Yujun Deng

Broadly tunable femtosecond parametric oscillator using a photonic crystal fiber

Pulses as short as 460 fs and a tuning range as wide as 200 nm around 1 microm have been achieved from a photonic-crystal-fiber-based parametric oscillator. The ring cavity with only 65 cm of photonic crystal fiber is synchronously pumped with a tunable passively mode-locked Yb-doped fiber laser. Widely extended tunability is achieved by using the modulation instability gain in normal dispersion as the result of high-order dispersion in the photonic crystal fiber.

Generation of broadband femtosecond visible pulses in dispersion-micromanaged holey fibers

Submillimeter-scale dispersion micromanagement (DMM) is used to generate coherent and stable femtosecond visible pulses in holey fibers as short as 10 mm. The longitudinal variation of the phase-matching conditions for Cerenkov radiation and four-wave mixing explains the results well. We have converted up to 20% of the total input energy to a low-noise solitary wave with a bandwidth up to 50 nm in the range 385-625 nm by using holey fibers with various DMM designs.

Colliding-pulse passive harmonic mode-locking in a femtosecond Yb-doped fiber laser with a semiconductor saturable absorber

We demonstrate a passive harmonic mode-locked femtosecond Yb-doped fiber laser employing a semiconductor saturable absorber in a colliding-pulse configuration. 380-fs pulses at 605 MHz repetition rate with >60 dB supermode suppression is achieved.

Self-starting passive harmonic mode-locked femtosecond Yb 3+ -doped fiber laser at 1030 nm

We demonstrate the first self-starting passively harmonic mode-locked femtosecond Yb/sup 3+/-doped fiber laser with up to 585 MHz scalable repetition rate and >45 dB of supermode suppression. 400 mW average power, /spl sim/240 fs pulses is achieved after amplification. Pulse-to-pulse jitter is characterized by optical cross correlation.

Fiber-laser-based difference frequency generation scheme for carrier-envelope-offset phase stabilization applications.

A difference frequency generation scheme that is potentially applicable to self-stabilization of the carrier-envelope-offset phase is demonstrated for the first time with a fiber-laser-based system. By taking advantage of the unique dispersion of the photonic-crystal-fibers, short pulses at 615 nm can be efficiently and selectively generated with low noise via Cherenkov-radiation in a 23-mm-PCF with a mode-locked Yb-fiber laser. Difference frequency generation between the 615-nm pulses and the 1030-nm output pulses from the Yb-fiber amplifier produces pulses at ~1530 nm, which can be readily amplified by Er-doped-fiber amplifiers. This scheme may provide a new route to a fiber-laser-based CEO-phasestabilized source.

Colliding-pulse passive harmonic mode-locking in femtosecond Yb-doped fiber laser with semiconductor saturable absorber

We demonstrate a passive harmonic mode-locked femtosecond Yb-doped fiber laser employing a semiconductor saturable absorber in a colliding-pulse configuration. 380-fs pulses at 605 MHz repetition rate with >55 dB supermode suppression is achieved.

Three-dimensional femtosecond photochemical etching in silicon

Micron-size channels have been made inside silicon by femtosecond laser-assisted HF etching. The etching is guided by localized carriers generated via two-photon absorption. Its potential of 3-D drilling has been demonstrated.

Photonic crystal fiber-based broadly tunable femtosecond laser sources and applications

Photonic crystal fiber (PCF) is considered as a special type of 2-dimensional photonic crystal structure. As the result of its large design flexibility, there are numerous different types of PCFs exhibiting vastly different optical properties. Among them, the small-core PCFs have extremely high effective nonlinearity, which makes them an ideal nonlinear medium for new frequency generation. However significant nonlinear process in fiber only occurs when the phase matching condition is satisfied. Therefore, the dispersion properties of PCFs are also critical. In this paperr, three different approaches are taken to extend the tunability of an Yb-fiber-based femtosecond source. All of the schemes are enabled by the unique dispersion and nonlinear properties of photonic-crystal-fibers (PCFs). In the first approach, by adopting the newly available PCF into an optical parametric oscillator (FOPO) and combining it with our newly-developed mode-locked Yb-fiber laser [1], we extend the tunability of this fiber-based system to over 200-nm around 1 μm [2]. The second scheme uses Raman soliton self-frequency shifting effect in PCFs. Femtosecond soliton pulses tunable from 1100 nm to 1300 nm are generated. In the third approach, by taking advantage of broadly variable phase matching point for the Cherenkov radiation in PCFs, broadly tunable femtosecond visible pulses from 450 nm to 630 nm are achieved [3].

Dispersion micro-managed holey fiber and coherent blue-violet continuum generation

Sub-mm scale dispersion micro-management is introduced and demonstrated to generate coherent blue-violet continuum in a short holey fiber. The longitudinal variations of phase-matching conditions of Cherenkov radiation and four-wave mixing are the reasons.

Photonic-crystal-fiber-based femtosecond parametric oscillator with 200 nm tunability around 1/spl mu/m

Pulses as short as /spl sim/460 fs, tuning range as wide as /spl sim/200 nm around 1/spl mu/m have been achieved from a photonic-crystal-fiber-based parametric oscillator by using the modulation instability gain in normal dispersion regime.