Intracavity Dispersion Management Research Articles

Tunable femtosecond optical parametric oscillators resonating at 0.65-1.02 µm and 1.07-2.3 µm.

We present a singly resonant femtosecond optical parametric oscillator (OPO) cavity architecture supporting ultra-broadband wavelength tuning and efficient outcoupling of the generated optical pulses. Experimentally, we demonstrate an OPO with its oscillating wavelength tuned over 652-1017 nm and 1075-2289 nm, spanning nearly 1.8 octaves. This is, as far as we know, the widest resonant-wave tuning range obtained from a green-pumped OPO. We show that intracavity dispersion management is crucial for the stationary and single-band operation of such a broadband wavelength tuning system. This architecture is universal, and therefore can be extended to allow the oscillation and ultra-broadband tuning of OPOs at various spectral regions.

Environment-stable sub-100 fs Er: fiber laser with a 3 dB bandwidth of 78 nm.

A robust all polarization-maintaining (PM) passively mode-locked Er-doped fiber laser is demonstrated based on the biased nonlinear amplifier loop mirror (NALM). With a π/2 nonreciprocal free-space phase shifter, stable single pulse mode locking can be obtained at the central wavelength of 1565.7 nm with a 3 dB spectral bandwidth of 24.6 nm in the soliton regime. The repetition rate of the pulse train is 98.13 MHz. The direct output pulse duration is 109 fs, which is nearly transform-limited. After the intracavity dispersion management, the robust self-started mode-locking in the stretched-pulse regime is realized at 1564 nm, and the 3 dB spectral bandwidth reaches up to 78 nm. The repetition rate of the pulse train is 199.6 MHz. In particular, the direct output pulse width is only 77 fs with a low integrated relative intensity noise (RIN) of only 0.0044% (integrated from 1 Hz to 1 MHz). To the best of our knowledge, this is the shortest pulse width directly from the all-PM NALM laser oscillator.

Nonlinear photonics device based on double perovskite oxide Ba2LaTaO6 for ultrafast laser generation

Using the optical induced deposition, we investigate a saturable absorber (SA) based on tapered fiber and double perovskite oxide Ba2LaTaO6 for ultrashort pulse fiber laser generation. The Ba2LaTaO6 is synthesized via a high-temperature solid-state reaction method. The nonlinear optical absorption of the SA is investigated experimentally. Its saturation intensity and modulation depth are 2.66 MW/cm2 and 24 %, respectively. Depend on intracavity chromatic dispersion management and evanescent field interaction between SA and continuous wave laser, a conventional soliton pulse, a harmonic mode-locking and a three order soliton molecule are also achieved in passively mode-locked fiber laser. This is the first time that double perovskite oxide Ba2LaTaO6 is applied as a saturable absorber to generate an ultrashort pulse fiber laser with abnormal dispersion regimes. The results prove great potentials of Ba2LaTaO6 for future research and applications in ultrafast photonics.

Yb-doped polarization-maintaining femtosecond fiber laser using Gires–Tournois interferometers for dispersion management

We demonstrate an ultrashort pulsed Yb-doped polarization-maintaining fiber laser which uses Gires–Tournois interferometers (GTI) for managing dispersion. The GTI placed in the oscillator cavity aims to compress the pulse. Resulting in a pulse with a duration of 78 fs. The fact that the laser does not require additional de-chirp makes it more compact and avoids the insertion loss of additional components. Experiments with different dispersion confirm the excellent dispersion-managed performance of GTI. As far as we know, the duration of 78 fs is the shortest pulse obtained by using intracavity GTI dispersion management in fiber lasers.

Tunable synchronized dual-wavelength pulsed operation in an Er/Yb double-clad fiber laser

We present a simple and efficient experimental approach to synchronized dual-wavelength pulsed operation in an all-fiber laser. Four different dual-wavelength emissions of synchronized picosecond pulses are generated through simple adjustments of a wave retarder. Autocorrelation traces exhibit modulation profiles corresponding to dual-wavelength emissions with wavelength separations ranging over one order of magnitude, from 0.96 to 9 nm. In all cases, it is observed stable dual-wavelength operation and perfect synchronization between both pulsed components, without requiring of intra-cavity dispersion management. For the first time, to the best of our knowledge, synchronous tunable dual-wavelength pulse emission in a single-cavity Er/Yb double clad ring fiber laser is experimentally demonstrated.

Dispersion managed thulium-doped fiber laser mode-locked by the nonlinear loop mirror

Intracavity dispersion management in a passively mode-locked thulium-doped all-fiber laser, based on a nonlinear optical loop mirror (NOLM) saturable absorber is reported. Fundamental soliton and stretched pulse soliton generation are demonstrated, when the oscillator operates with anomalous net dispersion. Gaussian pulses with a duration of 253 fs and 26.4 nm spectral bandwidth centered at wavelength of 1967 nm were generated with a fundamental pulse repetition frequency of ~15.8 MHz. In soliton mode-locking regime the oscillator delivering optical solitons with a 3 dB spectral width of 7.96 nm and duration of 675 fs. To the best of our knowledge, this is the shortest fundamental soliton generated from thulium-doped fiber laser with all anomalous dispersion based on a nonlinear fiber loop mirror saturable absorber reported till date.

