143 research outputs found
Investigation of coherent sources of infrared radiation Semiannual status report, 1 Nov. 1967 - 30 Apr. 1968
Refractive effects in gaseous infrared Q switched laser
Investigation of coherent sources of infrared radiation Semiannual status report, 1 May - 31 Oct. 1967
Appleton-Hartree equations for propagation of electromagnetic waves collisionless magnetoionic medium to determine effect of electron density on laser behavio
Direct measurement of xenon flashtube opacity
Opacity measurement of xenon flash tube - optical mase
Three-photon-excited fluorescence detection of atomic hydrogen in an atmospheric-pressure flame
By using three-photon excitation at 291.7 nm of the n 4 hydrogen level and observing Balmer- radiation at 486.1 nm, hydrogen atoms in an atmospheric C2H2/O2 flame have been detected. Other schemes for hydrogen detection were also tried, and the results are discussed
Phonon induced relaxation in excited optical states of trivalent praseodymium in laf3
Phonon induced relaxation in excited optical states of trivalent praseodymium in lanthanum fluorid
High-contrast Doppler-free transmission spectroscopy
By applying Doppler-free saturated absorption spectroscopy in the regime of high integrated sample absorption, high-contrast Doppler-free laser transmission signals can be obtained as demonstrated in experiments on the sodium D lines. Natural linewidth background-free signals are observed
Laser spectroscopy using beam-overlap modulation
A new Doppler-free laser spectroscopy method is demonstrated that employs modulation of the position of a laser beam rather than the commonly used intensity or polarization modulation. The technique is applicable in saturated absorption as well as fluorescence measurements, as is illustrated in experiments on sodium and iodine lines. A particular feature of the method is that Doppler- and background-free fluorescence spectra can be recorded without using intermodulation techniques
Active laser frequency stabilization using neutral praseodymium (Pr)
We present a new possibility for the active frequency stabilization of a
laser using transitions in neutral praseodymium. Because of its five outer
electrons, this element shows a high density of energy levels leading to an
extremely line-rich excitation spectrum with more than 25000 known spectral
lines ranging from the UV to the infrared. We demonstrate the active frequency
stabilization of a diode laser on several praseodymium lines between 1105 and
1123 nm. The excitation signals were recorded in a hollow cathode lamp and
observed via laser-induced fluorescence. These signals are strong enough to
lock the diode laser onto most of the lines by using standard laser locking
techniques. In this way, the frequency drifts of the unlocked laser of more
than 30 MHz/h were eliminated and the laser frequency stabilized to within
1.4(1) MHz for averaging times >0.2 s. Frequency quadrupling the stabilized
diode laser can produce frequency-stable UV-light in the range from 276 to 281
nm. In particular, using a strong hyperfine component of the praseodymium
excitation line E = 16 502.616_7/2 cm^-1 -> E' = 25 442.742_9/2 cm^-1 at lambda
= 1118.5397(4) nm makes it possible - after frequency quadruplication - to
produce laser radiation at lambda/4 = 279.6349(1) nm, which can be used to
excite the D2 line in Mg^+.Comment: 10 pages, 14 figure
Decoherence of Bose-Einstein condensates in traps at finite temperature
The phase diffusion of the order parameter of trapped Bose-Einstein
condensates at temperatures large compared to the mean trap frequency is
determined, which gives the fundamental limit of the line-width of an atom
laser. In addition a prediction of the correlation time of the number
fluctuations in the condensate is made and related to the phase diffusion via
the fluctuation-dissipation relation.Comment: 4 pages Revtex, revised version, to appear in Phys. Rev. Letter
Continuous-wave room-temperature diamond maser
The maser, older sibling of the laser, has been confined to relative
obscurity due to its reliance on cryogenic refrigeration and high-vacuum
systems. Despite this it has found application in deep-space communications and
radio astronomy due to its unparalleled performance as a low-noise amplifier
and oscillator. The recent demonstration of a room-temperature solid- state
maser exploiting photo-excited triplet states in organic pentacene molecules
paves the way for a new class of maser that could find applications in
medicine, security and sensing, taking advantage of its sensitivity and low
noise. However, to date, only pulsed operation has been observed in this
system. Furthermore, organic maser molecules have poor thermal and mechanical
properties, and their triplet sub-level decay rates make continuous emission
challenging: alternative materials are therefore required. Therefore, inorganic
materials containing spin-defects such as diamond and silicon carbide have been
proposed. Here we report a continuous-wave (CW) room-temperature maser
oscillator using optically pumped charged nitrogen-vacancy (NV) defect centres
in diamond. This demonstration unlocks the potential of room-temperature
solid-state masers for use in a new generation of microwave devices.Comment: 7 pages, 4 figure
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