 mm, with an EMCCD-camera exposure time 10 μs. Camera pixel size is 16 μm x 16 μm. What should be filter transmission value to attenuate this beam to the level of single photon/pixel for such exposure time? (38) What are the main sources of noise for ordinary CCD camera and for cooled, EM-CCD camera? In what case the ordinary CCD camera has an advantage over the EM-CCD camera?