All-solid-state VUV frequency comb at 160 nm using high-harmonic generation in nonlinear femtosecond enhancement cavity.

We realized a solid-state-based vacuum ultraviolet frequency comb by harmonics generation in an external enhancement cavity. Optical conversions were so far reported by only using gaseous media. We present a theory that allows the most suited solid generation medium to be selected for specific target harmonics by adapting the material's bandgap. We experimentally use a thin AlN film grown on a sapphire substrate to realize a compact frequency comb high-harmonic source in the Deep Ultraviolet (DUV) / Vacuum Ultraviolet (VUV) spectral range. By extending our earlier VUV source [Opt. Express26, 21900 (2018)] with the enhancement cavity, a sub-Watt level Ti:sapphire femtosecond frequency comb is enhanced to 24 W stored average power, its 3rd, 5th, and 7th harmonics are generated, and the targeted 5th harmonic's power at 160 nm increased by two orders of magnitude. The emerging nonlinear effects in the solid medium, together with suitable intra-cavity dispersion management, support optimal enhancement and stable locking. To demonstrate the realized frequency comb's spectroscopic ability, we report on the beat measurement between the 3rd harmonic beam and a 266 nm CW laser reaching about 1 MHz accuracy.

Passive optimization of pump noise transfer function by narrow band-pass filtering in femtosecond fiber lasers

Fluctuation of pump power is one of the major sources of temporal and intensity noise in femtosecond fiber lasers. In this work, the transfer functions between the relative intensity noise (RIN) of the pump laser diode (LD) and the output RIN, between the RIN of the pump LD and timing jitter of femtosecond fiber lasers are systematically studied. It is demonstrated, for the first time to our knowledge, that the amplitude of the pump RIN transfer function can be effectively decreased by an intra-cavity narrow band-pass filter. In particular, for normal-dispersion lasers, the 3-dB bandwidth of the transfer function can also be narrowed by two-thirds, with a steeper falling edge. Furthermore, with the narrow band-pass filtering, the transfer function is almost independent of the net intra-cavity dispersion due to amplifier similariton formation. The proposed scheme can effectively isolate the pump-induced noise without the need of complex active pump LD control and intra-cavity dispersion management, thus providing an easy way for practical high-power, high-stability femtosecond fiber laser design and related high-precision applications outside the laboratory.

Asymptotically Single-Mode Hybrid Fiber for Dispersion Management Near 1 μm

In this paper, we demonstrated the possibility of efficient dispersion management using a newly developed asymptotically single-mode hybrid fiber that has anomalous dispersion in the 1 μm spectral range. Of the few internal modes of the hybrid fiber, only one mode can propagate at a length longer than 6 m because of the mode's differential optical absorption. This feature was achieved by inserting a highly absorbing ring layer at the position of the electric field minimum of the hybrid mode. About 10 m of an asymptotically single-mode hybrid fiber with an anomalous dispersion of ∼65 ps/(nm⋅km) at 1064 nm was used for the compression of 7 ps chirped pulses down to 440 fs duration. The use of the same hybrid fiber with a length of 6.5 m for intracavity dispersion management allowed us to demonstrate the stable operation of a ring soliton laser scheme based on a semiconductor satiable absorbing mirror. Pulses with duration of approximately 700 fs, a peak power of 850 W and energy as high as 0.55 nJ were extracted directly from the laser.

Generation of 70 fs broadband pulses in a hybrid nonlinear amplification system with mode-locked Yb:YAG ceramic oscillator

We demonstrate the passively mode-locked laser performances of bulk Yb:YAG ceramic prepared by non-aqueous tape casting, which generates initial pulses in temporal width of 3 ps and spectrum width of 3 nm without intra-cavity dispersion management. The ceramic laser is further used as seeding oscillator in a fiber nonlinear amplification system, where ultrashort pulses in maximum output power of ∼100 W and pulse duration of 70 fs are achieved. Moreover, the laser spectrum is broadened to be ∼41 nm due to self-phase modulation effects in the gain fiber, overcoming the narrow spectrum limitations of ceramic materials. Our approach opens a new avenue for power-scaling and spectrum-expanding of femtosecond ceramic lasers.

Stable Mode-Locked Nanosecond Chirp-Free Pulse Generation With Ultra-Narrow Bandwidth

A stable nanosecond chirp-free pulse generation with ultra-narrow bandwidth is established from a passively mode-locked erbium-doped fiber laser with a homemade fiber Bragg grating as the intra-cavity filter and careful intra-cavity dispersion management introduced. The laser generates nearly chirp-free pulse that is close to the Fourier transform-limited condition. The measured pulsewidth is 2 ns and the spectral width is only 192 MHz. The measured time jitter is below 1%. The pulse repetition rate is 982 kHz, which reveals there are only 195 oscillating longitudinal modes. This is the longest duration of single stable chirp-free pulse in passively continuous-wave mode-locked fiber lasers to our best knowledge.

