Anna Fragemann

Second-order nonlinearities in the domain walls of periodically poled KTiOPO4

The domain wall regions in periodically poled KTiOPO4 crystals were examined and found to give rise to phasematched second harmonic generation in the Cerenkov directions. This phenomenon is caused by the nonlinear coefficients d11 and d12, which are not present in single domain regions, but are nonzero at and close to domain walls. The appearance of these nonlinearities is attributed to strain, produced by the domain inversion process and results in the creation of a dc piezoelectric field.

Bright, single-spatial-mode source of frequency non-degenerate, polarization-entangled photon pairs using periodically poled KTP

We use two perpendicular crystals of periodically-poled KTP to directly generate polarization-entangled photon pairs, the majority of which are emitted into a single Gaussian spatial mode. The signal and idler photons have wavelengths of 810 nm and 1550 nm, respectively, and the photon-pair generation rate is 1.2x107 sec-1 for a pump power of 62 mW. The apparatus is compact, flexible, and easily to use.

Enhanced stimulated Raman scattering in optical parametric oscillators from periodically poled KTiOPO4

Enhanced Raman scattering and concurrent Raman oscillation have been observed in nanosecond optical parametric oscillators in the near-infrared spectral region for certain periodicities of periodic ...

Frequency converters from visible to mid-infrared with periodically poled RbTiOPO4

Electric-field poling has been used to fabricate quasi-phase-matched frequency converters in RbTiOPO4. A more accurate Sellmeier equation has been obtained for wavelengths between 0.43 and 3.4 mum. ...

Broadband nondegenerate optical parametric amplification in the mid infrared with periodically poled KTiOPO4.

We theoretically and experimentally demonstrate that the bandwidth in a nondegenerate optical parametric amplifier can be substantially increased by noncollinear interaction in a quasi-phase-matched single-periodicity structure. Broadband amplification of signals between 1540 and 1720 nm was realized in periodically poled KTiOPO4. The achieved signal bandwidth of 6.9 THz at 1680 nm is large enough to accommodate sub-100 fs optical pulses.

High-resolution domain imaging on the nonpolar y-face of periodically poled KTiOPO4 by means of atomic force microscopy

The inverse piezoelectric effect is used to produce high-resolution images of ferroelectric domains in periodically poled KTiOPO4 crystals on their nonpolar y-face using atomic force microscopy. We ...

High-peak power nanosecond optical parametric amplifier with periodically poled KTP

A two-stage optical parametric amplifier generating 5 ns 208 kW peak power pulses in the spectral region at 1.535 microm in a diffraction-limited beam was realized in a single periodically poled KTP crystal. The maximum small-signal gain for the two stages reached 75dB and the total conversion efficiency was 30%. An analysis of the small-signal gain dependence on the M2 of the pump beam is presented for the collinear and noncollinear OPA. Efficient spectral broadening of the signal was demonstrated in short pieces of single-mode telecommunication fiber.

Efficient all-diode-pumped double stage femtosecond optical parametric chirped pulse amplification at 1-kHz with periodically poled KTiOPO4

A practical efficient optical parametric chirped pulse amplification is demonstrated with periodically poled KTiOPO4. It provides a compact solution to amplify stretched pulses to the 100 µJ level (signal + idler) at 1 kHz. The amplified signal pulses near 1.57 µm are recompressed to 270 fs.

Optical parametric amplification of a gain-switched picosecond laser diode

Optical parametric amplification, employing periodically poled KTiOPO4 as the gain medium, was used to amplify radiation emitted by a gain-switched laser diode. The pulses, which had durations between 20 ps and 2 ns, were amplified with up to 50 dB in a double stage set-up and reached pulse energies of 1 and 23 microJ, respectively.

Active and passive hybrid mode-locking of a Nd:YVO 4 laser with a single partially poled KTP crystal

We report on a Nd:YVO(4) laser mode-locked with a hybrid active and passive modulator consisting of a single partially poled KTP crystal. The periodically poled part provides negative cascaded Kerr-lensing, which together with intracavity soft and hard apertures gives passive modulation. Active phase modulation comes from the electro-optic effect by applying a voltage over the unpoled part of the crystal. The active modulation provides pulse lengths of about 95 ps, which initiate pulse shortening and self-sustained passive mode-locking by the cascaded Kerr effect. The repetition rate of the laser was 94 MHz and the output power was 350 mW, with a bandwidth of 0.235 nm and pulse lengths down to 6.9 ps.