We report on a passively mode-locked oscillator based on an erbium-doped dual concentric core fiber combining high normal dispersion and large mode area. This large normal dispersion laser generates long pulses with 30 ps duration and 0.17 nm spectral width at 1530 nm wavelength. The source delivers an average power of 64 mW at a repetition rate of 16 MHz, corresponding to 4 nJ energy. This concept opens up new degrees of freedom in the design of mode-locked fiber lasers.

We report a fiber optical parametric oscillator (FOPO) synchronously pumped in a C-band, delivering high-energy picosecond pulses exceeding the nanojoule level of around 1700 nm. The gain medium is a dispersion-shifted fiber, pumped by highly-chirped pulses from a mode-locked dissipative soliton fiber laser. Optimizing the pump wavelength along with time-dispersion-tuning of the FOPO enabled a broad tunability from 1617-1876 nm for the idler wave. In addition, relative intensity noise levels below -140 dBc Hz(-1) have been achieved, paving the way for using such a source in biophotonics and instrumentation.

We report on a mode-locked erbium-doped fiber laser delivering highly-chirped pulses with several tens of nanojoules of energy around 1560 nm and its exploitation to efficiently pump a fiber optical parametric oscillator (FOPO), thus enabling picosecond pulse generation around 1700 nm. The laser cavity features a high normal dispersion and mode-locking is sustained using tailored spectral filtering combined with nonlinear polarization evolution and a semiconductor saturable absorber. Numerical simulations show that the laser dynamics is governed by a strong mode-locking mechanism compensating for the large spectral and temporal pulse evolution along the cavity. In the frame of high energy picosecond pulse generation around 1700 nm, we then demonstrate that using highly-chirped pulses as pump pulses allows for the efficient tuning of the FOPO idler wavelength between 1620 and 1870 nm. In addition, satisfying noise characteristics have been achieved both for the Er-laser and the FOPO, with respective relative intensity noises (RIN) of −154 and −140 dBc/Hz, thus paving the way for the use of such sources in ultrafast instrumentation.

Ability of fast intensity discrimination provided by a graphene-based saturable absorber device is demonstrated in the perspective of all-optical signal processing in 1.5 mu m wavelength range. The dynamic extinction ratio enhancement is measured as more than 3 dB. It is argued that, the device performances are promising enough to be tested further in an efficient all-optical module to reduce crosstalk or intensity noise in high rate signals.

Ultrafast fiber laser technology is nowadays a mature field with numerous industrial and scientific applications ranging from material processing to microscopy and metrology. As a consequence, the available output power of ultrafast fiber lasers has followed a remarkable growth in the last decade. The technological maturity and commercial availability of semiconductor saturable absorber mirrors (SESAMs) play a key role in this progress as they are essential for ultrashort pulse generation in passively mode-locked lasers [1] and can now cover a broad spectral range. In order to efficiently initiate mode-locking in fiber lasers, such SeSaMs must exhibit very strong nonlinearities and in particular, in the case of dissipative soliton lasers, high modulation depths of several tens of percent are required to stabilize the pulsed regime [2, 3]. Such performances are today reached with multiple quantum wells (MQW) saturable absorbers embedded in resonant Fabry-Perot cavities [4] and with the introduction of impurities in the active area in order to lower the carriers' lifetime. An accurate control of the growth process is however required to obtain satisfying optical properties. Even if simplified technologies have been developed, e.g. based on carbon nanotubes or topological insulators, they cannot be implemented in a large scale with reproducible processes and thus cannot answer the current need for efficient mass-production of SESAMs. Here, we present a novel SESAM architecture with a simplified fabrication process based on Metal Organic Chemical Vapor Deposition (MOCVD), which is cost effective and more adapted for large-scale fabrication than standard molecular beam epitaxy used for growing current commercial saturable absorber devices. This new generation of SESAMs is based on a thick InGaAs layer embedded into a resonant Fabry-Perot micro-cavity, as shown in Fig. 1(a). In order to demonstrate the great potential of our SESAM for ultrafast lasers, we successfully used it to achieve stable mode-locking in a normal dispersion erbium-doped fiber laser without using any additional mechanism such as nonlinear polarisation evolution, hence reducing the laser cavity to a compact and user-friendly configuration (see Fig. 1(a)). Highly-chirped dissipative solitons with 19.5 ps duration and 5.4 nm width were obtained, as shown in Fig. 1(b). Pulses have then been externally compressed down to 1.1 ps and our system showed an excellent amplitude stability with a signal-to-noise ratio exceeding 90 dB. The laser delivers an average power of 86 mW at 17 MHz repetition rate, corresponding to an energy per pulse of 5 nJ. This work suggests that this new generation of SESAM with reduced fabrication costs can be considered as a promising alternative to current technologies in the frame of ultrafast lasers development and apphcations.

