Abstract: A CARS system and method for probing a Raman signature of a sample are described. A short femtosecond pulse from one or more lasers is split into two pulses, a stimulus pulse and a probe pulse, whereby the probe pulse is time-delayed with respect to the stimulus pulse. Both pulses can be phase- and polarization-modulated. The stimulus pulse excites a vibronic level in the sample and the probe pulse probes molecular Raman transitions in the sample. A difference in the signals with and without excitation can be used to determine on which molecule a bond is most likely located. This will allow an accurate and sensitive determination of the presence of specific molecules in the sample. The system and method can be used to analyze biological samples and to discriminate between molecules having overlapping Raman signatures.

Abstract: A multi-wavelength, commonly mode-locked external cavity laser system includes a solid state gain element generating a collinearly propagating multi-wavelength optical beam, a diffracting element that diffracts the multi-wavelength optical beam into a plurality of diffracted optical beams, a wavelength-selective device receiving the plurality of diffracted optical beams and controllably transmitting or reflecting the diffracted optical beams depending on their wavelengths, and at least one mode-locking device that mode-locks the optical beams from the gain elements in common and thus forms a mode-locked optical output beam of picosecond or femtosecond duration and high peak power.

Abstract: A mode-locked external cavity laser device includes a plurality of gain elements with corresponding end mirrors, and a diffracting element that diffracts optical beams emitted by the gain elements and combines the diffracted optical beams to form an overlapping output beam. A mode-locking device that intercepts the overlapping output beam and in cooperation with the end mirrors forms the external cavity. The mode-locking device mode-locks the optical beams from the gain elements in common and thus forms a mode-locked optical output beam of picosecond or femtosecond duration and high peak power.

Abstract: An amplified commonly mode-locked and/or Q-switched external cavity laser device with a plurality of gain elements and a plurality of amplifying elements is described. The device produces amplified optical pulses of picosecond to nanoseconds duration. The amplified pulses can be used in applications requiring large optical pulse energy and also high average optical power, such as material processing, nonlinear optics, extreme UV spectroscopy, and generation of x-rays.

Abstract: A system and method for patterned exposure of a photoactive medium is described wherein a pulsed optical beam with a high peak-power is stretched in the time domain to reduce the peak power while maintaining the average power. The stretched pulse illuminated a pattern, such as a transparent or reflective photolithography mask. The pattern is then imaged onto the photoactive medium after recompressing the beam. This arrangement prevents damage to the mask by the high peak power of the pulsed optical beam.

Abstract: A grating structure with a dielectric coating is disclosed that operates efficiently away from the blaze angle in low order with a high diffraction efficiency and high wavelength dispersion. Such grating structure can be employed in Littrow configuration to provide, for example, cavity feedback in excimer lasers.

Abstract: A lamellar volume grating operating in reflection and transmission and providing a substantially wavelength- and polarization-independent diffraction efficiency is disclosed. The lamellar grating has an approximately rectangular grating profile with a height-to-width ratio of the grooves or “teeth” advantageously greater than 2. The grating operates preferably in first order and can be implemented as an immersion grating. In particular, the lamellar volume grating described herein can be employed in an optical multiplexer/demultiplexer arrangement with small overall dimensions.

Abstract: A multi-wavelength external cavity laser system is disclosed, wherein an array of individual laser elements is placed in a shared laser cavity for all wavelengths that is defined by a free space grating, an optional reflector, and a single relay lens. Laser radiation from the cavity can be externally modulated at each wavelength and outputted as an overlapping beam having substantially all the wavelengths produced by the laser elements through a single fiber or as an array of wavelength-separated beams. A modular design facilitates the addition and/or repair of individual or several channels.

Abstract: A multi-wavelength external cavity fiber laser system is disclosed. Laser radiation from the cavity can be externally modulated at each wavelength and outputted as an overlapping beam having substantially all the wavelengths produced by the laser elements through a single fiber or as an array of wavelength-separated beams. The fiber laser can include an intra-cavity etalon that allows all wavelength to be tuned simultaneously.

Abstract: A grating structure useful for WDM multiplexer/demultiplexer applications is described. The grating structure has a substantially polarization-independent diffraction efficiency of a predetermined useful wavelength range, for example, between 1.4 and 1.6 &mgr;m. Each grating period includes a triangular section and a flat-topped section, with the width of the flat-topped section between 20 and 50% of the grating period. The disclosed grating structure can be formed in any material that is substantially transparent over the useful wavelength range and used in either a Littrow and a Littman-Metcalf configuration.

Abstract: A grating device with a substantially polarization-independent diffraction efficiency is disclosed. The grating device is preferably a surface grating that can be produced by ruling or holographically, and includes at least two different grating elements with the same grating period, but different modulation depths or blaze angles. The blaze angles and the illuminated areas of the respective grating elements can be selected to produce a substantially polarization-independent and optionally also wavelength-independent response of the grating device.

Abstract: A laser wavelength meter determines the unknown wavelength of a laser by measuring the phase difference between two orthogonally polarized beams derived from the laser. The orthlogonally polarized beams propagaic along two optical paths of different length as defined, for example, by a polarizing beam splitter or a stepped reflector with a defined step height. An in situ reference laser of known wavelength allows calculation and monitoring of the path difference between the two optical paths.