217 research outputs found
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
Sub-Pikosekunden-Spektroskopie der Schwingungsrelaxion von C-H-Streckschwingungen in polyatomaren Molekülen
Ultrahigh resolution optical coherence tomography using a superluminescent light source
A superluminescent Ti:Al2O3 crystal is demonstrated as a light source for ultrahigh resolution optical coherence tomography (OCT). Single spatial mode, fiber coupled output powers of ~40 μW can be generated with 138 nm bandwidth using a 5 W frequency doubled, diode pumped laser, pumping a thin Ti:Al2O3 crystal. Ultrahigh resolution OCT imaging is demonstrated with 2.2 μm axial resolution in air, or 1.7 μm in tissue, with >86 dB sensitivity. This light source provides a simple and robust alternative to femtosecond lasers for ultrahigh resolution OCT imaging
Widely-tunable mid-IR frequency comb source based on difference frequency generation
We report on a mid-infrared frequency comb source of unprecedented tunability
covering the entire 3-10 {\mu}m molecular fingerprint region. The system is
based on difference frequency generation in a GaSe crystal pumped by a 151 MHz
Yb:fiber frequency comb. The process was seeded with Raman shifted solitons
generated in a highly nonlinear suspended-core fiber with the same source.
Average powers up to 1.5 mW were achieved at 4.7 {\mu}m wavelength.Comment: 3 pages, 3 figure
Transverse and longitudinal characterization of electron beams using interaction with optical near-fields
We demonstrate an experimental technique for both transverse and longitudinal
characterization of bunched femtosecond free electron beams. The operation
principle is based on monitoring of the current of electrons that obtained an
energy gain during the interaction with the synchronized optical near-field
wave excited by femtosecond laser pulses. The synchronous
accelerating/decelerating fields confined to the surface of a silicon
nanostructure are characterized using a highly focused sub-relativistic
electron beam. Here the transverse spatial resolution of 450 nm and femtosecond
temporal resolution achievable by this technique are demonstrated
Self-broadening and self-shift in the band of ammonia from mid-infrared-frequency-comb spectroscopy
We report the broadband absorption spectrum of the band of
NH near 4 . The data were recorded using a mid-infrared
frequency comb coupled to a homebuilt Fourier-transform spectrometer with a
resolution of 0.00501 . Line positions, line intensities,
self-broadening, and self-shift parameters for six rovibrational lines were
determined at room temperature ( K). Comparison with HITRAN 2016 shows
good agreement at improved precision. The high precision and the rapid
tunability of our experiment enables advanced fast spectroscopy of molecular
gases
Phase-stabilized, 1.5-W frequency comb at 2.8 to 4.8 micron
We present a high-power optical parametric oscillator-based frequency comb in
the mid-infrared wavelength region using periodically poled lithium niobate.
The system is synchronously pumped by a 10-W femtosecond Yb:fiber laser
centered at 1.07 um and is singly resonant for the signal. The idler (signal)
wavelength can be continuously tuned from 2.8 to 4.8 um (1.76 to 1.37 um) with
a simultaneous bandwidth as high as 0.3 um and a maximum average idler output
power of 1.50 W. We also demonstrate the performance of the stabilized comb by
recording the heterodyne beat with a narrow-linewidth diode laser. This OPO is
an ideal source for frequency comb spectroscopy in the mid-IR.Comment: 4 figure
Octave-spanning ultrafast OPO with 2.6-6.1µm instantaneous bandwidth pumped by femtosecond Tm-fiber laser
We report the extension of broadband degenerate OPO operation further into mid-infrared. A femtosecond thulium fiber laser with output centered at 2050 nm synchronously pumps a 500-μm-long crystal of orientation patterned GaAs providing broadband gain centered at 4.1 µm. We observe a pump threshold of 17 mW and output bandwidth extending from 2.6 to 6.1 µm at the −30 dB level. Average output power was 37 mW. Appropriate resonator group dispersion is a key factor for achieving degenerate operation with instantaneously broad bandwidth. The output spectrum is very sensitive to absorption and dispersion introduced by molecular species inside the OPO cavity
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