Matei Rusu

Passively synchronized erbium (1550-nm) and ytterbium (1040-nm) mode-locked fiber lasers sharing a cavity.

Erbium and ytterbium fiber lasers were firmly synchronized by nonlinear interaction in active media placed in the same cavity. A two-color femtosecond-picosecond pulse train at largely separate wavelengths of 1.55 and 1.04 microm was generated. Optimizing the laser cavity to enhance the cross-phase modulation in the gain materials has yielded a large mismatch of 20 microm between the two laser cavities.

Slicing the supercontinuum radiation generated in photonic crystal fiber using an all-fiber chirped-pulse amplification system.

We report on an experimental study of supercontinuum broadening in photonic crystal fiber performed by measuring the temporal behavior of spectrally-sliced radiation in different propagation regimes. The study confirms the soliton fission theory by observing the red-shifted fundamental solitons and blue-shifted nonsolitonic radiation.

Passively synchronized two-color mode-locked fiber system based on master-slave lasers geometry

Using a master - slave configuration, a robust synchronization was achieved for two-color Erbium and Ytterbium mode-locked fiber lasers. Due to enhanced nonlinear interaction in the fiber, noise-free pulse-locking was achieved allowing for a cavity mismatch tolerance of 140 microm. This is the highest tolerable cavity-length difference ever been obtained for synchronized mode-locked oscillators.

Red-green-blue (RGB) light generator using tapered fiber pumped with a frequency-doubled Yb-fiber laser.

We report on successful realization of a picosecond visible-continuum source embedding a single mode fiber taper. The output of ytterbium mode-locked fiber laser was frequency doubled in a periodically-polled lithium niobate (PPLN) crystal to produce green pump light. Spectral brightness of the white light generated in the tapered fiber was improved by limiting the broadening just to the visible wavelengths. The influence of taper parameters, particularly the dispersion, on white light spectrum has been studied.

Femtosecond neodymium-doped fiber laser operating in the 894-909-nm spectral range

We demonstrate a practical ultrafast Nd-doped fiber laser operating in the 894-909-nm spectral range. Using purposely designed semiconductor saturable absorbers, a truly self-started mode-locking regime of operation with clean transform-limited 360-fs pulses was achieved.

Fiber taper for dispersion management in a mode-locked ytterbium fiber laser

We exploit the large anomalous dispersion in the waist of a fiber taper to offset the intracavity normal chromatic dispersion of an Yb-doped fiber laser. The fiber taper provides sufficient anomalous dispersion to ensure soliton operation of the mode-locked laser. With the taper removed from the cavity, the laser operates in a net normal dispersion regime.

1.05-μm mode-locked Ytterbium fiber laser stabilized with the pulse train from a 1.54-μm laser diode

Using cross-phase modulation in an optical fiber, we synchronized the pulse train from a mode-locked ytterbium fiber laser operating at 1.05 microm to an external optical master signal. The optical master source based on a 1.54 microm distributed feedback (DFB) diode laser was driven by the clock signal and was used as a seed source. The amplified seed pulses are launched into the fiber cavity and synchronize the mode-locked pulses through cross-phase modulation. The master clock signal is electronically generated, benefiting from inherent stability and repeatability. Due to its simplicity, this technique provides an attractive alternative to the traditional scheme that uses an independent mode-locked laser as source of seed signal. Since the approach is flexible and generally applicable, we expect this stabilization method to have a good potential for use in metrology and optical communications.

Semiconductor all-optical modulator for synchronization of independent fiber laser oscillators and active mode-locking

Using an optically driven nonlinear semiconductor mirror, we have synchronized a 1.56-/spl mu/m mode-locked erbium fiber laser to the pulse train from a mode-locked ytterbium fiber laser operating at 1.05 /spl mu/m. We demonstrate that a robust active or passive mode-locked picosecond pulse operation and tight control of the repetition rate can be obtained resulting in a large value of the locking tolerance for the slave laser cavity mismatch exceeding 250 /spl mu/m.

Flat-top temperature tuning response in periodically-poled nonlinear crystals

Second harmonic generation via periodically-poled nonlinear materials offers an efficient means of generating high-quality visible light at wavelengths that would be otherwise unattainable with traditional laser sources. While this technology has the potential for implementation in many mass-industrial applications, temperature stability requirements, often as restrictive as 0.1°C, can make packaging with a pump source problematic. In this work we are investigating the use of synthesised response PPLN gratings to create crystals that are better suited to visible SHG. Our route towards addressing this issue is to convert the standard sinc-shaped temperature-tuning response of a uniform grating to a flat-top temperature tuning function with widths of up to several degrees. We have achieved a computationally efficient means of designing such gratings with a required temperature tuning profile based on a simulated annealing algorithm using repeated local changes of grating layout and subsequent Bloembergen-style analysis of the second harmonic, successive iterations of which quickly lead to the desired temperature tuning profile. Using our high fidelity poling technique we have fabricated synthesised response PPLN with precise placement of poled domains in Lithium Niobate based on the designs from our mathematical models. Measurements on these initial devices provide more than 4°C flat-top temperature stability, albeit with a corresponding loss in operational efficiency. Our aim is to implement improved designs in magnesium-doped Lithium Niobate for packaging with near-room temperature diode-based pump sources, as could be applied towards RGB TV and projector applications.

Passively mode-locked erbium fiber laser synchronized to clock using vertical-cavity semiconductor modulator driven optically with the 1.54-/spl mu/m laser diode

Robust synchronization of a passively mode-locked fiber laser to an optical clock based on gain-switched semiconductor laser diode has been achieved. Owing to high nonlinear response of vertical-cavity semiconductor reflecting modulator, the locking mechanism is efficient and would allow for reliable synchronization of passively mode-locked laser at high harmonics. The clock is built entirely of standard telecom-grade components