The signal and idler beams from a picosecond, synchronously pumped optical parametric oscillator (OPO) provide the two colors necessary for coherent anti-Stokes Raman scattering (CARS) microscopy. OPO provides continuously tunable frequency difference between over broad range of shifts (100-3700 cm(-1)) by varying temperature single nonlinear crystal. near-infrared output (900-1300 nm) allows deep penetration into thick samples reduced photodamage. Applications this light source to in vivo...

A ZnGeP>(2) (ZGP) optical parametric oscillator (OPO) with wide mid-IR tunability has been demonstrated. The singly resonant angle-tuned ZGP OPO was pumped by 100-ns erbium laser pulses at lambda =2.93mum and yielded output that continuously tunable from 3.8 to 12.4 mum (type I phase matching) 4 10 II matching). An pump threshold less than 1 mJ in the whole 4-12 range of output, quantum conversion efficiency reached 35%. linewidth typically a few wave numbers; however, single intracavity...

We demonstrate a new approach to coherent anti-Stokes Raman scattering (CARS) microscopy that significantly increases the detection sensitivity. CARS signals are generated by collinearly overlapped, tightly focused, and raster scanned pump Stokes laser beams, whose difference frequency is rapidly modulated. The resulting amplitude modulation of signal detected through lock-in amplifier. This scheme efficiently suppresses nonresonant background allows for far fewer vibrational oscillators...

We provide a proof-of-principle demonstration of CARS endoscopy. The design utilizes single mode optical fiber with focusing unit attached to the distal end. Picosecond pump and Stokes pulse trains in near infrared are delivered through nearly unaltered spectral temporal characteristics at intensities needed for endoscopic images recorded by collecting epi-CARS signal generated sample raster scanning respect fiber. This endoscope prototype represents an important step towards situ chemically...

We have investigated photoexcited carrier lifetimes in arsenic-ion-implanted semi-insulating GaAs by time-resolved reflectivity measurements. Subpicosecond (220 to 550 fs) which do not exhibit apparent dosage dependence for samples bombarded with 200 keV arsenic ions at increasing dosages the range of 1012 and 1016 ions/cm2 are reported. The shortest lifetime was observed sample irradiated 1013 ions/cm−2. These ever ion-damaged comparable those low-temperature molecular beam epitaxially...

We report a narrow-linewidth ZnGeP2 (ZGP) optical parametric oscillator (OPO). It employs Q-switched Nd:YAG-laser-pumped LiNbO3 OPO with an output at λ=2.55 µm that is used as pump for the ZGP OPO. With singly resonant type II cavity containing diffraction grating and Si etalon, we achieved mid-IR tunability from 3.7 to 8 linewidth of ∼0.1 cm-1, corresponding ∼3 axial modes. have also demonstrated such can be fairly broadband (∼15 cm-1) pump.

We report on power, tuning, and temporal characteristics of an optical parametric oscillator (OPO) based a periodically poled stoichiometric lithium tantalate (PPSLT) crystal pumped by high-power mode-locked Ti:sapphire laser. Focus is given to the OPO operating range spanning from 900 1350 nm, which important in nonlinear microscopy spectroscopy. Generation peak powers beyond 10 kW level strongly affected onset intracavity power-dependent loss, due high ultrafast Kerr nonlinearity gain...

Ultrafast decay of optical phonons has been studied in wide-bandgap BaSnO

We describe experimental results on label free imaging of striated skeletal muscle using second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) microscopy.The complementarity the SHG CARS data makes it possible to clearly identify main sarcomere sub-structures such as actin, myosin, acto-myosin, intact T-tubular system emanates from sarcolemma.Owing sub-micron spatial resolution high sensitivity microscopy technique we were able resolve individual myofibrils.In...

Relaxation of coherent TO phonons is investigated in bulk GaAs and InP using an infrared time-resolved anti-Stokes Raman scattering technique. Measurements were performed as a function the crystal temperature range 10--300 K permitting determination dominant phonon relaxation channels. The experimental results are consistent with decay into TA LA while two identical energy dominates at low temperatures.

Efficient optical parametric oscillation is demonstrated in periodically poled stoichiometric lithium tantalate crystal pumped by a mode-locked Ti:sapphire laser. The oscillator (OPO) delivers maximum average power of more than 345 mW signal and 180 idler beams. OPO continuously tunable across the 940-1350 nm wavelength range its branch, delivering nearly transform-limited 160-180 fs pulses. Despite onset high absorption loss mid-IR, 40 obtained for beam within 4.3-4.6 μm range. gain allows...

