Fiber optical parametric generation of widely tunable source : continuous-wave to sub-pricosecond regime

Fiber optical parametric amplifiers (FOPAs) have attracted considerable attention during the last decade because of their broad bandwidth, high gain and wavelength-flexibility. In comparison to cumbersome bulky systems, they bring the advantages of all-fiber systems, i.e. reliability, long-term stability and compactness. FOPAs rely on the third-order susceptibility and are characterized by a quasi-instantaneous nonlinear response that involves pump, signal and idler waves. Chirped pulse amplification (CPA) allows to get a high energy amplification and its realization in FOPAs would increase the overall performances of these amplifiers. Such an experimental demonstration has never been reported in the past. In this work, we show for the first time the experimental feasibility of fiber-based optical parametric chirped pulse amplification (FOPCPA) with an all-fibered setup. The stretching/compression stages are realized with a single linearly chirped fiber Bragg grating (LCFBG) used in both directions while the amplification is performed in a CW-pumped FOPA that uses 500 meters of highly nonlinear fiber (HNLF). Fourier transform limited optical pulses at 1550 nm are stretched from 6 ps to 70 ps and then amplified by 22 dB without any spectral or temporal distortions. Experiments are confirmed by simulations carried out by numerical integration of the nonlinear Schrödinger equation with parameters matching those of the experimental setup. For simplicity, this first experimental demonstration is realized in the telecommunication window. By using photonic crystal fibers, one can move the working wavelength around 1 μm.

We demonstrate with realistic numerical simulations that fiber optical parametric chirped pulse amplification is able to amplify ultra-short optical pulses. Such amplifiers driven by two-pump waves can amplify pulse bandwidth twice as large as the one of a single pump configuration. We show that pulses as short as 50 fs can be directly amplified. In addition, we take benefit from the saturation regime to achieve spectral broadening which makes possible to reduce pulse duration down to 15 fs.

We report an actively mode-locked fiber optical parametric oscillator (FOPO) based on feedback idler which is reflected by a fiber Bragg grating (FBG). The idler-resonant FOPO, configured in ring cavity, is based on high nonlinear fiber (HNLF) and the feedback idler which is modulated by a phase modulator (PM) is poured into the ring cavity via a 3-dB coupler pumped by a continuous wave (CW). With the PM activated and the cavity length synchronized, a stable train of 50 ps pulses can be obtained at a repetition rate of 10 GHz.

We experimentally demonstrate, for the first time to the best of our knowledge, the use of optical fiber for optical parametric chirped pulse amplification to amplify subpicosecond pulses. We use this system to amplify a subpicosecond signal at 1595 nm generated by a fiber-optical parametric oscillator. The 750-fs signal from the oscillator output is stretched to 40 ps, amplified by an all-fiber optical parametric amplifier and then compressed to 808 fs. The peak power of the signal is amplified from 93 mW to 10 W.

Fiber Optical Parametric Chirped Pulse Amplification (FOPCPA) consists of amplifying temporally stretched short pulses in an optical fiber by a high intensity pump beam through a four-wave mixing process [1,2]. Such amplification scheme presents high gain, large bandwidth, repetition rate and wavelength broad flexibility and tunability but provides up to now only very weak signal energies (below the nJ level).

This thesis examines laser generation from the ultraviolet to the short edge of the mid-infrared band by exploiting the nonlinear effects in photonic crystal fibers (PCFs). Several different physical mechanisms are investigated by using homemade PCFs with elaborately customized dispersion profiles. A particular focus is on the development of fiber optical parametric amplifiers (FOPAs) and oscillators (FOPOs) based on the PCFs with a zero-dispersion wavelength of ca. 1.06 m. In particular, several schemes are proposed for solving the key problems involved in the application of FOPOs. These oscillators can be made more convenient to use by optimizing the wavelength-tuning mechanisms, and made more energy-efficient with the help of specially designed cavity structures. Today s oscillators are more reliable, powerful and maneuverable than ever. This thesis provides a systematic road map in connection with the study of nonlinear wavelength generation in PCFs, from their fiber design and technical fabrication, to their physical mechanism and experimental investigation

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.

