Measurement Of Femtosecond Pulses Research Articles

Measurement of femtosecond pulses in the focal point of a high-numerical-aperture lens by two-photon absorption

We demonstrate a method for the measurement of femtosecond optical pulses in the focal point of a high-NA lens, using interferometric autocorrelation through two-photon absorption. A chirp-free input pulse of 47 fs is found to broaden by ≈50% after focusing by a well-compensated objective. With proper prechirp compensation, the actual pulse width in the focus of such a lens system can be restored to (almost) its initial value. The unique value of the presented two-photon autocorrelation technique is its capability of measuring the actual pulse width at the focal point of a high-NA lens, an aspect that is of direct importance to two-photon imaging approaches, for example.

Dispersion measurements for femtosecond-pulse generation and applications

Dispersive phenomena provide limits in the generation, measurement and applications of femtosecond optical pulses. Optical elements such as prisms, gratings, air, mirrors, filters, and laser crystals all contribute to the total dispersion in optical systems. Interferometric techniques enable measurements of dispersion of individual elements, and new techniques allow dispersion measurement inside the cavity of operating modelocked femtosecond tunable lasers. These techniques provide access to detailed information about dispersion errors which can distort pulses and produce undesirable effects in modelocked lasers. In this article, we review techniques for the measurement of dispersion in optical components and systems. In several cases, we compare measurements made with intracavity dispersion techniques with extracavity measurements and point out common features.

Ultrabroadband second-harmonic generation in organic and inorganic thin crystals

Organic thin crystals of 2-methyl-4-nitroaniline (MNA) have been used to frequency double simultaneously all components of a broadband continuum using a non-phase-matched configuration. A 1 μm sample of MNA permits to convert, in a single pulse, wavelengths in the band 600–1400 nm to the 300–700 nm band. Using the same technique, we also evidence the remarkably large bandwidth of a 100-μm-thick KDP, when used in the wavelength noncritical phase-matched region centered around 1.03 μm. The conversion efficiencies of the 1-μm-thick MNA sample and of the 100-μm-thick phase-matched KDP crystal are shown to be comparable. The results are of interest to the processing and measurement of femtosecond pulses.

Surface second-harmonic generation in Si(111) for autocorrelation measurements of 248-nm femtosecond pulses

124-nm radiation by surface second-harmonic generation was used to measure the pulse-width autocorrelation of femtosecond 248-nm pulses. Second-order autocorrelation was obtained for input fluences as high as 0.01 J/cm2. At higher input fluences, autocorrelation of higher order is observed.

Single-shot measurement of ultraviolet and visible femtosecond pulses using the optical Kerr effect

We present a method that allows the single-shot measurement of femtosecond pulses in the ultraviolet as well as the visible spectral regions. The method is based on the optical Kerr shutter technique, and it provides the third-order intensity correlation function.

Single-shot measurement of femtosecond pulses using the optical Kerr effect

The authors demonstrate the optical Kerr shutter technique as a simple and powerful tool for single-shot measurements of femtosecond pulses over a wide spectral range. The method provides the third-order intensity correlation function which gives information about pulse asymmetry and pulse structures.

Measurement of ultraviolet femtosecond pulses using the optical kerr effect

We demonstrate the optical Kerr shutter technique as a simple and powerful tool for the measurement of femtosecond pulses in the ultraviolet as well as in the visible spectral region. The method provides the third-order intensity correlation function which gives information about pulse asymmetry and pulse structures.

Chirp measurement of large-bandwidth femtosecond optical pulses using two-photon absorption

We describe a novel method for accurate chirp measurement of broadband femtosecond pulses over their entire bandwidth based on two-photon absorption. These chirp measurements are applied for the optimization of a fiber-grating-prism pulse compressor.

Two-photon absorption in diamond and its application to ultraviolet femtosecond pulse-width measurement

Intensity-dependent transmission measurements of 310-nm femtosecond pulses show that diamond has a twophoton absorption coefficient of 0.75 +/- 0.15 cm/GW, in approximate agreement with universal scaling formulas for two-photon absorption in diamond-structure materials. We then demonstrate that two-photon absorption is strong enough to permit simple measurements of ultraviolet femtosecond pulse widths in single-crystal diamond plates that are thin enough (250 microm) to be both inexpensive and dispersion free. Autocorrelation measurements of 10-50-nJ, 0.18-1.4-ps pulses are presented. The method requires no phase matching and can be applied to pulses in the wavelength range of 220-550 nm.