We design various tapered photonic crystal fibers (PCFs) , namely, hexagonal tapered PCF (H-TPCF), octagonal tapered PCF (O-TPCF) and decagonal tapered PCF (D-TPCF) for generating self-similar ultrashort pulses (USPs) and stretched pulses . Here, we report on pulse compression as well as pulse stretching using the above mentioned PCFs wherein both dispersion and nonlinear profiles vary exponentially. Of these PCFs, we use dispersion decreasing PCFs for pulse compression process and dispersion increasing PCFs for pulse stretching process. From the detailed analysis, we find that H-TPCFs could generate high quality USPs with more compression percentage whereas D-TPCFs could produce high quality stretched pulses with more stretching percentage.

Senthilnathan K

Department of Physics

School of Advanced Sciences

Vellore Campus

Ramesh Babu P

Manimegalai A

Nakkeeran K

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

A Comparative Study on Designing Efficient Pulse Compressors and Pulse Stretchers Using Tapered Photonic Crystal Fibers

Springer Proceedings in Physics Recent Trends in Materials Science and Applications

The generation of high-quality self-similar ultrashort pulses at 1550 nm by tapering the photonic crystal fibers (PCFs) is numerically demonstrated. We taper the PCF to achieve the exponentially decreasing dispersion and exponentially increasing nonlinearity profiles, which turn out to be the fundamental requirements for generating the chirped self-similar pulses. Further, we find that the chirped solitons could also be generated with the other three possible exponential variations. Thus, for the first time, we attempt tapering the PCFs for bringing in these exponentially varying dispersion and nonlinear profiles. We carry out the detailed pulse compression studies for various decay rates of the dispersion profiles as the decay rates of dispersion depend on the initial chirp and hence on compression factor, too. The unique feature of this pulse compressor lies in the fact that the required length of the tapered PCF is about 20 times less than that of the previously reported pulse compressor operating at 850 nm. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).

Fulltext

Optical Engineering

Tapering photonic crystal fibers for generating self-similar ultrashort pulses at 1550 nm

We consider an optical pulse propagating in a tapered photonic crystal fiber (PCF) wherein dispersion as well as nonlinearity varies along the propagation direction. The generalized nonlinear Schrödinger equation aptly models the pulse propagation in such a PCF. The design of the tapered PCF is based on the analytical results, which demand that the dispersion decrease exponentially and the nonlinearity increase exponentially. In this paper, we adopt the generalized projection operator method for deriving the pulse-parameter equations of the Lagrangian variation method and the collective variable method. Besides, we consider another pulse profile called raised cosine (RC), which is aimed at replacing the conventional hyperbolic secant pulse. From the detailed results, we infer that the initial RC pulse evolves into a hyperbolic secant pulse. Further, in order to minimize the input power requirement, we employ the idea of replacing the solid core in the PCF with chloroform. In addition to the single pulse compression, we also investigate the possibility of multisoliton pulse compression. Here, we consider eight chirped hyperbolic secant pulses as input and generate a train of ultrashort pulses at 850 nm based on the chirped multisoliton pulse compression. In a similar way, we extend this pulse compression with eight RC pulses.

IEEE Photonics Journal

Generation of a Train of Ultrashort Pulses Near-Infrared Regime in a Tapered Photonic Crystal Fiber Using Raised-Cosine Pulses

We propose a fiber stretcher for stretching the high-energy ultrashort pulses which require high dispersion and large mode area to secure high stretching ratio and for ensuring distortionless pulses. In this line, we suggest a novel design of photonic quasi-crystal fiber (PQF) to achieve the desired high normal group velocity dispersion (GVD) of 1000 ps2/km at 1.06 μm and inner core effective mode area as 35 μm2. These unique properties have been exploited to achieve a high stretching ratio (&gt;105) as well as less nonlinearity, which, in turn, results in a distortionless fiber stretcher for an Yb-doped high-energy ultrafast fiber laser system based on chirped pulse amplification. © 2006 IEEE.

IEEE Photonics Technology Letters

High Normal Dispersion and Large Mode Area Photonic Quasi-Crystal Fiber Stretcher

By using appropriate self-similar scaling analysis, we delineate the generation of linearly chirped solitary pulses in photonic crystal fiber (PCF) at 850 nm to obtain the short pulses with large compression factor and minimal pedestal energy when compared to adiabatic compression scheme. The dispersion and nonlinearity varying nonlinear Schrdinger equation aptly models the pulse propagation in such a PCF. The analytical results demand that the effective dispersion must decrease exponentially while the nonlinearity must increase exponentially in the PCF. Thus, based on the analytical results, we propose the new design of tapered PCF by varying the pitch and diameter of the air hole. We adopt the projection operator method to derive the pulse parameter equations which indeed very clearly describe the self-similar pulse compression process at different parts of the PCF structures. As we are interested in constructing compact compressor, we also introduce another designing of PCF by filling chloroform in the core region. The chloroform filled tapered PCF exhibits low dispersion length for efficient pulse compression with low input pulse energy over small propagation distances. © 2010 IEEE.

Journal	Data powered by TypesetSpringer Proceedings in Physics Recent Trends in Materials Science and Applications
Publisher	Data powered by TypesetSpringer International Publishing
ISSN	0930-8989
Open Access	No