572 results about "Femtosecond pulse" patented technology

An apparatus generates femtosecond pulses from laser amplifiers by nonlinear frequency conversion. The implementation of nonlinear frequency-conversion allows the design of highly nonlinear amplifiers at a signal wavelength (SW), while still preserving a high-quality pulse at an approximately frequency-doubled wavelength (FDW). Nonlinear frequency-conversion also allows for limited wavelength tuning of the FDW. As an example, the output from a nonlinear fiber amplifier is frequency-converted. By controlling the polarization state in the nonlinear fiber amplifier and by operating in the soliton-supporting dispersion regime of the host glass, an efficient nonlinear pulse compression for the SW is obtained. The generated pulse width is optimized by utilizing soliton compression in the presence of the Raman-self-frequency shift in the nonlinear fiber amplifier at the SW. High-power pulses are obtained by employing fiber amplifiers with large core-diameters. The efficiency of the nonlinear fiber amplifier is optimized by using a double clad fiber (i.e., a fiber with a double-step refractive index profile) and by pumping light directly into the inner core of this fiber. Periodically poled LiNbO3 (PPLN) is used for efficient conversion of the SW to a FDW. The quality of the pulses at the FDW can further be improved by nonlinear frequency conversion of the compressed and Raman-shifted signal pulses at the SW. The use of Raman-shifting further increases the tuning range at the FDW. For applications in confocal microscopy, a special linear fiber amplifier is used.

Various embodiments of a system described herein relate to micromachining materials using ultrashort visible laser pulses. The ultrashort laser pulses may be green and have a wavelength between about 500 to 550 nanometers in some embodiments. Additionally, the pulses may have a pulse duration of less than one picosecond in certain embodiments.

High efficiency reflective volume Bragg gratings with chirped gratings recorded in photo-thermo-refractive glass having an absolute diffraction efficiency exceeding 95% in transmitting and reflecting modes are used to stretch and/or compress ultrashort laser pulses with high efficiency. Robustness, compactness, thermal and laser stability along with placement of multiple elements in the same space provides femtosecond laser system with high efficiency of stretching and re-compression of femtosecond pulses.

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.

The invention relates to methods of writing a light-guiding structure in a bulk glass substrate. The bulk glass substrate is preferably made from a soft silica-based material having an annealing point less than about 1380°K. A pulsed laser beam is focused within the substrate while the focus is translated relative to the substrate along a scan path at a scan speed effective to induce an increase in the refractive index of the material along the scan path. Substantially no laser-induced physical damage of the material is incurred along the scan path. Various optical devices can be made using this method.

Waveguides produced in bulk glass using femtosecond pulsed lasers have diameters and refractive index profiles that are manipulated by additional motions or beams. For example, spot focuses of the femtosecond pulsed lasers trace overlapping or widened tracks by superimposing additional relative motions between the spot focuses and the bulk glass. Additional femtosecond pulsed beams can also be used to produced widened waveguides.

The present invention provides methods of fabricating a radiation-absorbing semiconductor wafer by irradiating at least one surface location of a silicon substrate, e.g., an n-doped crystalline silicon, by a plurality of temporally short laser pulses, e.g., femtosecond pulses, while exposing that location to a substance, e.g., SF₆, having an electron-donating constituent so as to generate a substantially disordered surface layer (i.e., a microstructured layer) that incorporates a concentration of that electron-donating constituent, e.g., sulfur. The substrate is also annealed at an elevated temperature and for a duration selected to enhance the charge carrier density in the surface layer. For example, the substrate can be annealed at a temperature in a range of about 700 K to about 900 K.

The invention relates to a nano-femtosecond dual-laser composite machining system. The system comprises a femtosecond laser, a nanosecond laser, a synchronous control circuit, an illuminating light source, a semi-transparent semi-reflecting mirror, a first dichroscope, a second dichroscope, a focusing lens and a charge coupled device (CCD) image detector, wherein the synchronous control circuit controls laser pulse output of the femtosecond laser and the nanosecond laser, and accurately adjusts relative time of nanosecond pulse and femtosecond pulse in the aspect of time to synchronize leading edges of the two pulses; the illuminating light source is positioned on one side of the semi-transparent semi-reflecting mirror, and the second dichroscope, the first dichroscope and the focusing lens are coaxially arranged on the other side of the semi-transparent semi-reflecting mirror in turn and are positioned on a straight line together with the illuminating light source; and the CCD image detector is positioned at the tail end of a reflecting light path of the semi-transparent semi-reflecting mirror. Through the system, the advantages of high femtosecond laser machining accuracy and high nanosecond laser machining efficiency are simultaneously integrated, and high-accuracy and high-efficiency micro-nano machining is realized; and the system can be widely applied to the fields such as high-accuracy machining of aviation and aerospace key parts, microstructure machining of a laser fusion ignition target, microstructure machining of a microsensor and the like.

The invention discloses manufacturing method and equipment of a single optical frequency comb with high stability and high repetition frequency. The method comprises the following specific steps of: outputting femtosecond pulses with high repetition frequency, wide spectrum and pulse width less than 7 fs by using a cycle-grade femtosecond titanium sapphire oscillator; carrying out beat measurement of the CEO of the femtosecond pulses by using a single nonlinear crystal; and simultaneously locking repetition frequency and CEO frequency to a stable external microwave reference source by using a circuit feedback technology. The equipment comprises the cycle-grade femtosecond titanium sapphire oscillator, the single nonlinear crystal beat measurement fceo device and a feedback circuit device controlled on the basis of the phase lock principle. The invention has the characteristics of compact equipment structure, long locking time, high usable output power, small phase noise and the like, and is mainly applied to the scientific researches of absolute optical frequency measurement, optical clock composition, atto-second production and the like.