We report on the successful operation of a dissipative soliton fiber laser mode-locked with a bulk InGaAs-based saturable absorber mirror forming a resonant micro-cavity. Highly-chirped pulses with several nanojoules of energy are thus produced. Remarkably, the laser performances in terms of output power and amplitude stability are comparable to those obtained with their multiple-quantum-well-based counterparts. This letter suggests that this simplified approach for saturable absorber mirrors can be considered as a promising alternative regarding ultrafast optics applications.

Ultrafast laser sources emitting in the spectral range 1600–1800 nm are very attractive for many biomedical applications such as multi-photon microscopy [1] and laser surgery [2]. Taking into account tissue scattering and absorption, it has indeed been shown that the optimum wavelength window in terms of penetration lies around 1700 nm [3]. The development of fiber-based ultrafast lasers to address these applications is highly desired to offer reliable and cost effective laser solutions. The first approach to achieve this goal consists in developing mode-locked lasers based of Tm-Ho- or Bi-doped fibers and emitting directly around 1700 nm [3-4]. Unfortunately, the performances of these sources are far from target in terms of pulse energy and laser dynamics [3-4]. The second approach relies on nonlinear conversion of a pump pulse centred at 1550 nm through intrapulse stimulated Raman scattering [1] or by exploiting fiber-based optical parametric oscillators (FOPO) [5]. Here, we demonstrate a DSF-based FOPO pumped by a dissipative soliton Er-doped fiber laser [6]. We report, to the best of our knowledge, the highest energy at 1665 nm for a degenerate FWM FOPO pumped by ps pulses. The tuning of the FOPO was performed via the adjustment of the pump wavelength along with the time-dispersion-tuning technique (Fig. 1(a)). Optimizing the pump wavelength along with the FOPO cavity length allowed a broad tunability from 1617 to 1876 nm for the idler and from 1319 to 1518 nm for the signal (Fig. 1 (b)). For a pump wavelength of 1566 nm, 4 ps idler pulses with 3 nJ energy have been obtained at 1665 nm, with a record-high internal conversion efficiency of 55 %. Pulse evolution within the cavity was also numerically investigated using a generalized nonlinear Schrödinger equation (GNLSE) model and an excellent agreement with the experimental results was found. Amplitude noise measurements have been performed on both the pump and idler pulses and a good relative intensity noise (RIN) level lower than −140dBc/Hz have been measured. This work thus paves the way for the use of such a fiberized source in nonlinear imaging experiments such as coherent Raman microscopy and optical coherence tomography.

We aim at realizing an optically-pumped, dual-frequency VECSEL at telecom wavelength (1.5 µm) with a frequency difference in the radio-frequency (RF) range (around 11 GHz), to be used in a sensor unit based on Brillouin scattering in optical fibers. Laser emission of two orthogonally-polarized cavity modes with a controlled frequency difference is obtained by inserting a birefringent crystal in the VECSEL cavity. We have examined the influence of the different intra-cavity elements on the laser emission. It is shown that optimizing the free spectral range and the bandwidth of the intra-cavity Fabry-Perot etalon is of practical importance to achieve a stable single longitudinal laser emission for each of the two orthogonal polarizations. The optimization of the output power has also been investigated and it is concluded that up to 100 mW output power can be expected by adjusting the reflectivity of the output coupling mirror of the VECSEL cavity. The achievement of a highly-stable frequency difference is crucial for sensing applications. For this reason the influence of different parameters on the stability of the dual-frequency emission have been studied. It is concluded that mechanical vibrations are the main cause of the RF signal instability in our free-running VECSEL cavity. The design of a compact or mono-block cavity may allow to meet the stability requirements for our sensors.