In contrast to fiber optical parametric amplification, theoretical studies on the dynamics of fiber optical parametric oscillation are rare. In this letter, we propose a precise nonlinear model to predict the saturation gain and the output power of a fiber optical parametric oscillator (FOPO) in the steady state. This model utilizes the sinusoidal-input describing function as a quasi-linear approximation of the nonlinear dynamics of parametric amplification. To complete the nonlinear model of a FOPO, a model for the linear part of the FOPO cavity is established, and then the block diagram of a FOPO is derived. Based on this block diagram and the related transfer function, a graphical approach to attain the saturation gain and output power is introduced. In addition, a simplified graphical approach and a theoretical upper bound for the output power are investigated. Finally, the proposed model is experimentally verified, in which the theory is in agreement with the experiment.

This book, published in 2007, provides comprehensive coverage of the theory and practice of OPAs and related devices, including fiber optical parametric oscillators (OPOs). After introducing the field, the theory and techniques behind all types of fiber OPAs are covered starting from first principles - topics include the scalar and vector OPA theory; the nonlinear Schrodinger equation; OPO theory; and quantum noise figure of fiber OPAs. Challenges of making fiber OPAs practical for a number of applications are discussed, and a survey of the state-of-the-art in feasibility demonstrations and performance evaluations is provided. The capabilities and limitations of OPAs; the potential applications for OPAs and OPOs, and prospects for future developments in the field are discussed. Theoretical tools developed in this text can also be applied to other areas of nonlinear optics. This is a valuable resource for researchers, advanced practitioners, and graduate students in optoelectronics.

Combining Al-doped and Ge-doped HNLFs as gain media in FOPAs is proposed and optimized, resulting in efficient SBS mitigation while circumventing the additional loss of the high SBS threshold Al-doped fiber.

This paper theoretically studies the double-pumped fibre-optical parametric amplifiers (FOPAs) in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the central wavelength of the two pumps. Extremely broad tuning range can be obtained when the central pump wavelength is in the normal dispersion regime and is insensitive to the wavelength separation between the two pumps, while the tuning range is narrow in the anomalous dispersion regime and can be significantly enhanced by increasing the wavelength separation. Impacts of higher-order dispersions and temporal walk-off on the gain spectra are also discussed.

The phase-sensitive amplification (PSA) has attracted intensive attention due to its ability to amplify the in-phase component and attenuate the out-of-phase component of an optical signal. This ability leads to several applications in the all-optical signal processing and fiber optic communication, such as the low-noise amplification, the phase regeneration, and so on. The phase-sensitive functionality can be performed with different nonlinear devices, including the high-nonlinear fiber (HNLF), the periodically poled lithium niobate, the semiconductor optical amplifier (SOA), and so on. Most reported schemes are based on the HNLF, while SOA-based PSA research works are rarely reported. In this paper, the characteristics of dual-pump degenerate PSA in the SOA are theoretically analyzed and experimentally investigated. The input power, injection current, and internal loss of the SOA correlated to the PSA are examined. The influence of the involved wavelengths is also considered. Experimental results show good agreement with the numerical calculations. A gain extinction ratio of ∼25 dB is experimentally obtained, providing the absolute possibility of the on-chip all-optical signal processing based on PSA in the optic communication system.

We present CEP measurements for a 100 kHz optical parametric chirped pulse amplification source in the mid-IR at 3.2 microns. The source is passively CEP stabilised to <100 mrad RMS over 1 million pulses .

Abstract: Fiber Optic Communication system is a key element in modern day telecommunication network used all around the globe. Larger bandwidth signal transmission where data received with lowest possible delay serves as a big edge to both, the telecommunication industry and consumer. Recently, optical fiber communication technology has made great progress, where constantly exploring new technologies has greatly enhanced communications capabilities in the traditional sense. This paper gives an overview of fiber optic communication systems including their key technologies, and also discusses their technological trend towards the next generation. The recent developments in the area of fiber optic communication as well as the advances in different Fiber types, their properties, optical sources, detectors, system limitations and applications are also discussed in the paper.

