Fiber Optical Parametric Oscillator Research Articles

Widely tunable fiber optical parametric oscillator synchronized with a Ti:sapphire laser for stimulated Raman scattering microscopy

Stimulated Raman scattering (SRS) microscopy is a powerful vibrational imaging technique with high chemical specificity. However, the insufficient tuning range or speed of light sources limits the spectral range of SRS imaging and, hence, the ability to identify molecular species. Here, we present a widely tunable fiber optical parametric oscillator with a tuning range of 1470 cm−1, which can be synchronized with a Ti:sapphire laser. By using the synchronized light sources, we develop an SRS imaging system that covers the fingerprint and C–H stretching regions, without balanced detection. We validate its broadband imaging capability by visualizing a mixed polymer sample in multiple vibrational modes. We also demonstrate SRS imaging of HeLa cells, showing the applicability of our SRS microscope to biological samples.

Numerical Study of the Scheme of a Fiber Optical Parametric Oscillator with Two-Arm Synchronous Pumping

Numerical Study of the Scheme of a Fiber Optical Parametric Oscillator with Two-Arm Synchronous Pumping

µJ-level normal dispersion fiber optical parametric chirped-pulse oscillator based on a collapsed-ends photonic crystal fiber

We demonstrate the generation of broadband tunable and synchronized pulses exceeding the microjoule level using the new concept of fiber optical parametric chirped-pulse oscillation (FOPCPO). The oscillator is based on a collapsed-ends photonic crystal fiber pumped in the normal dispersion regime by a fiber laser.

Fiber Optical Parametric Oscillator With Wide Tuning Range and Fixed Repetition Rate

We present a widely wavelength-tunable fiber-based optical parametric oscillator (FOPO) with a fixed repetition rate using four-wave mixing in a photonic crystal fiber and an intracavity spectral filter. The FOPO produces nearly transform-limited pulses with a spectral width of 1.1 nm and a pulse duration of 1.0 ps. By changing the wavelength of a pump laser and the passband of the spectral filter, the tuning range between 832 and 922 nm is achieved. Over the entire range, the displacement of a delay stage required to match the cavity round trip time with the period of the pump pulses is as small as 0.8 mm. The present FOPO synchronized with a low-noise picosecond laser will be useful for sensitive and broadband vibrational imaging by stimulated Raman scattering microscopy.

Fiber optical parametric oscillator made of soft glass

Fiber optical parametric oscillators (FOPOs) are compact optical sources of coherent and broadly tunable light compatible with operation in unconventional spectral bands. Highly nonlinear silica fibers have enabled the development of FOPOs in the telecommunication wavelength band, but the strong material absorption of silica glass at wavelengths >2 µm limits its applicability in the mid-infrared (MIR) spectral range. In this work, we overcome this issue and report a FOPO designed entirely out of soft glass fiber. For this purpose, we combine an As2Se3 single-mode fiber coupler, an As2Se3 parametric gain medium, and a low-loss ZBLAN delay fiber to build the first all-fiber laser cavity made of soft glass. Two proof-of-concept FOPOs are presented, one driven by pure parametric gain leading to wavelength-tunable Stokes emission within the range 2.088-2.139 µm, and the other driven by Raman-assisted parametric gain leading to Stokes emission within the range 2.023-2.048 µm. This demonstration is a promising first step toward the development of fully fiberized MIR light sources.

Numerical investigation of the energy limit in a picosecond fiber optic parametric oscillator.

Numerical simulation of a fiber optic parametric oscillator to produce picosecond narrowband pulses for coherent anti-Stokes Raman spectroscopy has been performed by an open source Python-based library using an extremely wide range of parameters, such as the pump pulse duration, parametric frequency shift, spectral bandwidth of the pump, and the parametric pulses. It required an extremely large calculation window, both in time and spectral domains. We managed to speed up the simulation 50 times using a graphic processor unit that allowed us to define the areas of stability for different lengths of standard passive (5-100 m) and photonic crystal (23-100 cm) fibers used in the external linear oscillator cavity. It was shown that highly chirped dissipative solitons at a wavelength about 800 nm can be generated with energy up to 55 nJ, which is limited by the pump depletion and self-phase modulation effects.