We report on measurements of the ultrafast changes in absorption and refractive index pure GaAs near-infrared midinfrared ranges optical spectrum. The multicolor experiments have been performed by using an parametric oscillator that allowed photoexcitation electron-hole plasma, probing associated both parts dielectric function a wide spectral range (\ensuremath{\sim}1--4 \ensuremath{\mu}m) with femtosecond time resolution. found while change is primarily due to resonant inter-valence-band...

The relaxation dynamics of coherent phononlike LO-phonon--plasmon hybrid modes is investigated in $n$-doped GaAs using an infrared time-resolved anti-Stokes Raman scattering technique. Measurements performed for different crystal temperatures the range 10--300 K as a function electron density injected by doping show large reduction mode dephasing time compared to bare LO-phonon one densities larger than ${10}^{16}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}.$ results are interpreted terms decay...

We report on the design and performance of a time-resolved Coherent Raman spectroscopy system with time resolution better than 120 fs. The coherent transients can be traced more 75 dB dynamic range while accessing probing active modes across 250-2400 cm-1 frequency. delivers an equivalent spectral 0.1 regarding line bandwidth parameters for probed resonances.

Ultrafast relaxation dynamics of light and heavy holes in GaAs following femtosecond valence-to-conduction-band excitation are measured by probing the light- heavy-to-split-off hole transitions at different midinfrared wavelengths using recently developed broadly tunable optical parametric oscillator. The initial times less than 75 fs, a spectral hole-burning effect is seen. results suggest that carrier–carrier optical-phonon scattering, particular, polar primary processes leading to...

We propose and experimentally demonstrate a method that is capable of resolving both real imaginary parts third-order nonlinearity (χ(3)) in the vicinity Raman resonances. Dispersion χ(3) can be obtained from medium probed within microscopic volumes with spectral resolution better than 0.10 cm(-1).

Femtosecond time-resolved reflectivity measurements, structural, and electrical analyses have been performed to investigate the effect of rapid thermal annealing (RTA) on GaAs implanted with 200 keV arsenic ions at 1016 ions/cm2. Ultrashort carrier lifetimes from 0.48 fs 2.3 ps were observed for samples annealed temperatures between 600 800 °C. The time constants are somewhat shorter than those RTA-annealed low-temperature molecular-beam epitaxy grown material, while following same trend...

Generation of transform limited picosecond pulses continuously tunable across wavelengths in the near-infrared (995–1340 nm) and midinfrared (2.1–3.6 μm) range is demonstrated an optical parametric oscillator (OPO) based on a periodically poled stoichiometric lithium tantalate crystal. The OPO, which synchronously pumped by mode-locked Ti:sapphire laser, delivers about 1 W combined average power at repetition rate 74 MHz, represents close to 45% extraction efficiency output power. With...

We report on the realization of a sensitive microspectroscopy and imaging approach based three-color femtosecond coherent anti-Stokes Raman scattering (CARS) technique with high spectral, time, spatial resolution. Independently tunable, high-repetition rate optical parametric oscillators were used to attain dynamic range 5 orders magnitude for time-domain CARS signal. The attained sensitivity permitted tracing decay weak structurally complex active modes in soft condensed matter. Application...

Ultrafast decays of the intrinsic phonon modes within 260–790 cm−1 range frequencies, which are symmetry forbidden in first-order Raman scattering bulk SrTiO3 crystal, have been traced using time-resolved coherent technique. The effective decay times 0.86–1.38 ps and yield corresponding linewidths 7.7–12.3 for optical lattice vibrations. Symmetry breakage mechanisms related to free charged carriers resulting from vacancies do not appear play a major role.

Completely self-starting and stable operation of a Kerr-lens mode-locked Ti:sapphire laser was realized in both picosecond femtosecond regimes. The cavity has symmetric X configuration with soft aperturing. Enhanced Kerr nonlinearity reduced backscattering effects were thought to be key obtaining self-mode-locked from 765 815 nm for the regime 770 835 regime. mode-locking starting time as measured by onset second-harmonic signal ranged 300 ms 2 s, depending on alignment. Preliminary data...