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We report on fabrication of high-Q (i.e., a quarter million) lithium niobate whispering-gallery-mode microresonators using femtosecond laser micromachining. Second harmonic generation with a normalized conversion efficiency of 1.35×10−5/mW has been experimentally demonstrated.
The geometry dependence of the absorption in semiconductor nanowires is of large interest currently, and especially the diameter-dependent absorption resonances are promising for tunable detectors. Here, we show that these resonances for both wurtzite and zincblende GaP nanowires can be tuned down to λ ∼ 330 nm by decreasing the diameter to 35 nm. This stop of the shifting at λ ∼ 330 nm indicates...
We have compared the radiation resistance of various Er3+-doped fiber preforms manufactured with different technologies: Si and Al nanoparticles doped fibers, and standard MCVD fibers. All of them have been irradiated with a total gamma dose of 5.9 kGy and then studied using absorption and EPR spectroscopies.
Laser filamentation provides a convenient source of broadband, intrinsically short radiation that is an ideal source for impulsive vibrational and rotational excitation of polyatomic molecules. Here we present experimental and theoretical results achieved to date.
We present techniques for measuring the damage performance of a variety of optical components with ps laser pulses, introduce a novel beam diagnostic technique, and explore the sensitivity of damage resistance to laser spot size for the case of high-reflectivity, multilayer dielectric (MLD) mirrors.
We observe a 3-fold increase in the electron density within 30 picoseconds after the filamentary propagation of femtosecond pulses in 60-bar argon gases. This suggests that electron-impact ionization dominates on this time scale.
We report recent progress on the J-KAREN laser upgrade to realize 1022 W/cm2 intensity at 0.1 Hz. Our current high-spatiotemporal-quality broadband pulses of over 20 J will be further amplified in the final amplifier.
We demonstrate significant thermo-optic degradation of single-modedness in active large mode area fibers due to heat generation in the fiber. We propose and demonstrate through simulations, simple compensation mechanisms using custom length dependent fiber coiling.
We describe a 100 mJ three component ytterbium based laser system operating at 1030 nm. Capabilities of both temporal pulse shaping and efficient active/passive spatial shaping for amplification in a 100 J system are incorporated.
The nonlinear absorption was studied for compounds linking tricycloquinazoline to a number of iridium groups. It was determined that the excited-state cross section was highest for the compound with a single iridium group.
We demonstrated 0.9 mJ terahertz pulses by optical rectification of a high-energy Cr:Mg2SiO4 laser in large organic crystal. The emitted spectrum covers 0.1–5 THz and the peak fields exceed 42 MV/cm and 14 Tesla.
By carefully designing diagonal transitions in the active region, we present a broadband mid-infrared quantum cascade detector with photocurrent ranging from 3.9 to 9.6 μm, more than 2 times broader than stacked designs.
We report on a record 2% extracted optical-to-terahertz conversion efficiency in the mm-wavelength range through optical rectification in cryogenically-cooled lithium niobate by exploiting spatial and temporal shaping of the optical pump beam.
We present the characterization of minority carrier diffusion length and surface recombination velocity, as well as vertical diffusivity and mobility by performing an electron beam induced current measurement in addition to an optical lifetime measurement.
We demonstrate the generation of half-cycle terahertz pulses with elliptical polarization and 167 nJ pulse energy. These pulses have been generated using a 6H-SiC Large Aperture Photo-conductive Antenna (LAPCA) covered with a binary phase mask and excited by a 400 nm laser. We show that by changing the thickness of the phase mask and the geometry of the LAPCA it is possible to generate intense half-cycle...
Spectral dependence of nonlinear optical absorption cross-section (σ) near and below the bandgap (Eg) is measured for InN by using Z-scan technique. A drastic increase of σ near Eg can be understood by the band-filling model.
We have demonstrated kW-peak-power terahertz (THz)-wave parametric generation and 70 dB-dynamic-range detection by using efficient surface-coupling configuration. The system is capable of producing and detecting monochromatic THz-wave pulses in the wide frequency range from 0.8 to 2.8 THz.
A hybrid silicon ring laser in which the counter-clockwise circulating power is coupled into the clockwise mode is demonstrated. Unidirectional clockwise laser output is achieved with a suppression ratio of 19 dB over the counter-clockwise mode.
We provide a simple explanation for why laser media with distributed loss should have a sublinear output power characteristic. This understanding clarifies the role of long-range spatial hole burning in reducing the efficiency of semiconductor lasers, and is essential for optimizing power output.
Wavelength tuning in a single mode parity-time (PT) symmetric semiconductor microring laser is demonstrated. Stable continuous tuning over a spectral range of 4 nm has been obtained at telecom wavelengths by adjusting the ambient temperature.
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