The invention relates to a light frequency reference fiber femtosecond light frequency comb with tunable broadband repetition frequency. The comb comprises a hybrid-locking-based erbium-doped fiber femtosecond laser device with tunable broadband repetition frequency, a reference laser locking system based on piezoelectric ceramic, a reference laser locking system based on a pumping current, a computer control system and a temperature control system, wherein the erbium-doped fiber femtosecond laser device is an annular chamber structure and is internally added with an electric control optical delay wire, and the repetition frequency of the laser device can realize continuous tunable broadband. For realizing light frequency reference femtosecond pulse output, rapid and slow piezoelectric ceramics and the pumping current are employed to cooperatively control beat frequency of the femtosecond laser device and two reference laser devices, the rapid piezoelectric ceramics fixing structure which is easy to use is designed, and a temperature control box is further designed to acquire stable beat frequency; the light frequency reference fiber femtosecond light frequency comb has advantages of light frequency reference output, tunable broadband repetition frequency, good stability and small size and further has application potential in the industrial environment.

The invention relates to a method for improving the machining efficiency of micro-channel preparation through femtosecond laser, which belongs to the technical field of femtosecond laser application. The method includes the steps: firstly, generating the femtosecond pulse laser by the aid of a femtosecond laser system, adjusting energy by means of combination of a half wave plate and a polarizing film and modulating the femtosecond laser into femtosecond interval pulse sequence by the aid of a pulse shaper; secondly, reflecting the pulse sequence laser obtained in the first step to an objective lens for focusing through a reflector, realizing imaging by the aid of a CCD (charge coupled device) and a lighting source, moving a six-dimensional precision electric control platform and positioning a laser focus on the lower surface of a sample horizontally placed on the six-dimensional precision electric control platform; and thirdly, controlling the six-dimensional precision electric control platform to move along a laser propagation direction by the aid of a computer to machine a micro-channel on the sample. As the femtosecond laser is modulated into the femtosecond interval pulse sequence by the aid of the pulse shaper, the micro-channel preparation efficiency is improved. Moreover, introduction of a vibration source is omitted, so that controllability of precision machining cannot be reduced.

A source of high-power femtosecond optical pulses comprises a combination of a relatively short rare-earth doped fiber amplifier (e.g., less than five meters) with a first section of single mode fiber (or other dispersive element) disposed at the input of the amplifier to “pre-chirp” the output from a femtosecond pulse source, and a second section of single mode fiber fused to the output of the fiber amplifier to provide compression to the amplified pulses generated by the fiber amplifier. The rare-earth doped fiber amplifier is formed to comprise a normal dispersion, which when combined with self-phase modulation and distributed gain leads to a regime in amplifiers defined as “self-similar propagation”. In this regime of operation, the fiber amplifier generates high energy pulses with a parabolic shape (the parabolic shape defined as a function of time). These pulses also exhibit a strong linear chirp, where the linear nature of the chirp leads to efficient compression of the pulses.

Embodiments of the present invention are generally related to a fiber assembly, for example, in a chirped pulse amplification system, for all-fiber delivery of high energy femtosecond pulses. More specifically, embodiments of the present invention relate to a system and method for improving dispersion management when using hollow core photonic bandgap fibers for pulse compression. In one embodiment of the present invention, a fiber assembly comprises: an optical laser oscillator; a first fiber section for stretching the pulses from the laser oscillator, the first fiber section comprising a high order mode fiber; and a second fiber section for compressing the stretched pulses, connected to the first fiber section via a splice, the second fiber section comprising a hollow core photonic bandgap fiber; wherein the fiber assembly outputs a pulse compression at less than 200 fs.

A modelocked fiber laser is designed to have strong pulse-shaping based on spectral filtering of a highly-chirped pulse in the laser cavity. The laser generates femtosecond pulses without a dispersive delay line or anomalous dispersion in the cavity.

An apparatus and methods for generating a substantially supercontinuum-free widely-tunable multimilliwatt source of radiation characterized by a narrowband line profile. The apparatus and methods employ nonlinear optical mechanisms in a nonlinear photonic crystal fiber (PCF) by detuning the wavelength of a pump laser to a significant extent relative to the zero-dispersion wavelength (ZDW) of the PCF. Optical phenomena employed for the selective up-conversion in the PCF include, but are not limited to, four-wave mixing and Cherenkov radiation. Tunability is achieved by varying pump wavelength and power and by substituting different types of PCFs characterized by specified dispersion properties.

The present invention relates to an amplifier chain for generating ultrashort light pulses of different pulse durations and applies in particular to amplifier chains suitable for amplifying picosecond and femtosecond pulses. The amplifier chain comprising a stretcher with at least one entry dispersive element of the grating type and intended to temporally stretch an incident pulse, an amplifying medium designed to amplify said stretched pulse, a compressor with at least one entry dispersive element substantially identical to that of the stretcher, designed to temporally compress said amplified pulse. According to the invention, the stretcher and the compressor include means for moving the dispersive elements between first and second positions, in such a way that the angle of incidence in a first position is equal to the angle of diffraction in the second position, and vice versa, allowing two degrees of stretch of the chain to be defined, each adapted to the amplification of pulses of different durations.