Highly stable and small size local oscillators is a very important component of any remote sensing, imaging, and telecommunication systems. The key factor influencing the frequency stability is quality factor of the resonance structure. Related close-in to carrier phase noise for offset frequencies above active device corner frequency reduces at least at a rate of 20 dB/decade while offset below corner frequency increases at rate of 30 dB/decade. A new approach in realization of the electrical oscillators is to augment electrical quality factor by optical energy storage components (e.g., fiber optic delay lines and ring resonators) to enhance effective quality factor (Q) to 10^4-10^6, well beyond available electrical Q of 2000 in dielectric resonator oscillators (DRO). Moreover, stability of resonance frequency has been impacted by the environmental induced (e.g., piezo and pyro properties of material) sensitivities. In addition, micro-scale design approaches are reported using multi-mode (both semiconductor and solid state) lasers for low phase noise intermodal oscillations. Finally, forced oscillation techniques of injection locking, phase locking, and mode-locking are attractive to further stabilize electrical and optical oscillation methods. In this thesis, development of broadband stable frequency sources is reported covering both X- and K-band using forced opto-electronic oscillator technique. The broadband frequency tuning is achieved using coarse electrical tuning of YIG bandpass filter combined with fine-tuned optical transversal filter using dispersive delay component and wavelength control of a fiber laser, as optical source. Forced opto-electronic oscillation techniques of self-injection locking (SIL), self-phase locked loop (SPLL), and self-injection locked phase locked loop (SILPLL) are optimized for further frequency stabilization of a frequency synthesizer. In SILPLL application, long delay line is crucial for substantial phase noise reduction; therefore, kilometer long optical fiber delay lines have been used to construct the optical feedback since their loss is extremely low compared to electrical delay lines. Meantime, open loop gain is another key parameter to achieve low phase noise in these feedback systems, as the phase noise reduction is proportional to phase locking loop gain. The phase noise and pull-in time can be greatly reduced in SILPLL as opposed to SIL or SPLL alone. A forced oscillation of fixed frequency DRO at 10 GHz system provide -137 dBc/Hz phase noise at 10kHz offset with under 10 fs aperture jitters, while OEO based X-band and K-band synthesizers provide phase noise of -137 dBc/Hz (&lt;10 fs jitters) and -127 dBc/Hz (&lt;12 fs jitters) at offset 10 kHz respectively in a computer controlled 19" rack-mountable OEO systems. After realization of the desired modular frequency synthesizer, development a compact opto-electronic oscillator system is demonstrated in my PhD study. Monolithic design and testing of multi-section quantum well lasers are reported on 5x2 mm2 InP chip using a commercial foundry service (i.e., SmartPhotonics). The designed lasers consist of 4 major sections of semiconductor optical amplifier (SOA), optical phase modulator (PM) and distributed Bragg reflector (DBR) mirrors. The DBR section provides wavelength selectivity while phase section and gain medium provide output wavelength tuning. An electro-absorption modulator (EAM) is prepared for mode number control using its wavelength sensitive absorption coefficient. The experiments supported predicted performance of this multi-mode laser structure and impact of combined forced oscillation of intermodal oscillations with mode locking method to realize a frequency stabilized and tunable RF signal source. Meantime, forced technique SILPLL and optimum mode locking techniques are applied in order to achieve improved phase noise performance. The free-running inter-modal oscillation frequencies suffers from poor phase noise of -5 dBc/Hz at 1 kHz and -32 dBc/Hz at 10kHz offset around 11.54 GHz, while under forced oscillation a -58 dBc/Hz at 1 kHz offset and -98 dBc/Hz at 10 kHz offset are achieved. A frequency tuning range of 800 MHz is also measured. In mode locked laser operation, the RF beat-notes forced with SILPLL topology provides a better performance. Improved phase noise of -79 dBc/Hz at 1kHz, -110 dBc/Hz at 10 kHz is measured with under 50 fs aperture jitters, while a broadband frequency tuning from 11 GHz to 13 GHz range is measured. The tuning range is potentially to be further improved, if the shared DBR laser pair symmetry could be improved. In summary, this thesis provides the solution for building RF synthesizer using forced opto-electronic oscillator and laser beat-notes oscillation output. The experimental results are corroborated with detailed analytical and numerical modeling to optimize oscillator phase noise performance. The modular design solution shows great stability and low phase noise, while the compact monolithic design solutions are quite attractive for a smaller size. Potential for full integration of multi-mode multi-section MQW laser with optical delay lines are also presented as a logical development path towards a compact frequency synthesizer.