Visible Picosecond Pulses Research Articles

Narrow-bandwidth tunable picosecond pulses in the visible produced by noncollinear optical parametric amplification with a chirped blue pump

Narrow-bandwidth (approximately 27 cm(-1)) tunable picosecond pulses from 480 nm-780 nm were generated from the output of a 1 kHz femtosecond titanium:sapphire laser system using a type I noncollinear optical parametric amplifier (NOPA) with chirped second-harmonic generation (SHG) pumping. Unlike a femtosecond NOPA, this system utilizes a broadband pump beam, the chirped 400 nm SHG of the Ti:sapphire fundamental, to amplify a monochromatic signal beam (spectrally-filtered output of a type II collinear OPA). Optimum geometric conditions for simultaneous phase- and group-velocity matching were calculated in the visible spectrum. This design is an efficient and simple method for generating tunable visible picosecond pulses that are synchronized to the femtosecond pulses.

From femtosecond infrared to picosecond visible pulses: temporal shaping with high-efficiency conversion

We present a single-pass frequency doubler that efficiently converts broadband near-infrared femtosecond pulses into narrow-spectrum visible picosecond pulses. An optimal control technique is introduced for properly designing aperiodically poled nonlinear crystals to generate visible pulses of the desired amplitude, phase profile, and carrier wavelength.

A restructuring of the CO/Pt( [formula omitted]) surface induced by femtosecond laser pulses?

Femtosecond visible pulses at 800 nm are observed to induce permanent spectral changes in the CO internal stretch region of CO/Pt(1 1 1) at 300 K, using sum frequency generation vibrational spectroscopy. By contrast, IR femtosecond, and visible picosecond pulses do not induce any change. Defects, disordering, water coadsorption or laser induced CO dissociation can be ruled out to account for the observed changes, which seem to be due to the formation of a metastable structure. With this structure, the CO coverage seems to increase reversibly in equilibrium with gas phase CO, which normally occurs on various surfaces, but not on Pt(1 1 1). An unusually high frequency for linearly bonded CO at 300 K is obtained above ≈10 −7 mbar. More experimental work using other techniques is required to confirm the occurrence of a metastable structure and to characterize it. Nevertheless the available spectroscopic and structural data concerning CO on Pt(1 1 1) do not support an interpretation where the laser induced metastable structure would remain close to the regular c(4×2) structure.

Experimental investigation of nonlinear frequency conversion in pure SiO/sub 2/-core monomode optical fibers pumped at 1.319 μm: single pass and oscillators

Generation of intense visible picosecond pulses in the spectral region of 580-610 nm through efficient nonlinear frequency conversion of 1.319 /spl mu/m Nd:YAG Q-switched and mode-locked laser pulses in pure SiO/sub 2/-core single mode optical fibers was experimentally investigated. Peak powers of ten's of watts in single-pass arrangement and over 100 W in synchronously pumped amplifier/oscillators were obtained. The LP/sub 02/ mode signal light generated exhibits threshold power, critical fiber length, and an asymmetrical spectrum of a few nanometers. A phase-matched four-wave mixing process involving two photons around 800 nm and one photon around 1.4 /spl mu/m was responsible for the visible light generation. Varying the test fiber minimum dispersion wavelength, the four-wave mixing signal wavelength is shifted within the region of 580-610 nm. >

Complete all-optical switching of visible picosecond pulses in birefringent fiber

Switching of visible picosecond pulses with a 50:1 contrast ratio is demonstrated in a time-division interferometry arrangement. The high-contrast switching of the signal is accomplished by uniform cross-phase modulation by an orthogonally polarized control pulse that walks through the signal during propagation in a strongly birefringent 10-m fiber.

Colliding visible picosecond pulses in optical fibers

The observation of the nonlinear interaction of two visible picosecond pulses, separated by a small time interval, while propagating in an optical fiber is reported. It is found that as propagation proceeds, a region of pulse collision develops in which intensity oscillations form that are similar to those recently observed in optical wave breaking. The frequency of these oscillations increases for an increasing time separation between the input pulses and is found to be as large as 5 THz. For small time intervals between the input pulses no oscillations formed. This observed behavior is found to agree well with numerical integrations of the nonlinear Schrödinger equation.

Parametric excitation of continuously tunable visible picosecond pulses

An experimental investigation was made of parametric generation of ultrashort light pulses in KDP and ADP crystals pumped with the third and fourth harmonics of single picosecond pulses emitted from a YAG:Nd3+ laser. The frequency width of the parametric superluminescence ranged from 10 to 5300 cm−1 depending on the phase conditions in the three-frequency interaction and the focusing parameters of the pump radiation. The efficiency of conversion of the pump radiation reached 10–15%. The results demonstrated potential usefulness of the parametric superluminescence continuum in picosecond spectroscopy.