Numerical investigation of the fiber optic parametric oscillator scheme with a dual-arm synchronous pumping

Numerical investigation of the fiber optic parametric oscillator scheme with a dual-arm synchronous pumping

Coherent light wave generation in an incoherently pumped fiber optical parametric oscillator

We present a numerical study on the coherent sideband generation from an incoherently pumped fiber optical parametric oscillator (FOPO). We revisit the fiber dispersion condition in a parametric process that fulfills the convection-induced phase-locking mechanism when pumping incoherently. Particularly, there exist analytical solutions for phase-matching frequencies in a convection-induced phase-locking process when using a parametric gain fiber with two zero dispersion wavelengths. With the optical feedback, we manage to circulate and amplify the convection sideband in a singly resonant FOPO. The autocorrelation shows that the coherence of the oscillating convection sideband can be strongly influenced by the cavity feedback fraction.

Spectral correlations in a fiber-optical parametric oscillator

Tailoring wavelength correlations in fiber-optical sources through nonlinear phenomena could drive many quantum optics applications. However, to date, such correlations have not been explored within fiber-optical parametric oscillators (FOPO), which are now widespread wavelength-agile sources. We experimentally investigate the real-time dynamics of a synchronously pumped picosecond FOPO with a combination of statistical tools using time-stretch spectroscopy. The study of wavelength correlations allows us to unveil particular spectrotemporal dynamics and correlation patterns. Specifically, we demonstrate that combining mutual information (MI) analysis and least-squares regression with large ensembles of shot-to-shot spectra allows to efficiently track energy transfers from pump to parametric waves. In addition, we show that tuning the FOPO parameters enables the shaping of spectral correlations to a certain extent.

High-energy normal-dispersion fiber optical parametric chirped-pulse oscillator.

We demonstrate a fiber optical parametric chirped-pulse oscillator (FOPCPO) pumped in the normal-dispersion regime by chirped pulses at 1.036 µm. Highly chirped idler pulses tunable from 1210 nm to 1270 nm with energies higher than 250 nJ are generated from our system, along with signal pulses tunable from 870 nm to 910 nm. Numerical simulations demonstrate that further energy scaling is possible and paves the way for the use of such FOPCPOs for applications requiring high-energy, compact, and low-noise sources, such as in biophotonics or spectroscopy.

Numerical study of passively mode-locked fiber optical parametric oscillators by self time-lensing

The recent development of fiber mode-locked lasers with fiber parametric gain has opened up an intriguing field of ultrafast pulse generation. Thanks to the tunability of the parametric gain in optical fibers, the gain media of mode-locked lasers are no longer limited to the choice of rare-earth-doped fibers. In our previous study, optical time-stretch was introduced into the cavity of a fiber optical parametric oscillator as a temporal diffracting distance to overcome localization of the parametric gain. The implementation of the diffracting distance for pulse stretching and compression relied on two dispersive elements with opposite sign dispersion. In this context, we propose a new design of passively mode-locked fiber optical parametric oscillators with only a single mono-dispersive element. We utilize the parametric process as a time lens at which the spectral components of the two oscillating parametric sidebands are phase-conjugated in the temporal domain. This allows both mode-locked sidebands to oscillate and switch periodically inside the fiber cavity with only a single dispersive element. We numerically simulate the pulse generation of this switching mode-locked fiber parametric oscillator.

Instantaneous Dynamics of a Fiber Optical Parametric Oscillator Within Its Initiating Process

A fiber optical parametric oscillator (FOPO) is an effective way of generating new wavelength lasers in non-conventional wavelength bands, but the complex nature behind it is challenging for both theoretical and experimental studies. Luckily, dispersive Fourier transformation, which has been emerging in recent years, provides us with a good method of demystifying this complexity. In this letter, we capture and report, for the first time, the instantaneous dynamics of the initiating process in a fiber optical parametric oscillator. We directly observe that the initiating process experiences three stages. The FOPO fully establishes the parametric oscillation during nearly 2000 round-trips, i.e., nearly 93 $\mu \text{s}$ . In the meantime, the spectrum of the amplifier spontaneous emission noise gradually narrows down and evolves into the characteristic spectrum of the parametric oscillation. In order to start parametric oscillation, the pump power needs to exceed a certain threshold, after reaching which the power of the residual pump decreases while the signal and idle light grow. As we expect, due to the four-wave mixing effect, the signal and idle light are completely synchronous. Moreover, the stability of the oscillation is very sensitive to a slight fluctuation of the pumping pulses.