Operational characteristics of a LD-pumped novel Yb,Y:CaF2 mode-locked laser using a SESAM

A LD-pumped novel Yb,Y:CaF2 femtosecond laser is demonstrated for the first time. The continuous-wave and mode-locked operational characteristics of the co-doped fluoride crystal are described in detail. With intracavity dispersion management using a prism-pair, a 330 fs pulse at a centre wavelength of 1049 nm is obtained. The average output power is 224 mW at a repetition rate of ~83 MHz.

SESAM and SWCNT Mode-Locked All-Fiber Thulium-Doped Lasers Based on the Nonlinear Amplifying Loop Mirror

We report on thulium-doped all-fiber lasers based on the nonlinear amplifying loop mirror and mode-locked with a semiconductor saturable absorber (SESAM) or single-walled carbon nanotubes (SWCNTs). An intracavity and external dispersion management was realized with the aid of a passive germanium-silicate fiber. The SESAM mode-locked laser generates as short as 230-fs pulses with a maximum average output power of 106 mW, corresponding to a 3.7 kW peak power and almost 2 nJ pulse energy. In contrast to the SESAM-based laser, the SWCNT mode-locked laser generates 450-fs pulses of mW-level average output power.

High peak power pulses from dispersion optimised modelocked semiconductor laser

Presented is an electrically pumped passively modelocked edge-emitting semiconductor laser system in an external cavity setup with intracavity dispersion management. This concept, in combination with a pulse compressor, provides pulses as short as 158 fs. By expanding the setup with a tapered diode laser amplifier, peak powers up to 6.5 kW were achieved in the 850 nm wavelength range.

A high power MOPA-laser based on a mode-locked thulium-doped fiber oscillator with intracavity dispersion management

We present a mode-locked thulium-doped fiber laser with intracavity group velocity dispersion (GVD) management by incorporating a low-loss single-mode germanium–silica fiber that introduces a significant amount of normal dispersion. Depending on the total GVD value, the laser generates picosecond or femtosecond pulses in the spectral band between 1930 and 1970 nm. Moreover, we demonstrate an amplifier based on an ytterbium and thulium co-doped GTWave-fiber that also acts as an external pulse compressor. We have obtained amplified pulses with durations from several picoseconds down to 200 fs and energy up to 56 nJ.

Control over the performance characteristics of a passively mode-locked erbium-doped fibre ring laser

We report an all-fibre ultrashort pulse erbium-doped ring laser passively mode-locked by single-wall carbon nanotubes dispersed in carboxymethylcellulose-based polymer films. Owing to intracavity dispersion management and controlled absorption in the polymer films, the laser is capable of generating both femto- and picosecond pulses of various shapes in the spectral range . We have demonstrated and investigated the generation of almost transform-limited, inversely modified solitons at a high normal cavity dispersion.

Ultrafast, stretched-pulse thulium-doped fiber laser with a fiber-based dispersion management

An ultrafast thulium-doped fiber laser with stretched-pulse operation has been realized and investigated. The passively mode-locked oscillator emitted 119 fs pulses at a peak wavelength of 1912 nm. A normal-dispersion fiber with a high numerical aperture and small core was used for intracavity dispersion management and external compression. Numerical simulations were performed and are in good agreement with the experimental results.

High-power thulium-doped fibre laser with intracavity dispersion management

This paper reports a scheme for the generation and amplification of pico- and femtosecond pulses in the range 1.93–1.97 μm using thulium-doped silica fibres. Group velocity dispersion (GVD) management in the cavity of the thulium-doped fibre laser oscillator is ensured by a single-mode germanosilicate fibre (75 mol % GeO2 in the core) with a positive GVD. Pulses are obtained down to 200 fs in duration and up to 56 nJ in energy.

Femtosecond passively modelocked diode laser with intracavity dispersion management

We report on the generation of ultrashort pulses by dispersion management of a passively modelocked external cavity diode laser. Pulse widths down to 200 fs are obtained at 830 nm emission wavelength. We use intracavity dispersion management to increase the spectral bandwidth and compress the strongly chirped pulses externally with a grating compressor.

All-fiber mode-locked nanosecond laser employing intracavity chirped fiber gratings

We demonstrate that nanosecond pulses are generated directly from an all-fiber mode-locked ytterbium-doped fiber laser. A pair of Chirped Fiber Gratings (CFGs) with different sign of dispersion is employed for intracavity dispersion management. Self-starting stabilized mode-locking operation is achieved by nonlinear polarization evolution (NPE). The 1.27 ns pulses are obtained after one CFG with large positive dispersion. The pulse energy is up to 15 nJ at a repetition rate of 3.48 MHz.