96,166 research outputs found
Green-pumped, picosecond MgO:PPLN optical parametric oscillator
We investigate the performance of a magnesium-oxide-doped periodically poled lithium niobate crystal (MgO:PPLN) in an optical parametric oscillator (OPO) synchronously-pumped by 530nm, 20ps, 230MHz pulses with an average power of up to 2W from a frequency-doubled, gain-switched laser diode seed and a multi-stage Yb:fiber amplifier system. The OPO produces ~165mW (signal, 845nm) and ~107mW (idler, 1421nm) of average power for ~1W of pump power and can be tuned from ~800nm to 900nm (signal) and 1.28µm to 1.54µm (idler). Observations of photo-refraction and green-induced infrared absorption (GRIIRA) in different operational regimes of the MgO:PPLN OPO are described and the role of peak intensity and average power are investigated, both with the aim to find the optimal operating regime for pulsed systems
Intensity Noise Optimization of a Mid-Infrared Frequency Comb Difference Frequency Generation Source
We experimentally demonstrate in a difference-frequency generation
mid-infrared frequency comb source the effect of temporal overlap between pump-
and signal- pulse to the relative intensity noise (RIN) of the idler pulse.
When scanning the temporal delay between our 130 fs long signal- and pump
pulses, we observe a RIN minimum with a 3 dB width of 20 fs delay and an RIN
increase of 20 dB in 40 fs delay at the edges of this minimum. We also
demonstrate active long-term stabilization of the mid-infrared frequency comb
source to the temporal overlap setting corresponding to the lowest RIN
operation point by an on-line RIN-detector and active feedback control of the
pump-signal- pulse delay. This active stabilization set-up allowed us to
dramatically increase the signal-to-noise ratio of mid-infrared absorption
spectra
Entangled photon apparatus for the undergraduate laboratory
We present detailed instructions for constructing and operating an apparatus
to produce and detect polarization-entangled photons. The source operates by
type-I spontaneous parametric downconversion in a two-crystal geometry. Photons
are detected in coincidence by single-photon counting modules and show strong
angular and polarization correlations. We observe more than 100 entangled
photon pairs per second. A test of a Bell inequality can be performed in an
afternoon.Comment: 6 pages, 9 figure
Multiple-octave spanning mid-IR supercontinuum generation in bulk quadratic nonlinear crystals
Bright and broadband coherent mid-IR radiation is important for exciting and
probing molecular vibrations. Using cascaded nonlinearities in conventional
quadratic nonlinear crystal like lithium niobate, self-defocusing near-IR
solitons have been demonstrated that led to very broadband supercontinuum
generation in the visible, near-IR and short-wavelength mid-IR. Here we conduct
an experiment where a mid-IR crystal pumped in the mid-IR gives multiple-octave
spanning supercontinua. The crystal is cut for noncritical interaction, so the
three-wave mixing of a single mid-IR femtosecond pump source leads to highly
phase-mismatched second-harmonic generation. This self-acting cascaded process
leads to the formation of a self-defocusing soliton at the mid-IR pump
wavelength and after the self-compression point multiple octave-spanning
supercontinua are observed (covering 1.6-m). The results were recorded
in a commercially available crystal LiInS pumped in the 3-m range,
but other mid-IR crystals can readily be used as well.Comment: submitted to APL Photonic
Generation and Direct Detection of Broadband Mesoscopic Polarization-Squeezed Vacuum
Using a traveling-wave OPA with two orthogonally oriented type-I BBO crystals
pumped by picosecond pulses, we generate vertically and horizontally polarized
squeezed vacuum states within a broad range of wavelengths and angles.
Depending on the phase between these states, fluctuations in one or another
Stokes parameters are suppressed below the shot-noise limit. Due to the large
number of photon pairs produced, no local oscillator is required, and 3dB
squeezing is observed by means of direct detection.Comment: 4 pages, 4 figures, submitted to PR
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