Fiber Source for Pumping a Fiber-Optical Parametric Generator at ∼800 nm

The coherent anti-Stokes Raman spectroscopy (CARS) has attracted a great attention as non-invasive method of real-time monitoring of processes occurring in biological tissues and cells. It needs a special kind of optical source that would be compact, stable and low cost. We investigate a possibility of using highly-chirped dissipative soliton oscillator together with a narrowband fiber Bragg grating and all-fiber amplifier. Optical pulses with the duration of 85 ps and the peak power of 400 W were generated at the output of the fiber system with the repetition rate about 13 MHz. Developed source is suitable to pump a fiber optical parametric oscillator for CARS.

Low Noise High-Energy Dissipative Soliton Erbium Fiber Laser for Fiber Optical Parametric Oscillator Pumping

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.

High-energy dissipative soliton-driven fiber optical parametric oscillator emitting at 1.7 µm

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.

Fiber Optical Parametric Oscillator and Amplifier for CARS Spectroscopy

We demonstrated coherent anti-Stokes Raman scattering spectroscopy based on fiber optical parametric oscillator and amplifier utilizing four wave mixing in photonic crystal fibers. The output powers and spectra of generated signals were analyzed in detail for various regimes involving spontaneous, stimulated, and amplified parametric processes. The optical parametric oscillator provided tunable signal pulses from 780 to 787 nm with a spectral bandwidth of 3.0 nm, which were then used to seed a fiber optical parametric amplifier, resulting in signal pulses with an average power of 33 mW and spectral bandwidth of 1.1 nm. Using the amplified signal and residual pump pulses, the anti-Stokes signal of polystyrene sample was detected, which confirms the feasibility of the proposed coherent anti-Stokes Raman Scattering light source.

Short pulse generation from a passively mode-locked fiber optical parametric oscillator with optical time-stretch.

We propose a passively mode-locked fiber optical parametric oscillator assisted with optical time-stretch. Thanks to the lately developed optical time-stretch technique, the onset oscillating spectral components can be temporally dispersed across the pump envelope and further compete for the parametric gain with the other parts of onset oscillating sidebands within the pump envelope. By matching the amount of dispersion in optical time-stretch with the pulse width of the quasi-CW pump and oscillating one of the parametric sidebands inside the fiber cavity, we numerically show that the fiber parametric oscillator can be operated in a single pulse regime. By varying the amount of the intracavity dispersion, we further verify that the origin of this single pulse mode-locking regime is due to the optical pulse stretching and compression.

Tunable Femtosecond Laser From 965 to 1025 nm in Fiber Optical Parametric Oscillator

We presented a fiber optical parametric oscillator generating tunable femtosecond pulses based on four-wave mixing. By using a photonic crystal fiber as the parametric gain and a single mode fiber to select the oscillating wavelength via dispersion filtering, output pulses with a pulse duration of 350 fs, and spectral bandwidth of 5.8 nm were obtained. The wavelength of the output pulses could be tuned from 965 to 1025 nm by adjusting the dispersion filtering. This setup provides a simple and flexible light source for biomedical applications and tunable infrared pulse generation through nonlinear frequency conversion.

Polarization switch of four-wave mixing in a lawtunable fiber optical parametric oscillator.

We reported the simultaneous generation and selective manipulation of scalar and cross-phase modulation instabilities in a fiber optical parametric oscillator. Numerical and experimental results show independent control of parametric gain by changing the input pump polarization state. The resonant cavity enables power enhancement of 45 dB for the spontaneous sidebands, generating laser pulses tunable from 783 to 791 nm and 896 to 1005 nm due to the combination of four-wave mixing, cascaded Raman scattering and other nonlinear effects. This gain controlled, wavelength tunable, fiber-based laser source may find applications in the fields of nonlinear biomedical imaging and stimulated Raman spectroscopy.

All-fiber wavelength-swept optical parametric oscillator at 1 μm band

We demonstrate an all-fiber and continuously wavelength-swept fiber optical parametric oscillator (FOPO) based on dispersion tuning technology around 1 μm. The alignment-free FOPO is pumped by a pulse train light, driven by a frequency-swept electric pulse source with a repetition rate ranging from 107.24 MHz to 107.31 MHz. Thus, the FOPO demonstrates a wavelength-swept output with a sweeping range of 100 nm centered at 1065.10 nm. The sweeping rate can be improved up to 100 kHz, while the cumulative speed exceeds 1000 000 nm s−1. Since the electric scanning is used in an all-fiber setup instead of the traditional mechanical scanning method, it demonstrates better stability under prolonged operation, which is promising to be applied in biomedical imaging, such as optical coherence tomography (OCT) systems and other applications.