Juan L. A. Chilla

Direct determination of the amplitude and the phase of femtosecond light pulses.

A direct measurement of the amplitude and the phase of a femtosecond light pulse is performed for the first time to our knowledge. The measurement is made in the frequency domain, and the time dependence of the field can be easily obtained by a Fourier transform. The technique relies on a pulse synthesis scheme to unravel the frequency dependence of the phase. A mask filters the spectrum, which gives rise to a pulse with a measurable temporal profile related to the frequency dependence of the phase. In particular, with a rectangular slit the time delay of the synthesized pulse is the first derivative of the phase with respect to the frequency of the original pulse at the central frequency of the filter. The amplitude of the spectrum is obtained from the power spectrum.

High-power optically pumped semiconductor lasers

Optically pumped, external-cavity, surface emitting semiconductor lasers (also known as optically pumped semiconductor lasers, OPS lasers, and vertical external cavity surface emitting lasers, VECSELs) generate near-diffraction limited beams from low brightness diode-array pumps. We have demonstrated 30 W cw at 980 nm and 15 W cw at 488 nm in a single spatial mode from these emitters and believe they can be scaled to > 100 W. Potential applications we have explored for such devices include wavelength conversion, spectral and spatial brightness conversion.

Polarization switching in vertical-cavity surface emitting lasers observed at constant active region temperature

Polarization switching in gain-guided, vertical-cavity, surface-emitting lasers was studied as a function of the active region temperature. We show that polarization switching occurs even when the active region temperature is kept constant during fast pulse low duty cycle operation. This temperature independent polarization switching phenomenon is explained in terms of a recently developed model.

Recent advances in optically pumped semiconductor lasers

Optically pumped semiconductor lasers offer significant advantages with respect to all traditional diode-pumped solid state lasers (including fiber lasers) in regards to wavelength flexibility, broad pump tolerance, efficient spectral and spatial brightness conversion and high power scaling. In this talk we will describe our recent progress in the lab and applying this technology to commercial systems. Results include diversified wavelengths from 460 to 570nm, power scaling to >60W of CW 532nm, and the launch of a low cost 5W CW visible source for forensic applications.

Dense plasma diagnostics with an amplitude-division soft-x-ray laser interferometer based on diffraction gratings

We report the demonstration of an amplitude-division soft-x-ray interferometer that can be used to generate high-contrast interferograms at the wavelength of any of the saturated soft-x-ray lasers (5.6-46.9 nm) that are available at present. The interferometer, which utilizes grazing-incidence diffraction gratings as beam splitters in a modified Mach-Zehnder configuration, was used in combination with a tabletop 46.9-nm laser to probe a large-scale (~2.7-mm-long) laser-created plasma.

Analysis of a method of phase measurement of ultrashort pulses in the frequency domain

A detailed analysis of a method of phase measurement of ultrashort light pulses is performed. It is shown that the output pulse of a zero dispersion compressor with a mask consisting of a narrow slit is a wide pulse delayed an amount equal to the phase derivative of the field spectrum with respect to frequency. State criteria to determine whether the approximations are valid are presented. The method is not affected by artifacts coming from diffraction effects in the slit or by the fact that only correlations are measured. The effects of the errors in positioning the elements are considered and minimized in the construction of the experimental apparatus. A novel technique for measurement of the derivative of the cross correlation is described, and it is used to locate the delayed output pulse. >

Transverse-mode dynamics in vertical-cavity surface-emitting lasers excited by fast electrical pulses

Summary form only given. With modulation bandwidth of 10-15 GHz, vertical-cavity surface-emitting lasers (VCSELs) have become a suitable choice for optical interconnects. However, the presence of higher order modes in the cavity can cause rapid variations of the spectral, spatial and noise characteristics of the laser beam that can affect the gigahertz performance of these devices. Herein we present measurements of the response of VCSELs excited by 0.8-1-ns pulses that show the importance of mode competition and spatial hole burning in the dynamics in VCSELs.

Blue and green optically pumped semiconductor lasers for display

We discuss a compact RGB source with ouput power of several watts per color consisting of a red (638 nm) diode and OPS lasers with blue (460 nm) and green (530) nm output. Suitability for display applications is shown by replacing the lamp of a standard Rear Projection TV.

Discharge‐pumped soft‐x‐ray laser in neon‐like argon

Starting with the discovery of x‐ray lasers in 1984, laser‐created plasmas remained for almost a decade, the only medium in which large amplification of soft‐x‐ray radiation could be obtained. In this paper the recent first demonstration of large soft‐x‐ray amplification in a discharge‐created plasma column, realized utilizing a fast capillary discharge to collisionally excite the 46.9 nm transition of Ne‐like, Ar is reviewed. Results of the parametrization of the Ar IX discharge‐pumped amplifier, the study of the dynamics of its plasma column, and the measurement of the time history of the laser pulse are reported. Prospects for laser operation at shorter wavelengths are also discussed.

Spatial–temporal analysis of the self-mode-locked Ti: sapphire laser

We employ our extended spatial–temporal matrices to analyze the Ti: sapphire self-mode-locked laser. Our results agree with previously reported experimental work and give us a deeper understanding of the way this laser functions. We found the pulse-shaping mechanism to be essentially solitonlike; the role of the aperture is to discriminate against cw operation. We also study the buildup of the pulse starting from a fluctuation.