Noncollinear Sum-frequency Mixing Research Articles

Rapidly tunable femtosecond near-UV pulses from a non-collinear optical parametric oscillator.

Broadband tunable femtosecond laser pulses are of great interest in numerous fields, such as spectroscopy or imaging. Here, we report on the generation of rapidly tunable radiation in the near UV by using intracavity non-collinear sum-frequency mixing between the visible pulses of a non-collinear optical parametric oscillator (NOPO) and a near-infrared beam. The NOPO is pumped by the third harmonic of an Yb-based master oscillator fiber amplifier (MOFA). For sum-frequency mixing, remaining fundamental pulses at 1030 nm are used. With this approach, near-UV pulses in a range of 333-413 nm with average output powers up to 90 mW and pulse durations from 158-240 fs are achieved. Fast tunability is demonstrated over the whole tuning range by varying just the cavity length. The system also allows for the generation of two simultaneous synchronized output pulse trains in the visible and the near-UV spectral range.

High-energy picosecond near-vacuum ultraviolet pulses generated by sum-frequency mixing of an amplified Ti:sapphire laser

We demonstrate high-energy picosecond near-vacuum ultraviolet laser pulse generation. Frequency quadrupling is achieved by noncollinear sum-frequency mixing of the fundamental and the third harmonic of a two-stage Ti:sapphire amplifier in beta-BaB(2)O(4) crystal. UV pulses with energies of approximately 10 mJ tunable from 195 to 210 nm at a 10 Hz repetition rate are obtained.

Widely tunable deep ultraviolet generation in CLBO

In a single cut cesium lithium borate (CsLiB 6O 10 or CLBO) crystal we have generate deep UV radiation tunable from 195 to 265 nm (with a gap from 210 to 226 nm due to crystal cut limitation). Radiation in the 195–210 nm region is generated by noncollinear sum-frequency mixing of Nd:YAG laser radiation with the second harmonic (239–262 nm) of the dye laser radiation. However, radiation in the region of 210–237.5 nm and 236.8–265 nm is generated by third harmonic and second harmonic generation of the dye laser, respectively. All three interactions for coverage of the said range are made in the same cut CLBO crystal Type-I, θ=80° and ϕ=45°. The shorter wavelength tuning is phase-matching limited. A conversion efficiency of 14% is realised in our 5.5 mm long crystal for the generation of 241.7 nm radiation by Type-I second harmonic generation with a fundamental input beam intensity as low as 14.6 MW/cm 2.

Tunable coherent far-UV generation by frequency conversion in BBO

Tunable vacuum ultraviolet radiation below 200 nm was generated in a beta barium borate (BBO) crystal by noncollinear sum-frequency mixing (SFM) of Nd:YAG laser radiation and the second harmonic of a dye laser pumped by the third harmonic of the neodymium laser. The lower limit attained was 187.9 nm, being the shortest wavelength generated in the crystal to date. The tunability was extended, up to 230 nm, in BBO by generation of the third harmonic (SFM of the second harmonic with the fundamental) of the dye laser pumped by the second harmonic of the Nd:YAG laser. An SFM conversion efficiency as high as 21% was achieved when the energy of the fundamental dye-laser beam was only 10 mJ.

Efficient generation of 200–230-nm radiation in beta barium borate by noncollinear sum-frequency mixing: errata

Efficient generation of 200–230-nm radiation in beta barium borate by noncollinear sum-frequency mixing: errata

Efficient generation of 200–230-nm radiation in beta barium borate by noncollinear sum-frequency mixing

Tunable ultraviolet radiation in the 200-230-nm region has been generated with beta barium borate crystals by type I sum-frequency mixing of the second harmonic with the fundamental beam from a dye laser pumped by the second harmonic of the same Nd:YAG laser. A noncollinear phase-matching configuration has made it possible to realize conversion efficiency of 21% at 208.3 nm with input power densities as low as 28 MW/cm(2) for the fundamental and 2.4 MW/cm(2) for its second-harmonic radiation. The absorption characteristic of a standard DNA sample has been studied with the generated tunable ultraviolet source, revealing additional features compared with those obtained with a spectrophotometer.

Collinear and non-collinear sum-frequency mixing in?-BBO for a tunable 195?198 nm all-solid-state laser system

We attained tunable UV laser radiation between 195 and 198 nm by sum-frequency mixing two synchronized flashlamp-pumped solid-state Q-switch lasers, a Nd:YAG laser frequency quadrupled to 266 nm and a tunable (730–770 nm) alexandrite laser. UV pulse energies of 0.12 mJ with repetition rates of 10 Hz were attained in collinear, as well as non-collinear sum-frequency interaction in aβ-Barium Borate (BBO) crystal with a conversion efficiency of 2.5%. Theoretical models for the non-collinear phase-matching interaction were investigated at UV wavelengths below 200 nm.

Noncollinear ultraviolet generation in a lithium borate crystal

Nd:YAG and a Nd:YAG-pumped dye laser are used to generate tunable deep ultraviolet radiation down to 240 nm in a lithium triborate crystal (LBO) by noncollinear sum-frequency mixing. All longer wavelengths can be generated by a combination of harmonic generation of the dye laser and sum-frequency mixing, 240 nm being the near noncritical limit. A set of versatile Sellmeier dispersion equations is derived to satisfactorily predict phase-matching in LBO.

A technique for the calculation of phase-matching angle for type-II noncollinear sum-frequency generation in negative uniaxial crystals

A technique of predicting the phase-matching angle for noncollinear sum-frequency mixing involving two extraordinary rays and one ordinary ray in a negative uniaxial crystal is described, and predicted results are experimentally verified. Good agreement between predicted and experimental results gives the technique a firm footing, thereby introducing a very simple relation correlating the noncollinear angle with the phase-matching angles of the interacting beams.