We have realized a dual-frequency vertical external cavity surface emitting laser (VECSEL) at 1.5 μm. Laser emission of two orthogonally polarized cavity modes is obtained by inserting a birefringent crystal into the VECSEL cavity. We have examined the influence of the different intracavity elements on the laser emission. It is shown that optimizing the free spectral range and the bandwidth of the intracavity Fabry-Perot etalon is of practical importance to achieve a stable single longitudinal laser emission for each of the two orthogonal polarizations. The optimization of the output power has also been investigated, and it is concluded that up to 50 mW output power can be expected in dual-frequency operation by adjusting the reflectivity of the output coupling mirror of the VECSEL cavity. The influence of different parameters on the stability of the dual-frequency emission has been studied. It is concluded that mechanical vibrations are the main cause of radio-frequency (RF) signal instability in our free-running VECSEL cavity. The design of a compact or mono-block cavity may allow meeting the stability requirements for optical fiber sensors based on Brillouin scattering.

Laser sources with a controllable flexible wavelength have found widespread applications in optical fiber communication, optical sensing, and microscopy. Here, we report a tunable mode-locked fiber laser using a graphene-based saturable absorber and a tapered mirror as an end mirror in the cavity. The phase layer in the mirror is precisely etched by focused ion beam (FIB) milling technology, and the resonant wavelength of the mirror shifts correspond to the different etch depths. By scanning the tapered mirror mechanically, the center wavelength of a mode-locked fiber laser can be continuously tuned from 1562 to 1532 nm, with a pulse width in the sub-ps level and repetition rate of 27 MHz.

We report on a passively mode-locked erbium-doped fiber laser featuring a large normal dispersion and emitting high-energy dissipative solitons. Mode-locking is stabilized by the combined actions of a high nonlinearity amplitude modulator and a narrow band spectral filter. The laser routinely delivers highly chirped pulses with more than 38 nJ energy that can be compressed down to 700 fs duration using bulk gratings. Numerical simulations confirm the experimental results and reveal the self-similar pulse evolution along the normal dispersion fibers included inside the cavity.

Focused ion beam milling has been applied to fabricate an ultra-thin taper structure on crystalline indium phosphide to realize a multi-wavelength vertical cavity photonic device. The appropriate FIB scanning procedures and operating parameters were used to control the target material re-deposition and to minimize the surface roughness of the milled area. The sputtering yield of crystalline indium phosphide target was determined by investigating the relationship between milling depth and ion dose. By applying the optimal experimentally obtained yield and related dose range, we have fabricated an ultra-thin taper structure whose etch depths are precisely and progressively tapered from 25 nm to 55 nm, with a horizontal slope of about 1:13,000. The optical characterization of this tapered device confirms the expected multi-wavelength behavior of our device and shows that the optical losses induced by the FIB milling process are negligible. (C) 2014 Elsevier B.V. All rights reserved.

In this paper, we review our recent developments on ultrafast pulse generation in erbium-doped fiber laser systems operating in the 1550 nm wavelength range. This work concerns the generation of ultrafast pulses from dissipative soliton fiber lasers featuring resonant saturable absorber mirrors, as well as their amplification in highly efficient erbium-doped large-mode-area fibers. Different amplification schemes featuring all-fiber components are studied leading to the achievement of record pulse energy from a high repetition rate laser system.

LBL-12154 C'. Invited paper to be presented to the International Conference on Excited States and Multiresonant Nonlinear Optical Processes in Solids, Aussois, ~ranee, March 18-20, 1981 THEORETICAL ASPECTS OF FOUR-WAVE MIXING SPECTROSCOPY WITH MULTIPLE RESONANCES J.L. Oudar and Y.R. Shen January 1981 TWO-WEEK LOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks. For a personal retention copyy call Tech. Info. Divisiony Ext 6782. Prepared for the U.S. Department of Energy under Contract W-7405-ENG-48

We demonstrate that the nonlinear optical response of graphene is resonantly enhanced by incorporating monolayer graphene into a Fabry-Pérot microcavity. The modulation depth of the microcavity-integrated monolayer graphene device is increased to 12% which is much higher than the value of about 2% in other works, while retaining an ultrafast recovery time of ~0.7 ps. This suggests possible application in ultrafast all-optical signal processing.

We report on our recent developments on ultrafast pulse generation in erbium-doped fiber laser systems operating in the 1550 nm wavelength range. This work concerns the generation of ultrafast pulses from dissipative soliton fiber lasers featuring resonant saturable absorber mirrors as well as their amplification in highly efficient erbium-doped large-mode-area fibers. Different amplification schemes featuring all-fiber components are studied leading to the achievement of record pulse energy from a high repetition rate laser system. The system delivers 8 W of average power at 35 MHz repetition rate corresponding to 230 nJ pulse energy. After external compression, near transform-limited, 850 fs-long pulses are obtained. The pulse peak power exceeds 180 kW.