Parametric generation and characterization of femtosecond mid-infrared pulses in ZnGeP2.

Ultrafast mid-infrared (IR) coherent radiation plays an important role in strong-field physics, wherein the use of longer wavelengths has reduced the optical intensities needed to drive light-matter interactions by orders of magnitude in comparison to near-IR radiation. Optimizing parametric interactions for generation and characterization of mid-IR pulses is an enabling step for those applications. We report on the production of >50 µJ femtosecond pulses centered at 5 µm in a two-stage optical parametric amplifier (OPA) based on ZnGeP2, a high-performance optical material in this spectral region. The OPA is pumped by an ultrafast 2-µm source. Amplified pulses have been characterized by parametric upconversion, enabling the use of standard silicon detectors. A numerical model of the system has been developed and tested to control dispersion, group-velocity mismatch, and off-axis parametric fluorescence. The source architecture is suitable for production of mJ-level mid-IR ultrafast pulses without the use of chirped-pulse amplification, where convenient pumping could be realized directly by mid-IR laser sources based on materials such as Cr:ZnSe or Cr:ZnS.

Nondegenerate parametric generation of 2.2-mJ, few-cycle 2.05-µm pulses using a mixed phase matching scheme.

We describe the production of 2.2-mJ, ∼6 optical-cycle-long mid-infrared laser pulses with a carrier wavelength of 2.05 µm in a two-stage ß-BaB2O4 nondegenerate optical parametric amplifier design with a mixed phase matching scheme, which is pumped by a standard Ti:sapphire chirped-pulse amplification system. It is demonstrated that relatively high pulse energies, short pulse durations, high stability, and excellent beam profiles can be obtained using this simple approach, even without the use of optical parametric chirped-pulse amplification.

Efficient generation of backward terahertz pulses from multiperiod periodically poled lithium niobate.

Backward terahertz pulses were converted from ultrafast pulses of a laser amplifier within multiperiod periodically poled LiNbO3 (PPLN) wafers. The average output powers of more than 2 microW were obtained from all six domain periods, corresponding to the frequency range of 217 GHz-2.373 THz. Among the six periods, the highest output power of 10.7 microW and the narrowest linewidth of 5.98 GHz were achieved at the periods of 66.5 microm and 150.0 microm, respectively.

Watt-level single-frequency tunable Nd:YLF/periodically poled KTiOPO(4) red laser.

Intracavity second-harmonic generation of a diode-pumped Nd:YLiF(4) ring laser oscillating on the sigma-polarized (4)F(3/2) - (4)I(13/2) transition (lambda(omega) ~ 1314 nm) with a temperature-tuned periodically poled KTiOPO(4) (ppKTP) crystal is reported, yielding up to 0.92 W tunable (lambda(2omega) = 656-658 nm) single-frequency output. Evidence of self-mode-locking via cascading nonlinearities is observed when the ppKTP is strongly phase mismatched.

[Study on two-photon induced fluorescence of newly synthesized chromophore BECVN and BMABN].

One-photon fluorescence(OPF) and two-photon fluorescence (TPF) of two chromophores 1,4-bis(9-ethyl-vinyl carbazole) naphthalene (abbreviated as BECVN) and 1,4-bis(4-N, N-methylamino styryl) naphthalene (abbreviated as BMABN) were resported. Strong emission at 492-541 nm and at 500-556 nm, respectively, were obtained under the excitation of -370 nm (Xe lamp) and of 730-800 nm femto-second laser pulses, respectively. Although the relative fluorescence quantum yield (phi(f)) of BECVN is as high as 7.4 times that of BMABN, the latter possesses higher TPF intensity and larger two-photon absorption (TPA) cross-section, suggesting that BMABN containing naphthalene as pi-center end-capped with N,N-methylamino styryl group exhibits more effective two-photon process. Lippert equation showed that the difference of dipole momnet (deltamu(ge)) between the ground state and the excited state for BECVN is nearly twice that for BMABN, conforming to that the deltamu(ge) value is not the key for the enhancement of two-photon absorption cross-section.

Triaryl boron-based A-pi-A vs triaryl nitrogen-based D-pi-D quadrupolar compounds for single- and two-photon excited fluorescence.

Three new A-pi-A-type compounds with trivalent boron, protected by two mesityl groups, as electron acceptor have been synthesized and investigated together with their two diphenylamino-ended D-pi-D analogues. These boranes exhibit large two-photon absorption cross sections and high fluorescence quantum yields.