Abstract: An intracavity resonant Fabry-Perot saturable absorber (R-FPSA) induces modelocking in a laser such as a fiber laser. An optical limiter such as a two photon absorber (TPA) can be used in conjunction with the R-FPSA, so that Q-switching is inhibited, resulting in laser output that is cw modelocked. By using both an R-FPSA and a TPA, the Q-switched modelocked behavior of a fiber laser is observed to evolve into cw modelocking.

Abstract: An intracavity resonant Fabry-Perot saturable absorber (R-FPSA) induces modelocking in a laser such as a fiber laser. An optical limiter such as a two photon absorber (TPA) can be used in conjunction with the R-FPSA, so that Q-switching is inhibited, resulting in laser output that is cw modelocked. By using both an R-FPSA and a TPA, the Q-switched modelocked behavior of a fiber laser is observed to evolve into cw modelocking.

Abstract: Stable operation of an ultra-compact modelocked fiber laser generating short optical pulses generally without use of any non-fiber, intra-cavity polarization-manipulating elements is obtained by employing a saturable absorber coupled to one end of a highly-birefringent fiber serving as the laser cavity. Once the laser is modelocked in one of the polarization axes of the highly-birefringent fiber, the degeneracy of the polarization axis is eliminated and cw oscillation along the other polarization axis is also prevented. Without a polarization-dependent loss in the cavity, the modelocked polarization axis is indeterminate, i.e., modelocking can occur on either of the polarization axes. However, the introduction of only a small polarization dependent loss is sufficient to ensure the reliable start-up of modelocking on only the low-loss axis.

Abstract: The output power of a passively modelocked fiber laser is increased by distributing optical losses throughout the cavity. The laser cavity includes a saturable absorber and a polarizing element that serves as the output coupler, and these are positioned on opposite sides of the fiber gain medium. The pump light is preferably injected towards the side of the laser cavity that includes the saturable absorber. The laser cavity compensates for polarization drifts and is environmentally stable.

Abstract: 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.

Abstract: The present invention is directed to providing an environmentally stable, ultra-short pulse source. Exemplary embodiments relate to passively modelocked ultra-short fiber lasers which are insensitive to temperature variations and which possess only negligible sensitivity to pressure variations. Further, exemplary embodiments can be implemented in a cost-effective manner which render them commercially practical in unlimited applications. Arbitrary fiber lengths (e.g., on the order of 1 millimeter to 1 kilometer, or greater) can be used to provide an ultra-short pulse with a cost-effective architecture which is commercially practical.

Abstract: A compact fiber laser unit includes a laser source, a laser oscillator connected to the laser source for generating an optical and a laser amplifier connected to the laser oscillator for amplifying the optical pulse produced by the laser oscillator. The laser oscillator includes a first optical fiber that connects bulk components of the laser oscillator to the laser source and the laser amplifier includes a second optical fiber that connects bulk components of the laser amplifier to the laser source. The first and second fibers are wound around a common holder in the form of a fiber tray. The fiber tray is connected to a fiber bench and the bulk components of the laser oscillator and the laser amplifier are mounted on the fiber bench.

Abstract: 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.

Abstract: To amplify and compress optical pulses in a multi-mode (MM) optical fiber, a single-mode is launched into the MM fiber by matching the modal profile of the fundamental mode of the MM fiber with a diffraction-limited optical mode at the launch end. The fundamental mode is preserved in the MM fiber by minimizing mode-coupling by using relatively short lengths of step-index MM fibers with a few hundred modes and by minimizing fiber perturbations. Doping is confined to the center of the fiber core to preferentially amplify the fundamental mode, to reduce amplified spontaneous emission and to allow gain-guiding of the fundamental mode. Gain-guiding allows for the design of systems with length-dependent and power-dependent diameters of the fundamental mode. To allow pumping with high-power laser diodes, a double-clad amplifier structure is employed. For applications in nonlinear pulse-compression, self phase modulation and dispersion in the optical fibers can be exploited.

Abstract: The present invention is directed to methods and apparatuses for performing temporal scanning using ultra-short pulsewidth lasers in which only minimal (micro-scale) mechanical movement is required. The invention also relates to methods for obtaining high-accuracy timing calibration, on the order of femtoseconds. A dual laser system is disclosed in which the cavity of one or more of the lasers is dithered, by using a piezoelectric element. A Fabry-Perot etalon is used to generate a sequence of timing pulses used in conjunction with a laser beam produced by the laser having the dithered laser cavity. A correlator correlates a laser pulse from one of the lasers with the sequence of timing pulses to produce a calibrated time scale.

Abstract: The generation of ultrashort pulses with adjustable repetition rates from passively modelocked fiber lasers is demonstrated. By inserting semiconductor saturable absorbers with life-times of the order of 10 nsec into fiber lasers with cavity round-trip times of the order of 100 nsec, passive harmonic modelocking is obtained, leading to the stable generation of pulses at integer multiples of the fundamental cavity frequency. For polarization states that allow for optical limiting of the lasers, pulses are obtained in a frequency range between 20 and 500 MHz., where different repetition rates can be simply selected by changing the pump power level to the cavity. The pulse jitter within one cavity round-trip time is measured to be between 300 psec and 50 psec, where side bands in the frequency domain may be suppressed by up to 70 dB.

Abstract: Cladding-pumped fibers are used for chirped pulse amplification of ultrashort optical pulses, increasing the average output power by one order of magnitude and substantially decreasing the cost of pump sources. Broad-area multimode diode pumped Er/Yb codoped fiber amplifiers and MOPA pumped high-power Er-doped fiber amplifiers are used to achieve chirped pulse amplification.

Abstract: The present invention is directed to providing an environmentally stable, ultra-short pulse source. Exemplary embodiments relate to passively modelocked ultra-short fiber lasers which are insensitive to temperature variations and which possess only negligible sensitivity to pressure variations. Further, exemplary embodiments can be implemented in a cost-effective manner which render them commercially practical in unlimited applications. Arbitrary fiber lengths (e.g., on the order of 1 millimeter to 1 kilometer, or greater) can be used to provide an ultra-short pulse with a cost-effective architecture which is commercially practical.

Abstract: A technique for the generation of picosecond (psec) and femtosecond (fsec) pulses from modelocked double-clad fiber lasers cladding pumped with broad area diode laser arrays is disclosed. Using an erbium/ytterbium fiber oscillator, 560 fsec pulses with pulse energies up to 40 pJ are generated at a wavelength of 1560 nm. In a dispersion-compensated cavity, pulses as short as 170 fsec with pulse energies up to 50 pJ are obtained. By adding a negatively chirped fiber Bragg grating for additional intracavity dispersion control, pulse widths of 3 psec with pulse energies up to 1 nJ are obtained. A saturable absorber is used for pulse start up, whereas nonlinear polarization evolution is exploited for steady-state pulse shaping. An environmentally stable design is ensured by employing birefringent fibers and a compensation scheme for linear and nonlinear polarization drifts in the cavity.

Abstract: Chirped Bragg gratings are used both for stretching and compressing of ultrashort optical pulses in a chirped pulse amplification system, so that even femtosecond pulses can be stretched and recompressed back to their initial shape and duration. When used in chirped pulse amplification systems instead of bulk diffraction grating stretchers and compressors, Bragg gratings offer unprecedented compactness, robustness and system efficiency.

Abstract: A laser system that enables dual-wavelength asynchronous modelocked operation with controllable repetition rates reduces gain competition and wavelength coupling with either inhomogeneously or homogeneously broadened gain media. Another purpose of the laser system is to minimize pulse interaction effects. The system includes a laser excitation device for generating output wavelengths from the gain medium with non-uniform gain profile. Further, the system includes devices for modelocking and coupling the wavelengths generated by the gain medium. The system includes at least one laser cavity for each of the generated wavelengths.

Abstract: The invention relates to modelocked lasers including highly dispersive optical elements. The dispersive optical elements increase the oscillation pulse width inside the laser oscillators, which reduces the nonlinearity of the laser cavity for a given oscillating pulse energy. Compared to conventionally designed modelocked lasers, an increase in output pulse energy by one to three orders is achieved. As way of example, the technique is applied to an erbium fiber laser, where a chirped fiber Bragg grating is employed as the dispersive element. By using a Kerr-modelocking technique, a high nonlinearity may be sustained inside the fiber laser cavity, which leads to the generation of pulses with psec widths and energies up to 2 nJ. The large bandwidth of the chirped fiber Bragg grating allows a wavelength tuning range in excess of 10 nm, which is achieved by polarization control and a control of the gain spectrum of the laser.

Abstract: The present invention is generally directed to a laser, such as a soliton fiber laser, having an emission wavelength controlled by non-linear effects. Although the emission wavelength of such lasers is typically limited to the center of the gain profile, exemplary embodiments of the present invention provide relatively broad bandwidth control by producing significant gain-pulling using non-linear effects. Any non-linear effects in a laser cavity can be used to provide significant gain pulling and a broadband wavelength tuning range including, for example, the soliton self-frequency shift (SSFS) and cross-phase modulation (CPM). As a result, non-linear tuning can be achieved. Exemplary embodiments provide gain-pulling which allows a significant separation to be induced between the peak emission wavelength of the modelocked fiber laser (i.e., the modelocked emission wavelength, or MLEW) and the emission wavelength of the non-modelocked laser (i.e., the continuous wave emission wavelength, or CWEW).

Abstract: The present invention is directed to providing a passively mode-locked laser which can achieve higher-harmonic mode-locking to produce a pulse repetition rate comparable to that of known actively mode-locked lasers, without requiring the complex modulation schemes typically associated with active techniques. Exemplary embodiments of the present invention are directed to a passively mode-locked laser wherein mode-locking is achieved by harmonic partitioning of the laser cavity. In accordance with the present invention, relatively high repetition rates can be achieved to provide ultra-short pulses without requiring the complex modulation schemes of active techniques, and without becoming susceptible to instabilities typically associated with passive techniques wherein high repetition rates are achieved using subcavities.